al si order in albite and its effect on albite dissolution processes a monte carlo study the role of al si disorder in the kinetics of albite dissolution is explored through parameterized monte carlo methods two dissolution mechanisms multilayer leaching and single layer retreat were tested on 48 albite test configurations in simulations involving multilayer leaching dissolution rates increased with decreasing long range order lro we observed a fivefold maximum increase in dissolution rate tied to al si disordering roughly equivalent to that accompanying a decrease of 1 4 ph units at ph 1 5 this increase in rate due to disordering in albite is similar to that observed from compositional variation in plagioclase feldspars an47 vs an at low ph in contrast al si disordering had no discernible effect during the simulations involving the single layer retreat mechanism these results suggest that the effect of al si disorder on albite dissolution rate is mechanism dependent

sediment scour and deposition within harbors in california usa caused by the march 11 2011 tohoku oki tsunami abstract tsunamis have caused significant damage to boats and docks within harbors and ports along the california coast sediment scour and deposition within harbors by tsunamis though not extensively studied have produced long term impacts to the recovery and resiliency of affected maritime communities the march 11 2011 tohoku oki teletsunami generated strong tsunami currents up to 7 m s or 14 kn within crescent city and santa cruz harbors that triggered sedimentation problems regulatory issues with sediment disposal and months of delays in the reconstruction process evaluation of video pre and post tsunami bathymetric surveys and harbor sediment analysis data helped develop a better understanding of tsunami flow regime and sediment transport within these harbors in crescent city the scour effects of large tsunami surges were amplified by the narrow entrance to the small boat basin increasing the sediment supply and trapping this material within the basin causing shoaling that made the harbor unusable and creating long term disposal issues within the entire harbor at least 289 400 m3 of sediment was scoured in an area of 0 67 km2 a minimum fill volume of 154 600 m3 was calculated with the sediment covering 55 of that portion of the harbor included in the bathymetric surveys in santa cruz the long constricting layout and shallow nature of the harbor increased current velocities and scour in confined areas and exacerbated sedimentation in between and beneath docks at the harbor entrance estimated scour volumes range from 2550 to 14 800 m3 and fill estimates range from 120 to 8750 m3 depending upon the surveys used to characterize post tsunami conditions while the area of deposition ranges from 6 to 64 of the survey overlap areas about 83 m3 of sediment was scoured in santa cruz north harbor while a minimum of 75 m3 was deposited across 50 of that portion of the harbor common to pre and post tsunami surveys fill estimates are considered minimums due to sediment deposited in locales not covered by the various surveys in general the southern part of the harbor near the entrance jetties was erosional while most of the northern part of the harbor was depositional analyses of tsunami currents observed on videos collected during the tsunami provide excellent support for the bathymetric change analyses and together the two lines of evidence provide a means to predict flow patterns and areas at risk of damage from the tsunami by assessing harbor dimensions and layout and analyzing observations video from past tsunamis reducing constrictions and deepening channels within harbors would greatly reduce tsunami current speeds and the potential for scour the maritime community and state regulatory agencies should work together to streamline the review process to assist recovery efforts after significant tsunamis

physical modelling of local scour at twin piles under combined waves and current abstract under the actions of ocean waves and current severe local scour can be induced around pile groups significantly compromising the safety of marine structures a series of flume tests were conducted for physical modelling the local scouring process around twin piles in the cohesionless soils under combined waves and currents and compared with the pure current case the effects of non dimensional pile spacing g d and flow skew angle on the scour depth and time scale of scour around twin piles are intensively examined the experimental observations indicate that the influence of pile spacing on the scour depth development is much more significant for the side by side 90 arrangement than that for the tandem arrangement 0 with the increase of flow skew angle the maximum scour depth is remarkably enhanced within the examined range 0 g d 3 0 when g d 3 0 the pile group effect on the time scale is generally negligible for pure current cases whereas a prominent pile group effect can still be observed for combined wave current cases especially for the side by side arrangement a parameter of equivalent pile diameter is then introduced for evaluating the maximum scour depth at the twin piles with the previous formulas for the single pile based on the existing and present experimental data the empirical formula of dimensionless equivalent pile diameter as the function of g d and is established to predict the maximum scour depth at the twin piles

experimental observations of tsunami induced scour at onshore structures tsunami inundation of the coastal environment can induce scour at structure foundations leading to failure a series of experiments are made using a unique pneumatic long wave generator to generate tsunami wave periods of 25 147 s equating to 3 17 3 min at 1 50 froude scale the waves propagate over a sloping bathymetry and impinge upon a square structure founded onshore in a flat sediment bed flow velocity height and scour depth are recorded as a function of time during tsunami inundation the rate of scour is observed to be time dependent equilibrium which is not attained is argued to be an inappropriate measure for time dependent transient flows such as tsunami in which the flow velocity depth and direction are variable the maximum scour depth is recorded and critically is observed not to be equal to the final depth due to significant sediment slumping when flow velocities reduce in the latter stages of inundation current and wave scour predictor equations over predict the scour while the asce 7 16 method under predicts comparisons with available data in the literature show longer inundation durations increase the amount of scour

numerical investigation of flow and scour around a vertical circular cylinder flow and scour around a vertical cylinder exposed to current are investigated by using a three dimensional numerical model based on incompressible reynolds averaged navier stokes equations the mod

geological constraints on the thermodynamic properties of the stilbite stellerite solid solution in low grade metabasalts abstract standard state thermodynamic data for stilbite ca2naal5si13o36 16h2o and stellerite ca2al4si14o36 14h2o together with mixing properties of the stilbite stellerite solid solution stilbite ss are derived through assessment of geological observations of stilbite ss compositions in metabasalts experimental phase equilibria and calorimetric observations measured compositions of stilbite ss in tertiary metabasalts in iceland and icelandic geothermal systems change systematically towards the stellerite endmember with increasing stratigraphic depth and temperature standard molal volumes heat capacities and entropies for the endmembers of the solid solution are derived through critical review of published crystallographic and calorimetric data for natural stilbite ss standard molal gibbs energies of formation at 298 15 k and 1 bar for stilbite 4 946 475cal mol 1 and stellerite 4 762 036 cal mol 1 and the mixing properties of the solid solution are retrieved from observed phase and compositional relations in metabasalts at berufjordur iceland measured temperatures of zeolite mineral distribution in active geothermal systems and published observations of reversed phase equilibria mixing in stilbite ss can be described with an athermal solid solution model thermodynamic data resulting from our analysis provide close correlation between compositions of stilbite ss in icelandic geothermal systems predicted from compositions of geothermal solutions and observed compositions of these minerals in low grade metabasalts of iceland as well as the observed temperature of the stilbite ss to laumontite leonhardite transition in icelandic geothermal systems stilbite ss composition in metabasalts is a sensitive function of temperature fluid composition coexisting minerals especially silica polymorphs and geothermal gradient

mechanisms and rates of plagioclase carbonation reactions abstract plagioclase is one of the most abundant sources of calcium in the earth s crust and it may play an important role for co2 storage this study address the carbonation of anorthite rich plagioclase an67 an73 in a system with fluid transport and under stagnant conditions a combined approach of flow through column and batch experiments has been used experimental conditions ranging from 100 to 250 c and 20 to 120 bar and different preparations of the starting material were applied the overall carbonation reaction consists of plagioclase dissolution coupled to a number of precipitation reactions the flow through column experiments at 250 c showed stoichiometric dissolution of the plagioclase al hydroxide proto al hydroxide nucleated on the plagioclase as the first phase to precipitate a secondary porosity developed between the shrinking plagioclase and the enclosing proto al hydroxide calcite as the second phase to precipitate filled the primary pore space a reaction front was developed separating the zone at the inlet where all the plagioclase had dissolved and the less reacted outlet of the column redissolution of the calcite and formation of euhedral boehmite crystals occurred when a sufficient amount of plagioclase had dissolved clay minerals were not precipitated in the column experiments between 11 and 30 of the plagioclase was dissolved within 72 168 h of reaction a much higher extent of plagioclase dissolution was observed in the high pressure experiments compared to the low pressure however a smaller share of the released ca was trapped as calcite in the high pressure experiments both observations are consistent with a more rapid progression of the dissolution front at high pressure the batch experiments showed conversion of the plagioclase to a mixture of al hydroxide possibly gibbsite clays and calcite a range in conversion from below the detection limit to 91 was observed within reaction periods of 24 72 h crystallinity of the feldspar was the most important factor contributing to increased reaction rates a general positive effect of increasing temperature on the conversion is observed for all materials whereas pressure and the addition of cacl2 did not have any effect the carbonation of plagioclase at stagnant conditions is slow compared to olivine at temperatures around 200 c however industrial operations involving high fluid flows of co2 water mixtures induce gradients in ph or solute concentrations which may lead to increased reaction rates and changes in porosity permeability

numerical simulation of scour and backfilling processes around a circular pile in waves abstract this study continues the investigation of flow and scour around a vertical pile reported by roulund et al 2005 flow and scour backfilling around a vertical pile exposed to waves are investigated by using a three dimensional numerical model based on incompressible reynolds averaged navier stokes equations the model incorporates 1 k turbulence closure 2 vortex shedding processes 3 sediment transport both bed and suspended load as well as 4 bed morphology the numerical simulations are carried out for a selected set of test conditions of the laboratory experiments of sumer et al 1997 2013a and the numerical results are compared with those of the latter experiments the simulations are carried out for two kinds of beds rigid bed and sediment bed the rigid bed simulations indicate that the vortex shedding for waves around the pile occurs in a one cell fashion with a uniform shedding frequency over the height of the cylinder unlike the case for steady current where a two cell structure prevails the rigid bed simulations further show that the horseshoe vortex flow also undergoes substantial changes in waves the amplification of the bed shear stress around the pile including the areas under the horseshoe vortex and the lee wake region is obtained for various values of the keulegan carpenter number the principal parameter governing the flow around the pile in waves the present model incorporated with the morphology component is applied to several scenarios of scour and backfilling around a pile exposed to waves in the backfilling simulations the initial scour hole is generated either by a steady current or by waves the present simulations indicate that the scour and backfilling in waves are solely governed by the lee wake flow in agreement with observations the numerical model has proven successful in predicting the backfilling of scour holes exposed to waves the results of the numerical tests indicate that the equilibrium depth of scour holes is the same for both the scour and the backfilling for a given keulegan carpenter number in full agreement with observations

full scale cfd simulation of tsunamis part 1 model validation and run up abstract this paper presents numerical simulations of the propagation shoaling and run up of full scale tsunami waves the simulations are performed with a model solving reynolds averaged navier stokes equations with k turbulence closure and is one of very few studies involving cfd simulations at full tsunami scale involving full resolution of small scale dispersive effects as well as wave breaking it is demonstrated that a combination of previous analytical and empirical expressions for run up heights and inundation speeds match those simulated well this indicates that these are reasonable first approximation even in cases where the underlying assumption of linearity of the incoming tsunami is violated as well as in cases where breaking occurs though they generally slightly underestimate both run up height and inundation speed it is shown that the run up of tsunamis can manifest in different ways depending on the initial wave shape and slope of the coast and three qualitative run up types previously identified in the literature are described in detail it is further shown that the shorter waves of an undular bore which appear during lengthy propagation in shallow water can either maintain their shape the entire distance to shore or break far offshore creating a breaking bore it is demonstrated the front of the breaking bore will not appear as steep for n waves as single waves because these need to re wet the drawn down region before reaching the original shoreline finally the importance of shorter waves riding on the front of the tsunami is discussed it is shown that they have little impact on the run up height and inundation speed but are important in terms of local flow velocities the results presented here are part 1 of a larger study where part 2 involves details of the tsunami induced boundary layer dynamics bed shear stresses and implication for sediment transport

the impact of dolomite and plagioclase weathering on the chemistry of shallow groundwaters circulating in a granodiorite dominated catchment of the sila massif calabria southern italy abstract this work is aimed at investigating the weathering processes of the granodiorites cropping out in a small catchment of the sila massif the mineral constituents in this granodiorite are plagioclase often zoned with a ca rich core and a na rich rim quartz chlorite k feldspar white mica and epidote during this study dolomite was discovered in local stream sediments as separate monomineralic grains probably resulting from erosion of veins cutting the crystalline rocks prevailing dissolution of foreign dolomite and a ca rich plagioclase is suggested by the ca mg hco3 chemical composition of local groundwaters and stream waters which is rather unexpected for waters interacting with granitoid rocks these qualitative observations are quantitatively confirmed by reaction path modelling of the weathering processes occurring in the study area which was carried out using the eq3 6 software package version 8 0 and the double solid reactant method indeed it was possible to ascertain that the release of both major dissolved constituents and several trace elements ba co cr fe mn ni pb sr v and zn from rocks to waters is chiefly controlled by the dissolution of foreign dolomite and the ca rich core of zoned plagioclases

currents drag and sediment transport induced by a tsunami 1 we report observations of water surface elevation currents and suspended sediment concentration ssc from a 10 m deep site on the inner shelf in northern monterey bay during the arrival of the 2010 chile tsunami velocity profiles were measured from 3 5 m above the bed mab to the surface at 2 min intervals and from 0 1 to 0 7 mab at 1 hz ssc was determined from the acoustic backscatter of the near bed profiler the initial tsunami waves were directed cross shore and had a period of approximately 16 min maximum wave height was 1 1 m and maximum current speed was 0 36 m s during the strongest onrush near bed velocities were clearly influenced by friction and a logarithmic boundary layer developed extending more than 0 3 mab we estimated friction velocity and bed shear stress from the logarithmic profiles the logarithmic structure indicates that the flow can be characterized as quasi steady at these times at other phases of the tsunami waves the magnitude of the acceleration term was significant in the near bed momentum equation indicating unsteady flow the maximum tsunami induced bed shear stress 0 4 n m2 exceeded the critical shear stress for the medium grained sand on the seafloor cross shore sediment flux was enhanced by the tsunami oscillations of water surface elevation and currents continued for several days the oscillations were dominated by resonant frequencies the most energetic of which was the fundamental longitudinal frequency of monterey bay the maximum current speed hourly timescale in 18 months of observations occurred four hours after the tsunami arrived

on the runup of long waves on a plane beach 1 using the records of free surface fluctuations at several locations during the 2011 japan tohoku tsunami we first show that the leading tsunami waves in both near field and far field regions are small amplitude long waves these leading waves are very different from solitary waves we then focus on investigating the evolution and runup of non breaking long waves on a plane beach which is connected to a constant depth region for this purpose we develop a lagrangian numerical model to solve the nonlinear shallow water equations the lagrangian approach tracks the moving shoreline directly without invoking any additional approximation we also adopt and extend the analytical solutions by synolakis 1987 and madsen and schaffer 2010 for runup and rundown of cnoidal waves and a train of multiple solitary waves the analytical solutions for cnoidal waves compare well with the existing experimental data and the direct numerical results when wave amplitudes are small however large discrepancies appear when the incident amplitudes are finite we also examine the relationship between the maximum runup height and the leading wave form it is concluded that for a single wave the accelerating phase of the incident wave controls the maximum runup height finally using the analytical solutions for the approximated wave forms of the leading tsunamis recorded at iwate south station from the 2011 tohoku japan tsunami we estimate the runup height

experimental determination of plagioclase dissolution rates as a function of its composition and ph at 22 c abstract the steady state far from equilibrium dissolution rates of nine distinct plagioclases ranging in composition from an2 to an89 were measured in mixed flow reactors at 22 2 c and ph from 2 to 11 the dissolution rates of all plagioclases based on silica release show a common u shaped behaviour as a function of ph where rates decrease with increasing ph at acid condition but rise with increasing ph at alkaline conditions consistent with literature findings constant ph plagioclase dissolution rates increase with increasing anorthite content at acidic conditions measured anorthite dissolution rates are 2 5 orders of magnitude faster than those of albite at ph 2 perhaps more significantly rates are independent of plagioclase composition at alkaline conditions interpretation and data fitting suggests that plagioclase dissolution rates are consistent with their control by the detachment of si rich activated complexes formed by the removal of al from the mineral framework taking account of this mechanism and transition state theory yields equations describing plagioclase dissolution rates r as a function of both the mineral and aqueous fluid compositions found in natural earth surface systems for ph 6 rates are consistent with log r mol cm 2 s 0 35 log a h 3 a al 3 11 53 and for ph log r mol cm 2 s n acid log a h 3 a al 3 0 033 an 14 77 where an represents the percent anorthite in the plagioclase solid solution ai corresponds to the activity of the ith aqueous species and nacid is given by n acid 0 004 an 0 05

run up of tsunamis and long waves in terms of surf similarity abstract in this paper we review and re examine the classical analytical solutions for run up of periodic long waves on an infinitely long slope as well as on a finite slope attached to a flat bottom both cases provide simple expressions for the maximum run up and the associated flow velocity in terms of the surf similarity parameter and the amplitude to depth ratio determined at some offshore location we use the analytical expressions to analyze the impact of tsunamis on beaches and relate the discussion to the recent indian ocean tsunami from december 26 2004 an important conclusion is that extreme run up combined with extreme flow velocities occurs for surf similarity parameters of the order 3 6 and for typical tsunami wave periods this requires relatively mild beach slopes next we compare the theoretical solutions to measured run up of breaking and non breaking irregular waves on steep impermeable slopes for the non breaking waves the theoretical curves turn out to be superior to state of the art empirical estimates finally we compare the theoretical solutions with numerical results obtained with a high order boussinesq type method and generally obtain an excellent agreement

full scale cfd simulation of tsunamis part 2 boundary layers and bed shear stresses abstract this paper presents results from numerical simulations of the propagation and run up of full scale tsunamis using a reynolds averaged navier stokes model with emphasis on the resulting boundary layers and bed shear stresses spatial distributions of the shields and rouse parameters during run up and draw down show that for the tsunamis considered with a sediment grain size corresponding to medium sand considerable sediment transport shields parameter o 10 o 100 can be expected during run up and that the sediment transport can be expected to be dominated by suspended load the results likewise show that the expected sediment transport during draw down will similarly be considerable and dominated by suspension the tsunami induced boundary layers are monitored in time and the observed boundary layer thickness ranges from spanning only a small fraction of the water depth to spanning the entire depth the velocity profiles beneath the tsunamis are shown to have good correspondence with a logarithmic profile within the boundary layer similarly the bed shear stresses beneath the tsunamis are investigated and a new and simple engineering model is developed for predicting the temporal variation of the bed shear stress based only on a free stream velocity signal the new engineering model is shown give better predictions for the bed shear stress than a standard manning approach and is likewise shown in the appendix to produce reasonable predictions for shorter wind scale waves it is finally also shown how the temporal evolution of the boundary layer thickness can be predicted based on the free stream velocity signal alone the results presented here are part 2 of a larger study where part 1 presents the model validation and detailed descriptions of the run up process

reaction of plagioclase feldspars with co2 under hydrothermal conditions abstract geological storage of co 2 in plagioclase bearing sediments granitic rocks and fractured basalts is expected to have a variety of geochemical and geomechanical effects including mineral trapping and porosity permeability changes the amount of co 2 trapped by mineralisation and the extent of any changes in host rock transport or mechanical properties depend on rock composition to date studies of mineralisation have mainly been based on dissolution and precipitation experiments performed at ambient surface conditions or at slightly elevated temperature and pressure however the reactions that occur under in situ conditions are poorly constrained in an attempt to determine the secondary phases formed in the plagioclase co 2 water system under such conditions we performed a set of batch experiments at temperatures in the range 200 300 c using carbon dioxide pressures from 0 4 to 15 mpa we investigated reaction of anorthite and albite which are expected to precipitate calcite and kaolinite and dawsonite and quartz respectively however in most of our experiments reactions precipitating clays kaolinite and smectite or illite boehmite and a mg ni fe hydrotalcite like phase dominated the nickel being derived from the reaction vessel little or no carbonate and no dawsonite were detected additional feldspar free control experiments employing mg rich brine showed that carbonates would be preserved in our feldspar experiments if formed but that a carbonate substrate is needed to promote precipitation since the secondary phases formed in our plagioclase experiments are stable under a wide range of conditions we expect that they will also form under co 2 storage systems with suitable fluid rock composition from our results we conclude that clay precipitation can proceed or accompany carbonate precipitation depending on the availability of carbonate substrate though an artefact in our experiments in the context of subsurface alkaline waste injection hydrotalcite may play a positive role here by immobilising heavy metals while carbonates will mineralise the co 2

predictions of the equilibrium depth and time scale of local scour below a partially buried pipeline under oblique currents and waves abstract this paper presents experimental results on temporal developments of local scour below a partially buried pipeline under oblique currents waves the effects of the flow incident angle 45 0 denotes that the currents waves are perpendicular to the pipeline and the embedment to diameter ratio e d 0 5 e d 0 denotes no embedment on the equilibrium depth and time scale of scour were quantitatively investigated the experimental results indicate that with the increase of the embedment to diameter ratio from 0 to 0 5 the equilibrium depth of scour decreases by up to 30 and the time scale increases by approximately 5 times with the increase of the flow incident angle from 0 to 45 the equilibrium depth decreases by approximately 25 and the time scale increases by approximately 0 7 times a uniform empirical relationship between the equilibrium depth for arbitrary conditions s i e for 0 or e d 0 and that for a conventional case s0 for 0 and e d 0 is newly proposed for both current and wave conditions based on theoretical derivation and curve fitting to the experimental data where s0 can be easily predicted from existing empirical formulae the correlation analysis indicates that the experimental results of the equilibrium depth can be well represented by the newly proposed formula for predicting the time scale of scour process a theoretical approach based on the erosion rate of sediment which was originally proposed for a conventional case is expanded to arbitrary conditions it is indicated that the time scales of scour obtained from the theoretical approach are well coincident with the experimental values finally an empirical relationship between the time scale for arbitrary conditions t and that for a conventional case t0 was established based on the theoretical derivation the newly proposed empirical formula is found to provide satisfactory predictions of the time scale compared with the present experimental results and those published

hematite in porous red clouded feldspars evidence of large scale crustal fluid rock interaction abstract transmission electron microscopy shows that red clouded alkali feldspars from granitic rocks contain numerous open pores up to several hundred nanometres in cross section and that almost every pore contains rosettes or needles of crystalline hematite in the samples described here the hematite forms at the reaction interfaces at which plagioclase feldspar is replaced by alkali feldspar these observations together with the fact that the origin of the porosity can be explained by the mechanism of sub solidus mineral fluid replacement processes indicate that hematite is a direct product of fluid rock interaction and is not a solid state exsolution product from the feldspar

reactive transport modeling of plug flow reactor experiments quartz and tuff dissolution at 240 c abstract extension of reactive transport modeling to predict the coupled thermal hydrological and chemical evolution of complex geological systems is predicated on successful application of the approach to simulate well constrained physical experiments in this study steady state effluent concentrations and dissolution precipitation features associated with crushed quartz and tuff dissolution at 240 c have been determined experimentally using a plug flow reactor pfr and scanning electron microscopy sem techniques then modeled with the reactive transport simulator gimrt steefel and yabusaki 1996 using a linear rate law from transition state theory tst for quartz dissolution interdependence of the specific surface area am and reaction rate constant km predicted from the modeling agrees closely with that obtained from an analytical solution to the reaction transport equation without diffusion dispersion verifying the advection dominant nature of the pfr experiments independently determined aqtz and kqtz from the literature are shown to be internally consistent with respect to the model and analytical interdependence implying appropriateness of the linear tst rate law and adequacy of bet determined am for use in modeling pfr experiments applications of this integrated approach for monomineralic dissolution include assessment of internal consistency among independent am and km data estimation of km from bet determined am and rapid evaluation of alternative rate laws for tuff dissolution accurate simulation of the experimental steady state effluent concentrations to within 3 for na al and k to within 15 for si and ca and dearth of alteration phases

rans based simulation of turbulent wave boundary layer and sheet flow sediment transport processes abstract a numerical model coupling the horizontal component of the incompressible reynolds averaged navier stokes rans equations with two equation k turbulence closure is presented and used to simulate a variety of turbulent wave boundary layer processes the hydrodynamic model is additionally coupled with bed and suspended load descriptions the latter based on an unsteady turbulent diffusion equation for simulation of sheet flow sediment transport processes in addition to standard features common within such rans based approaches the present model includes 1 hindered settling velocities at high suspended sediment concentrations 2 turbulence suppression due to density gradients in the water sand mixture 3 boundary layer streaming due to convective terms and 4 converging diverging effects due to a sloping bed the present model therefore provides a framework for simultaneous inclusion of a number of local factors important within cross shore wave boundary layer and sediment transport dynamics the hydrodynamic model is validated for both hydraulically smooth and rough conditions based on wave friction factor diagrams and boundary layer streaming profiles with the results in excellent agreement with experimental and or previous numerical work the sediment transport model is likewise validated against oscillatory tunnel experiments involving both velocity skewed and acceleration skewed flows as well as against measurements beneath real progressive waves model capabilities are exploited to investigate the importance of boundary layer streaming effects on sediment transport in selected velocity skewed conditions for the medium sand grain conditions considered the model results suggest that streaming effects can enhance onshore sediment transport rates by as much as a factor of two moreover for fine sand conditions streaming and related convective effects are demonstrated to potentially reverse the direction of net transport i e from offshore to onshore relative that predicted in oscillatory tunnel conditions the developed model is implemented within the popular matlab environment and hence may be attractive for both research and educational purposes

experimental and numerical study of wave induced backfilling beneath submarine pipelines abstract this paper presents results of complementary experimental and numerical studies involving wave induced backfilling of current generated scour holes beneath submarine pipelines the laboratory experiments are conducted in a wave plus current flume utilizing laser doppler anemometry to measure velocities synchronized flow visualizations using digital image technology along with live bed scour and backfilling measurements each experiment is based on a two stage process 1 initial scour induced by a pure current followed by 2 backfilling induced by pure waves either regular or irregular the time series of scour depths are closely monitored through video recordings systematic analysis of these has resulted in a closed form expression for the backfilling time scale which is demonstrated to be a full order of magnitude greater than the well known time scale of scour with both governed primarily by the shields parameter the developed expression is strictly valid for the current to wave backfilling scenarios considered while likely serving as an upper limit for more general wave induced backfilling circumstances the experiments are complemented by similar backfilling simulations utilizing a fully coupled hydrodynamic and morphodynamic cfd model the numerical simulations demonstrate the ability of the model to predict backfilling towards expected equilibrium scour depths based on the new wave climate with time scales reasonably in line with experimental expectations

numerical simulation of tsunami scale wave boundary layers this paper presents a numerical study of the boundary layer flow and properties induced by tsunami scale waves for this purpose an existing one dimensional vertical 1dv boundary layer model based on the horizontal component of the incompressible reynolds averaged navier stokes rans equations is newly extended to incorporate a transitional variant of the standard two equation k turbulence closure the developed numerical model is successfully validated against recent experimental measurements involving transient solitary wave boundary layers as well as for oscillatory flows collectively demonstrating the ability to reproduce accurate velocity profiles turbulence and bed shear stresses on both smooth and rough beds the validated model is then employed for the study of transient wave boundary layers at full tsunami scales covering a wide and realistic geophysical range in terms of the flow duration bottom roughness and associated reynolds numbers for this purpose three different synthetic idealised tsunami wave descriptions are considered i e invoking 1 single wave solitary like but with independent period and wave height 2 sinusoidal and 3 n wave descriptions the flow boundary layer thickness turbulence and bed shear stresses induced are systematically monitored and parameterised under both hydraulically smooth and rough bed conditions the results generally support a notion that the boundary layers induced by tsunami scale waves are both current like due to their long durations as well as wave like in the sense that the boundary layer will not necessarily span the entirety of the water column the results likewise suggest that there is a continuum connecting wind wave and tsunami wave scales as existing expressions commonly used for characterising boundary layer properties beneath wind waves maintain reasonable accuracy when extrapolated to full tsunami scales boundary layers driven by actual field measured tsunami signals are likewise simulated stemming from both the 2004 indian ocean as well as the 2011 tohoku events these results are reconciled with the various synthetic tsunami signals considered generally confirming their usefulness as idealised tsunami waves

tsunami induced scour around monopile foundations abstract a fully coupled hydrodynamic and morphologic numerical model is presented and utilized for the simulation of tsunami induced scour around a monopile structure representative of those commonly utilized as offshore wind turbine foundations at moderate depths i e for depths less than 30 m the model is based on solutions to reynolds averaged navier stokes equations coupled with two equation k turbulence closure with additional bed and suspended load descriptions forming the basis for sea bed morphology the model is first validated for flow bed shear stresses and scour within a steady current where a generally excellent match with experimentally based results is found a methodology for maintaining and assessing hydrodynamic and morphologic similarity between field and laboratory model scale tsunami events is then presented combining diameter based froude number similarity with that based on the dimensionless wave boundary layer thickness to monopile diameter ratio this methodology is utilized directly in the selection of governing tsunami wave parameters i e velocity magnitude and period used for subsequent simulation within the numerical model with the tsunami induced flow modelled as a long sinusoidally varying current the flow sediment transport and scour processes beneath up to ten tsunami waves are simulated in succession these illustrate a generally accumulative scour process i e a relatively rapid scour induced by the leading wave with an additional build up of the scour depth during additional trailing waves the resulting scour seems to approach an equilibrium value after sufficient time duration which corresponds reasonably to that predicted by existing steady current scour depth expressions after accounting for the finite boundary layer thickness induced by the unsteady tsunami wave i e it is important to incorporate both current like as well as wave like aspects of the long tsunami event based on the simulated results a simple methodology for predicting the tsunami induced scour depth in engineering practice is finally developed this methodology is demonstrated to match the predicted scour development for all of the simulated flows considered ranging from the series of transient tsunami waves to the steady current limit

numerical and experimental investigation of flow and scour around a circular pile the flow around a vertical circular pile exposed to a steady current is studied numerically and experimentally the numerical model is a three dimensional model the model validation was achieved against new experimental data which include two component laser doppler anemometry lda flow measurements and the hot film bed shear stress measurements and reported in the present paper and the data of others and a k w turbulence model was used for closure the model does not have a free surface facility and therefore is applicable only to cases where the froude number is small fr 0 0 2 the flow model was used to study the horseshoe vortex and lee wake vortex flow processes around the pile the influence on the horseshoe vortex of three parameters namely the boundary layer thickness the reynolds number and the bed roughness was investigated in the latter investigation the steady solution of the model was chosen a study of the influence of the unsteady solution on the previously mentioned flow processes was also carried out the ranges of the parameters covered in the numerical simulations are the boundary layer thickness to pile diameter ratio is varied from 2 x 10 2 to 10 2 the pile reynolds number from 10 2 to 2 10 6 and the pile diameter to roughness ratio from 2 to about 10 3 the amplification of the bed shear stress around the pile including the areas under the horseshoe vortex and the lee wake region was obtained for various values of the previously mentioned parameters the steady state flow model was coupled with a morphologic model to calculate scour around a vertical circular pile exposed to a steady current in the case of non cohesive sediment the morphologic model includes i a two dimensional bed load sediment transport description and ii a description of surface layer sand slides for bed slopes exceeding the angle of repose the results show that the present numerical simulation captures all the main features of the scour process the equilibrium scour depth obtained from the simulation agrees well with the experiments for the upstream scour hole some discrepancy up to 30 was observed however for the downstream scour hole the calculations show that the amplification of the bed shear stress around the pile in the equilibrium state of the scour process is reduced considerably with respect to that experienced at the initial stage where the bed is plane

experimental study of tsunami induced scour around a monopile foundation abstract this paper presents an experimental study of the tsunami induced scour process around a monopile foundation representative of those commonly used for offshore wind farms the scour process is studied by subjecting the monopile to a time varying current which enables a properly down scaled experiment from the boundary layer and scour perspective it is shown how the scaled experiments corresponds to real life idealized tsunami cases with periods ranging from 10 to 40 min it is then shown that the boundary layers of the model tsunami are well described by recently developed empirical relations for tsunami boundary layers by subjecting the monopile to several successive tsunami waves the scour process is shown to occur in a stepwise cumulative fashion with the final equilibrium scour depth tending to the depth limited steady current limit it is shown that the entire scour development can reasonably be predicted by a recently developed simple engineering model finally the experimental results are compared to a fully coupled hydrodynamic and morphologic cfd model and a good correspondence is obtained

meteoric water basalt interactions ii a field study in n e iceland the compositions of rain snow melt spring and geothermal waters from the rift zone of n e iceland can be explained by seaspray addition chemical fractionation at the seawater air interface burning of fossil fuel farming activities purification by partial melting of snow and ice dissolution of basalts and buffering by alteration minerals the dissolution of the rocks appears to be incongruent during solute acquisition spring compositions move through the stability fields of kaolinite and smectite to the laumontite and illite fields all but four of the springs are undersaturated with respect to calcite silica concentrations are compatible with the solubility of basaltic glass the reactions reflected in the spring waters appear to have taken place sealed off from atmospheric co2 after initial saturation the geothermal waters which are recharged by the spring waters are depleted in mg and ca but enriched in carbon and sulfur with respect to dissolution of primary rocks expressions are derived relating dissolution rates of rocks age of groundwaters physical properties of groundwaters and mass transfer the characteristic rock particle radii in the cold water aquifers range from 0 2 to 2 cm and the characteristic crack openings are of the order 0 04 to 0 4 cm using laboratory studies on the icelandic lavas as a guide the residence times of the cold waters in the aquifers can be estimated at 60 days to 4 years the average active surface area of the aquifers enclosing 1000 g of spring water is of the order of 0 6 to 6 m2 and these 1000 g of water have reacted with 0 1 to 1 g of basaltic rocks the same mass of thermal water has interacted with 100 to 300 g of unaltered rocks

soil mineralogy at the mars exploration rover landing sites an assessment of the competing roles of physical sorting and chemical weathering 1 soils in gusev crater and meridiani planum derive primarily from a surface dominated by basalt the modal mineralogy of primary igneous and secondary alteration phases in the soils is estimated using mossbauer minites and apxs spectra primary minerals include plagioclase pyroxene and olivine with less common apatite magnetite and chromite secondary phases are dominated by sulfates and include nanophase oxides chlorides hematite and are assumed to include amorphous silica and phyllosilicates most soil chemical compositions overlap with basalts indicating that despite the presence of a secondary component in the soils they have not been significantly chemically weathered we modeled the significance of olivine dissolution by acid s by iteratively removing the molar feot mgo component olivine proxy from the mean bulk compositions of the gusev rock classes adirondack algonquin and irvine until none remained regardless of modeling conditions acid s alteration cannot account for many soils in gusev crater that are either depleted or enriched in molar feot mgo although it is a process capable of explaining some soil compositions based on a rock and mineral mixing model supports our hypothesis for soil formation that consists of surface comminution by impact gardening followed by compositional modification by hydrodynamic sorting and admixing of secondary components including phyllosilicates and sulfates such a physical process can produce the range of molar feot mgo in soils by concentrating or depleting specific minerals for example dust and fine sands are enriched in molar feot mgo relative to coarse sand which suggests accumulation of more mafic phases in finer grain fractions

sediment transport and trench development beneath a cylinder oscillating normal to a sandy seabed abstract the purpose of this study is to explore the conditions in which trenches form beneath oscillating cylinders such as pipelines cables or idealised chains close to the seabed experiments are conducted by oscillating a circular cylinder in a direction normal to an initially flat sandy bed across a relatively wide parameter space the transport patterns and trench geometries reveal three transport regimes that are linked to vortex dynamics and depend primarily on the ratio of oscillation amplitude to cylinder diameter k c number for k c 4 sediment motion results in bedload transport that is symmetric about the cylinder centreline this leads to the formation of two parallel trenches with a prominent ridge forming directly beneath the cylinder for 4 k c 9 sediment motion occurs via localised transport events which are associated with the motion of vortices shed from the cylinder these transport events are irregular but occur on both sides of the cylinder and lead to the formation of a symmetric trench geometry for 9 k c 12 the sediment motion is characterised by localised transport events and asymmetric bedload transport driven by overall vortex dynamics in terms of trench size the maximum equilibrium depth is found to increase with k c and a mobility number defined in terms of the maximum cylinder velocity the initial rate of trench development also increases with k c number and with an additional dependency on the cylinder number the cylinder motions required to initiate trenching are predicted well using continuity arguments and an oscillatory boundary layer assumption provided the k c number and minimum gap between the cylinder and the bed are relatively small the findings in this study provide insight into the mechanisms and prediction of trench formation in particular this study reveals that significant trenches can form in sandy seabeds solely due to fluid flow induced by pipeline cable chain motion without direct seabed contact which has implications for structural fatigue

numerical investigation of wave plus current induced scour beneath two submarine pipelines in tandem abstract two dimensional 2d local scour beneath two submarine pipelines in tandem under wave plus current conditions is investigated numerically a fully coupled hydrodynamic and morphologic model based on unsteady reynolds averaged navier stokes urans equations with the k turbulence closure is applied the model is validated against existing experimental measurements involving live bed scour beneath a single pipeline and beneath two pipelines in tandem respectively the model is then employed to simulate scour beneath two tandem pipelines under wave plus current conditions for a variety of keulegan carpenter k c numbers and relative current strengths horizontal gap ratios the horizontal gap distance between two pipelines divided by the pipeline diameter ranging from 1 to 4 are modelled it is found that for conditions involving waves plus a low strength current the scour pattern beneath two pipelines behaves like that in the pure wave condition conversely when the current has equal strength to the wave induced flow the scour pattern beneath two pipelines resembles that in the pure current condition it is also observed that in the pure wave condition the equilibrium scour depth beneath each pipeline is affected by both k c and the horizontal gap ratio except for k c 5 6 for such a small k c the horizontal gap ratio has insignificant influence on the equilibrium scour depth since vortex shedding does not occur when the current strength relative to the waves is low the scour development beneath the upstream and the downstream pipelines are similar however when the current has equal strength to the waves the scour development beneath the downstream pipeline has a different pattern to that upstream namely smaller horizontal gap ratios result in delayed scour beneath the downstream pipeline

varied pathways of river borne clay minerals in a near shore marine region a case study of sediments from the elbe and weser rivers and the se north sea abstract the the results outline significant systematic changes in the proportions of clay minerals in the k rb ratios the k ar data and in the heavy metal contents at the fluvial estuarine transition and towards the marine environment these changes result from a progressive mixing of suspended fluvial material with reworked pleistocene sediments at the bottom of the north sea near shore the proportion of reworked pleistocene sediment amounts only 20 30 the mixture is distributed within a 100 km wide zone mainly by currents parallel to the coast it is also transported during flood tide into the estuaries where it is mixed further with suspended fluvial material the k rb ratios and k ar dates obtained from illite prove to be particularly useful for modeling the mixing of the clay minerals as well as their distribution patterns and origin

numerical simulation of wave induced scour and backfilling processes beneath submarine pipelines abstract a fully coupled hydrodynamic morphodynamic numerical model is presented and utilized for the simulation of wave induced scour and backfilling processes beneath submarine pipelines the model is based on solutions to reynolds averaged navier stokes equations coupled with k turbulence closure with additional bed and suspended load descriptions forming the basis for sea bed morphology the morphological evolution is updated continuously rather than being based e g on period or other time averaging techniques simulations involving wave induced scour over the range of keulegan carpenter number 5 6 kc 30 demonstrate reasonable match with previous experiments both in terms of the equilibrium scour depth as well as the scour time scale wave induced backfilling processes are additionally studied by subjecting initial conditions taken from scour simulations with larger kc to new wave climates characterized by lower kc values the simulations considered demonstrate the ability of the model to predict backfilling toward expected equilibrium scour depths based on the new wave climate in line with experimental expectations the simulated backfilling process is characterized by two stages 1 an initial re distribution phase involving re organization of sediments in the immediate vicinity of the pipeline potentially followed by 2 a more lengthy backfilling evolution toward equilibrium scour depth the simulated backfilling time scales are of the same order of magnitude as in experiments though the multi stage process complicates a more systematic characterization the simulated sequences of scour and backfilling achieved within the present work are estimated to represent temporal durations of up to approximately 12 h at full practical scales

formation and development of a breaker bar under regular waves part 1 model description and hydrodynamics abstract in this work a detailed hydrodynamic model is presented which is used for the study of cross shore sediment transport and morphodynamics in two dimensions the model is described in the framework of the generally unstructured finite volume method considerable emphasis is put on those subtleties in the morphological formulation which are required to achieve mass conservation for the amount of sediment in the bed and in suspension in this first part of two the hydrodynamic description over the cross shore profile is presented the model is validated against an experiment with detailed measurements of the free surface and turbulence over a fixed breaker bar profile a test matrix covering a large interval of the surf similarity parameter is simulated and the phase lag between the breakpoint and the initiation of the setup is described the relation of this phase lag to a cross shore delay in dissipation of organised energy into turbulence is described the relation of this phase lag to the distribution of the location of maxima in bed shear stresses and magnitude of the undertow is also described furthermore processes in the hydrodynamics which will have a smoothing effect on the mean cross shore sediment transport and morphodynamic response are considered all simulations are presented for regular waves and for values of the deep water surf similarity parameter 0 in the range from 0 08 to 1 19 i e covering both spilling and plunging breakers