intrinsic nonlinearity and spectral structure of internal tides at an idealized mid atlantic bight shelf break abstractto quantify dynamical aspects of internal tide generation at the mid atlantic bight shelf break this study employs an idealized ocean model initialized by climatological summertime stratification and forced by monochromatic barotropic tidal currents at the offshore boundary the froude number of the scenario is subunity and the bathymetric slope offshore of the shelf break is supercritical a barotropic to baroclinic energy conversion rate of 335 w m 1 is found with 14 of the energy locally dissipated through turbulence and bottom friction and 18 radiated onto the shelf consistent with prior studies nonlinear effects result in additional super and subharmonic internal waves at the shelf break the subharmonic waves are subinertial evanescent and mostly trapped within a narrow beam of internal waves at the forcing frequency they likely result from nonresonant triad interaction associated with strong nonlinearity strong vertical shear associated with the subharmonic waves tends to enhanc

spatial and temporal progression of internal erosion in cohesionless soil permeameter tests were performed on four widely graded cohesionless soils to study their susceptibility to in ternal erosion test specimens were reconstituted as a saturated slurry consolidated and then subjected to multi stage seepage flow under increasing hydraulic gradient the occurrence of internal instability is described qualitatively from vis ual observations through the wall of the permeameter during a test and from post test observations it is also described quantitatively from change of hydraulic gradient within the specimen and from axial displacement during a test the re sults provide a novel insight into the spatial and temporal progression of seepage induced internal instability this insight yields an improved characterization of suffusion and suffosion in cohesionless soils the progression of which appears gov erned by a critical combination of hydraulic gradient and effective stress resume des essais en permeametre ont eterealises sur quatre sols sans cohesion et agranulometrie etalee afin d etudier leur susceptibilitea l erosion interne les echantillons ont etereconstitues sous forme de pulpe saturee consolidee et en suite soumise aun ecoulement multi etapes sous un gradient hydraulique qui augmente l apparition de l instabiliteinterne est decrite de facon qualitative a partir d observations visuelles a travers la paroi du permeametre durant l essai ainsi que par des observations post essai l instabiliteinterne est aussi decrite quantitativement apartir des variations du gradient hydraulique al interieur des echantillons et du deplacement axial durant l essai les resultats offrent une vision nouvelle de la progression spatiale et temporelle de l instabiliteinterne causee par l infiltration ces resultats apportent une meil

modeling and analysis of internal tide generation and beamlike onshore propagation in the vicinity of shelfbreak canyons abstracta hydrostatic numerical model with alongshore uniform barotropic m2 tidal boundary forcing and idealized shelfbreak canyon bathymetries is used to study internal tide generation and onshore propagation a control simulation with mid atlantic bight representative bathymetry is supported by other simulations that serve to identify specific processes the canyons and adjacent slopes are transcritical in steepness with respect to m2 internal wave characteristics although the various canyons are symmetrical in structure barotropic to baroclinic energy conversion rates c are typically asymmetrical within them the resulting onshore propagating internal waves are the strongest along beams in the horizontal plane with the stronger beam in the control simulation lying on the side with higher c analysis of the simulation results suggests that the cross canyon asymmetrical c distributions are caused by multiple scattering effects on one canyon side slope because the phase variation in the spatially d

microbiotic crust control of runoff generation on sand dunes in the negev desert 1 the general belief that dune sands in arid regions are not likely to generate runoff and that runoff necessitates wet conditions is examined runoff generation was measured within an arid dune field in the western negev desert israel during 1990 1994 on 16 plots 1 2 6 6 m2 constructed along a continuum of crust covered crust the relationships between chlorophyll a and carbohydrates of the microbiotic crust and runoff yield were studied whereas chlorophyll a 15 45 mg m 2 and carbohydrates 4 9 17 6 g m 2 of the cyanobacterial crusts showed positive linear relationships with runoff coefficients a significant reduction in runoff yield was obtained once the moss dominated crust with 53 54 5 mg m 2 chlorophyll a and 28 5 28 9 g m 2 of carbohydrates which inhabited the wettest habitat within the dune field was also included in the analysis contrary to previous assumptions that an increase in runoff generation occurs on arid and semiarid sand dunes in wet climates wet climates may lead to the establishment of moss dominated crusts that in turn decrease runoff yield

statistics of internal tide bores and internal solitary waves observed on the inner continental shelf off point sal california abstractmoored observations of temperature and current were collected on the inner continental shelf off point sal california between 9 june and 8 august 2015 the measurements consist of 10 moorings in total 4 moorings each on the 50 and 30 m isobaths covering a 10 km along shelf distance and an across shelf section of moorings on the 50 40 30 and 20 m isobaths covering a 5 km distance energetic highly variable and strongly dissipating transient wave events termed internal tide bores and internal solitary waves isws dominate the records simple models of the bore and isw space time behavior are implemented as a temperature match filter to detect events and estimate wave packet parameters as a function of time and mooring position wave derived quantities include 1 group speed and direction 2 time of arrival time duration vertical displacement amplitude and waves per day and 3 energy density energy flux and propagation loss in total over 1000 bore events and over 9000 isw events

visualisation of seepage induced suffusion and suffosion within internally erodible granular media a rigid walled transparent soil permeameter has been developed to study visually the mechanisms occurring during seepage induced internal erosion in susceptible granular media under upward flow

internal tide generation at the continental shelf modeled using a modal decomposition two dimensional results abstract stratified flow over topography is studied with oceanic applications in mind a model is developed for a fluid with arbitrary vertical stratification and a free surface flowing over three dimensional topography of arbitrary size and steepness with background rotation in the linear hydrostatic regime the model uses an expansion of the flow fields in terms of a set of basis functions which efficiently capture the vertical dependence of the flow the horizontal structure may then be found by solving a set of coupled partial differential equations in two horizontal directions and time subject to simple boundary conditions in some cases these equations may be solved analytically but in general simple numerical procedures are required using this formulation the internal tide generated by a time periodic barotropic tidal flow over a continental shelf and slope is calculated in various idealized configurations the topography and fluid motion are taken to be independent of one coordinate di

particle transport characteristics and filtration of granitic residual soils from the korean peninsula weathered granitic residual soils which are found in much of the korean peninsula pose unique challenges in terms of internal stability and filtration the particle transport and filtration behavior of two extreme soil types named shinnae dong and poi dong are investigated in this paper the erodibilities of the two soils are evaluated using constant flow rate experiments on both undisturbed samples and samples with cylindrical holes a comparison of the results from these experiments revealed the extent of particle redeposition and self filtration in the internal erosion process in spite of the differences in the mineralogical properties and engineering characteristics of the two soils the size of the eroded particles from the two soils fell within the same range of 1 100 m the two soils were coupled with filters chosen according to the us bureau of reclamation s usbr filter criteria to determine the efficiency of filters in minimizing erosion it was found that the filters significantly mini

resonant amplification of subinertial tides in a submarine canyon 1 tidal oscillations dominate the flow field in many submarine canyons observations have shown that semidiurnal tidal energy in submarine canyons is significantly amplified with respect to adjacent shelves this amplification is thought to be caused by focusing of propagating internal tides incident from the open ocean or local in canyon generation on critical canyon floor slopes these mechanisms require freely propagating internal tides with superinertial frequencies we present results from a moored array in a canyon at 44 n where the observed velocities reached over 0 8 m s 1 the canyon flow field was highly unusual because it was dominated by the subinertial diurnal tide this occurred despite the fact that the barotropic tide was predominantly semidiurnal the diurnal tide was dramatically amplified in the canyon its velocities increasing toward the seafloor and canyon head the diurnal oscillations also exhibited marked modulation in time by the background barotropic forcing length scales suggest that the diurnal tide should be resonant in the canyon an analytical framework is used to explain the mechanisms behind the strong diurnal currents observed by the moored array in the model along shelf barotropic flow sets up a double kelvin wave response in the canyon generating along canyon velocities which are subsequently amplified by resonance the pattern of the model predictions is in excellent agreement with the observed velocity pattern

comparison of two criteria for internal stability of granular soil internal instability describes the loss of soil particles as a result of seepage two criteria are commonly used to determine the potential for such instability within a granular soil that is subje

predicting the saturated hydraulic conductivity of sand and gravel using effective diameter and void ratio this paper assesses methods to predict the saturated hydraulic conductivity k of clean sand and gravel currently in engineering the most widely used predictive methods are those of hazen and t

the applicability of microbially induced calcite precipitation micp for internal erosion control in gravel sand mixtures seepage induced internal erosion in earth filled embankment dams has been attracting the attention of civil engineering researchers and practitioners for decades microbially induced carbonate prec

capillary tube model for internal stability of cohesionless soil abstractkovacs criterion to assess the potential for internal instability of cohesionless soils that was proposed but never tested experimentally is verified with reference to a database of laboratory test results the inherent margin of safety is described and a threshold boundary between stable and potentially unstable gradations is established a variation on the method is then presented termed the simplified kovacs criterion

post erosion mechanical response of internally unstable soil of varying size and flow regime one of the leading causes of dam failure is internal erosion the impact of erosion of non plastic fine particles known as suffusion on the soil structure and strength has been studied experiment

algae influence the hydrophysical parameters of a sandy soil abstract article history received 2 august 2011received in revised form 31 january 2012accepted 3 february 2012available online xxxxkeywords algaebiological soil crustsoil water repellencysand dunesorptivityhydraulic conductivity biological soil crusts have a major effect on water ow in soils two study sites located at a pine forest gladecovered with a biologicalsoil crust formed the basis of our study the sand soil atthe surface glade soil wascompared to a control soil pure sand with limited impact of vegetation or organic matter occurring at50 cm depth beneath a glade area to assess the in uence ofalgae in the biological soil crust on the propertiesof pure sand a coccal green alga choricystis minor lamentous green alga klebsormidium subtile and stra menopile alga tribonema minus were isolated from the top layer of glade soil and grown in the lab in petridishes on sterile pure sand as monoalgal and bialgal c minor and k subtile crusts for 3 5 7 9 11 13 15 17 19 and 21 days atthe end ofeach growth stage the hydrophysicalparametersof crusted sand were estimat ed after drying at 50 c for 15 h equivalent to a 3 day hot spell and compared to the parameters of puresand the hydrophysical parameters were substantially different between the two surfaces the glade soilhad an index of water repellency about 18 times that of pure sand and the persistence of water repellencyalmost 54 times that of pure sand both sorptivity and hydraulic conductivity in the glade soil were about7 those of the pure sand respectively the growth of arti cial algal crusts characterized by an increase inorganic carbon content from 0 16 to 0 33 resulted in an increase in water drop penetration time of thedried crusts up to 14 times that of the pure sand and a decrease in the water sorptivity of the dried crustsup to 10 that of the pure sand whereas k subtile crusts both monoalgal and bialgal with c minor hadup to a 9 decrease in hydraulic conductivity compared to pure sand there was no impact of monoalgalc minor and t minus crusts on hydraulic conductivity k subtile was possibly limited to surface growth whereas c minor and t minus penetrated to depth consequently k subtile may have clogged the toppores more effectively than the other two strains the water repellency cessation time increased with anincrease in water drop penetration time for all the dried monoalgal and bialgal crusts used in this study agreater impact of k subtile on the shifts in hydraulic behaviour could in uence water capture and storage potentially decreasing evaporation during dry periods but enhancing overland ow diminishing leachingduring wet periods 2012 elsevier b v all rights reserved

flow and mixing in ascension a steep narrow canyon 1 a thin gash in the continental slope northwest of monterey bay ascension canyon is steep with sides and axis both strongly supercritical to m2 internal tides a hydrostatic model forced with eight tidal constituents shows no major sources feeding energy into the canyon but significant energy is exchanged between barotropic and baroclinic flows along the tops of the sides where slopes are critical average turbulent dissipation rates observed near spring tide during april are half as large as a two week average measured during august in monterey canyon owing to ascension s weaker stratification however its average diapycnal diffusivity 3 9 10 3 m2 s 1 exceeded the 2 5 10 3 m2 s 1 found in monterey most of the dissipation occurred near the bottom apparently associated with an internal bore and just below the rim where sustained cross canyon flow may have been generating lee waves or rotors the near bottom mixing decreased sharply around ascension s one bend as did vertically integrated baroclinic energy fluxes dissipation had a minor effect on energetics which were controlled by flux divergences and convergences and temporal changes in energy density in ascension the observed dissipation rate near spring tide was 2 1 times that predicted from a simulation using eight tidal constituents averaged over a fortnightly period the same observation was 1 5 times the average of an m2 only prediction in monterey the previous observed average was 4 9 times the average of an m2 only prediction

internal tides and mixing in a submarine canyon with time varying stratification abstractthe time variability of the energetics and turbulent dissipation of internal tides in the upper monterey submarine canyon msc is examined with three moored profilers and five adcp moorings spanning february april 2009 highly resolved time series of velocity energy and energy flux are all dominated by the semidiurnal internal tide and show pronounced spring neap cycles however the onset of springtime upwelling winds significantly alters the stratification during the record causing the thermocline depth to shoal from about 100 to 40 m the time variable stratification must be accounted for because it significantly affects the energy energy flux the vertical modal structures and the energy distribution among the modes the internal tide changes from a partly horizontally standing wave to a more freely propagating wave when the thermocline shoals suggesting more reflection from up canyon early in the observational record turbulence computed from thorpe scales is greatest in the bottom 5

the 2000 r m hardy lecture full scale hydraulic performance of soilbentonite and compacted clay liners the results of laboratory and in situ permeability tests can be used to predict the total leakage rate of a soil bentonite or clay liner this prediction however ignores the large influence that minor defects may have on the total leakage in quebec hundreds of municipal wastewater ponds have been filled with water to measure their total leakage rate before approval the design criteria and the equations to be used for the full scale performance test are briefly reviewed with their capacities to detect hydraulic deficiencies several case histories are presented to illustrate various problems excessive leakage of a stable soil bentonite mix washing of bentonite in a soil bentonite mix internal erosion of a natural clay liner through an inadequate sand filter and effects of freezing on the total leakage of a clay liner key words liner clay bentonite permeability performance full scale test

hydromechanical modeling of granular soils considering internal erosion this paper attempts to formulate a coupled practical model in the framework of continuum mechanics to evaluate the phenomenon of internal erosion and its consequences on the mechanical behavior of

barotropic and baroclinic m2 tides in the monterey bay region abstract a high resolution 250 m primitive equation model is used to simulate the depth averaged and baroclinic m2 tides in the monterey bay region the model shows a high level of skill in comparisons with sea level observations adcp current observations within the submarine canyon are reasonably well reproduced the modeled depth averaged currents have a complex spatial pattern with magnitudes in excess of 0 1 m s 1 near moss landing during the second half of flood ebb tide the flow is into out of the bay through the canyon but out of into the bay over the shelf regions this depth averaged flow pattern is not evident in a diagnostic run implying a feedback between the internal tides and the pressure gradient in the bay the depth integrated baroclinic total minus depth averaged energy fluxes show a complex beamlike pattern due to the interaction of energy from multiple sources the beams have magnitudes up to 1 kw m 1 interspersed with regions of near zero depth integrated flux energy en

turbulent kinetic energy dissipation in barrow canyon pacificwaterflowsacross theshallowchukchisea beforereachingthe arctic ocean where it isa sourceof heat freshwater nutrients and carbon a substantial portion of pacific water is routed through barrow canyon located in the northeast corner of the chukchi barrow canyon is a region of complex geometry and forcing where a variety of water masses have been observed to coexist these factors contribute to a dynamic physical environment with the potential for significant water mass transformation the measurements of turbulent kinetic energy dissipation presented here indicate diapycnal mixing is important in the upper canyon elevated dissipation rates were observed near the pycnocline effectively mixing winter and summer water masses as well as within the bottom boundary layer the slopes of shear stratification layers combined with analysis of rotary spectra suggest that near inertial wave activity may be important in modulating dissipation near the bottom because the canyon is known to be a hotspot of productivity with an active benthic community mixing may be an important factor in maintenance of the biological environment

internal tide generation and destruction by shoaling internal tides 1 internal tide generation is usually predicted from local topography surface tides and stratification however internal tides are often observed to be unrelated to local spring neap forcing appearing intermittently in 3 5 day bursts here we suggest a source of this intermittency by illustrating how remotely generated shoaling internal tides induce first order changes in local internal tide generation theory numerical simulations and observations show that pressure perturbations associated with shoaling internal tides can correlate with surface tide velocities to generate or destroy internal tides where shoaling internal tides have random phase such as on the new jersey slope time averaged internal tide generation is unaffected but instantaneous internal tide generation varies rapidly altering internal tide energy and possibly affecting nonlinear internal waves across shelf transport and mixing where shoaling internal tides are phase locked to the local surface tide such as in double ridge systems time averaged internal tide generation is affected and may result in resonance

assessing the potential of internal erosion and suffusion of granular soils this study presents a new empirical criterion for assessing the potential of internal erosion and suffusion of granular soils this method considers the bimodal structure of a soil having a primary coarse fabric and loose finer particles based on the porosities influenced by the particle size distribution and the degree of compaction by comparing the representative particle size of a loose finer fraction with the controlling constriction size of a primary coarse fabric a distinct boundary between internally stable and unstable soils with respect to internal erosion may be found

transition from partly standing to progressive internal tides in monterey submarine canyon monterey submarine canyon is a large sinuous canyon off the coast of california the upper reaches of which were the subject of an internal tide observational program using moored profilers and upward looking moored adcps the mooring observations measured a near surface stratification change in the upper canyon likely caused by a seasonal shift in the prevailing wind that favoured coastal upwelling this change in near surface stratification caused a transition in the behaviour of the internal tide in the upper canyon from a partly standing wave during pre upwelling conditions to a progressive wave during upwelling conditions using a numerical model we present evidence that either a partly standing or a progressive internal tide can be simulated in the canyon simply by changing the initial stratification conditions in accordance with the observations the mechanism driving the transition is a dependence of down canyon supercritical internal tide reflection from the canyon floor and walls on the depth of maximum stratification during pre upwelling conditions the main pycnocline extends down to 200 m below the canyon rim resulting in increased supercritical reflection of the up canyon propagating internal tide back down the canyon the large up canyon and smaller down canyon progressive waves are the two components of the partly standing wave during upwelling conditions the pycnocline shallows to the upper 50 m of the watercolumn above the canyon rim resulting in decreased supercritical reflection and allowing the up canyon progressive wave to dominate

observations on internal stability of cohesionless soils introduction internal stability refers to the ability of the coarser fraction of a soil to prevent migration of its finer fraction as a result of seepage flow skempton brogan 1994 report findings from piping tests on four well graded to gap graded sandy gravels flow was imposed in an upward direction without surcharge loading and without vibration an abrupt transition was noted from stable to unstable states defined by the ratio d9 15 d9 85 1 4 4 as postulated by kezdi 1979 and attributed to work published in 1969 the latter concept was conceived independently by de mello 1975 advocated by sherard 1979 for a ratio 4 to 5 and recommended by lowe 1988 for a ratio of 5 it involves splitting the gradation at arbitrary points along the curve to yield d9 15 of the coarse fraction and d9 85 of the fine fraction as illustrated in fig 1 for gradation g3 c in this study we further evaluate the kezdi 1979 criterion through laboratory permeameter testing of five soils fig 1 and table 1 and compare the results with a dataset of 34 gradations extracted from kenney lau 1985 1986 and honjo et al 1996

sources of baroclinic tidal energy in the gaoping submarine canyon off southwestern taiwan 1 a three dimensional model driven by tidal constituents o1 k1 m2 and s2 was adopted to evaluate the sources of baroclinic tidal energy in the gaoping submarine canyon gpsc off southwestern taiwan the model domain covered the probable primary generation sites including the luzon strait ls and the southeastern taiwan strait ts the simulated baroclinic tides agreed with the observations of tidal current velocity isotherm vertical displacement and baroclinic tidal energy flux fbc in the gpsc the depth integrated seven day averaged fbc computed from the model result was 2 2 kw m 1 in the gpsc and the corresponding area integrated fbc reached 189 4 mw the results obtained from the model suggest that the baroclinic tides lead to strong turbulent mixing near the canyon head with a vertical diffusivity of 3 5 10 3 m2 s 1 baroclinic tidal energy in the gpsc is mainly generated on the western ridge in the ls and on the steep topography in the southeastern ts the local generation of baroclinic energy only accounts for 4 4 of the total value the other 95 6 of the baroclinic tidal energy is remotely generated at the ls and the southeastern ts of which 31 9 and 8 8 are directly emanated respectively into the gpsc the northwestward and southeastward baroclinic energy beams radiating from the ls and the southeastern ts respectively meet each other and form internal partial standing tides outside the gpsc the transverse baroclinic energy from the internal partial standing tides accounts for the remaining 54 9 of the baroclinic tidal energy in the gpsc

experimental investigation of global backward erosion and suffusion of soils in embankment dams many embankment dams constructed with a core of nonplastic or very low plasticity silt sand gravel typically of glacial fluvioglacial or alluvial origin have experienced internal erosion this h

interference pattern and propagation of the m2 internal tide south of the hawaiian ridge abstract most of the m2 internal tide energy generated at the hawaiian ridge radiates away in modes 1 and 2 but direct observation of these propagating waves is complicated by the complexity of the bathymetry at the generation region and by the presence of interference patterns observations from satellite altimetry a tomographic array and the r p flip taken during the farfield program of the hawaiian ocean mixing experiment home are found to be in good agreement with the output of a high resolution primitive equation model simulating the generation and propagation of internal tides the model shows that different modes are generated with different amplitudes along complex topography multiple sources produce internal tides that sum constructively and destructively as they propagate the major generation sites can be identified using a simplified 2d idealized knife edge ridge model four line sources located on the hawaiian ridge reproduce the interference pattern of sea surface height and energy fl

closure to fabric and effective stress distribution in internally unstable soils by t shire c o sullivan k j hanley and r j fannin the authors have performed numerical tests to determine the distribution of fabric and effective stresses in internally unstable soils different grain size distribution curves as well as different densities were investigated the authors have used the methods of kezdi 1979 and kenney and lau 1985 1986 to assess the internal stability the relative density has a significant effect on the internal stability ahlinhan et al 2012 icold 2013 accordingly it is important to use a method takes into consideration the effect of density to assess the internal stability neither kezdi s method nor kenney and lau s method takes the density in consideration a suitable method is the one suggested by dallo et al 2013 which takes the effect of soil density in consideration for instance the soil gap med 18 is classified as border line according to kezdi s method whereas it is classified as unstable according to kenney and lau s method regardless of its relative density according to dallo et al 2013 soil gap med 18 is unstable transition or border line and stable for the loose medium and dense relative densities respectively also the internal stability prediction accuracy of dallo et al 2013 s method is better than those of the kezdi or kenney and lau methods dallo et al 2013 the discusser used the method of dallo et al 2013 to assess the internal stability of the gap graded soils tested by the authors table 1 it can be seen that the soils gap wide xx are unstable the soils gap narrow xx are stable whereas the internal stability of the soils gap med xx depends on the relative density of the soil another discussion point is related to the authors adoption of the findings of skempton and brogan 1994 that the critical finer fraction s falls between narrow limits of finer fractions by mass ffine 1 4 24 29 for dense and loose samples respectively also the finer fraction smax at which the finer particles completely separate the coarse particles from one another is given as ffine 1 4 35 the discusser believes that the critical finer fraction can be computed more accurately according to indraratna et al 2011 eq 1 or dallo and wang 2012 eq 2 as smax 1 4 1 nl 1 nc nc 1

numerical treatment of cross shelf open boundaries in a barotropic coastal ocean model abstract using a barotropic coastal ocean model with a straight coastline and uniform cross shelf bottom slope seven different cross shelf open boundary conditions four of which are applied in either implicit or explicit form are compared in three numerical experiments 1 a mound of water is allowed to collapse and radiate waves toward the open boundaries 2 a uniform alongshelf wind stress is applied at zero time over the entire shelf and held constant for the duration of the experiment 3 a uniform cross shelf wind stress is applied at zero time over the entire shelf and held constant for the duration of the experiment the boundary condition which is most transparent to waves consists of a sponge at the outer edge of the model domain with an orlanski radiation condition at the outer edge of the sponge several open boundary conditions perform adequately in the wind stress experiments but the orlanski radiation condition alone without a sponge appears to give the best total performance of thes

internal tides in monterey submarine canyon abstract the m2 internal tide in monterey submarine canyon is simulated using a modified version of the princeton ocean model most of the internal tide energy entering the canyon is generated to the south on sur slope and at the head of carmel canyon the internal tide is topographically steered around the large canyon meanders depth integrated baroclinic energy fluxes are up canyon and largest near the canyon axis up to 1 5 kw m 1 at the mouth of the upper canyon and increasing to over 4 kw m 1 around monterey and san gregorio meanders the up canyon energy flux is bottom intensified suggesting that topographic focusing occurs net along canyon energy flux decreases almost monotonically from 9 mw at the canyon mouth to 1 mw at gooseneck meander implying that high levels of internal tide dissipation occur the depth integrated energy flux across the 200 m isobath is order 10 w m 1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head where internal ti

propagation of low mode internal waves through the ocean abstract the baroclinic tides play a significant role in the energy budget of the abyssal ocean although the basic principles of generation and propagation are known a clear understanding of these phenomena in the complex ocean environment is only now emerging to advance this effort a ray model is developed that quantifies the effects of spatially variable topography stratification and planetary vorticity on the horizontal propagation of internal gravity modes the objective is to identify baroclinic shoals where wave energy is spatially concentrated and enhanced dissipation might be expected the model is then extended to investigate the propagation of internal waves through a barotropic mesoscale current field the refraction of tidally generated internal waves at the hawaiian ridge is examined using an ensemble of mesoscale background realizations derived from weekly ocean topography experiment topex poseidon altimetric measurements the path of mode 1 is only slightly affected by typical cur

internal tide convergence and mixing in a submarine canyon abstractobservations from eel canyon located on the north coast of california show that elevated turbulence in the full water column arises from the convergence of remotely generated internal wave energy the incoming semidiurnal and bottom trapped diurnal internal tides generate complex interference patterns the semidiurnal internal tide sets up a partly standing wave within the canyon due to reflection at the canyon head dissipating all of its energy within the canyon dissipation in the near bottom is associated with the diurnal trapped tide while midwater isopycnal shear and strain is associated with the semidiurnal tide dissipation is elevated up to 600 m off the bottom in contrast to observations over the flat continental shelf where dissipation occurs closer to the topography slope canyons are sinks for internal wave energy and may have important influences on the global distribution of tidally driven mixing

seismic precursor to instability induced by internal erosion in loose granular slopes fluidised landslides are one of the most dangerous types of mass movements as they can run over long distances at high velocity a flow like landslide can occur in both artificially designed and na

numerical simulation of internal tides and the resulting energetics within monterey bay and the surrounding area 1 we use a three dimensional nonhydrostatic unstructured grid code to simulate internal tides within monterey bay the predicted water surface barotropic and baroclinic velocities and internal tides in the greater coastal region agree with observations the agreement is due to the use of a high resolution mesh alongshore prescription of the barotropic m2 tidal velocities and specification of initial conditions consistent with field data results of depth integrated m2 period averaged energy flux and energy flux divergence are presented in order to identify locations of significant internal wave generation and dissipation based on the results there is a domain wide power surplus of 52 mw due to internal tides that is available for pelagic mixing yet isolated bathymetric features such as monterey submarine canyon and smooth ridge are net dissipative with dissipation rates of 8 3 and 1 5 mw respectively

particle size distribution of lunar soil meteorite impact on the lunar surface produces a consistent broadly graded soil in this note the geotechnical and geological systems are compared to characterize lunar soil in geotechnical terms the lunar soil particle size distribution is described as sandy silt silty sand well graded in geologic terms it is described as very fine sand very poorly sorted nearly symmetrical and mesokurtic because of its broad particle size distribution lunar soil may be internally erodible

internal tidal modal ray refraction and energy ducting in baroclinic gulf stream currents abstractupstream mean semidiurnal internal tidal energy flux has been found in the gulf stream in hydrodynamical model simulations of the atlantic ocean a major source of the energy in the simulat

diurnal and semidiurnal internal tide energy flux at a continental slope in the south china sea 1 barotropic surface and baroclinic internal tides were measured at four mooring sites during a field investigation of acoustic propagation characteristics and physical oceanography in the northern south china sea the mooring positions were in a line moving up the shallow portion of a continental slope at water depths between 350 and 85 m using time series of temperature and velocity at several depths 1 month series of semidiurnal and diurnal species internal tidal energy flux vectors were computed for three sites with a 14 day series computed for the fourth shallow site the internal tides had a temporal signature that was not in complete accord with the barotropic tides showing an enhancement of diurnal internal tides with respect to semidiurnal bathymetric slope barotropic tidal fluid particle trajectories and scale of generation site versus internal tide wavelength are investigated as possible causes of the differing response of the species

assessing the potential of internal instability and suffusion in embankment dams and their foundations suffusion is the process by which finer soil particles are moved through constrictions between larger soil particles by seepage forces soils susceptible to suffusion are described as internally unstable this technical note describes a method for assessing the potential of internal instability of silt sand gravel or clay silt sand gravel soils based on their particle size distribution based on laboratory tests carried out by the writers and results published by others it is shown that some commonly used methods are conservative for these soils

suffusion susceptibility investigation by energy based method and statistical analysis internal erosion is one of the main causes of instabilities within hydraulic earth structures four internal erosion processes can be distinguished and this study deals with the process of suffusi

on the use of the kozeny carman equation to predict the hydraulic conductivity of soils the saturated hydraulic conductivity of a soil can be predicted using empirical relationships capillary models statistical models and hydraulic radius theories a well known relationship between permeability and the properties of pores was proposed by kozeny and later modified by carman the resulting equation is largely known as the kozeny carman kc equation although the two authors never published together in the geotechnical literature there is a large consensus that the kc equation applies to sands but not to clays this view however is supported only by partial demonstration this paper evaluates the background and the validity of the kc equation using laboratory permeability tests test results were taken from publications that provided all of the information needed to make a prediction void ratio and either the measured specific surface for cohesive soils or the gradation curve for noncohesive soils the paper shows how to estimate the specific surface of a noncohesive soil from its g