onset of scour below pipelines and self burial abstract this paper summarizes the results of an experimental study on the onset of scour below and self burial of pipelines in currents waves pressure was measured on the surface of a slightly buried pipe at two points one at the upstream side and the other at the downstream side of the pipe both in the sand bed the latter enabled the pressure gradient which drives a seepage flow underneath the pipe to be calculated the results indicated that the excessive seepage flow and the resulting piping are the major factor to cause the onset of scour below the pipeline the onset of scour occurred always locally but not along the length of the pipeline as a two dimensional process the critical condition corresponding to the onset of scour was determined both in the case of currents and in the case of waves once the scour breaks out it will propagate along the length of the pipeline scour holes being interrupted with stretches of soil span shoulders supporting the pipeline as the span shoulder gets shorter and shorter more and more weight of the pipeline is exerted on the soil in this process a critical point is reached where the bearing capacity of the soil is exceeded general shear failure at this point the pipe begins to sink at the span shoulder self burial it was found that the self burial depth is governed mainly by the keulegan carpenter number the time scale of the self burial process on the other hand is governed by the keulegan carpenter number and the shields parameter diagrams are given for the self burial depth and the time scale of the self burial process

the pretornadic phase of the goshen county wyoming supercell of 5 june 2009 intercepted by vortex2 part i evolution of kinematic and surface thermodynamic fields abstractthe authors analyze the pretornadic phase 2100 2148 utc tornadogenesis began at 2152 utc of the goshen county wyoming supercell of 5 june 2009 intercepted by the second verification of the origins of rotation in tornadoes experiment vortex2 the analysis relies on radar data from the weather surveillance radar 1988 doppler wsr 88d in cheyenne wyoming kcys and a pair of doppler on wheels dow radars mobile mesonet observations and mobile sounding observations the storm resembles supercells that have been observed in the past for example it develops a couplet of counter rotating vortices that straddle the hook echo within the rear flank outflow and are joined by arching vortex lines with the cyclonic vortex becoming increasingly dominant in the time leading up to tornadogenesis the outflow in the hook echo region where sampled has relatively small virtual potential temperature deficits during this stage of evolution a few kilometers upstream north of the location of maxim

paleostress and statistical analysis using quartz veins from mineralized and non mineralized zones application for exploration targeting abstract quartz vein orientations thickness and spacing data are analyzed from 10 transects each of mineralized and non mineralized zones of gadag region which is a gold bearing terrain within the dharwar craton southern india paleostress analysis reveals that the veins emplaced when fluid pressure pf varied from pf 2 intermediate principle stress to pf 2 to pf

composite vortex2 supercell environments from near storm soundings abstractthree dimensional composite analyses using 134 soundings from the second verification of the origins of rotation in tornadoes experiment vortex2 reveal the nature of near storm variability in the environments of supercell thunderstorms based upon the full analysis it appears that vertical wind shear increases as one approaches a supercell within the inflow sector providing favorable conditions for supercell maintenance and possibly tornado formation despite small amounts of low level cooling near the storm the seven analyzed tornadic supercells have a composite environment that is clearly more impressive in terms of widely used metrics than that of the five analyzed nontornadic supercells including more convective available potential energy cape more vertical wind shear higher boundary layer relative humidity and lower tropospheric horizontal vorticity that is more streamwise in the near storm inflow the widely used supercell composite parameter scp and significant tornado param

the pretornadic phase of the goshen county wyoming supercell of 5 june 2009 intercepted by vortex2 part ii intensification of low level rotation abstractthe dynamical processes responsible for the intensification of low level rotation prior to tornadogenesis are investigated in the goshen county wyoming supercell of 5 june 2009 intercepted by the second verification of the origins of rotation in tornadoes experiment vortex2 the circulation of material circuits that converge upon the low level mesocyclone is principally acquired along the southern periphery of the forward flank precipitation region which is a corridor characterized by a horizontal buoyancy gradient thus much of the circulation appears to have been baroclinically generated the descending reflectivity core drc documented in part i of this paper has an important modulating influence on the circulation of the material circuits a circuit that converges upon the low level mesocyclone center prior to the drc s arrival at low levels approximately the arrival of the 55 dbz reflectivity isosurface in this case loses some of its previously acquired circulation during the final f

tubular structures of northern wairarapa new zealand as possible examples of ancient fluid expulsion in an accretionary prism evidence from field and petrographical observations

simulated supercells in nontornadic and tornadic vortex2 environments abstractthe composite near storm environments of nontornadic and tornadic supercells sampled during the second verification of the origins of rotation in tornadoes experiment vortex2 both appear to be generally favorable for supercells and tornadoes it has not been clear whether small differences between the two environments e g more streamwise horizontal vorticity in the lowest few hundred meters above the ground in the tornadic composite are actually determinative of storms tornadic potential from the vortex2 composite environments simulations of a nontornadic and a tornadic supercell are used to investigate storm scale differences that ultimately favor tornadogenesis or tornadogenesis failure both environments produce strong supercells with robust midlevel mesocyclones and hook echoes though the tornadic supercell has a more intense low level updraft and develops a tornado like vortex exceeding the ef3 wind speed threshold in contrast the nontornadic supercell only produces shallow vortic

three dimensional characterization of a fractured granite and transport properties a three dimensional fracture network in a granite block is reconstructed from a series of experimental serial sections it is visualized and its most important geometrical characteristics are studied namely the orientation of the fractures the connectivity of the fractures the number of cycles per unit volume the distributions of surface areas and of the intersection lengths and the number of finite solid blocks isolated in the solid matrix by the network though the network mostly consists of two families of fractures it is interesting to note that a simple model of randomly oriented monodisperse hexagons often yields a good order of magnitude for the various geometrical properties which have been measured on the real block the flow properties are then studied examples of velocity field are provided as well as histograms of velocities the permeability tensor is determined and is found to be in good agreement with snow s formula finally dispersion is analyzed by means of a random walk method histograms of arrival times are provided and interpreted in terms of dispersion tensor

a simulation of the development of successive cells along a cold outflow boundary abstract a three dimensional numerical simulation is presented in which five new cells clouds develop in succession over a 4 h period the cells that develop have common characteristics including a lifetime of 40 min they form at 30 min intervals in a convergent region along the cold outflow boundary that is established by previous cells the propagation of the cloud system is several meters per second faster than individual cell movement due to the discrete development of new cells on the right flank of previous ones analysis of the simulation indicates that the most pronounced changes near the surface are due to downdraft development in contrast there is only a weak signature of new updraft development near the surface in the convergence field each new updraft develops along the cold outflow boundary which moves slowly away from the previous cell the air participating in the generation of a new cell appears to have originated 1 1 5 km below cloud base 2 6 km as the cell grows and rain begins

the regulation of tornado intensity by updraft width abstractstrong to violent tornadoes cause a disproportionate amount of damage in part because the width and length of a tornado damage track are correlated to tornado intensity as now estimated through enhanced fujita scale ratings the tendency expressed in the observational record is that the most intense tornadoes are often the widest herein the authors explore the simple hypothesis that wide intense tornadoes should form more readily out of wide rotating updrafts this hypothesis is based on an application of kelvin s circulation theorem which is used to argue that the large circulation associated with a wide intense tornado is more plausibly associated with a wide mesocyclone because a mesocyclone is strictly speaking a rotating updraft the mesocyclone width should increase with increasing updraft width a simple mathematical model that is quantified using observations of mesocyclones supports this hypothesis as do idealized numerical simulations of supercellular thunderstorms

ore controls in the charters towers goldfield ne australia constraints from geological geophysical and numerical analyses the approach taken in this paper namely synthesising a wealth of previous information with new data and a genetic model in combination with integrated numerical analyses led to new insights into the geological controls on the localisation of auriferous veins and residual prospectivity of the charters towers goldfield ne australia the method also has implications for the assessment of other mature goldfields worldwide despite a number of different ore controls having operated within the charters towers goldfield the controlling factors can be linked to a single genetic model for orogenic granitoid hosted lode gold mineralisation in a brittle deformation regime d4 of ne sw to nne ssw shortening under conditions of supralithostatic fluid pressure and low stress difference spatial autocorrelation results suggest district scale alignment of the auriferous veins parallel to and overlapping with the ese wnw to e w striking charters towers ravenswood lineament a major crustal boundary in the basement to the ravenswood batholith at the camp scale auriferous veins have abundance and proximity relationships with nw se nnw sse ne sw and ene wsw oriented lineaments suggesting that structures that controlled gold deposition in one camp did not necessarily control mineralisation in other camps fractal dimensions obtained with the box counting method range from 1 02 to 1 10 whereas veins in the charters towers city camp are characterised by a significantly higher fractal dimension of 1 28 this discrepancy may be taken to imply that most or all outcropping and near surface deposits within the charters towers city camp have been found and that new discoveries are more likely to occur at greater levels of depth or outside the boundaries of this camp the new understanding has implications for the assessment of the residual prospectivity of the charters towers goldfield where large areas of prospective rock types and structures e g approximately 40 of the charters towers ravenswood lineament are hidden under cover this parameter space was inaccessible to the historic prospectors and has received relatively little attention from recent explorers the following steps are suggested for the development of a targeting strategy for lode gold exploration in areas of the goldfield under cover 1 identify from geological and geophysical data the ene wsw 15 and nnw sse 15 striking structures and geological boundaries within a 20 km wide corridor parallel to and centred upon the charters towers ravenswood lineament the potential control on gold deposit distribution at the regional to district scale 2 interpret from geological and geophysical data the distribution of pre middle devonian granitoids within these areas that are the preferred host rocks of the payable gold deposits 3 deduce from geophysical data the ene wsw 15 and nnw sse 15 striking structures that cut or bound the intrusions identified in step 2 4 locate segments along the structures identified in step 3 that deviate most from the geometry of a straight line e g potential bends or splays and or intersect other structures or geological contacts or both and 5 define and rank potential targets within the prospective areas identified in step 4 and systematically test the best ones

geometry percolation and transport properties of fracture networks derived from line data summary in most geological instances 2 d or 3 d fracture distributions are not available from field data we show here that when data relative to fractures are collected along a line such as a road or a well estimations can be given to the major geometrical properties of the corresponding fracture networks such as the volumetric density of fractures their percolation character and their macroscopic permeability all these formulae are analytical and can be split into two parts the first one can be derived from the measured data while the second one requires some assumption on the lateral extension of the fractures and on their permeability all these techniques are applied to fractures located in the baget watershed they are also validated on a granite block whose structure is fully known extensions are proposed for networks with variable permeabilities and polydisperse fractures

the relationship of the degree of interconnection to permeability in fracture networks the problem of determining the permeability of a rock mass containing a system of finite fractures is highly dependent on both the degree of interconnection between fractures and the heterogeneity of individual fracture characteristics this paper examines how degree of interconnection affects both magnitude and nature of the fracture permeability the interconnection between given fracture sets is a complex function of 1 fracture density i e the number of fractures per unit volume and 2 the fracture extent or size unfortunately neither the density nor the extent of fractures is easily determined from borehole data however fracture frequency can be directly measured in a borehole because it is simply the number of fractures intersected per unit length of the borehole the frequency is a measure of the product of fracture density and size because the probability of a fracture intersecting a borehole is proportional to this product the effect of the degree of interconnection was investigated by numerically simulating flow in fracture networks where fracture size and density varied inversely while the product of these two parameters was held fixed directional permeabilities of a number of such networks were determined and the hydraulic behavior of each fracture system was compared to that of an ideal porous medium the permeability of the rock matrix between the fractures was assumed to be low enough to be negligible the results show that as fracture length increases the degree of interconnection increases thus for a given fracture frequency as measured in a borehole the permeability of the system increases as fracture length is increased and density is proportionally decreased also fracture systems with shorter but more dense fractures behave less like porous media than do systems with longer but less dense fractures knowledge of fracture frequency and orientation alone is inadequate when determining permeability or deciding the important question of whether a given system behaves like a porous medium for many cases where these parameters can be measured in the borehole it is critical to know fracture length in order to predict the degree of fracture network interconnection however for certain cases where fractures are larger than some critical size it may not be necessary to know fracture lengths exactly

linear and nonlinear propagation of supercell storms abstract a nonlinear formula for updraft motion in supercell storms is derived from petterssen s formula for the motion of systems and the vertical equation of motion and tested on form preserving disturbances at each level continuous propagation of an updraft maximum is determined largely by the horizontal gradient of the nonhydrostatic vertical pressure gradient force nhvpgf at the updraft center the nhvpgf is deduced from the formal solution of the poisson equation for nonhydrostatic pressure in anelastic flow subject to homogeneous neumann boundary conditions at the ground and top boundary recourse also is made to published fields of partitioned vertical pressure gradient force updraft motion is partitioned into parts forced by horizontal gradients of hydrostatic pressure linear interaction between the environmental shear and updraft and nonlinear dynamical effects the dynamics of supercell storms for nearly straight and highly curved hodographs are found to be different nonlinear rotation

numerical model for local scour under offshore pipelines a numerical model based on potential flow theory is proposed for simulating the equilibrium scour hole formed by unidirectional flow underneath offshore pipelines the model employs a finite difference method to solve the laplace equation in terms of velocity potential in a curvilinear coordinate system a boundary adjustment technique based on the newton raphson method is used to calculate the free boundary formed by the eroded seabed by means of the equilibrium of all forces acting on a sediment particle on a sloping bed because the solution of flow field and adjustment of the seabed topography are carried out in an iterative manner the model takes into account the interactions between the flow pipe and the seabed the comparison of the present model with empirical formulas on the prediction of the maximum scour depth indicates that the present model is useful for approximate estimation of scour depth at a pipeline on the seabed for the case of clear water scour

geometrical and fractal analysis of a three dimensional hydrothermal vein network in a fractured granite abstract a three dimensional study of a fracture network has been performed on a 0 66 m 3 block of fine grained granite from la peyratte deux sevres france the block was sawn in nine parallel plates the fractures associated with altered haloes were mapped for each plate using a photographic method the nine fracture sets were subjected to an analysis of the percolated network based on a measurement of the width of altered haloes developed around fractures hydrothermal alteration is created by circulation of a certain amount of fluid flow in the rock we assume that the alteration zone width is proportional to fluid mass flow the width of alteration zones will give a good idea of the path preferentially followed by fluids the relation between fracture length and width of the alteration zone shows that the total fracture network consists in fact of two sorts the largest fractures surface 0 1 m 2 create a loose and poorly interconnected pattern in the block however they have developed wide alteration zones 3 mm and have then had a great role in fluid conduction they represent only 10 of the fractures but are responsible for 47 of alteration in volume approximately 80 of these fractures with wide alteration zones are oriented in the same direction this main network is linked to a more dense highly interconnected system made of shorter fractures with narrower altered zones fractal analysis has also been performed on pictures of the fracture patterns using the linear cantor s dust method fractal dimension values d indicate an anisotropy of fracture distribution on each plane moreover when the planes are compared to one another in succession variations of d values can be noticed indicating an inhomogeneity in the third dimension the study of such a three dimensional fracture set shows that fluids follow preferential paths within a fracture network and helps the understanding of fracture distribution

how does micropetrography help us to understand the permeability and poromechanical behaviour of a rock many poromechanical studies of rocks give little regard to the micropetrographic observation of their constituents the aim of this study is to show how such a detailed study can help understand and provide more precision on the poromechanical behaviour of the material the rock studied here is an oolitic limestone micropetrography reveals the nature of the constituents calcite mostly in the form of fine grained micrite their abundance their organization micrite organized in ooids linked by a calcitic cement small sized highly connected isotropic porosity scarce unconnected porosity and the structure of the rock global isotropy small heterogeneities due to sedimentological phenomena no microcracks micropetrography completes the information obtained by poromechanics in that it allows the observation of elements deduced from macroscopical tests the aim of this paper is to show the effect of microporosity on permeability and flow in a rock where microporous grains are in contact with each other

tornadogenesis in a high resolution simulation of the 8 may 2003 oklahoma city supercell abstracta 50 m grid spacing advanced regional prediction system arps simulation of the 8 may 2003 oklahoma city tornadic supercell is examined a 40 min forecast run on the 50 m grid produces two f3 intensity tornadoes that track within 10 km of the location of the observed long track f4 intensity tornado the development of both simulated tornadoes is analyzed to determine the processes responsible for tornadogenesis trajectory based analyses of vorticity components and their time evolution reveal that tilting of low level frictionally generated horizontal vorticity plays a dominant role in the development of vertical vorticity near the ground this result represents the first time that such a mechanism has been shown to be important for generating near surface vertical vorticity leading to tornadogenesis a sensitivity simulation run with surface drag turned off was found to be considerably different from the simulation with drag included a tornado still developed in the no drag simulation but it was

a preliminary polarimetric radar comparison of pretornadic and nontornadic supercell storms abstractsupercell thunderstorms produce a variety of hazards including tornadoes a supercell will often exist for some time prior to producing a tornado while other supercells never become torna

application of cantor s method for fractal analysis of fractures in the toyoha mine hokkaido japan cantor s method has been used for fractal analysis of fractures in the toyoha mine hokkaido japan the analyses were performed on a two dimensional area ranging from 30 cm2 to 220 km2 cantor s analysis predicts the probability of fracture occurrence in rocks in a given distance the probability of finding a fractured zone of length x is given by p x d where d is the fractal dimension in the toyoha mine the samples collected in sugo and izumo veins are characterized by d values of 0 25 and 0 10 0 24 respectively the distribution of fractures in galleries 200 m long is very similar d 0 17 at a kilometer scale the disposition of veins varies according to the directions of observation d 0 20 e w and 0 25 0 28 nw se at a larger scale landsat map the fault distribution appears very similar in all directions 0 22 d 0 25 in the vicinity of the toyoha mine the fracture disposition is fractal at all scales of observation despite a scale factor that can vary by 106 the distribution of fractures remains fractal with similar fractal numbers average d 0 25 moreover d values gradually change according to the distance from the toyoha mine suggesting that the type of rupture and consequently the nature of stress are different far from the toyoha mine

three dimensional scour below offshore pipelines in steady currents this paper presents the results of an experimental investigation on three dimensional scour below offshore pipelines subject to steady currents the major emphasis of the investigation is on the scour propagation velocity along the pipeline after the scour initiation physical experiments were conducted to quantify the effects of various parameters on scour propagation velocity along the pipeline in a water flume of 4 m wide 2 5 m deep and 50 m long local scour depths directly below the model pipeline were measured using specifically developed conductivity scour probes effects of various parameters such as pipeline embedment depth incoming flow shields parameter and flow incident angle relative to the pipeline on scour propagation velocity along the pipeline were investigated it was found that scour propagation velocity generally increases with the increase of shields parameter but decreases with the increase of the pipeline embedment depth a general predictive formula for scour propagation velocity is proposed and validated against the experimental results

fractal and multifractal measures of natural and synthetic fracture networks we have analyzed the fractal and multifractal nature of a series of 17 natural fracture trace maps representing a wide variety of scales geological settings and lithologies as well as a number of typical synthetic fracture networks in which fracture locations orientations and lengths are drawn from various probability distribution functions recent studies have shown that multifractal methods can be used to investigate fracture networks at greater depth since the fractal dimension represents only part of the scaling spectrum characterizing each network we find that the real and synthetic fracture maps display fractal and multifractal properties moreover the properties of the synthetic networks are very similar to those of the real networks with nontrivial fractal dimensions and multifractal spectra we suggest that different fracturing mechanisms can lead to two or more distinct subranges over which a fractal dimension can be defined while the heterogeneity of the rock and the nature of the fracturing mechanisms lead to multifractal properties we also find that the fractal dimension of a synthetic fracture network is relatively insensitive to parameters such as fracture length and orientation but can be controlled by appropriate choice of the relative fracture density

numerical modeling of flow and scour below a pipeline in currents part ii scour simulation abstract a vertical two dimensional 2d numerical model for time dependent local scour below offshore pipelines subject to unidirectional steady flow is developed the governing equations for the flow and sediment transport are solved by using finite difference method in a general curvilinear coordinate system the performance of two turbulence models the standard k model and smagorinsky subgrid scale sgs model on modeling time dependent scour processes is examined both suspended load and bed load are considered in the scour model the suspended load model is verified against two channel sediment transport cases the change of bed level is calculated from the continuity equation of total sediment transport a new time marching scheme and a sand slide scheme are proposed for the scour calculation it is found that the proposed time marching scheme and sand slide model work well for both clear water and live bed scour situations and the standard k turbulence closure is more preferable than the sgs model in the 2d scour model developed in this study

fractal patterns of fractures in granites abstract fractal measurements using the cantor s dust method in a linear one dimensional analysis mode were made on the fracture patterns revealed on two dimensional planar surfaces in four granites this method allows one to conclude that 1 the fracture systems seen on two dimensional surfaces in granites are consistent with the part of fractal theory that predicts a repetition of patterns on different scales of observation self similarity fractal analysis gives essentially the same values of d on the scale of kilometres metres and centimetres five orders of magnitude using mapped surface fracture patterns in a sierra nevada granite batholith mt abbot quadrangle calif 2 fractures show the same fractal values at different depths in a given batholith mapped fractures main stage ore veins at three mining levels over a 700 m depth interval of the boulder batholith butte mont show the same fractal values although the fracture disposition appears to be different at different levels 3 different sets of fracture planes in a granite batholith central france and in experimental deformation can have different fractal values in these examples shear and tension modes have the same fractal values while compressional fractures follow a different fractal mode of failure the composite fracture patterns are also fractal but with a different median fractal value compared to the individual values for the fracture plane sets these observations indicate that the fractal method can possibly be used to distinguish fractures of different origins in a complex system it is concluded that granites fracture in a fractal manner which can be followed at many scales it appears that fracture planes of different origins can be characterized using linear fractal analysis

reexamining the vertical development of tornadic vortex signatures in supercells abstractobservations from a hybrid phased array doppler radar the mobile weather radar 2005 x band phased array mwr 05xp were used to investigate the vertical development of tornadic vortex signatures tvss during supercell tornadogenesis data with volumetric update times of 10 s an order of magnitude better than that of most other mobile doppler radars were obtained up to storm midlevels during the formation of three tornadoes it is found that tvss formed upward with time during tornadogenesis for two cases in a third case missing low level data prevented a complete time height analysis of tvs development however tvs formation occurred first near the ground and then at storm midlevels several minutes later these results are consistent with the small number of volumetric mobile doppler radar tornadogenesis cases from the past 10 years but counter to studies prior to that in which a descending tvs was observed in roughly half of tornado cases utilizing weather surveillance radar 1988 do

scaling and geometric properties of extensional fracture systems in the proterozoic basement of yemen tectonic interpretation and fluid flow implications abstract multi scale mappings of fracture systems in the crystalline basement of yemen are presented fracture datasets are described through statistical analyses of direction length spacing density and spatial distribution results are combined with field observations and can be directly used to model the geometry of the fracture networks in analog basement rocks from multi kilometric to decametric scales the fractured reservoir analog is defined with a dual porosity model in which tectonic and joint systems correspond to the basement reservoir backbone and matrix respectively these two end members reveal contrasting geometrical reservoir and scaling properties in tectonic systems multi scale geometries are self similar the fracture network shows fractal behavior power law length distribution and clustered spacing and fault zones show hierarchical organization of geometrical parameters such as length thickness and spacing in joint systems the fracture network is scale dependent with exponential length distribution and shows anti clustered spacing however these two end members have both well connected properties with fault zones acting as main drain and joint systems acting as the fluid supply

thickness and spatial distribution of veins in a porphyry copper deposit rosia poieni romania abstract a statistical analysis of the vein thickness distributions of veins in the rosia poieni porphyry copper deposit romania indicates that vein thickness data conform to a power law distribution whereas the spatial distribution of veins follows a negative exponential law a high clustering of the veins is indicated by both the spacing distribution and the cv values the similar vein densities observed at the open pit scale are representative of a saturation level of vein nucleation differences in the spacing distribution and in the mean vein thickness are explained by different initial nucleation rates in the deepest and the lowest parts of the porphyry copper the highly clustered organization of the system is explained by vein linkage processes during their growth and modification of the fluid pressure and local stress during the hydrofracturing

fractal analysis of fractures applied to soultz sous forets hot dry rock geothermal program abstract a fractal analysis has been performed on a fracture set observed on granite cores in order to determine preferential paths for fluids injected during hot dry rock hdr geothermic experiments this analysis was based on the sorting of fractures on criteria such as their direction according to the present stress field their dip their hydrothermal filling thickness vein width which is linked to the intensity of alteration and thus to the physico chemical properties of the surrounding rock the results show a global increase of the fractal dimension d with depth which may be related to the lithostatic pressure gradient analysis of the total fracture set has showed zones in which fractures are clustered low d values while others are characterized by regularly spaced fractures higher d values fractures parallel to the maximum horizontal stress narrow veins and fractures with a dip greater than 40 represent 35 to 79 of the total fracture set their fractal dimensions are similar to those of the total fracture set large veins linked with high porosity zones show a cluster pattern all along the drilling in the context of hdr geothermics one should seek highly fractured zones especially if the fractures they contain are clustered and if they have developed wide alteration zones linked to a high porosity these conditions may optimize the hdr heat exchanger possibilities

the influence of environmental low level shear and cold pools on tornadogenesis insights from idealized simulations abstractidealized dry simulations are used to investigate the roles of environmental vertical wind shear and baroclinic vorticity generation in the development of near surface vortices in supercell like pseudostorms a cyclonically rotating updraft is produced by a stationary cylindrical heat source imposed within a horizontally homogeneous environment containing streamwise vorticity once a nearly steady state is achieved a heat sink which emulates the effects of latent cooling associated with precipitation is activated on the northeastern flank of the updraft at low levels cool outflow emanating from the heat sink spreads beneath the updraft and leads to the development of near surface vertical vorticity via the baroclinic mechanism as has been diagnosed or inferred in actual supercells that have been simulated and observed an intense cyclonic vortex forms in the simulations in which the environmental low level wind shear is strong and the heat sink is of intermediate strength relative to the

fractal analysis of fractures in rocks the cantor s dust method abstract the cantor s dust method of fractal analysis has been used to describe the regularity of fracture patterns in geological materials seen on a two dimensional surface this linear method of analysis is well adapted to a determination of two dimensional phenomena the determination of the fractal dimension d indicates that it varies regularly as a function of the orientation of the analysis direction this is taken to indicate that there is a relation unexplained as yet between the regularity of the fracture pattern and the forces which produced it the use of the cantor s dust method on naturally fractured materials ranging in dimension from 3 mm to 45 m in maximum dimension indicates the fractal nature of the fractures found in natural materials the analysis method can also be used to identify local variations in the stress field which caused failure such as the fractures in a feldspar compared to those in the host granite etc the method appears to be a sensitive descriptive measure of the failure patterns in rocks

numerical modeling of flow and scour at pipelines a numerical model for the description of fluid flow and suspended and bed load sediment transport is presented density effects are included in the momentum reynolds equations and in the turbulence kappa and epsilon equations changes in bed levels are calculated from sediment continuity and the finite element grid is adapted to the geometry the reynolds equations and the transport equation for suspended sediment are solved numerically using a taylor galerkin finite element method the flow at a surface mounted cylinder in a steady flow is predicted in good agreement with experiments periodic vortex shedding from a cylinder placed above a rigid bed is predicted in good agreement with laboratory experiments provided that sufficiently detailed grids approximately 5 000 nodes are used scour calculations are performed for a cylinder in a steady flow with its underside placed at the level of the original flat bed predicted scour at a pipeline in steady flow is in good agreement with laboratory measurements reported in the literature

evolution of permeability in sand injectite systems abstract sand injectite complexes comprise kilometer scale clastic intrusion networks that act as effective conduits for the migration accumulation and then recovery of hydrocarbons and other fluids an equivalent continuum model is constructed to represent a sand injectite reservoir coupling stress and fluid flow in fractured rock using the continuum simulator toughreact coupled with flac3d to follow deformation and fluid flow a permeability model which uses staged percolation models is proposed to improve permeability estimation of fracture networks by accommodating four different levels of fracture connectivity this permeability model is confirmed against field and laboratory data corresponding to the different connectivities of fracture networks the new constitutive permeability model is incorporated into the coupled hydro mechanical simulator framework and applied to sand injectites with the analysis of permeability evolution mechanisms and mechanical sensitivity the results indicate that when the magnitudes of principal stresses increase in a constant ratio normal closure is the dominant mechanism in reducing fracture aperture and thereby permeability conversely the evolution of stress difference can accentuate aperture and permeability due to an increase in shear dilation for critically or near critically oriented fractures also the evolution of aperture and related permeability of fractured rock are more sensitive at lower stress states than at higher stress states due to the hyperbolic relationship between normal stress and normal closure of the fractures