Scaling and self‐similarity in one‐dimensional unsteady open channel flow

The conditions under which the Saint Venant equations system for unsteady open channel flow, as an initial–boundary value problem, becomes self‐similar are investigated by utilizing one‐parameter Lie group of point scaling transformations. One of the advantages of this methodology is that the self‐similarity conditions due to the initial and boundary conditions can also be investigated thoroughly in addition to the conditions due to the governing equation. The obtained self‐similarity conditions are compared with the scaling relationships that are derived through the Froude similitude. It is shown that the initial–boundary value problem of a one‐dimensional unsteady open channel flow process in a prototype domain can be self‐similar with that of several different scaled domains. However, the values of all the flow variables (at specified time and space) under different scaled domains can be upscaled to the same values in the prototype domain (at the corresponding time and space), as shown in this study. Distortion in scales of different space dimensions has been implemented extensively in physical hydraulic modelling, mainly because of cost, space and time limitations. Unlike the traditional approach, the distinction is made between the longitudinal–horizontal and transverse–horizontal length scales in this study. The scaled domain obtained by the proposed approach, when scaling ratios of channel width and water depth are equal, is particularly important for the similarity of flow characteristics in a cross‐section because the width‐to‐depth ratio and the inclination angles of the banks are conserved in a cross‐section. It is also shown that the scaling ratio of the roughness coefficient under distorted channel conditions depends on that of hydraulic radius and longitudinal length. The proposed scaling relations obtained by the Lie group scaling approach may provide additional spatial, temporal and economical flexibility in setting up physical hydraulic models. Copyright © 2013 John Wiley & Sons, Ltd.     

Automatic detection of near surface geological and hydrological features and investigating their influence on groundwater accumulation and salinity in southwest Egypt using remote sensing and GIS

This study employs two automated algorithms, the topographic fabric and the deterministic eight-node (D8), to reveal near surface geological fractures and their associated paleodrainages network from a 90?m DEM of the Shuttle Topographic Radar Mission sensor. The topographic fabric algorithm, which calculates the slope and aspect which define a vector normal to the earth’s surface and then compute direction cosines of normal vector at each point, was used to auto-detect fault zones. The deterministic eight-node (D8) algorithm, which determines in which neighbouring pixel any water in a central pixel will flow naturally, was used to delineate paleodrainages concealed beneath sand sheets. Seven sets of geological structures were recognized. Their major trends were found to be in the S46°W, S58°W, S81°W, N107°W, N–S, E–W and N152°W and share similar trends of the revealed paleodrainages. The results suggest a strong spatial relationship between the features extracted from DEM and groundwater potential.     

Influence of geomagnetic field on the motion of low satellites

The first aim of the present work is to compute a more accurate and recent model for the Earth’s magnetic field. The second aim is to determine the effects of the Earth’s magnetic field on the motion of a charged artificial satellite to evaluate the variations of the orbital elements of the satellite due to these effects. The magnetic field and its variation with time have been studied at different heights, longitudes and latitudes. The geomagnetic field is considered as a multiple potential field and the electrical charge of the satellite is assumed to be constant. A new computer code has been constructed to follow the components of the magnetic field in spherical harmonic models. The Gauss equations are solved numerically. The results concentrate on the computation of the numerical values of orbital perturbation for the case of a low Earth satellite. RS-1 satellite and space craft gravity probe B (GPB) are chosen as cases of studies for a detailed numerical analysis.     

Structural geologic control with the limestone bedrock associated with piling problems using remote sensing and GIS: a modified geomorphological method

Geotechnical engineering and unpredictable piling problems of highly urbanized areas underlain by intensive geological fracture zones require a better understanding of their spatial pattern and developments. Unlike traditional techniques which use geophysical survey and visual interpretation of optical satellite images, this study presents a modified approach to revealing the buried geological fractures in karst terrain, which incorporates Wood??s algorithm. The algorithm binary maps were modified by applying additional Soble filter with 10% threshold and equalization enhancement. These modifications have proven good discrimination for morphological linear and curvilinear derived from DEM. Results of the modified method were compared to the existing geological map and validated by conducting field observations. The analysis of the results and corresponding geological and topographical maps showed the effectiveness of the method to recognize the pattern of buried geological fractures. The results obtained demonstrated that maps of the modified method can be used as a reference map prior to any site investigation.     

Estimation of the 2D crustal velocity structure in the Hidaka and Iburi Subprefectures, Hokkaido, Japan

Applying the iterative shooting/bisection technique for rapid forward modeling to the seismic explosion data, we could refine the crustal velocity structure model of the western part of the Hidaka collision zone, Hokkaido, Japan. We used only the precise P-wave first arrival data obtained by the Research Group for Explosion Seismology, which set up a 113.4-km-long profile in August 2000 along with 327 observation points and four shot points with TNT charges from 100 to 300 kg. We could estimate a two-dimensional inhomogeneous crustal velocity structure model with a velocity decrease in the eastern direction at a depth of 15.7 km, several portions of velocity reversals with depth and a low velocity anomaly proposed in previous studies. The root-mean-square of travel-time residuals was improved from 0.398 s for the previous structure model to 0.176 s for the present model with a reduction of 55.8%.     

Flow–plant interactions at leaf,stem and shoot scales: drag,turbulence, and biomechanics

Flow–plant interactions are experimentally investigated at leaf, stem, and shoot scales in an open-channel flume at a range of Reynolds numbers. The experiments included measurements of instantaneous drag forces acting on leaves, stems, and shoots of the common freshwater plant species Glyceria fluitans, complemented with velocity measurements, high-resolution video recordings, and biomechanical tests of leaf and stem properties. The analyses of bulk statistics, power spectral densities, transfer functions, and cross-correlations of measured velocities and drag forces revealed that flow characteristics, drag force, and plant biomechanical and morphological properties are strongly interconnected and scale-dependent. The plant element–flow interactions can be subdivided into two classes: (I) passive interactions when the drag variability is due to the time variability of the wetted and frontal areas and squared approach velocity (due to the large-scale turbulence); and (II) active interactions representing a range of element-specific instabilities that depend on the element flexural rigidity and morphology. Implications of experimental findings for plant biophysics and ecology are briefly discussed.     

Relationship between geological structures and groundwater flow and groundwater salinity in Al Jaaw Plain,United Arab Emirates; mapping and analysis by means of remote sensing and GIS

Geological structures can be of great influence groundwater movement and accumulation in the surface and subsurface, and should therefore be taken into consideration in studies related to groundwater contamination impact. This study attempts to investigate the influence of geological structures on groundwater flow and groundwater salinity in Al Jaaw Plain, United Arab Emirates. A set of thematic maps derived from digital elevation model (DEM), LANDSAT, and Spaceborn Imagine Radar-C/X-Band Synthetic Aperture Radar were enhanced by applying Soble filter with 10 % threshold and equalization enhancement to reveal and map geological structures crosscut the entire region. Drainage pattern was derived from DEM automatically using D8 algorithm. The algorithm determines in which neighboring pixel any water in a central pixel will flow naturally. The trends of geological structures and drainage pattern extracted from remote sensing data were correlated with the spatial variation of hydraulic head, thickness aquifer, and groundwater salinity in the region. The results of the study reveal that the wadi courses, thickness of the aquifer, and topography are structural controlled by NNW–SSE, NE–SW, and ENE–WSW trending fault zones, significantly influencing the groundwater flow and groundwater contamination in Al Jaaw Plain.     

Review: Satellite-based remote sensing and geographic information systems and their application in the assessment of groundwater potential, with particular reference to India

Various hydrological, geological and geomorphological factors play a major role in the occurrence and movement of groundwater in different terrains. With advances in space technology and the advent of powerful personal computers, techniques for the assessment of groundwater potential have evolved, of which remote sensing (RS) and geographic information systems (GIS) are of great significance. The application of these methods is comprehensively reviewed with respect to the exploration and assessment of groundwater potential in consolidated and unconsolidated formations in semi-arid regions, and specifically in India. The process of such assessment includes the collection of remotely sensed data from suitable sensors and the selection of thematic maps on rainfall, geology, lithology, geomorphology, soil, land use/land cover, drainage patterns, slope and lineaments. The data are handled according to their significance with the assignment of appropriate weights and integrated into a sophisticated GIS environment. The requisite remote sensing and GIS data, in conjunction with necessary field investigations, help to identify the groundwater potential zones effectively.     

Signal reconstruction of surface waves on SASW measurement using Gaussian Derivative wavelet transform

Surface wave method consists of measurement and processing of the dispersive Rayleigh waves recorded from two or more vertical transducers. The dispersive phase data are inverted and the shear wave velocity versus depth is obtained. However, in case of residual soil, the reliable phase spectrum curve is difficult to be produced. Noises from nature and other human-made sources disturb the generated surface wave data. In this paper, a continuous wavelet transform based on mother wavelet of Gaussian Derivative was used to analyze seismic waves in different frequency and time. Time-frequency wavelet spectrum was employed to localize the interested seismic response spectrum of generated surface waves. It can also distinguish the fundamental mode of the surface wave from the higher modes of reflected body waves. The results presented in this paper showed that the wavelet analysis is able to determine reliable surface wave spectrum of sandy clayey residual soil.     

Middle Miocene ostracods from Wadi Sudr,westcentral Sinai,Egypt: systematic,biostratigraphy and palaeobiogeographic affinity with the Mediterranean realm

The investigation of the exposed middle Miocene strata from Wadi Sudr yielded well-preserved ostracod carapaces. Detailed taxonomic and paleontological studies led to the recognition of 36 ostracod species belonging to 25 genera, 4 species of them were considered new which fully described. Three assemblage biozones were recorded as follows: Actinocythereis spinosa–Actinocythereis hystrix zone, Chrysocythere cataphracta muricata-Cytheretta africana zone, and Disopontocypris schweijeri-Bythocypris tripolensis zone. The recorded biozones were calibrated with the previously studied middle Miocene planktonic foraminiferal biozones on the same samples and also correlated with the Miocene ostracod biozones from the neighboring countries. Our ostracod assemblages present in the lower and upper parts of the studied section (section II) indicated an inner neritic marine environment of moderate energy of currents and rapid sedimentation, while the assemblages in the middle part showed more deeper (outer neritic) environments with low energy of currents and low rate of sedimentation. The palaeobiogeographic distribution of the studied ostracods showed high affinity with the ostracod assemblages of the southern Mediterranean and moderate to low affinities with that of the northern and eastern Mediterranean respectively. The highly ornamented ostracod species with structures on the carapace were recorded from both Northern and Southern Mediterranean, while the smooth ones were found in the Southern Mediterranean only. The highly ornamented species are more widely distributed in both Southern and Northern Mediterranean than the smooth species. This may indicate that the ornamented species are more able to migrate than the smooth ones.