Bottom Ridge Research Articles

Variations in Flow Patterns in the Northern Taiwan Strait Observed by Satellite-Tracked Drifters

This study investigates the variations in flow patterns in the northern Taiwan Strait in summer using high-frequency (HF) radar measurements, satellite-tracked drifter trajectories and numerical models. There is an obvious interaction between intra-diurnal tides and ocean currents in northwestern Taiwan. When the tide changes between high tide and low tide, the change in direction of the nearshore flow occurs before the change in the offshore flow. Drifter trajectories show that there are three different drifting paths in the Taiwan Strait in summer. One path is along the west coast of Taiwan from the southwest coast to the northeast coast. Another path is the same as the first one but leads northward to the East China Sea instead of eastward to the northeast coast of Taiwan. The other path exists along the west coast of Taiwan, some distance out, after being deflected by the bottom ridge. The regional ocean modeling system model was used in this study to clarify the influencing factors that lead to these three paths. The results of multiple simulations and HF radar data indicate that the bifurcation of the first two drift paths in northwestern Taiwan is caused by ebb and flood tide transitions. The different routes of the latter two paths are due to the significant speed difference between the nearshore current and the offshore current approximately 45 km from the coast.

Indigenous Knowledge Assessment on Irrigation Water Management Practices

Indigenous knowledge is the local or traditional knowledge system used by farmers. Therefore indigenous knowledge on irrigation water management means using of local or traditional knowledge system to manage irrigation water. This study was aimed to investigate farmers’ current irrigation water management practice and their technical performance. In this study I used reconnaissance survey and observation were carried out with each implementing center and Woreda Bureau of Agriculture to obtain overview of different irrigation schemes and irrigation practice conditions. The collected qualitative and quantitative data both from primary and secondary sources were analyzed using appropriated statistical methods like SPSS. The study result showed that farmers have developed several indigenous knowledge of irrigation water management practices. Among these knowledge, most of farmers in both weredas use furrow irrigation method, farmers use soil moisture method and crop leaf wilt techniques to irrigate cropped land, Most farmers apply irrigation water at morning and night time, The respondents uses watering top ridge to determine irrigation water sufficient and watering bottom ridge and slow stream flow for irrigation water insufficient.

The Effect of Interlayer on Water Cut Rise in a Bottom Water Reservoir

A bottom water reservoir is universal in all reservoirs in the world. In the exploitation process of the bottom water reservoir, because the reservoir is in complete contact with bottom water, the natural energy supply of the bottom water reservoir is sufficient. At the same time, in the production process, the pressure drop generated by the formation is mainly concentrated near the wellbore, which leads to a short period of waterless oil production, fast water breakthrough, and fast water cut rise, which seriously affects the overall recovery factor and increases the risk of oil filed exploitation. Since the distribution of an interlayer enhances the heterogeneity of the reservoir, it has a prominent impact on the flow of oil and water in the bottom water reservoir. However, people know little about the impact of the interlayer on the bottom water reservoir. In this paper, the mathematical model of two-phase flow in the bottom water reservoir with the interlayer is proposed, and the numerical solution of the model is obtained by a finite element method. The influence of the distribution of the interlayer on the water cut rising law of the bottom water reservoir is analyzed. The results show that the bottom water is blocked by the interlayer and its own gravity and the rising height of the bottom water is limited, so that the interlayer has a significant inhibitory effect on the coning of the bottom water. The closer the interlayer is to the oil-water interface, the faster the water cut will rise; the narrower the interlayer is, the faster the bottom water ridge will advance; when the width of the interlayer is the same as that of the reservoir, the water cone will not appear; the higher the permeability of the interlayer is, the faster the upper body of the water cut will be; when the permeability of the reservoir and the interlayer is over 1000, the influence of the interlayer on the water cut rise is not obvious; the thickness of the interlayer on the water cut rise law has little effect. Finally, through the case analysis, it is proposed that the new horizontal wells should be arranged in the position where the interlayer develops. The findings of this study can help for the better understanding of control laws of the interlayer on the bottom water and providing a crucial theoretical basis for the development of the bottom water reservoir.

Controlled Scaffold Platform Designs on Nasopharyngeal Carcinoma Cell Separation

Nasopharyngeal carcinoma (NPC) is a highly invasive and metastatic disease occurring in the nasopharynx. For early diagnosis or treatment, it is helpful to separate invasive nasopharyngeal carcinoma (NPC43) cells from epithelial (NP460) cells. However, the lack of proper in vivo models significantly hinders the systematic study of NPC. In this study, an in vitro two-layer scaffold platform was developed to mimic the extracellular matrix of the tissue that allows the investigation of carcinoma and epithelial cell migration behaviors. Three precisely controlled factors were designed to investigate how topographic cues affected migration of NP460 and NPC43 cells: overlay angles between the top and bottom layers, top layer thicknesses, and surface topography of the bottom layer ridges. These designs offered different surface contact areas for cells to probe and form focal adhesions as they migrated on the platforms. As NP460 and NPC43 cells respond differently to the surrounding microenvironments, when the top layers were perpendicular to the bottom layers, 66.3% NPC43 cells could move into the $10~\mu \text{m}$ wide trenches compared to 5.5% for NP460 cells. However, NP460 and NPC43 cells migrating into top layer trenches were hindered when the top layer was too shallow or too thick. Moreover, the gratings added on the bottom layer ridges promoted cells to squeeze into the trenches. These results yielded over 92.3% separation efficiency on platforms with a 15- $\mu \text{m}$ thick top layer being perpendicular to the bottom layer and gratings on the bottom layer ridges.

Influence of Design and Technological Parameters of Disk Working Bodies on the Height of the Crest of the Bottom of the Furrow

Disks are one of the most common tillage working bodies used both on independent machines and tools, and as part of combined aggregates. Compliance with agrotechnical requirements is a necessary condition for improving the technological efficiency of the disk working bodies. The height of the furrow bottom ridge depends on a number of design and technological parameters of adjacent disks, as well as the distance between them. In the article, analytical expressions are obtained that allow us to describe the relationship between the height of furrow bottom ridge formed between the projections of cutting edges of adjacent disks, structural and technological parameters, and a given orientation scheme.

Baroclinic Modes over Rough Bathymetry and the Surface Deformation Radius

AbstractThe deformation radius is widely used as an indication of the eddy length scale at different latitudes. The radius is usually calculated assuming a flat ocean bottom. However, bathymetry alters the baroclinic modes and hence their deformation radii. In a linear quasigeostrophic two-layer model with realistic parameters, the deep flow for a 100-km wave approaches zero with a bottom ridge roughly 10 m high, leaving a baroclinic mode that is mostly surface trapped. This is in line with published current meter studies showing a primary EOF that is surface intensified and has nearly zero flow at the bottom. The deformation radius associated with this “surface mode” is significantly larger than that of the flat bottom baroclinic mode. Using World Ocean Atlas data, the surface radius is found to be 20%–50% larger over much of the globe, and 100% larger in some regions. This in turn alters the long Rossby wave speed, which is shown to be 1.5–2 times faster than over a flat bottom. In addition, the larger deformation radius is easier to resolve in ocean models.

Hypothesis on the Formation of Baer’s Mounds by Nonlinear Waves upon a Sudden Drop in the Level of the Caspian Sea

It is shown experimentally that upon a rapid draining of water within a basin, the Froude number quickly reaches its maximum and then remains virtually constant. Stationary long three-dimensional waves that arise on the water’s surface form bottom ridges, the distance between which is equal to the length of the waves. It is established that ridges on the shores of the northern part of the Caspian Sea (Baer’s Mounds) could have been formed by three-dimensional waves upon a sudden drop in the level of the Caspian Sea.

Application of binary compound water control technology in the development of horizontal wells in offshore oil fields

Offshore A oil field is a typical bottom water reservoir with thin thickness of oil layer and large thickness ratio of water layer and oil layer. Due to its strong bottom water energy, serious non-homogenous and the impact of the bottom ridge, most of the horizontal well production segment is seriously water out.Based on interaction relationship between horizontal segment trajectory and oil and-water interface, the distribution and contrast of permeability along horizontal segment and the comprehensive analysis of production performance, this paper combines the characteristics of the residual oil distribution of typical wells and the mechanism of dual compound oil addition, and from the perspective of combining theory with the field creatively put forward the dual composite water control mode of first injecting gel segment plug and then injecting foam. then completed the design of dual compound water control mode and dosage of the typical well. After processing water control measures, the production data shows that the water content decreased significantly after opening the well, from 95.1% before water control to 80%, which was 15% lower. Also the oil production rate has a significant increase from 2.3t/d before water control to maximum to 9t/d after implementing control measures and cumulative oil increase is 550t with effective period of 135 days. The effect of oil and precipitation is obvious.

The Residual Potential of Bottom Water Reservoir Based upon Genetic Algorithm for the Relative Permeability Inversion

At present in the offshore oilfield, X oilfield had successfully developed bottom water reservoir with horizontal well. The development mode of single sand body of horizontal well caused water cut rose rapidly and irresistible bottom water coning. The common empirical formula of recoverable reserves obtained through statistical analysis was not applicable to the bottom water reservoir. Under the condition of as high as tens of thousands of time local scour multiple, underground seepage law had been changed. In order to improve the understanding of the remaining potential of bottom water reservoir in the ultra-high water cut stage, this research innovation proposed to carry out the flow tube simulation of the bottom water ridge. In addition, combining with the theoretical research of the quantitative characterization of the water ridge form and the vector permeability, theoretical model was established. At last, the phase permeability curve was calculated from the production data of the ultra-high water cut stage of the bottom water reservoir by combining the genetic algorithm. According to the change of water ridge and oil saturation, the mechanism of end point change of phase permeability curve was expounded, and the effective production radius of water drive oil in bottom water reservoir was put forward, which provided the basis for understanding the potential of oil field and tapping the potential in the future.

Modeling of three-dimensional sound propagation through solitary internal waves

An accurate and numerically efficient numerical model is very important for studying the effect of internal wave on underwawter sound propagation. A full-wave, three-dimensional (3D) coupled-mode model is able to deal with the internal wave problem with satisfactory accuracy, but such a model is in general numerically inefficient. A numerically efficient 3D model is presented for sound propagation in a range-dependent waveguide in the presence of solitary internal waves in this work. The present model is a forward-marching model that neglects backscattering. In this 3D model, an efficient two-dimensional (2D) coupled-mode model, C-SNAP, is adopted to compute 2D acoustic field solutions excited by a line source. The C-SNAP is a 2D forward-marching model, which uses an energy-conserving matching condition to preserve accuracy. An appealing aspect of C-SNAP is that its efficiency is competitive with that of the existing parabolic equation model. The integral transform technique is used to extend C-SNAP to a 3D model, where a complex integration contour is used for evaluating the wavenumber integral. A brief review of C-SNAP and formulation of the present 3D model are given. The forward-marching models are primarily suitable for treating the range-dependent problems with weak backscattering, such as with a slowly varying bathymetry. Since in general the backscattering from internal wave is weak, which is also validated numerically in this work, the present model is able to address the problem of sound propagation through internal wave with satisfactory accuracy. At the same time, it achieves an efficiency gain of at least an order of magnitude over that of full two-way, 3D model. In addition to the internal wave, the present model is also suitable for solving the general range-dependent problems where backscattering is weak, such as in the presence of a bottom ridge of a small height. Numerical simulations are also provided to validate the present model, where a two-way, 3D model serves as the benchmark. The numerical results show that the effect of the internal wave on the acoustic field is negligible for the region between the source and the internal wave. However, the effect is significant on the other side of the internal wave. A more interesting observation is the angular dependence of the interference pattern induced by the internal wave.

Size synthesis method for disc cam mechanisms with a negative radius translating roller follower

This work considers a disc cam mechanism with an upright installed negative radius translating roller follower. Accurate descriptions, as well as the basic concept and steps, are given for the shape, basic/overall size, and size synthesis of the new mechanism. A size coordinate system O − r0 R and size domain Ω( r0, R) are established, which are given discrete-meshing (grid) treatment. In addition, four constraints are proposed for the calculation formula. The traversal technique is used to achieve visual mapping under single/merged constraints, which gives the corresponding boundary and solution domain. Then, a combination of multiobjective planning and visual mapping reveals important principles such as the non-inferior region [Formula: see text], ridge point [Formula: see text]/ridge line ∂ [Formula: see text], and bottom ridge point P**/double optimal point [Formula: see text], as well as the existence of the global optimal solution. We have therefore obtained instructive and important conclusions for the size synthesis of the new mechanism.

Numerical simulation of interaction between internal solitary waves and submerged ridges

Direct numerical simulations are performed to study the transformation of internal solitary waves (ISWs) of depression type propagating over an underwater ridge in a two-layer fluid system. Bottom ridges with relatively smooth vertex are employed to represent sills in natural lakes and oceans. Consistent with previous experiments, three interaction types (weak, moderate and strong) are observed to be based on the energy loss. In addition, the moderate interaction are found to be categorized into transmitted and reflected type according to their distinct transformation process. General flow characteristics for ISW–ridge interaction in the benthic boundary layer and in the pycnocline is monitored and analysed. A modified degree of blocking Bm considering both the nonlinear effect of incident ISWs and the blockage effect of the submerged ridge is proposed. Different ISW–ridge interactions are discovered to be linked with Bm. Maximum wave-induced velocities, wave energy losses, reflected and transmitted wave amplitudes are found to have a self-similar feature with Bm. The maximum energy loss is up to 35% and the maximum wave-induced velocity can reach 1.8 times of the phase speed of the incident ISW. Empirical equations are obtained based on the data fitting to predict some useful physical parameters during ISW–ridge interaction.

Nonlinear Wave Equations for Oceanic Internal Solitary Waves

In the coastal ocean, the interaction of barotropic tidal currents with topographic features such as the continental shelf, sills in narrow straits, and bottom ridges are often observed to generate large amplitude, horizontally propagating internal solitary waves. These are long nonlinear waves and hence can be modeled by equations of the Korteweg–de Vries type. Typically they occur in regions of variable bottom topography, with the consequence that the appropriate nonlinear evolution equation has variable coefficients. Further, as these waves can be long‐lived it is necessary to take account of the effects of the Earth's background rotation. We review this family of model evolution equations and some of their pertinent solutions, obtained both asymptotically and numerically.

Supervised machine learning for estimation of rough bottom anisotropy direction using bistatic acoustic scattered fields

An issue when trying to use scattered acoustic fields to classify underwater targets is the strong directional scattering due to anisotropic rough bottom structure that occurs in the 1-5 kHz frequency range. Autonomous Underwater Vehicles (AUVs) are uniquely suited to exploit this three dimensional field with the goal of estimating the anisotropy direction of the bottom roughness. Estimation of the angle of bottom roughness ridges relative to an acoustic source is carried out using a combination of supervised machine learning and AUV behaviors. Anisotropic Goff-Jordan power spectrum bottom scattered fields in 15 degree angle increments are generated using SCATT and OASES acoustic packages. The amplitudes of these fields are sampled into sets of 5-20 AUV waypoints. Support Vector Machine (SVM) regression is used to train a model, and an independent test data set is used to evaluate the validity of the model. A confidence model is constructed and critical waypoints identified using the test set results. The confidence and SVM models can then be used to determine bottom roughness angle in real time, as demonstrated using the LAMSS MOOS-IvP simulation environment.

Propagation properties of a surface plasmonicwaveguide with a bowtie air cores

A kind of surface plasmonic waveguide with a bowtie shaped air core was designed. The dependence of distribution of longitudinal energy flux density, effective index and propagation length of the fundamental mode supported by this waveguide on geometrical parameters and working wavelength were analyzed using the finite-difference frequency-domain (FDFD) method. Results show that the longitudinal energy flux density distributes mainly in the center region which is formed by the top and the bottom ridge. The effective index and propagation length of the fundamental mode can be adjusted by the geometric parameters as well as the working wavelength. At a given working wavelength, the effective index decreases as the radius of ridge increases, meanwhile propagation length and mode area of the fundamental mode increase as radius of ridge increases. The geometric parameter of radius of circles at four corner can affect the propagation properties slightly. The radius of sectors on both sides can effect propagation properties obviously. With given geometric parameters, relative to the case of λ=705.0 nm, in the case of larger λ, the area of field distribution is larger, and the size of the contact area of field and metallic surface is also larger, then the interaction of field and silver is weaker, and the effective index becomes smaller, so the propagation length becomes larger. The possibility of applying this kind of surface plasmonic waveguide to the field of sensors was discussed.

Transcritical shallow-water flow past topography: finite-amplitude theory

We consider shallow-water flow past a broad bottom ridge, localized in the flow direction, using the framework of the forced Su–Gardner (SG) system of equations, with a primary focus on the transcritical regime when the Froude number of the oncoming flow is close to unity. These equations are an asymptotic long-wave approximation of the full Euler system, obtained without a simultaneous expansion in the wave amplitude, and hence are expected to be superior to the usual weakly nonlinear Boussinesq-type models in reproducing the quantitative features of fully nonlinear shallow-water flows. A combination of the local transcritical hydraulic solution over the localized topography, which produces upstream and downstream hydraulic jumps, and unsteady undular bore solutions describing the resolution of these hydraulic jumps, is used to describe various flow regimes depending on the combination of the topography height and the Froude number. We take advantage of the recently developed modulation theory of SG undular bores to derive the main parameters of transcritical fully nonlinear shallow-water flow, such as the leading solitary wave amplitudes for the upstream and downstream undular bores, the speeds of the undular bores edges and the drag force. Our results confirm that most of the features of the previously developed description in the framework of the unidirectional forced Korteweg–de Vries (KdV) model hold up qualitatively for finite amplitude waves, while the quantitative description can be obtained in the framework of the bidirectional forced SG system. Our analytic solutions agree with numerical simulations of the forced SG equations within the range of applicability of these equations.

Sea Surface Manifestation of Along-Tidal-Channel Underwater Ridges Imaged by SAR

A group of submerged ocean bottom sand ridges in the Bohai Sea, China, are shown in RADARSAT-1 and ENVISAT synthetic aperture radar (SAR) images. The sand ridges appear as fingerlike quasi-linear features in the SAR images. Examining the detailed local bathymetry chart, we find that these features coincide with the satellite images. The heights of the sand ridges are less than 10 m, and the water depth is between 10 and 30 m. The spacing of the sand ridges is about 10 km, and the length of the sand ridges is about 20 km. The same sand ridges are also visible on a Moderate Resolution Imaging Spectroradiometer (MODIS) true-color image. The semidiurnal and diurnal tidal currents in this area are almost parallel to the major axis of these sand ridges. These observations cannot be explained using the existing 1-D SAR imaging model, which is not applicable to sand ridges parallel to the tidal current. In this paper, we consider the shallow-water current bathymetry in a 2-D space. An analytical ocean model was applied to demonstrate the temporal variations of the current divergence and convergence that are induced by the along-sand-ridge-direction current and ridge interaction. A radar simulation model is used to simulate the variation of normalized radar cross section (NRCS) induced by the ocean surface current. The simulated NRCS variation is similar to that extracted from the calibrated SAR image. Simulation results also show that the NRCS variation becomes negligible when the ocean current is set to about half of the maximum tidal current.

Formation of undular bores and solitary waves in the Strait of Malacca caused by the 26 December 2004 Indian Ocean tsunami

Deformation of the Indian Ocean tsunami moving into the shallow Strait of Malacca and formation of undular bores and solitary waves in the strait are simulated in a model study using the fully nonlinear dispersive method (FNDM) and the Korteweg‐deVries (KdV) equation. Two different versions of the incoming wave are studied where the waveshape is the same but the amplitude is varied: full amplitude and half amplitude. While moving across three shallow bottom ridges, the back face of the leading depression wave steepens until the wave slope reaches a level of 0.0036–0.0038, when short waves form, resembling an undular bore for both full and half amplitude. The group of short waves has very small amplitude in the beginning, behaving like a linear dispersive wave train, the front moving with the shallow water speed and the tail moving with the linear group velocity. Energy transfer from long to short modes is similar for the two input waves, indicating the fundamental role of the bottom topography to the formation of short waves. The dominant period becomes about 20 s in both cases. The train of short waves, emerging earlier for the larger input wave than for the smaller one, eventually develops into a sequence of rank‐ordered solitary waves moving faster than the leading depression wave and resembles a fission of the mother wave. The KdV equation has limited capacity in resolving dispersion compared to FNDM.

Quantitative Analyses of Absorption-Sensitive Surface Plasmon Resonance Near-Infrared Spectra

Surface plasmon resonance near-infrared (SPR-NIR) spectroscopy provides 10-100 times absorption enhancement compared with the absorption in the corresponding attenuated total reflection (ATR) NIR spectra. However, analysis of the enhanced SPR-NIR spectra is not straightforward because of the substantial contribution from SPR. This paper proposes two analysis methods for concentration-dependent changes of SPR-NIR spectra from a viewpoint of change in absorption intensity. One is based on rapid scans of the SPR-NIR spectra with a fixed incident angle, and the other is based on multi-angle sequential scans. A concentration of methanol in water has successfully been determined by both methods. From the measurement of the light intensity within an absorption band of water (5230-5120 cm(-1)) at a fixed incident angle, the concentration was calibrated to an accuracy of 0.02 wt. %. In the latter multi-angle method, it has been proved that computed bottom ridges of the envelope curve of the SPR-NIR spectra are not only enhanced 30 times compared with the corresponding ATR-NIR spectra, but are also equivalent to the conventional transmittance NIR spectra in quality. The bottom ridges allow us to analyze SPR-NIR spectra in the same manner as conventional spectral analyses based on Beer's law.

Modelling the motion of an internal solitary wave over a bottom ridge in a stratified fluid

A series of laboratory experiments has been carried out to investigate the passage of an internal solitary wave of depression over a bottom ridge, in a two-layer fluid system for which the upper and lower layer is linearly-stratified and homogeneous respectively. Density, velocity and vorticity fields induced by the wave propagation over the ridge have been measured simultaneously at three locations, namely upstream, downstream and over the ridge crest, for a wide range of model parameters. Results are presented to show that wave breaking may occur for a sufficiently large wave amplitude and a strong ridge blockage factor, with accompanying mixing and overturning. Density field data are presented (i) to illustrate the overturning and mixing processes that accompany the wave breaking and (ii) to quantify the degree of mixing in terms of the wave and ridge parameters. For weak encounters, good agreement is obtained between the laboratory experimental results (velocity and vorticity fields induced by the wave propagation) and the predictions of a recently-developed fully nonlinear theory. Discrepancies between theory and experiment are discussed for cases in which breaking and mixing occur.