The Experts below are selected from a list of 12789 Experts worldwide ranked by ideXlab platform
Hilmi Demiray - One of the best experts on this subject based on the ideXlab platform.
-
on Progressive Wave solution for non planar kdv equation in a plasma with q nonextensive electrons and two oppositely charged ions
2020Co-Authors: Hilmi Demiray, Essam R Elzahar, S A ShanAbstract:The second author is partially supported by the Deanship of Scientific Research at Prince Sattam bin Abdulaziz University under grant No. 2019/1/11000.
-
weakly non linear Waves in a tapered elastic tube filled with an inviscid fluid
International Journal of Non-linear Mechanics, 2005Co-Authors: Ilkay Bakirtas, Hilmi DemirayAbstract:In the present work, treating the artery as a tapered, thin walled, long and circularly conical prestressed elastic tube and using the longWave approximation, we have studied the propagation of weakly non-linear Waves in such a fluid-filled elastic tube by employing the reductive perturbation method. By considering the blood as an incompressible inviscid fluid, the evolution equation is obtained as the Korteweg-de Vries equation with a variable coefficient. It is shown that this type of equation admits a solitary Wave-type solution with variable Wave speed. It is observed that, the Wave speed decreases with distance for positive tapering while it increases for negative tapering. It is further observed that, the Progressive Wave profile for expanding tubes (a>0) becomes more steepened whereas for narrowing tubes (a<0) it becomes more flattened.
-
On the existence of some evolution equations in fluid-filled elastic tubes and their Progressive Wave solutions
International Journal of Engineering Science, 2004Co-Authors: Hilmi DemirayAbstract:In the present work, by employing the nonlinear equations of motion of an incompressible, isotropic and prestressed thin elastic tube and the approximate equations of an incompressible inviscid fluid, we studied the existence of some possible evolution equations in the longWave approximation and their Progressive Wave solutions. It is shown that, depending on the set of values of the initial deformation, it might be possible to obtain the conventional Korteweg-deVries (KdV) and the modified KdV equations of various forms. Finally, a set of Progressive Wave solutions is presented for such evolution equations.
S D Mobbs - One of the best experts on this subject based on the ideXlab platform.
-
numerical simulations of air water flow of a non linear Progressive Wave in an opposing wind
Boundary-Layer Meteorology, 2015Co-Authors: X Wen, S D MobbsAbstract:We present detailed numerical results for two-dimensional viscous air–water flow of a non-linear Progressive water Wave when the speed of the opposing wind varies from zero to 1.5 times the Wave phase speed. It is revealed that at any speed of the opposing wind there exist two rotating airflows, one anti-clockwise above the Wave peak and one clockwise above the Wave trough. These rotating airflows form a buffer layer between the main stream of the opposing wind and the Wave surface. The thickness of the buffer layer decreases and the strength of rotation increases as the wind speed increases. The profile of the average $$x$$ -component of velocity reveals that the water Wave behaves as a solid surface producing larger wind stress compared to the following-wind case.
-
numerical simulations of laminar air water flow of a non linear Progressive Wave at low wind speed
Boundary-Layer Meteorology, 2014Co-Authors: X Wen, S D MobbsAbstract:A numerical simulation for two-dimensional laminar air–water flow of a non-linear Progressive water Wave with large steepness is performed when the background wind speed varies from zero to the Wave phase speed. It is revealed that in the water the difference between the analytical solution of potential flow and numerical solution of viscous flow is very small, indicating that both solutions of the potential flow and viscous flow describe the water Wave very accurately. In the air the solutions of potential and viscous flows are very different due to the effects of viscosity. The velocity distribution in the airflow is strongly influenced by the background wind speed and it is found that three wind speeds, $$U=0$$ , $$U=u_m$$ (the maximum orbital velocity of a water Wave), and $$U=c$$ (the Wave phase speed), are important in distinguishing different features of the flow patterns.
R E Uittenbogaard - One of the best experts on this subject based on the ideXlab platform.
-
sand transport beneath Waves the role of Progressive Wave streaming and other free surface effects
Journal of Geophysical Research, 2013Co-Authors: Wouter Kranenburg, Jan S Ribberink, Jolanthe J L M Schretlen, R E UittenbogaardAbstract:Recent large-scale Wave flume experiments on sheet-flow sediment transport beneath Stokes Waves show more onshore-directed sediment transport than earlier sheet-flow experiments in oscillating flow tunnels. For fine sand, this extends to a reversal from offshore- (tunnels) to onshore (flumes)-directed transport. A remarkable hydrodynamic mechanism present in flumes (with free water surface), but not in tunnels (rigid lid), is the generation of Progressive Wave streaming, an onshore Wave boundary layer current. This article investigates whether this streaming is the full explanation of the observed differences in transport. In this article, we present a numerical model of Wave-induced sand transport that includes the effects of the free surface on the bottom boundary layer. With these effects and turbulence damping by sediment included, our model yields good reproductions of the vertical profile of the horizontal (mean) velocities, as well as transport rates of both fine and medium sized sediment. Similar to the measurements, the model reveals the reversal of transport direction by free surface effects for fine sand. A numerical investigation of the relative importance of the various free surface effects shows that Progressive Wave streaming indeed contributes substantially to increased onshore transport rates. However, especially for fine sands, horizontal gradients in sediment advection in the horizontally nonuniform flow field also are found to contribute significantly. We therefore conclude that not only streaming, but also inhomogeneous sediment advection should be considered in formulas of Wave-induced sediment transport applied in morphodynamic modeling. We propose a variable time-scale parameter to account for these effects.
-
net currents in the Wave bottom boundary layer on Waveshape streaming and Progressive Wave streaming
Journal of Geophysical Research, 2012Co-Authors: Wouter Kranenburg, Jan S Ribberink, R E Uittenbogaard, Suzanne J M H HulscherAbstract:The net current (streaming) in a turbulent bottom boundary layer under Waves above a flat bed, identified as potentially relevant for sediment transport, is mainly determined by two competing mechanisms: an onshore streaming resulting from the horizontal non-uniformity of the velocity field under Progressive free surface Waves, and an offshore streaming related to the nonlinearity of the Waveshape. The latter actually contains two contributions: oscillatory velocities under nonlinear Waves are characterized in terms of velocity-skewness and acceleration-skewness (with pure velocity-skewness under Stokes Waves and acceleration-skewness under steep sawtooth Waves), and both separately induce offshore streaming. This paper describes a 1DV Reynolds-averaged boundary layer model withk-eturbulence closure that includes all these streaming processes. The model is validated against measured period-averaged and time-dependent velocities, from 4 different well-documented laboratory experiments with these processes in isolation and in combination. Subsequently, the model is applied in a numerical study on the Waveshape and free surface effects on streaming. The results show how the dimensionless parameterskh (relative water depth) and A/kN (relative bed roughness) influence the (dimensionless) streaming velocity and shear stress and the balance between the mechanisms. For decreasing kh, the relative importance of Waveshape streaming over Progressive Wave streaming increases, qualitatively consistent with earlier analytical modeling. Unlike earlier results, simulations for increased roughness (smaller A/kN) show a shift of the streaming profile in onshore direction for all kh. Finally, the results are parameterized and the possible implications of the streaming processes on sediment transport are shortly discussed
Wouter Kranenburg - One of the best experts on this subject based on the ideXlab platform.
-
sand transport beneath Waves the role of Progressive Wave streaming and other free surface effects
Journal of Geophysical Research, 2013Co-Authors: Wouter Kranenburg, Jan S Ribberink, Jolanthe J L M Schretlen, R E UittenbogaardAbstract:Recent large-scale Wave flume experiments on sheet-flow sediment transport beneath Stokes Waves show more onshore-directed sediment transport than earlier sheet-flow experiments in oscillating flow tunnels. For fine sand, this extends to a reversal from offshore- (tunnels) to onshore (flumes)-directed transport. A remarkable hydrodynamic mechanism present in flumes (with free water surface), but not in tunnels (rigid lid), is the generation of Progressive Wave streaming, an onshore Wave boundary layer current. This article investigates whether this streaming is the full explanation of the observed differences in transport. In this article, we present a numerical model of Wave-induced sand transport that includes the effects of the free surface on the bottom boundary layer. With these effects and turbulence damping by sediment included, our model yields good reproductions of the vertical profile of the horizontal (mean) velocities, as well as transport rates of both fine and medium sized sediment. Similar to the measurements, the model reveals the reversal of transport direction by free surface effects for fine sand. A numerical investigation of the relative importance of the various free surface effects shows that Progressive Wave streaming indeed contributes substantially to increased onshore transport rates. However, especially for fine sands, horizontal gradients in sediment advection in the horizontally nonuniform flow field also are found to contribute significantly. We therefore conclude that not only streaming, but also inhomogeneous sediment advection should be considered in formulas of Wave-induced sediment transport applied in morphodynamic modeling. We propose a variable time-scale parameter to account for these effects.
-
net currents in the Wave bottom boundary layer on Waveshape streaming and Progressive Wave streaming
Journal of Geophysical Research, 2012Co-Authors: Wouter Kranenburg, Jan S Ribberink, R E Uittenbogaard, Suzanne J M H HulscherAbstract:The net current (streaming) in a turbulent bottom boundary layer under Waves above a flat bed, identified as potentially relevant for sediment transport, is mainly determined by two competing mechanisms: an onshore streaming resulting from the horizontal non-uniformity of the velocity field under Progressive free surface Waves, and an offshore streaming related to the nonlinearity of the Waveshape. The latter actually contains two contributions: oscillatory velocities under nonlinear Waves are characterized in terms of velocity-skewness and acceleration-skewness (with pure velocity-skewness under Stokes Waves and acceleration-skewness under steep sawtooth Waves), and both separately induce offshore streaming. This paper describes a 1DV Reynolds-averaged boundary layer model withk-eturbulence closure that includes all these streaming processes. The model is validated against measured period-averaged and time-dependent velocities, from 4 different well-documented laboratory experiments with these processes in isolation and in combination. Subsequently, the model is applied in a numerical study on the Waveshape and free surface effects on streaming. The results show how the dimensionless parameterskh (relative water depth) and A/kN (relative bed roughness) influence the (dimensionless) streaming velocity and shear stress and the balance between the mechanisms. For decreasing kh, the relative importance of Waveshape streaming over Progressive Wave streaming increases, qualitatively consistent with earlier analytical modeling. Unlike earlier results, simulations for increased roughness (smaller A/kN) show a shift of the streaming profile in onshore direction for all kh. Finally, the results are parameterized and the possible implications of the streaming processes on sediment transport are shortly discussed
X Wen - One of the best experts on this subject based on the ideXlab platform.
-
numerical simulations of air water flow of a non linear Progressive Wave in an opposing wind
Boundary-Layer Meteorology, 2015Co-Authors: X Wen, S D MobbsAbstract:We present detailed numerical results for two-dimensional viscous air–water flow of a non-linear Progressive water Wave when the speed of the opposing wind varies from zero to 1.5 times the Wave phase speed. It is revealed that at any speed of the opposing wind there exist two rotating airflows, one anti-clockwise above the Wave peak and one clockwise above the Wave trough. These rotating airflows form a buffer layer between the main stream of the opposing wind and the Wave surface. The thickness of the buffer layer decreases and the strength of rotation increases as the wind speed increases. The profile of the average $$x$$ -component of velocity reveals that the water Wave behaves as a solid surface producing larger wind stress compared to the following-wind case.
-
numerical simulations of laminar air water flow of a non linear Progressive Wave at low wind speed
Boundary-Layer Meteorology, 2014Co-Authors: X Wen, S D MobbsAbstract:A numerical simulation for two-dimensional laminar air–water flow of a non-linear Progressive water Wave with large steepness is performed when the background wind speed varies from zero to the Wave phase speed. It is revealed that in the water the difference between the analytical solution of potential flow and numerical solution of viscous flow is very small, indicating that both solutions of the potential flow and viscous flow describe the water Wave very accurately. In the air the solutions of potential and viscous flows are very different due to the effects of viscosity. The velocity distribution in the airflow is strongly influenced by the background wind speed and it is found that three wind speeds, $$U=0$$ , $$U=u_m$$ (the maximum orbital velocity of a water Wave), and $$U=c$$ (the Wave phase speed), are important in distinguishing different features of the flow patterns.
