SUSTech KC
http:///kc.sustech.edu.cn:80
南方科技大学
Wed, 26 Jan 2022 10:21:53 GMT
20220126T10:21:53Z

Experimental study on gas mass transfer process in a heterogeneous coal reservoir
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/267197
Title: Experimental study on gas mass transfer process in a heterogeneous coal reservoir
Authors: Men，Xinyang; Tao，Shu; Liu，Zhenxing; Tian，Wenguang; Chen，Shida
Description: <p>Series and parallel seepage simulation experiments of coal matrix pore sample, natural fracture sample and artificial fracture sample with three permeability ranges were designed and performed. These three samples represent the low permeability zone, transition zone and fracturing zone in the development coal seam. In the parallel experiment, fracturing fractures are the dominant seepage channel, and the gas seepage in the matrix and natural fractures is limited. In the series experiment, a highefficiency mass transfer stage has the displacement pressure difference is greater than 7.3 MPa, which represents the coal reservoir has a strong gas supply capacity. On the contrary, a lowefficiency mass transfer stage appears when the displacement pressure difference is less than 7.3 MPa, suggesting the decline in gas supply capacity. Due to the rapid output of nearwell desorbed gas, a short gas production peak will be formed in the early production stage. After that, due to insufficient gas supply on the parallel path, the gas production rate drops rapidly. The second gas production peak appears in the highefficiency mass transfer stage. Finally, due to the limited expansion of the pressure drop funnel, the gas production gradually decreased and eventually stabilized after entering the lowefficiency mass transfer stage.</p>
Tue, 18 Jan 2022 06:31:51 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/267197
20220118T06:31:51Z

Numerical simulation of nonlinear wave transformation over a submerged plate
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266826
Title: Numerical simulation of nonlinear wave transformation over a submerged plate
Authors: Yu，Xiping; Isobe，Masahiko; Watanabe，Akira
Description: The Euler equation of fluid motion is integrated in the vertical direction by assuming a hyperbolic cosine distribution of pressure, as a result, quasilinear hyperbolic equations governing the wave motion above a solid bed are obtained. The equations are then applied to describing the wave transformation over a submerged plate. An algorithm based on the method of characteristics is developed in the numerical computation. The wave reflection and transmission coefficients computed under various conditions are compared with the experimental data, and the overall agreement is found to be fairly satisfactory.
Tue, 18 Jan 2022 06:03:58 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266826
20220118T06:03:58Z

Scattered waves around a submerged disk
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266825
Title: Scattered waves around a submerged disk
Authors: Yu，Xiping; Chwang，Allen
Description: Potential wave theory is employed to analyze the scattered waves around a submerged circular disk. general harmonic expressions of the velocity potential are obtained in subdomains and matched at their common boundary through a simple technique. Variation of the wave height around the disk versus the dimensionless disk radius and the relative water depth versus the dimensionless disk radius and the relative water depth is discussed. Relation between the wave force acting on the disk and the incident wave conditions is also presented.
Tue, 18 Jan 2022 06:03:56 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266825
20220118T06:03:56Z

Analysis of wave scattering by submerged circular disk
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266814
Title: Analysis of wave scattering by submerged circular disk
Authors: Yu，Xiping; Chwang，Allen T.
Description: Wave scattering over a horizontally submerged circular disk is analyzed by the linear potential wave theory. By means of the method of separation of variables, harmonic expressions of the velocity potential in terms of unknown constants are obtained in three subregions of the domain occupied by the fluid. A simple approach is employed to match these harmonic expressions at the common boundary of the subregions. The velocity potential is thus obtained, and consequently, the watersurface elevation is determined. Variation of the wave height around the submerged disk versus the dimensionless disk radius, the relative water depth, and the submerged depth ratio of the disk to the total water depth is presented and discussed. The results show an effect of wave focusing around the rear of the disk. It is also noted that shallowerwater waves undergo more significant scattering when the ratio of the disk radius to the incident wavelength is fixed. The pattern of the waveheight distribution is found to be closely related to the size of the disk but less dependent on the relative water depth. © ASCE.
Tue, 18 Jan 2022 06:03:24 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266814
20220118T06:03:24Z

Water waves above submerged porous plate
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266811
Title: Water waves above submerged porous plate
Authors: Yu，Xiping; Chwang，Allen T.
Description: Wave motion over a submerged porous plate is studied by the boundaryelement method based on the linear potential wave theory. The boundary condition at the porous plate is formulated under the assumption that the flow within the porous medium is governed by Darcy's law. The characteristics of variation of the reflection, the transmission, the loss of energy and the force versus the plate length, the water depth, the incident wavelength, the depth of submergence, and the porosity of the plate are discussed. It is shown that the reflection and transmission coefficients vary periodically as the relative length of the plate tothe incident wavelength increases. Moderately large values of the porosity of the plate are found to produce the maximum dissipation of the incident wave energy. It is also demonstrated that a plate with proper porosity can significantly suppress the reflection and reduce the wave force acting on it while the transmission can be kept at a low level. © ASCE.
Tue, 18 Jan 2022 06:03:21 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266811
20220118T06:03:21Z

Waveinduced oscillation in harbor with porous breakwaters
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266808
Title: Waveinduced oscillation in harbor with porous breakwaters
Authors: Yu，Xiping; Chwang，Allen T.
Description: Waveinduced oscillation in a semicircular harbor with porous breakwaters is studied on the basis of the linear potential wave theory and a newly derived boundary condition for the breakwaters. By separation of variables, general expressions of the velocity potential in terms of unknown constants are obtained in the harbor region and in the open sea. These expressions are matched so that the porous boundary condition and the continuity of mass flux and free surface at the harbor entrance are satisfied. The velocity potential and, consequently, the free surface oscillation in the whole domain concerned are thus determined. The frequency response of a harbor with breakwaters of various porous properties is investigated. It is noted that the inertial effect of the porous structure is mainly to increase the resonant wave number and it does not reduce the amplitude of the resonant oscillation significantly. On the other hand, the porous resistance gives rise to little change of the resonant wave number but it reduces the amplitude of the resonant oscillation effectively. A small but finite permeability of the breakwater is found to be optimal to diminish the resonant oscillation. © ASCE.
Tue, 18 Jan 2022 06:02:50 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266808
20220118T06:02:50Z

Wave motion through porous structures
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266803
Title: Wave motion through porous structures
Authors: Yu，Xiping; Chwang，Allen T.
Description: Linear potential theory is applied to the analysis of wave motion through a twolayer porous structure. For special cases, the characteristics of waves in nondissipative, weakly, as well as strongly, dissipative media and their relations with the inertial and resistive properties of the media are explored. It is noted that in a nondissipative medium, the wave components are either nonpropagative or nondecaying. In a dissipative medium, however, they are always propagative and decaying as well. The reflection, transmission, and dissipation of monochromatic incident waves by a rectangular block, with typical dissipative characteristics and various thickness as well as submergence of its crest, are studied by the method of matched velocity potentials. It is found that there is an optimum thickness for a porous structure beyond which any further increase of the thickness may not lead to an appreciable improvement of its functional performance in reducing the transmission and reflection. It is also discovered that a medium of moderate permeability may be favorable in the design of a widecrested breakwater if the wave heights on both front and lee sides of the structure are required to be controlled. © ASCE.
Tue, 18 Jan 2022 06:02:42 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266803
20220118T06:02:42Z

Diffraction of water waves by porous breakwaters
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266792
Title: Diffraction of water waves by porous breakwaters
Authors: Yu，Xiping
Description: Diffraction of water waves by porous breakwaters is studied based on the linear potential wave theory. The formulation of the problem includes a newly derived relation for the fluid motion through thin porous structures in addition to the conventional governing equation and boundary conditions for smallamplitude waves in ideal fluids. The porous boundary condition, indirectly verified by collected experimental data, is obtained by assuming that the flow within the porous medium is governed by a convectionneglected and porouseffectmodeled Euler equation. A vertically twodimensional problem with longcrested waves propagating in the normal direction of an infinite porous wall is first solved and the solution is compared with available experimental data. The wave diffraction by a semiinfinite porous wall is then studied by the boundarylayer method, in which the outer approximation is formulated by virtue of the reduced twodimensional solution. It is demonstrated that neglect of the inertial effect of the porous medium leads to an underestimate of the functional performance of a porous breakwater. © ASCE.
Tue, 18 Jan 2022 06:02:10 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266792
20220118T06:02:10Z

Irregular waves over an elliptic shoal
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266791
Title: Irregular waves over an elliptic shoal
Authors: Yu，Xiping; Togashi，Hiroyoshi
Description: A numerical model for the transformation of narrowbanded irregular waves over gradually varying bottom topography is presented. The model is based on the mild slope wave equation for component waves. Perturbation of the mild slope wave equation with respect to the deviation of the angular frequency of any component wave from that of a principal wave, which is a small quantity for waves of narrowbanded spectra, is carried out. The mild slope wave equation, which depends on the frequency of the component wave, can thus be replaced by the perturbation equations in terms of the principal wave parameters. The finite element method is considered for numerical solutions of the perturbation equations. Since the matrix of the linear algebraic finite element equations depends on neither the component wave properties nor the order of the perturbation, numerical solution of an irregular wave field can be efficiently obtained. The model is applied to the computation of the wave motion over an elliptic shoal. The computed wave height distribution shows satisfactory agreement with the available experimental data.
Tue, 18 Jan 2022 06:02:09 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266791
20220118T06:02:09Z

Wave breaking over submerged horizontal plate
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266790
Title: Wave breaking over submerged horizontal plate
Authors: Yu，Xiping; Isobe，Masahiko; Watanabe，Akira
Description: The inceptive condition for wave breaking over a submerged horizontal plate is proposed. The incident wave parameter I = gH<inf>o</inf>/C<sup>2</sup><inf>h</inf>, which reduces to the relative wave height for long waves and is proportional to the wave steepness for deepwater waves, is used as the breaking index. Waves break over the plate when I is greater than a critical value I<inf>c</inf> which depends on the ratio of the wave celerity over the plate to that of the incident wave and also on the relative length of the plate to the incident wavelength. The establishment of the breaking inceptive condition is based on an empirical formula for partial standing waves breaking in uniform water depth. To determine the relation between the local waves over the plate and the incident wave, linear analysis is employed, and a modification is then made to take into account the nonlinear effect. A laboratory experiment is carried out to verify the semiempirically established breaking condition, and satisfactory agreement between the semiempirical prediction and the experimental observation is obtained. © ASCE.
Tue, 18 Jan 2022 06:02:07 GMT
http:///kc.sustech.edu.cn:80/handle/2SGJ60CL/266790
20220118T06:02:07Z