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Inertial effects on the performance of a bottom-hinged oscillating wave surge converter
http://ntour.ntou.edu.tw:8080/ir/handle/987654321/52291
title: Inertial effects on the performance of a bottom-hinged oscillating wave surge converter abstract: Abstract: This paper theoretically and experimentally investigates the inertial effects of the flap body on the performance of a bottom-hinged oscillating wave surge converter (BH-OWSC). A two-dimensional (2D) hydrodynamic theory for a BH-OWSC based on the assumption of potential flow is developed to show that one simple but critical parameter, i.e., the square of sum of three mechanical-impedance terms associated with the inertial effects, can precisely characterize the performance trend of a BH-OWSC. Model testing in a small-scaled wave basin follows to validate the theoretical formulations with a flap body consisting of multiple hollow cylinders into which water can be filled individually to alter the values of flap's inertial parameters. The performance of each inertial specification of the flap model is evaluated based on the measurement of the mean water discharge from the hydraulic pump (or the power take-off). Finally, the “near resonant condition” has been validated experimentally by altering the inertial parameters of the flap. Thus, the aforementioned parameter is shown to be capable of characterizing the inertial effects on the performance of a BH-OWSC, and the minimization of it will maximize the power capturing performance of a BH-OWSC. Consequently, the parameter can be used for design guidelines of the flap body in its inertial aspect, such as locating the center of mass and determining the geometric dimensions of a flap body.
<br>THE TREFFTZ TEST FUNCTIONS METHOD FOR SOLVING THE GENERALIZED INVERSE BOUNDARY VALUE PROBLEMS OF LAPLACE EQUATION
http://ntour.ntou.edu.tw:8080/ir/handle/987654321/52290
title: THE TREFFTZ TEST FUNCTIONS METHOD FOR SOLVING THE GENERALIZED INVERSE BOUNDARY VALUE PROBLEMS OF LAPLACE EQUATION abstract: Abstract: The issue of data completion is important for the elliptic type partial differential equation. In the inverse Cauchy problem, we need to complete the boundary data by over-specifying Dirichlet and Neumann data on a portion of the boundary. In this paper, we numerically solve the generalized inverse boundary value problems of Laplace equation in a rectangle with one boundary function and two boundary functions missing, which are more difficult than the inverse Cauchy problem. By using the technique of a boundary integral equation method together with a specially designed Trefftz test function, we can complete the boundary data by requiring minimal extra data. Then solving the Laplace equation with the given data and recovered data by the multiple-scale Trefftz method, we can find the numerical solution in the interior nodal points.
<br>USING REPRODUCING KERNEL PARTICLE METHOD FOR SHALLOW WATER PROBLEMS
http://ntour.ntou.edu.tw:8080/ir/handle/987654321/52041
title: USING REPRODUCING KERNEL PARTICLE METHOD FOR SHALLOW WATER PROBLEMS abstract: Abstract: In this paper, a meshfree numerical scheme, which is based on the reproducing kernel particle method (RKPM), is proposed to solve the shallow water equations (SWEs). By applying the split coefficient matrix method on SWEs, RK approximation with upstream scheme can be employed for spatial discretization.
Temporal discretization of SWEs is handled by the secondorder total-variation diminishing Runge-Kutta method. The merits of the present method are verified by performing three numerical experiments, which are problems related to open channel flow, oblique hydraulic jump and two-dimensional dam break. It is found that the proposed meshfree numerical scheme is able to efficiently model the shallow water problems with
high convergence rate and accuracy. When non-uniform discretization is used in conjunction with the proposed method,the order of approximation and accuracy can still be maintained.
<br>Single cavitation bubble generation and observation of the bubble collapse flow induced by a pressure wave
http://ntour.ntou.edu.tw:8080/ir/handle/987654321/50350
title: Single cavitation bubble generation and observation of the bubble collapse flow induced by a pressure wave abstract: Abstract: This study utilizes a U-shape platform device to generate a single cavitation bubble for a detailed analysis of the flow field characteristics and the cause of the counter jet during the process of bubble collapse caused by sending a pressure wave. A high speed camera is used to record the flow field of the bubble collapse at different distances from a solid boundary. It is found that a KelvinâHelmholtz vortex is formed when a liquid jet penetrates the bubble surface after the bubble is compressed and deformed. If the bubble center to the solid boundary is within one to three times the bubbleâs radius, a stagnation ring will form on the boundary when impinged by the liquid jet. The fluid inside the stagnation ring will be squeezed toward the center of the ring to form a counter jet after the bubble collapses. At the critical position, where the bubble center from the solid boundary is about three times the bubbleâs radius, the bubble collapse flow will vary. Depending on the strengths of the pressure waves applied, the collapse can produce a KelvinâHelmholtz vortex, the RichtmyerâMeshkov instability, or the generation of a counter jet flow. If the bubble surface is in contact with the solid boundary, the liquid jet can only move inside-out without producing the stagnation ring and the counter jet; thus, the bubble collapses along the radial direction. The complex phenomenon of cavitation bubble collapse flows is clearly manifested in this study.
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