In this paper,numerical modeling and model testing of a complex-shaped remotely-operated vehicle（ROV） were shown.The paper emphasized the systematic modeling of hydrodynamic damping using the computational fluid dyn...In this paper,numerical modeling and model testing of a complex-shaped remotely-operated vehicle（ROV） were shown.The paper emphasized the systematic modeling of hydrodynamic damping using the computational fluid dynamic software ANSYS-CFXTM on the complex-shaped ROV,a practice that is not commonly applied.For initial design and prototype testing during the developmental stage,small-scale testing using a free-decaying experiment was used to verify the theoretical models obtained from ANSYS-CFXTM.Simulation results are shown to coincide with the experimental tests.The proposed method could determine the hydrodynamic damping coefficients of the ROV.展开更多
Clarifying how radial gap affects the vibration characteristic of a disc-like structure is of importance in engineering applications,such as in evaluating the operational stability of a runner of a pump turbine.In the...Clarifying how radial gap affects the vibration characteristic of a disc-like structure is of importance in engineering applications,such as in evaluating the operational stability of a runner of a pump turbine.In the present investigation,the runner is simplified as a disc,and a physical experiment is designed on it with variable radial gaps to measure the vibration characteristics,especially by considering rotation.Two frequency peaks for the diametrical mode are generated due to the rotation,and those with lower and higher frequencies are defined as positive and negative modes,respectively.The frequency difference between positive and negative modes increases linearly with the increasing rotating speed,and a linear function is captured to describe the relationship between natural frequency and rotating speed.Regarding the radial gap,its increase causes a slight increase in the natural frequencies but results in a significant reduction in the hydrodynamic damping ratio.Especially in the smaller radial gap conditions,such as when the relative radial gap increases from 0.67%to 3.3%,the reduction in hydrodynamic damping ratio reaches 31.52%.From the perspective of suppressing the resonance amplitude,reducing the radial gap of a runner is recommended due to the mechanism of increasing hydrodynamic damping.展开更多
In this paper, a compact finite difference method is presented for solving the initial boundary value problems for the improved Boussinesq equation with damping terms. The fourth-order equation can be transformed into...In this paper, a compact finite difference method is presented for solving the initial boundary value problems for the improved Boussinesq equation with damping terms. The fourth-order equation can be transformed into a first-order ordinary differential system, and then, the classical Pad4 approximation is used to discretize spatial derivative in the non- linear partial differential equations. The resulting coefficient matrix for the semi-discrete scheme is tri-diagonal and can be solved efficiently. In order to maintain the same order of convergence, the classical fourth-order Runge-Kutta method is the preferred method for explicit time integration. Soliton-type solutions are used to evaluate the accuracy of the method, and various numerical experiments are designed to test the different effects of the damping terms.展开更多
文摘In this paper,numerical modeling and model testing of a complex-shaped remotely-operated vehicle（ROV） were shown.The paper emphasized the systematic modeling of hydrodynamic damping using the computational fluid dynamic software ANSYS-CFXTM on the complex-shaped ROV,a practice that is not commonly applied.For initial design and prototype testing during the developmental stage,small-scale testing using a free-decaying experiment was used to verify the theoretical models obtained from ANSYS-CFXTM.Simulation results are shown to coincide with the experimental tests.The proposed method could determine the hydrodynamic damping coefficients of the ROV.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52179092,51879266)supported by the 2115 Talent Development Program of China Agricultural University.
文摘Clarifying how radial gap affects the vibration characteristic of a disc-like structure is of importance in engineering applications,such as in evaluating the operational stability of a runner of a pump turbine.In the present investigation,the runner is simplified as a disc,and a physical experiment is designed on it with variable radial gaps to measure the vibration characteristics,especially by considering rotation.Two frequency peaks for the diametrical mode are generated due to the rotation,and those with lower and higher frequencies are defined as positive and negative modes,respectively.The frequency difference between positive and negative modes increases linearly with the increasing rotating speed,and a linear function is captured to describe the relationship between natural frequency and rotating speed.Regarding the radial gap,its increase causes a slight increase in the natural frequencies but results in a significant reduction in the hydrodynamic damping ratio.Especially in the smaller radial gap conditions,such as when the relative radial gap increases from 0.67%to 3.3%,the reduction in hydrodynamic damping ratio reaches 31.52%.From the perspective of suppressing the resonance amplitude,reducing the radial gap of a runner is recommended due to the mechanism of increasing hydrodynamic damping.
文摘In this paper, a compact finite difference method is presented for solving the initial boundary value problems for the improved Boussinesq equation with damping terms. The fourth-order equation can be transformed into a first-order ordinary differential system, and then, the classical Pad4 approximation is used to discretize spatial derivative in the non- linear partial differential equations. The resulting coefficient matrix for the semi-discrete scheme is tri-diagonal and can be solved efficiently. In order to maintain the same order of convergence, the classical fourth-order Runge-Kutta method is the preferred method for explicit time integration. Soliton-type solutions are used to evaluate the accuracy of the method, and various numerical experiments are designed to test the different effects of the damping terms.
