Computational Fluid Dynamics(CFD)investigations into water entry problems of a rigid flat plate with air pockets were systematically conducted.The Volume of Fluid(VOF)model was utilised to capture localised slamming p...Computational Fluid Dynamics(CFD)investigations into water entry problems of a rigid flat plate with air pockets were systematically conducted.The Volume of Fluid(VOF)model was utilised to capture localised slamming phenomena that occur during,and post-impact events.The model’s geometry was modified to include a pocket on the slamming impact surface to investigate the effect of air entrapment on the magnitude and distribution of slamming forces and pressures.A parametric study was conducted on the geometric parameters of the modelled pocket by altering its area,depth,and volume to exam-ine the response of slamming force and pressure loading under several impact velocities.The numerical results of slamming forces and pressures were in good agreement with experimental drop test measure-ments(with relative error of-6%and 7%for the magnitude of slamming force and pressure,respectively).The numerical results proved that the peak pressure is proportional to the magnitude of impact velocity squared(p maxαv^(2)).展开更多
A mathematical model is presented for the charging-up process in an air-entrapped pipeline with moving boundary conditions. A coordinate transformation technique is employed to reduce fluid motion in time-dependent do...A mathematical model is presented for the charging-up process in an air-entrapped pipeline with moving boundary conditions. A coordinate transformation technique is employed to reduce fluid motion in time-dependent domains to ones in time-independent domains. The nonlinear hyperbolic partial differential equations governing the unsteady motion of fluid combined with an equation for transient shear stress between the pipe wall and the flowing fluid are solved by the method of lines. Results show that ignoring elastic effects overestimates the maximum pressure and underestimates the maximum front velocity of filling fluid. The peak pressure of the entrapped air is sensitive to the length of the initial entrapped air pocket.展开更多
A mathematical model is presented for transient flow in a rapidly filling pipeline with an entrapped air pocket. The influence of transient shear stress between the pipe wall and the flowing fluid is taken into accoun...A mathematical model is presented for transient flow in a rapidly filling pipeline with an entrapped air pocket. The influence of transient shear stress between the pipe wall and the flowing fluid is taken into account. A coordinate transformation technique is employed to generate adaptive moving meshes for the multiphase flow system as images of the time-independent computational meshes in auxiliary domains. The method of characteristics is used to reduce the coupled nonlinear hyperbolic partial differential equations governing the motion of the filling fluid, entrapped air, and blocking fluid to ordinary differential equations. Numerical solution of resulting equations shows that the transient shear stresses have only a small damping effect on the pressure fluctuations. The peak pressure in the entrapped air pocket decreases significantly with increasing initial entrapped air volume, but decreases slightly with increasing initial entrapped air pressure.展开更多
文摘Computational Fluid Dynamics(CFD)investigations into water entry problems of a rigid flat plate with air pockets were systematically conducted.The Volume of Fluid(VOF)model was utilised to capture localised slamming phenomena that occur during,and post-impact events.The model’s geometry was modified to include a pocket on the slamming impact surface to investigate the effect of air entrapment on the magnitude and distribution of slamming forces and pressures.A parametric study was conducted on the geometric parameters of the modelled pocket by altering its area,depth,and volume to exam-ine the response of slamming force and pressure loading under several impact velocities.The numerical results of slamming forces and pressures were in good agreement with experimental drop test measure-ments(with relative error of-6%and 7%for the magnitude of slamming force and pressure,respectively).The numerical results proved that the peak pressure is proportional to the magnitude of impact velocity squared(p maxαv^(2)).
文摘A mathematical model is presented for the charging-up process in an air-entrapped pipeline with moving boundary conditions. A coordinate transformation technique is employed to reduce fluid motion in time-dependent domains to ones in time-independent domains. The nonlinear hyperbolic partial differential equations governing the unsteady motion of fluid combined with an equation for transient shear stress between the pipe wall and the flowing fluid are solved by the method of lines. Results show that ignoring elastic effects overestimates the maximum pressure and underestimates the maximum front velocity of filling fluid. The peak pressure of the entrapped air is sensitive to the length of the initial entrapped air pocket.
文摘A mathematical model is presented for transient flow in a rapidly filling pipeline with an entrapped air pocket. The influence of transient shear stress between the pipe wall and the flowing fluid is taken into account. A coordinate transformation technique is employed to generate adaptive moving meshes for the multiphase flow system as images of the time-independent computational meshes in auxiliary domains. The method of characteristics is used to reduce the coupled nonlinear hyperbolic partial differential equations governing the motion of the filling fluid, entrapped air, and blocking fluid to ordinary differential equations. Numerical solution of resulting equations shows that the transient shear stresses have only a small damping effect on the pressure fluctuations. The peak pressure in the entrapped air pocket decreases significantly with increasing initial entrapped air volume, but decreases slightly with increasing initial entrapped air pressure.
