A two-dimensional computational model is develope for the calulation of tides, storm surges and otherlong-period waves in coastal and shelf waters. The Partial differental equations are approximated by two sets of dif...A two-dimensional computational model is develope for the calulation of tides, storm surges and otherlong-period waves in coastal and shelf waters. The Partial differental equations are approximated by two sets of difference equations on a space-staggered grid system. Both sets are explicit with one set for water level and x-component velocity, and another for water level and y-component velocity. These two sets are used successively for stepby-step solution in time. An analytical investigation on the linearized sets of the difference equations indicates that thecomputational scheme is unconditionally stable. The model is of second order accuracy both in space and in time andconserves mass and momentum. Simulations of surface elevation caused by periodic forcing in one-opening rectangularbasin with flat topography and by steady wind stress in the basin with flat or slope topography show that the computed results are in excellent agreement with the corresponding analytic solutions. The steady-tate wind-induced setupin a ofed basin with discontinuous topography computed with the present model are also in excellent agreement withthe results from Leendertse's model. Finally, the model is applied to hindcast a storm surge in the South China Seaand reproduces the surge elevation satisfactorily.展开更多
A numerical study of ship-to-ship interaction forces is performed using a commercial CFD code,and the results are compared with experimental data and with the results of a panel method analysis.Two ship models have be...A numerical study of ship-to-ship interaction forces is performed using a commercial CFD code,and the results are compared with experimental data and with the results of a panel method analysis.Two ship models have been used in the interaction forces analysis:a tug and a tanker,advancing parallel to each other with different lateral distances and two different values of the fluid depth.Computations are carried out with four different flow models:inviscid and viscous flow with the free surface modeled as a rigid wall and inviscid and viscous flow with the deformable free surface.A fair agreement was obtained with available experimental data and results obtained by panel method.The influence of viscosity in the computations is found to be comparatively weak,while the wavemaking effects may be important,at small magnitude of the horizontal clearance.展开更多
Ships sailing in shallow and/or confined water(when calling a harbour or other berthing areas),will experience a different behaviour due to the interaction with vertical and/or horizontal boundaries.Among other hydrod...Ships sailing in shallow and/or confined water(when calling a harbour or other berthing areas),will experience a different behaviour due to the interaction with vertical and/or horizontal boundaries.Among other hydrodynamic changes induced in confined water,the lateral ship-bank interaction force changes its sign at a critical distance between ship and bank or bottom.However,this distance and its effects on model test results have not been quantified in the past.To investigate the shallow water hydrodynamics coupled with bank effects,systematic model tests were carried out at Flanders Hydraulics Research(FHR)with different ship models.The following parameters were systematically varied:water depth,lateral position,speed,and propeller rate.The change of the ship-bank induced lateral force from an attraction force in medium-deep and shallow water to a repulsion force in extremely shallow water conditions,can be ascribed to the interaction of the boundary layers of the ship model and the environment(tank and installed banks).In this article,a mathematical model is proposed for the critical distance in terms of boundary layer influence thickness.This indicates the range where the model tests are influenced by the horizontal or vertical restrictions combined with the propeller’s dynamic effects.Moreover,the expression has also been extended to describe the relationship between full-scale ship length and water depth with the boundary layer influence thickness.Due to lower Reynolds numbers and relatively thicker boundary layers at model scale,upscaling of the model test results,according to Froude’s law,may provide erroneous results.The influence of the boundary layer initiates at a relatively higher under keel clearance(UKC)for a smaller ship model compared with a larger ship model.Therefore,the boundary layer’s influence with respect to ship model length should be considered during model testing.展开更多
In view of the disastrous consequences of tailings dam break and its unique evolutionary process in complex areas,this paper constructs two-dimensional shallow water equations,rheological equations and mathematical mo...In view of the disastrous consequences of tailings dam break and its unique evolutionary process in complex areas,this paper constructs two-dimensional shallow water equations,rheological equations and mathematical models of tailings sand flows on the basis of Navier–Stokes equations(N–S equations).It performs total variation diminishing(TVD)discretization on these equations,develops forward simulation programs in MATLAB2016 and conducts numerical analyses on three kinds of dam breaks(ideal dam break,asymmetric dam break and dam break with obstacles in the downstream area).The results show that TVD discretization is effective in capturing shock waves.According to the analysis on consequences of Huangmailing Tailings Dam break,the author obtains the maximum distance of tailings sand flow,the flow rate of tailings and the time that tailings reach destinations in the downstream area,thereby providing scientific basis for disaster analyses on similar tailings dam breaks and supplying technical support for emergency rescues after disasters.展开更多
文摘A two-dimensional computational model is develope for the calulation of tides, storm surges and otherlong-period waves in coastal and shelf waters. The Partial differental equations are approximated by two sets of difference equations on a space-staggered grid system. Both sets are explicit with one set for water level and x-component velocity, and another for water level and y-component velocity. These two sets are used successively for stepby-step solution in time. An analytical investigation on the linearized sets of the difference equations indicates that thecomputational scheme is unconditionally stable. The model is of second order accuracy both in space and in time andconserves mass and momentum. Simulations of surface elevation caused by periodic forcing in one-opening rectangularbasin with flat topography and by steady wind stress in the basin with flat or slope topography show that the computed results are in excellent agreement with the corresponding analytic solutions. The steady-tate wind-induced setupin a ofed basin with discontinuous topography computed with the present model are also in excellent agreement withthe results from Leendertse's model. Finally, the model is applied to hindcast a storm surge in the South China Seaand reproduces the surge elevation satisfactorily.
基金the project PTDC/EMSTRA/5628/2014 "Maneuvering and moored ships in ports-physical and numerical modeling,"funded by the Portuguese Foundation for Science and Technology(FCT)financed by FCT under contract number SFRH/BD/67070/2009
文摘A numerical study of ship-to-ship interaction forces is performed using a commercial CFD code,and the results are compared with experimental data and with the results of a panel method analysis.Two ship models have been used in the interaction forces analysis:a tug and a tanker,advancing parallel to each other with different lateral distances and two different values of the fluid depth.Computations are carried out with four different flow models:inviscid and viscous flow with the free surface modeled as a rigid wall and inviscid and viscous flow with the deformable free surface.A fair agreement was obtained with available experimental data and results obtained by panel method.The influence of viscosity in the computations is found to be comparatively weak,while the wavemaking effects may be important,at small magnitude of the horizontal clearance.
文摘Ships sailing in shallow and/or confined water(when calling a harbour or other berthing areas),will experience a different behaviour due to the interaction with vertical and/or horizontal boundaries.Among other hydrodynamic changes induced in confined water,the lateral ship-bank interaction force changes its sign at a critical distance between ship and bank or bottom.However,this distance and its effects on model test results have not been quantified in the past.To investigate the shallow water hydrodynamics coupled with bank effects,systematic model tests were carried out at Flanders Hydraulics Research(FHR)with different ship models.The following parameters were systematically varied:water depth,lateral position,speed,and propeller rate.The change of the ship-bank induced lateral force from an attraction force in medium-deep and shallow water to a repulsion force in extremely shallow water conditions,can be ascribed to the interaction of the boundary layers of the ship model and the environment(tank and installed banks).In this article,a mathematical model is proposed for the critical distance in terms of boundary layer influence thickness.This indicates the range where the model tests are influenced by the horizontal or vertical restrictions combined with the propeller’s dynamic effects.Moreover,the expression has also been extended to describe the relationship between full-scale ship length and water depth with the boundary layer influence thickness.Due to lower Reynolds numbers and relatively thicker boundary layers at model scale,upscaling of the model test results,according to Froude’s law,may provide erroneous results.The influence of the boundary layer initiates at a relatively higher under keel clearance(UKC)for a smaller ship model compared with a larger ship model.Therefore,the boundary layer’s influence with respect to ship model length should be considered during model testing.
文摘In view of the disastrous consequences of tailings dam break and its unique evolutionary process in complex areas,this paper constructs two-dimensional shallow water equations,rheological equations and mathematical models of tailings sand flows on the basis of Navier–Stokes equations(N–S equations).It performs total variation diminishing(TVD)discretization on these equations,develops forward simulation programs in MATLAB2016 and conducts numerical analyses on three kinds of dam breaks(ideal dam break,asymmetric dam break and dam break with obstacles in the downstream area).The results show that TVD discretization is effective in capturing shock waves.According to the analysis on consequences of Huangmailing Tailings Dam break,the author obtains the maximum distance of tailings sand flow,the flow rate of tailings and the time that tailings reach destinations in the downstream area,thereby providing scientific basis for disaster analyses on similar tailings dam breaks and supplying technical support for emergency rescues after disasters.
