A real free surface boundary condition,taking the viscous effects and surface tension into account,is applied to the nonlinear calculation of wave making resistance.It may provide more information about the character ...A real free surface boundary condition,taking the viscous effects and surface tension into account,is applied to the nonlinear calculation of wave making resistance.It may provide more information about the character of the nonlinear ship wave and be helpful to improving the stability,convergence and local wave profile in potential calculation of the nonlinear ship wave.The wave making calculations for Series 60 are presented.展开更多
We consider the problem of a ship advancing in waves. In this method, the zone of free surface in the vicinity of body is discretized. On the discretized surface, the first-order and second-order derivatives of ship w...We consider the problem of a ship advancing in waves. In this method, the zone of free surface in the vicinity of body is discretized. On the discretized surface, the first-order and second-order derivatives of ship waves are represented by the B-Spline formulae. Different ship waves are approximated by cubic B-spline and the first and second order derivates of incident waves are calculated and compared with analytical value. It approves that this numerical method has sufficient accuracy and can be also applied to approximate the velocity potential on the free surface.展开更多
Adopting complex number theory, a mathematic model of Green function is built for two dimension free water surface, and an analytic expression of Green function is obtained by introducing two parameters. The intrinsic...Adopting complex number theory, a mathematic model of Green function is built for two dimension free water surface, and an analytic expression of Green function is obtained by introducing two parameters. The intrinsic properties of Green function are discussed on vertical line and horizontal line. At last, the derivation expression of Green function is obtained from the formula of Green function.展开更多
Reducing the fuel consumption of ships presents both economic and environmental gains. Although in the past decades,extensive studies were carried out on the flow around ship hull, it is still difficult to calculate t...Reducing the fuel consumption of ships presents both economic and environmental gains. Although in the past decades,extensive studies were carried out on the flow around ship hull, it is still difficult to calculate the flow around the hull while considering propeller interaction. In this paper, the viscous flow around modern ship hulls is computed considering propeller action. In this analysis, the numerical investigation of flow around the ship is combined with propeller theory to simulate the hull-propeller interaction. Various longitudinal positions of the rudder are also analyzed to determine the effect of rudder position on propeller efficiency. First, a numerical study was performed around a bare hull using Shipflow computational fluid dynamics(CFD) code to determine free-surface wave elevation and resistance components.A zonal approach was applied to successively incorporate Bpotential flow solver^ in the region outside the boundary layer and wake, Bboundary layer solver^ in the thin boundary layer region near the ship hull, and BNavier-Stokes solver^in the wake region. Propeller open water characteristics were determined using an open-source MATLAB code Open Prop, which is based on the lifting line theory, for the moderately loaded propeller. The obtained open water test results were specified in the flow module of Shipflow for self-propulsion tests. The velocity field behind the ship was recalculated into an effective wake and given to the propeller code that calculates the propeller load. Once the load was known, it was transferred to the Reynolds-averaged Navier-Stokes(RANS) solver to simulate the propeller action. The interaction between the hull and propeller with different rudder positions was then predicted to improve the propulsive efficiency.展开更多
文摘A real free surface boundary condition,taking the viscous effects and surface tension into account,is applied to the nonlinear calculation of wave making resistance.It may provide more information about the character of the nonlinear ship wave and be helpful to improving the stability,convergence and local wave profile in potential calculation of the nonlinear ship wave.The wave making calculations for Series 60 are presented.
文摘We consider the problem of a ship advancing in waves. In this method, the zone of free surface in the vicinity of body is discretized. On the discretized surface, the first-order and second-order derivatives of ship waves are represented by the B-Spline formulae. Different ship waves are approximated by cubic B-spline and the first and second order derivates of incident waves are calculated and compared with analytical value. It approves that this numerical method has sufficient accuracy and can be also applied to approximate the velocity potential on the free surface.
文摘Adopting complex number theory, a mathematic model of Green function is built for two dimension free water surface, and an analytic expression of Green function is obtained by introducing two parameters. The intrinsic properties of Green function are discussed on vertical line and horizontal line. At last, the derivation expression of Green function is obtained from the formula of Green function.
基金the Committee for Advanced Studies and Research(CASR)Bangladesh University of Engineering and Technology for granting research fundsub-project CP No.2084 of Department of Naval Architecture and Marine Engineering under Higher Education Quality Enhancement Project(HEQEP),UGC,Ministry of Education,Govt.of Bangladesh for providing necessary research facilities during the current research work
文摘Reducing the fuel consumption of ships presents both economic and environmental gains. Although in the past decades,extensive studies were carried out on the flow around ship hull, it is still difficult to calculate the flow around the hull while considering propeller interaction. In this paper, the viscous flow around modern ship hulls is computed considering propeller action. In this analysis, the numerical investigation of flow around the ship is combined with propeller theory to simulate the hull-propeller interaction. Various longitudinal positions of the rudder are also analyzed to determine the effect of rudder position on propeller efficiency. First, a numerical study was performed around a bare hull using Shipflow computational fluid dynamics(CFD) code to determine free-surface wave elevation and resistance components.A zonal approach was applied to successively incorporate Bpotential flow solver^ in the region outside the boundary layer and wake, Bboundary layer solver^ in the thin boundary layer region near the ship hull, and BNavier-Stokes solver^in the wake region. Propeller open water characteristics were determined using an open-source MATLAB code Open Prop, which is based on the lifting line theory, for the moderately loaded propeller. The obtained open water test results were specified in the flow module of Shipflow for self-propulsion tests. The velocity field behind the ship was recalculated into an effective wake and given to the propeller code that calculates the propeller load. Once the load was known, it was transferred to the Reynolds-averaged Navier-Stokes(RANS) solver to simulate the propeller action. The interaction between the hull and propeller with different rudder positions was then predicted to improve the propulsive efficiency.
