A combination of methods was developed that can determine hydrodynamic forces on a planing hull in steady motion.Firstly,a potential-based boundary-element method was used to calculate the hydrodynamic pressure,induce...A combination of methods was developed that can determine hydrodynamic forces on a planing hull in steady motion.Firstly,a potential-based boundary-element method was used to calculate the hydrodynamic pressure,induced resistance and lift.Then the frictional resistance component was determined by the viscous boundary layer theory.Finally,a particular empirical technique was applied.to determine the region of upwash geometry and determine spray resistance.Case studies involving four models of Series 62 planing craft were run.These showed that the suggested method is efficient and capable,with results that are in good agreement with experimental measurements over a wide range of volumetric Froude numbers.展开更多
For purpose of easy identification of the role of free vortices on the lift and drag and for purpose of fast or engineering evaluation of forces for each individual body, we will extend in this paper the Kutta-Joukows...For purpose of easy identification of the role of free vortices on the lift and drag and for purpose of fast or engineering evaluation of forces for each individual body, we will extend in this paper the Kutta-Joukowski （K J） theorem to the case of inviscid flow with multiple free vortices and multiple airfoils. The major simplification used in this paper is that each airfoil is represented by a lumped vortex, which may hold true when the distances between vortices and bodies are large enough. It is found that the Kutta-Joukowski theorem still holds provided that the local freestream velocity and the circulation of the bound vortex are modified by the induced velocity due to the out- side vortices and airfoils. We will demonstrate how to use the present result to identify the role of vortices on the forces according to their position, strength and rotation direction. Moreover, we will apply the present results to a two-cylinder example of Crowdy and the Wagner example to demon- strate how to perform fast force approximation for multi-body and multi-vortex problems. The lumped vortex assumption has the advantage of giving such kinds of approximate results which are very easy to use. The lack of accuracy for such a fast evaluation will be compensated by a rig- orous extension, with the lumped vortex assumption removed and with vortex production included, in a forthcoming paper.展开更多
文摘A combination of methods was developed that can determine hydrodynamic forces on a planing hull in steady motion.Firstly,a potential-based boundary-element method was used to calculate the hydrodynamic pressure,induced resistance and lift.Then the frictional resistance component was determined by the viscous boundary layer theory.Finally,a particular empirical technique was applied.to determine the region of upwash geometry and determine spray resistance.Case studies involving four models of Series 62 planing craft were run.These showed that the suggested method is efficient and capable,with results that are in good agreement with experimental measurements over a wide range of volumetric Froude numbers.
基金supported by National Basic Research Program of China (2012CB720205)
文摘For purpose of easy identification of the role of free vortices on the lift and drag and for purpose of fast or engineering evaluation of forces for each individual body, we will extend in this paper the Kutta-Joukowski （K J） theorem to the case of inviscid flow with multiple free vortices and multiple airfoils. The major simplification used in this paper is that each airfoil is represented by a lumped vortex, which may hold true when the distances between vortices and bodies are large enough. It is found that the Kutta-Joukowski theorem still holds provided that the local freestream velocity and the circulation of the bound vortex are modified by the induced velocity due to the out- side vortices and airfoils. We will demonstrate how to use the present result to identify the role of vortices on the forces according to their position, strength and rotation direction. Moreover, we will apply the present results to a two-cylinder example of Crowdy and the Wagner example to demon- strate how to perform fast force approximation for multi-body and multi-vortex problems. The lumped vortex assumption has the advantage of giving such kinds of approximate results which are very easy to use. The lack of accuracy for such a fast evaluation will be compensated by a rig- orous extension, with the lumped vortex assumption removed and with vortex production included, in a forthcoming paper.
