A new numerical method was developed for predicting the steady hydrodynamic performance of ducted propellers. A potential based surface panel method was applied both to the duct and the propeller, and the interaction ...A new numerical method was developed for predicting the steady hydrodynamic performance of ducted propellers. A potential based surface panel method was applied both to the duct and the propeller, and the interaction between them was solved by an induced velocity potential iterative method. Compared with the induced velocity iterative method, the method presented can save programming and calculating time. Numerical results for a JD simplified ducted propeller series showed that the method presented is effective for predicting the steady hydrodynamic performance of ducted propellers.展开更多
The potential based low order surface panel method is used to predict the hydrodynamic performance of marine propellers. In present method the hyperboloidal quadrilateral panels are employed to avoid the gap between t...The potential based low order surface panel method is used to predict the hydrodynamic performance of marine propellers. In present method the hyperboloidal quadrilateral panels are employed to avoid the gap between the panels. The influence coefficients of panels are calculated by Morino’s analytical formulations for increasing numerically calculating speed. The pressure Kutta condition is satisfied on the trailing edge of propeller blade by Newton-Raphson iterative procedure. Therefore the pressure coefficients of the suction and pressure faces of blade are equal on trailing edge. The method developed by Yanagizawa is used to determine the velocities on propeller surface, and to avoid the singularity in the numerical differentiation. The predicted pressure distributions and open water performances of general propellers and highly skewed propellers have a good agreement with experimental dat and other calculation results.展开更多
In conventional marine seismic exploration data processing,the sea surface is usually treated as a horizontal free boundary.However,the sea surface is affected by wind and waves and there often exists dynamic small-ra...In conventional marine seismic exploration data processing,the sea surface is usually treated as a horizontal free boundary.However,the sea surface is affected by wind and waves and there often exists dynamic small-range fluctuations.These dynamic fluctuations will change the energy propagation path and affect the final imaging results.In theoretical research,different sea surface conditions need to be described,so it is necessary to study the modeling method of dynamic undulating sea surface.Starting from the commonly used sea surface mathematical simulation methods,this paper mainly studies the realization process of simple harmonic wave and Gerstner wave sea surface simulation methods based on ocean wave spectrum,and compares their advantages and disadvantages.Aiming at the shortcomings of the simple harmonic method and Gerstner method in calculational speed and sea surface simulation effect,a method based on wave equation and using dynamic boundary conditions for sea surface simulation is proposed.The calculational speed of this method is much faster than the commonly used simple harmonic method and Gerstner wave method.In addition,this paper also compares the new method with the more commonly used higher-order spectral methods to show the characteristics of the improved wave equation method.展开更多
A doublet integral equation is formulated for the two-dimensional dissipative potential flow around a hydrofoil submerged below a free-water surface. The free-water surface is assumed to involve energy dissipation, an...A doublet integral equation is formulated for the two-dimensional dissipative potential flow around a hydrofoil submerged below a free-water surface. The free-water surface is assumed to involve energy dissipation, and thus it is the source of damping. A doublet panel method is developed from incorporation of the dissipative Green function approach and the doublet distributions on the hydrofoil surface. Numerical computations are implemented, and the derived numerical results are in good agreement with analytic solutions and experimental measurements.展开更多
This paper has predicted the range and volume of unsteady sheet cavitation of a propeller by using the surface panel method. The linearization in cavity thickness is adopted to reduce the computing time and storage sp...This paper has predicted the range and volume of unsteady sheet cavitation of a propeller by using the surface panel method. The linearization in cavity thickness is adopted to reduce the computing time and storage space. The iteration scheme between chordwise strips has been used because the range and volume of cavitation are both unknown. The propeller cavitation range determined by the calculation method presented in this paper agrees with the observation results of cavity image at cavitation tunnel very well, and this proves the practicability of the method.展开更多
The unsteady sheet cavitation of podded propeller was predicted by using a surface panel method. The interaction between propeller and pod was treated with the iterative calculation of induced velocity potential, and ...The unsteady sheet cavitation of podded propeller was predicted by using a surface panel method. The interaction between propeller and pod was treated with the iterative calculation of induced velocity potential, and the method of induced velocity potential can save a great deal of storage and computation time compared to the method of induced velocity. The induced velocity potential of unit singularity on every pod panel to every key blade panel and of unit singularity on every key blade panel and its wake panel to every pod panel were calculated when the key blade is at every angle position. Based on the wake model of the conventional single propeller, a new wake model of podded propeller was constructed. The propeller is analyzed only on the key blade in order to save computation time and memory space. The method can be used to calculate the hydrodynamics performance and cavitation of propeller in uniform and non-uniform inflows. It can give the unsteady force and cavitation shape of propeller. The propeller cavitation range determined by the present method agrees with the observation results of cavity image given in cavitation tunnel well, and this proves the practicability of the method.展开更多
A method for static aeroelastic analysis based on the high-order panel method and modal method is presented. The static aeroelastic characteristics of flexible wings are investigated using this method. Three-dimension...A method for static aeroelastic analysis based on the high-order panel method and modal method is presented. The static aeroelastic characteristics of flexible wings are investigated using this method. Three-dimensional aerodynamic models of flexible wings are constructed based on the geometry of wing configuration, and the modal method is adopted to achieve the fluid-structure coupling. The static aeroelastic characteristics of the AGARD445.6 wing and a low-aspect-ratio wing are investigated in this study. The influences of elastic structural deformation on aerodynamic forces are studied with an emphasis analyzing the aerodynamic coefficients, wing root loads, structural deformation and pressure distribution of different sections, and results are compared with the results from wind-tunnel tests and the elastic results based on experimental aerodynamic forces. It is concluded that aerodynamic forces can be accurately calculated with the high-order panel method. The method presented in this study is feasible, credible and efficient. Comprehensive static aeroelastic characteristics can be provided by the method for early phases of aircraft design.展开更多
A three-dimensional high-order panel method based on non-uniform rational B-spline(NURBS) is developed for predicting the hydrodynamic interaction forces on a moored ship induced by a passing ship in shallow water. An...A three-dimensional high-order panel method based on non-uniform rational B-spline(NURBS) is developed for predicting the hydrodynamic interaction forces on a moored ship induced by a passing ship in shallow water. An NURBS surface is used to precisely represent the hull geometry. Velocity potential on the hull surface is described by B-spline after the source density distribution on the boundary surface is determined. A collocation approach is applied to the boundary integral equation discretization. Under the assumption of low passing speed, the effect of free surface elevation is neglected in the numerical calculation, and infinite image method is used to deal with the finite water depth effect. The time stepping method is used to solve the velocity potential at each time step. Detailed convergence study with respect to time step, panel size and Green function is undertaken. The present results of hydrodynamic forces are compared with those obtained by slender-body theory to show the validity of the proposed numerical method. Calculations are conducted for different water depths and lateral distances between ships, and the detail results are presented to demonstrate the effects of these factors.展开更多
The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with consta...The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with constant source and doublet distribution. Each panel＇s comer coordinates were calculated by spline interpolation between the main parameter and the blade geometry of the propeller. The integral equation was derived using the Green Formula. The influence coefficient of the matrix was calculated by the Morino analytic formula. The tangential velocity distribution was calculated with the Yanagizawa method, and the pressure coefficient was calculated using the Bonuli equation. The pressure Kutta condition was satisfied at the trailing edge of the propeller blade using the Newton-Raphson iterative procedure, so as to make the pressure coefficients of the suction and pressure faces of the blade equal at the trailing edge. Calculated results for the propeller in steady inflow were taken as initialization values for the unsteady inflow calculation process. Calculations were carried out from the moment the propeller achieved steady rotation. At each time interval, a linear algebraic equation combined with Kutta condition was established on a key blade and solved numerically. Comparison between calculated results and experimental results indicates that this method is correct and effective.展开更多
A raised panel method based on NURBS (Non-Uniform Rational B-Splines) forfree-surface flows with forward speed is presented. In this generalized panel method, NURBS areemployed to represent the body geometry, disturbe...A raised panel method based on NURBS (Non-Uniform Rational B-Splines) forfree-surface flows with forward speed is presented. In this generalized panel method, NURBS areemployed to represent the body geometry, disturbed free surface, and to express the unknown sourcestrength distribution, on the body surface and above the free surface. Compared with commonhigher-order panel methods, it has no need of adopting local coordinates. NURBS make the geometryrepresentation of the body shape and the wave pattern more precise. Raised panels above the freesurface produce less numerical dispersion error, need less CPU consumption and are helpful andcombined with collocation-point shifting up-stream, can satisfy the radiation condition numerically.By using continuous and discrete Fourier analysis, numerical errors of this method are discussedand a general expression for the errors of numerical damping and dispersion, including the effectsof the vertical distance of singularities to the free surface, the order of singularity distributionrepresented by B-splines in panels, and collocation-point shifting is derived.展开更多
An optimal marine propeller design method is proposed,which integrates the lifting line and surface panel method and is characterized by the use of the surface panel method to take the hub effect into consideration.By...An optimal marine propeller design method is proposed,which integrates the lifting line and surface panel method and is characterized by the use of the surface panel method to take the hub effect into consideration.By developing an integrated approach instead of an iterative method for the calculation of the interaction between the hub and the designed blades,the hub effects on the optimal circulation can be accounted for throughout the theoretical design procedure.This new integrated method provides a fast and accurate enough method to model the straight forward hub surface,in the optimal propeller design.A systematic design procedure from the basic design inputs to the blade geometry determination is performed and the designed propellers are validated by the surface panel method and the RANS method.The design and analysis cases are considered by different approaches with comparison and validation.And a comparative study including different hub geometries is also performed to reveal the mechanism of the hub effect on the distributions of the propeller optimal loads.展开更多
基金Supported by the Open Research Foundation of State Key Laboratory of AUV,HEU under Grant No.2007015
文摘A new numerical method was developed for predicting the steady hydrodynamic performance of ducted propellers. A potential based surface panel method was applied both to the duct and the propeller, and the interaction between them was solved by an induced velocity potential iterative method. Compared with the induced velocity iterative method, the method presented can save programming and calculating time. Numerical results for a JD simplified ducted propeller series showed that the method presented is effective for predicting the steady hydrodynamic performance of ducted propellers.
文摘The potential based low order surface panel method is used to predict the hydrodynamic performance of marine propellers. In present method the hyperboloidal quadrilateral panels are employed to avoid the gap between the panels. The influence coefficients of panels are calculated by Morino’s analytical formulations for increasing numerically calculating speed. The pressure Kutta condition is satisfied on the trailing edge of propeller blade by Newton-Raphson iterative procedure. Therefore the pressure coefficients of the suction and pressure faces of blade are equal on trailing edge. The method developed by Yanagizawa is used to determine the velocities on propeller surface, and to avoid the singularity in the numerical differentiation. The predicted pressure distributions and open water performances of general propellers and highly skewed propellers have a good agreement with experimental dat and other calculation results.
基金The General Program of National Natural Science Foundation of China under contract No.42074150the National Key Research and Development Project under contract No.2017YFC0601305。
文摘In conventional marine seismic exploration data processing,the sea surface is usually treated as a horizontal free boundary.However,the sea surface is affected by wind and waves and there often exists dynamic small-range fluctuations.These dynamic fluctuations will change the energy propagation path and affect the final imaging results.In theoretical research,different sea surface conditions need to be described,so it is necessary to study the modeling method of dynamic undulating sea surface.Starting from the commonly used sea surface mathematical simulation methods,this paper mainly studies the realization process of simple harmonic wave and Gerstner wave sea surface simulation methods based on ocean wave spectrum,and compares their advantages and disadvantages.Aiming at the shortcomings of the simple harmonic method and Gerstner method in calculational speed and sea surface simulation effect,a method based on wave equation and using dynamic boundary conditions for sea surface simulation is proposed.The calculational speed of this method is much faster than the commonly used simple harmonic method and Gerstner wave method.In addition,this paper also compares the new method with the more commonly used higher-order spectral methods to show the characteristics of the improved wave equation method.
文摘A doublet integral equation is formulated for the two-dimensional dissipative potential flow around a hydrofoil submerged below a free-water surface. The free-water surface is assumed to involve energy dissipation, and thus it is the source of damping. A doublet panel method is developed from incorporation of the dissipative Green function approach and the doublet distributions on the hydrofoil surface. Numerical computations are implemented, and the derived numerical results are in good agreement with analytic solutions and experimental measurements.
文摘This paper has predicted the range and volume of unsteady sheet cavitation of a propeller by using the surface panel method. The linearization in cavity thickness is adopted to reduce the computing time and storage space. The iteration scheme between chordwise strips has been used because the range and volume of cavitation are both unknown. The propeller cavitation range determined by the calculation method presented in this paper agrees with the observation results of cavity image at cavitation tunnel very well, and this proves the practicability of the method.
基金Project supported by the Research Foundation of the Ministry of Education Key Laboratory of High Speed Ship Engineering(Grant No. HSSE0803).
文摘The unsteady sheet cavitation of podded propeller was predicted by using a surface panel method. The interaction between propeller and pod was treated with the iterative calculation of induced velocity potential, and the method of induced velocity potential can save a great deal of storage and computation time compared to the method of induced velocity. The induced velocity potential of unit singularity on every pod panel to every key blade panel and of unit singularity on every key blade panel and its wake panel to every pod panel were calculated when the key blade is at every angle position. Based on the wake model of the conventional single propeller, a new wake model of podded propeller was constructed. The propeller is analyzed only on the key blade in order to save computation time and memory space. The method can be used to calculate the hydrodynamics performance and cavitation of propeller in uniform and non-uniform inflows. It can give the unsteady force and cavitation shape of propeller. The propeller cavitation range determined by the present method agrees with the observation results of cavity image given in cavitation tunnel well, and this proves the practicability of the method.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60736025, 90716006 and 10902006)the Doctoral Program Foundation of Institutions of Higher Education of China (Grant No. 20091102110015)the Major Programs of China National Space Administration (Grant No. D2120060013)
文摘A method for static aeroelastic analysis based on the high-order panel method and modal method is presented. The static aeroelastic characteristics of flexible wings are investigated using this method. Three-dimensional aerodynamic models of flexible wings are constructed based on the geometry of wing configuration, and the modal method is adopted to achieve the fluid-structure coupling. The static aeroelastic characteristics of the AGARD445.6 wing and a low-aspect-ratio wing are investigated in this study. The influences of elastic structural deformation on aerodynamic forces are studied with an emphasis analyzing the aerodynamic coefficients, wing root loads, structural deformation and pressure distribution of different sections, and results are compared with the results from wind-tunnel tests and the elastic results based on experimental aerodynamic forces. It is concluded that aerodynamic forces can be accurately calculated with the high-order panel method. The method presented in this study is feasible, credible and efficient. Comprehensive static aeroelastic characteristics can be provided by the method for early phases of aircraft design.
基金the National Natural Science Foundation of China(Nos.51179019 and 51309152)
文摘A three-dimensional high-order panel method based on non-uniform rational B-spline(NURBS) is developed for predicting the hydrodynamic interaction forces on a moored ship induced by a passing ship in shallow water. An NURBS surface is used to precisely represent the hull geometry. Velocity potential on the hull surface is described by B-spline after the source density distribution on the boundary surface is determined. A collocation approach is applied to the boundary integral equation discretization. Under the assumption of low passing speed, the effect of free surface elevation is neglected in the numerical calculation, and infinite image method is used to deal with the finite water depth effect. The time stepping method is used to solve the velocity potential at each time step. Detailed convergence study with respect to time step, panel size and Green function is undertaken. The present results of hydrodynamic forces are compared with those obtained by slender-body theory to show the validity of the proposed numerical method. Calculations are conducted for different water depths and lateral distances between ships, and the detail results are presented to demonstrate the effects of these factors.
基金Supported by the Doctoral Program of Higher Education Foundation under Grant No. 2006021702.
文摘The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with constant source and doublet distribution. Each panel＇s comer coordinates were calculated by spline interpolation between the main parameter and the blade geometry of the propeller. The integral equation was derived using the Green Formula. The influence coefficient of the matrix was calculated by the Morino analytic formula. The tangential velocity distribution was calculated with the Yanagizawa method, and the pressure coefficient was calculated using the Bonuli equation. The pressure Kutta condition was satisfied at the trailing edge of the propeller blade using the Newton-Raphson iterative procedure, so as to make the pressure coefficients of the suction and pressure faces of the blade equal at the trailing edge. Calculated results for the propeller in steady inflow were taken as initialization values for the unsteady inflow calculation process. Calculations were carried out from the moment the propeller achieved steady rotation. At each time interval, a linear algebraic equation combined with Kutta condition was established on a key blade and solved numerically. Comparison between calculated results and experimental results indicates that this method is correct and effective.
文摘A raised panel method based on NURBS (Non-Uniform Rational B-Splines) forfree-surface flows with forward speed is presented. In this generalized panel method, NURBS areemployed to represent the body geometry, disturbed free surface, and to express the unknown sourcestrength distribution, on the body surface and above the free surface. Compared with commonhigher-order panel methods, it has no need of adopting local coordinates. NURBS make the geometryrepresentation of the body shape and the wave pattern more precise. Raised panels above the freesurface produce less numerical dispersion error, need less CPU consumption and are helpful andcombined with collocation-point shifting up-stream, can satisfy the radiation condition numerically.By using continuous and discrete Fourier analysis, numerical errors of this method are discussedand a general expression for the errors of numerical damping and dispersion, including the effectsof the vertical distance of singularities to the free surface, the order of singularity distributionrepresented by B-splines in panels, and collocation-point shifting is derived.
文摘An optimal marine propeller design method is proposed,which integrates the lifting line and surface panel method and is characterized by the use of the surface panel method to take the hub effect into consideration.By developing an integrated approach instead of an iterative method for the calculation of the interaction between the hub and the designed blades,the hub effects on the optimal circulation can be accounted for throughout the theoretical design procedure.This new integrated method provides a fast and accurate enough method to model the straight forward hub surface,in the optimal propeller design.A systematic design procedure from the basic design inputs to the blade geometry determination is performed and the designed propellers are validated by the surface panel method and the RANS method.The design and analysis cases are considered by different approaches with comparison and validation.And a comparative study including different hub geometries is also performed to reveal the mechanism of the hub effect on the distributions of the propeller optimal loads.
