非惯性系下湍流的计算,对湍流模型的应用一直是一项挑战性的工作.作者提出"扩展内禀平均旋转张量"的概念,并且指出将在惯性系下发展的雷诺应力模型应用于非惯性系下的湍流模拟,非线性湍流模型中的平均旋转张量应该用"扩...非惯性系下湍流的计算,对湍流模型的应用一直是一项挑战性的工作.作者提出"扩展内禀平均旋转张量"的概念,并且指出将在惯性系下发展的雷诺应力模型应用于非惯性系下的湍流模拟,非线性湍流模型中的平均旋转张量应该用"扩展内禀平均旋转张量"替代,从而正确地反映非惯性系诱导的旋转效应.为了验证这一处理方法,采用4个非线性κ-ε模型,对充分发展的旋转槽道流进行了数值模拟.在较广泛的雷诺数和Rossby数范围进行的数值模拟表明,应用该技术途径,非线性κ-ε湍流模型CLS(Craft,Launder and Suga)模型和HM(Huang and Ma)模型可以相当好地捕捉旋转效应及其对湍流结构的影响,因此,可以令人满意地应用于工程湍流的计算.展开更多
The method to calculate the aerodynamic stability derivates of aircrafts by using the sensitivity equations is ex- tended to flows with shock waves in this paper. Using the newly developed second-order cell-centered f...The method to calculate the aerodynamic stability derivates of aircrafts by using the sensitivity equations is ex- tended to flows with shock waves in this paper. Using the newly developed second-order cell-centered finite volume scheme on the unstructured-grid, the unsteady Euler equations and sensitivity equations are solved simultaneously in a non-inertial frame of reference, so that the aerodynamic stability derivatives can be calculated for aircrafts with complex geometries. Based on the numerical results, behavior of the aerodynamic sensitivity parameters near the shock wave is discussed. Furthermore, the stability derivatives are analyzed for supersonic and hypersonic flows. The numerical results of the stability derivatives are found in good agree- ment with theoretical results for supersonic flows, and variations of the aerodynamic force and moment predicted by the stability derivatives are very close to those obtained by CFD simulation for both supersonic and hypersonic flows.展开更多
The pitching motions of supercavitating vehicles could not be avoided due to the lost water buoyancy.In order to have some insight for the design of the supercavitating vehicles,the fixed frequency and free pitching m...The pitching motions of supercavitating vehicles could not be avoided due to the lost water buoyancy.In order to have some insight for the design of the supercavitating vehicles,the fixed frequency and free pitching motions are investigated.A numerical predicting method based on the relative motion principle and the non-inertia coordinate system is proposed to simulate the free pitching motions of supercavitating vehicles in the longitudinal plane.Homogeneous and two fluid multiphase models are used to predict the natural and the ventilated supercavitating flows.In the fixed frequency pitching motions,a variety of working conditions are considered,including the pitching angular velocities and the supercavity scales and the results are found to be consistent with the available experimental results in literature.The mesh deformation technology controlled by the moment of momentum equation is adopted to study the free pitching motions and finally to obtain the planing states proposed by Savchenko.The numerical method is validated for predicting the pitching motions of supercavitating vehicles and is found to enjoy better calculation efficiency as comparing with the mesh regeneration technology.展开更多
文摘非惯性系下湍流的计算,对湍流模型的应用一直是一项挑战性的工作.作者提出"扩展内禀平均旋转张量"的概念,并且指出将在惯性系下发展的雷诺应力模型应用于非惯性系下的湍流模拟,非线性湍流模型中的平均旋转张量应该用"扩展内禀平均旋转张量"替代,从而正确地反映非惯性系诱导的旋转效应.为了验证这一处理方法,采用4个非线性κ-ε模型,对充分发展的旋转槽道流进行了数值模拟.在较广泛的雷诺数和Rossby数范围进行的数值模拟表明,应用该技术途径,非线性κ-ε湍流模型CLS(Craft,Launder and Suga)模型和HM(Huang and Ma)模型可以相当好地捕捉旋转效应及其对湍流结构的影响,因此,可以令人满意地应用于工程湍流的计算.
文摘The method to calculate the aerodynamic stability derivates of aircrafts by using the sensitivity equations is ex- tended to flows with shock waves in this paper. Using the newly developed second-order cell-centered finite volume scheme on the unstructured-grid, the unsteady Euler equations and sensitivity equations are solved simultaneously in a non-inertial frame of reference, so that the aerodynamic stability derivatives can be calculated for aircrafts with complex geometries. Based on the numerical results, behavior of the aerodynamic sensitivity parameters near the shock wave is discussed. Furthermore, the stability derivatives are analyzed for supersonic and hypersonic flows. The numerical results of the stability derivatives are found in good agree- ment with theoretical results for supersonic flows, and variations of the aerodynamic force and moment predicted by the stability derivatives are very close to those obtained by CFD simulation for both supersonic and hypersonic flows.
基金Project support by the Major National Natural Science Founation of China(Grant No.10832007)
文摘The pitching motions of supercavitating vehicles could not be avoided due to the lost water buoyancy.In order to have some insight for the design of the supercavitating vehicles,the fixed frequency and free pitching motions are investigated.A numerical predicting method based on the relative motion principle and the non-inertia coordinate system is proposed to simulate the free pitching motions of supercavitating vehicles in the longitudinal plane.Homogeneous and two fluid multiphase models are used to predict the natural and the ventilated supercavitating flows.In the fixed frequency pitching motions,a variety of working conditions are considered,including the pitching angular velocities and the supercavity scales and the results are found to be consistent with the available experimental results in literature.The mesh deformation technology controlled by the moment of momentum equation is adopted to study the free pitching motions and finally to obtain the planing states proposed by Savchenko.The numerical method is validated for predicting the pitching motions of supercavitating vehicles and is found to enjoy better calculation efficiency as comparing with the mesh regeneration technology.
