稳定分层流数值模拟方法及圆球绕流特征研究

On the numerical methods of the stable stratified flows and wake characteristics around a sphere

本文通过分析温度、盐度和压力对海水密度的相对影响,利用标准海水状态方程,联合求解温度形式的能量方程,提出一种新的实现温度主导状态下的密度连续分层数值模拟方法。基于有限体积法(FVM),通过求解连续性方程和动量守恒方程,湍流状态时采用基于k-ω湍流模型的脱体涡模拟(DES)方法,对连续分层流中的圆球绕流进行数值模拟,重点分析尾流场的旋涡脱落流动特性及尾涡结构特点。定量分析了尾涡结构中无因次涡包络区长度、涡旋脱落斯特罗哈尔数(St)、无因次化后的Lee波波长和无因次分离流线高度等尾涡流场特征。本文数值结果和Lin的圆球实验结果在定性和定量上保持一致,从而验证了本文建立的数值方法的正确性和有效性,可以为进一步研究密度分层流中潜航体航行尾流场问题提供有效的计算流体力学方法。

This paper discusses the relative influence of temperature,salinity and pressure on the density of seawater and uses the seawater state equation and the energy equation to achieve continuous stratification of the fluid density which is dominated by the temperature.Based on the finite volume method(FVM),the conti⁃nuity equation and the momentum equation are solved by using the detached eddy simulation(DES)method when the flow state is turbulence.The near field of the continuous stratified flow past a sphere is analyzed by adopting the numerical method established in this paper,with focus on the vortex shedding characteristics of the wake field and the characteristics of the wake vortex structure,the results of which show that the wake vortex structure exhibits a quasi-two-dimensional(Quasi-2D)status at low Froude number(Fr)due to the ex⁃istence of vertical stable density stratification,and that the vertical motion of the fluid particle in the wake is suppressed.When the Froude number(Fr)is higher,strong three-dimensional vortex structures and Lee waves appear in the wake field.The present study conducted quantitative researches on the dimensionless vortex envelope,the vortex shedding Strouhal number(St),the dimensionless Lee wave wavelength and the di⁃mensionless separation streamline height.The wake field characteristics are analyzed for different ranges of the Fr and the Re.The numerical results of this paper are consistent with the qualitative and quantitative re⁃sults of Lin’s experiments,verifying and validating the numerical method established in this paper,which can provide an effective computational fluid dynamics method for the further research on the issues of the wake field of submerged body in density stratified flow.