Despite being one of the oldest and most widely-used turbulence models in engineering computational fluid dynamics(CFD),the k-ωmodel has not been fully understood theoretically because of its high nonlinearity and co...Despite being one of the oldest and most widely-used turbulence models in engineering computational fluid dynamics(CFD),the k-ωmodel has not been fully understood theoretically because of its high nonlinearity and complex model parameter setting.Here,a multi-layer analytic expression is postulated for two lengths(stress and kinetic energy lengths),yielding an analytic solution for the k-ωmodel equations in pipe flow.Approximate local balance equations are analyzed to determine the key parameters in the solution,which are shown to be rather close to the empirically-measured values from the numerical solution of the Wilcox k-ωmodel,and hence the analytic construction is fully validated.The results provide clear evidence that the k-ωmodel sets in it a multilayer structure,which is similar to but different,in some insignificant details,from the Navier-Stokes(N-S)turbulence.This finding explains why the k-ωmodel is so popular,especially in computing the near-wall flow.Finally,the analysis is extended to a newlyrefined k-ωmodel called the structural ensemble dynamics(SED)k-ωmodel,showing that the SED k-ωmodel has improved the multi-layer structure in the outer flow but preserved the setting of the k-ωmodel in the inner region.展开更多
采用流体体积(Volume of Fluid,VOF)水土两相流模型、SST k-ω湍流模型和Herschel-Bulkley模型建立二维海底管道局部冲刷数值模型,模拟黏土质海床管道冲刷,并对管道局部冲刷剖面、升力系数、冲刷坑最大深度等进行对比研究,分析阻流器不...采用流体体积(Volume of Fluid,VOF)水土两相流模型、SST k-ω湍流模型和Herschel-Bulkley模型建立二维海底管道局部冲刷数值模型,模拟黏土质海床管道冲刷,并对管道局部冲刷剖面、升力系数、冲刷坑最大深度等进行对比研究,分析阻流器不同安装位置和长度对管道冲刷特性的影响机制。结果表明:安装于管道正上方的阻流器会加剧管道局部冲刷,而且随着阻流器长度的增加,管道局部冲刷坑最大深度和宽度均增加;安装于管道后方且平行于来流方向的阻流器有助于抑制管道局部冲刷,冲刷坑最大深度和宽度均减小;安装于管道底部的双向刚性阻流器可有效避免管道局部冲刷的发生,当双向刚性阻流器长度在3 D及以上时,管道局部冲刷基本不再发生。展开更多
基金the National Numerical Wind Tunnel(No.NNW2019ZT1-A03)the National Natural Science Foundation of China(Nos.91952201,11372008,and 11452002)。
文摘Despite being one of the oldest and most widely-used turbulence models in engineering computational fluid dynamics(CFD),the k-ωmodel has not been fully understood theoretically because of its high nonlinearity and complex model parameter setting.Here,a multi-layer analytic expression is postulated for two lengths(stress and kinetic energy lengths),yielding an analytic solution for the k-ωmodel equations in pipe flow.Approximate local balance equations are analyzed to determine the key parameters in the solution,which are shown to be rather close to the empirically-measured values from the numerical solution of the Wilcox k-ωmodel,and hence the analytic construction is fully validated.The results provide clear evidence that the k-ωmodel sets in it a multilayer structure,which is similar to but different,in some insignificant details,from the Navier-Stokes(N-S)turbulence.This finding explains why the k-ωmodel is so popular,especially in computing the near-wall flow.Finally,the analysis is extended to a newlyrefined k-ωmodel called the structural ensemble dynamics(SED)k-ωmodel,showing that the SED k-ωmodel has improved the multi-layer structure in the outer flow but preserved the setting of the k-ωmodel in the inner region.
文摘采用流体体积(Volume of Fluid,VOF)水土两相流模型、SST k-ω湍流模型和Herschel-Bulkley模型建立二维海底管道局部冲刷数值模型,模拟黏土质海床管道冲刷,并对管道局部冲刷剖面、升力系数、冲刷坑最大深度等进行对比研究,分析阻流器不同安装位置和长度对管道冲刷特性的影响机制。结果表明:安装于管道正上方的阻流器会加剧管道局部冲刷,而且随着阻流器长度的增加,管道局部冲刷坑最大深度和宽度均增加;安装于管道后方且平行于来流方向的阻流器有助于抑制管道局部冲刷,冲刷坑最大深度和宽度均减小;安装于管道底部的双向刚性阻流器可有效避免管道局部冲刷的发生,当双向刚性阻流器长度在3 D及以上时,管道局部冲刷基本不再发生。
