The dissipation function in turbulent plane Poiseuille flows(PPFs) and plane Couette flows(PCFs) subject to spanwise rotations is analyzed. It is found that, in the PCFs without system rotations, the mean part is cons...The dissipation function in turbulent plane Poiseuille flows(PPFs) and plane Couette flows(PCFs) subject to spanwise rotations is analyzed. It is found that, in the PCFs without system rotations, the mean part is constant while the fluctuation part follows a logarithmic law, resulting in a similar logarithmic skin friction law as PPFs.However, if the flow system rotates in the spanwise direction, no obvious dependence on the rotation number can be evaluated. In the PPFs with rotations, the dissipation function shows an increase with the rotation number, while in the PCFs with rotations,when the rotation number increases, the dissipation function first decreases and then increases.展开更多
This paper investigates the linear stability behaviour of plane Poiseuille flow under unsteady distortion by multiscale perturbation method and discusses further the problem proposed by paper [1]. The results show tha...This paper investigates the linear stability behaviour of plane Poiseuille flow under unsteady distortion by multiscale perturbation method and discusses further the problem proposed by paper [1]. The results show that in the initial period of disturbance development, the distortion profiles presented by paper [1] will make the disturbances grow up, thus augmenting the possibility of instability.展开更多
Linear Stability Analysis(LSA)of parallel shear flows,via local and global approaches,is presented.The local analysis is carried out by solving the Orr-Sommerfeld(OS)equation using a spectral-collocation method based ...Linear Stability Analysis(LSA)of parallel shear flows,via local and global approaches,is presented.The local analysis is carried out by solving the Orr-Sommerfeld(OS)equation using a spectral-collocation method based on Chebyshev polynomials.A stabilized finite element formulation is employed to carry out the global analysis using the linearized disturbance equations in primitive variables.The local and global analysis are compared.As per the Squires theorem,the two-dimensional disturbance has the largest growth rate.Therefore,only two-dimensional disturbances are considered.By its very nature,the local analysis assumes the disturbance field to be spatially periodic in the streamwise direction.The global analysis permits a more general disturbance.However,to enable a comparison with the local analysis,periodic boundary conditions,at the inlet and exit of the domain,are imposed on the disturbance.Computations are carried out for the LSA of the Plane Poiseuille Flow(PPF).The relationship between the wavenumber,a,of the disturbance and the streamwise extent of the domain,L,in the global analysis is explored for Re=7000.It is found that a and L are related by L=2pn/a,where n is the number of cells of the instability along the streamwise direction within the domain length,L.The procedure to interpret the results from the global analysis,for comparison with local analysis,is described.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.11772297 and11822208)
文摘The dissipation function in turbulent plane Poiseuille flows(PPFs) and plane Couette flows(PCFs) subject to spanwise rotations is analyzed. It is found that, in the PCFs without system rotations, the mean part is constant while the fluctuation part follows a logarithmic law, resulting in a similar logarithmic skin friction law as PPFs.However, if the flow system rotates in the spanwise direction, no obvious dependence on the rotation number can be evaluated. In the PPFs with rotations, the dissipation function shows an increase with the rotation number, while in the PCFs with rotations,when the rotation number increases, the dissipation function first decreases and then increases.
基金This work is supported by National Science Foundationthe Science Foundation of Shanghai University of Technology
文摘This paper investigates the linear stability behaviour of plane Poiseuille flow under unsteady distortion by multiscale perturbation method and discusses further the problem proposed by paper [1]. The results show that in the initial period of disturbance development, the distortion profiles presented by paper [1] will make the disturbances grow up, thus augmenting the possibility of instability.
文摘Linear Stability Analysis(LSA)of parallel shear flows,via local and global approaches,is presented.The local analysis is carried out by solving the Orr-Sommerfeld(OS)equation using a spectral-collocation method based on Chebyshev polynomials.A stabilized finite element formulation is employed to carry out the global analysis using the linearized disturbance equations in primitive variables.The local and global analysis are compared.As per the Squires theorem,the two-dimensional disturbance has the largest growth rate.Therefore,only two-dimensional disturbances are considered.By its very nature,the local analysis assumes the disturbance field to be spatially periodic in the streamwise direction.The global analysis permits a more general disturbance.However,to enable a comparison with the local analysis,periodic boundary conditions,at the inlet and exit of the domain,are imposed on the disturbance.Computations are carried out for the LSA of the Plane Poiseuille Flow(PPF).The relationship between the wavenumber,a,of the disturbance and the streamwise extent of the domain,L,in the global analysis is explored for Re=7000.It is found that a and L are related by L=2pn/a,where n is the number of cells of the instability along the streamwise direction within the domain length,L.The procedure to interpret the results from the global analysis,for comparison with local analysis,is described.
