This article presents the direct numerical simulation results of the turbulent flow in a straight square duct at a Reynolds number of 600, based on the duct width and the mean wall-shear velocity. The turbulence stati...This article presents the direct numerical simulation results of the turbulent flow in a straight square duct at a Reynolds number of 600, based on the duct width and the mean wall-shear velocity. The turbulence statistics along the wall bisector is examined with the turbulent flow field properties given by streamwise velocity and vorticity fields in the duct cross section. It was found that the solutions of the turbulent duct flow obtained in a spatial resolution with 1.2×10^6 grid points are satisfactory as compared to the existing numerical and experimental results. The results indicate that it is reasonable to neglect the sub-grid scale models in this spatial resolution level for the duct flow at the particular friction Reynolds number.展开更多
Direct numerical simulation(DNS)of incompressible flows in a zeropressure gradient turbulent boundary layer(TBL)is conducted by a finite difference method in which a fourth order upwind scheme is applied to discretize...Direct numerical simulation(DNS)of incompressible flows in a zeropressure gradient turbulent boundary layer(TBL)is conducted by a finite difference method in which a fourth order upwind scheme is applied to discretize the convective terms while a re-scaling approach is used to set inlet flow conditions.The Reynolds numbers based on free flow velocity and momentum thickness at the recycle section are respectively 687,1074,and 1430.The DNS has obtained favorable results indicating that the turbulence statistics is quite satisfactory as compared with the existing numerical and experimental results.The three dimensional turbulent structures at the momentum thickness Reynolds number of 1430 in several different instants are illustrated by the iso-surface of swirl strength square(the square of imaginary part of the complex eigenvalue of velocity gradient tensor)together with velocity vectors in three different cross sections.It is found that there are three kinds of vortical structures:quasi-symmetrical and asymmetrical hairpin vortices,and worm-like vortices.The DNS based on the numerical method can certainly reveal the main characteristics of the TBL flows at the given Reynolds numbers.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.10572135)the Research Grants Council of the Hong Kong Special Administrative Region,China (Grant No.PolyU5130/04E)
文摘This article presents the direct numerical simulation results of the turbulent flow in a straight square duct at a Reynolds number of 600, based on the duct width and the mean wall-shear velocity. The turbulence statistics along the wall bisector is examined with the turbulent flow field properties given by streamwise velocity and vorticity fields in the duct cross section. It was found that the solutions of the turbulent duct flow obtained in a spatial resolution with 1.2×10^6 grid points are satisfactory as compared to the existing numerical and experimental results. The results indicate that it is reasonable to neglect the sub-grid scale models in this spatial resolution level for the duct flow at the particular friction Reynolds number.
文摘Direct numerical simulation(DNS)of incompressible flows in a zeropressure gradient turbulent boundary layer(TBL)is conducted by a finite difference method in which a fourth order upwind scheme is applied to discretize the convective terms while a re-scaling approach is used to set inlet flow conditions.The Reynolds numbers based on free flow velocity and momentum thickness at the recycle section are respectively 687,1074,and 1430.The DNS has obtained favorable results indicating that the turbulence statistics is quite satisfactory as compared with the existing numerical and experimental results.The three dimensional turbulent structures at the momentum thickness Reynolds number of 1430 in several different instants are illustrated by the iso-surface of swirl strength square(the square of imaginary part of the complex eigenvalue of velocity gradient tensor)together with velocity vectors in three different cross sections.It is found that there are three kinds of vortical structures:quasi-symmetrical and asymmetrical hairpin vortices,and worm-like vortices.The DNS based on the numerical method can certainly reveal the main characteristics of the TBL flows at the given Reynolds numbers.
