Three-dimensional laminar flow in the entrance region of rotating curved pipes was investigated. The governing equations were written in an orthogonal curvilinear coordinate system and solved with a fully three-dimens...Three-dimensional laminar flow in the entrance region of rotating curved pipes was investigated. The governing equations were written in an orthogonal curvilinear coordinate system and solved with a fully three-dimensional numerical method. The development of secondary flow, axial velocity, local and average friction factors for different cases of rotation were given and discussed in detail. The results show that rotation influences the flow structure and friction factor greatly and that the secondary flow is sink-type in the early stage of development and then turns to vortex structure. The average friction factor and the intensity of secondary flow have drastic decrease near the entrance. At some proper rotation, the average friction factor can be noticeably reduced.展开更多
A pertubation method for the steady entrance flow through a convergingdiverging pipe, which can model an arterial stenosis at the initial stage, is presented. Aset of formulas for velocity, pressure and wall shear str...A pertubation method for the steady entrance flow through a convergingdiverging pipe, which can model an arterial stenosis at the initial stage, is presented. Aset of formulas for velocity, pressure and wall shear stress distributions are obtained. Results show that the flow patterns of entrance flow are considerably different from those ofdeveloped flow in a converging-diverging pipe: the velocity distribution at the stenosis issmoother, the centerline velocity decreases, and the wall shear stress and pressure gradient increase in the entrance region. The length of entrance flow for the pipe is slighty lower than that for a straight one with constant cross section. The results are checked by thefinite difference method.展开更多
A fully elliptic numerical study has been carried out to investigate the three-dimensional turbulent developing flow in a helical square duct with large curvature. A two-layer zonal model is proposed and used, in whic...A fully elliptic numerical study has been carried out to investigate the three-dimensional turbulent developing flow in a helical square duct with large curvature. A two-layer zonal model is proposed and used, in which the whole region is divided into a viscosity-affected near wall layer and a fully turbulent region. A DSM closure is applied in the former, and a one-equation model is solved in the latter. The results presented in this paper cover a Reynolds number range of (l- 10) x 104. The development of flow is found to be dominated by radial pressure gradient and Dean-type secondary motion. The distribution of Reynolds stresses in fully developed flow exhibit a complex pattern of turbulence anisotropy The development of peripherally averaged friction factor and the distribution of local friction factor in fully developed flow are given and discussed.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No: 10272096).
文摘Three-dimensional laminar flow in the entrance region of rotating curved pipes was investigated. The governing equations were written in an orthogonal curvilinear coordinate system and solved with a fully three-dimensional numerical method. The development of secondary flow, axial velocity, local and average friction factors for different cases of rotation were given and discussed in detail. The results show that rotation influences the flow structure and friction factor greatly and that the secondary flow is sink-type in the early stage of development and then turns to vortex structure. The average friction factor and the intensity of secondary flow have drastic decrease near the entrance. At some proper rotation, the average friction factor can be noticeably reduced.
文摘A pertubation method for the steady entrance flow through a convergingdiverging pipe, which can model an arterial stenosis at the initial stage, is presented. Aset of formulas for velocity, pressure and wall shear stress distributions are obtained. Results show that the flow patterns of entrance flow are considerably different from those ofdeveloped flow in a converging-diverging pipe: the velocity distribution at the stenosis issmoother, the centerline velocity decreases, and the wall shear stress and pressure gradient increase in the entrance region. The length of entrance flow for the pipe is slighty lower than that for a straight one with constant cross section. The results are checked by thefinite difference method.
文摘A fully elliptic numerical study has been carried out to investigate the three-dimensional turbulent developing flow in a helical square duct with large curvature. A two-layer zonal model is proposed and used, in which the whole region is divided into a viscosity-affected near wall layer and a fully turbulent region. A DSM closure is applied in the former, and a one-equation model is solved in the latter. The results presented in this paper cover a Reynolds number range of (l- 10) x 104. The development of flow is found to be dominated by radial pressure gradient and Dean-type secondary motion. The distribution of Reynolds stresses in fully developed flow exhibit a complex pattern of turbulence anisotropy The development of peripherally averaged friction factor and the distribution of local friction factor in fully developed flow are given and discussed.
