Vorticity is locally generated on a boundary at a rate measured by the boundary vorticity flux(BVF),which can be further decomposed into the sum of the orbital rotation and the generalized spin(specifically,the sum of...Vorticity is locally generated on a boundary at a rate measured by the boundary vorticity flux(BVF),which can be further decomposed into the sum of the orbital rotation and the generalized spin(specifically,the sum of shear and streaming vorticity)under the field description.For an incompressible viscous flow interacting with a stationary wall,the full expressions of the boundary fluxes of the orbital rotation and the spin are derived,for the first time,to elucidate their boundary creation mechanisms.Then,these new findings are successfully extended to the study of the boundary enstrophy dynamics,as well as the Lyman vorticity dynamics as an alternative interpretation to the boundary vorticity dynamics.Interestingly,it is found that the boundary coupling of the longitudinal and transverse processes is only embodied in the boundary spin flux,which is definitely not responsible for the generation of the boundary orbital-rotation flux.In addition,the boundary fluxes of enstrophy are directly associated with the boundary source of the second principal invariant of the velocity gradient tensor(VGT)and the two quadratic forms representing the spin-geometry interaction.The present exposition provides a new perspective and an additional dimension for understanding the vorticity dynamics on boundaries,which could be valuable in clarifying the formation mechanisms of near-wall coherent structures and flow noise at the fundamental level.展开更多
This paper presents two optimized rotors. The first rotor is as part of a 3-blade row optimization (IGV-rotor-stator) of a high-pressure compressor. It is based on modifying blade angles and advanced control of curvat...This paper presents two optimized rotors. The first rotor is as part of a 3-blade row optimization (IGV-rotor-stator) of a high-pressure compressor. It is based on modifying blade angles and advanced control of curvature of the airfoil camber line. The effects of these advanced blade techniques on the performance of the transonic 1.5-stage compressor were calculated using a 3D Navier-Stokes solver combined with a vortex/vorticity dynamics diagnosis method. The first optimized rotor produces a 3-blade row efficiency improvement over the baseline of 1.45% while also improving stall margin. The throttling range of the compressor is expanded largely because the shock in the rotor tip area is further downstream than that in the baseline case at the operating point. Additionally, optimizing the 3-blade row block while only adjusting the rotor geometry ensures good matching of flow angles allowing the compressor to have more range. The flow diagnostics of the rotor blade based on vortex/vorticity dynamics indicate that the boundary-layer separation behind the shock is verified by on-wall signatures of vorticity and skin-friction vector lines. In addition, azimuthal vorticity and boundary vorticity flux (BVF) are shown to be two vital flow parameters of compressor aerodynamic performance that directly relate to the improved performance of the optimized transonic compressor blade. A second rotor-only optimization is also presented for a 2.9 pressure ratio transonic fan. The objective function is the axial moment based on the BVF. An 88.5% efficiency rotor is produced.展开更多
Introduction Mechanotransduction has demonstrated potentials for tissue adaptation in vivo and in vitro. It is well documented that ultrasound,as a mechanical signal,can produce a wide variety of biological effects in...Introduction Mechanotransduction has demonstrated potentials for tissue adaptation in vivo and in vitro. It is well documented that ultrasound,as a mechanical signal,can produce a wide variety of biological effects in vitro and in vivo [1]. As an example,展开更多
基金Project supported by the National Natural Science Foundation of China(No.12402262)。
文摘Vorticity is locally generated on a boundary at a rate measured by the boundary vorticity flux(BVF),which can be further decomposed into the sum of the orbital rotation and the generalized spin(specifically,the sum of shear and streaming vorticity)under the field description.For an incompressible viscous flow interacting with a stationary wall,the full expressions of the boundary fluxes of the orbital rotation and the spin are derived,for the first time,to elucidate their boundary creation mechanisms.Then,these new findings are successfully extended to the study of the boundary enstrophy dynamics,as well as the Lyman vorticity dynamics as an alternative interpretation to the boundary vorticity dynamics.Interestingly,it is found that the boundary coupling of the longitudinal and transverse processes is only embodied in the boundary spin flux,which is definitely not responsible for the generation of the boundary orbital-rotation flux.In addition,the boundary fluxes of enstrophy are directly associated with the boundary source of the second principal invariant of the velocity gradient tensor(VGT)and the two quadratic forms representing the spin-geometry interaction.The present exposition provides a new perspective and an additional dimension for understanding the vorticity dynamics on boundaries,which could be valuable in clarifying the formation mechanisms of near-wall coherent structures and flow noise at the fundamental level.
文摘This paper presents two optimized rotors. The first rotor is as part of a 3-blade row optimization (IGV-rotor-stator) of a high-pressure compressor. It is based on modifying blade angles and advanced control of curvature of the airfoil camber line. The effects of these advanced blade techniques on the performance of the transonic 1.5-stage compressor were calculated using a 3D Navier-Stokes solver combined with a vortex/vorticity dynamics diagnosis method. The first optimized rotor produces a 3-blade row efficiency improvement over the baseline of 1.45% while also improving stall margin. The throttling range of the compressor is expanded largely because the shock in the rotor tip area is further downstream than that in the baseline case at the operating point. Additionally, optimizing the 3-blade row block while only adjusting the rotor geometry ensures good matching of flow angles allowing the compressor to have more range. The flow diagnostics of the rotor blade based on vortex/vorticity dynamics indicate that the boundary-layer separation behind the shock is verified by on-wall signatures of vorticity and skin-friction vector lines. In addition, azimuthal vorticity and boundary vorticity flux (BVF) are shown to be two vital flow parameters of compressor aerodynamic performance that directly relate to the improved performance of the optimized transonic compressor blade. A second rotor-only optimization is also presented for a 2.9 pressure ratio transonic fan. The objective function is the axial moment based on the BVF. An 88.5% efficiency rotor is produced.
基金supported by the NIH (R01 AR52379 & R01 AR49286),U S Army Medical Research and NSBRI
文摘Introduction Mechanotransduction has demonstrated potentials for tissue adaptation in vivo and in vitro. It is well documented that ultrasound,as a mechanical signal,can produce a wide variety of biological effects in vitro and in vivo [1]. As an example,
