Mixing, achieved mostly by mechanically stirring, is one of the most important unit operation processes in chemical and related industries. The problem of design and scale-up of stirred tanks has been tackled mainly b...Mixing, achieved mostly by mechanically stirring, is one of the most important unit operation processes in chemical and related industries. The problem of design and scale-up of stirred tanks has been tackled mainly by means of semi-empirical methods.Measurement and numerical simulation of viscous fluid in a stirred tank is still unsufficient and further development is needed.In this paper, computational fluid dynamics (CFD) simulation and digital particle image velocimetry (DPIV) measurement have been carried out to study the flow field of viscous fluid in a stirred tank agitated by a four-blade Ruston turbine.The working medium is a mixture of water and glycerine with various concentrations.The results show the mean velocity, turbulent energy, vorticity and circle flux of the fluids as well as the change of flow patterns with the fluid viscosity.CFD code of CFX with sliding grids was used to simulate the flow field.The k-ε model and laminar model was selected as the models of simulation.The CFD simulations were compared with the experimental DPIV data.The result shows that the CFD simulations can reflect the flow of the viscous fluid in a stirred tank.展开更多
Digital particle imaging velocimetry (DPIV) was used to me as ure the transient and time-averaged flow field in the mixing region and the wak e of a square jet into crossflow at jet-to-crossflow velocity ratio (VR) o ...Digital particle imaging velocimetry (DPIV) was used to me as ure the transient and time-averaged flow field in the mixing region and the wak e of a square jet into crossflow at jet-to-crossflow velocity ratio (VR) o f 0.5 and 2. The phenomenon of vortex instantaneously shedding from the jet ho le was investigated, and the flow turbulence intensity was estimated. The compl ex vortical structures encountered at VR of 2 were analyzed. Compulsively o ppressed by the main flow, the jet attached to the wall at VR of 0.5, and l ifted off the wall to develope into the main flow at VR of 2. The twisted v ortices in the leeward of jet contributed to the transportation of the crossflow boundary-layer fluid into the near wake, causing intensive turbulence. Strong vortices formed near the jet hole soon broke down and dissipated, yet the weak counter-vortex pair still held in the far wake.展开更多
基金国家自然科学基金项目 (No 2 983 613 0 )清华大学基础研究基金项目 (No JZ2 0 0 0 0 0 8)~~
文摘Mixing, achieved mostly by mechanically stirring, is one of the most important unit operation processes in chemical and related industries. The problem of design and scale-up of stirred tanks has been tackled mainly by means of semi-empirical methods.Measurement and numerical simulation of viscous fluid in a stirred tank is still unsufficient and further development is needed.In this paper, computational fluid dynamics (CFD) simulation and digital particle image velocimetry (DPIV) measurement have been carried out to study the flow field of viscous fluid in a stirred tank agitated by a four-blade Ruston turbine.The working medium is a mixture of water and glycerine with various concentrations.The results show the mean velocity, turbulent energy, vorticity and circle flux of the fluids as well as the change of flow patterns with the fluid viscosity.CFD code of CFX with sliding grids was used to simulate the flow field.The k-ε model and laminar model was selected as the models of simulation.The CFD simulations were compared with the experimental DPIV data.The result shows that the CFD simulations can reflect the flow of the viscous fluid in a stirred tank.
文摘Digital particle imaging velocimetry (DPIV) was used to me as ure the transient and time-averaged flow field in the mixing region and the wak e of a square jet into crossflow at jet-to-crossflow velocity ratio (VR) o f 0.5 and 2. The phenomenon of vortex instantaneously shedding from the jet ho le was investigated, and the flow turbulence intensity was estimated. The compl ex vortical structures encountered at VR of 2 were analyzed. Compulsively o ppressed by the main flow, the jet attached to the wall at VR of 0.5, and l ifted off the wall to develope into the main flow at VR of 2. The twisted v ortices in the leeward of jet contributed to the transportation of the crossflow boundary-layer fluid into the near wake, causing intensive turbulence. Strong vortices formed near the jet hole soon broke down and dissipated, yet the weak counter-vortex pair still held in the far wake.
