Based on the mechanical system of free-end fibers and the analysis of pulling free-end fibers out of the spun yarn during spinning,a low-fiber hollow spindle is designed and the air distribution of fluent field is sim...Based on the mechanical system of free-end fibers and the analysis of pulling free-end fibers out of the spun yarn during spinning,a low-fiber hollow spindle is designed and the air distribution of fluent field is simulated numerically. The negative pressure effect is much bigger at the top of low-fiber hollow spindle than that in Murata No.861,which is more conducive for single fiber to get into the channel of hollow spindle. The tangential velocity in 0-3 mm at the top of hollow spindle increases and the fluctuation of radial velocity is much stronger,which enhance the wrapping effect. In the addition,the distribution of axial velocity remains the same.展开更多
The interaction between a shock wave and a boundary layer on a suction side of gas turbine profile,namely Transition Location Effect on Shock Wave Boundary Layer Interaction,was one of main objectives of TFAST project...The interaction between a shock wave and a boundary layer on a suction side of gas turbine profile,namely Transition Location Effect on Shock Wave Boundary Layer Interaction,was one of main objectives of TFAST project.A generic test section in a transonic wind tunnel was designed to carry out such investigations.The design criteria were to reproduce flow conditions on the profile in wind tunnel as the one existing on the suction side of the turbine guide vane.In this paper,the effect of film cooling and jet vortex generators on the shock wave boundary layer interaction and shock induced separation is presented.Numerical results for Explicit Algebraic Reynolds Stress Model with transition modeling are compared with experimental data.展开更多
To develop vortex generator jet （VGJ） method for flow control, the turbulence flow in a 14° conical diffuser with and without vortex generator jets are simulated by solving Navier-Stokes equations with k-ε tur...To develop vortex generator jet （VGJ） method for flow control, the turbulence flow in a 14° conical diffuser with and without vortex generator jets are simulated by solving Navier-Stokes equations with k-ε turbulence model. The diffuser performance, based on different velocity ratio （ratio of the jet speed to the mainstream velocity）, is investigated and compared with the experimental study. On the basis of the flow characteristics using computation fluid dynamics （CFD） method observed in the conical diffuser and the downstream development of the longitudinal vortices, attempt is made to correlate the pressure recovery coefficient with the behavior of vortices produced by vortex generator jets.展开更多
Direct numerical simulation of a jet issuing from a nozzle having a rectangular cross-section is conducted. The vortex in cell (VIC) method, of which computational accuracy was heightened by the authors in a prior stu...Direct numerical simulation of a jet issuing from a nozzle having a rectangular cross-section is conducted. The vortex in cell (VIC) method, of which computational accuracy was heightened by the authors in a prior study, is used for the DNS. The aspect ratio of the nozzle cross-section is 15, and the Reynolds number based on the shorter side length of the nozzle exit is 6700. The turbulence statics, such as the mean velocity and the turbulence intensity, are favorably compared with the experimentally measured results. The behavior of the large-scale eddies as well as the development of the turbulent flow is also confirmed to agree with the measurement. These indicate that the authors’ VIC method is successfully employed for the DNS of rectangular jet.展开更多
The effects of the vortex generator jet(VGJ)attached at the endwall on the corner separation/stall control are investigated by numerical simulation in a high-turning linear compressor cascade. The results show that th...The effects of the vortex generator jet(VGJ)attached at the endwall on the corner separation/stall control are investigated by numerical simulation in a high-turning linear compressor cascade. The results show that the corner separation could be reduced significantly, which results in a wider operation range as well as a more uniform exit flow angle and total pressure profile. At the near-stall operation point, the maximum relative reduction of the total pressure loss is up to 32.5%,, whereas the jet mass ratio is less than 0.4%,. Based on the analysis of the detailed flow structure, three principal effects of the VGJ on the endwall cross flow and corner separation are identified. One is to increase the tangential velocity component opposite to cross flow, thus inhibiting the endwall secondary flow near the jet exit. The second is to suppress the pitchwise extension of the passage vortex as an air fence. The third is to sweep the low energy fluids towards the mainstream on the up-washed side and to transport the mainstream fluids to the endwall to reenergize the boundary layer on the down-washed side.展开更多
Contrary to natural cavitation,ventilated cavitation is controllable and is not harmful.It is particularly used to reduce the drag of the hydraulic vehicles.The ventilated cavitation is characterized by various gas re...Contrary to natural cavitation,ventilated cavitation is controllable and is not harmful.It is particularly used to reduce the drag of the hydraulic vehicles.The ventilated cavitation is characterized by various gas regimes.The mechanisms of ventilated cavitation are investigated in the present work with CFD based on a 2D solver.The attention is especially focused on the transition between the reentrant jet and twin vortex regimes.The results confirmthat the product of ventilated cavitation number and Froude number is lower than 1(σcFr<1)in the twin vortex regime,while it is higher than 1(σcFr>1)in the reentrant jet regime,as reported in the literature.Further analysis shows that ventilated cavitation is significantly influenced by the natural cavitation number.展开更多
基金Program for Changjiang Scholars and Innovative Research Team in University,China(No.IRT1220)Shanghai Natural Science Foundation,China(No.13ZR1400900)Keygrant Project of Chinese Ministry of Education(No.113027A)
文摘Based on the mechanical system of free-end fibers and the analysis of pulling free-end fibers out of the spun yarn during spinning,a low-fiber hollow spindle is designed and the air distribution of fluent field is simulated numerically. The negative pressure effect is much bigger at the top of low-fiber hollow spindle than that in Murata No.861,which is more conducive for single fiber to get into the channel of hollow spindle. The tangential velocity in 0-3 mm at the top of hollow spindle increases and the fluctuation of radial velocity is much stronger,which enhance the wrapping effect. In the addition,the distribution of axial velocity remains the same.
基金supported by the 7 EU framework project and was carried out within the research project with the acronym TFAST(Transition Location Effect on Shock Wave Boundary Layer Interaction)supported by CI TASKPL-Grid Infrastructure。
文摘The interaction between a shock wave and a boundary layer on a suction side of gas turbine profile,namely Transition Location Effect on Shock Wave Boundary Layer Interaction,was one of main objectives of TFAST project.A generic test section in a transonic wind tunnel was designed to carry out such investigations.The design criteria were to reproduce flow conditions on the profile in wind tunnel as the one existing on the suction side of the turbine guide vane.In this paper,the effect of film cooling and jet vortex generators on the shock wave boundary layer interaction and shock induced separation is presented.Numerical results for Explicit Algebraic Reynolds Stress Model with transition modeling are compared with experimental data.
基金This project is supported by Scientific Research Foundation of Ministry of Education of China for Returnee.
文摘To develop vortex generator jet （VGJ） method for flow control, the turbulence flow in a 14° conical diffuser with and without vortex generator jets are simulated by solving Navier-Stokes equations with k-ε turbulence model. The diffuser performance, based on different velocity ratio （ratio of the jet speed to the mainstream velocity）, is investigated and compared with the experimental study. On the basis of the flow characteristics using computation fluid dynamics （CFD） method observed in the conical diffuser and the downstream development of the longitudinal vortices, attempt is made to correlate the pressure recovery coefficient with the behavior of vortices produced by vortex generator jets.
文摘Direct numerical simulation of a jet issuing from a nozzle having a rectangular cross-section is conducted. The vortex in cell (VIC) method, of which computational accuracy was heightened by the authors in a prior study, is used for the DNS. The aspect ratio of the nozzle cross-section is 15, and the Reynolds number based on the shorter side length of the nozzle exit is 6700. The turbulence statics, such as the mean velocity and the turbulence intensity, are favorably compared with the experimentally measured results. The behavior of the large-scale eddies as well as the development of the turbulent flow is also confirmed to agree with the measurement. These indicate that the authors’ VIC method is successfully employed for the DNS of rectangular jet.
基金Supported by the National Natural Science Foundation of China(No.51306042)
文摘The effects of the vortex generator jet(VGJ)attached at the endwall on the corner separation/stall control are investigated by numerical simulation in a high-turning linear compressor cascade. The results show that the corner separation could be reduced significantly, which results in a wider operation range as well as a more uniform exit flow angle and total pressure profile. At the near-stall operation point, the maximum relative reduction of the total pressure loss is up to 32.5%,, whereas the jet mass ratio is less than 0.4%,. Based on the analysis of the detailed flow structure, three principal effects of the VGJ on the endwall cross flow and corner separation are identified. One is to increase the tangential velocity component opposite to cross flow, thus inhibiting the endwall secondary flow near the jet exit. The second is to suppress the pitchwise extension of the passage vortex as an air fence. The third is to sweep the low energy fluids towards the mainstream on the up-washed side and to transport the mainstream fluids to the endwall to reenergize the boundary layer on the down-washed side.
基金performed in the scope of project ANR-12-ASTR-0017-03 "BF-DRAINH" in collaboration with the IRENav Laboratory (French Naval Academy,Brest,France) and the IMFT laboratory (Toulouse,France)
文摘Contrary to natural cavitation,ventilated cavitation is controllable and is not harmful.It is particularly used to reduce the drag of the hydraulic vehicles.The ventilated cavitation is characterized by various gas regimes.The mechanisms of ventilated cavitation are investigated in the present work with CFD based on a 2D solver.The attention is especially focused on the transition between the reentrant jet and twin vortex regimes.The results confirmthat the product of ventilated cavitation number and Froude number is lower than 1(σcFr<1)in the twin vortex regime,while it is higher than 1(σcFr>1)in the reentrant jet regime,as reported in the literature.Further analysis shows that ventilated cavitation is significantly influenced by the natural cavitation number.
