The commercial finite code ANSYS was employed for the simulation of the electromagnetic tube bulging process. The finite element model and boundary conditions were thoroughly discussed. ANSYS/EMAG was used to model th...The commercial finite code ANSYS was employed for the simulation of the electromagnetic tube bulging process. The finite element model and boundary conditions were thoroughly discussed. ANSYS/EMAG was used to model the time varying electromagnetic field in order to obtain the radial and axial magnetic pressure acting on the tube. The magnetic pressure was then used as boundary conditions to model the high velocity deformation of various length tube with ANSYS/LSDYNA. The time space distribution of magnetic pressure on various length tubes was presented. Effect of tube size on the distribution of radial magnetic pressure and axial magnetic pressure and high velocity deformation were discussed. According to the radial magnetic pressure ratio of tube end to tube center and corresponding dimensionless length ratio of tube to coil, the free electromagnetic tube bulging was studied in classification. The calculated results show good agreements with practice.展开更多
Correlations for the extension of a water vapor jet injected in a liquid pool were historically proposed considering the mass flux (kg/m2/s) as a constant. The results were satisfactory, however adjusting the values b...Correlations for the extension of a water vapor jet injected in a liquid pool were historically proposed considering the mass flux (kg/m2/s) as a constant. The results were satisfactory, however adjusting the values by linear regression. Although, it presents the following drawbacks: 1) the formulation is only valid for the specific range of data for what it was created;2) it does not allow the analytical evaluation of the heat transfer coefficient from the extension equation. This paper proposes a new formulation for the calculation of the mass flux, in such a way to remove both of these drawbacks.展开更多
For Unmanned Aerial Vehicles(UAVs)with limited electrical power to achieve effectively anti-/de-icing at the leading edge of the wing,a strategy of ice shape modulation was proposed.Isolated simulated ice shape pieces...For Unmanned Aerial Vehicles(UAVs)with limited electrical power to achieve effectively anti-/de-icing at the leading edge of the wing,a strategy of ice shape modulation was proposed.Isolated simulated ice shape pieces printed by 3D printing technology are mounted on a NACA0012 finite wing model,and its lift/drag coefficients and suction-side velocity fields are measured by the six-component force balance and the Particle Imaging Velocimetry(PIV),respectively.The ratio of the spanwise length of a single ice shape piece to chord length and the spanwise length of the non-icing area between the two adjacent single ice shape pieces are defined as dimensionless ice shape length(w/c)and dimensionless modulation ratio(w/λ),respectively.The results indicate that for a fixed w/λ,the wing lift coefficient first increases and then drops with increasing w/c,and a peak value exists when w/c is between 0.1 and 0.2.The lower the w/λis,the higher the wing lift coefficient will be.The periodical variation of the flow separation area along the spanwise direction is attributed on the one hand to the acceleration effect of the flow field in the non-icing area which reduces the separation area,and on the other hand to the cross-flow caused by the streamwise vortices from the non-icing area to the icing area which promotes the mixing of the flow field(similar to vortex generators).The obtained modulation law is verified through flight tests and provides guidance for the use of ice shape modulation scheme for UAVs that cannot be completely anti-/deicing under severe weather conditions.展开更多
The objective of this study is to investigate critical velocity and smoke maximum temperature beneath the ceiling in the connected area of branch tunnel with varying fire locations.The fire sources were located in the...The objective of this study is to investigate critical velocity and smoke maximum temperature beneath the ceiling in the connected area of branch tunnel with varying fire locations.The fire sources were located in the divergent connected area of the branch tunnel,to imitate traffic accidents near the branch point.A 1/20 scale model branch tunnel was built including main line before branch,main line after branch,and ramp.Experimental tests and numerical simulations were performed to explore smoke movement characteristics with longitudinal ventilation.The results showed that the enlarged cross-sectional area in branch tunnel caused the shortening of the back-layering length,and a modified model of back-layering length was proposed.The higher tunnel height in this work affected the critical condition of large fire;it caused a larger transition point of dimensionless critical velocity.A revised model was proposed for the maximum temperature rise of tunnel fires in the connected area of branch tunnel.The critical velocity kept unchanged when the branch angle increased from 0°to 20°because there is little change in the longitudinal smoke temperature.As the local tunnel width of fire source was increased,the required critical velocity was increased while the local effective velocity kept nearly the same.展开更多
文摘The commercial finite code ANSYS was employed for the simulation of the electromagnetic tube bulging process. The finite element model and boundary conditions were thoroughly discussed. ANSYS/EMAG was used to model the time varying electromagnetic field in order to obtain the radial and axial magnetic pressure acting on the tube. The magnetic pressure was then used as boundary conditions to model the high velocity deformation of various length tube with ANSYS/LSDYNA. The time space distribution of magnetic pressure on various length tubes was presented. Effect of tube size on the distribution of radial magnetic pressure and axial magnetic pressure and high velocity deformation were discussed. According to the radial magnetic pressure ratio of tube end to tube center and corresponding dimensionless length ratio of tube to coil, the free electromagnetic tube bulging was studied in classification. The calculated results show good agreements with practice.
文摘Correlations for the extension of a water vapor jet injected in a liquid pool were historically proposed considering the mass flux (kg/m2/s) as a constant. The results were satisfactory, however adjusting the values by linear regression. Although, it presents the following drawbacks: 1) the formulation is only valid for the specific range of data for what it was created;2) it does not allow the analytical evaluation of the heat transfer coefficient from the extension equation. This paper proposes a new formulation for the calculation of the mass flux, in such a way to remove both of these drawbacks.
基金supported by the National Natural Science Foundation of China(No.12002384)the National Key Laboratory Foundation of China(No.614220210200112)。
文摘For Unmanned Aerial Vehicles(UAVs)with limited electrical power to achieve effectively anti-/de-icing at the leading edge of the wing,a strategy of ice shape modulation was proposed.Isolated simulated ice shape pieces printed by 3D printing technology are mounted on a NACA0012 finite wing model,and its lift/drag coefficients and suction-side velocity fields are measured by the six-component force balance and the Particle Imaging Velocimetry(PIV),respectively.The ratio of the spanwise length of a single ice shape piece to chord length and the spanwise length of the non-icing area between the two adjacent single ice shape pieces are defined as dimensionless ice shape length(w/c)and dimensionless modulation ratio(w/λ),respectively.The results indicate that for a fixed w/λ,the wing lift coefficient first increases and then drops with increasing w/c,and a peak value exists when w/c is between 0.1 and 0.2.The lower the w/λis,the higher the wing lift coefficient will be.The periodical variation of the flow separation area along the spanwise direction is attributed on the one hand to the acceleration effect of the flow field in the non-icing area which reduces the separation area,and on the other hand to the cross-flow caused by the streamwise vortices from the non-icing area to the icing area which promotes the mixing of the flow field(similar to vortex generators).The obtained modulation law is verified through flight tests and provides guidance for the use of ice shape modulation scheme for UAVs that cannot be completely anti-/deicing under severe weather conditions.
基金This research was supported by the National Nature Science Foundation of China(No.52076066)Key Research and Development Project of Zhejiang Province(No.2018C03029)+1 种基金Zhejiang Provincial Natural Science Foundation of China(No.LQ19E040005)Fellowship of China Postdoctoral Science Foundation(No.2021M693042).
文摘The objective of this study is to investigate critical velocity and smoke maximum temperature beneath the ceiling in the connected area of branch tunnel with varying fire locations.The fire sources were located in the divergent connected area of the branch tunnel,to imitate traffic accidents near the branch point.A 1/20 scale model branch tunnel was built including main line before branch,main line after branch,and ramp.Experimental tests and numerical simulations were performed to explore smoke movement characteristics with longitudinal ventilation.The results showed that the enlarged cross-sectional area in branch tunnel caused the shortening of the back-layering length,and a modified model of back-layering length was proposed.The higher tunnel height in this work affected the critical condition of large fire;it caused a larger transition point of dimensionless critical velocity.A revised model was proposed for the maximum temperature rise of tunnel fires in the connected area of branch tunnel.The critical velocity kept unchanged when the branch angle increased from 0°to 20°because there is little change in the longitudinal smoke temperature.As the local tunnel width of fire source was increased,the required critical velocity was increased while the local effective velocity kept nearly the same.
