Three-dimensional compressible flow simulationswere conducted to develop a Hyperloop pod. Thenovelty is the usage of Gamma transition model, in whichthe transition from laminar to turbulent flow can be predicted.First...Three-dimensional compressible flow simulationswere conducted to develop a Hyperloop pod. Thenovelty is the usage of Gamma transition model, in whichthe transition from laminar to turbulent flow can be predicted.First, a mesh dependency study was undertaken,showing second-order convergence with respect to themesh refinement. Second, an aerodynamic analysis for twodesigns, short and optimized, was conducted with thetraveling speed 125 m/s at the system pressure 0.15 bar.The concept of the short model was to delay the transitionto decrease the frictional drag;meanwhile that of theoptimized design was to minimize the pressure drag bydecreasing the frontal area and introduce the transitionmore toward the front of the pod. The computed resultsshow that the transition of the short model occurred moreon the rear side due to the pod shape, which resulted in 8%smaller frictional drag coefficient than that for the optimizedmodel. The pressure drag for the optimized designwas 24% smaller than that for the short design, half ofwhich is due to the decrease in the frontal area, and theother half is due to the smoothed rear-end shape. The totaldrag for the optimized model was 14% smaller than that forthe short model. Finally, the influence of the systempressure was investigated. As the system pressure and theReynolds number increase, the frictional drag coefficientincreases, and the transition point moves toward the front,which are the typical phenomena observed in the transitionregime.展开更多
Hyperloop has become one of the key reserve technologies for future high-speed rail transit.The gas in the tube is compressed and rubbed,leading to a strong aerodynamic heating effect.The research on the flow field ch...Hyperloop has become one of the key reserve technologies for future high-speed rail transit.The gas in the tube is compressed and rubbed,leading to a strong aerodynamic heating effect.The research on the flow field characteristics and aerodynamic heating effect of hyperloop is in its infancy,and that on the flow field structure is lacking.In this study,the nozzle theory was used to make a preliminary judgment on the choked flow phenomenon in the hyperloop.Based on the flow results obtained under different working conditions,the identification basis of the choked flow phenomenon in the hyperloop was obtained.Furthermore,the effect of the choked/unchoked flow on the flow structure,temperature,and pressure distribution of the annular space in the tube was analyzed.Based on traditional high-speed railway aerodynamics,according to relevant theories and calculation in aerospace field,and combined with the model test data,the reliability verification analysis on the characteristics of the flow field are carried out.The structure of the flow filed in the tube can be divided into choked and unchoked.The judgment is dependent on whether the throat reaches the speed of sound.Under the choked flow,a normal shock wave is formed in front of the tube train.The temperature rise of the local flow field exceeds 50 K;the temperature rise of the stagnation region exceeds 88 K,and the pressure is approximately 1.7 times that of the initial pressure in the tube.When the flow is unchoked,differences arise in the distribution of the flow field corresponding to different incoming Mach numbers.When the incoming flow is supersonic,the flow field maintains a supersonic speed,and a bow-shaped shock wave is formed at the front of the tube train.Owing to the shock wave or expansion wave,the local flow field exhibits significant fluctuations in temperature and pressure.Conversely,when the incoming flow is subsonic,the flow field in the tube maintains a subsonic speed,and no shock wave structure is observed.展开更多
基金The authors acknowledge all the members of the Swissloop Team for their great endeavor to compete in the Hyperloop pod Competition and to push the Hyperloop technology forward.The authors gratefully acknowledge Connova AG for their support in manufacturing of the pod.
文摘Three-dimensional compressible flow simulationswere conducted to develop a Hyperloop pod. Thenovelty is the usage of Gamma transition model, in whichthe transition from laminar to turbulent flow can be predicted.First, a mesh dependency study was undertaken,showing second-order convergence with respect to themesh refinement. Second, an aerodynamic analysis for twodesigns, short and optimized, was conducted with thetraveling speed 125 m/s at the system pressure 0.15 bar.The concept of the short model was to delay the transitionto decrease the frictional drag;meanwhile that of theoptimized design was to minimize the pressure drag bydecreasing the frontal area and introduce the transitionmore toward the front of the pod. The computed resultsshow that the transition of the short model occurred moreon the rear side due to the pod shape, which resulted in 8%smaller frictional drag coefficient than that for the optimizedmodel. The pressure drag for the optimized designwas 24% smaller than that for the short design, half ofwhich is due to the decrease in the frontal area, and theother half is due to the smoothed rear-end shape. The totaldrag for the optimized model was 14% smaller than that forthe short model. Finally, the influence of the systempressure was investigated. As the system pressure and theReynolds number increase, the frictional drag coefficientincreases, and the transition point moves toward the front,which are the typical phenomena observed in the transitionregime.
基金This work was supported by Hebei Province Natural Science Foundation(E2022105032)National Natural Science Foundation of China(51978575,52172359).
文摘Hyperloop has become one of the key reserve technologies for future high-speed rail transit.The gas in the tube is compressed and rubbed,leading to a strong aerodynamic heating effect.The research on the flow field characteristics and aerodynamic heating effect of hyperloop is in its infancy,and that on the flow field structure is lacking.In this study,the nozzle theory was used to make a preliminary judgment on the choked flow phenomenon in the hyperloop.Based on the flow results obtained under different working conditions,the identification basis of the choked flow phenomenon in the hyperloop was obtained.Furthermore,the effect of the choked/unchoked flow on the flow structure,temperature,and pressure distribution of the annular space in the tube was analyzed.Based on traditional high-speed railway aerodynamics,according to relevant theories and calculation in aerospace field,and combined with the model test data,the reliability verification analysis on the characteristics of the flow field are carried out.The structure of the flow filed in the tube can be divided into choked and unchoked.The judgment is dependent on whether the throat reaches the speed of sound.Under the choked flow,a normal shock wave is formed in front of the tube train.The temperature rise of the local flow field exceeds 50 K;the temperature rise of the stagnation region exceeds 88 K,and the pressure is approximately 1.7 times that of the initial pressure in the tube.When the flow is unchoked,differences arise in the distribution of the flow field corresponding to different incoming Mach numbers.When the incoming flow is supersonic,the flow field maintains a supersonic speed,and a bow-shaped shock wave is formed at the front of the tube train.Owing to the shock wave or expansion wave,the local flow field exhibits significant fluctuations in temperature and pressure.Conversely,when the incoming flow is subsonic,the flow field in the tube maintains a subsonic speed,and no shock wave structure is observed.
