Inspired by shark’s skin in nature,a non-smooth surface could be an ideal model for changing the flow characteristics of fluids on the object surface.To analyze the effect of a non-smooth surface with concaves on the...Inspired by shark’s skin in nature,a non-smooth surface could be an ideal model for changing the flow characteristics of fluids on the object surface.To analyze the effect of a non-smooth surface with concaves on the maglev train aerodynamic performances and to investigate how the concave size affects the aerodynamic forces and flow structure of a maglev train,four 1/10th scaled maglev train models are simulated using an Improved Delayed Detached Eddy Simulation(IDDES)method.The numerical strategy used in this study is verified by comparison with the wind tunnel test results,and the comparison shows that the difference was in a reasonable range.The results demonstrate that the concaves could effectively reduce the tail car pressure drag,thus reducing the total drag,and that the smaller the concave size was,the better the drag reduction effect would be.The change in the lift with the concave size was more significant than that of the drag,and the tail car lift of R1(0.0012H),R2(0.0024H),and R3(0.0036H)train models was 30.1%,43.0%,and 44.5%less than that of the prototype,respectively.In addition,different flow topologies of the wake are analyzed.The width and height of the vortex core of the counter-rotating vortices tended to decrease with the concave size.Thus,from the point of view of ensuring the operating safety of a maglev train,a non-smooth surface with small-size concaves is recommended.展开更多
Transient numerical simulations were carried out by placing dimples at the top,sides and bottoms of the tail car streamline area of a high-speed maglev train.The results of an improved delayed detached eddy simulation...Transient numerical simulations were carried out by placing dimples at the top,sides and bottoms of the tail car streamline area of a high-speed maglev train.The results of an improved delayed detached eddy simulation turbulence model using three-dimensional compressible Navier-Stokes and shear-stress transport K-Omega double equations were compared to the results of a wind tunnel test to verify the numerical simulation accuracy,within 5%of the ground truth,which is an acceptable precision range.The results show that dimples arranged on the streamline area atop the train tail car affected the locations at which the airflow at the top and bottom of the train met and weakened the strength of the wake.The aerodynamic drag and lift coefficient decreased by 3.40%and 4.27%,respectively.When the dimples were arranged on the streamline area at the sides or bottoms of the train tail car,they had little effect on the top of the tail car,so they did not destroy the balance of the airflow at the top and bottom.They also had little influence on the development of wake topology.Therefore,the aerodynamic drag and lift of the train changed little.展开更多
基金This work was supported by the National Numerical Wind Tunnel Project(Grant No.NNW2018-ZT1A02).
文摘Inspired by shark’s skin in nature,a non-smooth surface could be an ideal model for changing the flow characteristics of fluids on the object surface.To analyze the effect of a non-smooth surface with concaves on the maglev train aerodynamic performances and to investigate how the concave size affects the aerodynamic forces and flow structure of a maglev train,four 1/10th scaled maglev train models are simulated using an Improved Delayed Detached Eddy Simulation(IDDES)method.The numerical strategy used in this study is verified by comparison with the wind tunnel test results,and the comparison shows that the difference was in a reasonable range.The results demonstrate that the concaves could effectively reduce the tail car pressure drag,thus reducing the total drag,and that the smaller the concave size was,the better the drag reduction effect would be.The change in the lift with the concave size was more significant than that of the drag,and the tail car lift of R1(0.0012H),R2(0.0024H),and R3(0.0036H)train models was 30.1%,43.0%,and 44.5%less than that of the prototype,respectively.In addition,different flow topologies of the wake are analyzed.The width and height of the vortex core of the counter-rotating vortices tended to decrease with the concave size.Thus,from the point of view of ensuring the operating safety of a maglev train,a non-smooth surface with small-size concaves is recommended.
基金supported by the National NumericalWind Tun-nel Project(Grant No.2018-ZT1A02)the Fundamental Research Funds for the Central Universities of Central South University(Grant No.2021zzts0682)the Fundamental Research Funds for the Central Universities of Central South University(Grant No.2019zzts266).
文摘Transient numerical simulations were carried out by placing dimples at the top,sides and bottoms of the tail car streamline area of a high-speed maglev train.The results of an improved delayed detached eddy simulation turbulence model using three-dimensional compressible Navier-Stokes and shear-stress transport K-Omega double equations were compared to the results of a wind tunnel test to verify the numerical simulation accuracy,within 5%of the ground truth,which is an acceptable precision range.The results show that dimples arranged on the streamline area atop the train tail car affected the locations at which the airflow at the top and bottom of the train met and weakened the strength of the wake.The aerodynamic drag and lift coefficient decreased by 3.40%and 4.27%,respectively.When the dimples were arranged on the streamline area at the sides or bottoms of the train tail car,they had little effect on the top of the tail car,so they did not destroy the balance of the airflow at the top and bottom.They also had little influence on the development of wake topology.Therefore,the aerodynamic drag and lift of the train changed little.
