Wind loads on a moving vehicle–bridge deck system by wind-tunnel model test

Yongle Li,Peng Hu,You-Lin Xu,Mingjin Zhang,Haili Liao 한국풍공학회 2014 Wind and Structures, An International Journal (WAS Vol.19 No.2

Wind-vehicle-bridge (WVB) interaction can be regarded as a coupled vibration system. Aerodynamic forces and moment on vehicles and bridge decks play an important role in the vibration analysis of the coupled WVB system. High-speed vehicle motion has certain effects on the aerodynamic characteristics of a vehicle-bridge system under crosswinds, but it is not taken into account in most previous studies. In this study, a new testing system with a moving vehicle model was developed to directly measure the aerodynamic forces and moment on the vehicle and bridge deck when the vehicle model moved on the bridge deck under crosswinds in a large wind tunnel. The testing system, with a total length of 18.0 m, consisted of three main parts: vehicle-bridge model system, motion system and signal measuring system. The wind speed, vehicle speed, test objects and relative position of the vehicle to the bridge deck could be easily altered for different test cases. The aerodynamic forces and moment on the moving vehicle and bridge deck were measured utilizing the new testing system. The effects of the vehicle speed, wind yaw angle, rail track position and vehicle type on the aerodynamic characteristics of the vehicle and bridge deck were investigated. In addition, a data processing method was proposed according to the characteristics of the dynamic testing signals to determine the variations of aerodynamic forces and moment on the moving vehicle and bridge deck. Three-car and single-car models were employed as the moving rail vehicle model and road vehicle model, respectively. The results indicate that the drag and lift coefficients of the vehicle tend to increase with the increase of the vehicle speed and the decrease of the resultant wind yaw angle and that the vehicle speed has more significant effect on the aerodynamic coefficients of the single-car model than on those of the three-car model. This study also reveals that the aerodynamic coefficients of the vehicle and bridge deck are strongly influenced by the rail track positions, while the aerodynamic coefficients of the bridge deck are insensitive to the vehicle speed or resultant wind yaw angle.

Numerical simulation of the neutral equilibrium atmospheric boundary layer using the SST k-ω turbulence model

Hu, Peng,Li, Yongle,Cai, C.S.,Liao, Haili,Xu, G.J. Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.17 No.1

Modeling an equilibrium atmospheric boundary layer (ABL) in an empty computational domain has routinely been performed with the k-${\varepsilon}$ turbulence model. However, the research objects of structural wind engineering are bluff bodies, and the SST k-${\omega}$ turbulence model is more widely used in the numerical simulation of flow around bluff bodies than the k-${\varepsilon}$ turbulence model. Therefore, to simulate an equilibrium ABL based on the SST k-${\omega}$ turbulence model, the inlet profiles of the mean wind speed U, turbulence kinetic energy k, and specific dissipation rate ${\omega}$ are proposed, and the source terms for the U, k and ${\omega}$ are derived by satisfying their corresponding transport equations. Based on the proposed inlet profiles, numerical comparative studies with and without considering the source terms are carried out in an empty computational domain, and an actual numerical simulation with a trapezoidal hill is further conducted. It shows that when the source terms are considered, the profiles of U, k and ${\omega}$ are all maintained well along the empty computational domain and the accuracy of the actual numerical simulation is greatly improved. The present study could provide a new methodology for modeling the equilibrium ABL problem and for further CFD simulations with practical value.

The appropriate shape of the boundary transition section for a mountain-gorge terrain model in a wind tunnel test

Hu, Peng,Li, Yongle,Huang, Guoqing,Kang, Rui,Liao, Haili Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.1

Characterization of wind flows over a complex terrain, especially mountain-gorge terrain (referred to as the very complex terrain with rolling mountains and deep narrow gorges), is an important issue for design and operation of long-span bridges constructed in this area. In both wind tunnel testing and numerical simulation, a transition section is often used to connect the wind tunnel floor or computational domain bottom and the boundary top of the terrain model in order to generate a smooth flow transition over the edge of the terrain model. Although the transition section plays an important role in simulation of wind field over complex terrain, an appropriate shape needs investigation. In this study, two principles for selecting an appropriate shape of boundary transition section were proposed, and a theoretical curve serving for the mountain-gorge terrain model was derived based on potential flow theory around a circular cylinder. Then a two-dimensional (2-D) simulation was used to compare the flow transition performance between the proposed curved transition section and the traditional ramp transition section in a wind tunnel. Furthermore, the wind velocity field induced by the curved transition section with an equivalent slope of $30^{\circ}$ was investigated in detail, and a parameter called the 'velocity stability factor' was defined; an analytical model for predicting the velocity stability factor was also proposed. The results show that the proposed curved transition section has a better flow transition performance compared with the traditional ramp transition section. The proposed analytical model can also adequately predict the velocity stability factor of the wind field.

The appropriate shape of the boundary transition section for a mountain-gorge terrain model in a wind tunnel test

Peng Hu,Yongle Li,Rui Kang,Haili Liao 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.1

Characterization of wind flows over a complex terrain, especially mountain-gorge terrain (referred to as the very complex terrain with rolling mountains and deep narrow gorges), is an important issue for design and operation of long-span bridges constructed in this area. In both wind tunnel testing and numerical simulation, a transition section is often used to connect the wind tunnel floor or computational domain bottom and the boundary top of the terrain model in order to generate a smooth flow transition over the edge of the terrain model. Although the transition section plays an important role in simulation of wind field over complex terrain, an appropriate shape needs investigation. In this study, two principles for selecting an appropriate shape of boundary transition section were proposed, and a theoretical curve serving for the mountain-gorge terrain model was derived based on potential flow theory around a circular cylinder. Then a two-dimensional (2-D) simulation was used to compare the flow transition performance between the proposed curved transition section and the traditional ramp transition section in a wind tunnel. Furthermore, the wind velocity field induced by the curved transition section with an equivalent slope of 30 was investigated in detail, and a parameter called the \'velocity stability factor\' was defined; an analytical model for predicting the velocity stability factor was also proposed. The results show that the proposed curved transition section has a better flow transition performance compared with the traditional ramp transition section. The proposed analytical model can also adequately predict the velocity stability factor of the wind field.

Wind loads on a moving vehicle-bridge deck system by wind-tunnel model test

Li, Yongle,Hu, Peng,Xu, You-Lin,Zhang, Mingjin,Liao, Haili Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.19 No.2

Wind-vehicle-bridge (WVB) interaction can be regarded as a coupled vibration system. Aerodynamic forces and moment on vehicles and bridge decks play an important role in the vibration analysis of the coupled WVB system. High-speed vehicle motion has certain effects on the aerodynamic characteristics of a vehicle-bridge system under crosswinds, but it is not taken into account in most previous studies. In this study, a new testing system with a moving vehicle model was developed to directly measure the aerodynamic forces and moment on the vehicle and bridge deck when the vehicle model moved on the bridge deck under crosswinds in a large wind tunnel. The testing system, with a total length of 18.0 m, consisted of three main parts: vehicle-bridge model system, motion system and signal measuring system. The wind speed, vehicle speed, test objects and relative position of the vehicle to the bridge deck could be easily altered for different test cases. The aerodynamic forces and moment on the moving vehicle and bridge deck were measured utilizing the new testing system. The effects of the vehicle speed, wind yaw angle, rail track position and vehicle type on the aerodynamic characteristics of the vehicle and bridge deck were investigated. In addition, a data processing method was proposed according to the characteristics of the dynamic testing signals to determine the variations of aerodynamic forces and moment on the moving vehicle and bridge deck. Three-car and single-car models were employed as the moving rail vehicle model and road vehicle model, respectively. The results indicate that the drag and lift coefficients of the vehicle tend to increase with the increase of the vehicle speed and the decrease of the resultant wind yaw angle and that the vehicle speed has more significant effect on the aerodynamic coefficients of the single-car model than on those of the three-car model. This study also reveals that the aerodynamic coefficients of the vehicle and bridge deck are strongly influenced by the rail track positions, while the aerodynamic coefficients of the bridge deck are insensitive to the vehicle speed or resultant wind yaw angle.

Numerical simulation of the neutral equilibrium atmospheric boundary layer using the SST k-ω turbulence model

Peng Hu,Yongle Li,C.S. Cai,Haili Liao,G.J. Xu 한국풍공학회 2013 한국풍공학회지 Vol.17 No.1

Modeling an equilibrium atmospheric boundary layer (ABL) in an empty computational domain has routinely been performed with the k-ε turbulence model. However, the research objects of structural wind engineering are bluff bodies, and the SST k-ω turbulence model is more widely used in the numerical simulation of flow around bluff bodies than the k-ε turbulence model. Therefore, to simulate an equilibrium ABL based on the SST k-ω turbulence model, the inlet profiles of the mean wind speed U, turbulence kinetic energy k, and specific dissipation rate ω are proposed, and the source terms for the U, k and ω are derived by satisfying their corresponding transport equations. Based on the proposed inlet profiles, numerical comparative studies with and without considering the source terms are carried out in an empty computational domain, and an actual numerical simulation with a trapezoidal hill is further conducted. It shows that when the source terms are considered, the profiles of U, k and ω are all maintained well along the empty computational domain and the accuracy of the actual numerical simulation is greatly improved. The present study could provide a new methodology for modeling the equilibrium ABL problem and for further CFD simulations with practical value.

Analysis and study of compact inductive power transfer systems for EV charging

Ai, Yongle,Hu, Xiaoqi,Li, Xing,Zhang, Xin The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.5

The double-sided LCC topology provides an efficient compensation method for electric vehicle (EV) wireless charging systems. However, the existence of two compensation coils results in an electric vehicle wireless charging device with a large volume, high power consumption, and low efficiency. To solve these problems, this paper proposes a wireless charging structure in which the compensation coils are separately integrated into the transmitting and receiving coils. First, the number of turns of the transmitting coil is optimized to maximize the coupling coefficient of the transmitting coil. Secondly, to minimize the redundant coupling effect, the relative placement of the compensation coils is studied. Based on the proposed coil integration method, it is possible to ignore the redundant coupling between the compensation coils and the transmitting and receiving coils. Then, the Ansys Maxwell and Ansys Twin Builder are used to build a joint simulation circuit to construct the proposed wireless charging system. Simulation and experimental results show that the system output power is 3.09 kW with a gap of 150 mm, and that the transmission efficiency is 95.49%. In addition, the integrated solution has a high transmission efficiency in the presence of front-to-back misalignment and vertical misalignment of electric vehicles.

Tensile Behaviors of Laser-Discrete-Quenched Substrate/Nickel Coating of Electroplated Grinding Wheel

Cong Mao,Yujie Zhong,Yongle Hu,Weidong Tang,Z. M. Bi,Zhaohong Lei,Changchun Jiang,Aimin Tang 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.5

Electroplated grinding wheel has significant advantages, such as longer service life, higher removal rate, reduction of preparation work, reapplication of the wheel bub. Then it is an efficient, green and eco-friendly abrasive tool. In order to reveal the mechanism that the service life of the electroplated grinding wheel is increased by pre-quenched substrate, the tensile behavior and interfacial stresses of the laser-discrete-quenched substrate/nickel coating were studied through tensile experiment and simulation. The results show that random initial cracks appear in the nickel coating over the unquenched zone before the tensile experiment. There is an inter-diffusion region at the interface of steel substrate and nickel coating; in comparison with the unquenched zone, the size of the inter-diffusion region in the laser-quenched zone was decreased significantly (e.g., 1.2 μm in comparison with 2.6 μm). In tensile testing, the coating over the pre-quenched specimen remains bonded with the substrate firmly even the fracture occurs. In contrast, the damages in the forms of blistering, stripping and exfoliating occurred in the coating over the unquenched specimen. When a fracture occurs, there is a significant difference of the ultimate strains of quenched and unquenched zones; the ultimate strain of quenched zone is 0.0714, while that of the unquenched zone is 0.1667. At the bonding interface, the pre-quenched specimen ensured the overall shear stress and the maximum normal stress, which are lower than those of unquenched specimen. The initial cracks in pre-quenched specimen propagate during stretching, the effect of the absorbed strain energy reduces strain mismatch between the substrate and coating at the interface, and this improves the bonding strength at the interface of the laser-discrete-quenched specimen significantly.

Aerodynamic Instability of Stay Cables with Lighting Fixtures

Zhouquan Deng,Haojun Tang,Bo Hu,Yongle Li 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7

In order to decorate the night view for cities, installing lighting fixtures on stay cables of existing cable-stayed bridges is an effective choice, but the aerodynamic characteristics of the stay cables will change significantly. This paper presents a study on the galloping stability of the stay cables equipped with lighting fixtures. The static aerodynamic coefficients were computed using computational fluid dynamics (CFD) simulations, and the reason for the negative slope of the lift coefficient was discussed based on the changes in pressure distributions and flow field characteristics. Wind tunnel tests were further carried out to verify the numerical results. The possible galloping instability intervals for the stay cables with lighting fixtures were calculated. The results show that the existence of lighting fixtures has significant effects on the aerodynamic performance of stay cables. The slope of the lift coefficient becomes negative within several intervals of angles of attack, which indicates the possible galloping instability. The sudden decrease in the lift coefficient is mainly related to the vortex which covers the concave between the lighting fixture and the stay cable and makes the separated flow cannot reattach.

Wind field numerical simulation of a cable-stayed bridge in a mountainous area using improved inlet boundary by CIRFG method

Mingjin Zhang,Yiyan Dai,Bo Hu,Xu Xin,Lianhuo Wu,Yongle Li 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.9

Bridges in mountainous areas are indispensable nodes in transportation networks, and wind resistance capabilities have become a controlling factor of long-span bridges built in mountain areas. Therefore, it is necessary to study the characteristics of wind fields under complex terrain. An improved inlet boundary by fitting the boundary curve was proposed in this study. The inlet fluctuating wind field was generated by the Correlation Improved Random Flow Generation method (CIRFG). The results of the numerical simulations show that the fluctuating wind input generated by CIRFG tallies with the target wind field, which proves the reliability of the proposed method. The method of fitting boundary curves to give inlet wind speed profiles can achieve non-uniform wind profile inputs. The results show the wind direction of the gorge varies significantly by height. The wind speed at the summit will accelerate affected by the terrain. Also influenced by the terrain, the turbulence intensity profiles in the simulated area show an S-shape. The transverse wind and angle of attack are uneven along the main girder, especially near slopes. The conclusions obtained in the study can provide references for the wind resistance of bridges built in mountainous areas.