چكيده به لاتين
In this study, in order to address the effect of crosswind on Tractor-Semitrailer by considering the aerodynamic centers and coefficients of trailer and tractor separately, first aerodynamic coefficients of trailer and tractor have been calculated. For this purpose, Vehicle geometry has been meshed as a combination of unstructured and prismatic grids. Then numerical simulation was conducted in FLUENT software for different crosswind velocities through using K-ε Realizable Turbulent model. As the next step, by using the calculated aerodynamic coefficients, Tractor-Semitrailer movement under crosswind effect was studied by TruckSim software and the results of the case in which aerodynamic centers and coefficients were chosen separately was compared with the case in which these factors were chosen dependently. Finally, the movement was controlled through LQR method and braking differential actuator and required control momentums for controlling yaw rate of vehicle, was proposed.
The results show that by increasing crosswind velocity and keeping vehicle velocity constant, drag coefficient is slightly decreased and side force coefficient is increased. Increasing crosswind leads to reducing drag coefficient and side force coefficient of tractor and increasing in Semitrailer coefficients. Increasing crosswind velocity aligns flow wakes with resultant forces acting on Vehicle. Vehicle behavior is different in case where dynamic coefficients and centers was separately chosen from the case in which they were chosen dependently. Required control momentum for Tractor and Semitrailer also shows that control momentum is different in two cases. When coefficients were chosen dependently, less control momentum is needed. Hence, choosing centers and coefficients dependently, provides more acceptable results compared to the cases in which those factors were chosen separatly.
Keywords:
Tractor-Semitrailer, Crosswind, Numerical Simulation, TruckSim
