Effect of Rotating Cylinder on the Drag Force of A Road Truck Vehicle

Abstract

The effect on aerodynamic drag of a truck by controlling the boundary layer separation using a rotating cylinder on leading edge of the truck-trailer is investigated numerically. The flow was assumed to be steady, incompressible, turbulent, and two-dimensional passing over the top surface of the truck. The boundary condition for all the boundaries of the truck was set as well as the cylinder was treated as a moving wall with a specific rotational velocity. The developed computational algorithm is tested for the flow over a flat plate (8m) long with various free stream inlet relative velocity (U∞) which are considered the same as truck velocity and has the values (40, 60, 90, and 120) km/h. The effect of cylinder diameter (10,20,30,and 40) , rotational speed (1000-5000 r.p.m) and free stream velocity on the aerodynamic drag and pressure distribution of the flow field were investigated. The governing equations which used are the continuity, momentum, and the (K-ε) turbulence model. These equations are approximated by using a finite volume method, with staggered grid and modified SIMPLE algorithm. A computer program in FORTRAN 90 is built to perform the numerical solution.The numerical results show that, the optimum cases for inlet free stream relative velocity (U∞) values( 40,60) km/h, a significant reduction of drag coefficient equal to 80% and 77% respectively was obtained by useing a speed of rotation and diameter size equal to 5000 r.p.m and 40 cm , for (U∞) value( 90 )km/h a reduction equal to76%, and for (U∞) equal to (120) km/h a reduction equal to 60% was obtained . These optimum results lade to reduce the effect of the aerodynamic drag on the vehicle by delaying the separation zone of boundary layer and enhancing the pressure gradient of the flow field. Comparison of the results with the available previous published experimental and fluent program results was investigated.