Week 10: Modeling and Simulation of flow around an Ahmed Body

introduction

The Ahmed body was first created by SR Ahmed in his research "some salient feature of the time-averaged ground vehicle wake" in 1984. Ahmed body is the benchmark model for aerodynamics simulation tools.

the simple geometrical shape has a length of 1.044 meters, a height of 0.288 meters, and a width of 0.389 meters .it also has 0.5-meter cylindrical legs attached to the bottom of the body and the rear surface has a slant has falls off at 40 degrees.

Ahmed's body represents the simplified ground vehicle geometry of bluff body type .its shape is simple enough for accurate flow simulation and retains some important practical features relevant to automobiles body. this helps us to calculate the turbulent flow field around the simple car using the k-epsilon model'

some of the key characteristics which can be obtained from the simulation of Ahmed body are velocity magnitude, pressure magnitude, wake region, drag force, lift force

geometry

setup

results

C_L = L/qS

q = (rU²/2)

L=20 N S=0.1253

D=1.001

cl=2*20.0676/(1.255*40^2*0.1253)

cl=0.2788

D=52

v=40

cd =2*52/(1.255*40^2*0.1253)

cd=0.4783

both experimental data and simulation data plots

x=-13 mm

x=-263 mm

x=37

x=87

x=-113 mm

x=-63 mm

x=187mm

x=137

conclusion

• both experimental data and simulation data plots matched

• drag coefficient and lift coefficient calculated and analyzed