Consideration of Factors Influencing Closed Jet Wind Tunnel Blockage Corrections for Road Vehicles.

Experimental studies of wind tunnel blockage for road vehicles have usually been conducted in model wind tunnels. Models have been made in a range of scales and tested in a working section of fixed size. More recently CFD studies of blockage have been undertaken, which allow a fixed vehicle size and the blockage is varied by changing the cross section of the flow domain. This has some inherent advantages. A very recent database of drag and lift coefficients for different road vehicle shapes and simple bodies examined in a closed wall tunnel with a wide range of blockage ratios has become available and provides some additional insight into the blockage phenomenon. This paper shows how some of the parameters influencing blockage can be derived from the CFD data and provides some tentative proposals for correcting the measured drag and lift coefficients.