Determination of Aerodynamic Coefficients from Shock Tunnel Free Flight Trajectories

Abstract

ISL’s shock tunnel is used as a short blowing ground testing facility to analyze the 6 degrees of freedom motion of a free flying body in order to determine its aerodynamic coefficients. The “Free-Flight Force Measuring (FFM) Technique” was originally described in former literature and has been further developed at ISL’s Shock Tube Laboratory using high-speed cameras for observing the translation and the rotation of the body. This paper presents the three tasks that are required to perform the data reduction: 1) measurement of the time-dependent flow parameters as a basis to compute a theoretical motion, 2) accurate observation of the translational and angular motions of the body and 3) estimation of the aerodynamic coefficients using a least-square fit of the measurements to the theoretical motion. The results of the process are tested at Mach 3.0 and Mach 4.5 against the reference aerodynamic data of an Explosively Formed Penetrator (EFP) model.