Drag and Rolling Moment Measurements Using Accelerometer-based Force Balance in a Shock Tunnel

Abstract

A multicomponent force balance was designed to measure the drag and rolling moment using an accelerometer-based technique. The force balance system used a linear ball bush as a new model mount system to minimize the constraint of the test model motion in both the axial and rotational directions. The accelerations of the test model were measured in the axial and rotational directions using accelerometers that were externally mounted on the test model. The drag and rolling moment were recovered from the measured accelerations using the system response functions, which included the dynamic characteristics of the force balance system. The system response functions were determined from the force balance calibration processes by applying a series of point loads in the axial and rotational directions and deconvolving the resulting accelerations. The drag and rolling moment measurements on the wedge model, including the flaps, were performed in a shock tunnel with a test time of approximately 3 ms at a nominal freestream Mach number of 6. A computational fluid dynamics (CFD) analysis assuming a laminar boundary layer was performed. Good agreement was obtained between the measured and calculated results. An uncertainty analysis of the measurements was conducted with regard to the influence of the fundamental properties of the test condition and force balance system.