Susceptibility of a Parallelogram Type Skin Friction Balance to Rotational Motion

摘要

The Flight Dynamics Directorate at WPAFB is currently involved in skin frictionresearch in the Mach 3 and Mach 6 High Reynolds Number (HRNF) facilities. The current instrument used to measure the shearing forces is a modified version of the NASA Langley parallelogram type skin friction balance tailored for operation in adverse thermal and dynamic environments. Although the balance has provided excellent results in both the Mach 3 and Mach 6 HRNF facilities, some concerns exists with the data at the very lowest stagnation pressures at Mach 3. At these low pressure (at P sub os of 80 psia) the balance and other measuring instruments experience erratic signal outputs. The concern therefore is whether the erratic behavior of the balance is due to tunnel vibration at low stagnation pressures or to aerodynamic conditions within the tunnel. A laboratory test was devised to determine at what frequency and amplitude the balance would experience erratic behavior. This report investigates the vibration test and analysis on the skin friction balance.