Flow sensing through unsteady pressure measurements during transverse wing–gust encounters

Abstract

Flight vehicles can optimize their performance by sensing unsteady flow phenomena and leveraging this information to improve decision-making and actuation. This study experimentally investigates the use of surface pressure measurements as unsteady flow sensors during large-amplitude transverse wing–gust encounters. An instrumented wing model is developed to overcome difficulties associated with unsteady pressure measurements in water towing tank facilities. The measurement system is validated through steady and unsteady experiments and is used to study the unsteady pressure distributions associated with transverse wing–gust encounters. Concurrent analysis of the pressure distributions and flowfields yields the following flow event sequence for high gust ratio (GR) experiments: As the wing enters the gust, a large suction peak forms on the leading edge. The suction peak widens and eventually splits into two distinct peaks. The secondary suction peak is associated with the leading-edge vortex (LEV) and its suction strength is found to be proportional to the gusting flow dynamic pressure, \(\textrm{GR}^2 + 1\). Integration of the sectional pressure distributions resulted in accurate estimates of the overall wing loads during the vortex formation stage of the dynamic stall process but not during the vortex separation stage. Dynamic stall initiation is shown to be associated with an inflection point on the leading-edge suction transient and an abrupt drop in the leading-edge pressure gradient. The timing of LEV formation is found to be associated with a maximum in leading-edge suction and an increase in leading-edge pressure gradient.