Force prediction during transverse and vortex gust encounters

摘要

This paper proposes a flowfield-based force prediction method for both transverse and vortex gust encounters, and examines the behavior of the maximum lift coefficient experienced during the transverse gust encounters. A sine-squared transverse gust was created in a water towing tank by using a water jet, whilst a vortex gust was created in a water channel by rotation of an upstream gust generator plate. Forces and flowfields were acquired for both gust types and examined. Average velocity variations in time were obtained along an upstream line, and variations in the effective angle of attack and lift coefficient were then computed based on these average velocities. A sensitivity study was performed, and coupling between the wing and the transverse gust was found to be important. For both gust types, lift coefficients from the measurements and the predictions were found to agree well with each other if the prediction results were to multiplied with the span of the wing. The transients in the lift force were observed to match the variations in the effective angle of attack. Furthermore, the peak lift coefficient experienced by a wing encountering sine-squared transverse gust was found to depend on the maximum effective angle of attack rather than individual values of the geometric angle of attack or the gust ratio.