Artificial wind gust generation based on an adaptive nozzle design

Abstract

In a former study carried out by Wood et al. (2022) and Wood and Breuer (2023) a novel approach for the generation of artificial wind gusts in a wind tunnel setup was presented denoted “the paddle”. The device generates wind gusts by dynamically blocking the nozzle outlet area with a rigid plate inducing a sudden rise and drop of the velocity signal. This procedure leads to highly reproducible wind gusts within a certain region of the test section depending on the kinematic settings of the paddle. However, outside of this restricted region the flow is dominated by a highly fluctuating flow regime. This effect limits the space of the test section, which can be used for experimental investigations. In order to reduce the negative effects of the paddle, a modified design of the gust generator is presented in this contribution. For this purpose, a second wind tunnel is designed using the same automation equipment as the paddle. However, the new setup comprises a nozzle with a fully movable upper contour in order to generate smoother wind gusts. The working principle and a comarison between the gusts generated by the paddle and the new device are presented based on a closely matched motion pattern of the servo driver unit and an identical blocking ratio. In summary, the adaptive nozzle reduces the drawbacks of the paddle such as the large flow separation and the velocity undershoot on the falling flank of the gust. Additionally, previously not attainable gust shapes can be generated leading to a greater variety of flow conditions for experimental studies on fluid-structure interaction (FSI).