Experimental and numerical studies on multi-jet impingement flow characteristics in a double-wall structure under rotating conditions

This study employs time-resolved particle image velocimetry technology to investigate the flow field characteristics of a double-wall jet structure under both stationary and rotating conditions. The jet rotation number range from 0 to 0.08, covering both clockwise and counterclockwise rotations, with a jet Reynolds number of 4000. The dimensionless jet-to-target spacing is 2. In order to elucidate the flow mechanisms based on experimental results and provide complementary insight, validated numerical simulations under conditions identical to the experiments were conducted. This paper considers average velocity and Reynolds stress and utilizes the proper orthogonal decomposition method to study flow characteristics. The results indicate that the rotation-induced Coriolis force, centrifugal force, and radial pressure gradient in the radial direction influence the jet to deflect. The pressure gradient generated by the centrifugal force weakens its effect, making the jet deflection primarily dominated by the Coriolis force. The deflection direction and degree of the jet differ with the rotation direction and increase with the rotation number. When the rotation direction is reversed, differences in the direction of the force acting on the fluid lead to variations in the secondary flow structures of the jet; the secondary flow structures within the impingement holes exhibit two-vortex or four-vortex structures under counterclockwise or clockwise rotation, respectively. At the highest rotation number, jet deflection intensifies mixing with the surrounding fluid, resulting in a reduction of about 30% in the velocity peak compared to the stationary state but an increase of approximately 0.6 times in turbulent kinetic energy.