A STUDY OF TWO OPPOSING PLANAR AIR JETS

Abstract

<p>This thesis tackles the behavior of two planar shaped opposing air jets. The word opposing means that the two air jets are positioned against each other to have a common center-line so that they impinge on each other. Opposing planar jets have several applications in industry which include: galvanization, chemical mixing processes, and combustion. Opposing planar jets are found to produce high level low frequency acoustic tones. In this study, the acoustic response of the opposing planar jets is investigated for different operating conditions. Acoustic tone analysis is performed for a wide range of jet exit velocities and separation distances between the two jets. Results show that the jets produce strong acoustic tones over the whole investigated range of test conditions. The acoustic response depends on the operating conditions of the jets and the acoustic tone is found to be generated by a self-sustained flow oscillation of the two jets.</p> <p>In order to further understand the reported oscillation phenomenon, particle image velocity (PIV) is utilized. Images of the oscillating flow field are acquired and image analysis is performed to obtain various flow dynamic properties. A computational fluid dynamics simulation is performed to help in highlighting the oscillation behavior of the jets. Results reveal that the jets exhibit anti-symmetric ‘’flapping’’ oscillation behavior. The jets are found to initially deflect away from their common centerline due to high stagnation pressure in the impingement region, while they deflect back to their common centerline due to cross stream oscillating velocity in the entrainment regions around the jets.</p>