Active Noise Control of Supersonic Impinging Jet using

This thesis concerns an active noise control of supersonic impinging jet flow using un-steady microjet injection. Supersonic impinging jet involves several problems such as lift loss, ground erosion, significant noise pollution, and sonic fatigue, all of which are dominated by impinging tones mainly caused by well-known phenomenon, the feed back loop. The main goal of this study is to achieve uniform and consistent noise reduction in the entire range of jet operating condition, by means of intercepting this feed back loop. Experimental investigations on ideally expanded Mach number 1.5, supersonic impinging jet flow were carried out at the scaled supersonic experimental facility. The actuator used for active control is composed of pulsed microjets, utilizing a fraction of mass flow rate needed with steady microjets. Two means of producing pulsed microjet were introduced; one with a rotating cap, pulsing at 16- 100Hz, and the other developed based on the principle of Hartmann tube, pulsing at 4.4- 6.1kHz, referred to as high frequency actuator. Control parameters related to pulsed microjet injection with rotating cap were varied to evaluate their effects on suppression o