Improvement of Pressure Recovery in a Duct by Repetitive Laser Energy Depositions

Impacts of energy deposition approach on performance of supersonic flow over a duct system were experimentally examined. Without using energy deposition, in the case of duct’s normal operation, supersonic flow was found being separated and weakly fluctuating at the duct’s compression surface. Additionally, in the case of unstable operation, supersonic flow was found strongly oscillating at both around the duct entrance and inside the duct chamber. To control these unfavorable influences to duct performance, energy deposition approach with repetition frequency up to 60 kHz was applied. Single energy pulse was confirmed to be able to suppressed flow separation. On the other hand, repetitive energy deposition not only could moderate flow separation but also increase total pressure of the internal flow, though the effectiveness highly depends on applied deposition frequency. Moreover, by applying repetitive energy pulses at 60 kHz, flow oscillation in the case of the duct’s unstable operation could be suppressed, and flow was stabilized.