Effects of Repetitive Laser Energy Deposition on Supersonic Duct Flows

An experimental study was conducted to examine the effects of repetitive energy deposition on the supersonic flow characteristics over a duct system with a central conical compression surface. Boundary-layer separation on the compression surface could induce flow instability in pulsation and resonant modes. At subcritical operation, this flow instability became stronger and the "big buzz" phenomenon occurred. To control these undesirable operations, repetitive laser energy deposition was done with a repetition frequency of up to 60 kHz, which resulted in a reduction of flow separation on the compression surface. It was also observed that flow oscillation characteristics at the two modes were modified; total pressure inside the duct chamber was increased and the big buzz was significantly suppressed.