Experimental investigation of linear energy deposition using femtosecond laser filamentation in a m=3 supersonic flow

The goal of this study is to demonstrate experimentally the “Laser Spike” concept in a supersonic flow. The “Laser Spike” uses a thin filament of plasma created by a femtosecond laser. This plasma filament formed by the TeraWatt laser pulse acts as a linear energy deposition upstream of the shock wave created by a blunt body. It has been found that the laser energy deposition induces a significant transient reduction of the drag. This reduction has been quantified using a drag balance. These experiments have been simulated numerically by modeling the plasma filament as a source term in the energy equation. It is shown that the plasma filament created by the ultra-short laser pulse forms a low-density heated core that interacts with the detached bow shock. This interaction produces an inflating recirculating bubble and leads to a transient reduction of the drag. These findings demonstrate the interest of ultrashort laser for flow control. Drag reduction, flow control and trajectory control are among the possible applications of the “laser spike” concept. Sonic boom alleviation could also be improved with this device.