On the location of the laser energy deposition region in wave drag reduction

Abstract

A two-dimensional numerical simulation is carried out to determine the optimum location of the concentrated laser energy deposition region for maximum wave drag reduction of a blunt body. A 25.4-mm-diameter semicircle, Mach 3.45, and 50 mJ pulse energy are chosen as the representative blunt body, free-stream Mach number, and magnitude of the deposited laser energy, respectively. The location of the energy deposition region is varied discretely from 21 to 50 mm upstream of the center of the semicircle along its axis of symmetry. The lower limit of the distance is just upstream of the blunt body bow shock along the axis of symmetry. It is found that for the assumed conditions, the maximum wave drag reduction happens at the lower limit of the distances. A time-resolved analysis of the interaction between the laser-induced blast wave and the bow shock is carried out to arrive at the conclusions. It is observed that the blast wave reflects as an expansion wave from the bow shock for the 21 mm case, whereas the reflected wave is a shock wave for all other cases. The time history of the static pressure at the blunt body nose and wave drag per unit depth on the blunt body are also provided for the above locations of the energy deposition region to justify the inferences.