Drag Reduction of Blunt Body in a Supersonic Flow with Laser Energy Depositions

Measurements of the drag over a flat-nosed cylinder with repetitive laser pulse irradiations ahead of it were conducted in a Mach-2, in-draft wind tunnel. Laser pulses were focused using a plane-convex lens fabricated on the nose of the cylinder at a repetition frequency of up to 10 kHz and an effective power of 70 W at a maximum. The drag was measured using a low-friction piston which was backed by a load cell in a cavity at a controlled pressure. The measurement was so delicate that careful implementation was necessary to accurately determine the amount of drag reduction. A drag reduction about 1.4 N which corresponds to an efficiency of energy deposition over 1400 % was obtained. Nomenclature A = projection area of cylinder body D = cylinder diameter F = force f = laser pulse repetition frequency L = distance between cylinder head and laser focus P = pressure P0 = atmospheric pressure Psub = pressure in sub-chamber t = time W = time-averaged laser power α = fitting constant

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