Wave Drag Reduction of Blunt Bodies Using Laser Sustained Energy Deposition In Argon Atmosphere

Abstract

Laser-induced energy deposition has been proposed for an effective flow control concept in super-and hypersonic transportation. Especially for blunt bodies the strength of the normal shock waves can be significantly mitigated by a modification of the gas temperature commonly generated by spark-discharge or repetitive laser-induced gas breakdown. The paper presents experimental and computational results of a laser-induced, non-repetitive gas heating concept in supersonic argon flow. Ignited by the gas breakdown of a Q-switched Nd:YAG laser a focused continuous wave CO2 laser sustains a plasma. The pressure distribution of a miniature hemisphere is measured by four static pressure taps and determines a drag reduction of up to 55 % for the Mach number 2.1 and of up to 60 % for the Mach number 2.7 using an average pulse power of up to 5.4 kW for a typical duration of 700 µs.

Objectives of Laser‐Induced Energy Deposition for Active Flow Control

“…Both measurement techniques disregard reflection and refraction losses of the transmitted laser beam. = 1 ± 0.13 for Mach 2.7 at p 2 = 6.6 bar and η = 0.58 ± 0.14 for Mach 2.1 at p 2 = 6.2 bar, using w ∞ for the free jet velocity [23]. The amount of deposited energy versus stagnation pressure is comparable for Mach 2.1 and Mach 2.7.…”