title: Common-path heterodyne laser-induced thermal acoustics for seedless laser velocimetry.
abstract: We demonstrate the use of a novel technique for the detection of heterodyne laser-induced thermal acoustic signals that allows the construction of a highly stable seedless laser velocimeter. A common-path configuration is combined with quadrature detection to provide flow direction, to greatly improve robustness to misalignment and vibration, and to give reliable velocity measurement at low-flow velocities. Comparison with Pitot tube measurements in the free stream of a wind tunnel shows root-mean-square errors of 0.67 m/s over the 0-55-m/s velocity range.
authors.forename: Roger C
authors.initials: RC
authors.lastname: Hart
authors.forename: G C
authors.initials: GC
authors.lastname: Herring
authors.forename: R Jeffrey
authors.initials: RJ
authors.lastname: Balla