Measurement and visualization of two-dimensional velocity distribution by the laser speckle photography using a He-Ne gas laser. 1st Report. Application to the free convection field around a vertical plate in air and measuring accuracy.

Abstract

The speckle photography technique is one of the novelest velocity measurement methods. This study examines the possibility that this technique will become practically applicable. In this study this technique is applied to the laminar-free convection field around an uniformly heated vertical plate in air. Moreover, a He-Ne gas laser is employed as the light source in order to enhance the validity of this technique. The measuring results agree with a similar solution within ±10% at the local velocity u(y)=0.057∼0.185 m/s. It becomes clear that this technique using a He-Ne gas laser can obtain a whole instantaneous two-dimensional velocity distribution with fair accuracy.