Measurement and visualization of a two-dimensional velocity distribution by laser speckle photography using a He-Ne gas laser. (2nd report. The application to the coaxial cylindrical couette flow and the measuring accuracy of the two-dimensional velocity field).

Abstract

The laser speckle photography technique has the advantage of obtaining a whole instantaneous two-dimensional velocity distribution as the vector quantity. However, there have been few reports on the measuring accuracy of this technique. Furthermore, most of these reports employed a high-power laser, e.q. an argon laser or a ruby pulse laser, as a light source. In this study, a He-Ne gas laser is employed in order to enhance the validity of the technique. This technique is applied to the coaxial cylindrical Couette flow to discuss the measuring accuracy of the velocity vector, especially the velocity direction. The measuring results agree with the analytical solution within ±10 % at the local scalar quantity of the velocity νθ(γ)=0.01∼0.40 m/s, and within ±2 degrees in the velocity direction.