A low cost laser-speckle photographic technique for velocity measurement in slow flows

A low cost, low power laser-speckle photographic technique has been developed and is duscussed for the measurement of point velocities in slow laminar flows. The technique is particularly suitable for axisymmetric flows where the two velocity components can be easily measured. The accuracy of the technique is established by measurement of the velocity distribution for Poiseuille flow and from data obtained for acceleration of an inelastic Newtonian fluid through a four-to-one circular contraction. Preliminary results are also presented in the contracting flow field for a non shear-thinning highly elastic fluid. These data are particularly significant for verification of finite element numerical solutions currently being developed for viscoelastic fluids in circular entry flows.