Low cost, high resolution DPIV for measurement of turbulent fluid flow
An optimized cross-correlation based Imaging Velocimetry system is described and its performance is evaluated in numerical and physical experiments. Given a discrete image array pair, the flow seeding and image processing parameters are optimized to maximize displacement accuracy, regardless of the computational cost; collectively these techniques are known as Correlation Imaging Velocimetry (CIV). Order of magnitude improvements over standard DPIV methods can readily be obtained, allowing high resolution measurements to be made with low cost standard resolution cameras. Fundamental limits on the measurable range of length, velocity and vorticity scales are identified, and related to those encountered in homogeneous, 3D turbulence. The current restrictions apply to all imaging velocimetry measurements; some paths for future research that are likely to be profitable are identified, together with some that are not. Extensive use of CIV in this and other laboratories has allowed direct verification of these optimization principals.