Three-Dimensional Flow Measurement by Digital Holographic Particle Image Velocimetry with Spatio-Temporal Derivative Method : Evaluation of the Measurement Accuracy by Numerical Simulation

In this paper, we present a digital holographic particle image velocimetry (DHPIV) technique with a spatio-temporal derivative method for velocity measurement in 3D space and the results of evaluating on its measurement accuracy. In this technique, hologram patterns are observed as digital images using an electronic camera, such as CCD or CMOS, and image reconstruction is carried out on a personal computer. Since an in-line observation system is utilized in conventional digital holography, a numerically reconstructed image is considerably enlarged in the depth direction and its depth resolution is extremely low; hence, the measurement accuracy in the depth direction is inaccurate in a digital holographic measurement. To overcome this difficulty, we apply a spatio-temporal derivative method to this technique for the detection of particle displacement along the z-axis. In a numerical simulation, measurement accuracy is evaluated for a multi particle model and a cubic cavity flow model. Furthermore, we examine the effect of noise on displacement measurement accuracy for numerically constructed noisy hologram patterns.