Abstract
An experimental investigation is performed to directly measure the velocity field across the fluid-porous medium interface using the method of particle image velocimetry (PIV) in a refractive-index matched system. The test section consists of a rectangular channel bounded on one side by a cavity filled with spherical particles arranged in cubic formation. Velocity measurement at the pore level of the porous cavity is made possible by matching the refractive index of the fluid with those of the channel and the spherical particles. In the PIV approach, digital images of the flow field were obtained in successive frames, which, upon processing to detect particles' locations and application of tracking algorithms, yielded the instantaneous velocity across the interface.