A new tool for flow field measurement is in use at the David Taylor Model Basin (DTMB) The Digital Particle, Image Velocimetry (DPIV) technique developed by Willert and Gharib (1) has been used to measure the flow fields of a 2D standing wave and of a laminar vortex pair interacting with 2D traveling waves at a free surface. Application of the DPIV technique to free surface flows introduces new measurement challenges a the position of the non-stationary surface is not known a priori, but must be determined from the video images themselves.
The initial application of the DPIV technique at DTMB has shown that it is a useful tool for flow field measurement and visualization with a high throughput rate. It is possible to obtain flow field measurements in almost rea1 time, and the results are immediately available for use in directing experimental efforts. It is envisioned that a myriad of applications will be found for the DPIV technique at DTMB, including the mapping of flow fields around hull forms, appendages, and propulsors.