ABSTRACT
A simple and low cost technique for visualization and quantitative analysis of water flow fields around aquatic animals is described based on particle tracking velocimetry (PTV). Stroboscopic or continuous 2D sheet illumination with a slide projector and a rotating shutter is used to visualize the flow of neutrally buoyant plastic particles suspended in the flow field. The flow pattern is recorded by photographing the streak lines of moving particles using long exposure times, or by filming them with a video camera. Digital photos stored on KODAK photo CD, or video frames digitized by a frame grabber, are analyzed on a MACINTOSH computer using “Colorlmage” software. Video frames are post-processed by the software by superimposing them onto one image. Velocity vectors are obtained by measuring the distances between traces of the same particle and the direction of the streak line. Applications of the technique include the analysis of the flow field of a swimming fish and the water currents generated by decapod crustaceans.
