SUBMERSIBLE PIV SYSTEM USING FIBER OPTIC LASER DELIVERY AND A DIGITAL CAMERA

摘要

A submersible particle image velocimetry (PIV) system foruse in oceanographic field studies has been designed and built.The primary purpose of this instrument is to measure thecharacteristics of the continental shelf bottom boundary layerincluding the velocity profile, Reynolds stresses, vorticitydistribution, dissipation and turbulence spectra. Fiber opticlaser delivery is used in this system. The choice of a laser andoptical fiber to transmit the large energies required for PIVimaging is discussed. The laser is a dual-head, flashlamppumped dye laser which generates up to 350 mJ/pulse. Theoptical fiber has a core diameter of 400 μm. To date, thehighest energy output transmitted through this fiber withoutdamage has been 126 mJ/pulse. The coupling and collimatingoptics required to avoid fiber damage and to maintain lowoutput beam divergence are outlined. A digital camera with1024×1024 pixel resolution (15 pairs of frames per second) isused for data acquisition.Other components of the system include: a digital compassand biaxial clinometer to provide an accurate reference frame; ahigh precision pressure sensor to give depth and wave heightmeasurements; and a high-speed serial data link for datatransmission and system control. The entire system is mountedon a hydraulic scissor jack and a motorized turntable to allowalignment with currents and traversing of the boundary layer.