DEVELOPMENT OF A 6X18 INCH RHEOLOGY TUNNEL FOR EXPERIMENTAL FLUID-DYNAMICS INVESTIGATION

The Ohio State University (OSU) and the Cleveland Clinic Foundation (C CF) developed a 6 x 18 inch low velocity Rheologic Research Tunnel to do flow visualization and other experimental fluid studies, particular ly on scaled-up models of cardiovascular devices, such as the CCF's In novative Ventricular Assist System. The large test section (TS) permit s detailed data to be obtained that would be inaccessible with a small er test prototype. A particular feature of the OSU-CCF program is the use of a non-Newtonian blood analog (NNBA), so the effect of the shear -thinning behavior of blood on the local development of separation, st agnation, and now patterns can be studied. The TS can simulate a press ure driven slit flow of 6 x 18 in., or the external flow around a vane or blade having an aspect ratio of 1. Maximum pressure is 8.5 psig, w hile the maximum velocity is 21.7 in/sec. The fluid supply tank has a capacity of 500 gal of NNBA and, with its associated filtration and ci rculation systems, can be adapted to studies of large transparent mode ls better studied outside the TS. Using 2 pumps, flow rates of 98-610 gal/min can be provided. Instrumentation includes thermistors, a 48 po rt pressure scanner with pressure transducers, a data acquisition syst em, and a digital video camera. Dye and hydrogen bubble systems have b een developed. Development of such a facility presents problems not en countered in more typical water tables or wind tunnels. These include fundamental issues such as providing a uniform flowfield; practical is sues with respect to priming, operating, and obtaining data from the s ystem; and safety considerations. For the very large volume of NNBA, a xanthan gum solution is used, whose shear-thinning behavior depends n ot only on concentration, but also on age and prior shear history. The lessons learned are presented, permitting others to efficiently devel op systems suitable to their testing needs.