In a limno-corral (diameter 12 m, depth to sediments 10 m), located in Baldeggersee (Switzerland), vertical mixing has been measured during more than one year and compared to the conditions in the open lake (maximum depth 65 m, surface area 5.3 kin2). The temperature method by McEwen and Hutchinson yields K z values between 5x 10 -2 cm2s -I at the upper boundary of the thcrmocline and 2x 10 -3 cm2s -I at the bottom, a value near the molecular diffusion of heat at 4~ (1.36x 10 -3 cm2s-t). K z calculated from profiles of excess radon-222 generally agree with those from the temperature data.Compared to the open lake, the corral has a more shallow epilimnion. However, during calm meteorological conditions, vertical mixing in the upper 10 m is similar outside and inside the corral.

Design studies are described for two recently completed large scale hydroacoustic test facilities (one of which is the world’s largest). These recirculating water tunnels have a different configuration than conventional tunnels, and special hydrodynamic design studies were required to evaluate and optimize the performance of some critical components. This paper considers the flow quality in the test section as influenced by the design of the contraction and the turbulence management system. Numerical modeling and experimental work were used to arrive at an acceptable nonsymmetrical nozzle design. Studies were also made of a turbulence management system using honeycombs rather than screens as typically used. Although design goals for turbulence levels were met, this study indicated that additional research in the area of turbulence management is necessary before there is a complete understanding of the overall process of turbulence attenuation.

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The St. Anthony Falls Hydraulic Laboratory has been involved in the hydrodynamic design of large cavitation facilities, which require a high performance axial flow pump that is cavitation free to meet stringent design conditions. As cavitation has been shown to be the largest noise source in an otherwise well designed facility, it must be eliminated for the design range of flow conditions. To reduce the possibility of blade cavitation it is desirable to have a near uniform, or at least, a near symmetrical approach velocity distribution at the pump inlet. The design of flow facilities to achieve such an inflow was the subject of extensive investigations. These investigations consisted of both numerical and physical modeling of critical components in the test loop. The influence of these components, which included the contraction, diffuser, and turning vanes was carefully documented. The combination of the two modeling techniques will be demonstrated as an effective design tool for a high performance, hydrodynamic test facility.