The original closed-jet test section designed for use in a 36-in. water tunnel with an air-bubble resorber was cylindrical and 2.18 diameters long. It was followed by a parabolic transition, 0.5 diameter long, to the 7 degree diffuser cone. The effect of diverging test section with a longer diffuser transition in decreasing the pressure gradients and, as a result, lowering the cavitation indices attainable is discussed in this report. Tests on a one-sixth scale model and analyses indicate that a test section diverging at a total angle of about 0 degrees 9.6' would be expected to have an essentially constant core pressure throughout the length of the test section. This divergence angle followed by a nearly 1-diameter transition should result in a test section which can be operated at cavitation indices as low as 0.025 or 0.030 at velocities of 84.5 fps.
Supplement I to Project Report No. 29; A Diverging Closed-Jet Test Section for a Water Tunnel
Prepared for the David Taylor Model Basin, Department of the Navy under Bureau of Ships Contract N600s-s-11459
Olson, Reuben M..
Model Studies of a Water Tunnel with an Air-Bubble Resorber Supplement I.
St. Anthony Falls Hydraulic Laboratory.
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