Investigation of Blockage Effects from Flow About Circular Cylinders in a Two-Dimensional Wind Tunnel

Citation

Schmidt, Louis Vincent (1950) Investigation of Blockage Effects from Flow About Circular Cylinders in a Two-Dimensional Wind Tunnel. Engineer's thesis, California Institute of Technology. doi:10.7907/1NSH-2G22. https://resolver.caltech.edu/CaltechTHESIS:09302010-144157909

Abstract

In these investigations a study of the blockage effects encountered in wind tunnel testing was made. Emphasis was placed on obtaining perceptible values of wake blockage in order to check the reliability of approximate derivations that are based on the assumption of small wakes. A bluff body (circular cylinder) was chosen for these investigations since it develops a pronounced wake. Three cylinders of varying size were employed in order to obtain a variation in the magnitudes of the blockage effects. The combined influence of surface irregularities such as static pressure orifices and the vertical walls resulted in the flow over the cylinders exhibiting three-dimensional characteristics. An investigation of these effects was conducted in order to determine means of circumventing three-dimensional characteristics. Two-dimensional flow characteristics were realized after the point of flow separation on the aft portion of the cylinder was made uniform in the spanwise direction. This was accomplished by means of separation strips fastened to the cylinder forward of the point of maximum thickness. After the realization of two-dimensional flow characteristics in the test section, the original purpose of the test was carried out to a limited extent. Experimental measurements of wake blockage effects were compared with the predicted values that are based on approximate derivations for cases where comparison could be made.

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