An Experimental Investigation of Blocking in a High-Speed, Closed Wind Tunnel Using the Wall Pressure Method

Author: Francis, Donald Lowell

Year: 1949

Degree: Engineer's thesis

Advisor: Bell, Richard William

Committee Member: Unknown, Unknown

Option: Aeronautics

DOI: 10.7907/V893-YJ92

Abstract

The purpose of this investigation was to determine the possibility of using a semi-empirical, wall pressure method to determine wind tunnel blocking corrections in the transonic range. Included are axial distributions of velocity increments at the wall in the presence of the wing models. The main results are presented in the form of comparisons of the blockage corrections determined by the semi-empirical method with the blocking corrections obtained by direct calculation. The models used in this investigation were reflection-plane-mounted wings of various sizes and sweep angles and one two-dimensional wing. Data for wings at moderate angles of attach are included, when available.

The results indicate that the corrections obtained by the semi-empirical method agree with those obtained by direct calculation in the range of Mach numbers where agreement is expected. The semi-empirical corrections become rapidly larger than the calculated corrections as the critical Mach number of the wing is exceeded. The magnitudes of the differences in the transonic range are sufficiently large to warrant the application of the semi-empirical method to transonic wind tunnel tests.

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