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National Aeronautical Establishment - 1977 -Analysis of Wall Interference Effects on Onera Calibration Models in the NAE 5ft. x 5ft. Wind Tunnel

'me experimental part of the present investigation was performed in the N AE 5-ft. X 5-ft. 
wind tunnel in the winter of 1974-75 as a part of the international program, initiated by ONERA, 
Reference 1. The main puQose was to compare test results on a series of geometrically similar models 
from various European and North American wind tunnels in an effort to improve the existing knowledge 
Of scale effect and wind tunnel interference. The second objective of N AE was to assist Dilworth, 
Secord, Meaøner & Associates (DSMA) in fulfilling the contractual commitment to provide training for 
one of their clients in testing in a high performance blowdown wind tunnel. 
Reviews of results and analyses of the test data from wind tunnel facilities where the ONERA 
models were tested prior to NAE can be found in References 1-7. 
Of the four aircraft models manufactured by ONERA only three, the Ml, Ma, and M5 models 
entered the NAE test facility, see Figure 1. ONERA's equivalent axisymmetric bodies were not included 
in the program, since investigation of lift interference rather than blockage Was Of prime concern. The 
model blockage ratios, based on the maximum section in a plane normal to the wind tunnel axis (about 
50% greater than the fuselage cross-section) are given in Table 1. 
The problem of subsonic lift interference on three-dimensional models in wind tunnels with 
perforated walls has been dealt with in a number of theoretical papers in the last couple of years. An 
approximation method based on the Fourier transform technique developed in Reference 8 for solving 
the two-dimensional problem, was reported in Reference 9. Since the solution is constructed in the 
form of series of velocity potentials, which correct the preceding ones for three-dimensional effects, it 
leads to extensive algebra and is difficult to use. However, some evaluated examples and useful tables 
can be found in Reference 10. The method of References 11 and 12, based on images in conjunction 
with Fourier transforms, is exact and easier to use, but can only be applied if either vertical or horizontal 
walls are solid. In References 13 and 14, while still depending On Fourier transforms, the wall interfer- 
ence potential is constructed in terms of infinite series, whose coefficients are found by satisfying the 
boundary conditions at a suitable number of points selected on the wind tunnel boundary. The idea of 
satisfying the boundary conditions at a discrete set of points is also the basis of the panel (lattice) 
methods. Their application to the wall interference in perforated wind tunnels is described in 
References 15-17.