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Experimental investigation of the design and testing capabilities of the tolerant wind tunnel

University of British Columbia

This thesis deals with a new approach to reduce wall blockage effects in wind tunnel testing. The idea is to use test section walls with airfoil slats at zero incidence to provide a test environment close to the free air condition. The performance of this test sec tion was investigated experimentally for forced plunging oscillation of two-dimensional NACA 0015 airfoils. A potential flow theory was also developed to estimate the wall correction numerically. Though a substantial difference between theory and experiment was observed under all cOnditions, both results show a similar trend: the wall blockage effect increases with increasing C/H ratio, but decreases with increasing non-dimensional frequency μ. However, low-correction experimental data is achieved at an open area ratio about 70%. This research was next extended to wind engineering tests of bluff bodies. The new wind tunnel test section consists of a sequence of uniformly spaced ring airfoils and a solid floor which represents the ground. Current test models include truck-trailer combinations, buses, cars and buildings. Spires and roughness elements are employed to simulate the atmospheric boundary layer flow in the building tests. The effects on wall corrections of several parameters,, such as the tunnel open area ratio, model area blockage ratio, model length blockage ratio, tunnel test section length-width ratio and the natural wind profile were investigated and relations between them were discussed. For the airfoil-slatted test section, results show that even at a model area blockage of 30% and length blockage of 50%, pressure distributions and drag coefficients unaffected by the tunnel walls can be obtained at an optimum combination of these parameters. Moreover, a common model blockage tolerance range is observed for all test models over the middle range of the open area ratio. On the whole, a test section with a length-width ratio of 5.0 at an open area ratio of 48% tends to be the best choice for wind engineering tests in the 3-D tolerant wind tunnel.

Thesis/Dissertation

application/pdf

2009-06-04

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http://hdl.handle.net/2429/8800

Mechanical Engineering

University of British Columbia

UBCV

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