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Analytical Study of Ventilated Wind Tunnel Boundary Interference on V/STOL Models Including Wake Curvature and Decay Effects

Report Number: AEDC TR 74-51
Author: Kraft, E. M.
Corporate Author: ARO, Inc.
Laboratory: Propulsion Wind Tunnel Facility
Date of Publication: 1974-11
Pages: 59
Contract: None Given
Contract: `
Project: None Given
AD Number: ADA000922

The wind tunnel boundary interference on a V/STOL model is calculated in a rectangular test section with solid vertical walls and ventilated (perforated or slotted) horizontal walls. The interference is found by applying the small perturbation theory of an incompressible fluid to the boundary value problem. The theory uses an image method in addition to Fourier transforms with an equivalent homogeneous boundary condition on the ventilated wall. The mathematical representation of the V/STOL model accounts for the curvature and decay of the wake. The assumption of a constant wake strength produces a paradox in that the maximum value of the interference factors increases as the initial jet velocity decreases. It is indicated that a realistic representation of the wake decay may be as significant as the wake curvature in assessing interference on pitching moment, tail forces, or blockage effects. The most significant aspect of the analysis shows that nonlinear cross-flow effects at the tunnel boundary are important in the V/STOL case, and a quasi-linear approximation to these effects is introduced into the solution providing good agreement with experimental data.

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