Doctoral Dissertations

Xiaoqing Qian

Date of Award

12-1994

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Mechanical Engineering

Major Professor

Ching F. Lo

Committee Members

R. J. Schulz, J. M. Wu, K. Kimble

Abstract

The objective of this study is to find fast and efficient ways to improve wall in-terference calculations for subsonic and transonic wind tunnel testing. The study consists of three portions. In the first portion, a panel method code, PMARC, has been modified to calculate wall interference effects using the improved test model representations. Two versions of the modified PMARC codes, MPMARC-1 and MPMARC-2, have been developed for wind tunnel wall interference study, and verified with independent reference data. In MPMARC-1, the test article is repre-sented by a mathematical model, such as source-sink, doublet and horseshoe vortex system. Excellent agreement has been found between the results of MPMARC-1 and image method for solid blockage, wake blockage and lifting system wall interferences. This modification makes it easy to study the fundamental wall in-terference mechanism. In MPMARC-2, the test article is represented by a set of numerical data which is the normal velocity distribution at the locations of tunnel wall surface panels. A case study was conducted using MPMARC-2 to simulate a wing-body geometry tested in the NASA 12ft Pressure Wind Tunnel (PWT). It's results have been verified with the original PMARC code. MPMARC-2 code reduces the computer memory requirements for complicated test article and wind tunnel geometries. With MPMARC-1 and MPMARC-2, a complete specification of test model geometry is avoided in wind tunnel wall interference computations. In the second portion of this study, a method to investigate the boundary-layer effect on wall interference prediction has been developed. The concept of equivalent boundary condition is introduced. An axisymmetric, non-lifting body with 1% tunnel blockage is selected for the study. The boundary-layer effect on tunnel wall interference prediction is proved to be negligible for subsonic wind tunnel. In the third portion of this study, a Two-Variable method for tunnel wall in-terference assessment in a circular tunnel has been developed. Analytical solutions are obtained using a Fourier transform technique, by either assuming a given body of revolution profile or representing the body of revolution by a source-sink dis-tribution. Numerical examples computed by a transonic small perturbation code TSFOIL and a panel method code PMARC are utilized to validate the developed Two-Variable method for open jet and closed circular tunnels, respectively. Good agreement has been found between the interference pressure coefficients obtained with the Two-Variable method and the numerical code predictions. Results have demonstrated that the Two-Variable method for circular tunnel blockage wall in-terference is ready for experimental verification. The general results of this overall studies are the development of fast and practical ways to evaluate wind tunnel wall interference effects on complex test articles in arbitrary configurations of tunnel test sections.

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