Numerical Analysis of Wind Tunnel Wall Interference on Two-dimensional Airfoil by New Porous Wall Model

Abstract

To analyze wall interference of a transonic wind tunnel, flows of two-dimensional airfoil with wind tunnel porous walls are computed by CFD and the new porous wall model. First, the computational results are validated by comparing with measurement. The porous wall model shows high accuracy enough to precisely simulate the wall interference. Effect of the wall interference is discussed by comparing two kinds of computational results with and without the wind tunnel wall. Wall interference by the porous wall is characterized by the downwash and blockage. Porous wall is effective for decreasing the blockage, which causes the acceleration around the airfoil. However, high porosity of the porous wall causes the large downwash, and it changes incidence angle of the airfoil. The Mokry's correction method for wall interference is verified by applying the correction to CFD results. The Mokry's method shows high accuracy in subsonic and no stall conditions, which meet the requirement of small perturbation potential equation. The accuracy is also high even if the model is large relative to the wind tunnel size. However, about 10 drag count error is caused under the transonic flow. The accuracy is rapidly reduced around the stall condition, and over 100 count error is caused. Nomenclature= coordinate = velocity of x,y direction = flow angle ( ( )) [deg] = lift coefficient = drag coefficient = height of wind tunnel = chord length of airfoil = airfoil thickness = porosity (ration of hole to wall area) = angle of attack

Numerical Analysis of the ONERA-M6 Wing with Wind Tunnel Wall Interference

“…An advantage of the present method is that the interference quantity on the wing chord can be specified where there is no CFD solution. Although previous research showed that the wall interference quantity computed by the linearized potential equation has some error in transonic flow cases, 7) its accuracy is sufficient for the present qualitative discussion. In the present study, Eqs.…”

“…In our previous study, we investigated how to change the flow field of a two-dimensional airfoil by wall interference and showed the wall interference reduced the Mach number and flow angle. 7) Also in the present study, the interference values for the Mach number and flow angle are computed, and we investigate the wall interference effect in the three-dimensional flow field. Then, in order to understand the wall interference in more detail, the effect on the lambda shock and aerodynamics coefficients are discussed in terms of the interference values of Mach number and flow angle.…”