Numerical Analysis of Flow through a Hole for Modeling of Wind Tunnel Porous Wall

Abstract

To model porous walls used in transonic wind tunnels, flow through a hole is investigated using Computational Fluid Dynamics (CFD). First, we analyze the relation between flow rate and differential pressure across the hole. At low differential pressures, such as for wind tunnel porous walls, the flow rate is found to increase linearly with differential pressure. We therefore propose a new model based on a linear relationship between flow rate and differential pressure. The effects of hole shape and boundary layer conditions near the hole are then investigated. In the outflow case (i.e., wind tunnel to plenum chamber), the flow rate increases as the ratio of hole depth to diameter becomes large due to variation of the flow separation area at the hole exit. Boundary layer thickness also affects the flow field: when the ratio of boundary layer thickness to hole diameter becomes small, the flow rate decreases, because the flow along wind tunnel side wall interacts more strongly with the flow through the hole.

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

“…The permeable walls greatly affect the flow field, and hence they must be properly modeled. However, there was no reliable model for the porous wall which is suitable for the condition of transonic wind tunnel, and therefore authors created a new porous wall model 9,10 . Using this new model, the pressure distributions on the porous wall agree well with the measurements.…”

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

“…The porous wall is modeled by the relationship between flow rate and differential pressure through the wall. Details of the modeling method can be found in Nambu et al 5,6) In this study, the porous wall is modeled by the following equations:…”

“…We have therefore developed a new porous wall model for transonic wind tunnels by analyzing the flow through a single hole using computational and experimental approaches. 5,6) This is the first model that can compute the effect of porous walls without requiring any empirical parameters. In our previous study, we attempted to apply the new model to compute the flow around a two-dimensional airfoil with wind tunnel walls.…”