Computation of transonic viscous flow over airfoils with control by an elastic membrane and comparison with control by passive ventilation

Breitling, Thomas; Zierep, Jürgen

doi:10.1007/bf01177169

Cited by 3 publications

(1 citation statement)

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“…The use of passive porous walls for drag control in transonic ow has also been studied experimentally by Nagamatsu et al 14 and Breitling and Zierep. 15 Similarly, ventilated porous walls have long been used to reduce blockage effects in transonic tunnels (for example, see the recent paper by Beutner et al 16 ). In this case the passive porous walls were effective at reducing shock strength and, thereby, wave drag.…”

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confidence: 98%

Effects of Passive Porous Walls on Boundary-Layer Instability

Carpenter

Porter

2001

AIAA Journal

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A theoretical study is described of the effects of a passive porous wall on boundary-layer instability. The passive porous wall is conceived of as a thin porous sheet stretched over a plenum chamber. When disturbances in the form of Tollmien-Schlichting waves propagate along the boundary layer, the uctuating pressure forces air in and out of the plenum chamber. The basic approach is based on classic linear stability theory for the at-plate boundary layer with modi ed wall boundary conditions. The wall response is represented by a complex admittance (ratio of uctuating ow rate per unit area to wall pressure) and, therefore, applies to a general class of passive porous, and other interactive, walls. The effects of a wide range of admittance values are studied. A stabilizing effect is obtained when the admittance phase is close to ¼/2, and an optimum value of admittance magnitude is also found. A theoretical model is introduced and used to calculate the admittance of the porous panels used in a parallel experimental study. It is shown that it may be possible to manufacture stabilizing porous panels. The stabilizing mechanism is due to the production of a near-wall region of negative Reynolds stress. Nomenclatureboundary-layer displacement thickness = dimensionless disturbance vorticitý = dimensionless compliant wall displacement ¹ = dynamic viscosity º = kinematic viscosity ½ = density ¾ = wall porosity, that is, proportion of area occupied by pores ' = admittance phase ! = dimensionless disturbance frequency Subscripts c = quantities evaluated in the plenum chamber i = imaginary part r = real part w = quantities evaluated at the wall ¾ D 1 = quantities evaluated with ¾ D 1 Superscripts O = disturbance amplitude N = average over a disturbance cycle

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confidence: 98%