A test was conducted on a model of the NACA 0012 airfoil section with a solid upper surface or a porous upper surface with a cavity beneath for passive venting. The purposes of the test were to investigate the aerodynamic characteristics of an airfoil with full-chord porosity and to assess the ability of porosity to provide a multipoint or self-adaptive design. The tests were conducted in the Langley 8-Foot Transonic Pressure Tunnel over a Mach number range from 0.50 to 0.82 at chord Reynolds numbers of 2 x E+06, 4 x E+06, and 6 E+06. The angle of attack was varied from -1 degree to 6 degrees. At the lower Mach numbers, porosity leads to a dependence of the drag on the normal force. At subcritical conditions, porosity tends to flatten the pressure distribution, which reduces the suction peak near the leading edge and increases the suction over the middle of the chord. At supercritical conditions, the compression region on the porous upper surface is spread over a longer portion of the chord. In all cases, the pressure coefficient in the cavity beneath the porous surface is fairly constant with a very small increase over the rear portion. For the porous upper surface, the trailing edge pressure coefficients exhibit a creep at the lower section normal force coefficients, which suggests that the boundary layer on the rear portion of the airfoil is significantly thickening with increasing normal force coefficient.

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Effect of Full-Chord Porosity on Aerodynamic Characteristics of the NACA 0012 Airfoil

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii Dedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Table of

On the Use of Surface Porosity to Reduce Wake-Stator Interaction Noise

This paper presents novel wind tunnel test results on the aerodynamics of a symmetric thin porous
airfoil and a porous rectangular half wing using a symmetric thin airfoil as its cross section, obtained by a
six-component force balance. The variation of lift coefficient, drag coefficient, pitching moment, lift versus
drag, the gradient of lift, and location of the aerodynamic center with respect to the angle of attack are presented
as a function of the porosity. The data, where possible, are compared with the analytical results. The trend of
the experimental results behaves in the same manner as the analytical solution. The measured drag coefficients
of the airfoil and wing are also presented. The applicability of the standard equation relating the lift coefficient of a non-porous wing with that of a non-porous airfoil to the case of porous wings is verified by applying
the equation to porous wings and validating the results using experimental data. Lift slope decreases as the
porosity increases. The drag decreases at a low value of porosity and then increases as porosity increases. The
standard equation for obtaining the lift coefficient of a wing from the lift coefficient of an airfoil is applicable
and valid for porous wings and airfoils.

/pdf/aerodynamics-of-porous-airfoils-and-wings-1svb7j1ykd.pdf

Aerodynamics of porous airfoils and wings

This paper uses the large-eddy simulation framework in OpenFOAM to investigate the flow characteristics around two-dimensional partially porous airfoils with symmetrical flat geometries, which were used in a previous experiment. The effects of a porous medium near the trailing edge are investigated at a chord Reynolds number of 350,000. Two porous media are modeled to investigate how the porous medium influences the flow around the airfoil and aerodynamic performance: One is a normal porous medium, defined as a homogeneous and isotropic material with identical properties in all directions. The other medium consists of straight holes perpendicular to the airfoil surface, allowing fluid to pass through unidirectionally. It is observed that drag and lift forces vary, depending on the internal structure of the porous medium. The size of the laminar separation bubbles also varies, depending on the parameters of the porous medium, such as the internal structure, the length of the porous section, and the porosity. It is shown that an airfoil with a low-porosity unidirectional porous medium increases the lift-to-drag ratio at high angles of attack as compared with the nonporous airfoil.

Virgil M. Musat

Papers

Permeable airfoils in incompressible flow