Experimental Study of the Effects of Finite Surface Disturbances and Angle of Attack on the Laminar Boundary Layer of an NACA 64A010 Airfoil with Area Suction.

摘要

A Langley low-turbulence wind-tunnel investigation was made of an NACA 64A0l0 airfoil section with continuous suction (area suction) through its porous surfaces to determine its ability to maintain extensive laminar flow behind finite surface disturbances and at angles of attack other than 0 deg. Although full-chord laminar flow can be obtained at large values of the Reynolds number through the use of area suction, application of area suction permitted only a small increase in the size of a finite disturbance required to cause premature boundary-layer transition as compared with the nonsuction airfoil. The results indicated that the stability theory for the incompressible laminar boundary layer, which is derived for vanishingly small, two-dimensional, aerodynamically possible disturbances in the boundary layer, is of little practical significance in determining the sensitivity of the laminar boundary layer to surface projections. Combined wake and suction-drag coefficients lower than the drag coefficient of the plain airfoil were obtained through a range of low lift coefficient by the use of area suction.