Biplane Effect

Because WindLode suspends the blades at intervals within an annular framework, the biplane effect is due consideration. The biplane effect is the phenomenon of reduced lift at the lower wing of a biplane, a result of the interference of the upper wing on the aerodynamics of the lower wing. The biplane effect was studied during the biplane era and is attributed to the compressive effect of the upper wing on the airflow over the lift surface of the lower wing. The effect is shown to vary according to the vertical distance between the upper and lower wings; the closer the two wings, the greater the effect and the further apart the wings, the less the effect. The biplane effect is diminished by stagger, wherein the leading edge of one of the two wings is advanced ahead of the other, the more the stagger, the less the biplane effect. In a typical biplane, the lower wing is placed at a distance of one chord below the upper, and the upper wing is staggered ahead of the lower wing. This combination of stagger and one chord separation of the two wings achieves a lift capacity for the lower wing rated at about 85% of the lift capacity of an identical wing on a monoplane.

Blades installed within the annular framework of WindLode should be considered subject to a biplane effect, assuming that the preceding blade interferes with the aerodynamics of the following blade. However, this potential problem is addressed by the proper spacing of blades within the framework. In the scaling/rating exercise, blades are spaced one and one-half chords apart. Also, there is a degree of stagger between adjacent blades, induced by the curvature of the framework. If a biplane effect is to be applied, it will be as a factor in the determination of the Coefficient of Lift of the inventive single-camber blade. In the Scaling/Rating Exercise, no biplane effect is applied. 

Betz’s Limit

Betz’s Limit holds no meaning for lift-powered wind turbines despite the current practice within the wind power industry, as such practice simply reflects aerodynamic backwardness. Betz’s Limit was formulated by Albert Betz in 1920, before understanding of lift was actually achieved. Betz utterly misapprehended the aerodynamics of lift, and therefore the formulation of his 1920 paper is meaningless, respecting lift-powered wind turbines. The prevailing adherence to Betz’s Limit signifies that wind turbine designers, most astonishingly, have little acquaintance with the aerodynamics of lift.

[Review of Betz’s Limit]

Aerodynamics of Lift

Lift is a force, that force being a pressure differential across an airfoil, which pressure differential is generated by airflow relative to the airfoil, which airflow generates a high pressure field at one side of the airfoil and at its leading edge, and a low pressure field at the camber on the opposite side, which airflow is generated by the forward motion of an airfoil, as the wing of an airplane, or, as in the case of an airfoil turbine blade, the airflow is the resultant of wind and forward motion of the rotating airfoil blade.