Читать книгу Wind Energy Handbook - Michael Barton Graham - Страница 132

If the angle of attack exceeds a certain critical value (typically 10° to 16°, depending on the Re), separation of the boundary layer on the ‘suction’ (or upper) surface takes place. A wake forms above the aerofoil starting from this separation (Figure A3.12), and the circulation and hence the lift are reduced and the drag increased. The flow past the aerofoil has then stalled. A flat plate at an angle of attack will also behave like an aerofoil and develop circulation and lift but will stall at a very low angle of attack because of the sharp leading edge. Cambering (or curving) the plate will increase the angle of attack for stall onset, but a much greater improvement can be obtained by giving thickness to the aerofoil together with a suitably rounded leading edge.