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SCHLICHTING – TRUCKENBRODT AERODYNAMICS OF THE AIRPLANE

SCHLICHTING – TRUCKENBRODT AERODYNAMICS OF THE AIRPLANE. A CRITICAL REVIEW OF CHAPTER TWO: AIRFOIL OF INIFINITE SPAN IN INCOMPRESSIBLE FLOW. 2D FLOW. THE FLOW ABOUT AN AIRFOIL OF INFINITE LENGTH IS TWO-DIMENSIONAL. INCORRECT : THE FLOW IS 3D . LIFT VS CIRCULATION.

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SCHLICHTING – TRUCKENBRODT AERODYNAMICS OF THE AIRPLANE

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  1. SCHLICHTING – TRUCKENBRODTAERODYNAMICS OF THE AIRPLANE A CRITICAL REVIEW OF CHAPTER TWO: AIRFOIL OF INIFINITE SPAN IN INCOMPRESSIBLE FLOW

  2. 2D FLOW • THE FLOW ABOUT AN AIRFOIL OF INFINITE LENGTH IS TWO-DIMENSIONAL. • INCORRECT: THE FLOW IS 3D

  3. LIFT VS CIRCULATION • LIFT PRODUCTION OF AN AIRFOIL IS CLOSELY RELATED TO THE CIRCULATION OF ITS VELOCITY IN THE NEAR-FIELD. • INCORRECT: THERE IS NO DEFINITE RELATION BETWEEN LIFT AND CIRCULATION

  4. LIFT BY CIRCULATION

  5. LOWER PRESSURE ABOVE • THERE IS HIGHER PRESSURE ON THE LOWER SURFACE, LOWER PRESSURE ON THE UPPER SURFACE. • IT FOLLOWS THEN FROM BERNOULLI THAT THE VELOCITIES ON THE LOWER AND UPPER SURFACE ARE LOWER AND HIGHER THAN THE VELOCITY OF THE INCIDENT FLOW. • TRIVIALITY: LIFT FROM PRESSURE DIFFERENCE

  6. LIFT FORMULA THE LIFT L IS GIVEN BY THE KUTTA-ZHUKOVSKY FORMULA: • L = CONSTANT x CIRCULATION • IF THE CIRCULATION IS KNOWN THE KZ FORMULA IS OF PRACTICAL VALUE FOR THE CALCULATION OF LIFT. • DANGEROUS: DOES NOT PREDICT STALL

  7. CIRCULATION DETERMINED BY SHARP TRAILING EDGE • EXPERIENCE SHOWS THAT A CIRCULATION FORMS OF THE MAGNITUDE THIS IS NECESSARY TO PLACE THE REAR STAGNATION POINT EXACTLY ON THE SHARP TRAILING EDGE. • NO THEORY: FREE SPECULATION

  8. CIRCULATION DETERMINED BY SEPARATION AT SHARP TRAILING EDGE

  9. STARTING VORTEX • BECAUSE OF FRICTION A VORTEX FORMS AT THE TRAILING EDGE WHICH QUICKLY DRIFTS AWAY FROM THE WING AND REPRESENTS THE SO-CALLED STARTING VORTEX. • SINCE THE CIRCULATION REMAINS CONSTANT FOR ALL TIMES ACCORDING TO THE THOMSON THEOREM, THERE MUST BY A CIRCULATION AROUND THE WING EQUAL TO THE STARTING VORTEX. • INCORRECT: CIRCULATION NOT CONSTANT IN TURBULENT FLOW

  10. VISCOSITY • THE VISCOSITY OF THE FLUID, AFTER ALL, CAUSES THE FORMATION OF CIRCULATION AND THEREFORE THE ESTABLISHMENT OF LIFT. • NO REASON: VISCOSITY NOT ORIGIN OF LIFT

  11. STARTING VORTEX GENERATED BY VISCOSITY

  12. SUMMARY: LIFT BY CIRCULATION • NO THEORY • NO RATIONALE • EVIDENCE BY OBSERVATION ONLY SPECULATION

  13. INCORRECT PRESSURE AT TRAILING EDGE

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