MODERN AERODYNAMICS AS PSEUDO-SCIENCE
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MODERN AERODYNAMICS AS PSEUDO-SCIENCE
CLAES JOHNSON
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PSEUDO-SCIENCE
• SUBSTANTIAL EFFECT FROM
• UNKNOWN CAUSE OR• CAUSE TOO SMALL FOR
• EXPERIMENTAL VERIFICATION
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EXAMPLES OF PSEUDO-SCIENCE
• ASTROLOGY• CROP CIRCLES• LYSENKOISM• PARAPSYCHOLOGY• UFOLOGY• PSYCHOKINESIS• LEVITATION
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PSEUDO-SCIENCE
• PSYCHO-ANALYSIS: UNCONSCIOUS SELF• MARXISM: SOCIALISM INEVITABLE + GOOD
BECAUSE CAPITALISM IS UNSTABLE
• BASIC ASSUMPTIONS CANNOT BE TESTED• PREDICTIONS CANNOT BE TESTED • EXPERIMENTALLY OR THEORETICALLY
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PSEUDO-SCIENCE??
• STRING THEORY: TOO SMALL SCALES• STATISTICAL MECHANICS: MOLECULAR CHAOS
• BASIC ASSUMPTIONS CANNOT BE TESTED• PREDICTIONS CAN/CANNOT BE TESTED
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KUTTA + ZHUKOVSKY + PRANDTL 1904FATHERS OF MODERN AERODYNAMICS
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PROVED THAT FLYING IS POSSIBLE AFTER WRIGHT SHOWED IT IN 1903
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MODERN AERODYNAMICS: LIFT + DRAG
• KUTTA-ZHUKOVSKY:• LIFT FROM CIRCULATION FROM• SHARP TRAILING EDGE SINGULARITY
• PRANDTL:• DRAG FROM • VANISHINGLY THIN BOUNDARY LAYER
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UNKNOWN OR SMALL CAUSE: TESTING IMPOSSIBLE
• LIFT:• SHARP TRAILING EDGE SINGULARITY
• DRAG: • VANISHINGLY THIN BOUNDARY LAYER
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EFFECT OF KUTTA-ZHUKOVSKY
• UIUC AIRFOIL DATABASE: 1500 AIRFOILS• ALL WITH SHARP TRAILING EDGE
• REAL WING: ROUNDED OR BLUNT • 1% - 10% CHORD LENGTH
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ROUNDED TRAILING EDGE: REAL TURBIN BLADE
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EFFECT OF PRANDTL
• AERODYNAMICS UNCOMPUTABLE
• AERODYNAMICS MYSTERY
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LUDWIG PRANDTL: BIG EFFECT FROM SMALL FRICTION
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PRANDTL BOUNDARY LAYER 1904
A very satisfactory explanation of the physical process in the boundary layer [Grenz-schicht] between a fluid and a solid body could be obtained by the hypothesis of an adhesion of the fluid to the walls, that is, by the hypothesis of a zero relative velocity between fluid and wall.
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SMALL FRICTION – BIG EFFECT
If the viscosity was very small and the fluid path along the wall not too long, the fluid velocity ought to resume its normal value at a very short distance from the wall. In the thin transition layer, however, the sharp changes of velocity, even with small coefficient of friction, produce marked results.
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EFFECT FROM EVER-SO-SMALL VISC.
In the steady motion around a sphere, there is a transition from the motion with viscosity to the limit of non-viscosity, then something quite different from the Dirichlet motion is produced. The latter is then only an initial condition, which is soon disturbed by the effect of an ever-so-small viscosity.
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SUCCESS CLAIMED
This plan has proved to be very fruitful, in that, on the one hand, it produces mathematical formulas, which enable a solution of the problems and, on the other hand, the agreement with observations promises to be very satisfactory.
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KUTTA-ZHUKOVSKY: BIG EFFECT FROM UNKNOWN CAUSE
• IF THERE IS CIRCULATION THEN THERE IS LIFT
INCORRECT LOGIC:• LIFT IS OBSERVED• HENCE THERE MUST BE CIRCULATION• BUT FROM WHERE?
NO ANSWER. HENCE IT MUST BE: • TRAILING EDGE SINGULARITY + VISCOSITY
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KUETHE-SCHETZER: TEXT BOOK: FOUNDATIONS OF AERODYNAMICS:
• A body with a sharp trailing edge which is moving through a fluid will create about itself a circulation of sufficient strength to hold the rear stagnation point at the trailing edge.
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SCHLICHTING: STUDENT OF PRANDTL:
• The technically most important wing profiles have, in general, a more or less sharp trailing edge.
• Then the magnitude of circulation can be derived from experience, namely, that there is no flow around the trailing edge, but that the fluid flows off the trailing edge smoothly.
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DANGER OF SUCCESS AND FATHERHOOD
• KZP PARALYZED MODERN AERODYNAMICS INTO PSEUDO-SCIENCE