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MAE 5130: VISCOUS FLOWS

MAE 5130: VISCOUS FLOWS. Introduction to Turbulent Flows November 23, 2010 Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk. SAMPLE STEADY TURBULENT DATA. Sampling time = 10 seconds, Sampling rate = 100 Hz

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MAE 5130: VISCOUS FLOWS

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  1. MAE 5130: VISCOUS FLOWS Introduction to Turbulent Flows November 23, 2010 Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk

  2. SAMPLE STEADY TURBULENT DATA • Sampling time = 10 seconds, Sampling rate = 100 Hz • Function f: ± 10 % fluctuation around a mean of 5 • Function g: ± 2 % fluctuation around a mean of 10

  3. STATISTICAL ANALYSIS

  4. AVERAGING POSTULATES

  5. EXPERIMENTAL DATA AND SCALED TURBULENT BOUNDARY LAYER VELOCITY PROFILES • Wall layer: Viscous shear dominates • (tlam >>> tturb) • Outer layer: Turbulent shear dominates • (tlam <<< tturb) • Overlap layer: Both types of shear important • (tlam ~tturb)

  6. TURBULENT BOUNDARY LAYER SCALING

  7. EXPERIMENTAL VERIFICATION OF INNER-, OUTER-, AND OVERLAP-LAYER LAWS RELATING VELOCITY PROFILES IN TURBULENT WALL FLOW

  8. COMMENTS ON ROUGH WALLS • IF e+ < 5 • Hydraulically smooth walls • No effect of roughness on friction • IF 5 < e+ < 70 • Transitional roughness • Moderate Reynolds-number effect • IF e+ > 70 • Fully rough flow • Sublayer is totally broken up and friction is independent of Reynolds number

  9. THE MOODY CHART

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