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Test 4

Test 4. Momentum Drag No comprehensive exam; use time slot for test 4 5/4 @1:00pm. Example. Determine the drag coefficient of an auto at 1 atm, 70 o F, 60mph. Frontal area is 22.26 ft 2 . Force acting in flow direction is 68lbf. Road surface in wind tunnel is moving at 60mph. Example.

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Test 4

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  1. Test 4 Momentum Drag No comprehensive exam; use time slot for test 4 5/4 @1:00pm

  2. Example Determine the drag coefficient of an auto at 1 atm, 70oF, 60mph. Frontal area is 22.26 ft2. Force acting in flow direction is 68lbf. Road surface in wind tunnel is moving at 60mph.

  3. Example Redesign side-view mirrors to reduce drag. Change from disc-type to hemispheric-type. Both have characteristic diameter of 13cm. Assume auto driven 24,000km per year at average speed of 95 kmh. Assume fuel density is 0.8 kg/L; price is $0.60/L; and energy value is 44,000 kJ/kg. The engine efficiency is 30%. Find the yearly cost savings for two mirrors.

  4. Reduced drag in flows Annular water layer High molecular weight polymer additive Micro-bubble layer

  5. Open Channel Storm water Irrigation Waste water collection and treatment

  6. Types of open channel flows – • Steady flow – when discharge (Q) does not change with time. • Uniform flow – when depth of fluid does not change for a selected length or section of the channel • Uniform steady flow – when discharge does not change with time and depth remains constant for a selected section. • cross section should remain unchanged – referred to as a prismatic channel

  7. Open Channel Flow Hydraulic radius: R = A/WP Do not include free surface in wetted perimeter.

  8. Open Channel Flow Re = V R/ Laminar flow: Re < 500 Turbulent flow: Re > 2000

  9. Best Hydraulic Section Design criteria

  10. Manning Equation USCS Q = (a/n) A R2/3 So1/2 a = 1.49 SI: a = 1.0

  11. Weirs Rectangular V-notch Cipolletti

  12. Hydraulic Jump Design concern Tidal bore

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