Lecture 16.pptx

# Lecture 16.pptx - Lecture 16 EXAMPLE PROBLEMAir at 1 atm...

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EXAMPLE PROBLEM- Air at 1 atm and 68 o F flowing in a long rectangular duct whose cross section is 1 ft x 0.5 ft with a velocity of 40 ft/s. The roughness of the duct is 0.00006 in. What is the pressure drop per unit length? air = 0.075 lbm/ft 3 air =0.018 cP Conversion factor cP=6.72 .10 -4 lbm/ft.s Lecture 16

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FLOW AROUND SUBMERGED OBJECTS Drag force = F = .r 2  air .V 2 /2 F/A=C d .  .V 2 /2 (C d =drag coefficient) R p = particle diameter. velocity. fluid density/fluid viscosity C d = 24/R p Stokes drag coefficient for low R p values V 2 = 4Dg( part - fluid )/3C d fluid Terminal velocity V= D 2 g( part - fluid )/18  (Stokes law) Buoyant Gravity Drag

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EXAMPLE 6.19 Estimate terminal velocity in air of a dust sphere with diameter 1 micron and SG =2. Density of air: 1.20 kg/m 3 Viscosity of air: 1.8 . 10 -5 Pa.s V= D 2 g( part - fluid )/18  (Stokes law)
A solid steel sphere of SG=7.85 and diameter 0.02 m is falling at its terminal velocity through water. What is its velocity? Make use of C d

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