ENGG 2230 Chapter : FluidMechWhite5eCh06.pdf
9 Apr 2013
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In flow past a sphere, the boundary layer becomes turbulent at about red 2. 5e5. Solution: for air at 20 c, take = 1. 2 kg/m3 and = 1. 8e 5 kg/m s. Convert d = 1. 6 inches to 0. 0406 m. the critical reynolds number is. Since air density and viscosity change with pressure, temperature, and humidity, the calculation does indeed depend upon the thermodynamic state of the air. 6. 2 air at approximately 1 atm flows through a horizontal 4-cm-diameter pipe. (a) find a formula for qmax, the maximum volume flow for which the flow remains laminar, and plot. Solution: (a) first convert the reynolds number from a velocity form to a volume flow form: With d = 0. 04 m = constant, get and for air from table a-2 and plot qmax versus t c: The curve is not quite linear because = / is not quite linear with t for air in this range.
