Unformatted text preview: s. The diameter is unknown.
Correct units must of course be used. For the present example, the data should use SI units: EES rho=950 nu=2E-5 L=100 eps=6E-5 hf=8.0 g=9.81 Q=0.342 The appropriate equations are the Moody formula, the definition of Reynolds number, volume flow rate as determined from velocity, the Darcy head-loss formula, and the roughness
Re V d/nu Q V pi d^2/4 f ( 2.0 log10(epsod/3.7 hf 2.51/Re/f^0.5))^( 2) f L/d V^2/2/g epsod eps/d Hit Solve from the menu. Unlike Example 6.9, this time EES complains that the system cannot be solved and reports “logarithm of a negative number.” The reason is that we allowed
EES to assume that f could be a negative number. Bring down Variable Information from the
menu and change the limits of f so that it cannot be negative. EES agrees and iterates to the
d 0.300 V 4.84 f 0.0201 Re 72,585 The unit system is spelled out as (m, kg, s, N). As always when using software, the user should
check the solution for engineering viability. For example, is the Reynolds number turbulent?
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- Spring '08
- Fluid Dynamics, e-Text Main Menu, Osborne Reynolds