Chapt06

# 4 read for water reynolds number is red vd q a 00111

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Unformatted text preview: ) ft]2 2 1.01 From Table 1.4 read for water Reynolds number is 10 6 m2/s 1.09 (8.17 ft/s)[( 1 /12) ft] 2 1.09 10 5 ft2/s 10 5 ft2/s. Then the pipe 31,300 This is greater than 4000; hence the flow is fully turbulent, and Eq. (6.6) applies for entrance length Le d 4.4 Re1/6 d (60 ft)/[( 1 /12) ft] 2 The actual pipe has L/d tion Le L 25 1440 (4.4)(31,300)1/6 25 1440. Hence the entrance region takes up the frac- 0.017 1.7% Ans. This is a very small percentage, so that we can reasonably treat this pipe flow as essentially fully developed. Shortness can be a virtue in duct flow if one wishes to maintain the inviscid core. For example, a “long” wind tunnel would be ridiculous, since the viscous core would invalidate the purpose of simulating free-flight conditions. A typical laboratory lowspeed wind-tunnel test section is 1 m in diameter and 5 m long, with V 30 m/s. If we take air 1.51 10 5 m2/s from Table 1.4, then Red 1.99 106 and, from Eq. (6.6), Le/d 49. The test section has L/d 5, which is much...
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## This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.

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