FLUENT Fluent Software Trainin Ncct⊙tLD TRN-99-003 Is the flow turbulent? External flows where Re,s pUl Re25×103 along a surface L=xDD. etc Re>20000 around an obstacle Other factors such as free-stream turbulence surface conditions and Internal flows disturbances may cause earlier Ren22300 transition to turbulent flow Natural convection Ra≥103-100 where Ra≡ gBaTLp c Fluent Inc. 2/20/01D4 © Fluent Inc. 2/20/01 Fluent Software Training TRN-99-003 Is the Flow Turbulent? External Flows Internal Flows Natural Convection 5 ³5´10 Rex along a surface around an obstacle where m rUL Re where L º Other factors such as free-stream turbulence, surface conditions, and disturbances may cause earlier transition to turbulent flow. L = x, D, Dh , etc. ³ 2,300 Dh Re 8 10 Ra ³10 -10 ma b r 3 g TL Ra D º ³ 20,000 ReD