Axial velocity problem in Fluent

clueless · May 15, 2009, 03:54

Near the inlet of the pipe, the axial velocity of a 500 reynold number flow is lower than that of a flow at reynold number 100. May i enquire why?

ak6g08 · May 15, 2009, 15:06

hi,

could you clarify something for me, the Re=500 is at the inlet of the pipe..where are you getting an Re=100?

in general, a reynolds number can be lower for a lower flow velocity, assuming the characteristic length is larger...so in the atmosphere (outside of the inlet), your reynolds number is much larger because your 'characteristic length' is huge, when you then move into say a pipe, your length (pipe diameter) suddenly decreases substantially, and thus results to a lower reynolds number even though your velocity goes up, but if you are comparing the inlet of a given pipe to the outlet of the same pipe, the reynolds numbers must be the same throughout, due to mass continuity...hope that helps

akour

May 15, 2009, 03:54	Axial velocity problem in Fluent	#1
clueless New Member - Join Date: May 2009 Posts: 4 Rep Power: 18	Near the inlet of the pipe, the axial velocity of a 500 reynold number flow is lower than that of a flow at reynold number 100. May i enquire why?

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May 15, 2009, 15:06		#2
ak6g08 Member Akour Join Date: May 2009 Posts: 79 Rep Power: 18	hi, could you clarify something for me, the Re=500 is at the inlet of the pipe..where are you getting an Re=100? in general, a reynolds number can be lower for a lower flow velocity, assuming the characteristic length is larger...so in the atmosphere (outside of the inlet), your reynolds number is much larger because your 'characteristic length' is huge, when you then move into say a pipe, your length (pipe diameter) suddenly decreases substantially, and thus results to a lower reynolds number even though your velocity goes up, but if you are comparing the inlet of a given pipe to the outlet of the same pipe, the reynolds numbers must be the same throughout, due to mass continuity...hope that helps akour