# Calculating mass flow rate

 Register Blogs Members List Search Today's Posts Mark Forums Read April 3, 2008, 15:13 Calculating mass flow rate #1 cfd novice Guest   Posts: n/a Hi Guys Can some one tell me please what is the relationship between mass flow rate (Ubar) and friction Reynolds number (Re tau). I need to calculate mass flow rate (Ubar) from Re tau. Thanks in advance  April 3, 2008, 18:31 Re: Calculating mass flow rate #2 cfd novice Guest   Posts: n/a Basically I am using periodic/cyclic BC at my inlet & outlet. I dont have U or P given, I have only Re tau. How can I calculte velocity from Re tau and then mass flow rate for my channel flow. Thanks in advance for answer. cfd novice  April 5, 2008, 07:58 Re: Calculating mass flow rate #3 sivaramakrishnaiah Guest   Posts: n/a you know Re number value ok ro(density)*velocity*damiter/dynamic viscosity for Re number. now you can calculate density in that density you can calculate mass flow rate know ok bye  April 5, 2008, 15:19 Re: Calculating mass flow rate #4 cfd novice Guest   Posts: n/a Hi sivaramakrishnaiah How can I calculate mass flow rate from density? Thank You  April 6, 2008, 16:12 Re: Calculating mass flow rate #5 alex Guest   Posts: n/a mass flow rate = rho*U*A (Rho=density, U=velocity, A=cross sectional area) Re = rho*U*l / mu (l=characteristic length, mu=viscosity) So Mass flow rate = Re*mu*A / l  April 7, 2008, 18:45 Re: Calculating mass flow rate #6 cfd novice Guest   Posts: n/a Thank you for your answer alex. mass flow rate = rho*U*A (1) Re = rho*U*A/mu (2) From (2): Re*mu = rho*U*A So mass flow rate = Re*mu How did you get above answer? Thanks  April 8, 2008, 13:08 Re: Calculating mass flow rate #7 alex Guest   Posts: n/a Re is based on an length, not the area. Re = rho*U*L / mu What length you use depends on the problem. L is the characteristic length. You might hear things such as Reynolds number based on pipe diameter for example. Or based on distance from leading to trailing edge of an airfoil. So... Mass flow = rho*U*A (where A=cross sectional area that the flow is flowing into). --(1) Re= rho*U*L / mu (where L is the length that you are basing your Reynolds number on) --(2) Combining (1) & (2) : Mass flow = Re*mu/L * A Regards, Alex  April 21, 2008, 06:38 Re: Calculating mass flow rate #8 davoche Guest   Posts: n/a there is a relation (from experimental datas) which can help you to determine the flow rate from re in a turbulent flow. Indeed, according to hinze (1975) : re_tau=1/8.3*(Re)^(7/8) You could also find more element (in french for the moment sorry) at the following link : http://www.olivierdoche.com/images/T...HESE_DOCHE.pdf Thread Tools Search this Thread Show Printable Version Email this Page Search this Thread: Advanced Search Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules Similar Threads Thread Thread Starter Forum Replies Last Post beguxa FLUENT 5 December 2, 2018 21:02 a.lynchy Fluent UDF and Scheme Programming 31 October 4, 2018 14:10 Sunil Gupta FLUENT 0 April 22, 2008 09:29 cfd novice FLUENT 1 April 3, 2008 18:31 Atit Koonsrisuk CFX 2 October 5, 2003 04:47

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