# Flow past a sphere

 Register Blogs Members List Search Today's Posts Mark Forums Read

 March 11, 2008, 09:08 Flow past a sphere #1 Fabio Guest   Posts: n/a Hi all, I am trying to simulate on a 3D model, a flow past a sphere which is located inside a cylinder, gap width between the sphere face and the cylinder 0.3mm (ball radius 15mm, cylinder radius 15.3mm). I got 750 PSI (it's true, is really high pressure!) pressure difference between the inlet and outlet. My goal is to predict the flow rate and the force action on the ball. As I am not interested to catch the turbulences shear stress and so on, then my mesh isn't too fine, no needs to use EWT. As you see the flow restriction is too small and the pressure is high, which yields huge flow velocities values on the shorter gap area. My point is which viscous model fits better? K-E Standard? Realizable? The solver might be Simple or Couple could be used as well? Thanks.

 November 24, 2009, 13:37 energy eqation in flow past a sphere #2 Member   Muhammed Asmail Join Date: Nov 2009 Location: Iraq Posts: 36 Rep Power: 7 Dear Sir how are you? i have problem is flow past a sphere,3-dimension,unsteady state if the energy equation is applied in flow past a sphere,how the mean value of heat tranfer calculated on surface of the sphere at each time by using FLUENT?,please can you give me the options of FLUENT in order to calculate mean value of heat tranfer calculated on the surface of sphere at each time . i am waiting your reply quickly please,please help me many thanks to you

 November 27, 2009, 15:44 #3 Senior Member   karine Join Date: Nov 2009 Posts: 158 Rep Power: 7 Hi go to solve--->monitors----> and u will find it u will choose to monitor the heattransfer over the sphere surface

November 27, 2009, 16:37
#4
Member

Muhammed Asmail
Join Date: Nov 2009
Location: Iraq
Posts: 36
Rep Power: 7
Quote:
 Originally Posted by thecfduser Hi go to solve--->monitors----> and u will find it u will choose to monitor the heattransfer over the sphere surface
Dear thecfduser

thank you very very much for your help,please Sir ,i will go to solve--->monitors and aftetr that what i will select (force,surface,volume,..or what),please give me the details step by step ,please my problem is waiting your help, for remember my problem is unsteady state,3-dimension,energy equatino,sphere
mant thanks to you

 November 27, 2009, 16:50 #5 Senior Member   karine Join Date: Nov 2009 Posts: 158 Rep Power: 7 Ok solve--->monitors--->surface choose 1 surface monitor. Enable plot, print and write in monitor 1: click on define: name: put any name ex:heat transfer coeficient report type: i dont know all report types...Look to Fluent manuel. Me i would put sum, but then u must divide ure data by the surface of ure sphere Report of: choose the variable u want to average Now Fluent will store in a file (because u enabeled write) the sum of the heat transfer coeficient over the sphere surface. U open the file with excel and divide by the sphere surface and u will got the average in function of time Hope that i could be useful sorry for my bad english if i was not clear, rewrite for me and i will try to talk in more details

 November 27, 2009, 16:51 #6 Senior Member   karine Join Date: Nov 2009 Posts: 158 Rep Power: 7 i forget something: in surfaces, u must select the sphere surface Regards

November 27, 2009, 17:10
#7
Member

Muhammed Asmail
Join Date: Nov 2009
Location: Iraq
Posts: 36
Rep Power: 7
Quote:
 Originally Posted by thecfduser i forget something: in surfaces, u must select the sphere surface Regards
dear in field report time ,what i will select (integral,flow rate,sum,...or what) i want to caculate mean value of heat transfer coefficient on the surface of the sphere at each time for example h at 10sec and h at 20sec,,etc no at each node
in x axis field what i will select (iteration,time step,flow time)
i hope that it is found example for this problem
many thanks to you

 November 27, 2009, 17:19 #8 Senior Member   karine Join Date: Nov 2009 Posts: 158 Rep Power: 7 select integral, but u will get the integral of the heat coefficient over the sphere surface ok? (in function of time) so u must divide it by the sphere surface to get the the mean value For the rest of ure quetsion, tell me before how much iteration by time step are u performing and i can respond u then. If u understand french, it will be easier to me. Regards

 November 27, 2009, 17:32 #9 Member   Muhammed Asmail Join Date: Nov 2009 Location: Iraq Posts: 36 Rep Power: 7 dear my english is best from my french i understand on your english your english is very good and no problem your text"so u must divide it by the sphere surface to get the the mean value" how can i divide? my sphere is divided before that in Gambit program my iteration in tim step is 30 as maximum value many thanks to you

 November 27, 2009, 17:40 #10 Senior Member   karine Join Date: Nov 2009 Posts: 158 Rep Power: 7 of u are interested in a whole profile, u must divide it on excel or matlab... if u choose area weighted average instead of integral, i think Fluent will divide it for u...but i am not sure....look to the fluent user's guide. 30 iteration per time step is very lot.... Anyway, in the surface monitors panel, choose WHEN TIME-STEP instead of WHEN ITERATION In X-AXIS, choose flow-time or time-step.... Fluent will plot for u your variable, and write it in a file too If u still have a problem, contact me (no need to thank me every time ) Good luck and regards comrade

November 27, 2009, 17:52
#11
Member

Muhammed Asmail
Join Date: Nov 2009
Location: Iraq
Posts: 36
Rep Power: 7
Quote:
 Originally Posted by thecfduser of u are interested in a whole profile, u must divide it on excel or matlab... if u choose area weighted average instead of integral, i think Fluent will divide it for u...but i am not sure....look to the fluent user's guide. 30 iteration per time step is very lot.... Anyway, in the surface monitors panel, choose WHEN TIME-STEP instead of WHEN ITERATION In X-AXIS, choose flow-time or time-step.... Fluent will plot for u your variable, and write it in a file too If u still have a problem, contact me (no need to thank me every time ) Good luck and regards comrade
Dear
by the way and at any time can check me what i will select area weighted average instead of integral ??? because fluent user's guide is not availble in my program.
my name is Muhammed
iraq
regards

Last edited by Muhammed_iraq; November 29, 2009 at 04:11.

November 27, 2009, 18:20
#12
Member

Muhammed Asmail
Join Date: Nov 2009
Location: Iraq
Posts: 36
Rep Power: 7
Quote:
 Originally Posted by thecfduser of u are interested in a whole profile, u must divide it on excel or matlab... if u choose area weighted average instead of integral, i think Fluent will divide it for u...but i am not sure....look to the fluent user's guide. 30 iteration per time step is very lot.... Anyway, in the surface monitors panel, choose WHEN TIME-STEP instead of WHEN ITERATION In X-AXIS, choose flow-time or time-step.... Fluent will plot for u your variable, and write it in a file too If u still have a problem, contact me (no need to thank me every time ) Good luck and regards comrade
Dear
by the way and at any time can check me what i will select area weighted average instead of integral ??? because fluent user's guide is not availble in my program.
my name is Muhammed
iraq
regards

Last edited by Muhammed_iraq; November 29, 2009 at 04:11.

 November 27, 2009, 18:41 #13 Senior Member   karine Join Date: Nov 2009 Posts: 158 Rep Power: 7 i looked in Fluent user's guide yes, choose are weighted averag and u will get what u want u can recontact me in case u still have a problem...

 November 27, 2009, 19:11 #14 Senior Member   karine Join Date: Nov 2009 Posts: 158 Rep Power: 7 hi u are using a steady or unsteady solver ?

November 29, 2009, 05:36
#15
Member

Muhammed Asmail
Join Date: Nov 2009
Location: Iraq
Posts: 36
Rep Power: 7
Quote:
 Originally Posted by thecfduser hi u are using a steady or unsteady solver ?
can you give me relation between Reynold and Nusselt? ,my Re=100,000 in order to check my solution.
i have checked cd with experimental work and the accuracy was very good
can give me example in actual work about flow past a sphere?
regards

 December 3, 2009, 14:00 #16 New Member   Matías Rodríguez C. Join Date: Dec 2009 Posts: 1 Rep Power: 0 HI Muhammed. I'm trying to solve a similar problem. I need to know the global heat transfer coefficient of a sphere (in fact, there are two shperes...one into another, separated with a air gap). The physical problema that i'm trying to solve is the drying of walnuts. But i'm starting with de simulation of the heat trasnfer. Can we maybe get email contact?. I have convergence problems with my model....how about you?. Which solver and boundary conditions are you using?. Hopingo to get an answer. Best regards Matias

December 14, 2009, 10:08
#17
Member

Muhammed Asmail
Join Date: Nov 2009
Location: Iraq
Posts: 36
Rep Power: 7
Quote:
 Originally Posted by thecfduser hi u are using a steady or unsteady solver ?
Dear Karine
can you give me relation between Reynold and Nusselt? ,my Re=100,000 in order to check my solution.
i have checked cd with experimental work and the accuracy was very good
how can i calculate the Strouhal Number(St)by using Fluent?

can give me example in actual work about flow past a sphere?
i am waiting your replr quickly

regards

December 14, 2009, 10:10
#18
Member

Muhammed Asmail
Join Date: Nov 2009
Location: Iraq
Posts: 36
Rep Power: 7
Quote:
 Originally Posted by CFDchile HI Muhammed. I'm trying to solve a similar problem. I need to know the global heat transfer coefficient of a sphere (in fact, there are two shperes...one into another, separated with a air gap). The physical problema that i'm trying to solve is the drying of walnuts. But i'm starting with de simulation of the heat trasnfer. Can we maybe get email contact?. I have convergence problems with my model....how about you?. Which solver and boundary conditions are you using?. Hopingo to get an answer. Best regards Matias
Dear Matais

please explain to me your problem step by step and send it to my e-mail(muham76@yahoo.com)
best regards

 December 14, 2009, 17:06 #19 Senior Member   karine Join Date: Nov 2009 Posts: 158 Rep Power: 7 Hi For the realtion between Re and Nu, i dont know it, but it is sure that u can find a lot of correlations in bibilography... For the Strouhal number, it is not easy... U must monitor data in a point that is behind ure sphere, then give this data to Matlab and do a fast fourrier transform to get the frequency of ure eddies....Once u have this frequency, u can calculate the Stouhal number...I dont know if this number is affected by temperature in ure case... Regards

December 15, 2009, 09:54
#20
Member

Muhammed Asmail
Join Date: Nov 2009
Location: Iraq
Posts: 36
Rep Power: 7
Quote:
 Originally Posted by thecfduser Hi For the realtion between Re and Nu, i dont know it, but it is sure that u can find a lot of correlations in bibilography... For the Strouhal number, it is not easy... U must monitor data in a point that is behind ure sphere, then give this data to Matlab and do a fast fourrier transform to get the frequency of ure eddies....Once u have this frequency, u can calculate the Stouhal number...I dont know if this number is affected by temperature in ure case... Regards
Hi

thank you very much
can give me example to caculate Strouhal number and send it to my e-mail(muham76@yahoo.com)?
best regards

 Thread Tools Display Modes Linear 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 On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post CHEN Main CFD Forum 1 January 30, 2010 03:12 Mahesh Bailakanavar FLUENT 0 February 14, 2008 01:21 lisa Main CFD Forum 2 August 30, 2005 16:36 roland schmehl Main CFD Forum 3 August 21, 2001 13:29 srijit goswami Main CFD Forum 3 January 27, 2001 08:28

All times are GMT -4. The time now is 14:46.