Cell size

pogbodo · February 16, 2015, 09:09

Hi all,
I am using fluent for my project and it's been very challenging as I am learning it myself with no one to guide me.

I have done my meshing using edge sizing and mapped face. I would like to know my cell size to enable me choose a good time step. Does anyone know how to get this info?

Thanks

LuckyTran · February 16, 2015, 09:17

You always need small enough cells to get spatially resolved information but if you want time-resolved simulations, then calculate your cell Courant number based on the time-step size that you want and expected cell velocity. Target Courant number ~1.

pogbodo · February 16, 2015, 12:08

Thanks LuckyTran.

I finally set up my problem and monitor. I used a UDF to define my sinusoidal velocity. However, in the monitor at the inlet I get something like this
velocity monitor.JPG

I expected a sine profile but the above profile is only correct form wt = 0 - pi.
I'm posibly doing something wrong. Could someone kindly point me to the right direction.

Thanks.

LuckyTran · February 16, 2015, 13:42

Are you specifying the profile using magnitude and direction or components. I think you should be using x,y,z components.

pogbodo · February 16, 2015, 15:28

I initially used magnitude and direction. I have now used components and hooked my udf in the inlet x component. I have also monitored the x component velocity close to the outlet and I can see a sine behaviour.

Thanks again luckyTran.

February 16, 2015, 09:09	Cell size	#1
pogbodo New Member Aberdeenshire Join Date: Feb 2015 Posts: 11 Rep Power: 11	Hi all, I am using fluent for my project and it's been very challenging as I am learning it myself with no one to guide me. I have done my meshing using edge sizing and mapped face. I would like to know my cell size to enable me choose a good time step. Does anyone know how to get this info? Thanks

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February 16, 2015, 09:17		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 65	You always need small enough cells to get spatially resolved information but if you want time-resolved simulations, then calculate your cell Courant number based on the time-step size that you want and expected cell velocity. Target Courant number ~1.

February 16, 2015, 12:08		#3
pogbodo New Member Aberdeenshire Join Date: Feb 2015 Posts: 11 Rep Power: 11	Thanks LuckyTran. I finally set up my problem and monitor. I used a UDF to define my sinusoidal velocity. However, in the monitor at the inlet I get something like this velocity monitor.JPG I expected a sine profile but the above profile is only correct form wt = 0 - pi. I'm posibly doing something wrong. Could someone kindly point me to the right direction. Thanks.

February 16, 2015, 13:42		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 65	Are you specifying the profile using magnitude and direction or components. I think you should be using x,y,z components.

February 16, 2015, 15:28		#5
pogbodo New Member Aberdeenshire Join Date: Feb 2015 Posts: 11 Rep Power: 11	I initially used magnitude and direction. I have now used components and hooked my udf in the inlet x component. I have also monitored the x component velocity close to the outlet and I can see a sine behaviour. Thanks again luckyTran.