Variable Mass Flow Rates

nygrenm · November 5, 2014, 13:48

Good afternoon fellow Star CCMers!

I am having a problem. I want to have the mass flow rate at the mass flow inlet be varying...building up to a certain number. What is the best way to go about this?

lcarasik · November 5, 2014, 17:18

I believe there is a tutorial or a article on the CD-adapco Steve Portal on how to do this. I would do this by having a table that has mass flow rate at each time step and have that imported on the inlet surface of the computational domain. There is definitely a way to do this, but you might have to dig a bit to find it! Good luck!

kguntur · November 6, 2014, 02:55

Like Icarasik mentioned, you could use a table to change the mass flow rate.
You can also do this via a field function, but for that you need to know the relation between the time (or iteration) and the mass flow rate.
If it is changing arbitrarily, then table would be the way to go.

nygrenm · November 10, 2014, 14:47

Thanks guys. The mass flow is starting at 0 and increasing to a certain value. So I think the best way to go is the table perhaps then?

SB123 · November 11, 2014, 12:11

that's what i use to vary my inlet velocity. table(time) with two columns

time velocity
.00001 1 (take over after inital conditions)
1 1.5 (ramp up)
5 1.5 (end)
6 5 (ramp up)
....
etc

gotta make sure the table loads properly, if it's unsteady time i prefer to use so i can vary my timestep/inner iterations w/o recaclualating the iteration count and reloading the table.
load table in tools-> tables

i also, to make sure i'm ramping properly will monitor a report for an inlet mass flow rate, i would suggest doing the same.

nygrenm · November 11, 2014, 12:14

SB123 Thanks for the advice! I will certainly try this!!

nygrenm · November 11, 2014, 13:49

Im trying to import a .csv file into the simulation but I get an error message

"Time table profile method: No time column found in table"

SB123 · November 11, 2014, 14:17

you have to have a column titles 'time' or 'Time' i can't remember, same if you were do do an iteration table

nygrenm · November 11, 2014, 14:20

Thanks...its time.

saurabhcha1 · July 21, 2021, 13:39

Hi nygrenm, I am getting the same error message even when my column is titles as: time. Did you take any other steps to resolve the issue?

Bali · December 1, 2021, 03:36

Quote:

Originally Posted by saurabhcha1

Hi nygrenm, I am getting the same error message even when my column is titles as: time. Did you take any other steps to resolve the issue?

have you figure it out?
it is weird. seems like the software can not read "time"

Marcel95 · January 6, 2022, 05:17

Had litteraly the same problem as explained aboth. In my case the error was solved by writing the "time" in the .csv file with Big Letter "T" --> Time

November 5, 2014, 13:48	Variable Mass Flow Rates	#1
nygrenm New Member Sicher Nygren Join Date: Oct 2014 Posts: 11 Rep Power: 11	Good afternoon fellow Star CCMers! I am having a problem. I want to have the mass flow rate at the mass flow inlet be varying...building up to a certain number. What is the best way to go about this?

November 5, 2014, 17:18		#2
lcarasik Senior Member Lane Carasik Join Date: Aug 2014 Posts: 692 Rep Power: 14	I believe there is a tutorial or a article on the CD-adapco Steve Portal on how to do this. I would do this by having a table that has mass flow rate at each time step and have that imported on the inlet surface of the computational domain. There is definitely a way to do this, but you might have to dig a bit to find it! Good luck! nygrenm likes this.

November 6, 2014, 02:55		#3
kguntur Member kris Join Date: May 2014 Posts: 73 Rep Power: 11	Like Icarasik mentioned, you could use a table to change the mass flow rate. You can also do this via a field function, but for that you need to know the relation between the time (or iteration) and the mass flow rate. If it is changing arbitrarily, then table would be the way to go. nygrenm likes this.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
mass flow in is not equal to mass flow out	saii	CFX	12	March 19, 2018 05:21
Target Mass Flow Rate	Nitin	FLUENT	9	June 17, 2017 10:30
Low Mixing time Problem	Mavier	CFX	5	April 29, 2013 00:00
emag beta feature: charge density	charlotte	CFX	4	March 22, 2011 09:14
Variable mass flow at boundary	Dimitrios	FLUENT	6	November 27, 2003 02:24

November 10, 2014, 14:47		#4
nygrenm New Member Sicher Nygren Join Date: Oct 2014 Posts: 11 Rep Power: 11	Thanks guys. The mass flow is starting at 0 and increasing to a certain value. So I think the best way to go is the table perhaps then?

November 11, 2014, 12:11		#5
SB123 Member Join Date: Mar 2013 Posts: 42 Rep Power: 13	that's what i use to vary my inlet velocity. table(time) with two columns time velocity .00001 1 (take over after inital conditions) 1 1.5 (ramp up) 5 1.5 (end) 6 5 (ramp up) .... etc gotta make sure the table loads properly, if it's unsteady time i prefer to use so i can vary my timestep/inner iterations w/o recaclualating the iteration count and reloading the table. load table in tools-> tables i also, to make sure i'm ramping properly will monitor a report for an inlet mass flow rate, i would suggest doing the same.

November 11, 2014, 12:14		#6
nygrenm New Member Sicher Nygren Join Date: Oct 2014 Posts: 11 Rep Power: 11	SB123 Thanks for the advice! I will certainly try this!!

November 11, 2014, 13:49		#7
nygrenm New Member Sicher Nygren Join Date: Oct 2014 Posts: 11 Rep Power: 11	Im trying to import a .csv file into the simulation but I get an error message "Time table profile method: No time column found in table"

November 11, 2014, 14:17		#8
SB123 Member Join Date: Mar 2013 Posts: 42 Rep Power: 13	you have to have a column titles 'time' or 'Time' i can't remember, same if you were do do an iteration table

November 11, 2014, 14:20		#9
nygrenm New Member Sicher Nygren Join Date: Oct 2014 Posts: 11 Rep Power: 11	Thanks...its time.

July 21, 2021, 13:39		#10
saurabhcha1 New Member Saurabh Chavan Join Date: Jul 2021 Posts: 4 Rep Power: 4	Hi nygrenm, I am getting the same error message even when my column is titles as: time. Did you take any other steps to resolve the issue?

January 6, 2022, 05:17		#12
Marcel95 New Member Marcel Join Date: Dec 2020 Location: Germany Posts: 17 Rep Power: 5	Had litteraly the same problem as explained aboth. In my case the error was solved by writing the "time" in the .csv file with Big Letter "T" --> Time