Transient heat flux changing in spatial coortinate

shahpar73 · September 2, 2016, 09:29

I want to apply HeatFlux [W/m^2] on a boundary between t=0s & 1s with x,y,z=0,0,0. The same heat flux is needed to apply between t=1s & 2s with x,y,z=1,0,0.

How to set STEP function for it in CEL?

ghorrocks · September 2, 2016, 09:46

For your first point, try:

if(t<1[s],100[W/m^2],0[W/m^2])

As the heat flux on the boundary.

I do not understand your comment about x,y,z=0,0,0 or 1,0,0.

shahpar73 · September 2, 2016, 15:33

Please read my rephrased question bellow....

I am trying to run a transient analysis for 2s. I want to apply HeatFlux [W/m^2] on a boundary between t=0s & 1s with x=0 mm. The same heat flux is needed to apply between t=1s & 2s with x=1mm. Note that x is the x-axis in cartesian coordinate system.

How to set STEP function for it in CEL?

The analysis is aimed to simulate moving heat source with increment of 1mm in the x-direction.

ghorrocks · September 3, 2016, 08:59

The if function is easier to understand compared to step.

Try these functions:
StartX = if(t<1[s],0[mm],1[mm])
EndX = if(t<1[s],1[mm],2[mm])
HeatFlux = if(x>StartX,if(x<EndX,100[W/m^2],0[W/m^2]),0[W/m^2])

And then use the HeatFlux variable as the function for the boundary heat flux.

shahpar73 · September 4, 2016, 15:52

Dear Glenn
I really appreciate your help...
Can you please modify the above CEL expressions to apply HeatFlux of 100 [W/m^2] at x=0mm when time t=0s-to-1s, then at x=1mm when t=1s-to-2s, and then at x=2mm when t=2s-to-3s.

I tried defining (in red colour);

StartX1 = if(t<1[s],0[mm],1[mm])
StartX2 = if(t<2[s],1[mm],2[mm])

EndX1 = if(t<1[s],1[mm],2[mm])
EndX2 = if(t<2[s],2[mm],3[mm])

And then tried to add to the HeatFlux equation (given above in your reply), but failed to get the required results.

ghorrocks · September 4, 2016, 19:56

You can see how these nested if statements get pretty ugly when it gets more complex.

Things you can do to simplify in include using a 1D interpolation function.

Hopefully you get the idea of if statements now and I do not have to write them for you. But if it is still not working please post the statement you are using and any error message it gives.

September 2, 2016, 09:29	Transient heat flux changing in spatial coortinate	#1
shahpar73 Member Shahid Parvez Join Date: Jul 2009 Location: Pakistan Posts: 38 Rep Power: 17	I want to apply HeatFlux [W/m^2] on a boundary between t=0s & 1s with x,y,z=0,0,0. The same heat flux is needed to apply between t=1s & 2s with x,y,z=1,0,0. How to set STEP function for it in CEL?

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September 2, 2016, 09:46		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	For your first point, try: if(t<1[s],100[W/m^2],0[W/m^2]) As the heat flux on the boundary. I do not understand your comment about x,y,z=0,0,0 or 1,0,0.

September 2, 2016, 15:33		#3
shahpar73 Member Shahid Parvez Join Date: Jul 2009 Location: Pakistan Posts: 38 Rep Power: 17	Please read my rephrased question bellow.... I am trying to run a transient analysis for 2s. I want to apply HeatFlux [W/m^2] on a boundary between t=0s & 1s with x=0 mm. The same heat flux is needed to apply between t=1s & 2s with x=1mm. Note that x is the x-axis in cartesian coordinate system. How to set STEP function for it in CEL? The analysis is aimed to simulate moving heat source with increment of 1mm in the x-direction.

September 3, 2016, 08:59		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	The if function is easier to understand compared to step. Try these functions: StartX = if(t<1[s],0[mm],1[mm]) EndX = if(t<1[s],1[mm],2[mm]) HeatFlux = if(x>StartX,if(x<EndX,100[W/m^2],0[W/m^2]),0[W/m^2]) And then use the HeatFlux variable as the function for the boundary heat flux.

September 4, 2016, 15:52		#5
shahpar73 Member Shahid Parvez Join Date: Jul 2009 Location: Pakistan Posts: 38 Rep Power: 17	Dear Glenn I really appreciate your help... Can you please modify the above CEL expressions to apply HeatFlux of 100 [W/m^2] at x=0mm when time t=0s-to-1s, then at x=1mm when t=1s-to-2s, and then at x=2mm when t=2s-to-3s. I tried defining (in red colour); StartX1 = if(t<1[s],0[mm],1[mm]) StartX2 = if(t<2[s],1[mm],2[mm]) EndX1 = if(t<1[s],1[mm],2[mm]) EndX2 = if(t<2[s],2[mm],3[mm]) And then tried to add to the HeatFlux equation (given above in your reply), but failed to get the required results.

September 4, 2016, 19:56		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	You can see how these nested if statements get pretty ugly when it gets more complex. Things you can do to simplify in include using a 1D interpolation function. Hopefully you get the idea of if statements now and I do not have to write them for you. But if it is still not working please post the statement you are using and any error message it gives.