[3nhu1]

Hi I am trying to write a nested IF statement as an expression in CFX.
Particularly I am getting errors as I would like to include the && (AND) portion - sorry I have already read the reference guide section on expressions
This is the equation that I would wish to include, thank you.

Thank you.

T_vc = 0.34[s]
T_vr = 0.15[s]
T = 1[s]

[ghorrocks]

if(t<=T_vc,[Top function],if(t<=T_vc+T_vr,[Middle function],if(y<=T,0[units?],[undefined!])))

Easy.

[3nhu1]

Thank you! This was a massive help and I am really very grateful.

if(t<=tvc,0.5 - 0.5*cos(pi*t/tvc),if(t<=tvc+tvr,0.5 + 0.5*cos(pi*(t-tvc)/tvr),if(t<=te,0[ ] ,0)))

I realised that this needs to be periodic e.g. 5s, could I ask how would a mod function be initialised?

[ghorrocks]

t_cycle = mod(t,5[s]))

Then change the equation to check t_cycle rather than t.

Also note your last nested if() statement is not required, both cases evaluate to 0 so you might as well remove it.

[3nhu1]

Thank you, sorry a last question I hope!

I tried using the above and also this simple example for another post

Cycletime = mod(t,11[s])
HeaterPower = if(Cycletime<1[s],100[W],0[W])

When I go to the variable in expressions either Cycletime and HeaterPower and plot for t > 1s e.g. 4s would I see the period function repeated in the plot?
I don't seem to obtain that.

[ghorrocks]

Please post what you do obtain then. Make sure you have enough resolution in the plot to resolve the transients - 0.1[s] resolution would be suitable.

[3nhu1]

Actually I managed to find out what was going on, you were right and had to zoom out to see it was repeating every 5 seconds instead, so I needed to set the time period to 1sec!

mod(t,1[s])

This works a treat and was really a massive help, so sincerely my thanks