[warmboy24]

Hi everyone! I am using CFX-Pre to simulated heat transfer in plastic injection molds. I simulate water flow in a cycle with the Expression function in CFX-Pre as follows:



Now, I want to want to simulate water flow in cycles but I can not. I do not know how.

Anyone can help me?! please!! thank you very much!

[ghorrocks]

The expressions Temp30 and Temp80 are completely unnecessary. You just need a single simple function:

Tinlet = if(t>20[s],30[C],80[C])

This should return the same value as your function does (except at t=20[s]).

What do you mean by a cycle? The function you describe is just a change in inlet from 30C to 80C.

[warmboy24]

Originally Posted by ghorrocks

The expressions Temp30 and Temp80 are completely unnecessary. You just need a single simple function:

Tinlet = if(t>20[s],30[C],80[C])

This should return the same value as your function does (except at t=20[s]).

What do you mean by a cycle? The function you describe is just a change in inlet from 30C to 80C.

Thank you!
My cycle is 40 seconds, in the first twenty seconds the temperature is 80 ° C, in the next twenty seconds the temperature is 30oC. I now want to change the temperature in several consecutive cycles. For example, in two cycles, from 1s to 20s temperature is 80oC, from 20s to 40s temperature is 30oC, from 40s to 60s returned to 80oC temperature, from 60s to 80s temperature is 30oC.

Now I want to simulate many cycles (eg 100 cycles), but I do not know how. Can I change the settings in CFX-Pre to do that? or I have to create an Expression to do it?

[ghorrocks]

Easy:

CyclePosition = mod(t,40[s])
Tinlet = if(CyclePosition<20[s],80[C],30[C])

[warmboy24]

Originally Posted by ghorrocks

Easy:

CyclePosition = mod(t,40[s])
Tinlet = if(CyclePosition<20[s],80[C],30[C])

Its Working! Thank You very much!

[warmboy24]

Originally Posted by ghorrocks

Easy:

CyclePosition = mod(t,40[s])
Tinlet = if(CyclePosition<20[s],80[C],30[C])

Hello Ghorrocks! Can you help me again?!


I'm making a simulated blow hot air on the surface of an object, as shown below.



Now, I want to control airflow over time and in multiple cycles. in one cycle (40 s): in the first 5 seconds of hot air is blown into; in the next 35 seconds not blow.

For example, I simulated in two consecutive cycles. from 0s to 5s air is blown into; from 5s to 40s not blow; from 40s to 45s air is blown into; from 45s to 80s not blow.

Can I control it by Experssion? and how do I do that?

Thanks!

[mvoss]

use the if()-statement to control the temperature. since it´s not directly related to the massflow you can simply turn it on and off when there is no flow.
If there are not to many cycles... create an expression for every "peak" with the return values being "0" otherwise and in the end add up all the peakes like T_inlet=T1+T2+T3+T4... and use T_inlet @ inlet

[warmboy24]

Originally Posted by mvoss

use the if()-statement to control the temperature. since it´s not directly related to the massflow you can simply turn it on and off when there is no flow.
If there are not to many cycles... create an expression for every "peak" with the return values being "0" otherwise and in the end add up all the peakes like T_inlet=T1+T2+T3+T4... and use T_inlet @ inlet

I used this Expressions to controll massflow and It ran look well. But Im not really sure. What do you think about that?!



In 20s cycle.

[ghorrocks]

Your function is fine. It turns the flow on for 5s and off for 15s, and repeats this forever. I do not know why you would bother with lots of if statements when the function you have is simple, nice and will continue if you decide you need to run for more cycles.