How to set up transient BC?
 

Hi,

I've a problem setting up the transient BC.

What I wish to get is:

1-2 sec, function1(t)

2-4 sec, function2(t)

4-6 sec, function1(t)

6-8 sec, function2(t)

......

Anyone know how to implement this expression in CFX-Pre?

Thanks, Sam

Re: How to set up transient BC?
 

Hi Sam,

Create expressions for each of your functions:function1 = ...
function2 = ...
...Then create an expression that includes all the functions and multiplies each by a corresponding step function:allFunctions = function1*step((2 [s]-t)/1[s]) +
function2*step((t-2 [s])/1[s])*step((4 [s]-t)/1[s]) +
function3*step((t-4 [s])/1[s])*step((6 [s]-t)/1[s]) +
function2*step((t-6 [s])/1[s])*step((8 [s]-t)/1[s]) +
...A step function takes a dimensionless argument (hence dividing by 1 [s]). If the argument is negative, it returns zero, positive returns 1 and if it is equal to zero, it returns 1/2. By combining your functions this way, you can turn them on and off as needed.

Regards,
Robin

Thank you.
 

Thanks, robin.

It works eventhough it's lengthy. I've to simulate over 40 sec & allfunction becomes a giant equation.