Create a time related function
 

As we knew fluent using steady flow for all the cases. but in some cases, if we wanted to create a unsteady mass flow for the stimulation. what can we do? simply to say, let me simply the problem of inlet mass flow rate be 30sin(pi * t)+ 90. then how can we change the way of steady flow to such unsteady flow.

was it done by creating a user defined function? or something else? please help me

Re: Create a time related function
 

Hi,

I don't know your particular problem but in general it is possible to write a simple UDF code to do just that!

Melaku H.

Re: Create a time related function
 

A very closely related example (transient velocity profile) is given in section 11.1 of the FLuent 6.1 UDF manual)

Re: Create a time related function
 

OK, i try to use this . Besides, how can i change it similarly so that a UDF of preesure can be constructed?

thanks For peter

Re: Create a time related function
 

but as i think more carefully, the UDF in the section 11.1 only give a varying flow pattern along different distance. this is not the problem i wanted to solve. what i need is the way which the flow of the whole region with a mass flow rate vary with respect of time. As the way of 11.1 only provided the minimum velocity in the middle of region.

so i think this is not the same case. what can i do ???

thanks in advance

Re: Create a time related function
 

Hi Eric,

If you want to vary the inlet boundary condition with respect to time how about trying the DEFINE_PROFILE macro - something like of Example 1 in Section 4.3.13, UDF Manual with time being the variable in the function.

Declare time as a variable and then as equal to the value of a time dependent macro as in Section 6.7

good luck,

matt.