# Create a time related function

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 February 28, 2005, 09:51 Create a time related function #1 Eric Guest   Posts: n/a 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

 March 2, 2005, 06:06 Re: Create a time related function #2 Melaku H. Guest   Posts: n/a 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.

 March 3, 2005, 09:03 Re: Create a time related function #3 peter Guest   Posts: n/a A very closely related example (transient velocity profile) is given in section 11.1 of the FLuent 6.1 UDF manual)

 March 3, 2005, 13:30 Re: Create a time related function #4 Eric Guest   Posts: n/a 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

 March 4, 2005, 11:58 Re: Create a time related function #5 Eric Guest   Posts: n/a 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

 March 14, 2005, 15:53 Re: Create a time related function #6 matt Guest   Posts: n/a 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.

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