## Fluids

#### integration operation in cfd post

• Noushin
Subscriber
Dear experts
In many of the parameters related to hemodynamics we find the application of integration such as
TAWP=1/T * Int (Pressure with respect to t)

How can I integrate any parameter in cfd post? Can anyone help?

Thank you
• Rob
Ansys Employee

I assume you mean t as in time and not Temperature ( t and T may be used for both or either). The data files retain data for each time step. You'll need to extract data for a point(s) of pressure v time and then integrate that curve numerically. If you're running the calculation then a UDF/expression could be used at each time step.

• Noushin
Subscriber
Thank you for your response. Yes time is denoted by t here. What would be the expression? Because in the expression window there is an operation "int", I thought that can be used as integrator. But how do I introduce the limits there? or does the expression automatically takes time period as limit? Because in case of integration with respect to two terms how can I define the integrator? such as integration with respect to helicity

Thank you

Regards
Noushin
• Rob
Ansys Employee

The expression would need the pressure at current & previous time step: that's dP and current time step size for dt.  Thinking about it you're looking at a UDF and needing to store the data. Or write out monitors during the run and use a function in Excel or similar.

• Noushin
Subscriber
Dear Sir
So from monitors in the fluent, I would need to create a variable consisting, Time(T), dp, dt, for calculating the below expression of time averaged time pressure
TAWP=1/T * integration of pressure (P) with respect to t.

Then after simulation I have to export the values into Excel and thus obtain the value. Am I right?
Kindly let me know if I have understood properly.

Thank you

Regards
Noushin
• Rob
Ansys Employee

That may be the easiest approach: we store instantaneous values in the data files so you'd need to manipulate the values outside of Fluent. You can also plot the actual values for use in your work: sometimes the peak values are important too.

• Noushin
Subscriber
Thank you.