Fluids

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.
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