[fluent_noob]

Hello,

I use Ansys 2019R1 w/ academic license. I am relatively new to Fluent. I wanted to generate sinusoidal pressure pulse as the input. I understand that there are three ways to implement this:
1. plotting the function w.r.t. time, tabulating it and using the result table directly.
2. User defined functions
3. Expressions
My queries are:
1. For convenience to my purpose, I am using expressions. I referred https://www.ansys.com/blog/tips-and-...nsys-fluent-ui. I don't understand the syntax of the expression. Why is it written as sin(Time/[s])? As in why the seconds as inverse? Please explain the syntax briefly. How can I provide a pressure pulse of the form Asint(wt + x) [Pa]?
2. Please link a document/research paper giving the details of expression synatx.
3. I have to use a square wave pulse later. I see that it's not possible to use sgm function in the expressions. How can this be achieved?


Thanks

[AlexanderZ]

your example looks like

(sin(Time/1[s]))*90000[Wm^-3]

Time/1 has unit [s]

for your expression Asint(wt + x) find out first what are w t x

For more complicated boundary conditions use UDF, DEFINE_PROFILE macro
more details in Ansys Fluent Customization manual

[mrkmrk]

Hi everyone,


Is it possible to use the variables' values of previous time steps in ANSYS Fluent expressions to define the values of those variables for the current time step? For example I want to define the pressure or flow rate at the inlet as function of their values at outlet at the previous time step as:


P_Inlet=Average of Pressure at outlet at previous time step.


Many thanks in advance.

[LuckyTran]

You need to use the export option solve/set/expert and answer yes to the question "Keep temporary solve memory from being freed?"

This option let's you use the fields from the previous timestep (they have different names like pressure n-1). Then you can do whatever you want. You can create reports to calculate the average pressure but not using the field named "pressure," use the corresponding pressure from the previous time step. These fields will show up in the GUI editor so you can interactively define your expressions. But they will not show up until you enable the option. Oh and you need to do at least one more time step for the fields to appear since the fields need to be generated and held in memory.

Some fields are always held, some are freed so you may or may not need to do this expert setting. It also depends on your temporal discretization how many time-steps exist at any given state. But try that as a start to see if it is good enough.

[mrkmrk]

Dear LuckyTran,


I really appreciate your valuable help.



I need to give it a try.


Thank You!