Learning Forum

[skdubey]

Dear Friends,

 

I am having an issue with the design points, Whenever I tried to update the design point in the fluent, I am getting the same answer. I have share the below steps for your suggestion

a.Upload the geometry model> create the mesh> Create the boundary condition Inlet P and OutletP

b.Open the Fluent solver, Flow model> type of fluid > setting the cell fluid > Boundary condition ( I create the Inlet P and Outlet P both as input parameter for my application

c.I initialize the solution suing the hybrid method> RUN the solution

Result step within the fluent: I choose the surface integral> facet avarage > outlevelocity>compute> save as output param

 

d.I save the Fluent  with the option call as “use the setting for the current and future setting option”. Many told this is important step or else you might find the similar error

e.Close the fluent and open the parameter and change the design points: I am getting the following the same Outlet velocity for all the different pressure which is not possible any suggestion will be really helpful.

 

f.I found the similar issue but no accurate solution: https://www.cfd-online.com/Forums/fluent/125869-getting-same-output-values-different-values-parameters-workbench.html

 

[Rob]

In Fluent set the Reporting Interval (Iterate panels) to 5. Given the change in inlet parameter is small it's possible the convergence checks are met before anything happens in the solver. Forcing a larger number of iterations first should fix this.  

[skdubey]

@rob

A. Above Problem: What is the larger number of iterations, do you mean to increase the number of iteration on the fluent side, generally, I kept the iteration around 250 on the fluent side and for FSI is around 5 time step (both fluent and structural models are steady and static).As the load is ramp up for each time step, is it fluent iteration or FSI time step maximum iteration in coupling system to increase which one?

B. Doubt about FSI: I am currently involve with the steady and static 2-Way FSI, I just put the time step in the coupling system 5 with maximum 5 iteration. I am not sure, if we use the static strucutural should we use only the 1-time step with n-number of maximum iterations? sometime, when I re-run my fsi model, it give me error that the time step must be higher than earlier one. I feel bit skeptic since each time step of coupling, the static load will be ramp up and then the information will be exchange between the fluent and vice versa so. I am not sure, if I am right, I tired to dig the manual for the system coupling, its difficult to get the theory behind it any suggestion?

[Rob]

You didn't say anything about FSI. The Reporting Interval I mentioned is here, middle panel. 

See if that helps. 

[skdubey]

@Rob, I even tried using just the fluent alone and check if changing the input parameter cause any changes in the output parameter. I tried the same step without fsi creating model> assiging the fluid to cell> providing inlet P condition with the input parameter> intiailzie the solution > run > results> surface avg outlet vel> save outlet param> save the fluent setup by using the change for current and future calculation > close fluent clicked on the parameter and started input different design points and still same answer ...this making bit frustrated rare occasion it runs and other time just give me the same value. 

any suggestion

[Rob]

And you've set the update in the Solver panel as 5? Can you check the residual checker/monitor panel too?

[PAWAN KUMAR]

 

Facing a similar problem in my case too. (I'm working on CFX)

Despite varying the speed of rotor (rad/s) at various design points, the torque of the rotor is yielding constant values.

Please Help.

 

[Rob]

Please post in a new topic - I don't know enough about CFX to help.