CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

Fractional Step Method failing for propeller simulation

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Search this Thread Display Modes
Old   July 7, 2022, 03:18
Default Fractional Step Method failing for propeller simulation
New Member
Varun V P
Join Date: Jun 2020
Posts: 11
Rep Power: 6
VarunV is on a distinguished road
We are studying the effects of oblique flow on variable pitch propellers, and we did wind tunnel experiments for these. Now I am running CFD simulations to study the flowfield.

This is the domain. There is a cuboid of dimensions 2.5 x 2.5 x 2.5 m, within which I have 2 cylindrical halves for each blade. Within them I have another cylinder which actually encloses the blade. The middle and the inner domain have a conformal mesh. I did this so that I can quickly rotate the inner section to simulate different pitches.

The strategy I was following is to first run the steady state simulation for 500 iterations, with the transition-SST solver (other transition solvers are crashing) and SIMPLE coupling, and then switch to NITA FSM for transient because it's faster, and I assumed that the solution will be unsteady at higher oblique angles.

While this strategy worked for the no-wind simulations (CFD results close to experimental,) I am getting divergence in the continuity equations when I give a velocity input of 10 m/s. This happens in the transient part, static is able to converge well till 1e-3 for continuity. On observing the velocity contours I observe spurious sections with very high speeds, near the inlet (>200 m/s).

Some sections of the mesh could do with some refinement, so I enabled automatic adaption for volume change and mass imbalance, every 10 iterations. I also reduced the under relaxation parameter to 0.1 for the momentum eq. I am still observing divergence. I ran the simulations with a more refined mesh, but I am still observing the same issues.

As a stopgap solution I am now running the simulations with SIMPLE pressure coupling because it works, though it takes a lot of time. But I still want to know why this problem is happening. Could it be because the compressibility condition is not able to be satisfied, acc to this (Monitoring residuals , is it safe ?
Attached Images
File Type: jpg Screenshot 2022-07-07 114806.jpg (41.6 KB, 0 views)
File Type: jpg Screenshot 2022-07-07 114928.jpg (48.5 KB, 0 views)
VarunV is offline   Reply With Quote


continuity error, fractional step method, nita, transient analysis, velocity

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Numerical implementation of Boundary conditions in fractional step method jollage Main CFD Forum 13 November 16, 2021 09:48
Rhie-Chow interpolation in Fractional Step Method AliE Main CFD Forum 5 December 10, 2018 08:16
Floating point exception error lpz_michele OpenFOAM Running, Solving & CFD 53 October 19, 2015 02:50
Help for the small implementation in turbulence model shipman OpenFOAM Programming & Development 25 March 19, 2014 10:08
Upgraded from Karmic Koala 9.10 to Lucid Lynx10.04.3 bookie56 OpenFOAM Installation 8 August 13, 2011 04:03

All times are GMT -4. The time now is 16:23.