TAGGED: Discovery AIM, drag, fluids
May 29, 2019 at 12:52 pminfoSubscriber🛈 This post originally contained file attachments which have been removed in compliance with the updated Ansys Learning Forum Terms & Conditions
Problem: the cumulative moving average values of the Transient CFD simulation of the drag and lift forces are not assimptotic to the prior Steady State ones.
I set up a parametric study to investigate the aerodynamic resistance of a structural steel angle section in quasi-2d.
For a fixed geometry (L.100.10) I set the wind incidence angle as parameter, extracted the Cd/Cl coefficients and include the results in a chart.
See attached the archived AIM file with results included for the 125°wind incidence angle case.
Please also find some screenshots of model,, mesh and results.
- wind incidence from 0-180° in 5° steps
- k-e standard RANS model in both Steady/Transient cases (none of the parameters changed in-between)
- boundary layers conservatively set, resulting y+ varies between 0.53-17.13
Other than 2-3 wind incidence angles, the Steady State solution converged ’normal’, see the residual plot attached for the 125°case.
The Cd/Cl coefficients are put in a chart – see attached.
In order to ’validate’ the Steady results, I wanted to make sure about what is obvious in CFD theory, e.g. that the long term transient Cd/Cl values are assimptotic to the Steady state ones.
So by only flipping the solver from Steady to Transient (left every setting as default by ANSYS) I left AIM to run for a 10s Transient run.
Unfortunately, the steady and long time average transient values differs a lot – see the attached time history of the Cd/Cl values.
- can you please point out what can be the source of the problem here?
- what turbulence or solver settings (e.g. other RANS models?) should I play around to get more reliable results?
May 30, 2019 at 2:09 amBrian BuenoAnsys Employee
I will have to inquire with our fluids experts about this. There are several validation models you can test located here. There are about a dozen or so fluid flow examples.
May 30, 2019 at 7:11 aminfoSubscriber
Thank you for your response, I'll check those examples if they can be relevant to my study.
One corrigendum to my original post: the transient chart shows the drag and resultant coefficients instead of drag & lift. Here I uploaded the update.
I am looking forward to the opinion of the fluid experts.
May 30, 2019 at 8:43 pmBrian BuenoAnsys Employee
Here is the response:
Without going through the results, this analysis is using a turbulence model that is not appropriate for the application. KE does not do well with separation of flow as the fluid goes around an object. We recommend using SST, in either steady or transient. Try rerunning these models and then compare the Cd/Cl values.
- You must be logged in to reply to this topic.
Boost Ansys Fluent Simulations with AWS
Computational Fluid Dynamics (CFD) helps engineers design products in which the flow of fluid components is a significant challenge. These different use cases often require large complex models to solve on a traditional workstation. Click here to join this event to learn how to leverage Ansys Fluids on the cloud, thanks to Ansys Gateway powered by AWS.
Earth Rescue – An Ansys Online Series
The climate crisis is here. But so is the human ingenuity to fight it. Earth Rescue reveals what visionary companies are doing today to engineer radical new ideas in the fight against climate change. Click here to watch the first episode.
Subscribe to the Ansys Blog to get great new content about the power of simulation delivered right to your email on a weekly basis. With content from Ansys experts, partners and customers you will learn about product development advances, thought leadership and trends and tips to better use Ansys tools. Sign up here.
- Can’t see license on online account
- loss of user settings
- Copy user settings to new release
- help online
- Unexpected graphics error
- Electric Heating – Ansys AIM
- Dwg export error
- Natural frequencies limited to first 6 modes
- Discovery AIM Mesh Error
- ANSYSLI Exited or could not read server port ANSYSLI_FNE_PORT
© 2023 Copyright ANSYS, Inc. All rights reserved.