July 30, 2021 at 2:57 pmrd_asmSubscriber
I am using SST k-omega model for my problem, inflation layers were applied near the solid (bottom) wall.. the wall has a roughness height (k_s) = 0.0009 m and first layer height I used is 2.5e-04.. but for this wall avg Y plus was found to be around 9.0; is it acceptable?
Note- From Literature I was made to understand that for k-omega model avg y plus should be ~1 but due to roughness upto what value of y plus would be acceptable?
Would be grateful if someone provide some insight into it..August 2, 2021 at 11:01 amRobAnsys EmployeeThis is where a blind adherence to y+ and solver maths falls down. For k-w you really want a y+ of around 1, but that makes the roughness larger than the near wall cell. What are you modelling?
August 3, 2021 at 2:25 pmrd_asmSubscriberThank you so much for your reply.. my concern is with that value of y plus, will my results be accepted?
I am solving flow over building problem, inflation applied at the ground.
August 4, 2021 at 10:38 amRobAnsys EmployeeProbably: with building models remember there's a certain amount of uncertainty regarding the ground level, curbs, window ledges, buses and what the airflow does over the neighbouring countryside. I tend to use RNG k-e with enhanced wall treatment (I can give details as I've presented this at an CIBSE external event but can't share the presentation) and focus mesh based on what I need to know. Are you looking at pedestrian comfort, building wind loading, smoke flow etc?
August 5, 2021 at 2:12 pmrd_asmSubscriber@Rob thank you sir for your Reply..
I am solving basically natural ventilation problem..
I have another confusion in my mind now now.. In natural ventilation analysis in buildings, which region is 'critical' regarding application of inflation layers, the ground or the building walls for better solution..
August 5, 2021 at 3:10 pmRobAnsys EmployeeIf you're inside you generally want a "good" mesh throughout and 1-2 inflation layers to give some wall refinement. Given the relatively low flow speed and chaotic nature of the flow you'll find y+ to vary over a wall.
August 6, 2021 at 4:07 amrd_asmSubscriberyes sir y+ is varying and it is very difficult to keep within the 'range' prescribed in standard literature
August 6, 2021 at 9:12 amRobAnsys EmployeeWelcome to CFD modelling! I tend to use RNG k-e with Enhanced Wall Treatment: it's a bit more relaxed re the y+ which is also only really useful to set the first cell height. Given all the interesting stuff happens in the free stream I'd be less worried about it.
Viewing 7 reply threads
Ansys Innovation Space
- You must be logged in to reply to this topic.
Simulation World 2022
Check out more than 70 different sessions now available on demand. Get inspired as you hear from visionary companies, leading researchers and educators from around the globe on a variety of topics from life-saving improvements in healthcare, to bold new realities of space travel. Take a leap of certainty and check out a session today here.
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.Trending discussions
- Suppress Fluent to open with GUI while performing in journal file
- Heat transfer coefficient
- What are the differences between CFX and Fluent?
- Floating point exception in Fluent
- Time Step Size and Courant Number
- Difference between K-epsilon and K-omega Turbulence Model
- The solver failed with a non-zero exit code of : 2
- Floating point exception
- Exporting Data Results
Top Rated Tags