Learning Forum

[20-1-01423]

there is a roof but not still added here, is this process okay? or should i simplify it further? 

im using ansys student, can u help me reach possible meshing in this size, dimension for layout is around 36m x 36m x 3.6m the roof if going up to 6 m (still not added)

 

[NickFL]

I would note two things.

1. Generally you are going to want a much larger Enclosure domain. The wake behind the building can last 100s of meters. But like you said, you are limited by the student license cell count, so you will have to make a trade-off somewhere. (Get use to it, in engineering we must make trade-offs all the time. But the key it to make them based upon good judgement of the physics.)
2. The second thing is are you only going to be specifing the wind in one direction? Or are you going to be evaluating this multiple times with wind out of the north, northwest, west, etc.? If if is the latter, I would recommend creating a cylindrical enclosure around the building. Then have an outer box that has a cut-out for the cylinder. Then you can keep the same mesh for all the wind orientations by just rotating the inner cylinder. Let me know if that is unclear.

[20-1-01423]

Thank you for your reply engr, 

what part should i compromise? im only going for a one wind direction here. 

is my geometry okay? or what

[20-1-01423]

.

 

 

[Rob]

Are you modelling air flow only? Inside or outside of the building? 

If you are going to use Fluent then you may want to read up on thin walls: they're there to stop the flow and don't need a physical thickness. 

As Nick's commented, the outer domain is nowhere near big enough. There are some wind tunnel guidelines somewhere (eg your University library) relating to blockage factor and proximity of the object of interest to the tunnel walls. If you can't respect these (it'll be possible but not easy) you can at least write up the report to explain what you've had to compromise and how you'd do it properly. Check the content in Learning as I'm fairly sure the CFD bounding zone size is covered there: might be in the wind turbine lecture. 

[20-1-01423]

Yes sir, im modelling airflow that goes outside to inside then outside. 

im confused about the wind tunnel guidelines. sorry. and about the Learning can u point the link please because i cant find it.

thank you for your reply very much appreciated 

[NickFL]

Do a scholar.google search for surface mounted cubes. It will show that you will need a substantial downstream and side regions to accurately model the flow. Ideally the side domains will be far enough from the body to be the free-stream values. What are the wind speeds that you are considering? 

[Rob]

There are published guidelines regarding putting things in wind tunnels. These consider blockage factors and how much space you need around the object. They can be a good starting point to design CFD domains. 

Modelling the inside and outside will be relatively expensive for mesh as you need to resolve doors and windows well. Are you looking at cooling too? 

Check in the wind turbine modules, https://innovationspace.ansys.com/learning-library/?search_term=&p_type=learning-library&discipline%5B%5D=Fluids&sort=popular  I know the Fluent Intro course had a couple of slide covering domain size but don't know about the Learning Room course as I don't teach that version. 

[20-1-01423]

Yes sir, the main purpose of this study for cooling, in relation to using a vertical turbine.

thank youu and noted

will ansys student version meet the accuracy for this, especially in meshing or no? given also a larger domain

[Rob]

So you may also need to consider buoyancy effects within the building. 

Student is near enough the same as the full commercial code with the exception of the cell count limits. So, it's accurate but you may not have sufficient cell count to do this properly. Your University may have Research licences which also don't have the cell count limiters.  The intent of Student was to let you learn how to use the various Ansys software tools, it's not intended to be used for large(r) projects, nor to replace University licences. 

[20-1-01423]

yes sir and noted but the univ doesnt have any related lincense for ansys. but still thank you very muchhh for the response