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-   -   Urgent (http://www.cfd-online.com/Forums/openfoam-pre-processing/62081-urgent.html)

ivanyao March 19, 2008 03:19

hi i want to know if there s
 
hi
i want to know if there someone use openfoam to calculate the wind pressure on the building?

platopus March 20, 2008 11:18

Hi, I don't think your quer
 
Hi,

I don't think your query really belongs here in the FoamX section of the forums, and to do what you want requires quite a bit of knowledge and skill to achieve with OpenFOAM.

I don't know how much you know about the things that are required, but I'm guessing you're a novice like me.

First you'll need a 3d CAD model of the surface of your building. You might be able to approximate it with a simple rectangular prism on a flat base in a box. It'll have to be in a format that some meshing software understands, but if it's that simple it might be done in a text editor.

Then you'll need to mesh the geometry to give a solver a framework within which to solve your problem. There are a number of free or open-source options for meshing, or you might be able to use OpenFOAM's own Blockmesh.

Then you'll need a solver to run. This is where OpenFOAM really comes in. You need a solver that will simulate the airflow around your building and give you an accurate solution in reasonable time on a reasonable-sized machine with a reasonable amount of memory and processing power. Here, the various appearances of the word 'reasonable' means something you can live with - something you have or can get hold of.

Someone on one of the OpenFOAM forums recently did a calculation of the force in a turbulent flow on a cylinder, I think. It's possible that he/she might share the code for that calculation, but it should really be as simple as adding up a bunch of vectors after the calculation is done - unless you want it recomputed during the simulation.

If you're comfortable with C++, that could help a lot, because OpenFOAM makes heavy use of it, and modifying a solver means understanding at least some of it.

There are quite a few solvers available 'out of the box' that have been tested and used a lot. If one of them can do the job unmodified or nearly so, then so much the better.

If it all sounds like too much hard work, and you're not up to reading the english documentation and the info on the web, now might be a good time to bail out and go do something else.

Why do you want to calculate wind pressure on a building, anyway?

What's the urgency?

ivanyao March 21, 2008 10:37

hi thank you!i am a master
 
hi
thank you!i am a master of civil engineering。i must finish the paper。
by the way,how can i contact the man who did a calculation of the force in a turbulent flow on a cylinder?

platopus March 21, 2008 14:08

"i am a master of civil engine
 
"i am a master of civil engineering"

Okay, I take that to mean that you should be familiar with the mathematics, but not necessarily the fluid dynamics or the C++ programming language.

"I must finish the paper"

"I love deadlines. I especially love the whooshing sound they make as they fly by." -
-- Douglas Adams

I heartily recommend his books. :-)

"how can i contact the man who did a calculation of the force in a turbulent flow on a cylinder?"

I guess you'd leave a message for him in a thread in which he is active. Read the following thread and take it from there:

http://www.cfd-online.com/OpenFOAM_D...tml?1199336135

Note that he's using a 2d cylinder, but everything in OpenFOAM is really done in 3d.

There's also a thing called liftDrag , that appeared in OpenFOAM 1.2, I think, and which could be added to a more recent version. Read about it here:

http://www.cfd-online.com/OpenFOAM_D...tml?1151231653

If all you want is a false colour map of pressures on the surface of the building, I think it ought to be possible to get that from a standard solver and viewing the results in parafoam.

I plan to download new versions of the software later today, and play with it shortly thereafter. Perhaps I might be able to be of some assistance to you as you work through your problem.

I'd wish you a happy Easter, but it's unlikely you celebrate it.

What sort of building is it? Is it a complicated geometry?

ivanyao March 22, 2008 07:33

hi thank you very much!the pr
 
hi
thank you very much!the problem is i can't build the modeling,even the simple one~~~,if i have any problem,can i leave a message to you?my email address is ivan_ywh@yahoo.com.cn,or we can discuss with the email..will you?

platopus March 22, 2008 19:19

I'm sending you email. There
 
I'm sending you email.
There might be a (relatively) simple way to help you, if you can tell me more about your situation and problem.


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