# natural ventilation modeling

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 November 2, 2009, 11:54 natural ventilation modeling #1 New Member   deepa Join Date: Nov 2009 Location: Los Angeles Posts: 4 Rep Power: 15 Hi All, I am trying to do CFD analysis from a building science approach. I am studying the air flow through louvered window. I want to model a single room with windows on opposite walls, say east and west walls.. The windows will have louvers at 45 angle. I want to visualize the air flow through the louver vanes and examine the velocity inside the space at various points. I would then change the louver angle and observe the changes. This experiment is a series of iterative process. I have been using Design Builder CFD for quite sometime now but have not been successful. I know this tool has not been discussed in this forum. My school had Flow Works in the computer labs, and I want to use that now. But I am new to this tool. So I want to ask the experienced people in this forum if this type of analysis is possible using Flow Works. My school has Solid WOrks as well. I am more comfortable with AutoCad to do the modeling. So if I import the model from AutoCad into Flow Works, will it work fine ? Ideally I want to do a 3D CFD simulation, but I think that can get complicated with the meshing around the louvers. So a 2D air flow analysis works for me at this point of time. I want to be able to see the velocity vectors as output. Any insight is appreciated !

November 2, 2009, 17:21
#2
New Member

murat
Join Date: Mar 2009
Posts: 17
Rep Power: 16
Quote:
 Originally Posted by deepa Hi All, I am trying to do CFD analysis from a building science approach. I am studying the air flow through louvered window. I want to model a single room with windows on opposite walls, say east and west walls.. The windows will have louvers at 45 angle. I want to visualize the air flow through the louver vanes and examine the velocity inside the space at various points. I would then change the louver angle and observe the changes. This experiment is a series of iterative process. I have been using Design Builder CFD for quite sometime now but have not been successful. I know this tool has not been discussed in this forum. My school had Flow Works in the computer labs, and I want to use that now. But I am new to this tool. So I want to ask the experienced people in this forum if this type of analysis is possible using Flow Works. My school has Solid WOrks as well. I am more comfortable with AutoCad to do the modeling. So if I import the model from AutoCad into Flow Works, will it work fine ? Ideally I want to do a 3D CFD simulation, but I think that can get complicated with the meshing around the louvers. So a 2D air flow analysis works for me at this point of time. I want to be able to see the velocity vectors as output. Any insight is appreciated !
First of all, if you use Floworks you cannot do 2d analysis because Floworks solver is based on 3D cartesian grid that so you have 3d geometry model

If your Autocad provides 3d cad model you can export it as step file(step includes all 3d part) than import it to Solidworks may be your solidworks has unique reader for Autocad model you can use also

You mentioned the grid around louvers, if you use Floworks you do not need boundary layer grid because Floworks has an unique capabilities of cartesian grid for example you generate the grid automatically in the solver infomation page you see three type pf grid these are solid,fluid and partial Partial grid is unique grid that one grid define both solid and fluid for this reason you do not need any boundary layer grids and if you use refinement grid tool that is in Intial mesh settings Floworks always check velocity gradient vectors to improve resolution of result so Floworks mesher add more mesh according to solution of any iteration automatically

After finishing first analysis for louvers at different angle you can study with Parametric Study tool in Flow Analysis but how to set up

1- Define your angle with Smart Dimension tool(Annotations)
2- Start Parametric Study and select feature dimension
3- Show the annotation which describes the angle of louvers
4- then select converge variable and run

Murat

 November 2, 2009, 18:34 #3 New Member   deepa Join Date: Nov 2009 Location: Los Angeles Posts: 4 Rep Power: 15 Hi Murat, Thank you very much for your reply !! It is very valuable. I have few questions. How do we export Autocad 3D model as 'step file'. I tried exporting my 3D model. I saw formats like metafile, stl,eps, dxx and others, but could not find 'step file' I want to model 'air flow'. Does it need to be mentioned anywhere about the 'type of fluid'. Is there a separate ' external' and 'internal' CFD simulation ? Because I want to see the flow "through" the external window , does it have to be " external" or "internal" simulation ? Thanks, -Deepa

November 2, 2009, 19:22
#4
New Member

murat
Join Date: Mar 2009
Posts: 17
Rep Power: 16
Quote:
 Originally Posted by deepa Hi Murat, Thank you very much for your reply !! It is very valuable. I have few questions. How do we export Autocad 3D model as 'step file'. I tried exporting my 3D model. I saw formats like metafile, stl,eps, dxx and others, but could not find 'step file' I want to model 'air flow'. Does it need to be mentioned anywhere about the 'type of fluid'. Is there a separate ' external' and 'internal' CFD simulation ? Because I want to see the flow "through" the external window , does it have to be " external" or "internal" simulation ? Thanks, -Deepa
I think there has to be step option in your Autocad(*.stp may be) or you can export the model as parasolid(*.xmt ) or .stl

While setting up the Floworks you can select the type of fluid as air and it is important thing that you define only one fluid in a fluid region so as I mentioned that while setting up the programme you can select air and type of analysis internal or external

If you want to simulate the flow through the window you should select external analysis with checking exclude cavities without flow conditions

Exclude internal spaces.
– Use this option for external flow analyses with
closed internal spaces that you wish to exclude
from the analysis.
• Exclude cavities without flow conditions.
– This option applies to both internal and external
flow analyses. The option is useful for closed
internal spaces with no Boundary Conditions or
Fans specified on their surfaces.
• If you select either of the two options, EFD will fill the
cavities with a solid.

If you face some problem to export 3d model for Solidworks you can send me and I can convert it for you

Murat

 May 15, 2019, 11:08 Cfd on louver #5 New Member   Jayakrishnan Join Date: May 2019 Posts: 3 Rep Power: 5 I'm doing a study on louver in fluent. And it's just a simple set of lovers arranged in a fluid domain with the only input condition being air velocity of 1.7m/s and a pressure outlet. After running when I look at the pressure contour it shows me negative static pressure, which means it has vaccum.interestingly the negative pressure is only formed at the the tips of the louver blades toward the bottom. Any chance I can remove this negative pressure ?

 Tags 2d simulation, air flow, louvers