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zscheck March 13, 2012 00:12

Air flow through intake manifold
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I have designed an intake manifold for a 4 cylinder gasoline engine and am trying to test my design using ANSYS. I have read through other posts, but I am having trouble finding something like what I am looking for. I have a table in excel for the pressure drops will occur at the end of the runners due to intake valves opening and closing, also I have no problem importing my drawing from Solidworks. I however do not know how to even start meshing the geometry of the intake, let alone how to independently control the outlets of the runners. In my reading I have heard a lot about making a big block around the object but it seems to me I should just use the solid intake (not the shell of it). I have included a picture of the geometry of the intake if that helps.

any help would be greatly appreciated

stuart23 March 13, 2012 11:52

Hi Aaron,

That intake plenum and 20mm restrictor look rather familiar..... CBR600...?

You need to extract the "fluid volume" as it's own solid. Try using Boolean functions in Solidworks so that you end up with a solid of the same shape as the air inside the plenum. You then have to apply boundary conditions to the intake ports and throttle opening. For the throttle opening, you will probably want to use a "pressure inlet" with atmospheric pressure. For the intake ports, you can either use a profile (a time series representation of the pressure drops (hint:from Ricardo)) OR you can do a steady state simulation and just set one port with the pressure drop.

Good luck


diamondx March 13, 2012 12:07

the calculation you will is on the fluid. so you need a fluid domain. i have made a video in youtube about how to extract the fluid domaine here is the link :
come back to us later if you have more question

zscheck March 13, 2012 19:35

Thanks for the help both of you, diamondx I was unable to follow the link for some reason. Good eye Stuart, actually for a Kawasaki but most likely same application, FSAE. for getting the fluid volume I just suppressed the shell feature, as I shelled it outward, the solid is the volume I need.

that seems to have worked but I am still pretty lost on how to assign inlet and outlet, and where to insert the excel file for pressure drops.

thanks again

scipy March 14, 2012 11:32

You if you have a 1 solid body now do the following:

1. Import the solidworks model into DesignModeler.
2. Edit the geometry in DM by changing the type of the body from Solid to Fluid. You can also assign inlets and outlets at this stage, but I like to do it in ANSYS Meshing.
3. In the Workbench, go to the next step which is Meshing. There you can choose the face selection tool from one of the top toolbars and select each of the faces, right click -> Created named selection and then name then either pressure-outlet, velocity-inlet or anything else. Also you can do some preliminary meshing right away. I'd suggest using a tetra mesh to capture your geometry more easily, add some inflation for boundary layers, set up the parameters for a decent volume mesh and Update.
4. After this you go into Fluent (or your solver of choice), choose a turbulence model, set up the material as Air or whatnot, and set up the boundary conditions for inlets/outlets. There will be a parameter button there where you can choose a pressure change chart from a csv/dat file which you can get from excel.. However, you simulation is going to have to be transient for it to work properly.
5. There's all sorts of things to do in Fluent before you can do a successful run, but you should first consult some literature/help files on this.

A series of videos I'm doing on external CFD might help you as far as geometry prep and meshing go (you can basically use same settings that I used in the video.. you're just doing it for an internal volume). Videos can be found here:

I'm hoping I'll have time for Fluent parts shortly.

P.S. you only need to assign named selections to your inlets and outlets, the walls of the plenum and intake pipes will be automatically detected as "wall" in Fluent. You can also give them named selections for better control of element size on piping/plenum etc, but it's not mandatory.

P.P.S However, if you are not looking for anything serious (simulation wise), there is a intake manifold simulation video for SolidWorks simulation on youtube: So maybe you can try it in SW first (it's a bit more user friendly than having to learn to use Fluent).

zscheck March 15, 2012 22:41

thanks, your videos and instructions were very helpful. The main problem I am having with it right now is that I do not understand how to set the outputs to what I need, as stated above, I have an excel file similar to the one in the last video linked (mostly because I saw that and figured most CFD software worked the same) but I dont know how to set the outputs to this.

I agree with your last thought there, I am not looking for something that complex, I would just like to verify that my design works... it would not take much to improve on the previous design. My problem is that while I have access to ANSYS and now Autodesk simulation Multiphysics, I only have a student version of Solidworks so I cannot do flow analysis on multiple outlets(otherwise I would have used that already, it seems the easiest and has the most help on youtube) I am trying to gain access to a full version of solidworks. I have started trying to mess with Autodesk but that is proving less helpful than ANSYS.

thanks for the help again though

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