Author Topic: Flat Plate Drag Computations (Read 774 times)

Stoney74 · « **on:** May 02, 2007, 12:09:04 AM »

Is there any relatively affordable software out there that can compute drag coefficients or flat plate drag values for a user-generated 3D model of an aircraft? Or, is there an equation that can be manipulated to determine an approximate range of the same values?

I'm trying to build a computer 3D model of a plane and then test its aerodynamic properties without working on a Cray or spending a gozillion bucks. Just curious if the capability exists...

Not sure if this is the best thread for the question, but given the regular crowd that skulks this thread, I figured I'd give it a shot...

Keiler · « **Reply #1 on:** May 02, 2007, 12:21:31 PM »

I found some open source fluid dynamics software here:

Open Foam

From what I read its capable of doing everything what you need to do fluid dynamic calcs.

Usually these programs use the finite volume method amongst others, so you just need your (not too sub-par) home PC and a bit of time to do calcs. The real complex ones with fine meshes can take a few hours, but results are usually very precise under these circumstances.

Regards,

Matt

Stoney74 · « **Reply #2 on:** May 02, 2007, 09:05:22 PM »

Thanks,

I have seen references to this software before, but not in a format I could understand. This link looks promising...

Brooke · « **Reply #3 on:** May 02, 2007, 11:26:57 PM »

I looked around a little and found Open Foam among others.

I didn't know anything about what software is out there, but did a search on "computational fluid dynamics software" and got links to pages with lots of links to software, such as this one:

http://www.cfd-online.com/Links/soft.html

It seems what you'd need is at least a CFD program and mesh-generator software. The mesh generator takes your 3D model and creates the mesh that covers it. The CFD takes the mesh file and does the computational fluid dynamics.

F4UDOA · « **Reply #4 on:** May 03, 2007, 10:33:00 AM »

Stoney,

Are you looking to calculate drag or do you need flat plate area specifically?

Have you ever seen X-Plane?? It allows you to build 3d models and build your own FM.

Here is a screen shot

Stoney74 · « **Reply #5 on:** May 03, 2007, 07:05:06 PM »

Quote

Originally posted by F4UDOA
Stoney,

Are you looking to calculate drag or do you need flat plate area specifically?

Have you ever seen X-Plane?? It allows you to build 3d models and build your own FM.

Here is a screen shot

What I'm trying to do is set up some testing (however unprecise) for a design I have been thinking about. I was looking for drag values so I could do some theoretical speeds, but the drag equation has more variables than I care to do the calculus for (plus its been awhile since I've done any multy variable calculus). I'm coming up with some 3-view drawings that I want to turn into a model, and then test to see air flows and drag numbers.

I might be going about this the wrong way, but I usually wind up learning a lot when I go on my "teach myself" undertakings. I should probably check it out, or Kev367th recommended the FS developers kit for putting a model together for FS. I figured with today's technology and all the RC builders out there, there would be some of this software floating.

Stoney74 · « **Reply #6 on:** May 25, 2007, 09:13:22 AM »

Did some research on OpenFOAM...

Its Linux based. Is there a way to run Linux on a Windows computer? I don't want to change my OS obviously, but can I install Linux and run it like a program in order to run FOAM?

gripen · « **Reply #7 on:** May 25, 2007, 01:33:39 PM »

You can download a Linux live distribution ie a version which operates from CD/DVD or even memory stick. There are several to choose from and all are free.

Stoney74 · « **Reply #8 on:** May 25, 2007, 07:37:09 PM »

Thanks, I'll have to check that out.

KayBayRay · « **Reply #9 on:** May 31, 2007, 01:09:46 PM »

Dont know about any software out there but... I would start with Bernoullis' Equation and refer to coefficients of friction and thermodynamics of the materials involved. However this requires a rigorous approach to approximate.

Not sure of the scope of your interest.

Later,
KayBay

Stoney74 · « **Reply #10 on:** May 31, 2007, 09:05:31 PM »

Well,

Right now I'm trying to design a Formula One class racer for Reno. I actually got a book by Dan Raymer that I'm working through. Pretty healthy amount of algebra, geometry, and trig in it. I'm coming up with conceptual numbers right now, but I'd like to use the FOAM application once I've got all the dimensions and weights computed. I need a "wind tunnel" to see if I need to change things around, and the FOAM program seems like the best way to do some basic stuff.

Thanks for the input...

dtango · « **Reply #11 on:** May 31, 2007, 10:14:13 PM »

Stoney74, my copy of Raymer came with his s/w as well. It's DOS based but does allow you to evaluate aircraft wings and bodies. I've played around with it but never did much else with it.

Tango, XO
412th FS Braunco Mustangs

Stoney74 · « **Reply #12 on:** June 01, 2007, 12:46:29 AM »

Book's great though. I got the Readers Digest Version "Simplified Aircraft Design for Homebuilders" first. I'm going to grab the textbook version as soon as I work through this one (I think that one has his s/w).He's got an Excel spreadsheet that crunches the hard math for you. I have to reverse engineer some of the math since Formula 1 has specific geometry and power requirements, but its proving helpful. But again, its all conceptual. I want to take a look at how the model will behave before I slap the table on the design, and don't know if I have the know-how to mock it up on the roof of my truck like Rutan did with the Vari-EZ...

Right now I'm trying to select an airfoil and am reading through the NACA Report 824...