CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

[FloWorks] Request advice for an airfoil calculation problem

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   September 29, 2009, 17:06
Question [FloWorks] Request advice for an airfoil calculation problem
  #1
New Member
 
no please no...
Join Date: Sep 2009
Location: France
Posts: 1
Rep Power: 0
Bogey Jammer is on a distinguished road
Hi all, my first post here

As a hobby (and my job is not related with aircrafts), I'm trying to create a custom designed aircraft, in order to introduce myself to aerodynamics.

The WIP:





I've put it on a hold because it's time to design the wing. And since I want to understand the much info as possible, I decided to use the embedded CFD software to the CAD software that I use, respectively CosmosFloWorks and SolidWorks.

CosmosFloWorks is excellent for simple hydraulic problems, but in aerodynamics, it seems to bring weird results and behavior according to my past experiences.
So I decided to give it a chance again and started to compute a know airfoil detailed in:



My goal is to reach the real results in order to thrust this software and continue to use it for aerodynamics.
I've chosen to compute the airfoil at Reynolds=2.9 x 10^6 and alpha=4, quite a simple situation, but as I expected the results are still wrong.. I'm currently trying to get a Cd between 0.01 and 0.015, and a Cl of 0.78, but the results say Cl=0.55 almost every time...

How I did:

I've set up a quite large computational domain but 0.024m thick (2D study situation):



Note that the airfoil chord measures 0.6 meter.

Then the mesh:



Composed with parallelized rectangles, smaller near the airfoil, larger at corners, detailed in rounded surface, and automatically detailed during calculation with the flow (in the leading edge area and trail).

The coefficient calculation:

CosmosFloWorks computes many values and parameters but I still need to enter equations to get the coefficients.
I got them from calculated force components (Cl=Yforce/(q0*0.6*cos(4)*0.024) and from pressure coefficients (equation is more complicated but the result is quite the same). So unfortunately both of these methods get a wrong result.

The speed setting and conditions:

I entered the windspeed according to the Reynolds number with standard atmospheric conditions. I'm sure it's good because I get a calculated Mach number of 0.2 like the real results. The material is set to adiabatic and without roughness.

Comparison with XFLR5:

Prior using CosmosFloWorks, I tried the airfoil in XFLR5 software using XFoil engine to analyze airfoils.



And surprisingly, it managed almost instantly to find the correct results...
I noted that the boundary layer just after the trailing edge is different in XFLR5, making me seriously doubting about CosmosFloWorks behavior.



For information, static pressure:



So, the questions are:
  1. Am I wrong somewhere?
  2. Can someone who has experience with this software comment this problem?
  3. Can we really thrust this software?
  4. Do I seriously need something to learn before going any further?

Thanks in advance

I can post more details if needed.
__________________
Super Signature
Bogey Jammer is offline   Reply With Quote

Reply

Tags
airfoil, cosmosfloworks, solidworks, xflr5, xfoil

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Airfoil boundary condition Frank Main CFD Forum 1 April 21, 2008 18:36
Verfication problem in cd/cl - advice required CH Main CFD Forum 4 November 13, 2006 21:38
solving airfoil like square cylinder problem? zonexo Main CFD Forum 1 May 27, 2006 15:16
Advice for convergence problem David CFX 4 November 3, 2002 04:00
CF4 - need advice on setting up multiphase problem Brett Towler CFX 2 August 18, 2000 16:38


All times are GMT -4. The time now is 04:30.