|
[Sponsors] |
January 31, 2006, 08:37 |
Error in drag
|
#1 |
Guest
Posts: n/a
|
When I calculate invicid subsonic flow field around airfoil I got 35 counts (Cd=0.035). It result was achieved on different smooth meshes. Node numbers was increased 2X, 4X and result was change to 30 counts (achieved minimum). Who can comment this effect?
|
|
January 31, 2006, 12:51 |
Re: Error in drag
|
#2 |
Guest
Posts: n/a
|
First, you say that you calculated INVISCID flow around the airfoil. This means that you actually calculated "form" drag, am I right? For the complete "drag" you need to activate viscosity. The interesting phenomena is that although both form and viscous coefficients are sometimes wrong, their sum is quite close to the experimental results! So try, you might obtain surprising results.
Secondly, using a dense mesh around the foil (viscous type mesh) in inviscid flow, is very wrong, because Euler formulation tends to increase numerical error in those regions with mesh clustered to the wall. So, increasing mesh density near the wall of the airfoil is actually worsening the numerical solution!!! This is of course not true with Navier-Stokes formulation (if y+ is appropriate to wall treatment used). Be careful, Razvan |
|
January 31, 2006, 13:00 |
Re: Error in drag
|
#3 |
Guest
Posts: n/a
|
Hi Razvan! could you add some details to what you said about grid-density and Euler formulation? I'm very interested to this topic...Luca
|
|
February 1, 2006, 04:01 |
Re: Error in drag
|
#4 |
Guest
Posts: n/a
|
Excuse me! I made mistake i. e. 35 counts = Cd = 0.0035
|
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Pressure drag, friction drag and total drag? | Cheng | CFX | 9 | January 26, 2024 13:46 |
anyone has got this paper? | Al | Main CFD Forum | 3 | October 8, 2007 02:04 |
Drag formulation | REMY | FLUENT | 0 | March 10, 2002 14:05 |
Drag formulation | remy | Main CFD Forum | 0 | March 10, 2002 13:05 |
Inviscid Drag at subsonic, subcritical Mach # | Axel Rohde | Main CFD Forum | 1 | November 19, 2001 12:19 |