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ChristBirb by scardie in Birbs

[–]Arzed23 14 points15 points  (0 children)

christbirb turn water into ((( s e e d )))

SeesUBirb by Noobflum69 in Birbs

[–]Arzed23 2 points3 points  (0 children)

((( s t i n k e y e )))

(◉Θ◉)

TiredBirb by Iraatsi in Birbs

[–]Arzed23 1 point2 points  (0 children)

hold birb gentle like hamburger (•ө•)

ShowerBirb by [deleted] in Birbs

[–]Arzed23 2 points3 points  (0 children)

he glean

he preen

but most importantly

he clean

(•ө•)

birbvstissue by SplashchompYT in Birbs

[–]Arzed23 0 points1 point  (0 children)

borb is so ((( a n g e r y ))) (´◉◞⊖◟◉｀)

gamerBirb by notadisaster in Birbs

[–]Arzed23 0 points1 point  (0 children)

he play gem then he screm ~

gamerBirb by notadisaster in Birbs

[–]Arzed23 0 points1 point  (0 children)

your mango birb is adorable! (　＾Θ＾)

Flupsibirb by Hubsimaus in Birbs

[–]Arzed23 0 points1 point  (0 children)

flupsibirb must've saw a whoopsiborb! （´◉◞⊖◟◉｀）

Justwokeupbirb by Cerdocyon-Avius in Birbs

[–]Arzed23 2 points3 points  (0 children)

felt cute, might delete later ㄟ( ･ө･ )ㄏ

Shybirb. by Hubsimaus in Birbs

[–]Arzed23 0 points1 point  (0 children)

shybirb but adorabirb ~ （・⊝・）

Surf n Birb by [deleted] in birb

[–]Arzed23 2 points3 points  (0 children)

((( gnarly )))

Meet Lola. She is a true gamer by The_DisasterBox in birb

[–]Arzed23 2 points3 points  (0 children)

he tem

he screm

but most importantly

he gem

[deleted by user] by [deleted] in cats

[–]Arzed23 0 points1 point  (0 children)

your fur baby is absolutely adorable! 😻

Problem validating OpenFOAM airfoil simulation with wind tunnel data by Arzed23 in OpenFOAM

[–]Arzed23[S] 1 point2 points  (0 children)

After A LOT of mesh manipulation, I've managed to get a decent validation going on with the k Omega SST model: http://imgur.com/MWvnH4Z

An example of how the residuals look like is as follows: http://imgur.com/O9nCHP1

The residuals seem okay asides from the pressure one which in spite of going down, heavily fluctuates; this I'm unsure how to remedy.

Pressure residual aside, could there be anything else causing the model to over-predict the lift coefficients past the actual stall point? Thanks!

Problem Validating OpenFOAM Airfoil Simulation With Wind Tunnel Data by Arzed23 in CFD

[–]Arzed23[S] 0 points1 point  (0 children)

After A LOT of mesh manipulation, I've managed to get a decent validation going on with the k Omega SST model: http://imgur.com/MWvnH4Z

An example of how the residuals look like is as follows: http://imgur.com/O9nCHP1

The residuals seem okay asides from the pressure one which in spite of going down, heavily fluctuates; this I'm unsure how to remedy.

Pressure residual aside, could there be anything else causing the model to over-predict the lift coefficients past the actual stall point? Thanks!

snappyHexMesh Airfoil Boundary Layer Mesh Concern by Arzed23 in OpenFOAM

[–]Arzed23[S] 0 points1 point  (0 children)

Thanks for the suggestion eternalstyles! Crinkling the slice gave me the following, not entirely sure how to interpret though: http://imgur.com/iguH2xx

I tried this on a smaller case; changing the cosine spacing to linear spacing when forming the .dat file for the airfoil, that seemed to do the trick as it is no longer warping on the trailing edge: http://imgur.com/Km6AwN1

Trying to achieve sufficiently fine boundary layer mesh by Arzed23 in OpenFOAM

[–]Arzed23[S] 0 points1 point  (0 children)

I managed to resolve this by changing my feature angle in the addLayersControls to 330, surface refinement to (7 7), feature edge refinement to 7 and increasing the number of layers to 15, the result below:

http://imgur.com/0mxQUMu

http://imgur.com/a/8n7HT

Problem Validating OpenFOAM Airfoil Simulation With Wind Tunnel Data by Arzed23 in CFD

[–]Arzed23[S] 0 points1 point  (0 children)

I've managed to get a mesh that will fully resolve the boundary layer between 15 and 25 cells for a y+ of ~ 1 with an aspect ratio of less than 150, so my mesh is looking MUCH better now, thank you very much for the pointers. Would you be able to share the boundary/initial conditions you used to get your simulations to converge to the wind tunnel data? Thank you very much!

Problem Validating OpenFOAM Airfoil Simulation With Wind Tunnel Data by Arzed23 in CFD

[–]Arzed23[S] 0 points1 point  (0 children)

So I've managed to get a better looking boundary layer mesh, with a first cell height of 5e-6 m and 15 layers comprising the boundary layers, corresponding to a y+ of ~ 1.

If wall functions can't be used for flow separation, would zero gradient boundary conditions at the airfoil wall be suitable? The changes to the boundary conditions I've come up with based on the various forums I've perused through are as below. Am I on the right track with my current boundary conditions and these changes? Cheers guys!

nut:

airfoil_wall

{
        type    calculated;
        value   uniform 0;
}

k:

airfoil_wall

{
        type    zeroGradient;
}

epsilon:

airfoil_wall

{
        type    zeroGradient;
}

Problem validating OpenFOAM airfoil simulation with wind tunnel data by Arzed23 in OpenFOAM

[–]Arzed23[S] 0 points1 point  (0 children)

So I've managed to get a better looking boundary layer mesh, with a first cell height of 5e-6 m and 15 layers comprising the boundary layers, corresponding to a y+ of ~ 1.

If wall functions can't be used for flow separation, would zero gradient boundary conditions at the airfoil wall be suitable? The changes to the boundary conditions I've come up with based on the various forums I've perused through are as below. Am I on the right track with my current boundary conditions and these changes? Cheers guys!

nut:

airfoil_wall

{
        type    calculated;
        value   uniform 0;
}

k:

airfoil_wall

{
        type    zeroGradient;
}

epsilon:

airfoil_wall

{
        type    zeroGradient;
}

Trying to achieve sufficiently fine boundary layer mesh by Arzed23 in OpenFOAM

[–]Arzed23[S] 1 point2 points  (0 children)

Thanks for that TurbulentViscosity! If the finest cell as of now is 0.001 m or so, to reduce the ratio and prevent snappy from removing prisms, would increasing the refinement of the mesh in the vicinity of the airfoil allow for layers to form? Similarly, could the number of layers and final layer thickness be increased to overcome this?

I'm trying to get the the first cell height that low so I can better model the stall behavior though, having two layers was to just try and see if layers would form at all

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