[Nek5000-users] Visualizing lambda2 vortices

[nek5000-users at lists.mcs.anl.gov]

Hi Paul,

The animations are very impressive ! I can now spot the hairpin structures
in my flow but it required a much higher value of lambda2- about -200 or so.
A=temperature and B=velocity worked really well. Thanks.

Regards
Shriram


On 30 September 2010 05:24, <nek5000-users at lists.mcs.anl.gov> wrote:

>
> Those are lambda2s, with pressure mapped onto the isosurface.
>
> Here is another - www.mcs.anl.gov/~fischer/hemi/hemi_0700.gif
>
> These are isosurfaces of lambda2 (probably lambda2 = -.1 or something
> --- usually a slight negative bias is required).
>
> In VisIt, you can select an isosurface of scalar A and then map
> scalar value B onto that surface as a pseudocolor plot.
>
> The plate and hemisphere are visualized by setting A to
> be velocity magnitude=.0001 (say) with B=pressure.
>
> The lambda2 vortices are visualized by setting A to be temperature
> (which is where lambda2 is stored in my case) and B to be velocity
> magnitude.
>
> (Choosing B to be pressure for both the walls and the vortices
> did not yield high contrast...)
>
> Paul
>
>
>
>
> On Wed, 29 Sep 2010, nek5000-users at lists.mcs.anl.gov wrote:
>
>  Hi,
>>
>> I was looking at Paul's pretty picture (
>> http://www.mcs.anl.gov/~fischer/cfd/hairpin_split.html) which I assume is
>> iso-surfaces of vorticity and had a question regarding visualizing lambda2
>> vortices. I have the lambda2 vortices calculated and stored as a passive
>> scalar in the field files but cant figure out a way to visualize them. How
>> do you generally visualize the dominant structures in the flow, say for
>> eg,
>> the hairpin vortices in the same animation ?
>>
>> Regards
>> Shriram
>>
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