Show the vortical structure of parked wind turbine

[QB-Lin]

I am simulating the vortical structure and flow field of a standstill wind turbine under turbulence inflow using AMR-Wind and OpenFAST.

However, the vortical structure generated by wind turbine seems mixed or blocked by the turbulence inflow
Is there any method to classify the vortical structure of wind turbine and those of turbulence inflow?

[hgopalan]

Use an ActuatorSourceTagging (

amr-wind/test/test_files/uniform_ct_disk_dynamic_adaptation/uniform_ct_disk_dynamic_adaptation.inp

Line 29 in 6c47e7f

incflo.physics = FreeStream ActuatorSourceTagging Actuator

) to tag the region of the wake vortex structures.

[QB-Lin]

Here is the vortical structure using passive_scalar as the isosurface (range from 0.7-1.05)

The use of passive_scalar need discussion.
What is the calculation procedure of passive_scalar?
What is its physical meaning?
Does the calculation of passive_scalar have some referenece?
Why the passive_scalar decrease as the wake move downwind?

[marchdf]

The passive scalar is just a scalar that is advected at the flow velocity and diffused according to a user provided constant (that's why it decreases as the wake moves downwind, you can set the diffusion constant to zero if you want to mitigate this). There is no physical meaning to the passive scalar other than what you ascribe to it. It's basically just a tracer variable.

In the case of actuator source tagging as @hgopalan suggested, it is used to tag where there's an actuator source and then trace those seeded tags through the flow. If can be used for whatever the user may want, e.g. dynamic refinement, etc.

[QB-Lin]

How to define the diffusion rate of passive scalar?
Is there any suggestion about the diffusion rate?

[marchdf]

There is no guidance on the diffusion coefficient for the passive scalar. It entirely depends on your use of the passive scalar. The flexibility of the formulation is intended so that users can do what they would like with it. The flip side of that is that we don't have guidance. One example use is for dynamic tagging: #1170. A user could set a diffusion coefficient associated to a time scale that would allow them to tag the wake behind a turbine up to whatever length they would like. But that's just one use case, and if understand correctly, yours is different. I would do some dimensional analysis and back out a reasonable value.