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wind farm parameterization unrealistic results

This post was from a previous version of the WRF&MPAS-A Support Forum. New replies have been disabled and if you have follow up questions related to this post, then please start a new thread from the forum home page.

mgolbazi

New member
Hi,

I am trying to simulate offshore wind farms using WRF wind farm parameterization (Fitch parametrization). I do two separate runs with the exact same setup except that one includes the wind turbines and the other one does not. My goal is to look at the difference between these two to understand the impact of the farms on wind speed.

When looking at the differences in the wind speeds between the two cases (with and without the wind farms), it seems like the turbines cause numerical noise in the model, which to some extend is acceptable. However, the noise seems to grow over time and result in some unrealistic and non-physical results. I attached an example plot at a certain time to this post. The turbines are at the coastal areas but the wind speed seems to increase/decrease significantly far away from the turbine areas.

The slight noise initially originates from the farms which is what I expected and propagates through the domain towards the boundaries. Eventually, the noise gets bigger and bigger and turns into unrealistic high/low wind areas.

My domain is a 400 by 400 grid and has a 4km grid resolution.

I have tried many domain configurations with different grid resolutions, one/two-way nesting, various microphysics options, reducing the time step, increasing or decreasing the number of the vertical layers, but none of them really worked. The only difference was that the large noises appeared at different times.

I also attached my latest namelist to this post.

I was wondering if you can help me with this problem. Any help is really appreciated!

Thank you,
Maryam
 

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This post has been moved to the Physics section of the forum, as this is specific to a physics scheme. Someone will respond to your inquiry soon.
 
Maryam,
The performance of the wind farm parameterization is heavily dependent on input information, e.g., the thrust coefficients, the power curve, rotor diameter, etc. Are you running with the default input files (wind-turbine-1.tbl and windturbines.txt), or you have created your own input files?
We don't have many experiences with this option mainly because we cannot obtain necessary information from the manufacturer. So the information from our users will be helpful for us to better understand the performance of this scheme. Please keep us updated about the progress/possible issues. Also, hope experienced users in the community can also join the discussion.
 
Hi,

This is not probably an answer to your question, but i noticed that you have activated the wind farm parametrization model in your outermost domain which has the coarsest mesh:
'' windfarm_opt = 1, 0, 0, 0, 0, ''

If the other nested domains contain the turbines as well, which I assume they do as you are probably zooming in on the farm location, then try to activate the wind farm model in a finer domain, say the innermost one.
 
Thank you, Karim! This was just an experiment to show the model instabilities in the outer domain. In the main simulations, I have indeed placed turbines and activated the parameterization in the inner domains.
 
have you tried to turn on wind farm option for all the domains, i.e.,
windfarm_opt = 1, 1, 1, 1, 1

It is recommended that physics option should be the same for all domains.
 
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