Mann turbulence model

[f.perrone2]

Hallo everybody,

I'm an italian mechanical engineering student and now I'm carrying out my Msc thesis.
My task is to model a 3d turbulent wind-field model in Matlab.

At the moment I've already implemented the Kaimal and von Karman models by means of the Sandia/Veers method.
My supervisor told me about the Mann model,which better simulate the real behaviour of wind turbulence.Therefore, I would like to implement the Mann model in Matlab in order to compare the results.

So I'm wondering if I could find somewhere a piece of code regarding the implementation,but in the IEC turbulence simulator I did not find anything.

My thesis has no commercial interests,hence I definitively don't mean to handle tha source code in a unpolite way.

I thank you in advance and I look forward to getting an answer whenever possible.
Kind regards,
Francesco

[Morten]

Dear Francesco,


We rarely distribute source code, though you could contact Jakob Mann and ask if he is willing to make an exception for you. But unless you have ideas for extending the model in an interesting way, I doubt that this is a clever way to spend yours and Jakobs limited time. The model is kind of complex and to make it really useful you should link it to flow model results.


Read the following two papers and judge for your self:
J Mann (1998) Wind field simulation, Prob. Eng. Mech.13, 269-282
J Mann (2000) The spectral velocity tensor in moderately complex terrain, J. Wind Eng. Ind. Aerodyn. 94, 581–602


You say that you have implemented Veers' model. The following paper might be of interest for your study:
M Nielsen, G C Larsen, K S Hansen (2007) Simulation of inhomogeneous, non-stationary and non-Gaussian turbulent winds, available at http://iopscience.iop.org/1742-6596/75/1/012060


Regards,
Morten

[f.perrone2]

Dear Morten,

thanks for the early answer;I will have a look at the advised paper.
I read both the Manns articles and I noticed that the code is somewhat complex to be implemented;however,it seems more efficient and less computing-heavy than the Veers method.

Best regards,
Francesco

[f.perrone2]

Hallo again,
the Mann model performs a final fft from the wave number space to the spatial domain.Let's say that:
N1 = 1024;
N2 = 32;
N3 = 32;
L1 = 6140;
L2 = 140;
L3 = 140.
Regard to those values,we have the below wave number vectors:
k1 = i*2*pi/L1; i = -N1/2,...,N1/2 (the 0-th order is elided)
k2 = j*2*pi/L2; j = -N2/2,...,N2/2
k3 = k*2*pi/L3; k = -N3/2,...,N3/2
but there's clearly a size mismatch between [k2,k3](they have N2=N3 elements) and k1;so the question is: how can I evaluate k = sqrt(k1.^2+k2.^2+k3.^2)??
Do I have to fill k2,k3 with zeros for N2/2+1:N1 or what??
The same question arise with the coordinates vector definition.

Could please shed a light? I will be really grateful.
Thanks in advance and best regards,
Francesco

[Morten]

The there dimensions of the Mann turbulence box will ususlly differ because you want to convert the longitudional direction to time via Taylor's frozen turbulence hypothesis. The two other directions should be large enough to model all turbulent eddies hitting the turbine rotor. Thus, lower wave numbers are included for the first velocity component. k is a 3D wave number vector (k1,k2,k3) spanning the wave number space corresonding to the physical space, and k is the length of that vector.