WAsP wake modelling

[HPJ]

Hi,

I'm trying to find information about the actual implementation of the PARK model in WAsP. The documentation I have so far been able to find only describes how to calculate the velocity deficit for a single wake. That is using the free-stream velocity as input to the deficit calculation. This is shown on page 5 (dV01) in this presentation: http://www.risoe.dk/vea/storpark/presentations/WAsP8%20Wake-effect%20model.pdf. Another expression is also shown (dV12). It is unclear what U1 and V1 represents?

Is any "cascading" effects accounted for? That is, is the model initiated with a free-stream velocity at the most upstream turbine and then the velocities used in the deficit calculation reduced with the wake effects down the 'rows'?

Are any speed-up effects accounted for? And if so, how?

I guess what I'm looking for is a more in-depth explanation of the implementation in WAsP.

Thank you as always!

-HP

[Ole Rathmann]

Hi Hans-Peter (from Siemens), the Park-model in WAsP is discribed in the follwing report and paper:
a) Jensen, N.O (1983). A Note on Wind Generator Interaction. Risø-M-2411,
b) Katic, I, Højstrup J. and Jensen, N.O. A Simple Model for Cluster Efficiency. Proceedings of the 1986 European Wind Energy Conference and Exhibition, Rome, Italy, October 7-9, paper C6.

Both are available from the literature-page of the WAsP web-site:
http://www.wasp.dk/Support/Literature

a) contains the basic N.O.Jensen wake model (single wake) used in the Park-model while b) contains the description of the wake-wake interaction (the empirical sum-of-squares of speed-deficits rule). Please notice that the Park-model uses reflection of the individual wakes in the ground surface to represent wake interaction with the ground surface as well as a partial-overlap factor (how much of a certain rotor is covered by the wake from a certain upwind turbine).

Ole Rathmann.

[crivero]

Hi Ole Rathmann,
I have read both, Jensen and Katic papers, and still have two questions I hope you can help me with:
1) Exist a distance limit to apply or not the deficit equation? For example, if a turbine is located 20 diameters away from the upwind turbine, does WAsP uses the deficit equation to find it? Is the wake propagation infinite?
2) Can you please elaborate a little bit more on the "reflection of the individual wakes in the ground surface"?