1. Institute of Mathematics for Industry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan e-mail:
2. Wind Energy Department, Technical University of Denmark, Nils Koppels Alle, Building 403, Lyngby DK-2800, Denmark;
3. Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Lavrentyev Avenue, 1, Novosibirsk 630090, Russia e-mail:
4. Schulich School of Engineering, University of Calgary, 2500 University Drive NW, Calgary T2N 1N4, Canada e-mail: