The authors acknowledge with thanks the constant computational help of Hidekazu Tsuji. This work has been done thanks to the fellowship for COE foreign researchers awarded to MI by Research Institute for Applied Mechanics, Kyushu University. Author MI thanks his other colleagues at RIAM for their valuable help: M. Oikawa, Y. Wakata, K. Iga, and R. Ide. The authors acknowledge with thanks the financial support provided by the French Embassy at Tokyo through the scientist exchange program and, in particular, the help R. Fahri has contributed to complete this work. Thanks are kindly addressed to C. Kharif for former discussions.
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