[1] Natl Inst Technol Rourkela, Dept Math, Rourkela 769008, India
[2] Natl Inst Technol, Dept Mech Engn, Silchar 788010, India
[3] City Univ London, Dept Mech Engn & Aeronaut, London, England
[4] Indian Inst Sci, Dept Aerosp Engn, Bangalore 560012, Karnataka, India