1. School of Mechanical, Industrial, and Aeronautical Engineering, University of the Witwatersrand , Johannesburg 2000, South Africa
2. School of Mechanical, Industrial, and Aeronautical Engineering, University of the Witwatersrand , Johannesburg 2000, South Africa ; , Nanjing 210016, China
3. College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics , Johannesburg 2000, South Africa ; , Nanjing 210016, China