1. Professor, Key Laboratory on Fluid Mechanics of Ministry of Education, School of Aeronautical Science and Engineering, Beijing Univ. of Aeronautics and Astronautics, No. 37 Xueyuan Rd., Haidian District, Beijing, China 100083 (corresponding author).
2. Ph.D. Student, Key Laboratory on Fluid Mechanics of Ministry of Education, School of Aeronautical Science and Engineering, Beijing Univ. of Aeronautics and Astronautics, No. 37 Xueyuan Rd., Haidian District, Beijing, China 100083.