해양환경안전학회지 (Journal of the Korean Society of Marine Environment & Safety)

  • 제25권6호
  • /
  • Pages.795-801
  • /
  • 2019
  • /
  • 1229-3431(pISSN)
  • /
  • 2287-3341(eISSN)
해양환경안전학회 (The Korean Society of Marine Environment and safety)
권호 표지
DOI QR코드

DOI QR Code

반구 전방에 생성된 말굽와류 흡입제어에 의한 후류영역 마찰저항 감소에 관한 연구

Skin-Friction Drag Reduction in Wake Region by Suction Control on Horseshoe Vortex in front of Hemisphere

  • 구본국 (창원대학교 조선해양공학과) ;
  • 강용덕 (동의대학교 조선해양공학과)
  • Koo, Bonguk (Department of Naval Architecture and Marine Engineering, Changwon University) ;
  • Kang, Yong-Duck (Department of Naval Architecture and Ocean Engineering, Dong-Eui University)
  • 투고 : 2019.09.27
  • 심사 : 2019.10.28
  • 발행 : 2019.10.31
PDF 다운로드
⟨ 이전 논문 다음 논문 ⟩

초록

층류 경계층 내 반구에 의해 유기되는 말굽와류를 흡입 제어했을 때 후류영역에서의 마찰저항 변화를 측정하였다. 이를 위해 회류수조에서 유동가시화를 실시하여 최적의 자유유속, 반구 크기 및 흡입제어 구멍 크기를 결정하였고, 반구 후류영역에 설치된 평판과 연결된 동력계로 표면 마찰저항 감소를 측정하는 실험을 수행하였다. 평판에 설치된 반구 전방에는 유입 유동에 의해 반구를 감싸는 말굽와류가 생성되며 그 주위 와도 방향에 의해 후류영역으로는 빠른 유속의 유동이 유입되어 머리핀 와류 생성을 촉진시킨다. 따라서 반구 전방에 생성되는 말굽와류 세기를 흡입 제어에 의해 약화시킴으로써 반구 좌우측으로 길게 형성된 유속방향 와류가 후류영역으로 공급하는 에너지는 감소하게 된다. 즉, 반구 전방의 말굽와류를 제어함으로써 후류영역으로부터 생성되는 헤어핀 와류 발생 주파수가 줄어 들게 된다. 염료 주입을 이용한 유동 가시화 영상을 해석한 결과로 머리핀 와류의 발생 빈도가 흡입제어에 의해 36.4 % 감소되었고, 후류영역에서 측정된 표면 마찰저항은 2.3 % 감소되는 것으로 나타났다.

The aim of this study was to investigate the possibility of the skin-friction reduction by vortex control. A vortical system such as a horseshoe vortex, a hairpin vortex, and a wake region was induced around a hemisphere attached on a Perspex flat plate in the circulating water channel. Hairpin vortices were developed from the wake region and horseshoe vortices were formed by an adverse pressure gradient in front of the hemisphere. The horseshoe vortices located on the flank of the hemisphere induced a high momentum flow in the wake region by the direction of their vorticity. This process increased the frequency of the hairpin vortices as well as the frictional drag on the surface of the wake region. To reduce the skin-friction drag, suction control in front of the hemisphere was applied through a hole. Flow visualization was performed to optimize the free-stream velocity, size of the hemisphere, and size of the suction hole. Once the wall suction control mitigated the strength of the horseshoe vortex, the energy supplied to the wake region was reduced, causing the frequency of the hairpin vortex generation to decrease by 36.4 %. In addition, the change in the skin-friction drag, which was measured with a dynamometer connected to a plate in the wake region, also decreased by 2.3 %.

키워드

참고문헌

  1. Abe, H., H. Kawamura, and Y. Matsuo(2001), Direct Numerical Simulation of a Fully Developed Turbulent Channel Flow with Respect to the Reynolds Number Dependence, Transactions of the ASME, 123, pp. 382-393.
  2. Balakumar, P. and E. Widnall(1986), Application of Unsteady Aerodynamics to Large-Eddy Breakup Devices in a Turbulent Flow, Phys. Fluids, 29, No. 6, pp. 1779-1787. https://doi.org/10.1063/1.865605
  3. Doligalski, T. L., C. R. Smith, and J. D. A. Walker(1994), Vortex Interactions with Walls, Ann. Rev. Fluid Mech., Vol. 26, pp. 573-616. https://doi.org/10.1146/annurev.fl.26.010194.003041
  4. Glezer, A.(1998), The Formation of Vortex Rings, Phys. Fluids, 31, No. 12, pp. 3532-3542. https://doi.org/10.1063/1.866920
  5. Guezennec, Y. G. and H. M. Nagib(1990), Drag Reduction in Turbulent Boundary Layers, AIAA J., 28, p. 245. https://doi.org/10.2514/3.10381
  6. Gupta, A. K.(1987), Hydrodynamic Modification of the Horseshoe Vortex at a Vertical Pier Junction with Ground, Phys. Fluids, 30, No. 4, pp. 1213-1215. https://doi.org/10.1063/1.866270
  7. Hung, C. M., C. H. Sung, and C. L. Chen(1992), Computation of Saddle Point of Attachment, AIAA J., 30, No. 6, pp. 1561-1569. https://doi.org/10.2514/3.11101
  8. Hutchins, N. and K. S. Choi(2002), Towards a Greater Understanding of Turbulent Skin-Friction Reduction, Proceedings of the ASME FEDSM, Paper No. 2002-31060.
  9. Iwamoto, K., Y. Suzuki, and N. Kasagi(2002), Reynolds Number Effect on Wall Turbulence: Toward Effective Feedback Control, Int. J. Heat and Fluid Flow, 23, pp. 678-689. https://doi.org/10.1016/S0142-727X(02)00164-9
  10. James, S. and C. K. Madnia(1996), Direct Numerical Simulation of a Laminar Vortex Ring, Phys. Fluids, 8, No. 9, pp. 2400-2414. https://doi.org/10.1063/1.869041
  11. Kang, Y. D., K. S. Choi, and H. H. Chun(2008), Direct Intervention of Hairpin Structures for Turbulent Boundary-Layer Control, Phys. Fluids, 20, pp. 101517-1-101517-13. https://doi.org/10.1063/1.3006346
  12. Kline, S. J., W. C. Reynolds, F. A. Schraub, and P. W. Runstadler(1967), The Structure of Turbulent Boundary Layer, J. Fluid Mech., 30, pp. 741-773. https://doi.org/10.1017/S0022112067001740
  13. Maxworthy, T.(1977), Some Experimental Studies of Vortex Rings, J. Fluid Mech., 81, pp. 465-495. https://doi.org/10.1017/S0022112077002171
  14. Pullin, D. I.(1979), Vortex Ring Formation at Tube and Orifice Openings, Phys. Fluids, 22, No. 3, pp. 401-403. https://doi.org/10.1063/1.862606
  15. Robinson, S. K.(1990), A Perspective on Coherent Structures and Conceptual Models for Turbulent Boundary Layer Physics, AIAA Paper No. 90-1638, pp. 1-16.
  16. Schlichting, H.(1968), Boundary-Layer Theory, McGraw-Hill
  17. Sahlin, A., A. V. Johansson, and P. H. Alfredsson(1988), The Possibility of Drag Reduction by Outer Layer Manipulators in Turbulent Boundary Layers, Phys. Fluids, 31, No. 10, pp. 2814-2820. https://doi.org/10.1063/1.866989
  18. Toy, N. and E. Savory(1983), Turbulent Shear Flow in the Near Wake of a Hemisphere, Proceedings of the 8th Symposium on Turbulence, pp. 145-156.
  19. Tufo, H. M., P. F. Fischer, M. E. Papka, and M. Szymanski(1999), Hairpin Vortex Formation, a Case Study for Unsteady Visualisation, 41st CUG Conference.
  20. Visbal, M. R.(1991), Structure of Laminar Juncture Flows, AIAA J., 29, No.8, pp. 1273-1282. https://doi.org/10.2514/3.10732
  21. Zondag, H. A.(1997), The Dynamics of Hairpin Vortices in a Laminar Boundary Layer, PhD Thesis, University of Eindhoven.