한국수자원학회논문집 (Journal of Korea Water Resources Association)

  • 제37권3호
  • /
  • Pages.219-231
  • /
  • 2004
  • /
  • 2799-8746(pISSN)
  • /
  • 2799-8754(eISSN)
한국수자원학회 (Korea Water Resources Association)
권호 표지
DOI QR코드

DOI QR Code

Bubble plume의 중첩효과가 저수지 성층파괴 효율에 미치는 영향에 대한 수리동역학적 2상-3차원 평가

Evaluation of Destratification Efficiency by Combined Effect of Adjacent Plumes through 2-Phase and 3D Hydrodynamic Analysis in a Stratified Fluid

  • 염경택 (한국과학기술원 건설ㆍ환경공학과) ;
  • 박희경 (한국과학기술원 건설ㆍ환경공학과) ;
  • 안제영 (한국과학기술원 건설ㆍ환경공학과)
  • 발행 : 2004.03.01
PDF 다운로드
⟨ 이전 논문 다음 논문 ⟩

초록

수중폭기장치로 저수지 성층을 파괴시켜 저수지 수질을 개선시키기 위한 방법이 최근 널리 이용되고 있다. 본 연구는 주요 성층 파괴기작인 Bubble Plume(공기 부력류)의 수리동역학적 거동특성과 플륨 간격에 따라 변하는 모멘텀 중첩효과가 성층파괴 효율에 어떠한 영향을 미치는지에 대하여 수행하였다. 이를 위해 전산유체(CFD) 소프트웨어를 이용한 2상(공기-물) 3차원의 탈성층모델을 개발했으며, 이로부터 계절에 따라 변하는 다양한 성층강도와 주입 공기량에 따라 변하는 비정상상태의 성층파괴 발달과정은 물론 최적 탈성층 효율을 갖는 플륨간격을 제안할 수 있었다. 모델검증을 위한 실험을 위해 대형 실험조를 개발했으며, 온도성층은 소금물을 이용했던 기존연구와는 달리 가열순환수를 이용한 자연성층을 재현시켜 수행하였다. 연구결과 탈성층 효율은 디퓨서 배치간격에 크게 영향을 받는 것으로 밝혀졌으며, 플륨간격이 수심의 약 1.5배 이내익 때 중첩영향이 강하게 일어났고, PN가 클수록 간격에 영향을 상대적으로 크게 받았다. 또한, 간격이 수심보다 작곤 때는 효율이 PN에 비례해서 선형적으로 증가한 반면 그 이상에서는 효율이 상대적으로 감소하면서 비선형적으로 증가하는 현상을 밝혀냈다. 이상의 연구결과를 통해 주입공기량은 PN가 약 1000, 디퓨서 배치간격은 수심의 1.5배일 때가 최적의 성층파괴 조건인 것으로 나타났다.

The use of air diffuser system to ameliorate the reservoir by breaking stratification is now widespread. This study focuses on the hydrodynamic behavior of bubble plumes, which is the major mechanism of destratification and their combined effect of adjacent plumes on destratification efficiency. By introducing 2-phase Computational Fluid Dynamics(CFD) technique, we could suggest the optimal diffuser spacing having optimal destratification efficiency by simply analyzing the complex destratification procedures varying with the seasonal stratification intensity and bubble flow rate. Lab experiments were also carried out to verify CFD model in thermally stratified fresh water which quite differs from former researches using salts. This study showed that the mixing efficiency strongly depends on the spacing of neighboring plumes. When diffuser spacing is lower than 1.5 times the depth, the combined effect is stronger; as Plume Number(PN) is increased, the efficiency is strongly affected by spacing. If the distance is shorter than the depth of water, the efficiency increases linearly in proportion to PN. Otherwise, the efficiency increases non-linearly. These findings suggest that the combined effect should be more quantitatively taken into consideration for design and operation of air-diffuser destratification system, and recommend that the optimal destratification efficiency will be when plume number is 1000 and the spacing between neighboring diffusers is 1.5 times the depth.

키워드

참고문헌

  1. 한국수자원공사 (2000.12). 200년 수중폭기효과 분석보고서, 수도관리 67400, 2000-41
  2. Asaeda T. and Imberger J. (1989). 'Behaviors of bubble plumes in a linear stratification.' Prco. JSCE, Vol. 411, pp. 55-62 (in Japanese)
  3. Asaeda T. and Imberger J. (1993). 'Structure of Bubble Plumes in Linearly Stratified Environment.' J. Fluid MEth., Vol. 249, pp. 35-57 https://doi.org/10.1017/S0022112093001065
  4. Baines W.D. (1975). 'Entrainment by a plume or a jet at a density interface.' J. Fluid Mech, Vol. 68(2), pp. 309-320 https://doi.org/10.1017/S0022112075000821
  5. Baines W.D. and Leitch A.M. (1992). 'Destruction of stratification by bubble plume.' J. Hydraul. Engng. ASCE, Vol. 118, pp. 559-577 https://doi.org/10.1061/(ASCE)0733-9429(1992)118:4(559)
  6. Barker J. L. (1976). 'Effects of air injection at Prompton Lake.' Wayne Co, Penn. J. Res. USGS 4(1), pp. 19-25
  7. Benoit Cushman-Roisin (1994). Introduction to geo-physical fluid dynamics. Prentice Hall, Englewood Cliffs, pp. 123-134
  8. Bernhardt H. (1967) 'Aeration of wahhbach reservoir without changing the temperature profile.' J. Am Water Works Assoc., Vol. 59, pp. 266-275
  9. Bulson P. S. (1961). 'Current produced by an air curtain in deep water.' Dock Harbour Authority, Vol. 42, pp. 15-22
  10. Drury D. D., Porcella D. B. and Gearheart R. A. (1975). 'The effects of artificial destratification on the water quality and microbial populations in Hyrum reservoir.' Utah Water Res. Lab. Utah State University, Logan, Utah. PREJEW011-11
  11. Fannelop T. K., Hirshberg S. and Kuffer J. (1991). 'Surface current and recirculating cell generated by bubble curtains and jets.' J. Fluid Mech, Vol. 229, pp. 629-657 https://doi.org/10.1017/S0022112091003208
  12. Fischer H. B., Imberger J., Brooks N. H. and List E. J. (1979). Mixing in Inland and Coastal Waters. Arcademic Press, INC. (London) LTD., pp. 150-228
  13. Imteaz M. A. and Asaeda T. (2000). 'Artificial mixing of lake water by bubble plumes and effect of bubbling operations on algal bloom.' Wat. Res. 34, pp. 1919-1929 https://doi.org/10.1016/S0043-1354(99)00341-3
  14. Knoppert P.L., Rook J. J., Hofker T. and Oskam G. (1970). 'Destratification experiments at Rotterdam.' J. Am. Water Wastewater Assoc., Vol. 62, pp. 448-454
  15. Kobus K. O. (1968). 'Analysis of the flow induced by a air-bubble system.' Proc. 11th Conf. Coastal eng. London, pp. 1016-1031
  16. Kojima S. (1983). 'Aeration of impounded water.' J. of Water Reuse Technology. Vol. 8, No 4, pp. 49-53
  17. Larson M. and Jonsson L. (1996). 'Efficiency of mixing by a turbulent jet in a stably stratification fluid.' Dynamics of Atmospheres and Oceans, Vol. 24, pp. 63-74 https://doi.org/10.1016/0377-0265(95)00458-0
  18. Lorenzen M. and Mitchell R. (1973). 'Theoretical effects of artificial destratification on algal production in impoundments.' J. of Environmental Science and Technology. Vol. 7, pp. 939-944 https://doi.org/10.1021/es60082a003
  19. Malueg K., Tilstro J., Schultz D. and Powers C. F. (1971). 'The effect of induced aeration upon stratification and eutrophication process in an Oregon Farm Pond.' Proceedings of the International Symposium on Man-made Lakes, Knoxville, Tennessee
  20. McDougall T. J. (1978). 'Bubble plumes in stratified environments.' J. Fluid Mech., Vol. 85(4), pp. 655-672 https://doi.org/10.1017/S0022112078000841
  21. Milgram J. H. (1983). 'Mean flow in round bubble plumes.' J. Fluid Mech., Vol. 133, pp. 345-376 https://doi.org/10.1017/S0022112083001950
  22. Robinson E. L., Irwin W. H. and Symons J. M. (1969). 'Influence of Artificial destratification on Plankton Populations in Impoundments.' Trans. Kint. Acad. Sci. Vol. 30(12), pp. 1-18
  23. Schladow S. G. (1993). 'Lake Destratification by bubble plume systems:Design methodology.' Journal of Hydraulic Engineering, Vol. 119(3), pp. 350-368 https://doi.org/10.1061/(ASCE)0733-9429(1993)119:3(350)
  24. Stefan H. G. and Gu, R. (1992). 'Efficiency of jet-miximg of temperature - strtified water.' J. Environ. Eng., Vol 118(3), pp. 363-379 https://doi.org/10.1061/(ASCE)0733-9372(1992)118:3(363)
  25. Stephens R. and Imberger J. (1993). 'Reservoir destratification via mechanical mixers.' Journal of Hydraulic Engineering, Vol. 119(4), pp. 438-457 https://doi.org/10.1061/(ASCE)0733-9429(1993)119:4(438)
  26. Wilkinson D. (1979). 'Two-dimensional bubble plumes.' J. Hydral. Div. ASCE, Vol. 105(HY2), pp. 139-154
  27. Zic K., Stefan H. G. and Ellis C. (1992). 'Laboratory study of water destratification by a bubble plume.' J. Hydraul. Res., Vol. 30(1), pp. 7-27 https://doi.org/10.1080/00221689209498944