Journal of Korea Water Resources Association (한국수자원학회논문집)

Korea Water Resources Association (한국수자원학회)
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Performance test of flow straightener with multiple parallel tubes

다중병렬관를 이용한 흐름 정류장치의 성능 평가

  • Seonwoo, Jaebin (Department of Civil and Environmental Engineering, Gangneung-Wonju National University) ;
  • Shin, Hongjoon (Central Research Institute, Korea Hydro & Nuclear Co. Ltd) ;
  • Paik, Joongcheol (Department of Civil and Environmental Engineering, Gangneung-Wonju National University)
  • 선우재빈 (강릉원주대학교 대학원 토목공학과) ;
  • 신홍준 (한국수력원자력(주) 중앙연구원) ;
  • 백중철 (강릉원주대학교 건설환경공학과)
  • Received : 2024.08.20
  • Accepted : 2024.09.25
  • Published : 2024.10.31
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Abstract

Providing a uniform velocity distribution at the inlet of the experimental flume through removing eddies, air bubbles, swirling flow and excessive velocity fluctuations as quickly and efficiently as possible is very important for the accurate reproduction and measurement of both flow velocity and phenomenon in the test reach. In this study, the flow straightener (FS) using multiple parallel PC (ploycarbonate) tubes was developed to increase the accuracy of flow measurement by quickly eliminating excessive velocity fluctuations and air bubbles. It was confirmed through a series of hydraulic experiments that FS using PC tubes can reduce the turbulence intensity (TI) by nearly half under all experimental configurations. The FS of PC tubes with a diameter of 20 mm and a length of 0.3 m can reduce the TI by more than 60% and the value can be maintained at about 2.4% that is in common at the inlet cross-section of the experimental flume. When the tube length is 0.3 m, the magnitude of TI decreases linearly as the tube diameter decreases, and it is desirable to keep the tube diameter at 20 mm to provide a definite flow conditioning effect. Small air bubbles formed at high flow conditions are found to grow in size and quickly rise to the free surface at the rising velocity of about 0.24 m/s due to increased buoyancy as they pass through the tubes. The removal function of air bubbles was not sensitive to the diameter and length of the PC tubes.

실험 개수로의 유입단면에서 와, 공기방울, 소용돌이 흐름 및 과도한 유속 변동을 가능한 짧은 구간에서 효율적으로 제거하여 균일한 유속분포를 제공하는 것은 시험구간에서의 정확한 유속 측정과 흐름 현상 재현에 매우 중요하다. 이 연구에서는 과도한 유속 변동과 공기방울을 빠르게 제어함으로써 흐름 측정의 정확도를 높이기 위해 다중병렬관을 이용한 정류장치를 개발하였다. 개발한 정류장치 장치의 흐름 안정화 성능을 수리 실험을 통해 확인하였다. 다중병렬관을 이용한 정류장치는 모든 실험 조건에서 유속 변동의 지표인 난류강도를 절반 가까이 줄일 수 있는 것으로 나타났다. 직경이 20 mm이고 길이가 0.3 m인 정류관을 사용할 때 난류강도를 약 60% 이상 감소시켜 일반적인 실험수로 유입단면에서의 난류강도인 약 2.4%의 값을 유지할 수 있는 것으로 나타났다. 관의 길이가 0.3 m인 경우 난류강도의 크기는 관의 직경을 감소시킴에 따라 선형적으로 분명하게 감소하였다. 일반적인 실험실 규모 조건에서 확실한 정류 효과를 확보하기 위해서는 정류관의 직경을 20 mm로 유지하는 것이 적합한 것으로 나타났다. 고유량 조건에서 발생하는 작은 공기방울은 다중병렬관을 통과하면서 크기가 커짐에 따라 증가한 부력에 의해 약 0.24 m/s의 속도로 빠르게 수면으로 상승하여 제거 되었다. 정류장치의 공기방울 제거 성능은 정류관의 직경과 길이에 민감하지 않은 것으로 나타났다.

Keywords

Acknowledgement

이 연구는 한국수력원자력(주)에서 재원을 부담하여 국립강릉원주대학교에서 수행한 연구결과입니다(22-개념-신재-15).

References

  1. Burley, R.R., and Harrington, D.E. (1987). Experimental evaluation of honeycomb/screen configurations and short contraction section for NASA Lewis Research Center's altitude wind tunnel. NASA Technical Paper 2692, NASA Lewis Research Center, Cleveland, OH, U.S.
  2. Cho, Y.-M. (2005). "Improvement of rectangle sedimentation basin using the moving baffle." Journal of Korean Society of Environmental Engineers, Vol. 27, No. 7, pp. 726-731.
  3. Damiola, L., Siddiqui, M.F., Runacres, M.C., and De Troyer, T. (2023). "Influence of free-stream turbulence intensity on static and dynamic stall of a NACA 0018 aerofoil." Journal of Wind Engineering & Industrial Aerodynamics, Vol. 232, 105270. doi: 10.1016/j.jweia.2022.105270.
  4. Godlieb, W., Gorter, S., Deen, N.G., Kuipers, J.A.M. (2011). "Experimental study of large scale fluidized beds at elevated pressure." Industrial & Engineering Chemistry Research, Vol. 51, No. 4, pp. 1962-1969.
  5. Howes, D.J., Burt, C.M., and Snaders, B.F. (2009). "Flow conditioner design for improving open channel flow measurement accuracy from a Sontek-Argonaut-SW." Proceedings of the 5th International Conference on Irrigation and Drainage, US Committee on Irrigation and Drainage, Salt Lake City, UT, U.S., pp. 117-126.
  6. Hussein, H.J., and Martinuzzi, R.J. (1996). "Energy balance for turbulent flow around a surface mounted cube placed in a channel." Physics of Fluids, Vol. 8, pp. 764-780.
  7. Liu, R., and Ting, D.S.-K. (2007). "Turbulent flow downstream of a perforated plate: Sharp-edged orifice versus finite-thickness holes." Journal of Fluid Engineering, Vol. 129, No. 9, pp. 1164-1171.
  8. Mendelson, H.D. (1967). "The prediction of bubble terminal velocity from wave theory." AlChE Journal, Vol. 13, No. 2, pp. 250-253.
  9. Nakagawa, H., and Nezu, I. (1987). "Experimental investigation on turbulent structure of backward-facing step flow in an open channel." Journal of Hydraulic Research, Vol. 25, No. 1. pp. 67-88.
  10. Nezu, I. (2005). "Open-channel flow turbulence and its research prospect in the 21st century." Journal of Hydraulic Engineering, Vol. 131, No. 4, pp. 229-246.
  11. Nino, Y., Lopez, F., and Garcia, M. (2003). "Threshold for particle entrainment into suspension." Sedimentology, Vol. 50. pp. 247-263.
  12. Ouazzane, K., and Benhadj, R. (2007). "An experimental investigation and design of flow-conditioning devices for orifice metering." Proceeding of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Vol. 221, No. 3, pp. 281-291. doi: 10.1243/0954406JMES382.
  13. Park, S.W., and Lee S.W. (2000). "An experimental study on the flow stabilization in the downstream region of a butterfly-type valve." Transactions of the Korea Society of Mechanical Engineering B, Vol. 24, No.11, pp. 1417-1427.
  14. Seo, Y. (2013). "Effect of hydraulic diameter of flow straighteners on turbulence intensity in square wind tunnel." HVAC&R Research, Vol. 19, No. 2, pp. 141-147.
  15. Song, J., Liu, D. Ma, J., and Chen, X. (2018). "Effect of elevated pressure on bubble properties in a two-dimensional gas-solid fluidized bed." Chemical Engineering Research and Design, Vol. 138, pp. 21-31.
  16. Spearman, E.P., Sattary, J.A., and Reader-Harris, M.J. (1996). "Comparison of velocity and turbulence profiles downstream of perforated plate flow conditioners." Flow Measurement and Instrumentation, Vol. 7, No. 3-4, pp. 181-199.
  17. Street, R.L., Watters, G.Z., and Vennard, J.K. (1998). Elementary fluid mechanics. 7th Edition, John Wiley & Sons, Inc., New York, NY, U.S., pp. 380-381.
  18. Wallis, G.B. (1974). "The terminal speed of single drops or bubbles in an infinite medium." International Journal of Multiphase Flow, Vol. 1, pp. 491-511.
  19. Xiang, Q.-J., Xue, L., Kim, K.-Y., and Shi, Z.-F. (2019). "Multi-objective optimization of a flow straightener in a large capacity firefighting water cannon." Journal of Hydrodynamics, Vol. 31, No. 1, pp. 137-144.
  20. Xiong, W., Kalkuhler, K., and Merzkirch, W. (2003). "Velocity and turbulence measurements downstream of flow conditioners." Flow Measurement and Instrumentation, Vol. 14, No. 6. pp. 249-260.