橫向流對射流影響之實驗及數值模擬

以作者查詢圖書館館藏

、以作者查詢臺灣博碩士

、以作者查詢全國書目

、勘誤回報

、線上人數：38

、訪客IP：18.190.156.214

姓名

陳奕丞(Yi-Cheng Chen) 查詢紙本館藏

畢業系所

土木工程學系

論文名稱

橫向流對射流影響之實驗及數值模擬
(Laboratory Experiments and Numerical Simulation of Droplet Jets under Cross Wind)

相關論文

★ 定剪力流中二維平板尾流之風洞實驗	★ 以大渦紊流模式模擬不同流況對二維方柱尾流之影響
★ 矩形建築物高寬比對其周遭風場影響之研究	★ 台灣地區風速機率分佈之研究
★ 邊界層中雙棟並排矩形建築之表面風壓量測	★ 排放角度與邊牆效應對浮昇射流影響之實驗研究
★ 低層建築物表面風壓之實驗研究	★ 圓柱體形建築物表面風壓之實驗研究
★ 最大熵值理論在紊流剪力流上之應用	★ 應用遺傳演算法探討海洋放流管之優化方案
★ 均勻流中圓柱體形建築物表面風壓之風洞實驗	★ 大氣與森林之間紊流流場之風洞實驗
★ 以歐氏-拉氏法模擬煙流粒子在建築物尾流區中的擴散	★ 以HHT分析法研究陣風風場中建築物之表面風壓
★ 以HHT時頻分析法研究陣風風場中物體所受之風力	★ 風吹落物之軌跡預測模式與實驗研究

檔案

[Endnote RIS 格式]

[Bibtex 格式]

[相關文章]

[文章引用]

[完整記錄]

[館藏目錄]

至系統瀏覽論文 (2026-8-1以後開放)

摘要(中)

在新冠病毒（COVID-19）疫情大流行的背景下，了解病原體在空氣中的傳播行為對於控制流行病至關重要。本研究的目的是通過實驗和數值模擬的方法，探討橫向流對射流中液滴分布和傳播的影響。我們藉由風洞實驗和大渦流模擬（LES）模式，針對不同風速和風向下射流的速度場和濃度場進行了研究。實驗在國立中央大學的風洞設施中進行，使用了不同的橫向流速度和射流速度，並測量了不同位置的射流速度和液滴濃度。模擬結果與實驗數據比對驗證，顯示出良好的一致性。研究結果表明，橫向流的存在顯著影響射流中的液滴濃度分布，在相同距離處(s/D ≈ 10)濃度約為無橫向流的37%。較大的液滴(dp ≥ 100 μm)由於慣性作用，受橫向流的影響較小，沿射流方向保持較高的濃度；而較小的液滴(dp ≤ 10 μm)則更容易被橫向流的影響，分散範圍更廣，相同距離處(s/D ≈ 10D)，粒徑dp = 10 μm的濃度，約為粒徑dp = 100 μm的25%。實驗和模擬還顯示了射流與橫向流之間的複雜相互作用，特別是在非平行風向下，射流出現了分叉現象，形成了雙峰分布。這些結果對噴嚏中液滴和氣溶膠的傳播行為，提供了深入的理解和應用價值。

摘要(英)

In the context of the COVID-19 pandemic, understanding the transmission behavior of pathogens in the air is crucial for controlling epidemics. This study aims to explore the impact of crosswind on droplet dispersion in sneeze-induced jet flows through experimental and numerical simulations. The laboratory experiments were performed in the wind tunnel facility of National Central University, and the jet velocities and droplet concentrations were measured under various wind speeds and directions. The experimental results are used to validate the simulation of a Large Eddy Simulation (LES) model. The crossflow could reduced the droplet concentration of the jet flow about 37% at the same distance (s/D ≈ 10). The simulation results indicate that the larger droplets (dp ≥ 100 μm) due to their inertia, are less likely to be influenced by the crosswind and maintain higher concentrations along the jet direction. Whereas smaller droplets (dp ≤ 10 μm) are easier to be carried by the crosswind, resulting in a wider dispersion and lower concentration. The particle concentration for with a diameter dp = 10 μm is approximately 25% (s/D ≈ 10) of that for the particles with a diameter dp = 100 μm. The numerical simulations also reveal the complex interactions between jet flows and crosswind, particularly under non-parallel wind directions, where the jet flow bifurcates, forming a twin-peak concentration distribution. These findings provide valuable insights into the behavior of droplets in jet flows under crosswind conditions.

關鍵字(中)

★ 噴嚏
★ 射流
★ 橫向風
★ 液滴
★ 氣懸膠
★ 計算流體力學

關鍵字(英)

★ Sneeze
★ jet flow
★ cross wind
★ droplet
★ aerosol
★ Computation Fluid Dynamics

論文目次

摘要 I
Abstract II
Table Captions: V
Figure Captions: VI
Chapter 1 Introduction 1
Chapter 2 Numerical Model 10
2.1 Governing equations 10
Chapter 3 Model Validation 15
3.1 Experimental setup 15
3.1.1 Velocity measurement 16
3.1.2 Concentration measurement 17
3.2 Numerical simulation 19
3.2.1 Boundary condition 20
3.2.2 Simulated Aerosol Concentration 21
3.3 Validation 22
Chapter 4 Results and Discussion 26
4.1 Particle diameter 26
4.2 Jet Velocity 28
4.3 Wind direction 30
Chapter 5 Conclusions 32
Reference 34

參考文獻

1. A.D. Gosman, and E. Ioannides, (1983). Aspects of computer-simulation of liquid-fueled combustors, J. Energy 7 (6) 482-490.
2. Amamou, A., Habli, S., Saïd, N. M., Bournot, P., and Le Palec, G. (2015). Numerical study of turbulent round jet in a uniform counterflow using a second order Reynolds stress model. Journal of Hydro-environment Research, 9(4), 482-495.
3. Ball, C.G., Fellouah, H. and Pollard, A., (2012). The flow field in turbulent round free jets. Progress in Aerospace Sciences, 50, pp.1-26.
4. Boersma, B. J., Brethouwer, G., and Nieuwstadt, F. T. (1998). A numerical investigation on the effect of the inflow conditions on the self-similar region of a round jet. Physics of Fluids, 10(4), 899-909.
5. Bourouiba, L., Dehandschoewercker, E., and Bush, J. W. M., (2014).“Violent expiratory events: On coughing and sneezing,” J. Fluid Mech. 745, 537–563.
6. Busco, G., Yang, S. R., Seo, J., and Hassan, Y. A. (2020). Sneezing and asymptomatic virus transmission. Physics of Fluids, 32(7) 073309. Doi:10.1063/5.0019090.
7. C.Y.H. Chao, and M.P. Wan, (2006). A study of the dispersion of expiratory aerosols in unidirectional downward and ceiling-return type airflows using a multiphase approach, Indoor Air 16(4) 296-312.
8. Chao, C.Y.H., Wan, M.P., Morawska, L., Johnson, G.R., Ristovski, Z.D., Hargreaves, M., Mengersen, K., Corbett, S., Li, Y., Xie, X., Katoshevski, D., (2009). Characterization of expiration air jets and droplet size distributions immediately at the mouth opening. Journal of Aerosol Science, 40(2), pp.122-133.
9. Dbouk, T. and Drikakis, D., (2020). On coughing and airborne droplet transmission to humans. Physics of Fluids, 32(5). 053310.
10. Deardorff, J. W. (1970). A numerical study of three-dimensional turbulent channel flow at large Reynolds numbers. J. Fluid Mech., 41(2), 453-480.
11. Feng, Y., Marchal, T., Sperry, T. and Yi, H., 2020. Influence of wind and relative humidity on the social distancing effectiveness to prevent COVID-19 airborne transmission: A numerical study. Journal of Aerosol Science, 147, 105585.
12. Gupta, J. K., Lin, C. H., and Chen, Q. (2010). Characterizing exhaled airflow from breathing and talking. Indoor Air, 20(1), 31-39.
13. Gupta, J. K., Lin, C.-H., Chen, Q., (2009). Flow dynamics and characterization of a cough. Indoor Air, 19(6), 517–525.
14. Han, M., Ooka, R., Kikumoto, H., Oh, W., Bu, Y. and Hu, S., (2021). Measurements of exhaled airflow velocity through human coughs using particle image velocimetry. Building and Environment, 202, 108020.
15. Han, Z. Y., Weng, W. G., and Huang, Q. Y. (2013). Characterizations of particle size distribution of the droplets exhaled by sneeze. J. Royal Soc. Interface, 10(88), 20130560.
16. Höppe, P. (1981). Temperatures of expired air under varying climatic conditions. Intern. Journal of Biometeorology, 25, 127-132.
17. Huq, P., & Dhanak, M. R. (1996). The bifurcation of circular jets in crossflow. Physics of Fluids, 8(3), 754-763.
18. Hussein, H. J. Capp, S. P. and George, W. K. ‘‘Velocity measurements in a high Reynolds number, momentum-conserving axisymmetric turbulent jet,’’ J. Fluid Mech. 258, 31 ~1994.
19. Johnson, G. R. and Morawska, L., (2009). “The mechanism of breath aerosol formation,” J. Aerosol Med. Pulmonary Drug Delivery 22(3), 229–237.
20. Kelso, R.M., Lim, T.T. and Perry, A.E., 1996. An experimental study of round jets in cross-flow. J. Fluid Mech., 306, pp.111-144.
21. Lee, J.H.W. and P. Neville-Jones, (1987). “Initial dilution of horizontal jet in crossflow”, J. of Hydraulic Eng., 113 (5), 615-629.
22. Lee, J.H.W. and V. Cheung, (1990). “Generalized Lagrangian model for buoyant jets in current”, J. of Environmental Eng. 116, (6), 1085-1106
23. Lee, Y. C., Chang, T. J., and Hsieh, C. I. (2018). A numerical study of the temperature reduction by water spray systems within urban street Canyons. Sustainability, 10(4), 1190.
24. Li, A. and Ahmadi, G. (1992). Dispersion and Deposition of Spherical Particles from Point Sources in a Turbulent Channel Flow. Aerosol Science and Technology, 16:209-226.
25. List, E.J. (1982). Turbulent jets and plumes, Ann. Rev. Fluid Mech., 14, 189-212.
26. Mendez-Diaz, M.M. and G.H. Jirka (1996). “Buoyant plumes from multiport diffuser discharge in deep co-flowing water”, J. of Hydraulic Eng. 122 (8), 428-435.
27. Morsi, S. A. and Alexander, A. J. (1972). An investigation of particle trajectories in two-phase flow systems. J. Fluid Mech., 55(2):193-208.
28. Nicas, M., Nazaroff, W. W. and Hubbard, A. (2005). Toward understanding the risk of secondary airborne infection: Emission of respirable pathogens, Journal of Occupational and Environmental Hygiene, 2(3), 143-154.
29. Olmedo, I., Nielsen, P. V., Ruiz de Adana, M., Jensen, R. L., and Grzelecki, P. (2012). Distribution of exhaled contaminants and personal exposure in a room using three different air distribution strategies. Indoor Air, 22(1), 64-76.
30. Pendar, M.-R. and Páscoa, J.C., (2020). Numerical modeling of the distribution of virus-carrying saliva droplets during sneeze and cough. Physics of Fluids, 32(8). 083305.
31. Rajaratnam, N. (1976). Turbulent Jets. Elsevier Publishing Co., Amsterdam, Netherlands.
32. Saffman, P. G. (1965). The lift on a small sphere in a slow shear flow. J. Fluid Mech., 22:385-400.
33. Sagaut, P. (2005). Large Eddy Simulation for Incompressible Flows: An Introduction. Springer, Berlin, Germany.
34. Tellier, R. (2006). Review of aerosol transmission of influenza A virus. Emerg. Infect. Dis. 12(11), 1657–1662. doi:10.3201/eid1211.060426.
35. Villafruela, J. M., Olmedo, I., De Adana, M. R., Méndez, C., and Nielsen, P. V. (2013). CFD analysis of the human exhalation flow using different boundary conditions and ventilation strategies. Building and Environment, 62, 191-200.
36. Wei, J. and Li, Y., (2015). Enhanced spread of expiratory droplets by turbulence in a cough jet. Building and Environment, 93(2), pp.86-96.
37. Wright, S.J. (1977) “Mean behavior of buoyant jets in a crossflow”, J. Hydraulics Div., 103 (5), 499-513.
38. Xie, X., Y. Li, H. Sun, and L. Liu, (2009). “Exhaled droplets due to talking and coughing,” J. Royal Soc. Interface, 6, 703–714.
39. Yang, S., Lee, G.W., Chen, C.M., Wu, C.C. and Yu, K.P., 2007. The size and concentration of droplets generated by coughing in human subjects. Journal of Aerosol Medicine, 20(4), pp.484-494.
40. Yuan, L.L., Street, R.L. and Ferziger, J.H., 1999. Large-eddy simulations of a round jet in crossflow. J. Fluid Mech., 379, pp.71-104.
41. Zhang, H., Li, Y., Xiao, J., and Jordan, T. (2018). Large eddy simulations of the all-speed turbulent jet flow using 3-D CFD code GASFLOW-MPI. Nuclear Engineering and Design, 328, 134-144.
42. Zhiyin, Y. (2015). Large-eddy simulation: Past, present and the future. Chinese Journal of Aeronautics, 28(1), 11-24.
43. Zhu, S., Kato, S. and Yang, J.H. (2006). Study on transport characteristics of saliva droplets produced by coughing in a calm indoor environment, Building and Environment, (41)12, 1691-1702.

指導教授

朱佳仁(Chia-Ren Chu)

審核日期

2024-7-30

推文