{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,1]],"date-time":"2026-02-01T09:52:40Z","timestamp":1769939560593,"version":"3.49.0"},"reference-count":92,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2023,12,29]],"date-time":"2023-12-29T00:00:00Z","timestamp":1703808000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China","award":["1210243"],"award-info":[{"award-number":["1210243"]}]},{"name":"National Natural Science Foundation of China","award":["52376113"],"award-info":[{"award-number":["52376113"]}]},{"name":"National Natural Science Foundation of China","award":["52176134"],"award-info":[{"award-number":["52176134"]}]},{"name":"National Natural Science Foundation of China","award":["CityU 15222421"],"award-info":[{"award-number":["CityU 15222421"]}]},{"name":"National Natural Science Foundation of China","award":["CityU 15218820"],"award-info":[{"award-number":["CityU 15218820"]}]},{"name":"Research Grants Council of the Hong Kong Special Administrative Region","award":["1210243"],"award-info":[{"award-number":["1210243"]}]},{"name":"Research Grants Council of the Hong Kong Special Administrative Region","award":["52376113"],"award-info":[{"award-number":["52376113"]}]},{"name":"Research Grants Council of the Hong Kong Special Administrative Region","award":["52176134"],"award-info":[{"award-number":["52176134"]}]},{"name":"Research Grants Council of the Hong Kong Special Administrative Region","award":["CityU 15222421"],"award-info":[{"award-number":["CityU 15222421"]}]},{"name":"Research Grants Council of the Hong Kong Special Administrative Region","award":["CityU 15218820"],"award-info":[{"award-number":["CityU 15218820"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>Binary droplet collision is a basic fluid phenomenon for many spray processes in nature and industry involving lots of discrete droplets. It exists an inherent mirror symmetry between two colliding droplets. For specific cases of the collision between two identical droplets, the head-on collision and the off-center collision, respectively, show the axisymmetric and rotational symmetry characteristics, which is useful for the simplification of droplet collision modeling. However, for more general cases of the collision between two droplets involving the disparities of size ratio, surface tension, viscosity, and self-spin motions, the axisymmetric and rotational symmetry droplet deformation and inner flow tend to be broken, leading to many distinct phenomena that cannot occur for the collision between two identical droplets owing to the mirror symmetry. This review focused on interpreting the asymmetric droplet deformation and the collision-induced internal mixing that was affected by those symmetry breaking factors, such as size ratio effects, Marangoni Effects, non-Newtonian effects, and droplet self-spin motion. It helps to understand the droplet internal mixing for hypergolic propellants in the rocket engineering and microscale droplet reactors in the biological engineering, and the modeling of droplet collision in real combustion spray processes.<\/jats:p>","DOI":"10.3390\/sym16010047","type":"journal-article","created":{"date-parts":[[2023,12,29]],"date-time":"2023-12-29T06:18:13Z","timestamp":1703830693000},"page":"47","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Symmetry-Breaking-Induced Internal Mixing Enhancement of Droplet Collision"],"prefix":"10.3390","volume":"16","author":[{"given":"Yupeng","family":"Leng","sequence":"first","affiliation":[{"name":"Institute for Energy Research, Jiangsu University, Zhenjiang 212013, China"},{"name":"School of Water, Energy, and Environment, Cranfield University, Cranfield MK43 0AL, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chengming","family":"He","sequence":"additional","affiliation":[{"name":"Institute for Energy Research, Jiangsu University, Zhenjiang 212013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qian","family":"Wang","sequence":"additional","affiliation":[{"name":"Institute for Energy Research, Jiangsu University, Zhenjiang 212013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhixia","family":"He","sequence":"additional","affiliation":[{"name":"Institute for Energy Research, Jiangsu University, Zhenjiang 212013, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8865-9138","authenticated-orcid":false,"given":"Nigel","family":"Simms","sequence":"additional","affiliation":[{"name":"School of Water, Energy, and Environment, Cranfield University, Cranfield MK43 0AL, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peng","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon 999077, Hong Kong"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,12,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1607","DOI":"10.1175\/1520-0469(1982)039<1607:CCABOR>2.0.CO;2","article-title":"coalescence and breakup of raindrops. 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