Ejection of marine microplastics by raindrops: a computational and experimental study

Microplastics and Nanoplastics

Table 1 Terminal velocity curve for raindrops at mean sea level pressure [29]

d/mm	\(u/\frac {\mathrm {m}}{\mathrm {s}}\)	Re	We	Fr	Ca	Bo
1	4.50	4282	281	45.4	0.0657	0.136
2	6.80	12943	1284	48.6	0.0992	0.545
3	8.10	23125	2733	47.2	0.1182	1.226
4	8.80	33498	4301	44.4	0.1284	2.179
5	9.20	43776	5876	41.5	0.1342	3.405
6	9.40	53673	7361	38.8	0.1371	4.903
7	9.55	63618	8864	36.4	0.1393	6.674

The terminal velocity u is a function of the drop diameter d. The dimensionless numbers Reynolds \({Re}=\frac {d u}{\nu }\), Weber \({We}=\frac {d u^{2} \rho }{\sigma }\), Froude \({Fr}=\frac {u}{\sqrt {d g}}\), Capillary \({Ca}=\frac {u \rho \nu }{\sigma }\) and Bond \({Bo}=\frac {d^{2} \rho g}{\sigma }\) are also given