Installation for measuring the distributions of volume concentrations of aerosol droplets by size based on the shadow method and its calibration procedure

For Russian citation (Opticheskii Zhurnal):

Сергеев Д.А., Краев И.М. Установка для измерения распределений объёмных концентраций капель аэрозоля по размерам на основе теневого метода и методика её калибровки // Оптический журнал. 2024. Т. 91. № 4. С. 40–49. http://doi.org/10.17586/1023-5086-2024-91-04-40-49

Sergeev D.A., Krayev I.M. Installation for measuring the distributions of volume concentrations of aerosol droplets by size based on the shadow method and its calibration procedure [in Russian] // Opticheskii Zhurnal. 2024. V. 91. № 4. P. 40–49. http://doi.org/10.17586/1023-5086-2024-91-04-40-49

For citation (Journal of Optical Technology):

Abstract:

The subject of study is the measurements of size distributions of spray concentrations induced in a laboratory experiment during the interaction of an air flow with a free water surface (simulation of the interaction of the atmosphere and hydrosphere) by optical methods. The aim of study is the development of a model of a system for measuring the distribution of volume concentrations of aerosol droplets by size based on the shadow imaging method and its calibration techniques. Method. A shadow method with high-speed video recording of a side view of an air flow with drops moving in it over a rough water surface with powerful diode illumination from the opposite side was used. A feature of these measurements is that the width of the region of detection of such a system perpendicular to the plane of filming depends on the focusing depth. Therefore, a special calibration system completely reproducing the optical path as in the flume, but with glass microspheres of a known size instead of drops was developed. Main results. The calibration system made it possible to obtain the dependence of the size of the measurement area across the image on the size of the detected drop. This dependence was used to correctly recalculate the distributions of the number of drops in the image plane into volume concentrations during the measurements in laboratory experiments on modeling of the wind-wave interaction in the Thermostratified Wind-Wave Tank (TsWiWaT) of the IAP RAS. The lower limit on the radius of 50 µm is the minimum among the results of similar studies using the shadow methods obtained to date. Practical significance. The proposed method of calibration/measurement by shadow visualization makes it possible to obtain data on the distribution of spray concentrations by size, which are necessary for the development of physical models that qualitatively and quantitatively describe the processes of interaction between the atmosphere and the hydrosphere in a wide range of conditions (storms and hurricanes).

Keywords:

shadow method, high speed video recording, spray, wind, waves, laboratory modeling

Acknowledgements:

the work was supported by the RGNF grant № 23-77-10060. The work of I.M. Krayev was supported within the state task of IAP RAS № 0030-2022-0005. The experiments were carried out on the equipment of a unique scientific installation "Complex of large-scale geophysical stands" of the IPF RAS

OCIS codes: 100.0100

References:

Fairall C.W., Kepert J., Holland G. The effect of sea spray on surface energy transports over the ocean // Global Atmos. Ocean Syst. 1994. V. 2. P. 121–142. https://doi.org/10.1175/JCLI-D-21-0608.1
Andreas E.L. A review of the sea spray generation function for the open ocean. In Atmosphere–ocean interactions. V. 1 (eds W.A. Perrie). Southampton, UK.: WIT Press, 2002. P. 1–46.
Veron F. Ocean spray // Annu. Rev. Fluid Mech. 2015. V. 47. P. 507–538. https://doi.org/10.1146/annurev-fluid-010814-014651
Wang C.S., Street R.L. Transfers across an air-water interface at high wind speeds the effect of spray // J. Geophys Res. 1978. V. 8. № 3. P. 2959–2969.
Lai R.J., Shemdin O.H. Laboratory study of the ge-neration of spray over water // J. Geophys. Res. 1974. V. 79. P. 3055–3063.
Fairall C.W., Banner M.L., Peirson W.L., Asher W., Morison R.P. Investigation of the physical scaling of sea spray spume droplet production // J. of Geophys. Res. 2009. V. 114. C10001. https://doi.org//10.1029/2008JC004918
Ortiz-Suslow D.G., Haus B.K., Mehta S., Laxague N.J. Sea spray generation in very high winds // J. Atmos. Sci. 2016. V. 73. P. 3975–3995. https://doi.org/10.1175/JAS-D-15-0249.1
Troitskaya Y., Kandaurov A., Ermakova O., Kozlov D., Sergeev D., Zilitinkevich S. Bag-breakup fragmentation as the dominant mechanism of sea-spray production in high winds // Sci. Rep. 2017. V. 7. P. 1614. https://doi.org/10.1038/s41598- 017-01673-9
Veron F., Hopkins C., Harrison E.L., Mueller J.A. Sea spray spume droplet production in high wind speeds // Geophys. Res. Lett. 2012. V. 39. L16602. https://doi.org/10.1029/2012GL052603
Anguelova M., Barber R.P., Wu J. Spume drops produced by the wind tearing of wave crests // J. Phys. Oceanogr. 1999. V. 29. P. 1156–1165. https://doi.org/10.1175/1520-0485(1999)029<1156:SDPBTW>2.0.CO;2
Medennikov P.A. Algorithm for detecting and determining the coordinates of a point object // Journal of Optical Technology. 2019. V. 86. № 8. P. 510–514. https://doi.org/10.1364/JOT.86.000510
Medennikov P.A., Pavlov N.I. Detection and tracking of weakly emitting point objects based on the analysis of a sequence of miniseries of images // Journal of Optical Technology. 2021. V. 88. № 12. P. 716–721. https://doi.org/10.1364/JOT.88.000716
Troitskaya Y., Kandaurov A., Ermakova O., Kozlov D., Sergeev D., Zilitinkevich S. The ‘Bag Breakup’ spume droplet generation mechanism at high winds. Part I: Spray generation function // J. Phys. Oceanogr. 2018. V. 48. № 9. P. 2167–2188. https://doi.org/10.1175/JPO-D-17-0104.1