Breakup of a surfactant-laden drop in a continuous air jet stream
Sumit Joshi  1, *@  , Sushrut Ranade  1, *@  , Anand T N C  1, *@  
1 : Indian Institute of Technology Madras
Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu -  India
* : Corresponding author

The breakup of a surfactant-laden drop occurs in various practical applications (crop spraying, sprays for cleaning, sprays for body and hair care). In this study, we investigate the breakup behaviour of such a drop in a continuous air jet stream. A solution of sodium lauryl sulfate (SLS) in water was used as a test liquid. The range of Weber numbers employed was 19.8-72.4. We observed bag breakup, bag-stamen breakup, dual-bag breakup and sheet-thinning breakup. A few important parameters such as stream-wise length and cross-stream length of the drop, the time at which the first instance of breakup is observed, and the displacement of the drop centroid were measured. Two approaches to obtain the velocity and acceleration of the drop from the centroid displacement data are discussed: central difference approximations and polynomial fitting using the ridge regression. Finally, the coefficient of drag of the drop at different Weber numbers, calculated using the velocity and acceleration data (obtained by employing both the approaches), is compared.

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