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1. Stop, DROP, and ROA: effectiveness of defenses through the lens of DROP

   https://doi.org/10.1145/3517745.3561454  

   Oliver, Leo; Akiwate, Gautam; Luckie, Matthew; Du, Ben; claffy, kc (October 2022, ACM Internet Measurement Conference (IMC))
2. The elastic Rayleigh drop

   https://doi.org/10.1039/C9SM01753D  

   Tamim, S. I.; Bostwick, J. B. (November 2019, Soft Matter)

   Bioprinting technologies rely on the formation of soft gel drops for printing tissue scaffolds and the dynamics of these drops can affect the process. A model is developed to describe the oscillations of a spherical gel drop with finite shear modulus, whose interface is held by surface tension. The governing elastodynamic equations are derived and a solution is constructed using displacement potentials decomposed into a spherical harmonic basis. The resulting nonlinear characteristic equation depends upon two dimensionless numbers, elastocapillary and compressibility, and admits two types of solutions, (i) spheroidal (or shape change) modes and (ii) torsional (rotational) modes. The torsional modes are unaffected by capillarity, whereas the frequency of shape oscillations depend upon both the elastocapillary and compressibility numbers. Two asymptotic dispersion relationships are derived and the limiting cases of the inviscid Rayleigh drop and elastic globe are recovered. For a fixed polar wavenumber, there exists an infinity of radial modes that each transition from an elasticity wave to a capillary wave upon increasing the elastocapillary number. At the transition, there is a qualitative change in the deformation field and a set of recirculation vortices develop at the free surface. Two special modes that concern volume oscillations and translational motion are characterized. A new instability is documented that reflects the balance between surface tension and compressibility effects due to the elasticity of the drop. 

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3. Drop-by-Drop Radar Cross Section Calculations for Sand C-band Weather Radar Frequencies

   https://doi.org/10.23919/EuCAP53622.2022.9768966  

   Teschl, Franz; Thurai, Merhala; Steger, Sophie; Schonhuber, Michael (March 2022, 16th European Conference on Antennas and Propagation (EuCAP))

   Recent studies revealed that scattering calculations at weather radar frequencies using individual drop shapes result in better agreement between simulated and measured polarimetric weather radar parameters, than if established rotational symmetric shape models are used. In the present work, thousands of individual rain drops that were detected with a 2D Video Disdrometer during a tropical storm, were reconstructed and their individual radar cross sections (RCS) were calculated by automatizing a commercial EM solver software. The calculations were carried out at the common weather radar frequencies at 2.8 GHz and 5.625 GHz, both for horizontal and vertical polarization. It is evaluated to what extend the RCS can differ for drops with an equal volume, it is discussed how the scattering parameters of individual drops scale within S- and C-band frequencies, and it is shown for one sample drop what effect the modelling granularity has on determined radar cross section values. 

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4. Statistics of Jet Drop Production

   https://doi.org/10.1029/2021GL092919  

   Berny, A.; Popinet, S.; Séon, T.; Deike, L. (May 2021, Geophysical Research Letters)
5. Light-Induced Polymer Drop Splashing

   https://doi.org/10.1021/acs.langmuir.1c03288  

   Upoma, Marufa A; Tran, Huy; Rose, Cason; Ayorinde, Taiwo; Sayes, Christie M; Pack, Min Y (June 2025, Langmuir)

   This study seeks to understand the role of photodegradation of aqueous polymers in drop splashing. Polymer drop impact commonly occurs in various industrial applications such as inkjet printing, spray coating, and agrochemical sprays. In agrochemicals, the various constituent components (e.g., adjuvants) imparts multiple changes to the fluid dynamics and the wetting behaviors of the drops, as well as interacting with the environmental conditions. The environmental conditions (e.g., thermal-degradation, photo-degradation, and oxidation) of the chemicals affect the shelf stability of the intended physicochemical properties of the chemicals, which are added to stabilize drift from the spray nozzles and minimize drop bouncing from leaves. The aging effects of the adjuvants in tandem with the already low pesticide delivery efficiency has an unknown effect on the agrochemical delivery efficiency and the related environmental burden from the increased run off. Herein, we systematically photo-degraded polyethylene oxide (PEO) to probe the drop splashing behavior as a result of the simulated aging conditions. Dye was added to accelerate the degradation of the polymers and caused drops to splash at Weber numbers where the pure PEO case did not, confirming the need to consider environmental factors which contributes to adjuvant aging in agrochemical applications. We have also conducted experiments with various concentrations of PEO to probe the changes in the splash dynamics as well as including surfactants, which played a marginal role in altering the splash dynamics under our parameter space. The significance of the study is that the degradation of the polymers influences the splashing and increases the amount of splashed droplets, indicating the importance of controlling the environmental conditions under which polymer solutions are stored. 

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