%0 Conference Paper %1 Ibach2023ILASS23 %A Ibach, Matthias %A Vaikuntanathan, Visakh %A Arad, ALumah %A Katoshevski, David %A Greenberg, Barry %A Weigand, Bernhard %D 2023 %K EXC2075 PN1 PN1-2(II) PN1-2B misc %T Numerical Study of Oscillating Droplets and their Relevance to Grouping in Streams %X The tendency of initially separated droplets to convene, named droplet grouping, is relevant in many technical applications, such as 3D ink-jet printing, medical inhalators and spray coating. Recent comparison of numerical studies to experimental data has shown that droplet shape deformation and subsequent oscillation can have a significant influence on the grouping time in droplet streams [1, 2]. Therefore, this study aims at numerically investigating the effect of non-spherical droplet shapes and oscillation on droplet dynamics and grouping behavior in monodisperse droplet streams for two relevant stages: 1) at the initial stage after breakup of the liquid jet into a stream of distinct droplets and 2) after the approach and coalescence of droplets within the stream. The simulations are performed with the in-house multiphase flow solver Free Surface 3D (FS3D) based on the Volume-of-Fluid (VOF) method, which solves the incompressible Navier-Stokes equations via direct numerical simulation (DNS). The evolution of the dominant oscillation mode and the damping rate for single, translating droplets as well as the effect of nearby droplets in the stream is compared with an analytical solution. Time until grouping in the first and subsequent grouping behavior in the second considered stage are examined for varying initial deviation from a spherical droplet and different initial Reynolds numbers. The study shows that shape oscillation resulting from sufficient deformation tends to expedite grouping processes in the stage after breakup of the liquid jet, decreasing time until grouping up to 33 % for a Reynolds number of 500. The coalescence in the grouping process within the second stage also induces stretching of the droplets. The influence on follow-up grouping after droplet coalescence in streams is found to be minor, since in this case time scales of the damping of the oscillation are small compared to characteristic times for the grouping process itself.

@inproceedings{Ibach2023ILASS23, abstract = {The tendency of initially separated droplets to convene, named droplet grouping, is relevant in many technical applications, such as 3D ink-jet printing, medical inhalators and spray coating. Recent comparison of numerical studies to experimental data has shown that droplet shape deformation and subsequent oscillation can have a significant influence on the grouping time in droplet streams [1, 2]. Therefore, this study aims at numerically investigating the effect of non-spherical droplet shapes and oscillation on droplet dynamics and grouping behavior in monodisperse droplet streams for two relevant stages: 1) at the initial stage after breakup of the liquid jet into a stream of distinct droplets and 2) after the approach and coalescence of droplets within the stream. The simulations are performed with the in-house multiphase flow solver Free Surface 3D (FS3D) based on the Volume-of-Fluid (VOF) method, which solves the incompressible Navier-Stokes equations via direct numerical simulation (DNS). The evolution of the dominant oscillation mode and the damping rate for single, translating droplets as well as the effect of nearby droplets in the stream is compared with an analytical solution. Time until grouping in the first and subsequent grouping behavior in the second considered stage are examined for varying initial deviation from a spherical droplet and different initial Reynolds numbers. The study shows that shape oscillation resulting from sufficient deformation tends to expedite grouping processes in the stage after breakup of the liquid jet, decreasing time until grouping up to 33 % for a Reynolds number of 500. The coalescence in the grouping process within the second stage also induces stretching of the droplets. The influence on follow-up grouping after droplet coalescence in streams is found to be minor, since in this case time scales of the damping of the oscillation are small compared to characteristic times for the grouping process itself.}, added-at = {2025-02-14T11:14:18.000+0100}, author = {Ibach, Matthias and Vaikuntanathan, Visakh and Arad, ALumah and Katoshevski, David and Greenberg, Barry and Weigand, Bernhard}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2de7f2051449a77603890935e9768e5dd/simtechpuma}, eventtitle = {ILASS-Europe 2023, 32nd Conference on Liquid Atomization and Spray Systems, 4-7 September 2023}, interhash = {ccbd02df2556a7be884db25a670df8f0}, intrahash = {de7f2051449a77603890935e9768e5dd}, keywords = {EXC2075 PN1 PN1-2(II) PN1-2B misc}, timestamp = {2025-02-14T11:14:18.000+0100}, title = {Numerical Study of Oscillating Droplets and their Relevance to Grouping in Streams}, venue = {Napoli, Italy}, year = 2023 }