Lateral jetting during off-center drop collisions on substrates

• Published in: International journal of heat and mass transfer 2018-07, Vol.122, p.740-748
• Main Authors: Tilger, Christopher F., Beacham, Sean T., Oehlschlaeger, Matthew A.
• Format: Article
• Language: English
• Subjects: Fluid dynamics; Heat transfer; Hydrochloric acid; Impact velocity; Jets; Jetting; Liquid drop impact; Sidelobes; Spreading; Substrates; Surface roughness; Water drops; Weber number
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2018.02.021

•The off-center impact of falling and sessile water drops is characterized.•Seven regimes are observed with prominent side jet evolving at a range of critical offsets.•The largest jets extend >2× the spread drop radius and project at >10× the impact velocity. In this work, we experimentally study the behavior of a sessile water drop impacted by another drop of water using a bottom-up viewing configuration and optically clear substrates. By varying the Weber number and the center-line impact offset distance, a variety of regimes based on the post-impact geometry are observed. A pair of side lobes/jets extending more than twice the maximum spread of the impacting drop are found to form at low to moderate Weber number at an offset distance close to three-quarter the combined radii of the two initial drops. The onset of these jets is probed further with a high-speed imaging study showing slender jets issue from the impacting drops ∼0.25 ms after impact at a velocity an order of magnitude greater than the impact velocity.