Доступ предоставлен для: Guest
Портал Begell Электронная Бибилиотека e-Книги Журналы Справочники и Сборники статей Коллекции
Atomization and Sprays
Импакт фактор: 1.262 5-летний Импакт фактор: 1.518 SJR: 0.814 SNIP: 1.18 CiteScore™: 1.6

ISSN Печать: 1044-5110
ISSN Онлайн: 1936-2684

Выпуски:
Том 29, 2019 Том 28, 2018 Том 27, 2017 Том 26, 2016 Том 25, 2015 Том 24, 2014 Том 23, 2013 Том 22, 2012 Том 21, 2011 Том 20, 2010 Том 19, 2009 Том 18, 2008 Том 17, 2007 Том 16, 2006 Том 15, 2005 Том 14, 2004 Том 13, 2003 Том 12, 2002 Том 11, 2001 Том 10, 2000 Том 9, 1999 Том 8, 1998 Том 7, 1997 Том 6, 1996 Том 5, 1995 Том 4, 1994 Том 3, 1993 Том 2, 1992 Том 1, 1991

Atomization and Sprays

DOI: 10.1615/AtomizSpr.2014007590
pages 895-913

EFFECTS OF LIQUID AND SURFACE CHARACTERISTICS ON OSCILLATION BEHAVIOR OF DROPLETS UPON IMPACT

Darren Banks
Department of Mechanical Engineering, University of California-Riverside, Riverside, California 92521, USA
Cynthia Ajawara
Department of Mechanical Engineering, University of California-Riverside, Riverside, California 92507, USA
Rafael Sanchez
Department of Mechanical Engineering, University of California-Riverside, Riverside, California 92507, USA
Hamza Surti
Department of Mechanical Engineering, University of California-Riverside, Riverside, California 92507, USA
Guillermo Aguilar
Department of Mechanical Engineering, University of California-Riverside, Riverside, California 92507, USA

Краткое описание

The physical behavior of a single droplet impacting a surface is one of the most fascinating facets of spray research. Under some conditions, a droplet will strike and spread across a solid surface without splashing or rebounding. That droplet will spread and recoil for some time, oscillating between a disk and a hemisphere until these fluctuations diminish due to viscous damping. These oscillations affect the liquid coverage area and are essential in droplet solidification applications; yet little is known about them; Knowing more will, for example, enable higher-precision three-dimensional printing or enhanced droplet and spray cooling. Using mixtures of water and glycerol, oscillations of droplets with kinematic viscosities between 1.0 × 10−6 and 1.1 × 10−4 m2 /s are explored, focusing on the damping behavior. Several impact substrates were used. Droplets freefall onto the target with velocities of 0.5−1.5 m/s. The Weber number of the droplets ranged from 10 to 100 and the Reynolds number from 15 to 4000. The impact velocity, spreading lamella diameter, and thickness at the center of each droplet were measured. Droplet kinematic viscosity, impact velocity, and surface tension effects are found to play a role in oscillations, which occur at approximately 75−90 Hz. For the liquids tested, a hydrophilic surface thins the droplet, arresting oscillations quickly, whereas a hydrophobic surface sustains oscillations. Correspondingly, a highly viscous droplet tends to stop oscillations sooner than a less viscous droplet. Increasing the velocity of impact restricts oscillations by spreading liquid across a larger area. For the range of conditions studied, viscosity dominates droplet oscillations when compared to the surface effects. We explore the interplay between viscous and surface tension effects in the oscillations. The spring constant and damping coefficient of an analogous harmonic system are calculated for the observed droplet oscillations. The tested liquid droplets generally exhibit underdamped behavior; higher damping coefficients are associated with more wetting and more viscous droplet liquids−a 103 increase in viscosity corresponds with an approximately 101 increase in damping. The spring constant appears to be influenced by the droplet composition and the surface wettability in a less trivial manner, with similar magnitudes and no discernable pattern in the spring constant (1.5−3.0 N/m) for all droplets and surface conditions examined.

Ключевые слова: droplet impact, wettability, oscillations, contact angle