Visual Research Of The Effect Of Surface Tension On Drop Deformation Regularity During Formation And Motion

The formation and movement of drop is the basic physics of surface tension measurement,ink-jet printing,atomization of fuel and many other engineering applications.It is important that studying the formation and movement regularly based on the drop deformation.The visualization method of droplet formation and dropping process were observed and the effect of surface tension on the process was studied.The main research contents and conclusions are as follows:1.Models which describe the formation,like static drop profile model,drop formation dynamic model,and Lamb's linear oscillation period model,are established respectively.Bo number,Ca number,Re number and We number are achieved.2.Set up the droplet deformation visualization experiment platform.The visualization experimental observation on the drop formation and free falling process were completed.Results are as follows:(1)The process of drop elongate is divided into initial oscillate,constant speed elongate and accelerate elongate.The static drop profile and the constant speed elongate process are controlled by Bo number.The process of accelerate elongate is controlled by We number.When the droplet formation period is relatively short,the initial oscillate and the constant speed elongate processes are simultaneously carried out.Bo number affects the elongate velocity in constant speed elongate process and We number affects the time of elongate acceleration and the turning point of the acceleration process.(2)Main factors impact the movement of satellite drop are ligament elongation,interaction time,satellite drop volume.Higher capillary pressure will be achieved on the end point of ligament with a greater ligament elongate rate.And the satellite drop motion tends to be upward.The longer of dimensionless interaction time sustains the longer of upward capillary pressure affects.And the satellite drop motion tends to be upward.The bigger of the volume of satellite is the greater of its gravity affects.And the satellite drop motion tends to be down.The velocity,angle and curvature on the contact point between satellite and the surface of residual liquid on the tip of capillary and main drop will also affect the motion tendency of satellite drop.(3)Oscillation deformation on the initial of free falling process is caused by the unbalance of capillary pressure.And high order surface wave was observed when the drop is big.The oscillation amplitude will be dissipated as the time goes by and finally present a axisymmetric oscillation mode with n=2 order surface wave.(4)Even though it has high order surface wave on the initial of oscillation deformation but oscillation period of the liquid droplet is almost identical with the linear theory of Lamb under n=2.3.Static surface tension and dynamic surface tension are measured by drop weight method and Wilhelmy slide method respectively.And the effect of trace anionic surfactant SDBS and the effect of surface tension on liquid droplet deformation are also studied.Results are as follows:(1)In the process of forming and falling,the SDBS molecules on the interface did not reach the adsorption equilibrium.(2)The dynamic surface tension is always higher than the static surface tension due to the surfactant adsorption unbalance on the drop surface.With the higher concentration of the SDBS the difference of between dynamic surface tension and static surface tension is smaller.(3)Surface tension will affect the oscillation period and amplitude.When the surface tension is small the oscillation period will be long and the amplitude will be great.4.Based on the experimental results,a mathematical model is established to describe the vibration and deformation of liquid droplets...