Experimental Investigation of Droplet Dynamics on Solid Surfaces: Spreading and Recoil Effects

2006 ◽  
Author(s):  
Kalpak P. Gatne ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Lower Surface ◽  
Video Camera ◽  
Temporal Variations ◽  
Liquid Viscosity ◽  
Viscous Effects ◽  
Droplet Dynamics ◽  
Digital Video Camera ◽  
The Impact

A study of the normal impact of liquid droplets on a dry horizontal substrate is presented in this paper. The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 2000 frames per second. A digital image processing software was used to determine the drop spread and height of the liquid on the surface from each frame. To ascertain the effects of liquid viscosity and surface tension, experiments were conducted with four liquids (water, ethanol, propylene glycol and glycerin) that have vastly different fluid properties. Three different Weber numbers (20, 40, and 80) were considered by altering the height from which the drop is released. The high-speed photographs of impact, spreading and recoil are shown and the temporal variations of dimensionless drop spread and height are provided in the paper. The results show that changes in liquid viscosity and surface tension significantly affect the spreading and recoil behavior. For a fixed Weber number, lower surface tension promotes greater spreading and higher viscosity dampens spreading and recoil. Using a simple scale analysis of energy balance, it was found that the maximum spread factor varies as Re1/5 when liquid viscosity is high and viscous effects govern the spreading behavior.

Experimental Investigation of Low Weber Number Post-Impact Drop Spreading on Solid Substrates

2010 ◽  
Author(s):  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Pure Water ◽  
Surfactant Solution ◽  
Video Camera ◽  
Dynamic Surface Tension ◽  
Temporal Variations ◽  
Dynamic Surface ◽  
Post Impact ◽  
Triton X

The post-impact spreading and recoil behaviors of droplets of pure liquids (water and ethanol) and aqueous solution of Triton X-100 (a surfactant) on a dry horizontal hydrophilic (glass) substrate are investigated for low Weber numbers. The evolution of drop shape during spreading and recoil are captured using a high-speed (4,000 frames per second) digital video camera. Digital image-processing was used to determine the spread and height of the liquid film on the surface from each frame. Unlike pure liquids, the liquid-gas interfacial tension for surfactant solution is a function of surface age, where surface tension is that of the solvent at zero time and then reaches an equilibrium value with increasing surface age. Furthermore, the equilibrium surface tension is a function of the surfactant concentration, which decreases from that of the solvent at zero concentration to that at the critical micelle concentration (CMC), and remains essentially constant thereafter. The surface tension of aqueous Triton X-100 solution varies from that of pure water to nearly that of ethanol. As such the comparison of transient droplet-impact-spreading-recoil behavior of the three liquids, or their temporal variations of the spread and the flattening factor, provides a basis for understanding the role of dynamic surface tension and surface wettability.

Effects of Surface Tension on Drop Impact on a Horizontal Rotating Disk

2012 ◽  
Vol 268-270 ◽  
pp. 1084-1093
Author(s):  
Xiao Fang Yuan ◽  
Jing Yin Li ◽  
Bin Zhang
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Tangential Velocity ◽  
Rotating Disk ◽  
Lower Surface ◽  
Drop Impact ◽  
Experimental Results ◽  
Impact Processes ◽  
Lower Surface Tension ◽  
The Impact

The impact processes of water and ethanol drops on a rotating horizontal aluminum disk were recorded and analyzed using a high-speed digital camera together with an image analysis program. The angular velocities of the disk were altered to study the effect of surface tension of drops on drop impact processes. The experimental results show that a lower surface tension will result in a higher tangential spread factor and a lower receding rate during the receding stage, for the drop impinging and depositing on a rotating disk. In addition, a lower surface tension of the drop tends to promote the occurrence of splash. The experimental results further verify a proposed correlation of splash-deposition boundary for drops impinging on a rotating disk. Both drops, though they have a quite different surface tension, experience four stages, with two new stages different from those of drops impinging on stationary surfaces. Their tangential spreading factors both increase obviously with the tangential velocity at the impact point, while their radial spreading factors vary a little.

scholarly journals An analysis of surface breakup induced by laser-generated cavitation bubbles in a turbulent liquid jet

2020 ◽  
Vol 61 (12) ◽  
Author(s):  
Jiayi Zhou ◽  
Mats Andersson
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Surface Deformation ◽  
Bubble Formation ◽  
Injection Pressure ◽  
Lower Surface ◽  
Video Camera ◽  
Liquid Jets ◽  
Water Mixture ◽  
Cavitation Bubbles

Abstract The breakup of turbulent liquid jets by cavitation bubbles was investigated by artificially introducing them by focusing laser light into the jet. The induced surface deformations and ejected liquid structures were characterized using shadowgraphy with a high-speed video camera. The flow velocity of the liquid jets, which were ejected from a 6 mm nozzle, was varied by adjusting the injection pressure from 1 to 5 bar. Deionized water and a dipropylene glycol–water mixture were used to compare the breakup of liquid jets with different surface tension and viscosity. Surface deformation and breakup were found to occur in two stages. One was early breakup of liquid strings into tiny droplets. This was followed by the formation of a larger structure separating into ligaments and larger drops. Averaged time-resolved one-dimensional plots were introduced and implemented to analyze breakup statistically, to address the problem of shot-to-shot variations in the breakup due to the turbulent condition of the jets. Bubble-induced breakup could easily be distinguished from spontaneous breakup with this method. Both the position of bubble formation and the injection pressure had an influence on the scale of the breakup. The deformation of the jet surface was highly affected by shear. The structure of the deformation became less intact when the surface tension was lower. The sizes of the drops produced during the second stage of breakup were analyzed. The bubble-induced breakup produced smaller drops than the spontaneous breakup at lower injection pressure. As expected, lower surface tension favored droplet detachment and smaller sized drops. Graphic abstract

Effects of Different Liquid Properties on the Characteristics of Impact-Generated High-Speed Liquid Jets

2011 ◽  
Vol 110-116 ◽  
pp. 370-376 ◽  
Author(s):  
Anirut Matthujak ◽  
Chaidet Kasamnimitporn ◽  
Wuttichai Sittiwong ◽  
Kulachate Pianthong
Keyword(s):  
High Speed ◽  
Physical Property ◽  
Ambient Air ◽  
Video Camera ◽  
Orifice Diameter ◽  
Liquid Jets ◽  
Jet Formation ◽  
Digital Video Camera ◽  
Maximum Penetration ◽  
The Impact

This paper describes the study of high-speed liquid jets injected in air from an orifice. The main focus is to study the effect of different liquid properties on the characteristics of the high-speed liquid jets injected in ambient air. The high-speed liquid jets are generated by the impact of a projectile, which known as impact acceleration method, launched in a horizontal single-stage power gun (HSSPG). The conical nozzle of 30° angle with the orifice diameter of 0.7 mm was used to generate the jets. The characteristics of high-speed jets were visualized by the high-speed digital video camera with shadowgraph optical arrangement. From the shadowgraph images, the jet formation, atomization, vaporization and shock waves were obviously observed. The maximum averaged velocity of water, alcohol, n-hexane, chloroform and glycerin jets is estimated to be 1,669.03 m/s, 1,548.59 m/s, 1,420.44 m/s, 1,204.46 m/s and 1,496.97 m/s, respectively. That effect on the maximum penetration distance of the water jet is longer than that of all jets. Surface tension and latent heat are the significant physical property for jet formation, while density, kinematics viscosity and heat capacity are not.

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

Experiments on the breakup of drop-impact crowns by Marangoni holes

2018 ◽  
Vol 844 ◽  
pp. 162-186 ◽  
Author(s):  
Abdulrahman B. Aljedaani ◽  
Chunliang Wang ◽  
Aditya Jetly ◽  
S. T. Thoroddsen
Keyword(s):  
Surface Tension ◽  
Lower Surface ◽  
High Viscosity ◽  
Solid Substrate ◽  
Immiscible Liquid ◽  
Hole Formation ◽  
Low Viscosity ◽  
Stress Changes ◽  
Lower Surface Tension ◽  
The Impact

We investigate experimentally the breakup of the Edgerton crown due to Marangoni instability when a highly viscous drop impacts on a thin film of lower-viscosity liquid, which also has different surface tension than the drop liquid. The presence of this low-viscosity film modifies the boundary condition, giving effective slip to the drop along the solid substrate. This allows the high-viscosity drop to form a regular bowl-shaped crown, which rises vertically away from the solid and subsequently breaks up through the formation of a multitude of Marangoni holes. Previous experiments have proposed that the breakup of the crown results from a spray of fine droplets ejected from the thin low-viscosity film on the solid, e.g. Thoroddsen et al. (J. Fluid Mech., vol. 557, 2006, pp. 63–72). These droplets can hit the inner side of the crown forming spots with lower surface tension, which drives a thinning patch leading to the hole formation. We test the validity of this assumption with close-up imaging to identify individual spray droplets, to show how they hit the crown and their lower surface tension drive the hole formation. The experiments indicate that every Marangoni-driven patch/hole is promoted by the impact of such a microdroplet. Surprisingly, in experiments with pools of higher surface tension, we also see hole formation. Here the Marangoni stress changes direction and the hole formation looks qualitatively different, with holes and ruptures forming in a repeatable fashion at the centre of each spray droplet impact. Impacts onto films of the same liquid, or onto an immiscible liquid, do not in general form holes. We furthermore characterize the effects of drop viscosity and substrate-film thickness on the overall evolution of the crown. We also measure the three characteristic velocities associated with the hole formation: i.e. the Marangoni-driven growth of the thinning patches, the rupture speed of the resulting thin films inside these patches and finally the growth rate of the fully formed holes in the crown wall.

Effect of Hydrated Salt Additives on Film Boiling Behavior at Vapor Film Collapse

2008 ◽  
Author(s):  
Takahiro Arai ◽  
Masahiro Furuya
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Film Boiling ◽  
Vapor Film ◽  
Quenching Temperature ◽  
Steel Sphere ◽  
Digital Video Camera ◽  
Collapse Temperature ◽  
Test Film ◽  
Film Collapse

A high-temperature stainless-steel sphere was immersed into various salt solutions to test film boiling behavior at vapor film collapse. The film boiling behavior around the sphere was observed with a high-speed digital-video camera. Because salt additives enhanced condensation heat transfer, the observed vapor film was thinner. Surface temperature of the sphere was measured. Salt additives increased the quenching (vapor film collapse) temperature, because frequency of direct contact between sphere surface and coolant increased. Quenching temperature rises with increased salt concentration. The quenching temperature, however, approaches a constant value when the slat concentration is close to its saturation concentration. The quenching temperature is well correlated with ion molar concentration, which is a number density of ions, regardless of the type of hydrated salts.

In-Flow Oscillation of Circular Cylinders in Cross-Flow

2007 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Hiroshi Haruguchi ◽  
Hiroyuki Nakajima ◽  
Toyohiro Sawada ◽  
Kozo Sugiyama
Keyword(s):  
High Speed ◽  
Flow Direction ◽  
Vortex Motion ◽  
Cross Flow ◽  
Video Camera ◽  
Circular Cylinders ◽  
Flow Oscillation ◽  
Single Cylinder ◽  
Digital Video Camera ◽  
Flow Oscillations

The importance of the in-flow oscillation of a single cylinder in cross-flow has been highlighted since an accident in a FBR-type reactor. In-flow oscillations have also been observed in tube arrays. This report is an experimental study on this phenomenon using totally nine cylinders in a water tunnel. Six cases, one single cylinder, two & three cylinders in parallel & in tandem, and a nine cylinder bundle, are examined. Every cylinder can move only in in-flow direction. The motion of cylinders is measured by the strain gages and by a high-speed digital video camera. The results are compared with the visualized vortex motion.

Bubble Lift-Off Diameter in Forced Convective Boiling Flow

2010 ◽  
Author(s):  
In-Cheol Chu ◽  
Chul-Hwa Song
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Bubble Nucleation ◽  
Present Observation ◽  
Convective Boiling ◽  
Digital Video Camera ◽  
Nucleation Frequency ◽  
Boiling Flow ◽  
Lift Off ◽  
Basic Features

A series of experiments were carried out to investigate the bubble nucleation to lift-off phenomena for a subcooled boiling flow in a vertical annulus channel. A high speed digital video camera was used to capture the dynamics of the bubble nucleation to lift-off process. A total of 148 recordings were made, and the bubble lift-off diameter and the bubble nucleation frequency were evaluated for 118 recordings up to now. The basic features of the lift-off diameter and nucleation frequency were addressed based on the present observation. A database for the bubble lift-off diameter was built by gathering and summarizing the data of Prodanovic et al., Situ et al., and the present work. The prediction capability of Unal’s model, Situ et al.’s model, and Prodanovic et al.’s correlation was evaluated against the database. The best prediction results were obtained by modifying the wall superheat correlation in Unal’s model.

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