scholarly journals Prediction of maximum spreading time of water droplet during impact onto hot surface beyond the Leidenfrost temperature

2021 ◽  
pp. 101396
Author(s):  
S. Illias ◽  
S. Hussain ◽  
Y.A. Rahim ◽  
M.A. Idris ◽  
M.E. Baharudin ◽  
...  
Keyword(s):  
Water Droplet ◽  
Leidenfrost Temperature ◽  
Spreading Time ◽  
Hot Surface ◽  
Maximum Spreading

The Effect of the Surface Inclination on the Hydrodynamics and Thermodynamics of Leidenfrost Droplets

2014 ◽  
Vol 30 (2) ◽  
pp. 145-151 ◽  
Author(s):  
P. Pournaderi ◽  
A. R. Pishevar
Keyword(s):  
Contact Time ◽  
Heat Removal ◽  
Total Heat ◽  
Vapor Layer ◽  
Accurate Calculation ◽  
Simulation Process ◽  
Mesh Resolution ◽  
Surface Inclination ◽  
Hot Surface ◽  
Maximum Spreading

ABSTRACTIn this research, the effect of the surface inclination on the hydrodynamics and heat transfer of droplets impinging on very hot surfaces is studied. The applied numerical algorithm is based on the accurate calculation of the vaporization rate in the simulation process using a combination of the level set and ghost fluid methods. Also a mesh clustering technique is utilized to create sufficient mesh resolution near the surface in order to take into account the effect of the thin vapor layer between droplet and very hot surface. The results are verified against available experiments. The effect of the surface inclination on the droplet maximum spreading radius, droplet contact time and total heat removal from the surface is considered. Results show that for the studied regime, the maximum spreading radius of the droplet is decreased with an increase in the surface inclination while the droplet contact time on the surface is independent from the surface inclination. For inclinations greater than 45°, the total heat removal is decreased considerably with an increase in the inclination angle. For smaller inclinations, the dependency of the total heat removal on the surface inclination is not strong.

Impinging Characteristics of Water Droplet on Hot Surface: Effect of Wall Inclination

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Choong Hyun Lee ◽  
Kyung Chun Kim
Keyword(s):  
Water Droplet ◽  
Surface Effect ◽  
Hot Surface

Photogallery Entry 8

Deformation and Rebounding Processes of a Water Droplet Impinging on a Flat Surface Above Leidenfrost Temperature

1996 ◽  
Vol 118 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Hitoshi Fujimoto ◽  
Natsuo Hatta
Keyword(s):  
Surface Tension ◽  
Water Droplet ◽  
Stokes Equations ◽  
Water Film ◽  
Video Camera ◽  
Ring Structure ◽  
Point Of View ◽  
Navier Stokes ◽  
Leidenfrost Temperature ◽  
Incompressible Fluid Flows

This paper treats numerical analyses of the deformation and rebounding processes of a water droplet impinging on a flat solid surface above the Leidenfrost temperature with a speed in the order of a few [m/s], as well as the flow field inside the droplet. These calculations were performed using the MAC-type solution method to solve a finite differencing approximation of the axisymmetric Navier-Stokes equations governing incompressible fluid flows. Also, the whole dynamic process of a droplet from the moment of collision with a hot surface including the rebound from it was recorded by using a video camera equipped with a macro lens. First, the water film formed by the droplet impinging on the surface spreads radially in a fairly thin discoid-like shape until it reaches a maximum. Next, the water film begins to recoil backwards towards the center and the recoiling process continues to occur owing to the surface tension effect at the periphery. Subsequently, the center part of the liquid drop begins to elongate upwards and the liquid near the top of the drop pulls up the lower part of the remaining liquid. Finally, a vortical ring structure appearing at the bottom of the elongated droplet induces the rotative motion in such a way as to form the rising flow and the droplet rebounds from the surface as a bowling pin-shaped mass. The numerical model to predict the deformation and rebounding processes was built up by accounting for the presence of viscous and surface tension effects. The numerical results obtained by the model were compared with the experimental data and discussed from a practical point of view.

Dynamic Behavior of a Small Water Droplet Impact Onto a Heated Hydrophilic Surface

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
El-Sayed R. Negeed ◽  
M. Albeirutty ◽  
Sharaf F. AL-Sharif ◽  
S. Hidaka ◽  
Y. Takata
Keyword(s):  
Dynamic Behavior ◽  
Water Droplet ◽  
High Speed ◽  
Heated Surface ◽  
Droplet Diameter ◽  
Video Camera ◽  
Surface Wettability ◽  
Hydrodynamic Characteristics ◽  
Small Water ◽  
Hot Surface

The aim of this study is to investigate the influence of the surface wettability on the dynamic behavior of a water droplet impacting onto a heated surface made of stainless steel grade 304 (Sus304). The surface wettability is controlled by exposing the surfaces to plasma irradiation for different time periods (namely, 0.0, 10, 60, and 120 s). The experimental runs were carried out by spraying water droplets on the heated surface where the droplet diameter and velocity were independently controlled. The droplet behavior during the collision with the hot surface has been recorded with a high-speed video camera. By analyzing the experimental results, the effects of surface wettability, contact angle between impacting droplet and the hot surface, droplet velocity, droplet size, and surface superheat on the dynamic behavior of the water droplet impacting on the hot surface were investigated. Empirical correlations are presented describing the hydrodynamic characteristics of an individual droplet impinging onto the heated hydrophilic surfaces and concealing the affecting parameters in such process.

Dynamic of Water Droplet Impacting on a Hydrophilic Surface Accompanied With Stagnation Flow

2014 ◽  
Author(s):  
Morteza Mohammadi ◽  
Mohammadreza Attarzadeh ◽  
Moussa Tembely ◽  
Ali Dolatabadi
Keyword(s):  
Shear Flow ◽  
Water Droplet ◽  
High Speed ◽  
Air Flow ◽  
Droplet Impact ◽  
Impact Behavior ◽  
Aluminum Surface ◽  
High Speed Photography ◽  
Stagnation Flow ◽  
Maximum Spreading

Droplet impact on solid surfaces has been extensively reported in the literature, however the effect of accompanying air flow on the outcome of impacting droplet has yet to be addressed and analyzed which is similar to real scenario of impacting water droplet on aircraft’s leading edge at in-flight icing conditions. This study addresses the net effect of airflow (i.e. stagnation and the resultant shear flow) on the impacting water droplet with the same droplet impact velocity which is exposed to different airspeeds. In order to provide stagnation flow, a droplet accelerator was built which can generate different airspeeds up to 20 m/s. Droplet impact behavior accompanied with stagnation flow on a polished aluminum surface with a contact angle of 70° was investigated by high speed photography. 2.5 mm water droplet size with impact velocities of 2, 2.5 and 3 m/s which correspond to non-splashing regime of impacts are exposed to three different regimes of air speeds namely 0 (i.e. still air case), 10, and 20 m/s. It was observed that when droplet reaches to its maximum spreading diameter, some fingered shape at the end of spreading lamella (i.e. Rayleigh-Taylor instability) is appeared. When stagnation flow is present these fingered shape droplets are exposed to the generated shear flow close to the substrate (i.e. Homann flow approach) causes a droplet break up while complete non-splashing regime is observed in still air case. In spite of the fact that maximum spreading diameter is not largely affected by air flow compare to still air case, droplet height variation is significantly reduced by about 70 percent for strong stagnation flow (i.e. 20 m/s) which generates non-recoiling condition resulting in the thin film formation.

scholarly journals Direct numerical simulation of the impact of a droplet onto a hot surface above the Leidenfrost temperature

2017 ◽  
Vol 104 ◽  
pp. 1090-1109 ◽  
Author(s):  
Lucia Rueda Villegas ◽  
Sébastien Tanguy ◽  
Guillaume Castanet ◽  
Ophélie Caballina ◽  
Fabrice Lemoine
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Leidenfrost Temperature ◽  
Hot Surface ◽  
The Impact
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