Effect of Surface Roughness on Single Cryogen Droplet Spreading

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Jie Liu ◽  
Walfre Franco ◽  
Guillermo Aguilar
Keyword(s):  
Surface Roughness ◽  
Human Skin ◽  
Droplet Diameter ◽  
Skin Surface ◽  
Skin Layer ◽  
Droplet Spreading ◽  
Viscous Boundary Layer ◽  
Superficial Skin ◽  
The Impact ◽  
Effect Of Surface

Cryogen spray cooling is an auxiliary procedure to dermatologic laser surgery, which consists of precooling the superficial skin layer (epidermis) during laser irradiation of subsurface targets to avoid nonspecific epidermal thermal damage. While previous studies have investigated the interaction of cryogen sprays with microscopically smooth human skin models, it is important to recognize that real human skin surface is far from smooth. With the objective to provide physical insight into the interaction between cryogen sprays and human skin, we study the effect of surface roughness on the impact dynamics of single cryogen droplets falling on skin models of various roughnesses (0.5–70μm). We first develop a theoretical model to predict the maximum spread diameter (Dm) following droplet impingement based on a similarity approximation to the solution of a viscous boundary layer that incorporates friction as the major source of viscous dissipation on a rough surface. Then, we measure the droplet diameter, impact velocity, and Dm of cryogen droplets falling by gravity onto skin models. Experimental data prove that the proposed model predicts Dm with good accuracy, suggesting that the effects of surface roughness and friction on Dm are properly taken into account for the range of surface roughness studied herein.

The Effect of Roughness on the Impact Dynamics and Heat Transfer of Cryogen Droplets Impinging Onto Indented Skin Phantoms

2005 ◽  
Author(s):  
Jie Liu ◽  
Walfre Franco ◽  
Guillermo Aguilar
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Human Skin ◽  
Spray Deposition ◽  
Skin Surface ◽  
Therapeutic Modality ◽  
Impact Dynamics ◽  
Large Momentum ◽  
Superficial Skin ◽  
The Impact

Laser dermatological surgery (LDS) is the preferred therapeutic modality for various dermatoses, including port wine stain (PWS) birthmarks. LDS is commonly used in conjunction with cryogen spray cooling, which is an auxiliary procedure that pre-cools the superficial skin layer (epidermis) prior to laser irradiation to avoid non-specific and excessive epidermal heating. Clinical observations show that skin indents markedly during spray deposition due to the large momentum of cryogen droplets. Furthermore, the human skin surface is far from smooth. Therefore, with the objective to provide some insight into the interaction between cryogen sprays and the rough and deformable human skin surface, the impingement dynamics and heat transfer induced by single cryogen droplets falling on rough and indented skin phantoms are present in this paper. Epoxy skin phantoms with a constant semispherical indentation of depth and radius of 2.44 mm and 6.34 mm, respectively, were used to simulate indented skin. Each phantom had a different surface roughnesses varying from 0.5 μm to 50μm. The experiments were carried out within a pressurized chamber to control or eliminate droplet evaporation. A high-speed camera and the temperature sensors placed on the upper surface of the skin phantoms were synchronized to record the impact dynamics and temperature changes as cryogen droplets fell on them. The results show that the surface roughness affects the impact dynamics and heat transfer during single droplet impingement. As the surface roughness (Ra) increasing, the heat flux decrease.

Effect of surface roughness on substrate-tuned gold nanoparticle gap plasmon resonances

Nanoscale ◽  
2015 ◽  
Vol 7 (9) ◽  
pp. 4250-4255 ◽  
Author(s):  
Chatdanai Lumdee ◽  
Binfeng Yun ◽  
Pieter G. Kik
Keyword(s):  
Surface Roughness ◽  
Gold Nanoparticles ◽  
Gold Nanoparticle ◽  
Single Particle ◽  
Gold Films ◽  
Particle Scattering ◽  
Plasmon Resonances ◽  
Scattering Spectra ◽  
The Impact ◽  
Effect Of Surface

The impact of nanoscale surface roughness on substrate-tuned gold nanoparticle plasmon resonances is demonstrated by comparing single-particle scattering spectra with simulated scattering spectra of gold nanoparticles on gold films with realistic roughness.

Relationship between dermal birefringence and the skin surface roughness of photoaged human skin

2009 ◽  
Vol 14 (4) ◽  
pp. 044032 ◽  
Author(s):  
Shingo Sakai ◽  
Noriaki Nakagawa ◽  
Masahiro Yamanari ◽  
Arata Miyazawa ◽  
Yoshiaki Yasuno ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Human Skin ◽  
Skin Surface ◽  
Skin Surface Roughness

Droplet Oscillation After Impact on a Solid Surface

2016 ◽  
Author(s):  
Yina Yao ◽  
Shuai Meng ◽  
Cong Li ◽  
Xiantao Chen ◽  
Rui Yang
Keyword(s):  
Contact Angle ◽  
Spray Deposition ◽  
Liquid Droplet ◽  
Droplet Diameter ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Oscillation Period ◽  
Droplet Spreading ◽  
Oscillation Phenomenon ◽  
The Impact

Droplet spreading and oscillation occur when a liquid droplet impacts on the solid surfaces. This process is vital in many industrial applications, such as ink-jet printing technologies, spray coating and agricultural spray deposition. However, the researches that have been done mainly focused on the spreading process, and less attention has been paid to the droplet oscillation phenomenon, which has influence on the solidification and evaporation process. Therefore, the study on droplet oscillation phenomenon after the impact is necessary and valuable. This paper aims at analyzing the droplet oscillation phenomenon using VOF method. Since the contact angle varies dramatically in the dynamic process, a dynamic contact angle model is introduced to improve the simulation accuracy. The dynamic contact angle model has been verified by comparing the numerical results with experimental and theoretical results. In order to study the factors that may influence the droplet oscillation period, different droplet diameters and impact velocities are utilized in this simulation. The results show that the oscillation period presents a positive relationship with droplet diameter. However, the impact velocity has no apparent influence on the oscillation period, which agrees well with the theoretical analysis.

Development of a Biomimetic Vibrotactile Sensor for Dynamic Deformation With an Array of Polymer Structures

2015 ◽  
Author(s):  
Jae Young Choi ◽  
Baek Chul Kim ◽  
Ja Choon Koo
Keyword(s):  
Surface Roughness ◽  
Human Skin ◽  
Dynamic Deformation ◽  
Skin Surface ◽  
Electrical Signal ◽  
Point Of View ◽  
Static Deformation ◽  
Skin Deformation ◽  
Vibration Sensing ◽  
Finger Skin

Humans can discriminate surface roughness using fingertip’s touch. It is believed that surface roughness is perceived by static and dynamic deformation of human skin. Recent findings have shown that subcutaneous slowly adapting mechanoreceptor (SA) detect static deformation of finger skin. However, there are difficulties to infinitely increase density of SA in limited skin space. [1] So, we focused on dynamic deformation is related with rapidly adapting mechanoreceptor (RA). In the process of scanning surface of objects with fingertips, RA detects vibrations induced by skin deformation. In this study, we suggest that sensors mimicking roles of RA can detect surface roughness. We used a polymer having similar characteristics of skin surface that transduce physical vibrations into electrical signal. And an array of polymer structures discriminates surface roughness. In other researches, they were tried to use one mechanoreceptor to acquire total range of vibrations. From the point of view which RAs have different vibration sensing ranges, we divided range of vibration through polymer structures and analyzed frequency element.

scholarly journals Effect of Grain Size and Surface Roughness on the Normal Coefficient of Restitution of Single Grains

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 814
Author(s):  
Chitta Sai Sandeep ◽  
Lina Luo ◽  
Kostas Senetakis
Keyword(s):  
Surface Roughness ◽  
Grain Size ◽  
Coefficient Of Restitution ◽  
Block Type ◽  
Flow Energy ◽  
Different Types ◽  
The Impact ◽  
Impact Experiments ◽  
Two Bodies ◽  
Effect Of Surface

The coefficient of restitution (COR) represents the fraction of pre-collision kinetic energy remained after the collision between two bodies. The COR parameter plays an important role in the discrete numerical analysis of granular flows or the design of protective barriers to reduce flow energy. This work investigated the COR for grain-block type impacts through comprehensive experiments using a custom-built impact loading apparatus. Glass balls of three different sizes were used as grains. The impact experiments were performed on three different types of materials as base blocks, namely brass, granite and rubber. Experiments on the brass block showed a decrease in COR values with increasing grain size. On the contrary, impacts on granite and rubber blocks showed an increase in COR values with increasing grain size. Additionally, the effect of surface roughness on the COR was investigated. It was revealed that the increase in surface roughness of either the grain or the block reduced the COR values due to the increased plastic deformations of surface asperities.

scholarly journals Effect of Surface Roughness during Peristaltic Movement in a Nonuniform Channel

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
R. Shukla ◽  
S. S. Bhatt ◽  
A. Medhavi ◽  
R. Kumar
Keyword(s):  
Surface Roughness ◽  
Newtonian Fluid ◽  
Biological Fluids ◽  
Current Model ◽  
Roughness Parameter ◽  
Pressure Rise ◽  
Complete Agreement ◽  
Major Mode ◽  
The Impact ◽  
Effect Of Surface

In this study, the effect of the roughness parameter during the peristaltic transport of a Newtonian fluid in a nonuniform channel has been explored. The motivation of this study comes from various research studies in the area of life sciences and engineering, which reveal that the wall of living beings’ arteries and all other surfaces have roughness to some extent. As peristalsis is a major mode of transporting biological fluids in various organs, the effect of surface roughness during peristaltic flow becomes very significant. The problem of peristaltic motion of a Newtonian fluid through a rough nonuniform channel having sinusoidal-shaped roughness has been investigated in the current work. To analyze the flow, analytic formulation of pressure rise, friction force, velocity, and pressure gradient has been carried out under the low Reynolds number and long-wavelength approximation. Results obtained for zero surface roughness from the current model are in complete agreement with previous studies available in the literature that have been carried out without considering the surface roughness of the wall. Numerical outcomes for the properties mentioned above have been plotted for analyzing the impact of roughness on the physical and flow parameters.

The Statistical Analysis of Droplet Train Splashing After Impinging on a Superheated Surface

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Lu Qiu ◽  
Swapnil Dubey ◽  
Fook Hoong Choo ◽  
Fei Duan
Keyword(s):  
Surface Roughness ◽  
Wall Temperature ◽  
Weber Number ◽  
Droplet Diameter ◽  
Copper Surface ◽  
Transition Regime ◽  
Droplet Tracking ◽  
Superheated Surface ◽  
The Impact ◽  
Number Case

An orderly droplet splashing is established when a water droplet train impinges onto a superheated copper surface. The droplets continuously impinge onto the surface with a rate of 40,000 Hz, a diameter of 96 μm or 120 μm, and a velocity of 8.4 m/s or 14.5 m/s. The heat transfers under different wall temperatures are measured, and the corresponding droplet splashing is recorded and analyzed. The effects of wall temperature, droplet Weber number, and surface roughness on the transition of the droplet splashing are investigated. The results suggest that the transferred energy is kept a constant in the transition regime, but a sudden drop of around 25% is observed when it steps into post-transition regime, indicating that the Leidenfrost point is reached. A higher Weber number of droplet train results in a more stable splashing angle and a wider range of splashed droplet diameter. The surface roughness plays no significant role in influencing the splashing angle in the high Weber number case, but the rougher surface elevates the fluctuation of the splashing angle in the low Weber number case. On the rougher surface, the temporary accumulation of the impact droplets is observed, a “huge” secondary droplet can be formed and released. The continuous generation of the huge droplets is observed at a higher wall temperature. Based on the result of droplet tracking of the splashed secondary droplets, the diameter and velocity are correlated.

Enzymatic Determination of Hydroxysteroids in Human Skin Surface Lipids1

1963 ◽  
Vol 41 (5) ◽  
pp. 265-268 ◽  
Author(s):  
Thomas J Cook ◽  
Allan L Lorincz ◽  
Alan R Spector
Keyword(s):  
Human Skin ◽  
Skin Surface ◽  
Enzymatic Determination
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