scholarly journals Sequentially estimating the dynamic contact angle of sessile saliva droplets in view of SARS-CoV-2

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0261441
Author(s):  
Sudeep R. Bapat
Keyword(s):  
Contact Angle ◽  
Data Collection ◽  
Confidence Interval ◽  
Interval Estimation ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Heat Mass Transf ◽  
Drying Time ◽  
Confidence Interval Estimation

Estimating the contact angle of a virus infected saliva droplet is seen to be an important area of research as it presents an idea about the drying time of the respective droplet and in turn of the growth of the underlying pandemic. In this paper we extend the data presented by Balusamy, Banerjee and Sahu [“Lifetime of sessile saliva droplets in the context of SARS-CoV-2,” Int. J. Heat Mass Transf. 123, 105178 (2021)], where the contact angles are fitted using a newly proposed half-circular wrapped-exponential model, and a sequential confidence interval estimation approach is established which largely reduces both time and cost with regards to data collection.

scholarly journals Numerical Bifurcation Analysis of a Film Flowing over a Patterned Surface through Enhanced Lubrication Theory

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 405
Author(s):  
Nicola Suzzi ◽  
Giulio Croce
Keyword(s):  
Contact Angle ◽  
Bifurcation Analysis ◽  
Dynamic Contact Angle ◽  
Flow Characteristics ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Inclined Plate ◽  
Lubrication Equation ◽  
Static Contact ◽  
Numerical Bifurcation

The bifurcation analysis of a film falling down an hybrid surface is conducted via the numerical solution of the governing lubrication equation. Instability phenomena, that lead to film breakage and growth of fingers, are induced by multiple contamination spots. Contact angles up to 75∘ are investigated due to the full implementation of the free surface curvature, which replaces the small slope approximation, accurate for film slope lower than 30∘. The dynamic contact angle is first verified with the Hoffman–Voinov–Tanner law in case of a stable film down an inclined plate with uniform surface wettability. Then, contamination spots, characterized by an increased value of the static contact angle, are considered in order to induce film instability and several parametric computations are run, with different film patterns observed. The effects of the flow characteristics and of the hybrid pattern geometry are investigated and the corresponding bifurcation diagram with the number of observed rivulets is built. The long term evolution of induced film instabilities shows a complex behavior: different flow regimes can be observed at the same flow characteristics under slightly different hybrid configurations. This suggest the possibility of controlling the rivulet/film transition via a proper design of the surfaces, thus opening the way for relevant practical application.

Spreading-Droplet Simulation With Surface Tension Model Using Inter-Particle Force in Particle Method

2013 ◽  
Author(s):  
Eiji Ishii ◽  
Taisuke Sugii
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Particle Method ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Particle Methods ◽  
Static Contact ◽  
Particle Force ◽  
Surface Tension Model

Predicting the spreading behavior of droplets on a wall is important for designing micro/nano devices used for reagent dispensation in micro-electro-mechanical systems, printing processes of ink-jet printers, and condensation of droplets on a wall during spray forming in atomizers. Particle methods are useful for simulating the behavior of many droplets generated by micro/nano devices in practical computational time; the motion of each droplet is simulated using a group of particles, and no particles are assigned in the gas region if interactions between the droplets and gas are weak. Furthermore, liquid-gas interfaces obtained from the particle method remain sharp by using the Lagrangian description. However, conventional surface tension models used in the particle methods are used for predicting the static contact angle at a three-phase interface, not for predicting the dynamic contact angle. The dynamic contact angle defines the shape of a spreading droplet on a wall. We previously developed a surface tension model using inter-particle force in the particle method; the static contact angle of droplets on the wall was verified at various contact angles, and the heights of droplets agreed well with those obtained theoretically. In this study, we applied our surface tension model to the simulation of a spreading droplet on a wall. The simulated dynamic contact angles for some Weber numbers were compared with those measured by Šikalo et al, and they agreed well. Our surface tension model was useful for simulating droplet motion under static and dynamic conditions.

Measurements of the Contact Angles for Various Fluids Which Are Widely Used in the Oilfields to Improve Oil Recovery

2018 ◽  
Author(s):  
M. Elsharafi ◽  
K. Vidal ◽  
R. Thomas
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Interfacial Tension ◽  
Oil Recovery ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Rock Face ◽  
Angle Measurements ◽  
Contact Angle Measurements

Contact angle measurements are important to determine surface and interfacial tension between solids and fluids. A ‘water-wet’ condition on the rock face is necessary in order to extract oil. In this research, the objectives are to determine the wettability (water-wet or oil-wet), analyze how different brine concentrations will affect the wettability, and study the effect of the temperature on the dynamic contact angle measurements. This will be carried out by using the Cahn Dynamic Contact Angle. Analyzer DCA 315 to measure the contact angle between different fluids such as surfactant, alkaline, and mineral oil. This instrument is also used to measure the surface properties such as surface tension, contact angle, and interfacial tension of solid and liquid samples by using the Wilhelmy technique. The work used different surfactant and oil mixed with different alkaline concentrations. Varying alkaline concentrations from 20ml to 1ml were used, whilst keeping the surfactant concentration constant at 50ml.. It was observed that contact angle measurements and surface tension increase with increased alkaline concentrations. Therefore, we can deduce that they are directly proportional. We noticed that changing certain values on the software affected our results. It was found that after calculating the density and inputting it into the CAHN software, more accurate readings for the surface tension were obtained. We anticipate that the surfactant and alkaline can change the surface tension of the solid surface. In our research, surfactant is desirable as it maintains a high surface tension even when alkaline percentage is increased.

Hydrosilation-Cured Poly(dimethylsiloxane) Networks:  Intrinsic Contact Angles via Dynamic Contact Angle Analysis

2003 ◽  
Vol 36 (10) ◽  
pp. 3689-3694 ◽  
Author(s):  
Janelle M. Uilk ◽  
Ann E. Mera ◽  
Robert B. Fox ◽  
Kenneth J. Wynne
Keyword(s):  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Contact Angle Analysis

Rheological and Interfacial Property of Nano-Al with HTPB, GAP and PET

2014 ◽  
Vol 924 ◽  
pp. 170-175 ◽  
Author(s):  
Hui Xiang Xu ◽  
Wen Jing Zhou ◽  
Feng Qi Zhao ◽  
Wei Qiang Pang ◽  
Zhi Hua Sun ◽  
...  
Keyword(s):  
Activation Energy ◽  
Surface Tension ◽  
Contact Angle ◽  
Apparent Viscosity ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Interfacial Property ◽  
Flow Activation Energy ◽  
Flow Activation

Rheological and interfacial property of nanoAl with Hydroxyl-terminated polybutadiene (HTPB), glycidyl azide polymer (GAP) and poly (ethyleneoxide-co-tetrafuran)(PET) were investigated by means of RS-300 rheometer, DCAT21 dynamic contact angle measuring instrument, interface surface tension meter (Germany) and X-ray photoelectron spectroscopy (xps). Rheological properties of three binders and nanoAl/binder suspensions in the mixing ratio of 1:2 were discussed. Results show that Three kinds of binders exhibit pseudoplastic characteristics with the apparent viscosity of less than 3 Pa s,and have weak interaction between molecular chain segment of itself. Within 30~60°C, with temperature increasing, the apparent viscosity of nanoAl suspensions decreases, in which the nanoAl/HTPB and nanoAl/GAP belong to pseudoplastic fluid of sensitive to temperature, with flow activation energy of 38.05 kJ/mol and 52.07 kJ /mol, respectively, but nanoAl/PET belongs to a bingham fluid of sensitive to changes in the shear rate, with flow activation energy of only 1.506 kJ/mol. The contact angles of nanoAl,GAP,HTPB and PET were measured by means of dynamic contact angle/surface tension instrument. The calculated values of adhesion and spread coefficient of nanoAl with binders decrease in the order Wnano-Al/PET>Wnano-Al/GAP>Wnano-Al/HTPB and Snano-Al/PET>Snano-Al/GAP>Snano-Al/HTPB.The results indicate that the interactions of nanoAl with binders decrease in the order nanoAl/PET>nanoAl/GAP>nanoAl/HTPB,which is consistent with the trends of apparent viscosity of the suspensions . Binding energy of Oxygen in nanoAl/HTPB is 532.03 ev,which is bigger than that of nanoAl,and indicate a strong action between nanoAl and HTPB.

PREPARATION AND CHARACTERIZATIONS OF PTFE GRADIENT NANOSTRUCTURE ON SILK FABRIC

2007 ◽  
Vol 14 (04) ◽  
pp. 547-551 ◽  
Author(s):  
F. L. HUANG ◽  
Q. F. WEI ◽  
W. Z. XU ◽  
Q. LI
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Dynamic Contact Angle ◽  
Chemical Properties ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Attenuated Total Reflection ◽  
Silk Fabric ◽  
Water Contact ◽  
Sputter Coating

Superhydrophobic materials have been extensively studied because of their wonderful array of properties and applications. In this study, normal and superhydrophobic surface of silk fabric have been prepared via deposition of different shapes of PTFE nanostructure using magnetron sputter coating. The effects of PTFE sputter coating on surface morphology and surface chemical properties were characterized using atomic force microscopy (AFM) and ATR-FTIR (attenuated total reflection-Fourier transform infrared spectroscopy). The wettability of the fabric was characterized through measuring the surface contact angle by drop shape analysis apparatus and dynamic contact angle by Wilhelmy technique. As evaluated by water contact angle measurements, all the treatments resulted in a significant enhancement in the hydrophobicity of silk fabric, while larger sputtering pressures brought bigger PTFE nanoparticles, which led to higher contact angles. The results have also revealed that alternant working pressures, could bring gradient nanostructures which generated both high contact angle and less contact angle hysteresis.

Effect of Dynamic Contact Angle on Single Bubbles During Nucleate Pool Boiling

2004 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Satish G. Kandlikar
Keyword(s):  
Contact Angle ◽  
Numerical Study ◽  
Removal Rate ◽  
Pool Boiling ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Heated Wall ◽  
Nucleate Pool Boiling ◽  
Static Contact

Nucleate pool boiling at low heat flux is typically characterized by cyclic growth and departure of single vapor bubbles from the heated wall. It has been experimentally observed that the contact angle at the bubble base varies during the ebullition cycle. In the present numerical study, dynamic advancing and receding contact angles obtained from experimental observations are specified at the base of a vapor bubble growing on a wall. The complete Navier-Stokes equations are solved and the liquid-vapor interface is captured using the level-set technique. The effect of dynamic contact angle on the bubble dynamics and vapor removal rate are compared to results obtained with static contact angle. The results show that bubble base exhibits a slip/stick behavior with dynamic contact angle though the overall effect on the vapor removal rate is small. Higher advancing contact angle is found to increase the vapor removal rate.

Nonlinear sloshing in zero gravity

2002 ◽  
Vol 464 ◽  
pp. 365-391 ◽  
Author(s):  
JOHN BILLINGHAM
Keyword(s):  
Contact Angle ◽  
Numerical Solutions ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Lateral Acceleration ◽  
Zero Gravity ◽  
Contact Lines ◽  
Weakly Nonlinear ◽  
Two Dimensional Flow

We study the effect of a time-periodic, lateral acceleration on the two-dimensional flow of a fluid with a free surface subject to surface tension, confined between two plane, parallel walls under conditions of zero gravity. We assume that the velocity of each contact line is a prescribed, single-valued function of the dynamic contact angle between fluid and solid at the wall. We begin by obtaining analytical solutions for the small-amplitude standing waves that evolve when this function is linear, the fluid is inviscid and the lateral acceleration is sufficiently small. This leads to damping of the motion, unless either the contact angles are fixed or the contact lines are pinned. In these cases, we include the effect on the flow of the wall boundary layers, which are the other major sources of damping. We then consider the weakly nonlinear solution of the inviscid problem when the contact angle is almost constant and the external forcing is close to resonance. This solution indicates the possibility of a hysteretic response to changes in the forcing frequency. Finally, we examine numerical solutions of the fully nonlinear, inviscid problem using a desingularized integral equation technique. We find that periodic solutions, chaotic solutions and solutions where the topology of the fluid changes, either through self-intersection or pinch off, are all possible.

The Effects of Asymmetric Micro Ratchets on Dynamic Contact Angle and Pool Boiling Performance

2012 ◽  
Author(s):  
Lance Austin Brumfield ◽  
Sunggook Park
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Pool Boiling ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Equilibrium Contact Angle ◽  
Droplet Impingement ◽  
Receding Contact ◽  
Receding Contact Angle

The dynamic advancing and receding contact angles of 5μl water droplets were experimentally measured via the droplet impingement technique on a polished brass surface, one brass symmetric micro ratchet, and five brass asymmetric micro ratchet samples of varying dimensions. Droplets were released from varying heights (Weber number) and the impacts studied via high speed camera. Equilibrium advancing and receding contact angles were measured by placing a water droplet on the surfaces and tilting it. Contact angle values were then compared to an existing pool boiling model which incorporates the dynamic receding contact angle, surface roughness ratio, and equilibrium contact angle.

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