Pressure generated at the instant of impact between a liquid droplet and solid surface

Tatekura, Yuki; Watanabe, Masao; Kobayashi, Kazumichi; Sanada, Toshiyuki

doi:10.1098/rsos.181101

Cited by 29 publications

(12 citation statements)

References 55 publications

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“…Here, ρg is the specific weight, t s . is the droplet spreading thickness, F γ is the surface tension force, ∆V is the volume of inflection, P e f f = 1.41ρc 0 v i − p a is effective impact pressure onset of impact, p a is the maximum pressure in the entrapped air and c 0 is the speed of sound [29].…”

Section: Data Availability Statementmentioning

confidence: 99%

Impacting Droplet Can Mitigate Dust from PDMS Micro-Post Array Surfaces

et al. 2021

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In this paper, the impact mechanisms of a water droplet on hydrophobized micro-post array surfaces are examined and the influence of micro-post arrays spacing on the droplet behavior in terms of spreading, retraction, and rebounding is investigated. Impacting droplet behavior was recorded using a high-speed facility and flow generated in the droplet fluid was simulated in 3D geometry accommodating conditions of the experiments. Micro-post arrays were initially formed lithographically on silicon wafer surfaces and, later, replicated by polydimethylsiloxane (PDMS). The replicated micro-post arrays surfaces were hydrophobized through coating by functionalized nano-silica particles. Hydrophobized surfaces result in a contact angle of 153° ± 3° with a hysteresis of 3° ± 1°. The predictions of the temporal behavior of droplet wetting diameter during spreading agree with the experimental data. Increasing micro-post arrays spacing reduces the maximum spreading diameter on the surface; in this case, droplet fluid penetrated micro-posts spacing creates a pinning effect while lowering droplet kinetic energy during the spreading cycle. Flow circulation results inside the droplet fluid in the edge region of the droplet during the spreading period; however, opposing flow occurs from the outer region towards the droplet center during the retraction cycle. This creates a stagnation zone in the central region of the droplet, which extends towards the droplet surface onset of droplet rebounding. Impacting droplet mitigates dust from hydrophobized micro-post array surfaces, and increasing droplet Weber number increases the area of dust mitigated from micro-post arrays surfaces.

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Section: Data Availability Statementmentioning

confidence: 99%

Impacting Droplet Can Mitigate Dust from PDMS Micro-Post Array Surfaces

et al. 2021

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“…The maximum pressure is normalized by that in the dry wall (p max (0) = 22 MPa). According to the work by Tatekura et al (2018), calculation of the water-hammer peak pressure that appears at the point contact of spherical droplet impact requires extremely high spatial/temporal resolutions. 67 In this study, we do not intend to resolve the water-hammer event with finer computational grids;…”

Section: A Acoustic Stage Of the Impact Dynamics: Water-hammer Shockmentioning

confidence: 99%

Simulation of high-speed droplet impact against a dry/wet rigid wall for understanding the mechanism of liquid jet cleaning

Kondo

Ando

2019

Physics of Fluids

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Physical cleaning techniques are of great concern to remove particulate contamination because of their low environmental impact. One of the promising candidates is based on water jets that often involve fission into droplet fragments. Particle removal is believed to be achieved by droplet-impact-induced wall shear flow. Here, we simulate high-speed droplet impact on a dry/wet rigid wall to investigate wall shear flow as well as water hammer after the impact. The problem is modeled by the axisymmetric compressible Navier-Stokes equations and solved by a finite volume method that can capture both shocks and material interface. As an example, we consider the impact of a spherical water droplet (200 µm in diameter) at velocity from 30 to 50 m/s against a dry/wet rigid wall. In our simulation, we can reproduce both acoustic and hydrodynamic events. In the dry wall case, the strong wall shear appears near the moving contact line at the wetted surface. On the other hand, once the wall is covered with the liquid film, the wall shear stress gets weaker as the film thickness increases; the similar trend holds for the water-hammer shock loading at the wall. According to the simulated base flow, we compute hydrodynamic force acting on small particles that are assumed to be attached at the wall, in a one-way-coupling manner. The hydrodynamic force acting on the particles is estimated under Stokes' assumption and compared to particle adhesion of van der Waals type, enabling us to derive a simple criterion of the particle removal.

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“…As shown in Figure 1, the impact of a free waterjet on soft tissue is divided into the following stages: at t = 0, the highspeed waterjet tip contacts the soft tissue surface; from t to t 1 , the shock wave is formed at the contact point and propagates in the water and soft tissue at different speeds, the pressurized water medium is densely populated in the waterjet tip, and the soft tissue is elastically deformed; from t 1 to t 2 , the waterjet stream continues to impact the soft tissue surface to form a new shock wave, because the velocity of the shock wave is much higher than the velocity of the waterjet, the water hammer pressure generated by the impact at its centre is disturbed by the shock wave until the waterjet tip is in complete contact with soft tissue; at t > t 3 the waterjet impact will form a stable Bernoulli stagnation pressure from the dynamic pressure of the waterjet, and the waterjet centre-pressure is significantly reduced. Experimental studies have shown that the water hammer pressure has a short duration of action, on the order of nanoseconds [14], [15].…”

Section: Waterjet Impact a Water Hammermentioning

confidence: 99%

Separation Behaviour Difference Between Gelatin and Porcine Liver Under High-Speed Waterjet Impact

Cao

Zhao

et al. 2019

IEEE Access

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Different from the rigid separation of biological tissue by scalpel, medical waterjet technology utilizes the impact kinetic energy of high-speed waterjet to instantly destroy the surface of biological tissue to achieve better clinical separation effect. Since the gelatin samples are transparent biomaterials, they were taken as the only substitute for soft tissue in experimental studies and observation in the current studies of medical waterjet separation technology, but the mechanical behavioural difference between the two has not been reported. To verify the adaptability of gelatin as a substitute of soft tissue under the impact of high-speed waterjet. Firstly, the dynamic process of impact was described through the energy balance equation. Then, based on the principle of altering a single variable, the difference of damage depth between 8 wt. %, 10 wt. %, and 12 wt. % gelatin samples and porcine liver tissue under various impact pressure, impact distance, and waterjet speed of motion (as opposed to flow velocity) was compared. The results show that the gelatin sample replicates the damage behaviour of porcine liver samples under the specific waterjet impact conditions, and the direction of the waterjet hydraulic power optimisation of the two materials is also consistent: however, due to the different sampling sites and anisotropy of porcine liver samples, the mechanical response of soft tissue under high-speed waterjet impact cannot be fully expressed by gelatin samples. The experimental results can provide support for the further study of medical waterjet separation technology.INDEX TERMS High-speed impact, medical waterjet, separation behavior, surgical instruments, tissue engineering.

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Pressure generated at the instant of impact between a liquid droplet and solid surface

Cited by 29 publications

References 55 publications

Impacting Droplet Can Mitigate Dust from PDMS Micro-Post Array Surfaces

Impacting Droplet Can Mitigate Dust from PDMS Micro-Post Array Surfaces

Simulation of high-speed droplet impact against a dry/wet rigid wall for understanding the mechanism of liquid jet cleaning

Separation Behaviour Difference Between Gelatin and Porcine Liver Under High-Speed Waterjet Impact

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