Numerical Analysis of Damping Effect of Liquid Film on Material in High Speed Liquid Droplet Impingement

Sasaki, H.; Ochiai, Naoya; Iga, Yuka

doi:10.5293/ijfms.2016.9.1.057

Cited by 30 publications

(10 citation statements)

References 11 publications

(10 reference statements)

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“…The suppression rate may be modeled by Eq. (22) as in the case of the water-hammer pressure in Fig. 9(b); the fitting result with a = 4.5 and b = 0.22 shows reasonable agreement with the simulation data.…”

Section: Hydrodynamic Stage Of the Impact Dynamics: Shear Flow Forsupporting

confidence: 74%

“…66 When it comes to plotting the maximum wall pressure in the dry case (l = 0) in addition to the wet case (l > 0), the fitting to the linear acoustic theory for the far field is no longer valid, for the maximum wall pressure in the dry case results from the direct contact between the droplet and the wall and thus consists of the near-field contributions. To model the functional dependence of the maximum wall pressure on the film thickness (l ≥ 0), one may use the empirical formula proposed in the previous studies 22,68 :…”

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

confidence: 99%

“…3,16,17 However, this evaluation is insufficient to identify the mechanism of the particle removal. With regard to the study of the droplet impact against a rigid wall, large variety of acoustic and hydrodynamic phenomena have been investigated (e.g., water hammer [18][19][20][21][22] , cavitation [23][24][25] , splashing [26][27][28][29][30][31][32] , side jetting 21,33,34 and rim instability 35,36 ). However, it is challenging to experimentally measure the wall shear flow development and visualize the particle removal.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Hydrodynamic Stage Of the Impact Dynamics: Shear Flow Forsupporting

confidence: 74%

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

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…Fujisawa et al [9] conducted an experimental study on the effect of a liquid film on material under droplet impingement and proposed an equation of the erosion rate considering the effect of the liquid film. We have also numerically demonstrated that the pressure caused by a droplet impingement is damped by the liquid film [10].…”

Section: Introductionmentioning

confidence: 89%

“…Between Fluid and Material. The algorithm of two-way coupled numerical method in fluid/material interface [10] is applied as follows: the pressure and normal stress in the vertical direction on the material surface are obtained by considering the reflection and transmission of pressure and stress waves with acoustic impedance. Nonslip condition is adopted on fluid/ material surface, where the vertical velocity on the boundary surface has values obtained by considering reflection and transmission.…”

Section: Boundarymentioning

confidence: 99%

Numerical Analysis of Influence of Roughness of Material Surface on High-Speed Liquid Droplet Impingement

Sasaki

Iga

2019

Journal of Pressure Vessel Technology

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This study explains why the deep erosion pits are formed in liquid droplet impingement erosion even though the droplets uniformly impinge on the entire material surface. Liquid droplet impingement erosion occurs in fluid machinery on which droplets impinge at high speed. In the process of erosion, the material surface becomes completely roughened by erosion pits. In addition, most material surface is not completely smooth and has some degree of initial roughness from manufacturing and processing and so on. In this study, to consider the influence of the roughness on the material surface under droplet impingement, a numerical analysis of droplets impinging on the material surface with a single wedge and a single bump was conducted with changing offsets between the droplet impingement centers and the roughness centers on each a wedge bottom and a bump top. As results, two mechanisms are predicted from the present numerical results: the erosion rate accelerates and transitions from the incubation stage to the acceleration stage once roughness occurs on the material surface; the other is that deep erosion pits are formed even in the case of liquid droplets impinging uniformly on the entire material surface. . In this study, the locally homogeneous model of compressible gas-liquid two-phase medium with phase changes [13][14][15] is used for the interface capturing method in a droplet interface. The governing equations in the fluid are the continuity and momentum equations, the total energy conservation equation of the gas-liquid mixture phase, and the continuity equation of the gas phase. In this numerical analysis, the continuum surface force model [16] is used in order to

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Damping effect on impact pressure from liquid droplet impingement on wet wall

Fujisawa

Yamagata

Fujisawa

2018

Annals of Nuclear Energy

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Numerical Analysis of Damping Effect of Liquid Film on Material in High Speed Liquid Droplet Impingement

Cited by 30 publications

References 11 publications

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

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

Numerical Analysis of Influence of Roughness of Material Surface on High-Speed Liquid Droplet Impingement

Damping effect on impact pressure from liquid droplet impingement on wet wall

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