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

Fujisawa, Kazuo; Yamagata, Takayuki; Fujisawa, Nobuyuki

doi:10.1016/j.anucene.2018.07.008

Cited by 25 publications

(7 citation statements)

References 22 publications

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“…Hence, the smoother the surface the lesser shearing effect, and thus delayed erosion. Moreover, the existence of liquid film on the target surface has shown to have a cushioning effect on liquid impact erosion [107]. This because impact pressure as well as shear damages caused by lateral jetting are greatly reduced by the liquid film [107,108].…”

Section: Effects Of Erosion Parametersmentioning

confidence: 99%

“…Moreover, the existence of liquid film on the target surface has shown to have a cushioning effect on liquid impact erosion [107]. This because impact pressure as well as shear damages caused by lateral jetting are greatly reduced by the liquid film [107,108]. However, according to Shi et al [109], with the progress of damage, the liquid trapped in pits or cracks can be forced to penetrate and cause higher damage than the dry surface.…”

Section: Effects Of Erosion Parametersmentioning

confidence: 99%

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Water Droplet Erosion of Wind Turbine Blades: Mechanics, Testing, Modeling and Future Perspectives

Ibrahim

Medraj

2019

Materials

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The problem of erosion due to water droplet impact has been a major concern for several industries for a very long time and it keeps reinventing itself wherever a component rotates or moves at high speed in a hydrometer environment. Recently, and as larger wind turbine blades are used, erosion of the leading edge due to rain droplets impact has become a serious issue. Leading-edge erosion causes a significant loss in aerodynamics efficiency of turbine blades leading to a considerable reduction in annual energy production. This paper reviews the topic of water droplet impact erosion as it emerges in wind turbine blades. A brief background on water droplet erosion and its industrial applications is first presented. Leading-edge erosion of wind turbine is briefly described in terms of materials involved and erosion conditions encountered in the blade. Emphases are then placed on the status quo of understanding the mechanics of water droplet erosion, experimental testing, and erosion prediction models. The main conclusions of this review are as follow. So far, experimental testing efforts have led to establishing a useful but incomplete understanding of the water droplet erosion phenomenon, the effect of different erosion parameters, and a general ranking of materials based on their ability to resist erosion. Techniques for experimentally measuring an objective erosion resistance (or erosion strength) of materials have, however, not yet been developed. In terms of modelling, speculations about the physical processes underlying water droplet erosion and consequently treating the problem from first principles have never reached a state of maturity. Efforts have, therefore, focused on formulating erosion prediction equations depending on a statistical analysis of large erosion tests data and often with a combination of presumed erosion mechanisms such as fatigue. Such prediction models have not reached the stage of generalization. Experimental testing and erosion prediction efforts need to be improved such that a coherent water droplet erosion theory can be established. The need for standardized testing and data representation practices as well as correlations between test data and real in-service erosion also remains urgent.

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Section: Effects Of Erosion Parametersmentioning

confidence: 99%

Section: Effects Of Erosion Parametersmentioning

confidence: 99%

Water Droplet Erosion of Wind Turbine Blades: Mechanics, Testing, Modeling and Future Perspectives

Ibrahim

Medraj

2019

Materials

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“…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%

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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“…Although when the thin water film sheds off from the compressor blade, it forms larger droplets that are more harmful to the blades, the film itself can dampen the impact energy of the droplets if it stays intact. Fujisawa et al (2018a) recently reported numerical and experimental studies showing that the impacting stress is extremely reduced by the water film when the tests are performed in a static apparatus. The base material under the water film suffers less impact energy compared with the dry surface.…”

Section: Introductionmentioning

confidence: 99%

Experimental and CFD simulation of interactions between water droplets with different surface features to understand water droplet erosion

Jing

Gujba

Medraj

2022

Trans. Can. Soc. Mech. Eng.

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Water droplet erosion (WDE) has received considerable attention in recent years. Different approaches have been proposed to understand WDE and find lasting solutions. Among them is understanding the interaction between the droplet impacts and the target surface especially at the erosion initiation stage. For this reason, this work studies the interactions between water droplets and different surface features to understand WDE. These surface features include flat smooth surface, grooved and porous samples. For the grooved samples, 1 mm and 0.5 mm depth are studied and their water droplet (WDE) erosion performance is evaluated. The 0.5 mm groove shows a longer incubation period than the flat reference sample. This work suggests that thin water film is formed in the groove which aids in dampening the impacts of subsequent water droplets. However, the maximum erosion rate is not affected by introducing these grooves. WDE performance of the porous samples is better than that of the solid material. This is because the porous structure dissipates the impact energy of the water droplets. Simulation results are in agreement with the experimental observations in this work. Furthermore, the simulation showed that the water droplet impacting patterns on different surface features are attributed to the effect of radial and axial airflows.

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

Cited by 25 publications

References 22 publications

Water Droplet Erosion of Wind Turbine Blades: Mechanics, Testing, Modeling and Future Perspectives

Water Droplet Erosion of Wind Turbine Blades: Mechanics, Testing, Modeling and Future Perspectives

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

Experimental and CFD simulation of interactions between water droplets with different surface features to understand water droplet erosion

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