Experimental and Numerical Framework for Study of Low Velocity Water Droplet Impact Dynamics

2016 ◽  
Author(s):  
B. R. Mitchell ◽  
A. Nassiri ◽  
M. R. Locke ◽  
J. C. Klewicki ◽  
Y. P. Korkolis ◽  
...  
Keyword(s):  
High Velocity ◽  
Water Droplet ◽  
Turbine Blades ◽  
Droplet Impact ◽  
Impact Dynamics ◽  
Water Droplets ◽  
Numerical Predictions ◽  
Starting Point ◽  
The Impact ◽  
Velocity Water

Impacting water droplets are capable of eroding soil, rock, turbine blades and even high speed aircraft. Research has shown that high velocity water droplet impingement onto a solid workpiece can strip paint, remove rust, and serve as a machining operation. This technique is different from waterjet cutting as a train of water droplets are used to transport momentum to a workpiece rather than a continuous jet. Also, no abrasive medium is used which produces an environmentally friendly process. The exploitation of this water droplet impact phenomenon in industrial applications as a means to deform and remove material does not currently exist. If the impact dynamics of water droplets can be understood and controlled, then industries would have the framework upon which they could employ this phenomenon in novel manufacturing equipment. In this paper, as a starting point, the impact force of 2.9mm diameter water droplets impacting at low velocities (∼2m/s) was studied experimentally and numerically. A piezoelectric force sensor was used to measure the transient force of impacting water droplets, while numerical simulations were used to identify the solid-fluid interaction and develop the basis for high velocity (>100m/s) liquid droplet impact dynamics. Agreement was established between experimental observations and numerical predictions for the impact velocities considered.

A Study on Using Plasticity Theory in the Design of the Transit Platform’s Panel

2012 ◽  
Vol 591-593 ◽  
pp. 148-151
Author(s):  
Yuan Yuan Teng ◽  
Da Shan Dong ◽  
Hui Qing Qiu
Keyword(s):  
Design Theory ◽  
Impact Dynamics ◽  
Practical Situation ◽  
Theoretical Derivation ◽  
Container Crane ◽  
Starting Point ◽  
Reference Design ◽  
The Impact ◽  
Energy Law ◽  
Full Consideration

Taking the limit intensity as a starting point, a plasticity design theory is introduced in the design of the transit platform’s panel of double trolley quayside container crane for replacing elasticity design theory as a conventional method. As to the impact dynamics issue, the study gives a theoretical derivation based on the energy law as well as a verification of the experiments of the lockpins’ falling , and uses simulations with Ansys/Ls-dyna condition. Combining the above three aspects, the results prove to be correct. Given the limitations and requirements of the practical situation and the standards, a reasonable design is offered. Through full consideration, it provides the value of the experience for future reference design and should be widely extended to use.

The brittle fracture of solids by liquid impact, by solid impact, and by shock

1964 ◽  
Vol 282 (1390) ◽  
pp. 331-352 ◽  
Keyword(s):  
Surface Wave ◽  
High Velocity ◽  
High Speed ◽  
Turbine Blades ◽  
Explosive Loading ◽  
Back Surface ◽  
High Speed Photography ◽  
Liquid Mass ◽  
Liquid Impact ◽  
The Impact

The type of stress pulse produced when a liquid mass strikes a solid at high velocity is first examined. Compressible behaviour, giving rise to a sharp peak of pressure, is found to occur in the initial stages of the impact. The duration of this peak depends on the dimensions and impact velocity of the liquid mass, and also on the compressible wave velocity for the liquid. A comparison is made with pulses produced by solid/solid impact and by the detonation of small quantities of explosive. Both the high-speed liquid impact and the explosive loading give intense pulses of duration only a few microseconds. A solid/solid impact has, by comparison, a much longer impact time of the order of hundreds of microseconds. The fracture of glasses and hard polymers using these three types of loading is described. The development of fracture is followed by high-speed photography. Differences in the modes of fracture are attributed to variations in the shape and duration of the applied stress pulses. Short circumferential fractures produced around the loaded area in liquid impact and explosive loading are shown to be initiated by the Rayleigh surface wave at points where flaws existed. More complex fracture patterns on the front surfaces of plates are due to the reinforcement of the surface wave with components of stress waves reflected from the back surface. A combination of impact loading and etching makes it possible to investigate the distribution and depths of flaws, their role in the fracture process, and the effect which etching has upon them. The observation on the deformation produced in solids by liquid impact has practical significance in the problem of supersonic aircraft flying through rain and in the erosion of turbine blades moving at high velocity through wet steam.

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

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 157 ◽  
Author(s):  
Mohamed Elhadi Ibrahim ◽  
Mamoun Medraj
Keyword(s):  
Wind Turbine ◽  
Water Droplet ◽  
Prediction Models ◽  
Experimental Testing ◽  
Turbine Blades ◽  
Leading Edge ◽  
Droplet Impact ◽  
Wind Turbine Blades ◽  
Water Droplet Erosion ◽  
Erosion Prediction

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.

scholarly journals High-Velocity Microsprays Enhance Antimicrobial Activity in Streptococcus mutans Biofilms

2016 ◽  
Vol 95 (13) ◽  
pp. 1494-1500 ◽  
Author(s):  
S. Fabbri ◽  
D.A. Johnston ◽  
A. Rmaile ◽  
B. Gottenbos ◽  
M. De Jager ◽  
...  
Keyword(s):  
Streptococcus Mutans ◽  
High Velocity ◽  
Antimicrobial Agents ◽  
Cetylpyridinium Chloride ◽  
Complex Structure ◽  
Impact Angle ◽  
Shear Stresses ◽  
Bacteria Killing ◽  
The Impact ◽  
Velocity Water

Streptococcus mutans in dental plaque biofilms play a role in caries development. The biofilm’s complex structure enhances the resistance to antimicrobial agents by limiting the transport of active agents inside the biofilm. The authors assessed the ability of high-velocity water microsprays to enhance delivery of antimicrobials into 3-d-old S. mutans biofilms. Biofilms were exposed to a 90° or 30° impact, first using a 1-µm tracer bead solution (109 beads/mL) and, second, a 0.2% chlorhexidine (CHX) or 0.085% cetylpyridinium chloride (CPC) solution. For comparison, a 30-s diffusive transport and simulated mouthwash were also performed. Confocal microscopy was used to determine number and relative bead penetration depth into the biofilm. Assessment of antimicrobial penetration was determined by calculating the killing depth detected by live/dead viability staining. The authors first demonstrated that the microspray was able to deliver significantly more microbeads deeper in the biofilm compared with diffusion and mouthwashing exposures. Next, these experiments revealed that the microspray yielded better antimicrobial penetration evidenced by deeper killing inside the biofilm and a wider killing zone around the zone of clearance than diffusion alone. Interestingly the 30° impact in the distal position delivered approximately 16 times more microbeads and yielded approximately 20% more bacteria killing (for both CHX and CPC) than the 90° impact. These data suggest that high-velocity water microsprays can be used as an effective mechanism to deliver microparticles and antimicrobials inside S. mutans biofilms. High shear stresses generated at the biofilm-burst interface might have enhanced bead and antimicrobial delivery inside the remaining biofilm by combining forced advection into the biofilm matrix and physical restructuring of the biofilm itself. Further, the impact angle has potential to be optimized both for biofilm removal and active agents’ delivery inside biofilm in those protected areas where some biofilm might remain.

scholarly journals Droplet impact on flowing liquid films with inlet forcing: the splashing regime

Soft Matter ◽  
2017 ◽  
Vol 13 (41) ◽  
pp. 7473-7485 ◽  
Author(s):  
Idris T. Adebayo ◽  
Omar K. Matar
Keyword(s):  
Liquid Films ◽  
Drop Impact ◽  
Droplet Impact ◽  
Impact Dynamics ◽  
Spatial Structures ◽  
P Waves ◽  
Flowing Liquid ◽  
The Impact

Waves! Spatial structures on flowing liquid films contribute immensely to drop impact dynamics and notably alter the impact outcomes.

Water Droplet Impact Dynamics at Icing Conditions with and without Superhydrophobicity

2012 ◽  
Author(s):  
Yong Han Yeong ◽  
Rafael Mudafort ◽  
Adam Steele ◽  
Ilker Bayer ◽  
Eric Loth ◽  
...  
Keyword(s):  
Water Droplet ◽  
Droplet Impact ◽  
Impact Dynamics

The Impact of Excitation and Mode Shape on Non-Linear Blade Vibrations

2020 ◽  
Author(s):  
Johannes Linhard ◽  
Andreas Hartung ◽  
Stefan Schwarz ◽  
Hans-Peter Hackenberg ◽  
Mateusz Sienko
Keyword(s):  
Mode Shape ◽  
Optical Measurement ◽  
Turbine Blades ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Vibration Measurement ◽  
Numerical Predictions ◽  
Non Linear ◽  
Strain Gauge Measurements ◽  
The Impact

Abstract Recently, reliable non-linear dynamic solvers for the analysis of frictionally coupled turbine blades have been developed which are based on either Higher Harmonic Balance Method or Non-linear Modal Analysis. One of these tools is OrAgL which was developed by Institute of Dynamics of Vibrations (Leibniz University of Hannover) and Institute of Aircraft Propulsion Systems (University of Stuttgart). In [1], the rig and engine validation results of with OrAgL performed forced response analyses have been published: The main aim of this paper was the comparison of non-linear numerical predictions (amplitude, frequencies) with the blade-to-blade averaged values of optical measurement results obtained using MTU’s non-contact vibration measurement system for shrouded turbine blades (BSSM-T). Detailed analyses and validations performed over the last two years showed several novel aspects of validation such as the comparison with strain gauge measurements. Moreover, a better understanding of the impact of excitation (magnitude and load distribution over the airfoil) as well as of the impact of the mode shape on the formation of saturation regimes is now possible. The results obtained from the analyses of real turbine blades are presented in this work.

Damage Analysis of Thermal Barrier Coatings Subjected to a High-Velocity Impingement of a Solid Sphere

2019 ◽  
Vol 827 ◽  
pp. 349-354
Author(s):  
Kiyohiro Ito ◽  
Fei Gao ◽  
Masayuki Arai
Keyword(s):  
Gas Turbine ◽  
Impact Velocity ◽  
Thermal Barrier Coatings ◽  
High Velocity ◽  
Turbine Blades ◽  
Interfacial Crack ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Wide Range ◽  
The Impact

A delamination of thermal barrier coatings (TBC) applied to turbine blades in gas turbine could be caused by a high-velocity impingement of various foreign objects. It is important to accurately predict the size of interfacial crack for safety operation of gas turbine. In this study, in order to establish a practical equation for prediction of the length of interfacial crack, a high velocity impingement test and a finite element analysis (FEA) based on a cohesive model were conducted. As the result, the length of interfacial crack is linearly increased with the impact velocity. In addition, it was confirmed that it was accurately estimated by the FEA. The equation for prediction of the length of interfacial crack was formulated based on these results and the energy conservation before and after impingement. Finally, the applicability of the equation was demonstrated in a wide range of impact velocity through a comparison with the experimental results.

Boiling during high-velocity impact of water droplets on a hot stainless steel surface

2006 ◽  
Vol 462 (2074) ◽  
pp. 3115-3131 ◽  
Author(s):  
Navid Z Mehdizadeh ◽  
Sanjeev Chandra
Keyword(s):  
Stainless Steel ◽  
Substrate Temperature ◽  
Impact Velocity ◽  
High Velocity ◽  
Steel Surface ◽  
Stainless Steel Surface ◽  
High Velocity Impact ◽  
Water Droplets ◽  
Velocity Impact ◽  
The Impact

High-velocity impact of water droplets (0.55 mm diameter) on a heated stainless steel surface was photographed. To achieve high impact velocities, the test surface was mounted on the rim of a rotating flywheel, giving linear velocities of up to 50 m s −1 . Two cartridge heaters were inserted in the substrate and used to vary substrate temperature. A charge coupled device (CCD) video camera was used to photograph droplets impinging on the substrate. To photograph different stages of droplet impact, the ejection of a single droplet was synchronized with the position of the rotating flywheel and triggering of the camera. Substrate temperature was varied from 100 to 240 °C and the impact velocity from 10 to 30 m s −1 . High-resolution photographs were taken of vapour bubbles nucleating sites inside the thin liquid films produced by spreading droplets. An analytical expression was derived for the amount of superheat required for vapour bubble nucleation as a function of the impact velocity. For a given surface roughness, the amount of superheat needed decreased with impact velocity, which agreed with experimental results. For a fixed impact velocity, the maximum extent of droplet spread increased with substrate temperature.

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