scholarly journals State of the art in cavitation erosion studies

2021 ◽  
Vol 1 (395) ◽  
pp. 13-34
Author(s):  
A. Pustoshny ◽  
Keyword(s):  
Cavitation Erosion ◽  
Experimental Studies ◽  
Full Scale ◽  
Blade Surface ◽  
Shot Blasting ◽  
Cavitation Damage ◽  
Cavitation Bubbles ◽  
Cumulative Jets ◽  
Computer Based ◽  
Propeller Blades

Object and purpose of research. This paper discusses cavitation erosion on propeller blades. The purpose of this work is to review and analyse modern studies on cavitation erosion, as well as to apply these research results for better under-standing of cavitation damage risk on full-scale propellers. Materials and methods. The paper reviews recent studies on cavitation erosion, as well as the author’s own findings in cavitation erosion on full-scale steel propellers, analyzing the energy needed to create cavitation damage of recorded size. This energy was calculated as per the model based on the results of metallurgical studies discussing the effect of shot blasting upon steel properties. Comparison of these results with those obtained as per classic formulae for the collapse energy of cavita-tion bubble made it possible to estimate the conditions of cavitation erosion on propeller blades. Main results. The review of recent studies on cavitation erosion has shown that current progress in the technologies of experimental studies and computer-based simulations made it possible to considerably improve the knowledge about cavitation erosion process as compared to the level of the 20th century. This review shows that cavitation erosion studies followed three practically independent paths: experimental studies and computer-based simulation of flow around propeller blades with locali-zation of peaks for one or several criteria reflecting the intensity of cavitation energy fluctuations; the studies intended to esti-mate the pressure exerted by collapsing cavitation bubbles and emerging cumulative jets; and finally, the studies on the proper-ties of materials affected by cumulative jets and collapsing bubbles. At this point, it would be practicable to merge these three paths using the results of full-scale cavitation erosion analysis for propellers. KSRC findings in cavitation damage of full-scale steel propeller has shown that cavitation damage recorded in these studies might occur due to a certain combination between the required energy, bubble-blade interaction pressure and the size of affect-ed area on steel blade surface, and this combination, in its turn, might take place when cavitation bubbles consisting of vapour fraction with partial air content hit the blade surface and collapse. Conclusion. This paper shows the capabilities of modern research methods in obtaining new data on the inception mecha-nism of cavitation erosion. Still, to develop the methods for prediction of cavitation erosion (in particular, on propellers), it is necessary to merge the results obtained in different branches of cavitation studies. The basis for this merging could become a power-based analysis of cavitation processes, with help of the cavitation erosion model suggested in this paper and based on the similarity between cavitation erosion and shot-blasting.

scholarly journals Mitigating cavitation erosion using biomimetic gas-entrapping microtextured surfaces (GEMS)

2020 ◽  
Vol 6 (13) ◽  
pp. eaax6192 ◽  
Author(s):  
Silvestre Roberto Gonzalez-Avila ◽  
Dang Minh Nguyen ◽  
Sankara Arunachalam ◽  
Eddy M. Domingues ◽  
Himanshu Mishra ◽  
...  
Keyword(s):  
Solid Surface ◽  
Surface Hardening ◽  
High Speed ◽  
Cavitation Erosion ◽  
Flow Problem ◽  
Vapor Bubbles ◽  
Cavitation Damage ◽  
Cavitation Bubbles ◽  
Microtextured Surfaces ◽  
High Speed Flows

Cavitation refers to the formation and collapse of vapor bubbles near solid boundaries in high-speed flows, such as ship propellers and pumps. During this process, cavitation bubbles focus fluid energy on the solid surface by forming high-speed jets, leading to damage and downtime of machinery. In response, numerous surface treatments to counteract this effect have been explored, including perfluorinated coatings and surface hardening, but they all succumb to cavitation erosion eventually. Here, we report on biomimetic gas-entrapping microtextured surfaces (GEMS) that robustly entrap air when immersed in water regardless of the wetting nature of the substrate. Crucially, the entrapment of air inside the cavities repels cavitation bubbles away from the surface, thereby preventing cavitation damage. We provide mechanistic insights by treating the system as a potential flow problem of a multi-bubble system. Our findings present a possible avenue for mitigating cavitation erosion through the application of inexpensive and environmentally friendly materials.

Cavitation Erosion Damage in Engine Bearings: Theory and Practice

1980 ◽  
Vol 102 (4) ◽  
pp. 847-857 ◽  
Author(s):  
D. R. Garner ◽  
R. D. James ◽  
J. F. Warriner
Keyword(s):  
Cavitation Erosion ◽  
Pressure Rise ◽  
Pressure Profile ◽  
Theory And Practice ◽  
Test Facility ◽  
Cavitation Damage ◽  
Erosion Damage ◽  
Oil Film ◽  
Bearing Materials ◽  
Computer Based

Cavitation erosion damage in engine bearings has assumed increasing importance during the past 5–10 years, probably as a result of the design trends towards higher rotational speeds, and, in some cases, higher rates of change of cylinder pressure rise. In many instances the damage is merely cosmetically undesirable, and of only minor functional significance; this is particularly so when the bearing is overlay plated. In more extreme cases extensive loss of lining material will result, and the consequential adverse effects on oil film conditions will reduce reliability and life of the bearings and associated parts. This paper presents a general background to cavitation erosion damage and examples of specific forms of this type of damage in plain bearings are given. A number of commonly applied palliatives and their effectiveness, based on engine experience, are discussed. A description of computer-based methods for predicting crankshaft journal locus, oil film pressure profile, and film extent is provided. An attempt has been made to rationalize several typical forms of cavitation damage on the basis of the theoretical model. An ultrasonic vibratory test facility used by the authors to determine the relative erosion resistance of the more commonly used bearing materials is described, and results presented.

Computational and experimental studies of the strength of full-scale samples of pipes with defects "metal loss" and "dent with groove"

2020 ◽  
Vol 10 (3) ◽  
pp. 226-233
Author(s):  
Dmitry A. Neganov ◽  
◽  
Victor M. Varshitsky ◽  
Andrey A. Belkin ◽  
◽  
...  
Keyword(s):  
Internal Pressure ◽  
Experimental Studies ◽  
Full Scale ◽  
The Other ◽  
Metal Loss ◽  
Calculation Methods ◽  
Reliable Operation ◽  
Sufficient Stability ◽  
Comparative Results ◽  
The Moment

The article contains the comparative results of the experimental and calculated research of the strength of a pipeline with such defects as “metal loss” and “dent with groove”. Two coils with diameter of 820 mm and the thickness of 9 mm of 19G steel were used for full-scale pipe sample production. One of the coils was intentionally damaged by machining, which resulted in “metal loss” defect, the other one was dented (by press machine) and got groove mark (by chisel). The testing of pipe samples was performed by applying static internal pressure to the moment of collapse. The calculation of deterioration pressure was carried out with the use of national and foreign methodical approaches. The calculated values of collapsing pressure for the pipe with loss of metal mainly coincided with the calculation experiment results based on Russian method and ASME B31G. In case of pipe with dent and groove the calculated value of collapsing pressure demonstrated greater coincidence with Russian method and to a lesser extent with API 579/ASME FFS-1. In whole, all calculation methods demonstrate sufficient stability of results, which provides reliable operation of pipelines with defects.

CREATING A WORKING MODEL OF A DRIVERLESS AIRFIELD TOW TRUCK

2021 ◽  
Vol 2021 (10) ◽  
pp. 45-52
Author(s):  
Denis D'yakov ◽  
Iskander Valiulin ◽  
Dmitriy Lihovidov ◽  
Aleksey Velikanov
Keyword(s):  
Research Methods ◽  
Economic Efficiency ◽  
Experimental Studies ◽  
Field Tests ◽  
Climatic Conditions ◽  
Full Scale ◽  
Support Surface ◽  
Reliable Operation ◽  
Working Model ◽  
Full Scale Tests

The purpose of the research in this paper is to develop a promising airfield driverless tow truck to increase the economic efficiency of aircraft towing facilities, including unmanned aircrafts as well as to ensure reliable operation in various climatic conditions. The research methods include the analysis of the experience of using such driverless airfield tow trucks abroad, the theory of calculating traction and speed indicators and experimental studies conducted during the creation and study of field tests of devices used to load the driving wheels of a tractor. To achieve the goal, the configuration of the structure being designed and its intended composition are determined analytically. The operation of the designed device in the traction mode is considered, and the characteristic of calculating its indicators when moving along the support surface is presented. The presented material briefly illustrates the process from creating a model of a driverless airfield tow truck to the created design of an existing sample, which will later be used to conduct its full-scale tests and a comprehensive assessment of its strength traction and speed characteristics.

scholarly journals The appliance of prefabricated soil-cement slabs processed with a hydrophobizing material for the road construction

2018 ◽  
Vol 196 ◽  
pp. 04026
Author(s):  
Sergey Sannikov ◽  
Sergey Kuyukov ◽  
Alexey Zamyatin ◽  
Alexandr Zhigailov
Keyword(s):  
Crack Formation ◽  
Experimental Studies ◽  
Road Construction ◽  
Full Scale ◽  
Complex Method ◽  
The Road ◽  
Soil Cement ◽  
Cement Mixture ◽  
Scale Experiment

The paper presents a complex method for increasing water resistance and reducing crack formation by using a prefabricated foundation of soil-cement slabs with surface processing with a hydrophobizing material on basis of organosilicon compounds. Theoretical, laboratory and full-scale experimental studies were made. Theoretical studies are based on the substantiation of the geometric parameters of the slab in order to exclude the probability of its destruction under its own weight during building and installation works. The result of the first stage of laboratory studies is the determination of the optimum composition of soil-cement mixture in order to achieve a grade of strength M20. At the second stage, the effectiveness of the influence of hydrophobizing materials "Tiprom U" and "Penetron-Admix" on water absorption and compressive strength of soil-cement was determined. The final stage of the research was a full-scale experiment. In the factory environment, soil-cement slabs were manufactured in metal forms. Based on the results of the research, conclusions about the effectiveness of this complex method were made. The use of soil-cement slabs allows reducing crack formation, as well as to work all year round due to manufacturing and surface treatment of slabs in the factory conditions.

Man-Computer Communication Techniques: Two Experiments

1967 ◽  
Vol 9 (6) ◽  
pp. 521-528 ◽  
Author(s):  
Robert T. Root ◽  
Robert Sadacca
Keyword(s):  
Image Interpretation ◽  
Experimental Studies ◽  
Data Entry ◽  
Aerial Imagery ◽  
Report Generation ◽  
Computer Communication ◽  
Communication Techniques ◽  
Detection And Identification ◽  
Report Data ◽  
Computer Based

Two experimental studies are reported that were intended to evaluate alternative man-computer communication techniques within the context of a computer-based image interpretation facility. The first experiment, comparing five different data entry procedures, indicated that, although a procedure requiring the interpreter to enter report data directly using a teletype keyboard resulted in the shortest overall throughput time, a procedure involving message composition by the image interpreter with subsequent transcription by a communicator minimizes the time spent by the interpreter in report generation and maximizes the time available for the detection and identification of targets on aerial imagery. The second experiment evaluating alternative word form-data entry format combinations, showed no differences among the six combinations studied.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The collapse of cavitation bubbles and the pressures thereby produced against solid boundaries

1966 ◽  
Vol 260 (1110) ◽  
pp. 221-240 ◽  
Keyword(s):  
Cavitation Erosion ◽  
Experimental Information ◽  
Liquid Jets ◽  
Steam Turbines ◽  
Jet Formation ◽  
Cavitation Damage ◽  
Cavity Collapse ◽  
New Ideas ◽  
The Impact ◽  
Shape Changes

Our object is to present a broad review of this subject as a branch of hydrodynamics, referring both to the well known ‘implosion’ mechanism first analysed by Lord Rayleigh and, more particularly, to the recently perceived possibility that effects of equally great violence, such as to damage solid boundaries, may arise through the impact of liquid jets formed by collapsing cavities. In §2 a few practical facts about cavitation damage are recalled by way of background, and then in §3 the significance of available theoretical and experimental information about cavity collapse is discussed. The main exposition of new ideas is in §4, which is a review of the factors contributing to shape changes and eventual jet formation by collapsing cavities. Finally, in §5, some new experimental observations on the unsymmetrical collapse of vapour-filled cavities are presented.

Experimental Studies of Full-Scale Posttensioned Steel Connections

2005 ◽  
Vol 131 (3) ◽  
pp. 438-448 ◽  
Author(s):  
Maria M. Garlock ◽  
James M. Ricles ◽  
Richard Sause
Keyword(s):  
Experimental Studies ◽  
Full Scale ◽  
Steel Connections
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