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 - Shockwaves from cavity collapse

1966 ◽  
Vol 260 (1110) ◽  
pp. 241-244 ◽  
Keyword(s):  
Spherical Shape ◽  
Solid Surfaces ◽  
Solid Boundary ◽  
Physical Situation ◽  
Steam Turbines ◽  
Jet Formation ◽  
Cavity Collapse ◽  
Peak Pressures ◽  
The Impact

The determination of the stresses produced by cavity collapse has been of interest since Rayleigh’s discussion of the problem. One theoretical calculation relating to this problem is the magnitude of the pressure pulse which is radiated when a spherical bubble collapses and rebounds in a liquid. A calculation of this kind has been made although it was necessary to idealize the physical situation. The peak pressures predicted by this treatment were of the order of some thousands of atmospheres and could, therefore, furnish a mechanism for the damage of solid surfaces. Since these peak pressures decrease rapidly with distance from the centre of the bubble, the solid boundary must be in the immediate neighbourhood of the bubble in order that damage may be produced by this mechanism. In this situation spherical collapse or rebound cannot be expected to take place. An additional disturbance from spherical symmetry arises because the spherical shape is unstable. There is now both theoretical and experimental evidence that jet formation may develop from this unstability, and could under suitable conditions give rise to cavitation damage. This evidence is briefly discussed.

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.

scholarly journals Transient Process and Micro-mechanism of Hydrofoil Cavitation Collapse

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1387
Author(s):  
Yuanyuan Zhao ◽  
Qiang Fu ◽  
Rongsheng Zhu ◽  
Guoyu Zhang ◽  
Chuan Wang ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Attack Angle ◽  
Solid Surfaces ◽  
Underwater Robots ◽  
Factors Affecting ◽  
Cavity Collapse ◽  
Hydraulic Machinery ◽  
Pressure Peak ◽  
The Impact

Cavitation will cause abnormal flow, causing a series of problems such as vibration, noise, and erosion of solid surfaces. In severe cases, it may even destroy the entire system. Cavitation is a key problem to be solved for hydraulic machinery and underwater robots, and the attack angle is one of the most important factors affecting the cavitation. In order to systematically study the impact of the attack angle on the hydrofoil cavitation, the hydrofoils of NACA 4412 with different attack angles were selected to study the collapse process and hydraulic characteristics such as pressure, velocity, vortex, and turbulent kinetic energy during cavitation. The results showed that when the cavitation number was the same, the process of cavity collapse was greatly affected by the attack angle. The length of the cavity collapse area was positively correlated with the attack angle. As the attack angle increased, the volume of the falling bubbles increased, resulting in a larger pressure peak caused by the collapse of bubbles. Moreover, the pressure gradient near the collapse point changed more drastically, thereby affecting the growth of attached cavitation. The fluctuation range of vortex core and turbulent kinetic energy also increased with increasing the attack angle.

scholarly journals Generation and breakup of Worthington jets after cavity collapse. Part 1. Jet formation

2010 ◽  
Vol 663 ◽  
pp. 293-330 ◽  
Author(s):  
STEPHAN GEKLE ◽  
J. M. GORDILLO
Keyword(s):  
Flow Structure ◽  
High Speed ◽  
Liquid Surface ◽  
Circular Disk ◽  
Boundary Integral ◽  
Analytical Modelling ◽  
Acceleration Region ◽  
Jet Formation ◽  
Cavity Collapse ◽  
The Impact

At the beginning of the last century Worthington and Cole discovered that the high-speed jets ejected after the impact of an axisymmetric solid on a liquid surface are intimately related to the formation and collapse of an air cavity created in the wake of the impactor. In this paper, we combine detailed boundary-integral simulations with analytical modelling to describe the formation of such Worthington jets after the impact of a circular disk on water. We extend our earlier model in Gekle et al. (Phys. Rev. Lett., vol. 102, 2009a, 034502), valid for describing only the jet base dynamics, to describe the whole jet. We find that the flow structure inside the jet may be divided into three different regions: the axial acceleration region, where the radial momentum of the incoming liquid is converted to axial momentum; the ballistic region, where fluid particles experience no further acceleration and move constantly with the velocity obtained at the end of the acceleration region; and the jet tip region, where the jet eventually breaks into droplets. From our modelling of the ballistic region we conclude that, contrary to the case of other physical situations where high-speed jets are also ejected, the types of Worthington jets studied here cannot be described using the theory of hyperbolic jets of Longuet-Higgins (J. Fluid Mech., vol. 127, 1983, p. 103). Most importantly, we find that the velocity and the shape of the ejected jets can be well predicted at any instant in time with the only knowledge of quantities obtained before pinch-off occurs. This fact allows us to provide closed expressions for the jet velocity and the sizes of the ejected droplets as a function of the velocity and the size of the impactor. We show that our results are also applicable to Worthington jets emerging after the collapse of a bubble growing from an underwater nozzle, although this system creates thicker jets than the disk impact.

Assessment of sensitivity of the efficiency of regional tax spending towards investment attractiveness of the types of economic activity carried out by the residents of advanced development territory

2020 ◽  
pp. 98-110
Author(s):  
Evgeniya Mikhailovna Popova ◽  
Guzel Mukhtarovna Guseinova ◽  
Sergei Borisovich Milov
Keyword(s):  
Economic Activity ◽  
Socioeconomic Development ◽  
Federal District ◽  
Tax Incentives ◽  
Capital Investments ◽  
The Subject ◽  
Investment Process ◽  
The Impact ◽  
Advanced Development

The deficit of subnational budgets and deceleration capital investments in multiple Russian regions increase the relevance of research aimed at improvement of tax incentivizing practice of the regional investment process. The studies focused on determination of the impact of socioeconomic and institutional factors upon the efficiency of investment tax expenses obtained wide circulation within the foreign scientific literature. The subject of this article is the assessment of sensitivity of the efficiency of regional tax expanses towards investment attractiveness of the types of economic activity carried out by the residents of territories of advanced socioeconomic development, created in the subjects of Far Easter Federal District. The scientific novelty and practical values of this research consists in substantiation of the reasonableness of assessment of investment attractiveness of the types of economic activity that are stimulated by tax incentives. Methodology for assessing investment attractiveness is proposed and tested. The conclusion is made that in case of low investment attractiveness of the type of economic activity, which was planned to support by tax incentives, it is required to conduct and additional analysis to avoid unjustified tax expanses.

Method development for the determination of textural properties of sugar beet roots

2019 ◽  
pp. 392-400 ◽  
Author(s):  
Gunnar Kleuker ◽  
Christa M. Hoffmann
Keyword(s):  
Sugar Beet ◽  
Compression Test ◽  
Storage Period ◽  
Textural Properties ◽  
Small Sample ◽  
Root Tip ◽  
Flexural Test ◽  
Sample Distribution ◽  
The Impact

The harvest of sugar beet leads to root tip breakage and surface damage through mechanical impacts, which increase storage losses. For the determination of textural properties of sugar beet roots with a texture analyzer a reliable method description is missing. This study aimed to evaluate the impact of washing, soil tare, storage period from washing until measurement, sample distribution and number of roots on puncture and compression measurements. For this purpose, in 2017 comprehensive tests were conducted with sugar beet roots grown in a greenhouse. In a second step these tests were carried out with different Beta varieties from a field trial, and in addition, a flexural test was included. Results show that the storage period after washing and the sample distribution had an influence on the puncture and compression strength. It is suggested to wash the roots by hand before the measurement and to determine the strength no later than 48 h after washing. For reliable and comparable results a radial distribution of measurement points around the widest circumference of the root is recommended for the puncture test. The sample position of the compression test had an influence on the compressive strength and therefore, needs to be clearly defined. For the puncture and the compression test it was possible to achieve stable results with a small sample size, but with increasing heterogeneity of the plant stand a higher number of roots is required. The flexural test showed a high variability and is, therefore, not recommended for the analysis of sugar beet textural properties.

Multiple interactions in riverine biofilms - surfactant adsorption, bacterial attachment and biodegradation

1995 ◽  
Vol 31 (1) ◽  
pp. 61-70 ◽  
Author(s):  
Graham F. White
Keyword(s):  
Organic Pollutants ◽  
Bacterial Attachment ◽  
Solid Surfaces ◽  
Sediment Surface ◽  
Liquid Interfaces ◽  
Polluted Soils ◽  
Biofilm Bacteria ◽  
The Impact ◽  
Multiple Interactions

Many organic pollutants, especially synthetic surfactants, adsorb onto solid surfaces in natural and engineered aquatic environments. Biofilm bacteria on such surfaces make major contributions to microbial heterotrophic activity and biodegradation of organic pollutants. This paper reviews evidence for multiple interactions between surfactants, biodegradative bacteria, and sediment-liquid interfaces. Biodegradable surfactants e.g. SDS, added to a river-water microcosm were rapidly adsorb to sediment surface and stimulated the indigenous bacteria to attach to the sediment particles. Recalcitrant surfactants and non-surfactant organic nutrients did not stimulate attachment Attachment of bacteria was maximal when biodegradation was fastest, and was reversed when biodegradation was complete. Dodecanol, the primary product of SDS-biodegradation, markedly stimulated attachment. When SDS was added to suspensions containing sediment and either known degraders or known non-degraders, only the degraders became attached, and attachment accelerated surfactant biodegradation to dodecanol. These cyclical cooperative interactions have implications for the design of biodegradability-tests, the impact of surfactant adjuvants on biodegradability of herbicides/pesticides formulated with surfactants, and the role of surfactants used to accelerate bioremediation of hydrocarbon-polluted soils.

Development and Validation of an LC-MS/MS Method for Simultaneous Determination of Canagliflozin and Metformin HCl in Rat Plasma and its Application

2020 ◽  
Vol 16 (6) ◽  
pp. 752-762
Author(s):  
Vivek Nalawade ◽  
Vaibhav A. Dixit ◽  
Amisha Vora ◽  
Himashu Zade
Keyword(s):  
Internal Standard ◽  
Rat Plasma ◽  
Precipitation Method ◽  
Herbal Extracts ◽  
One Step ◽  
Precision And Accuracy ◽  
Development And Validation ◽  
The Impact ◽  
Metformin Hcl

Background: Food and herbal extracts rich in Quercetin (QRT) are often self-medicated by diabetics and can potentially alter the pharmacokinetics (PK) of Metformin HCl (MET) and Canagliflozin (CNG) leading to food or herb-drug interactions and reduced therapeutic efficacy. However, the impact of these flavonoids on the pharmacokinetic behaviour of MET and CNG is mostly unknown. Methods: A simple one-step protein precipitation method was developed for the determination of MET and CNG from rat plasma. The mobile phase chosen was MeOH 65% and 35% water containing 0.1% formic acid at a flow rate of 1mL/min. Results: The retention time of MET, internal standard (Valsartan) and CNG was 1.83, 6.2 and 8.2 min, respectively. The method was found to be linear in the range of 200 - 8000 ng/mL for CNG and 100 = 4000 ng/ml for MET. Precision and accuracy of the method were below 20% at LLOQ and below 15% for LQC, MQC, and HQC. Conclusion: The method was successfully applied for the determination of PK of MET and CNG by using 100 μL of rat plasma. QRT co-administration affects the PK parameters of MET and CNG. This alteration in PK parameters might be of significant use for clinicians and patients.

The Microeconomics of Product Innovation

2018 ◽  
Author(s):  
Paul Stoneman ◽  
Eleonora Bartoloni ◽  
Maurizio Baussola
Keyword(s):  
Product Innovation ◽  
New Products ◽  
Goods And Services ◽  
Product Innovations ◽  
Microeconomic Analysis ◽  
Prime Objective ◽  
Price Measurement ◽  
The Impact

The prime objective of this book is the use microeconomic analysis to guide and provide insight into the generation and adoption of new products. Taking an approach that uses minimal formal mathematics, the volume initially addresses questions of definitions, sources, and extent of product innovation, differentiating between goods and services; hard and soft innovations; horizontal and vertical innovations; original, new to market, and new to firm innovations. The sources of product innovations (e.g. R&D, design, and creativity) are explored empirically, and the extent of such innovations is then pursued using survey and other data. Three chapters are devoted to the theoretical analysis of the demand for and supply of new products and to the determination of firms’ decisions to undertake product innovation. Later chapters encompass empirical evidence on the determination of the extent of product innovation, the diffusion of such innovation, the impact of product innovation on firm performance, price measurement, and welfare, while the final chapter addresses policy issues.

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