Investigation of Material Deformation by the High-Speed Water Slugs

2002 ◽  
Author(s):  
O. Petrenko ◽  
E. S. Geskin ◽  
G. A. Atanov ◽  
B. Goldenberg ◽  
A. Semko
Keyword(s):  
Shock Waves ◽  
Nozzle Exit ◽  
High Speed ◽  
Numerical Models ◽  
Water Pressure ◽  
Experimental Studies ◽  
Surface Cleaning ◽  
Water Velocity ◽  
Material Deformation ◽  
The Impact

Water constitutes an attractive manufacturing tool It is readily available and clean. The waterjets are conventionally used for surface cleaning, material removal, and surface modification. The intrinsic shortcomings of such an application are the need in the use of expensive and heavy pumping facilities and, what are more important, peculiarities of the waterjet-substrate interaction which limit material deformation by the incoming jet. These shortcomings are eliminated if the workpiece is impacted by the array of the water slugs, generated by the direct injection of high-intensity energy pulses into the water vessel (barrel) and ejection the portion of the water via the nozzle attached into the barrel. Such a device (barrel-nozzle combination) will constitute an effective and versatile manufacturing tool. Understanding of the phenomena that occur in the course of the energy injection into the water is necessary for the design of the desired device. The phenomena in question are determined by the ratio between the speed of the water in the barrel in the course of the energy injection and the speed of the shock waves in the water. If this ratio is much less than unity, the exit velocity is determined by the ratio between the cross section areas of the nozzle exit and the barrel. If the ratio in question approaches the unity, the water velocity at the nozzle exit is determined by the impact pressure. The device utilizing this principle is termed the water extruder. If however, the ratio is much more than unity the exit water velocity is determined by the superposition of shock waves developed in the fluid. This device termed the water cannon is able to accelerate the water slug to the speed far exceeding 1,000 m/sec. The numerical and experimental studies of water extruder were carried out. The numerical models were constructed and the variation of the water velocity and the water pressure in the barrel were investigated. Experimental setup for the study of the water extruder was constructed by the modification of Remington power tool. The experiments involved the piercing of metal strips. The effect of operational conditions on the maximal depth of the piecing was determined. Another series of experiments involved the study of the slug impact on plastic (lead) and brittle (concrete) materials. The effect of the stand off distance on the removal of both kinds of material was investigated. As the result the suggestions about the way of construction of the water extruders and their practical applications were made.

scholarly journals Numerical and Experimental Study of Phase Transformations in Welding Processes / Badania Numeryczne I Doświadczalne Przemian Fazowych W Procesach Spawania

2015 ◽  
Vol 60 (4) ◽  
pp. 2559-2568 ◽  
Author(s):  
W. Piekarska
Keyword(s):  
Solid State ◽  
Heat Source ◽  
Phase Transformations ◽  
High Speed ◽  
Numerical Models ◽  
Experimental Studies ◽  
Butt Joint ◽  
Heat Of Fusion ◽  
Large Temperature ◽  
Welding Processes

The paper concerns the mathematical and numerical modeling of phase transformations in solid state occurring during welding. The analysis of the influence of heating rate, cooling rate and maximum temperatures of thermal cycles on the kinetics of phase transformations is presented. On the basis of literature data and experimental studies the evaluation of classic mathematical and numerical models of phase transformation is presented with respect to the advanced methods of welding by using a high speed and a high power heat source. The prediction of the structure composition in laser welded butt-joint made of S460 steel is performed, where phase transformations are calculated on the basis of modified numerical models. Temperature distributions are determined as well as the shape and size of fusion zone and heat affected zone (HAZ). Temperature field is obtained by the solution of transient heat transfer equation with convective term and external volumetric heat source taken into account. Latent heat of fusion, evaporation and heats generated during phase transformations in solid state are considered in the numerical algorithm due to the large temperature range present in analyzed process. Results of the numerical prediction of structure composition in HAZ are presented in this work. Obtained results of computer simulations are compared to experimental research performered on the laser welded joint.

Development of Two-Dimensional Bubble Movement and Development Benchmark Dataset for Numerical Validation

2012 ◽  
Author(s):  
Gholamreza Keshavarzi ◽  
Tracie J. Barber ◽  
Guan Yeoh
Keyword(s):  
High Speed ◽  
Numerical Models ◽  
Experimental Studies ◽  
Fluid Flows ◽  
Full Time ◽  
Two Phase ◽  
Point Of Interest ◽  
Time Shape ◽  
Computational Resources ◽  
Bubble Movement

The motion and transport of bubbles in fluid flows have many engineering applications. The rise of a bubble has been a point of interest for both numerical and experimental studies. Various tracking methodologies have been developed, including markers, level sets and volume tracking. In order to validate numerical models of bubble flow, detailed experimental data describing the transient bubble shape is needed. This is best found from a 2D comparison rather than 3D experiment because computational resources for determining an accurate shape can be maximized. No real full time shape and subsequent deformation of this 2D bubble has yet been demonstrated. In this paper 2D bubble experiments have been conducted, in which a single bubble has been injected inside a close-walled tank and the rising of the bubble has been captured through a high speed camera. This data is now being used as a benchmark for numerical interface capturing and two phase flow methodology validations.

scholarly journals Impact of a Single Spoiler on Scouring Depth Status Beneath a River Crossing Inclined Pipeline

2018 ◽  
Vol 8 (5) ◽  
pp. 3316-3320
Author(s):  
S. Abbasi ◽  
M. Masoomi ◽  
S. A. Arjmandi
Keyword(s):  
Numerical Models ◽  
Experimental Studies ◽  
Side Wall ◽  
Element Model ◽  
Scour Depth ◽  
Model Flow ◽  
Pipeline Management ◽  
Scouring Depth ◽  
The Impact ◽  
The Finite Element Model

Deep river crossing pipelines utilized to carry fluids are often placed upon the sand bed. Placement of pipe on the non-smooth bed would result in the production of some local gaps beneath the pipe. Asymmetric scouring is one of the main reasons for pipe underwater failures which are significant in pipeline management. So, in designing pipelines, knowing the interaction between pipelines and bed, and predicting the scour depth with respect to the pipe distance from the bed is significant to ensure that the pipe will finally deposit on the bed. Numerical models have been developed for predicting the balance depth of scouring beneath the pipelines. In this paper, the impact of pipe orientation on maximum scour depth beneath the pipelines is investigated. To do this, a pipe is modeled with various angles with the flow. To manage the local scouring, some spoilers are placed and modeled upon some pipes too. Also, in order to know the effects of placement of a pipe at various distances from the bed, the impact of placement of each pipe at a distance of 0.2D, 0.4D and 0.6D is investigated as well. To model the pipe with and without a spoiler, the finite element model Flow-3D is utilized and the results show good accordance with previous experimental studies and proof the current model’s precision in predicting the scour depth. Results show that in the placement of the pipe in angles not investigated before and also with the installing of a spoiler, the scour process has a reverse ratio with the distance which would result in full deposition of the pipe on the bed. The least scour depth belongs to the condition in which the pipe has a 130° angle with the side wall.

scholarly journals Electromagnetic reducers in electromechanical systems

2021 ◽  
pp. 42-46
Author(s):  
Igor Tkachuk ◽  
Mykhailo Kovalenko
Keyword(s):  
Wind Turbines ◽  
High Speed ◽  
Numerical Models ◽  
Mechanical Energy ◽  
Experimental Studies ◽  
Total Weight ◽  
Electromechanical Systems ◽  
Low Speed ◽  
Electric Generator ◽  
Additional Noise

      Currently, due to the rising cost of electricity, low-power wind turbines (1-5 kW) are often used to supply consumers with electricity. In this case, wind turbines are used with both horizontal and vertical axes of rotation, the speed of which at an average wind speed V = 5 ÷ 10 m / s and is quite low, and is approximately n = 100 - 300 rpm. A low-speed electric generator for a wind generator with such a speed of rotation with a direct connection of the wind rotor shaft and the electric generator has a large number of poles and reaches a fairly large size. Therefore, magnifying gears (multiplexers) are often used and can increase the speed of the electric generator several times and, thus, reduce the mass of its active part, because the electromagnetic moment is proportional to the volume of the electric machine. However, manual transmissions are a source of additional noise, require frequent maintenance and reduce the durability of the wind turbine. This article will use permanent magnet reducers for wind turbines, which, unlike mechanical reducers, do not create additional noise, do not require lubrication, their durability is higher, operating costs are also significantly reduced, while the magnetic reducer can be integrated with an electric generator. at a wind rotor power P = 4 kW and speed n = 100-300 rpm, high-speed electric generator and magnetic reducer have approximately 2 times less total weight of magnets and 1.7 times less total weight of active materials (magnetic reducer + electric generator) than a low-speed multipole external generator. The aim of the study is to develop and implement an electromagnetic reducer in electromechanical systems. The basis of such systems are high-coercive magnets. To achieve this goal, the following tasks are set: - literary-patent search on the research topic; - selection of a prototype of a magnetic reducer and calculation of its main parameters; - development of graphical and numerical models to evaluate the effectiveness of the developed prototype; - optimization of the design of the magnetic reducer; - development of a system for converting mechanical energy with low potential into electricity; - prototyping and experimental studies of the system of conversion of mechanical energy with low potential into electrical energy

Experimental Investigation of the Green Water Loads on a Wave-Piercing Tumblehome Ship

2017 ◽  
Author(s):  
Hui Li ◽  
Bao-Li Deng ◽  
Shu-Zheng Sun ◽  
Wen-Lei Du ◽  
Hao-Dong Zhao
Keyword(s):  
Experimental Investigation ◽  
High Speed ◽  
Water Pressure ◽  
Pressure Sensors ◽  
Green Water ◽  
Strong Nonlinearity ◽  
Water Tank ◽  
Water Tank Experiment ◽  
The Impact ◽  
Ship Speed

This paper presents the results of an experimental investigation of green water loads on a wave-piercing tumblehome ship. A water tank experiment was carried out in head regular waves by using a self-propelling segmented ship model. Wave probes and pressure sensors were arranged on the bow deck along the longitudinal and transverse directions. The height of water and the impact pressure on the deck were measured and their distributions in different wave conditions studied. The motion of the water flowing on the deck was recorded by a high-speed video system. Based on the experimental results, it was found that the green water is more serious with the increase of incident wave height and ship speed. The bow shape has little effects on the occurrence of green water, but it influences the green water loads to some extent. The distribution of green water pressure is different from that of green water height due to the strong nonlinearity of green water pressure.

The Oscillation Behaviour of Liquid Metal in Arc Welding

2007 ◽  
Vol 539-543 ◽  
pp. 3877-3882 ◽  
Author(s):  
M.J.M. Hermans ◽  
B.Y.B. Yudodibroto ◽  
Yoshinori Hirata ◽  
G. den Ouden ◽  
I.M. Richardson
Keyword(s):  
Liquid Metal ◽  
Weld Pool ◽  
Arc Welding ◽  
High Speed ◽  
Numerical Models ◽  
Experimental Studies ◽  
Intermediate Step ◽  
Filler Wire ◽  
Research Activities ◽  
Penetration Control

This paper gives an historic overview and new developments of research activities in the field of the oscillatory behaviour of liquid metal in arc welding. Early work focused on the oscillation behaviour of the weld pool in Gas Tungsten Arc Welding (GTAW). Agitated weld pools exhibit specific modes of oscillation, the frequency of which can be measured from the arc voltage data and is conditioned by the geometry of the weld pool and the properties of the liquid metal. Of technological interest is the alteration of the oscillation behaviour for partially and fully penetrated situations, which can be used for penetration control during welding. A logical extension of the research activities was related to the influence of filler wire addition on the oscillation behaviour. An intermediate step towards the description of Gas Metal Arc Welding (GMAW), is the situation of GTAW with cold filler wire supply. It was found that both the liquid weld pool and the pendant liquid droplet at the tip of the filler wire experience an oscillation, which obscures the influence of the individual contributions of both liquid masses on the voltage data. It was shown that online penetration control is still possible, provided that the metal is transferred in an uninterrupted way, i.e. the filler wire flows smoothly into the weld pool. For GMAW, in which detached droplets collide with the weld pool surface, the difficulties are even more prominent. Recent work is related to this issue. Monitoring of the phenomena occurring at the weld pool and the pendant droplet become problematic by means of the voltage data. Observations by means of high-speed video imaging will be discussed. Apart from the experimental studies, efforts are undertaken in numerical simulations of the processes. A good correlation is obtained between experimental data and the results of the numerical models.

scholarly journals Modeling of the interaction of the layered barrier with a high-speed fragment

2019 ◽  
Vol 221 ◽  
pp. 01042
Author(s):  
Alexandr Ishchenko ◽  
Nikolay Belov ◽  
Viktor Burkin ◽  
Anton Sammel ◽  
Nikolay Yugov ◽  
...  
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Software Systems ◽  
Fracture Mechanisms ◽  
Elasticity Limit ◽  
Transparent Armor ◽  
Initial Stage ◽  
Numerical Research ◽  
Shock Wave Pressure ◽  
The Impact

For the manufacture of transparent armor of high class protection, as a rule, reinforced silicate glasses, as well as transparent ceramics, are used. Since these materials are resiliently brittle, they can be used only in transparent multilayered barriers with protective back films for protection against high-speed fragmentation elements and bullets. Plexiglass or polycarbonate is most often used as the back layer. The barrier’s face layer must have a hardness substantially higher than the hardness of the drummer’s material, and the Hugonievskii elasticity limit must exceed the shock-wave pressure arising at the initial stage in the barrier. The purpose of this paper is to develop a mathematical model that allows, within the framework of a porous elastic-plastic medium with regard to various fracture mechanisms, to calculate the impact interaction of fragmentation elements with transparent armor. Numerical research was conducted with the help of copyright software systems. Experimental studies of the collision of transparent armor with a splinter simulator in the speed range of 1500 ... 2500 m / s were carried out with the use of throwing installations of the NRI AMM TSU.

scholarly journals Bubbles with shock waves and ultrasound: a review

2015 ◽  
Vol 5 (5) ◽  
pp. 20150019 ◽  
Author(s):  
Siew-Wan Ohl ◽  
Evert Klaseboer ◽  
Boo Cheong Khoo
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Biomedical Applications ◽  
High Speed ◽  
Experimental Studies ◽  
High Intensity Focused Ultrasound ◽  
High Speed Photography ◽  
Sound Waves ◽  
Bubble Cloud ◽  
Bubble Interaction

The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed ‘acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics–bubble interactions, with a focus on shock wave–bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the ‘resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave–bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead.

scholarly journals Particle–wall collisions in a viscous fluid

2001 ◽  
Vol 433 ◽  
pp. 329-346 ◽  
Author(s):  
G. G. JOSEPH ◽  
R. ZENIT ◽  
M. L. HUNT ◽  
A. M. ROSENWINKEL
Keyword(s):  
Reynolds Number ◽  
Viscous Fluid ◽  
High Speed ◽  
Particle Density ◽  
Particle Surface ◽  
Density Ratio ◽  
Experimental Studies ◽  
Stokes Number ◽  
Coefficient Of Restitution ◽  
The Impact

This paper presents experimental measurements of the approach and rebound of a particle colliding with a wall in a viscous fluid. The particle's trajectory was controlled by setting the initial inclination angle of a pendulum immersed in a fluid. The resulting collisions were monitored using a high-speed video camera. The diameters of the particles ranged from 3 to 12 mm, and the ratio of the particle density to fluid density varied from 1.2 to 7.8. The experiments were performed using a thick glass or Lucite wall with different mixtures of glycerol and water. With these parameters, the Reynolds number defined using the velocity just prior to impact ranged from 10 to approximately 3000. A coefficient of restitution was defined from the ratio of the velocity just prior to and after impact.The experiments clearly demonstrate that the rebound velocity depends on the impact Stokes number (defined from the Reynolds number and the density ratio) and weakly on the elastic properties of the material. Below a Stokes number of approximately 10, no rebound of the particle occurred. For impact Stokes number above 500 the coefficient of restitution appears to asymptote to the values for dry collisions. The coefficients of restitution were also compared with previous experimental studies. In addition, the approach of the particle to the wall indicated that the particle slowed prior to impacting the surface. The distance at which the particle's trajectory varied due to the presence of the wall was dependent on the impact Stokes number. The particle surface roughness was found to affect the repeatability of some measurements, especially for low impact velocities.

scholarly journals EXPERIMENTAL STUDIES OF WEARING AND TEARING OF ASPHALT CONCRETE SURFACING UNDER THE ACTION OF WATER PRESSURE IN MICROPORES

2021 ◽  
pp. 83-92
Author(s):  
V. V. Volkov ◽  
V. A. Kozlov ◽  
V. N. Melkumov
Keyword(s):  
Experimental Data ◽  
Asphalt Concrete ◽  
Water Pressure ◽  
Fluid Pressure ◽  
Experimental Studies ◽  
Hydrodynamic Effect ◽  
Depth Of Penetration ◽  
Wear And Tear ◽  
The Impact ◽  
Whole Life Cycle

Statement of the problem. The goal of this study is to identify the effect of wet surfacing on its wear and tear. The mechanism of influence of transport loading in the presence of moisture and experimental methods of measurement of its influence on wear and tear of the top layer of asphalt concrete are discussed. Results. The contribution of the presence of moisture in the upper layer of the pavement to its wear and tear in the form of track formation was identified, and the hydrodynamic effect of water in the micropores of the pavement was investigated. Experimental data on the values of water pressure in the pores of the asphalt-concrete pavement in the moistened state under the action of the wheels of the moving traffic flow were obtained. Therefore it became possible to identify the maximum values of the pressure effect, the depth of penetration of the fluid pressure front and its effect on the destruction of the surfacing.Conclusions. The analysis of the data showed not only the presence of brittle fracture, but also the impact of moisture moving in the pores of asphalt concrete, exceeding its structural strength. Using experimental data, regression dependences of the wear and tear value on the standard flow parameters were obtained. For the operated surfacings regression dependence enables one to predict the size of wear and tear for the whole life cycle of the road.

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