scholarly journals Self-thermophoresis of laser-heated spherical Janus particles

2021 ◽  
Vol 44 (11) ◽  
Author(s):  
E. J. Avital ◽  
T. Miloh
Keyword(s):  
Temperature Field ◽  
Continuous Light ◽  
The Self ◽  
Soret Coefficient ◽  
Physical Parameters ◽  
Two Phase ◽  
Rayleigh Approximation ◽  
Analytic Expressions ◽  
Induced Velocity ◽  
Laser Heated

Abstract An analytic framework is presented for calculating the self-induced thermophoretic velocity of a laser-heated Janus metamaterial micro-particle, consisting of two conducting hemispheres of different thermal and electric conductivities. The spherical Janus is embedded in a quiescent fluid of infinite expanse and is exposed to a continuous light irradiation by a defocused laser beam. The analysis is carried under the electrostatic (Rayleigh) approximation (radius small compared to wavelength). The linear scheme for evaluating the temperature field in the three phases is based on employing a Fourier–Legendre approach, which renders rather simple semi-analytic expressions in terms of the relevant physical parameters of the titled symmetry-breaking problem. In addition to an explicit solution for the self-thermophoretic mobility of the heated Janus, we also provide analytic expressions for the slip-induced Joule heating streamlines and vorticity field in the surrounding fluid, for a non-uniform (surface dependent) Soret coefficient. For a ‘symmetric’ (homogeneous) spherical particle, the surface temperature gradient vanishes and thus there is no self-induced thermophoretic velocity field. The ‘inner’ temperature field in this case reduces to the well-known solution for a laser-heated spherical conducting colloid. In the case of a constant Soret phoretic mobility, the analysis is compared against numerical simulations, based on a tailored collocation method for some selected values of the physical parameters. Also presented are some typical temperature field contours and heat flux vectors prevailing in the two-phase Janus as well as light-induced velocity and vorticity fields in the ambient solute and a new practical estimate for the self-propelling velocity. Graphic abstract

scholarly journals Investigation of Pressure Oscillation and Cavitation Characteristics for Submerged Self-Resonating Waterjet

2021 ◽  
Vol 11 (15) ◽  
pp. 6972
Author(s):  
Lihua Cui ◽  
Fei Ma ◽  
Tengfei Cai
Keyword(s):  
Sudden Change ◽  
Three Dimensional ◽  
Pressure Oscillation ◽  
Experimental Tests ◽  
Low Pressure ◽  
The Self ◽  
Two Phase ◽  
Cavitation Phenomenon ◽  
Pressure Zone ◽  
Unsteady Characteristics

The cavitation phenomenon of the self-resonating waterjet for the modulation of erosion characteristics is investigated in this paper. A three-dimensional computational fluid dynamics (CFD) model was developed to analyze the unsteady characteristics of the self-resonating jet. The numerical model employs the mixture two-phase model, coupling the realizable turbulence model and Schnerr–Sauer cavitation model. Collected data from experimental tests were used to validate the model. Results of numerical simulations and experimental data frequency bands obtained by the Fast Fourier transform (FFT) method were in very good agreement. For better understanding the physical phenomena, the velocity, the pressure distributions, and the cavitation characteristics were investigated. The obtained results show that the sudden change of the flow velocity at the outlet of the nozzle leads to the forms of the low-pressure zone. When the pressure at the low-pressure zone is lower than the vapor pressure, the cavitation occurs. The flow field structure of the waterjet can be directly perceived through simulation, which can provide theoretical support for realizing the modulation of the erosion characteristics, optimizing nozzle structure.

scholarly journals Modification of Mechanical Properties of High-Strength Titanium Alloys VT23 and VT23M Due to Impact-Oscillatory Loading

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 80 ◽  
Author(s):  
Mykola Chausov ◽  
Janette Brezinová ◽  
Andrii Pylypenko ◽  
Pavlo Maruschak ◽  
Liudmyla Titova ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloys ◽  
High Strength ◽  
The Self ◽  
Self Organization ◽  
Two Phase ◽  
Rolled Metal ◽  
Technological Method ◽  
Equilibrium Processes ◽  
Production Conditions

A simple technological method is proposed and tested experimentally, which allows for the improvement of mechanical properties in sheet two-phase high-strength titanium alloys VT23 and VT23M on the finished product (rolled metal), due to impact-oscillatory loading. Under impact-oscillatory loading and dynamic non-equilibrium processes (DNP) are realized in titanium alloys, leading to the self-organization of the structure. As a result, the mechanical properties of titanium alloys vary significantly with subsequent loading after the realization of DNP. In this study, the test modes are found, which can be used in the production conditions.

scholarly journals An Analytical Prediction Model of Balanced and Unbalanced Faults in Doubly-Fed Induction Machines

2021 ◽  
Author(s):  
Frederic Maurer ◽  
Trond Leiv Toftevaag ◽  
Jonas Kristiansen Nøland
Keyword(s):  
Large Scale ◽  
Induction Machine ◽  
Design Stage ◽  
Analytical Prediction ◽  
Two Phase ◽  
Mechanical Constraints ◽  
Analytic Expressions ◽  
Doubly Fed Induction Machine ◽  
Simulation And Experiment ◽  
Doubly Fed

This paper presents the exact transient solution to the unbalanced and balanced faults in the doubly-fed induction machine (DFIM). Stator currents, rotor currents, and stator fluxes have been validated using simulation and experiment. The work is meant to strengthen and fasten the predictability of large DFIMs in the design stage to comply with mechanical constraints or grid fault issues. Moreover, the analytical approach reduces the computational costs of large-scale stability studies and is especially suited to the initial phase where a plethora design computations must be carried out for the DFIM before it is checked for its transient interaction with the power system. The possibility to dynamically estimate DFIM performance is simplified by original equations derived from first principles. First, a case study of a large 265.50 MVA DFIM is used to verify the proposed "large machine approximation" using simulation, achieving an exact match. Then, laboratory measurements were conducted on a 10.96 kVA and a 1.94 kVA DFIM to validate the transient current peaks predicted in the proposed analytic expressions for two-phase and three-phase faults, respectively.

Influence of an inclined magnetic field on the Poiseuille flow of immiscible micropolar–Newtonian fluids in a porous medium

2018 ◽  
Vol 96 (9) ◽  
pp. 1016-1028 ◽  
Author(s):  
Pramod Kumar Yadav ◽  
Sneha Jaiswal
Keyword(s):  
Magnetic Field ◽  
Rotational Velocity ◽  
Immiscible Fluids ◽  
Newtonian Fluids ◽  
Porous Channel ◽  
Physical Parameters ◽  
Inclined Magnetic Field ◽  
Two Phase ◽  
Flow Through ◽  
Newtonian Viscous Fluid

The present problem is concerned with two-phase fluid flow through a horizontal porous channel in the presence of uniform inclined magnetic field. The micropolar fluid or Eringen fluid and Newtonian viscous fluid are flowing in the upper and lower regions of the horizontal porous channel, respectively. In this paper, the permeability of each region of the horizontal porous channel has been taken to be different. The effects of various physical parameters like angles of inclination of magnetic field, viscosity ratio, micropolarity parameter, etc., on the velocities, micro-rotational velocity of two immiscible fluids in horizontal porous channel, wall-shear stress, and flow rate have been discussed. The result obtained for immiscible micropolar–Newtonian fluids are compared with the results of two immiscible Newtonian fluids. The obtained result may be used in production of oil from oil reservoirs, purification of contaminated ground water, etc.

scholarly journals Numerical Study on the Gas-Water Two-Phase Flow in the Self-Priming Process of Self-Priming Centrifugal Pump

Processes ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 330 ◽  
Author(s):  
Chuan Wang ◽  
Bo Hu ◽  
Yong Zhu ◽  
Xiuli Wang ◽  
Can Luo ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Two Phase Flow ◽  
Numerical Study ◽  
The Self ◽  
Main Stage ◽  
Phase Flow ◽  
Urban Greening ◽  
Two Phase ◽  
Ansys Cfx ◽  
Priming Process

A self-priming centrifugal pump can be used in various areas such as agricultural irrigation, urban greening, and building water-supply. In order to simulate the gas-water two-phase flow in the self-priming process of a self-priming centrifugal pump, the unsteady numerical calculation of a typical self-priming centrifugal pump was performed using the ANSYS Computational Fluid X (ANSYS CFX) software. It was found that the whole self-priming process of a self-priming pump can be divided into three stages: the initial self-priming stage, the middle self-priming stage, and the final self-priming stage. Moreover, the self-priming time of the initial and final self-priming stages accounts for a small percentage of the whole self-priming process, while the middle self-priming stage is the main stage in the self-priming process and further determines the length of the self-priming time.

A New Kind of FDM/FEM Squeeze Casting Temperature Field Calculation Model

2013 ◽  
Vol 641-642 ◽  
pp. 303-308
Author(s):  
Yu Hong Zhao ◽  
Wei Ming Yang ◽  
Hua Hou
Keyword(s):  
Temperature Field ◽  
Melting Temperature ◽  
Squeeze Casting ◽  
Solidification Process ◽  
Pressure Change ◽  
Calculation Model ◽  
Physical Parameters ◽  
Field Calculation ◽  
Fem Model ◽  
Relationship Of

A new FDM/ FEM model is developed to simulate the temperature field during the solidification process of squeeze casting. So we can transform the FDM mesh into FEM mesh directly ,then established the relationship of pressure change and melting temperature change and correct the size of melting temperature value and other thermal physical parameters (such as the thermal conductivity)which is related to the temperature ,and establish the temperature and thermal physical parameter relationship to get a data base. The solidification process of AM50A magnesium alloy is simulated. Squeeze casting experiments are also incited for validating the new FDM/FEM model. It is shown that the results of numerical simulation are in agreement with the experimental results.

An Extra Mode of Enhanced Heat Transfer by Oscillating Bubbles in Minichannels and Microchannels

2003 ◽  
Author(s):  
J. J. Schro¨der ◽  
S. Alraun
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Bulk Water ◽  
Electrical Heating ◽  
Similar Process ◽  
Experimental Investigations ◽  
Physical Parameters ◽  
Two Phase ◽  
Model Calculations ◽  
Zero Crossing

Experimental investigations on heat transfer in tubular micro- or minichannel arrangements more often report on two-phase flow instabilities, pulsations or oscillations, which result in a remarkable influence on heat transfer efficiency. In order to explain the piston-like oscillations of the steam-plugs and water-slugs (-columns), the authors studied the somehow similar process which occurs in the worldwide known toy steam boat. Experiments have been performed which used a demonstration plant made of glass. By controlled electrical heating, high-speed video, pressure and local temperature measurements, the paths of energy have been disclosed. The results are as surprising as the effect of making gold from sand with respect to an equivalent axial heat-conductivity of the water-filled glass tube. Initiated by these results, an abstracting model is presented that analytically quantifies this new regenerating (oscillating and conducting) heat transfer mode e.g. concerning the combination of a heat recharging tube wall and an oscillating water column in a field of diminishing temperatures between the temperature of the boiler surface and the subcooled bulk water. By introducing these heat transfer details, the steam boat can give an answer, not only on frequency and amplitude of the oscillations, but on the steady state conditions for — or time-dependency of — the location of zero-crossing as well. Experimental results and model calculations are in good agreement and need no fitting factors. This is the base to discuss that process along with its physical parameters and compare it to the above mentioned observations in flow-boilers or pulsating heat pipes etc. which use microchannels or minichannels.

Thermal Image Analysis on the Axial Temperature Distribution of an AGHP (Axial Grooved Heat Pipe)

2009 ◽  
Author(s):  
Ling Cheng ◽  
Hanzhong Tao
Keyword(s):  
Temperature Field ◽  
Heat Pipe ◽  
Working Conditions ◽  
Wall Temperature ◽  
Flow Instability ◽  
Two Phase ◽  
Vacuum Degree ◽  
Single Temperature ◽  
Working Region ◽  
Vapor Liquid

The wall temperature field on the condenser section of an AGHP (Axial Grooved Heat Pipe) is measured by infrared thermal imaging technology, and the temperature field information on condenser wall is obtained in the horizontal and vertical working conditions and different temperature conditions. In accordance with the temperature field, Combination of the interaction characteristics between vapor-liquid two-phase annular flow, and by calculating, the accuracy to predict the outcome on non-condensable gas region is verified. Based on the distance to evaporator outlet, the condenser of the AGHP is divided into four regions for analysis. The zone I is closest to evaporator outlet and zone IV is located at the end of condenser. There are different characteristics in 4 zones for the AGHP with different vacuum degree and working conditions. On the conditions of horizontal working status, for the high vacuum AGHP, steadily working region, small fluctuations region, large fluctuations region and temperature recovery region will appear in turn. However for the low vacuum one, the single temperature fluctuation region and a linear decline region come forth followed by the abnormal increase region and steadily working region. Recurring to the analysis of wall temperature information, the characteristics of two-phase vapor-liquid phase change heat transfer and capillary driven flow inner the AGHPs can be discerned qualitatively or semi-quantitatively and some of the laws, Such as vacuum degree, two-phase flow instability are conjectured. The research content in this paper will redound to understanding inner working mechanism for an AGHP or a small heat pipe, and at the same time, provide theory evidences for heat pipe testing in the service of mass production.

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