STUDY OF FREE BURNING ARC CHARACTERISTICS BY DIMENSIONAL ANALYSIS AND COMPUTER SIMULATION

2012 ◽  
Vol 03 (02) ◽  
pp. 1250001
Author(s):  
GRÉGOIRE DE IZARRA
Keyword(s):  
Dimensional Analysis ◽  
Thermal Conduction ◽  
Current Intensity ◽  
Large Set ◽  
Physical Processes ◽  
Arc Voltage ◽  
Radiation Losses ◽  
Arc Characteristics ◽  
Pi Theorem ◽  
1D Numerical Simulation

This paper deals with the study of experimental current intensity/voltage characteristics of a free burning arc that appears to be singular: At low intensity current, the arc voltage decreases until a minimum value, corresponding to a critical current intensity Ic. For current intensities higher than Ic, there is an increase of the arc voltage with the current intensity. Dimensional analysis and Pi theorem coupled with a large set of experimental data allow us to evaluate the main physical processes responsible for the characteristics shape. At low current intensity, the plasma is mostly driven by thermal conduction effects while at high current intensity, it is principally governed by radiation losses. Finally, the results obtained from dimensional analysis allow to propose a 1D numerical simulation of the plasma column that gives rather good qualitative results.

scholarly journals Characterization of venturi injector using dimensional analysis

2019 ◽  
Vol 23 (7) ◽  
pp. 484-491 ◽  
Author(s):  
Luiz R. Sobenko ◽  
José A. Frizzone ◽  
Antonio P. de Camargo ◽  
Ezequiel Saretta ◽  
Hermes S. da Rocha
Keyword(s):  
Dimensional Analysis ◽  
Flow Rate ◽  
Injection Rate ◽  
Operating Conditions ◽  
Functional Tests ◽  
Injection Flow Rate ◽  
Injection Flow ◽  
Hydraulic Conditions ◽  
Fluid Properties ◽  
Pi Theorem

ABSTRACT Venturi injectors are commonly employed for fertigation purposes in agriculture, in which they draw fertilizer from a tank into the irrigation pipeline. The knowledge of the amount of liquid injected by this device is used to ensure an adequate fertigation operation and management. The objectives of this research were (1) to carry out functional tests of Venturi injectors following requirements stated by ISO 15873; and (2) to model the injection rate using dimensional analysis by the Buckingham Pi theorem. Four models of Venturi injectors were submitted to functional tests using clean water as motive and injected fluid. A general model for predicting injection flow rate was proposed and validated. In this model, the injection flow rate depends on the fluid properties, operating hydraulic conditions and geometrical characteristics of the Venturi injector. Another model for estimating motive flow rate as a function of inlet pressure and differential pressure was adjusted and validated for each size of Venturi injector. Finally, an example of an application was presented. The Venturi injector size was selected to fulfill the requirements of the application and the operating conditions were estimated using the proposed models.

scholarly journals The Classical Nature of Thermal Conduction in Nanofluids

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Jacob Eapen ◽  
Roberto Rusconi ◽  
Roberto Piazza ◽  
Sidney Yip
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Strong Evidence ◽  
Thermal Conduction ◽  
Base Fluid ◽  
Liquid Mixtures ◽  
Large Set ◽  
Conductivity Data ◽  
Homogeneous Systems ◽  
Thermal Conductivity Data

We show that a large set of nanofluid thermal conductivity data falls within the upper and lower Maxwell bounds for homogeneous systems. This indicates that the thermal conductivity of nanofluids is largely dependent on whether the nanoparticles stay dispersed in the base fluid, form large aggregates, or assume a percolating fractal configuration. The experimental data, which are strikingly analogous to those in most solid composites and liquid mixtures, provide strong evidence for the classical nature of thermal conduction in nanofluids.

Thermal Effects in the Free Oscillation of Gas Bubbles

1971 ◽  
Vol 93 (3) ◽  
pp. 373-376 ◽  
Author(s):  
R. B. Chapman ◽  
M. S. Plesset
Keyword(s):  
First Principles ◽  
Thermal Effects ◽  
Thermal Conduction ◽  
Free Oscillation ◽  
Acoustic Radiation ◽  
Numerical Results ◽  
Air Bubbles ◽  
Gas Bubble ◽  
Physical Processes ◽  
Polytropic Exponent

A theory is developed from first principles which includes all the important physical processes which affect the frequency of the free oscillations of a gas bubble. The components of the damping: viscosity, thermal conduction in the gas, and acoustic radiation are all determined. Numerical results for the damping are given for air bubbles in water. Since there is physical interest in the polytropic exponent, κ, (in pVκ = const.), the value of κ which gives the correct natural frequency is also determined. Numerical results for this κ for air bubbles in water are presented.

A Numerical Model for the Identification of the Structural Damages in Rolling Contact Bearings Using Matrix Method of Dimensional Analysis

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
I. M. Jamadar ◽  
D. P. Vakharia
Keyword(s):  
Dimensional Analysis ◽  
Matrix Method ◽  
Energy Levels ◽  
Rolling Contact ◽  
Outer Race ◽  
Operating Load ◽  
Combined Use ◽  
Dependent Parameter ◽  
Multiple Variables ◽  
Pi Theorem

The damages to the structural elements, viz., inner race, outer race, rollers, cage, etc., of rolling contact bearings if not detected in time can cause tragic failures of the machineries supported by these bearings. The operating parameters like variations in the machinery speed, unbalance, operating load, etc., can cause a bearing to vibrate at higher energy levels and consequently will accelerate its wear. An attempt is made in this study, and a generalized model is developed using matrix method of dimensional analysis (MMDA) that predicted the response and correlated the dependent parameter, i.e., response with the significant independent parameters. Combined use of response surface methodology (RSM) is made to explore the dependence of various factors such as size of the defect, unbalance, speed, and their interactions on the vibration characteristics of the bearings. It is observed from the study that the model developed based on the MMDA has provided an efficient approach in recognizing the damaged bearing state, which can be easily implemented in the condition-based preventive maintenance strategies. Also, the effectiveness of MMDA as compared to the conventional Buckingham's pi theorem in the dimensional analysis (DA) practice, especially in the problems involving multiple variables, is shown in this study.

Dimensional Analysis and the Buckingham Pi Theorem

1972 ◽  
Vol 40 (12) ◽  
pp. 1815-1822 ◽  
Author(s):  
John H. Evans
Keyword(s):  
Dimensional Analysis ◽  
Pi Theorem
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