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Article
Publication date: 1 March 1992

VIJAY K. GARG

A finite difference solution for steady natural convective flow within the human eye, modelled as a sphere with a specified temperature distribution over its surface, has…

Abstract

A finite difference solution for steady natural convective flow within the human eye, modelled as a sphere with a specified temperature distribution over its surface, has been obtained. The stream function—vorticity formulation of the equations of motion for the unsteady axisymmetric flow is used; interest lying in the final steady solution. Forward differences are used for the time derivatives and second‐order central differences for the space derivatives. The alternating direction implicit method is used for solution of the discretization equations. Local one‐dimensional grid adaptation is used to resolve the steep gradients in some regions of the flow at large Rayleigh numbers. The break‐up into multi‐cellular flow is found at high Rayleigh numbers. Results identify regions of stagnant fluid in locations similar to those of blind spots in the eye.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 2 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 July 2002

Abstract

Details

Library Hi Tech News, vol. 19 no. 7
Type: Research Article
ISSN: 0741-9058

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Article
Publication date: 4 March 2014

H.C. Garg and Vijay Kumar

The changing technological scenario necessitated hybrid journal bearings to operate under severe conditions of heavy load and high speed resulting into temperature rise of…

Abstract

Purpose

The changing technological scenario necessitated hybrid journal bearings to operate under severe conditions of heavy load and high speed resulting into temperature rise of the lubricant fluid-film and bearing surface. To predict the performance of a bearing realistically, theoretical model must consider the combined influence of the rise of temperature and non-Newtonian behavior of the lubricant. The aim of the present paper is to study the effect of viscosity variation due to temperature rise and non-Newtonian behavior of the lubricant on performance of constant flow valve compensated multiple hole-entry hybrid journal bearings.

Design/methodology/approach

Finite element method has been used to solve Reynolds equation along with restrictor flow equation, 3D energy equation and 3D conduction equation using suitable iterative technique. The non-Newtonian lubricant has been assumed to follow cubic shear stress law.

Findings

The thermohydrostatic rheological performances of symmetric and asymmetric hole-entry hybrid journal bearing configurations are studied. The computed results illustrate that variation of viscosity due to rise in temperature and non-Newtonian behavior of the lubricant affects the performance of hole-entry hybrid journal bearing system quite significantly.

Originality/value

In the present work, the influences of the viscosity variation due to temperature rise and non-Newtonian behavior of the lubricant on the performance characteristics of non-recessed hole-entry hybrid journal bearing with symmetric and asymmetric configurations compensated with constant flow valve restrictors have been investigated for generating the design data to be used by bearing designer. The design data computed in the present thesis are a contribution in field of knowledge of bearing design.

Details

Industrial Lubrication and Tribology, vol. 66 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 4 February 2014

Hem Chander Garg and Vijay Kumar

The slot-entry hybrid journal bearings have been successfully used in various engineering applications because of their good performance over wide range of speed and load…

Abstract

Purpose

The slot-entry hybrid journal bearings have been successfully used in various engineering applications because of their good performance over wide range of speed and load, besides their relative simplicity in manufacturing. Most of the research work pertaining to non-recessed journal bearing assumes standard symmetric and asymmetric configurations. However, many more configurations are possible by changing the position of slot which may improve the performance of the slot-entry journal bearing. In the present work study of static performance characteristics of slot-entry journal bearing of different configuration has been carried out. The paper aims to discuss these issues.

Design/methodology/approach

FEM has been used to solve the Reynolds equation governing the flow of lubricant in the bearing clearance space along with the restrictor flow equation. The non-Newtonian lubricant has been assumed to follow the cubic shear stress law. The performance characteristics of slot-entry hybrid journal bearings are computed by developing a computer program.

Findings

The simulated results of bearing characteristics parameters in terms of minimum fluid-film thickness and bearing flow have been presented for the wide range of various values of non-linearity factor and external load. It is found that there is an increase in the oil requirement for slot-entry hybrid journal bearing with the specified operating and geometric parameters, when the viscosity of the lubricant decreases due to the non-Newtonian behavior of the lubricant. The effect of the decrease in the viscosity of the lubricant due to non-Newtonian behavior of the lubricant diminishes the attitude angle. The computed performance characteristics are helpful for the bearing designer while choosing a particular configuration of bearing.

Research limitations/implications

The performance characteristics have been computed by considering the non-Newtonian lubricants. The thermal effects have been ignored in the analysis so as to obviate the mathematical complexity.

Originality/value

Get idea from already published manuscripts.

Details

Industrial Lubrication and Tribology, vol. 66 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 13 May 2021

Surya Prakash, Naga Vamsi Krishna Jasti, F.T.S. Chan, Nilaish, Vijay Prakash Sharma and Lalit Kumar Sharma

The objective of the present study is to identify and analyze a set of critical success factors (CSFs) for ice-cream industry [cold chain management (CCM)] that helps in…

Abstract

Purpose

The objective of the present study is to identify and analyze a set of critical success factors (CSFs) for ice-cream industry [cold chain management (CCM)] that helps in increasing the efficacy, quality, performance and growth of the supply chain organization.

Design/methodology/approach

A questionnaire survey with companies in ice-cream sector and a panel study with experts were conducted to identify and validate CSFs and their associated sub-factors. Eight CSFs identified from the cold chain domain vetted for the ice-cream industry and then prioritized by using one of the most well-known decision-making frameworks, Decision-Making Trial and Evaluation Laboratory. The general verdicts of the modelling and its application to the real-world case have been tested through an ice-cream company supply chain.

Findings

The result shows that the significant CSFs accountable for the growth of the ice-cream industry are the infrastructure and capacity building, consistent product improvement and operational efficiencies of the value chain. Subsequently, it was identified that the use of IT and related technologies and improved processes for operations also play a considerable role in the performance of ice-cream industry.

Practical implications

The study successfully outlines the effective CCM practices for critical issues. The proposed methodology and factor modelling case demonstration might be useful in analyzing the logistic chains of products such as fruits, drugs and meat.

Originality/value

The meritorious identification of critical areas and executing mitigation plans bring notable benefits to the firms such as improved operational efficiencies, improved time to market performance and product innovation, which bring additional benefits to the producers.

Details

Measuring Business Excellence, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1368-3047

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Article
Publication date: 16 September 2013

H.C. Garg and Vijay Kumar

The purpose of this paper is to describe the static performance characteristics of orifice compensated hole-entry hybrid journal bearing considering the combined influence…

Abstract

Purpose

The purpose of this paper is to describe the static performance characteristics of orifice compensated hole-entry hybrid journal bearing considering the combined influence of rise in temperature and non-Newtonian behavior of the lubricant. The required governing equations have been solved using the finite element method and a suitable iterative technique. The non-Newtonian lubricant has been assumed to follow the cubic shear stress law. The thermohydrostatic (THS) rheological performance of asymmetric hole-entry hybrid journal bearing configurations are studied. The computed results indicate that variation of viscosity due rise in temperature and non-Newtonian behavior of the lubricant affects the performance of asymmetric hole-entry hybrid journal bearing system quite significantly.

Design/methodology/approach

The THS rheological solution of a hole-entry hybrid journal bearing system requires the simultaneous solution of Reynolds equation, 3D energy equation and 3D conduction equation along with appropriate boundary conditions. In present study an iterative numerical solution scheme is used to establish pressure and temperature fields in the lubricant fluid-film.

Findings

The computed results indicate that variation of viscosity due rise in temperature and non-Newtonian behavior of the lubricant affects the performance of asymmetric hole-entry hybrid journal bearing system quite significantly.

Originality/value

The available literature concerning the orifice compensated asymmetric hole-entry hybrid journal bearings indicates that the thermal effects together with non-Newtonian behavior of lubricant due to additives mixed in the lubricants have been ignored in the analysis so as to obviate the mathematical complexity. The bearing performance characteristics have been presented considering the combined influence of rise in temperature and non-Newtonian behavior of the lubricant for asymmetric bearing configurations.

Details

Industrial Lubrication and Tribology, vol. 65 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 8 July 2019

Abdul Kareem Lado and V.V. Singh

The purpose of this paper is to covenant with the cost assessment of a complex repairable system, consisting of two subsystems (Subsystem 1 and Subsystem 2) connected in…

Abstract

Purpose

The purpose of this paper is to covenant with the cost assessment of a complex repairable system, consisting of two subsystems (Subsystem 1 and Subsystem 2) connected in series configuration and being operated by a human operator. Each subsystem has two identical units in parallel configuration and has different types of failure and two types of repairs (general repair and copula repair). Through the transition diagram, the system of first-order partial differential equations is derived and solved using a supplementary variable technique, Laplace transforms. All failures are assumed to follow exponential distribution, whereas repairs follow two types of distributions that are general and Gumbel–Hougaard family copula. In this paper, explicit expressions for reliability, availability, mean time to failure (MTTF) and cost analysis functions have been obtained. In this paper, two types of repairs (copula repair and general repair) have been studied, and it has been concluded that copula repair is more reliable as compared to general repair. Some computations are taken as particular case by evaluating: reliability, availability, MTTF and cost analysis, so as to capture the effect of both failure and repair rates to reliability measures. The results have been shown in tables and graphs. The convincing part has been discussed in last section of this study.

Design/methodology/approach

This paper is focused on the cost assessment of a system consisting two subsystem series configuration. Each subsystem has two identical units in parallel configuration. The performance of the system has been analyzed by supplementary variable techniques and Laplace transforms. Various measures of the reliability have been discussed by evaluations. Software called Maple 13 is used for computations.

Findings

In this research paper, the authors have evaluated the operational cost and incurred profit of the system together with other reliability measures for various situations and different types of failures and two types of repairs using Gumbel–Hougaard family copula distribution.

Research limitations/implications

The present research focuses on the series and parallel configured complex systems that is used everywhere in industry and other sectors. The authors main aim is to claim that repair through the joint probability distribution copula is far better than general repair. Copula repair for a completely failed system is more beneficial for industrial system operations that will increase profit to the industrial sector.

Practical implications

The authors have observed that when repair follows general distribution the values of reliability obtained of the system are less compared to the those obtained when the authors apply copula repair, a joint probability distribution. It is a clear implication for industrial sector and organization to use the policy for a better generate revenue.

Social implications

According to the best of authors’ knowledge, there is no social implication as this study is meant for reliability section. The study in management and case study matters is considered to have social implication.

Originality/value

This research is the original work of authors. Nothing has been copied from any paper or book. The references are cited according to the relevance of study.

Details

International Journal of Quality & Reliability Management, vol. 36 no. 10
Type: Research Article
ISSN: 0265-671X

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Article
Publication date: 6 February 2009

H.C. Garg, Vijay Kumar and H.B. Sharda

Every high speed machine, demanding high level of perfection, can operate successfully through a precise design of bearings. Such a design can be formulated after…

Abstract

Purpose

Every high speed machine, demanding high level of perfection, can operate successfully through a precise design of bearings. Such a design can be formulated after carefully studying both static and dynamic characteristics of the journal bearing. The present paper aims to describe the study of static and dynamic performance of a hole‐entry hybrid journal bearing system compensated with capillary restrictor by considering the combined influence of thermal effects and non‐Newtonian behavior of the lubricant.

Design/methodology/approach

The variation of the viscosity due to the non‐Newtonian behavior of the lubricant and temperature rise is considered in the study. The numerical solution of the generalized Reynold's, equation governing the flow of the lubricant having variable viscosity along with the energy and heat conduction equations is obtained using finite element method. The non‐Newtonian lubricant has been assumed to follow the cubic shear stress law. The study includes performance of a double row symmetric hole entry hybrid journal bearing configuration containing 12 holes per row.

Findings

The results indicate that change in viscosity of lubricant affects the bearing design parameters.

Originality/value

The paper shows that accurate theoretical modeling of the bearing is an effective tool for the selection of design parameter such as bearing land width ratio (ab), restrictor design parameter (Cs2), and non‐linearity factor (K).

Details

Industrial Lubrication and Tribology, vol. 61 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 9 August 2013

H.C. Garg and Vijay Kumar

This paper aims to investigate the effect of plugging of holes on the static performance characteristics of a constant flow valve compensated hole‐entry hybrid journal…

Abstract

Purpose

This paper aims to investigate the effect of plugging of holes on the static performance characteristics of a constant flow valve compensated hole‐entry hybrid journal bearing system operating with Newtonian and non‐Newtonian lubricants. The analysis considers the generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor. The non‐Newtonian lubricant is assumed to follow the power law. The performance characteristics are computed for the two values of power law index (n=1.0 and 0.566). The computed results indicate that the blockage of holes during operation will not be the likely causes for the imminent failure of a well‐designed non‐recessed hole‐entry hybrid journal bearing.

Design/methodology/approach

Finite element method has been used to solve generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor.

Findings

The computed results indicate that the blockage of holes during operation will not be the likely causes for the imminent failure of a well‐designed non‐recessed hole‐entry hybrid journal bearing. The bearing configuration with plugged holes provides sufficient fluid film thickness and low power requirement as less lubricant is required to be pumped in the bearing.

Originality/value

To the best of the author's knowledge, no study which considers the influence of plugging of holes on the static performance characteristics of a constant flow valve compensated hole‐entry hybrid journal bearing system operating with Newtonian and non‐Newtonian lubricant is yet available in the literature.

Details

Industrial Lubrication and Tribology, vol. 65 no. 5
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 5 October 2012

H.C. Garg

The purpose of this paper is to present theoretical investigations of the static performance characteristics of orifice compensated symmetric hole‐entry hybrid journal…

Abstract

Purpose

The purpose of this paper is to present theoretical investigations of the static performance characteristics of orifice compensated symmetric hole‐entry hybrid journal bearing considering the combined influence of rise in temperature and non‐Newtonian behavior of the lubricant.

Design/methodology/approach

The thermohydrostatic (THS) rheological solution of a hole‐entry hybrid journal bearing system requires the simultaneous solution of Reynolds equation, energy equation and conduction equation along with appropriate boundary conditions. In the present study an iterative numerical solution scheme is used to establish pressure and temperature fields in the lubricant fluid‐film.

Findings

It is found that there is an increase in the oil requirement for a hybrid journal bearing with the specified operating and geometric parameters, when the viscosity of the lubricant decreases due to the rise in temperature and non‐Newtonian behavior of the lubricant.

Originality/value

The available literature concerning the orifice compensated symmetric hybrid/hydrodynamic journal bearings indicates that the thermal effects together with non‐Newtonian behavior of lubricant due to additives mixed in the lubricants have been ignored in the analysis so as to obviate the mathematical complexity.

Details

Journal of Engineering, Design and Technology, vol. 10 no. 3
Type: Research Article
ISSN: 1726-0531

Keywords

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