A Numerical Study of Combined Forced Convection and Gas Radiation From a Circular Cylinder in Cross Flow

A numerical study of combined forced convection and gas radiation from a circular cylinder is carried out. The fluid is assumed to be radiatively participating. Simulations are carried out for both laminar and turbulent flows. The Reynolds numbers considered are 100 and 500 for laminar flow and 7190, 21,580, 35,950, and 50,350 for turbulent flow. To check the effect of three-dimensionality on heat transfer characteristics, numerical simulations are also carried out for three-dimensional geometry. All the thermophysical properties of the working fluid are taken as those of air and are assumed to be constant for the range of temperature considered in the present study. In order to understand the effects of absorption and scattering of thermal radiation, a detailed parametric study is carried out by varying the absorption and scattering coefficients from 0 to 60 (m^?1). It is observed that the contribution of radiative heat transfer on total heat transfer is significant when the flow is laminar. The radiative Nusselt number decreases with the increase of absorption coefficient.     

Effect of fatigue damage on the dynamic fracture toughness of En-8-grade steel

Machine components normally experience fatigue cycling during operation. Failure of these components is mostly due to fatigue. So, it is important to know the fatigue damage behavior and fatigue life of the material before selecting these steels for making different machine components. The En-8-grade (equivalent to SAE/AISI 1040) steel is generally used as a machine component in the annealed or hardened-and-tempered condition. The fatigue life (fatigue/endurance limit) is also dependent upon the tensile properties of any material. By suitable heat treatment, one can manipulate the tensile properties of any steel. The present work reports the effect of fatigue damage in En-8-grade heattreated steel (annealed and hardened and tempered), under different cyclic loading conditions at room temperature (25 °C), on the impact and dynamic fracture-toughness properties. The results indicate higher fracture toughness and impact toughness in hardened-and-tempered steel than in annealed steel. Cyclic hardening and softening occurs in both the hardened-and-tempered as well as the annealed steel. With the increase of peak stress and number of fatigue cycles, the K _ID and CVN values decrease in hardened-and-tempered steels. The results are discussed in terms of dislocations, slip bands, and their density, microstructure, and fracture morphology.     

EFFECTS OF HALL CURRENT AND CHEMICAL REACTION ON OSCILLATORY MIXED CONVECTION-RADIATION OF A MICROPOLAR FLUID IN A ROTATING SYSTEM

This article is concerned with the analysis of the effects of thermal radiation on oscillatory mixed convection flow of a micropolar fluid in a rotating frame of reference in the presence of transverse magnetic field and Hall current. The influence of a first-order homogeneous chemical reaction and heat source effects is also analyzed. The governing partial differential equations with the appropriate boundary conditions are reduced to a set of ordinary differential equations using similarity transformations. The dimensionless governing equations for this investigation are solved analytically after using small perturbation approximation. The effects of various parameters on the velocity, temperature, and concentration fields as well as on skin-friction coefficient, Nusselt number, and Sherwood number with their amplitude and phase are discussed in detail. Numerical results are discussed with the help of graphs and tables. Present results are also compared with previously published work.     

TRANSIENT CONDUCTION AND RADIATION HEAT TRANSFER WITH VARIABLE THERMAL CONDUCTIVITY

The effect of variable thermal conductivity on transient conduction and radiation heat transfer in a planar medium is investigated. Thermal conductivity of the medium is assumed to vary linearly with temperature, while the other thermophysical properties and the optical properties are assumed constant. The radiative transfer equation is solved using the discrete transfer method, (DTM) and the nonlinear energy equation is solved using an implicit scheme. Transient as well as steady state results are found for an absorbing, emitting, and anisotropically scattering gray medium. Thermal conductivity has been found to have significant effects on both transient as well as steady state temperature and heat flux distributions. Some steady state results are compared with the results reported in the literature.     

Non linear dynamics of memristor based 3rd order oscillatory system

In this paper, we report for the first time the nonlinear dynamics of three memristor based phase shift oscillators, and consider them as a plausible solution for the realization of parametric oscillation as an autonomous linear time variant system. Sustained oscillation is reported through oscillating resistance while time dependent poles are present. The memristor based phase shift oscillator is explored further by varying the parameters so as to present the resistance of the memristor as a time varying parameter, thus potentially eliminating the need of external periodic forces in order for it to oscillate. Multi memristors, used simultaneously with similar and different parameters, are investigated in this paper. Mathematical formulas for analyzing such oscillators are verified with simulation results and are found to be in good agreement.     

An ionic liquid as a potential multifunctional lubricating oil additive

Abstract

Homopolymer of decyl acrylate was synthesized and blended with phosphonium based ionic liquid and their characterisation was carried out by spectral method (NMR, IR), thermogravimetric analysis and gel permeation chromatography (GPC). Performance of these blends were evaluated by standard ASTM method in base oil which clearly indicates that the blend effectively act as anti-wear agent and also pour point depressants and viscosity modifiers. A comparison of their performances with homopolymer has also been evaluated and reported.     

Integrated services packet networks with mobile hosts: Architecture and performance

This paper considers the support of real-time services to mobile users in an Integrated Services Packet Network. In the currently existing architectures, the service guarantees provided to the mobile hosts are mobility dependent, i.e., mobile hosts experience wide variation in the quality of service and often service disruption when hosts move from one location to another. The network performance degrades significantly when mobile hosts are provided with mobility independent service guarantees. In this paper we have proposed a service model for mobile hosts that can support adaptive applications which can withstand service degradation and disruption, as well as applications which require mobility independent service guarantees. We describe an admission control scheme for implementing this service model and evaluate its performance by simulation experiments. Simulation results show that, if sufficient degree of multiplexing of the mobility dependent and independent services are allowed, the network does not suffer any significant performance degradation and in particular our admission control scheme achieves high utilization of network resources.     

Testing and modelling of a novel ceiling panel for maintaining space relative humidity by moisture transfer

Radiant ceiling panels are preferred over all-air systems because of their ability to lower energy consumption and maintain better comfort conditions. One disadvantage is their inability to moderate indoor humidity. To overcome this limitation, a new panel that can transfer heat and moisture is being developed. This research determines the performance of this panel under different temperature and humidity conditions. The effectiveness of the panel ranges from 15% to 28%, depending on the conditions. A computational fluid dynamics model of the panel has been developed using the commercial software, FLUENT. Good agreement is seen between experiments and the model for most cases. Comparing the change in humidity ratio of the air, the average difference is 5%.