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In 1982, Smith and Hutton published comparative results of several different convection‐diffusion schemes applied to a specially devised test problem involving near‐discontinuities and strong streamline curvature. First‐order methods showed significant artificial diffusion, whereas higher‐order methods gave less smearing but had a tendency to overshoot and oscillate. Perhaps because unphysical oscillations are more obvious than unphysical smearing, the intervening period has seen a rise in popularity of low‐order artificially diffusive schemes, especially in the numerical heat‐transfer industry. This paper presents an alternative strategy of using non‐artificially diffusive higher‐order methods, while maintaining strictly monotonic transitions through the use of simple flux‐limiter constraints. Limited third‐order upwinding is usually found to be the most cost‐effective basic convection scheme. Tighter resolution of discontinuities can be obtained at little additional cost by using automatic adaptive stencil expansion to higher order in local regions, as needed.
Naturally buoyant flow and heat transfer in a cubic cavity with side opening is analyzed numerically. Vertical wall of the cavity is at a higher temperature than the…
Naturally buoyant flow and heat transfer in a cubic cavity with side opening is analyzed numerically. Vertical wall of the cavity is at a higher temperature than the ambient, while other walls are assumed to be adiabatic. Numerically accurate results are presented for Rayleigh numbers of 103 to 106 for a fluid having a Prandtl number of 0.71. Unstable flow is predicted for Ra = 1 × 107. The aim of the work is twofold; studying three‐ dimensional flow and heat transfer in a cavity and comparing three‐dimensional results with two‐dimensional approximation to verify the validity of the two‐dimensional model. Convection fluxes are calculated using QUICK scheme with ULTRA‐SHARP flux limiter for two and three‐dimensional simulation. The results indicate that as Rayleigh number increases the difference between two and three dimensional predictions increases. Also, it is found that this difference is greater for the flow field than for the rate of heat transfer.
An appreciation of the material from which modern printed circuit board drills are fabricated and an understanding of the salient geometric design features incorporated in such tooling will help those involved with the drilling process in determining optimum operating procedures and in identifying the underlying causes of hole deficiencies.
Reports numerical simulations of an unconfined methane‐air turbulent diffusion flame expanding from a porous burner. Turbulent combustion is simulated using the eddy…
Reports numerical simulations of an unconfined methane‐air turbulent diffusion flame expanding from a porous burner. Turbulent combustion is simulated using the eddy dissipation concept (EDC) which supposes that the reaction rate is controlled by the turbulent structures which enhance the mixing of fuel and oxidant. Two statistical k‐ε turbulence models have been tested: a standard high Reynolds number (HRN) and a more recent model based on the renormalization group theory (RNG). Radiation heat transfer and soot formation have been taken into account using P1‐approximation and transport submodels which reproduce the main phenomena encountered during soot production (nucleation, coagulation, surface growth). The set of coupled transport equations is solved numerically using a high order finite‐volume method, the velocity‐pressure coupling is treated by a projection technique. The numerical results confirm that 20‐25 percent of the combustion heat released is radiated away from the flame. Unsteady and unsymmetrical flame behaviour is observed for small Froude numbers which results from the development of Rayleigh‐Taylor like instabilities outside the flame surface. For higher Froude numbers the steady‐state and symmetrical nature of the solution is recovered.
A Selection of Equipment of Use in the Production and Maintenance of Aircraft, Missiles, Space Vehicles and Components. A new class R rotary stationary air compressor range has been introduced by the Consolidated Pneumatic Tool Co. Ltd., as a series of models with capacities of 70, 100, 160, 200, 300 and 500 cu. ft./min. at 100 lb./sq. in. Every size is available as an air or water cooled model and each of these variants can be supplied with a built‐in aftercooler. This extensive choice ensures that most operating conditions can be satisfied from the new range. The class R machines embody the well proven Power Vane principle of air compression in a new plant layout which now contains all the ancillary equipment for a stationary air compressor installation on one deck. This fully develops the inherent vibration free running and simple maintenance characteristics of the series to form a unique, continuous duty, packaged compressor. It is a feature of this new class R range that the need for supplying, mounting and connecting up any ancillary equipment such as an air receiver, after‐cooler or an electric starter is completely eliminated. Thus any model from the range can be supplied off the shelf and installed at its destination without special foundation preparation and with only simple connection to the electrical power supply and air mains.
This research aims to examine the casual relationship between normative belief (NB), subjective norms (SN), retailer’s behavioural belief (RBB), retailer’s attitude…
This research aims to examine the casual relationship between normative belief (NB), subjective norms (SN), retailer’s behavioural belief (RBB), retailer’s attitude (RATT), retailer’s behaviour intention (RBI), retailer’s actual behaviour (RAB) and retail performance (RetailP). Managing Halal meat becomes an issue for retailers due to consumers’ concerns for their religious belief.
A total of 230 questionnaires were distributed among Malaysian meat retailers of which 178 useful questionnaires were collected to empirically test the proposed seven critical points in Halal meat handling. Partial least squares, a structural equation modelling approach was used to examine simultaneously the structural components of both the measurement and causal model for reflective and formative constructs.
RBI and RAB are positively related to NB, SN, RBB and RATT in which motivate retailers for high RetailP and critical points in Halal meat handling. The empirical assessment supports the proposed hypotheses and supports RetailP as a formative construct measured by sales revenue, market share and customer satisfaction.
Empirically it was found that theory of reasoned actions (TRA) can be used to predict RetailP in addition to RAB. This study has significant policy implications alongside research implications despite some limitations.
The current literature and stated policies are focussing solely on consumers to understand the issues in Halal market which may not reach the strategic standpoint for firms and the state in general. The Malaysian Government should appreciate the importance of the Halal business markets in which NB, SN, RBB and RATT are influenced by certain elements discussed in this study.
This study is among the first few attempts towards “Islamic Retailing”. Prior literature applied TRA in a customer market verses this study examine the attitude and behaviour of businesses market (retailers) in Malaysia. This study explores retailers’ behaviour towards Halal value chain by integrating TRA and critical points in Halal meat handling.
In this paper new cubic v‐splines monotonic one‐dimensional profiles are presented, for the finite volume solution of convection‐diffusion problems. By studying the…
In this paper new cubic v‐splines monotonic one‐dimensional profiles are presented, for the finite volume solution of convection‐diffusion problems. By studying the profile in normalized variables, some weight functions have been determined for the profile. Being free of the requirement that the volumes be equal, the volume size can be reduced where needed. Numerical properties of the proposed method were formally analysed and are confirmed by numerical examples included here.
A new finite volume (FV) method is proposed for the solution ofconvection‐diffusion equations defined on 2D convex domains of general shape.The domain is approximated by a…
A new finite volume (FV) method is proposed for the solution of convection‐diffusion equations defined on 2D convex domains of general shape. The domain is approximated by a polygonal region; a structured non‐uniform mesh is defined; the domain is partitioned in control volumes. The conservative form of the problem is solved by imposing the law to be verified on each control volume. The dependent variable is approximated to the second order by means of a quadratic profile. When, for the hyperbolic equation, discontinuities are present, or when the gradient of the solution is very high, a cubic profile is defined in such a way that it enjoys unidirectional monotonicity. Numerical results are given.
This paper aims to present an evolutionary algorithm (EA) to accelerate the convergence for the radiative transfer equation (RTE) numerical solution using high-order and…
This paper aims to present an evolutionary algorithm (EA) to accelerate the convergence for the radiative transfer equation (RTE) numerical solution using high-order and high-resolution schemes by the relaxation coefficients optimization.
The objective function minimizes the residual value difference between iterations in each control volume until its difference is lower than the convergence criterion. The EA approach is evaluated in two configurations, a two-dimensional cavity with scattering media and absorbing media.
Experimental results show the capacity to obtain the numerical solution for both cases on all interpolation schemes tested by the EA approach. The EA approach reduces CPU time for the RTE numerical solution using SUPERBEE, SWEBY and MUSCL schemes until 97% and 135% in scattering and absorbing media cases, respectively. The relaxation coefficients optimized every two numerical solution iterations achieve a significant reduction of the CPU time compared to the deferred correction procedure with fixed relaxation coefficients.
The proposed EA approach for the RTE numerical solution effectively reduces the CPU time compared to the DC procedure with fixed relaxation coefficients.