Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 6 Articles
A parallel adaptive pseudo transient Newton-Krylov-Schwarz (a?NKS) method for the solution of compressible flows is presented.\r\nMultidimensional upwind residual distribution schemes are used for space discretisation, while an implicit time-marching scheme\r\nis employed for the discretisation of the (pseudo)time derivative. The linear system arising from the Newton method applied to the\r\nresulting nonlinear system is solved by the means of Krylov iterations with Schwarz-type preconditioners. A scalable and efficient\r\ndata structure for the (a?NKS procedure is presented.The main computational kernels are considered, and an extensive analysis is\r\nreported to compare the Krylov accelerators, the preconditioning techniques. Results, obtained on a distributed memory computer,\r\nare presented for 2D and 3D problems of aeronautical interest on unstructured grids....
Flickermeter is a common name for a system that measures the obnoxiousness of flicker caused by voltage fluctuations. The output\r\nof flickermeter is a value of short-term flicker severity indicator, Pst. This paper presents the results of the numerical simulations\r\nthat reconstruct the processing of flickermeter in frequency domain. With the use of standard test signals, the characteristics of\r\nflickermeter were determined for the case of amplitude modulation of input signal, frequency modulation of input signal, and for\r\ninput signal with interharmonic component. For the needs of simulative research, elements of standard IEC flickermeter signal\r\nchain as well as test signal source and tools for acquisition, archiving, and presentation of the obtained results were modeled. The\r\nresults were presented with a set of charts, and the specific fragments of the charts were pointed out and commented on. Some\r\nexamples of the influence of input signal�s bandwidth limitation on the flickermeter measurement result were presented for the\r\ncase ofAMand FM modulation. In addition, the diagrams that enable the evaluation of flickermeter�s linearity were also presented....
A detailed CFD modelling of an open refrigerated display cabinet has been formulated in a previous study. Some modifications\r\nare introduced in order to perform parametric studies dealing with low-cost geometrical and functional characteristics for\r\nimprovement of the global performance and energy efficiency. The parametric studies are devoted to the analysis of the thermal\r\nresponse and behaviour inside the food conservation space influenced by (1) air flow rate through the evaporator heat exchanger;\r\n(2) air curtain behaviour; (3) hole dimensions and distribution of the back panel; (4) discharge and return grilles angles; and\r\n(5) flow deflectors inside the internal duct. The analysis of the numerical predictions from the parametric studies allows the\r\ndevelopment of an optimized model for the conception of an open refrigerated display cabinet with a more adequate configuration.\r\nThe numerical predictions of the optimized model show lower product temperature and reduced electrical energy consumption,\r\nallowing the improvement of the food safety and the energy rationalization of the refrigeration equipment....
Liquid cooling electronics using microchannels integrated in the chips is an attractive alternative to bulky aluminum heat sinks.\r\nCooling can be further enhanced using nanofluids. The goals of this study are to evaluate heat transfer in a nanofluid heat sink\r\nwith developing laminar flow forced convection, taking into account the pumping power penalty. The proposed model uses semiempirical\r\ncorrelations to calculate effective nanofluid thermophysical properties, which are then incorporated into heat transfer\r\nand friction factor correlations in literature for single-phase flows. The model predicts the thermal resistance and pumping power\r\nas a function of four design variables that include the channel diameter, velocity, number of channels, and nanoparticle fraction.\r\nThe parameters are optimized with minimum thermal resistance as the objective function and fixed specified value of pumping\r\npower as the constraint. For a given value of pumping power, the benefit of nanoparticle addition is evaluated by independently\r\noptimizing the heat sink, first with nanofluid and then with water. Comparing the minimized thermal resistances revealed only\r\na small benefit since nanoparticle addition increases the pumping power that can alternately be diverted towards an increased\r\nvelocity in a pure water heat sink. The benefit further diminishes with increase in available pumping power....
In this paper simple model of improvement and deterioration rates of returns of a financial derivative is developed with time dependent power pattern optimal strategy. The improvement and deterioration are assumed to follow the three parameter Weibull distribution. A special attention is given to the use of three parameter Weibull scenarios analysis to perform stress testing of Weibull conditional tail expectations (WBCTE) based risk measurement systems....
Modeling the multiagents cooperative systems inspired from biological self-organized systems in the context of swarm model has\r\nbeen under great considerations especially in the field of the cooperation of multi robots. These models are trying to optimize\r\nthe behavior of artificial multiagent systems by introducing a consensus, which is a mathematical model between the agents as an\r\nintelligence property for each member of the swarm set. The application of this novel approach in the modeling of nonintelligent\r\nmulti agents systems in the field of cohesion and cluster formation of nanoparticles in nanofluids has been investigated in this study.\r\nThis goal can be obtained by applying the basic swarm model for agents that are more mechanistic by considering their physical\r\nproperties such as their mass, diameter, as well as the physical properties of the flow. Clustering in nanofluids is one of the major\r\nissues in the study of its effects on heat transfer. Study of the cluster formation dynamics in nanofluids using the swarm model\r\ncan be useful in controlling the size and formation time of the clusters as well as designing appropriate microchannels, which the\r\nnanoparticles are plunged into....
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