Papers by Keyword: Finite Volume Method (FVM)

Abstract: The ocean wave energy conversion into electricity has been increasingly researched in the last years. There are several proposed converters, among them the Oscillating Water Column (OWC) device has been widely studied. The present paper presents a two-dimensional numerical investigation about the fluid dynamics behavior of an OWC Wave Energy Converter (WEC) into electrical energy. The main goal of this work was to numerically analyze the optimized geometric shape obtained in previous work under incident waves with different heights. To do so, the OWC geometric shape was kept constant while the incident wave height was varied. For the numerical solution it was used the Computational Fluid Dynamic (CFD) commercial code FLUENT^®, based on the Finite Volume Method (FVM). The multiphasic Volume of Fluid (VOF) model was applied to tackle with the water-air interaction. The computational domain is represented by the OWC device coupled with the wave tank. This work allowed to check the influence of the incident wave height on the hydropneumatic power and the amplification factor of the OWC converter. It was possible to identify that the amplification factor increases as the wave period increases, thereby improving the OWC performance. It is worth to highlight that in the real phenomenon the incident waves on the OWC device have periods, lengths and height variables.

Abstract: This paper presents the parameters and assumptions of the hydrostatic guide rail in both ideal and actual working conditions, the simulate calculation of fluid-solid heat coupling field between gas film and the bearing surface is finished by Fluent based on finite volume method. By analyze and compare the results after post-treatment, we gain the effects caused by guide way’s structure and deformation on the formation of film pressure field, temperature field inside gas film, besides this paper also provides relate conclusions.

Abstract: We extend the application of numerical entropy production, as a smoothness indicator, from conservation laws to balance laws. We aim to indicate the smoothness of solutions to the shallow water equations involving varying width, which are a system of balance laws. The numerical entropy production appears to be accurate to detect discontinuities. As a numerical test, a radial dam break is considered. We assume that there is a higher level of water inside a radial dam than water outside the dam wall. If the radial dam is totally broken, then water flows from inside to outside. The flow results in a solution having shock discontinuities. Finding the positions of the discontinuities is our interest. They are the positions where numerical solutions, such as those generated by a finite volume method, decrease their accuracy. Detecting the position of the discontinuity can help in the improvement of the numerical solution in terms of its accuracy. We obtain that the numerical entropy production is simple to implement but give an accurate detection. The discontinuity of the stage (free water surface) is clearly detected by large values of the numerical entropy production as the smoothness indicator.

Abstract: In this work it is numerically studied the wave flow inside a tank and the main operational physical principle of three different wave energy converters (WEC): oscillating water column (OWC), overtopping and submerged plate. The wave energy converters are evaluated in laboratory and real scales. For all studied cases the conservation equations of mass, momentum and one equation for the transport of volumetric fraction are solved with the finite volume method (FVM). To tackle with water-air mixture, the multiphase model Volume of Fluid (VOF) is used. Several results showed the accuracy of the numerical approach for estimation of the physical phenomenon of wave flow inside tanks, as well as, its interaction with the studied devices. For the cases with geometrical optimization, Constructal Design is employed for geometrical evaluation of the devices. Results presented several theoretical recommendations about the influence of geometrical parameters (such as ratios between heights and lengths of OWC chamber and ramp of overtopping device and the distance from the plate to the seabed of wave tank) over the available power take off (PTO) in the OWC and submerged plate devices and over the amount of water stored in the reservoir of the overtopping device. Results showed the importance of geometric shapes over the devices performance. Moreover, it is evaluated the influence of several wave parameters (such as wave period and relative depths) over the fluid dynamic performance of the devices and geometrical parameters of the devices. It is noticed the non-occurrence of universal optimal shapes.

Abstract: Oil immersed transformer is an important equipment ofpower system, whose fault is often caused by the aging of insulation. In actualoperation, accurate calculation of the temperature field, especially hot spottemperature of transformer winding, is very important for stabilizing the powergrid operation and extending the transformer life. In order to calculate thetransformer's hot spot temperature accurately, a new method which is based oncomparison of respective advantages of the FEM and FVM is used; we take a31.5MVA transformer as exemple, using the hybrid method of the FEM and the FVM,the three-dimensional temperature field of transformer is calculated. Bycomparing the figures of top oil temperature of transformer monitored by theoperating transformer and the figures calculated by mixed method, the marginerror of the hot spot temperature is only 1.9°C. While the IEEE guidelines formodel calculation results, the calculated results of FEM algorithm and FVMalgorithm results with the monitoring data of standard deviation were as highas 4.6 °C, 3.8 °C and 3.1 °C. The Calculation accuracy is much higher than theaccuracy of the result using IEEE regulatory model, FEM and FVM, proved thatthis mixed method can calculate the internal temperature field of oil immersedtransformer accurately.

Abstract: Flow around a circular cylinder is a classical problem in fluid mechanics. The flowing problem about three tandem cylinders with different diameter is numerical simulated by a finite volume method. Through the simulation, the variations of flow field with different distance between the adjacent cylinder and different Reynolds number are investigated. The simulation result shows that three tandem cylinders with different diameter can evidently small columns minish width and aggrandize length of cylinder wakes compared with single cylinder.

Abstract: This study aimed to model numerically the thermal cycling resulting from the steel ASTM A743-CA6NM remelting process. The problem was solved with the support of the commercial software ANSYS / FLUENT ® 14.5 for the three-dimensional case using the finite volume method. The following simplifying assumptions were adopted: heat loss by natural convection, absence of radiation, no phase change, concentrated heat source, and thermophysical properties independent of temperature. The results were analyzed for two different current intensities: 90A and 130A, and compared with experimental measurements. The peak temperatures of the thermocouples near the fusion line for the current of 130A were well represented by the numerical model, with a maximum deviation of 9.62%. In the case of the more remote thermocouples from the fusion line, the best results were obtained for the current of 90A, not exceeding 5% of deviation. In general, it was found that the tested body is heated faster than in simulations. This can be considered as a consequence of the simplification in material properties, which were assumed constants with temperature. The results of this study demonstrate that, given the adopted simplifications, the numerical model was able to satisfactorily reproduce the experimentally measured thermal cycles.

Abstract: An increase of a combustion chamber volume of internal combustion engines (ICE) is connected with the solution of a problem of burning in cylinders of bigger amount of fuel. Thus, providing the complete burning, a full scavenging of cylinders and maintenance in permissible limits of temperature of exhaust gases requires increasing air supply. The most effective method of increase in amount of air is an increase of its density by means of preliminary compression in the compressor with the subsequent cooling. It should be noted that high complexity and a large labor content of the natural experiments do not allow receiving the reliable values of gas-dynamic characteristics of air flow in a compressor of a turbocharger. Therefore, by means of a computer code of computational fluid dynamics ANSYS-CFX, numerical studies of a flow in gas channel of a compressor of the KAMAZ engine are carried out. The integrated values of pressure, temperature in inlet and outlet of a compressor, received during numerical simulations, allow defining the air compression ratio, and also calculating compressor efficiency. Verification of the results of the numerical studies and of the natural experiment gives an agreement of the values with accuracy 1-5%. Hereafter, analysis of the calculation results, and optimization of the gas channel geometry of the compressor can allow improving gas-dynamic parameters of the compressor. This can lead to raise in techno-economic characteristics of the ICE.

Abstract: This study aims to numerically analyze the refractory wear of the blast furnace main trough. The three dimensional transient Navier-Stocks equation associated with the volume of fluid (VOF) was developed to describe the flow fields of air, molten iron and slag in the main trough of the blast furnace during tapping process; and then solved by the finite volume method (FVM) subject to the pressure implicit with split operator (PSIO). Based on the Newton’s law of viscosity, the computed shear stress profile in the impingement region consists with the erosion rate of main trough from the no. 4 blast furnace at China Steel Corporation (CSC BF4). The influence of the tapping angle and the ratio of iron to slag in tapping stream on the wall shear stress of main trough was also examined for the suggestion to minimize the refractory wear of blast furnace main trough in this work.

Abstract: The uniform temperature flied of substrates is a key factor to deposit high-quality diamond films on milling tools by the hot filament chemical vapor deposition (HFCVD). In this study, a 3-D computational model is established to simulate the temperature distribution on the substrates. Thereafter, the influence of the rotational speed of worktable n and the water flux of water-cooled worktable Q are investigated. The simulation results show that the increasing of the rotational speed of worktable is suitable to grow homogeneous diamond films and gently decrease the even temperature of seals. What’s more, the deceasing of the water flux will significantly increase the overall temperature of seals.