Papers by Keyword: Two-Fluid Model

Abstract: Zero-point spin fluctuations are shown to strongly influence the ground state of ferromagnetic metals and to impose limitations for the fully spin polarized state assumed in half-metallic ferromagnets, which may influence their applications in spintronics. This phenomenon leads to the low-frequency Stoner excitations and cause strong damping and softening of magnons in magnetoresistive manganites observed experimentally.

Abstract: The Euler-Euler two-fluid model incorporating the kinetic theory of granular flow was applied to simulate the gas-solid flow in fluidized beds. The pressure drop, particle distribution and motion characteristics were studied in this paper. In order to investigate the effect of structure of the fluidized bed on flow characteristics, fluidized beds with different diameters and structures were applied. User defined functions (UDF) were applied to study the flow characteristics when the particle size and mass changed over time. The results showed that with the increase of particle size, higher minimum fluidization velocity was required, but lower pressure drop was obtained. For a certain fluidizing medium, the bed critical fluidization velocity depended only on the size and nature of the particles. The structure of a fluidized bed had an influence on the particle distribution and motion characteristics.

Abstract: The fuel flow characteristics in diesel nozzle orifice are key factors to the atomization of fuel near the nozzle orifice. In the paper, two-phase flow model is used to simulate the complex flow features in nozzle orifice, and to study the influences of the relative position of nozzles orifice axis and nozzle axis, and inclination angle of nozzle hole on the internal flow feature.

Abstract: A numerical simulation has been performed for subcooled boiling process of high pressure liquid. On the basis of two-fluid model, the RPI model is used to calculate the mass transfer on the heating wall between gas-liquid two phases. The results show there is an obvious turning point on wall temperature along with flow direction，which demonstrates the onset point of subcooled boiling according to the variation of wall temperature. The fluid velocity isn’t in linear increase, which increases gradually at first and then increases sharply, which is the similar with that of void fraction. The gas-phase velocity is higher than that of liquid-phase and the difference increases gradually along with flow direction. The variation of two-phase pressure difference is similar with that of single-phase flow, which is mainly the gravity pressure difference. The study results better meet with experimental data, which verifies the accuracy of computational model.

Abstract: Numerical simulation of dense-phase pneumatic conveying flow field was carried out by using k-ε-ks-εs two-fluid model in horizontal pipe on the basis of kinetic theory of granular flow. The coupling issue between gas phase and solid phase was taken into account in the process of simulation. Such characteristics of flow field along pipe as pressure distribution, concentration distribution, gas and particle velocity distribution were obtained. The results of numerical simulation showed the tends of pressure, gas velocity, particle concentration in pipeline. The results of numerical simulation were compared with experimental results, and it showed that the simulation results were validated by the experimental data, which indicate that the model and the corresponding algorithm have higher accuracy and better prediction. Thus the numerical simulation method can reveal the basic characteristics of dense phase pneumatic conveying in horizontal pipe.

Abstract: Generation of vapor and predication of its behavior is an important problem in many industries. In this study, the three dimensional governing equations for turbulence two-phase flow are derived using ensemble averaging two fluid model. The governing equations are simplified by a heuristic approach based on boiling data, and the equations are used to obtain the parameters for each phase along the channel. A computer program is written for the simplified one-dimensional equations, and the results are compared with experimental data.