• Nuclear Engineering and Technology
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• v.38 no.1
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• pp.69-80
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• 2006

Fluid-elastic instability in an air-water two-phase cross-flow has been experimentally investigated using two different arrays of straight tube bundles: normal square (NS) array and rotated square (RS) array tube bundles with the same pitch-to-diameter ratio of 1.633. Experiments have been performed over wide ranges of mass flux and void fraction. The quantitative tube vibration displacement was measured using a pair of strain gages and the detailed orbit of the tube motion was analyzed from high-speed video recordings. The present study provides the flow pattern, detailed tube vibration response, damping ratio, hydrodynamic mass, and the fluid-elastic instability for each tube bundle. Tube vibration characteristics of the RS array tube bundle in the two-phase flow condition were quite different from those of the NS array tube bundle with respect to the vortex shedding induced vibration and the shape of the oval orbit of the tube motion at the fluid-elastic instability as well as the fluid-elastic instability constant.

• Advances in concrete construction
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• v.13 no.5
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• pp.361-365
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• 2022

The objective of this study is to simulate the two-phase flow in pipes with various two-fluid models and determinate the shear stress. A hyperbolic shear deformation theory is used for modelling of the pipe. Two-fluid models are solved by using the conservative shock capturing method. Energy relations are used for deriving the motion equations. When the initial conditions of problem satisfied the Kelvin Helmholtz instability conditions, the free-pressure two-fluid model could accurately predict discontinuities in the solution field. A numerical solution is applied for computing the shear stress. The two-pressure two-fluid model produces more numerical diffusion compared to the free-pressure two-fluid and single-pressure two-fluid models. Results show that with increasing the two-phase percent, the shear stress is reduced.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.471-474
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• 2006

The Mixer is apparatus that help precipitation or an inhomogeneous distribution of various phases to be mixed and that user makes necessary material mixing one or the other. Mainly the mixer which is used from chemical and food industry is very important system in engineering that mixes the material. The inside flow of the mixer under the actual states which put a basis in flow of the fluid is formed rotation of the impeller. The inside flow of impeller will be caused by various reasons change with shape of impeller, number of rotation, mixing material and flow pattern of free surface etc. Also mixer study depended in single-phase flow and experimental research. So the numerical analysis of flow mixing solid-fluid particle is simulated. It is become known, that the case where agitator inside working fluid includes the solid particle the sinkage reverse which the solid particle has decreases an agitation efficiency. From the research which it sees the hazard solid which examines the effect where the change of the sinkage territory which it follows agitation number of revolution and diameter of the particle goes mad to an agitator inside flow distribution - numerical analysis the inside flow distribution of liquid state with Eulerian Two-Phase Method.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.17 no.3
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• pp.209-219
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• 2013

The present paper deals with the extension of AUSMPW+ scheme into two-fluid model for multiphase flow. AUSMPW+ scheme is the improvement of a single-phase AUSM+ scheme by designing pressure-based weighting functions to prevent oscillations near a wall and shock instability after a strong shock. Recently, Kitamura and Liou assessed a family of AUSM-type schemes with two-fluid model governing equations [K. Kitamura and M.-S. Liou, Comparative study of AUSM-Family schemes in compressible multi-phase flow simulations, ICCFD7-3702 (2012)]. It was observed that the direct application of the single-phase AUSMPW+ did not provide satisfactory results for most of numerical test cases, which motivates the current study. It turns out that, by designing pressure-based weighting functions, which play a key role in controlling numerical diffusion for two-fluid model, problems reported in can be overcome. Various numerical experiments validate the proposed modification of AUSMPW+ scheme is accurate and robust to solve multiphase flow within the framework of two-fluid model.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2273-2278
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• 2007

Brazed Plate Heat Exchanger (BPHE) is a type of compact plate heat exchanger with parallel corrugated plates which are brazed together in series. Each plate hascorrugation called herringbone pattern. Inside a BPHE, hot fluid and cold fluid alternate its flow direction to establish counter current flow configuration. Two-phase flow heat transfer and pressure drop of R-22 in BPHE were experimentally measured in this study. In the present experiments, single-phase region and two-phase region coexist in a BPHE. Therefore, the inside of a BPHE have to be divided into single phase region and two phase region and analyzed accordingly. The results from the single phase flow analysis are then extended to the two phase flow analysis to correlate the condensation and evaporation heat transfer and pressure drop for the refrigerant R-22 in the BPHEs. Previous models for two- phase friction factor have been compared with the present experimental results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.2
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• pp.124-132
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• 2009

Experiments have been performed to investigate fluid-elastic instability of tube bundles, subjected to twophase cross flow. Fluid-elastic is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to the cross flow. The test section consists of cantilevered flexible cylinder(s) and rigid cylinders of normal square array. From a practical design point of view, fluid-elastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping parameter. For dynamic instability of cylinder rows, added mass, damping and the threshold flow velocity are evaluated. The Fluid-elastic instability coefficient is calculated and then compared to existing results given for tube bundles in normal square array.

• 한국전산유체공학회:학술대회논문집
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• 2002.10a
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• pp.41-46
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• 2002

A numerical simulation was made to determine the motion of particles in the fluid. The simulation is based on the Eulerian-Lagrangian method. The fluid motion was solved using a PISO-based finite-element method and a $\kappa-\epsilon$ model of turbulence. In the Lagrangian method for the solid phase, the trajectories of particles are calculated by integrating the equations of motion of a single Particle, and the collision between particles are taken into account. The influence of particles on the fluid phase is taken into account by introducing source terms in the Eulerian equations govering the fluid flow. It is known as the particle-source-in-cell (PSIC) method. Also, the turbulent effect in the particles and fluid notion is considered. The numerical results were compared with the experiment for a two-phase flow in a vertical pipe.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.4
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• pp.27-36
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• 2001

A new two-phase non-boiling convective heat transfer correlation for turbulent flow $(Re_{SL}>4000)$ in vertical tubes with different fluid flow patterns and fluid combinations was developed using experimental data available from the literature. The correlation presented herein originates from a careful analysis of the major non-dimensional parameters affecting two-phase heat transfer. This model takes into account the appropriate contributions of both the liquid and gas phases using the respective cross-sectional areas occupied by the two phases. A total of 255 data points from three available studies (which included the four sets of data) were used to determine the curve-fitted constants in the improved correlation. The performance of the new correlation was compared with two-phase correlations from the literature, which were developed for specific fluid combinations.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.219-222
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• 2005

A compressible two-fluid two-phase flow computation model using the stiffened-gas equation of state is formulated. Since the conservation equation system is of mixed type, it gives complex eigenvalues. The sonic speeds obtained from the individual single phase have been simply used in the literature for the fastest wave speeds necessary in the HLL scheme. This method has worked fine but proved to be quite diffusive according to our test. To improve the accuracy, we here propose to utilize the analytic eigenvalues evaluated from an approximate Jacobian matrix lot the fastest wave speeds. The interfacial transfer terms were dropped in constituting the Jacobian matrix for this purpose. The present scheme proved efficient, robust and accurate in comparison with other existing methods. We solved the cavitating flow problem using the present scheme. The result shows more detailed wave structure in the cavitating process caused by the strong expansion waves.

• The KSFM Journal of Fluid Machinery
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• v.3 no.3 s.8
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• pp.12-18
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• 2000

In this study, experimental and numerical analyses are carried out to investigate the performance of centrifugal pump with various air admitting conditions. Experiments on the pump performance under air-water two-phase flow are accomplished using a centrifugal pump with semi-open type impeller having three, five and seven blades, respectively. Also, the numerical analysis of turbulent air-water two-phase flow using the finite volume method has been carried out to obtain the pressure, velocities and void fraction on the basis of a so-called bubbly flow model with the constant size and shape of cavity. The results obtained through this study show the reasonable agreements within the range of bubbly flow regime. There are promising developments concerning application of the present study for the flow in a centrifugal pump with two-phase flow conditions and efforts must be followed to improve the turbulence model and two-phase flow model for turbomachinery.