scholarly journals Validation of NEPTUNE-CFD Two-Phase Flow Models Using Experimental Data

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
Author(s):  
Jorge Pérez Mañes ◽  
Victor Hugo Sánchez Espinoza ◽  
Sergio Chiva Vicent ◽  
Michael Böttcher ◽  
Robert Stieglitz
Keyword(s):  
Experimental Data ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Model Parameters ◽  
Phase Flow ◽  
Cfd Model ◽  
Two Phase ◽  
Flow Models ◽  
Phase Models ◽  
Good Agreement

This paper deals with the validation of the two-phase flow models of the CFD code NEPTUNEC-CFD using experimental data provided by the OECD BWR BFBT and PSBT Benchmark. Since the two-phase models of CFD codes are extensively being improved, the validation is a key step for the acceptability of such codes. The validation work is performed in the frame of the European NURISP Project and it was focused on the steady state and transient void fraction tests. The influence of different NEPTUNE-CFD model parameters on the void fraction prediction is investigated and discussed in detail. Due to the coupling of heat conduction solver SYRTHES with NEPTUNE-CFD, the description of the coupled fluid dynamics and heat transfer between the fuel rod and the fluid is improved significantly. The averaged void fraction predicted by NEPTUNE-CFD for selected PSBT and BFBT tests is in good agreement with the experimental data. Finally, areas for future improvements of the NEPTUNE-CFD code were identified, too.

Two-Phase Flow-Induced Forces on Bends in Small Scale Tubes

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
M. F. Cargnelutti ◽  
S. P. C. Belfroid ◽  
W. Schiferli
Keyword(s):  
Experimental Data ◽  
Structural Integrity ◽  
Two Phase Flow ◽  
Experimental Results ◽  
Small Scale ◽  
Phase Flow ◽  
Momentum Exchange ◽  
Two Phase ◽  
Worst Case ◽  
Good Agreement

Two-phase flow occurs in many situations in industry. Under certain circumstances, it can be a source of flow-induced vibrations. The forces generated can be sufficiently large to affect the performance or efficiency of an industrial device. In the worst-case scenario, the mechanical forces that arise may endanger structural integrity. Thus, it is important to take these forces into account in designing industrial machinery to avoid problems during operation. Although the occurrence of such forces is well known, not much is known about their magnitudes because, unfortunately, the amount of experimental data available in literature are rather limited. This paper describes the experiments performed to measure forces in 6 mm diameter tubing containing a bend. Experiments are performed on bends of different radii, with the bend positioned horizontally or vertically. The experimental results are analyzed based on flow regime and bend configuration. A comparison with available experimental results for bigger internal pipe diameter shows a general good agreement. To improve future predictions, a simple model based on momentum exchange is proposed to estimate the forces generated by multiphase flow. The proposed model shows a good agreement with the experimental data.

Performance of Two-Phase Flow Models on the Prediction of Oscillatory Flow Conditions

2016 ◽  
Author(s):  
Catalina Posada ◽  
Paulo Waltrich
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Pressure Gradient ◽  
Two Phase Flow ◽  
Percentage Error ◽  
Phase Flow ◽  
Liquid Holdup ◽  
Two Phase ◽  
Flow Models ◽  
Absolute Percentage Error

The present investigation presents a comparative study between two-phase flow models and experimental data. Experimental data was obtained using a 42 m long, 0.05 m ID tube system. The experimental data include conditions for pressures ranging from 1.2 to 2.8 bara, superficial liquid velocities 0.02–0.3 m/s, and superficial gas velocity ranges 0.17–26 m/s. The experimental data was used to evaluate the performance of steady-state empirical and mechanistic models while estimating liquid holdup and pressure gradient under steady-state and oscillatory conditions. The purpose of this analysis is first to evaluate the accuracy of the models predicting the liquid holdup and pressure gradient under steady-state conditions. Then, after evaluating the models under state-steady conditions, the same models are used to predict the same parameters for oscillatory and periodic conditions for similar gas and liquid velocities. The transient multiphase flow simulator OLGA, which has been widely used in the oil and gas industry, was implemented to model one oscillatory case to evaluate the prediction improvement while using a transient instead of a steady-state model to predict oscillatory flows. For the model with best performance for steady-state pressure gradient prediction, the absolute percentage error is 12% for Uls = 0.02 m/s and 5% for Uls = 0.3. For oscillatory conditions, the absolute percentage error is 30% for Uls = 0.02 m/s and 4% for Uls = 0.3. OLGA results underpredict the experimental pressure gradient under oscillatory conditions with errors up to 30%. Therefore, it was possible to conclude that the models can predict the average of the oscillatory data almost as well as for steady-state conditions.

Mach Number Scaling of Single-Component, Two-Phase Flow

1993 ◽  
Vol 115 (4) ◽  
pp. 772-777
Author(s):  
D. E. Nikitopoulos
Keyword(s):  
Experimental Data ◽  
Mach Number ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Critical Mass ◽  
Critical Flow ◽  
Phase Flow ◽  
Homogeneous State ◽  
Two Phase ◽  
Good Agreement

A simple two-fluid formulation is used to investigate compressibility effects and Mach number scaling for equilibrium, evaporating two-phase flow. The definition of the local two-phase Mach number emerges from a critical flow analysis. Comparisons of the theoretical critical mass flux with existing experimental data obtained in steam-water flows show very good agreement for moderate and high qualities over a wide critical pressure range. Within this quality range the predicted critical mass flux is quite insensitive to the velocity ratio. The analysis confirms previous observations, based on homogeneous flow models, indicating that in variable area ducts the critical state does not occur at a geometrical throat. Results of existing critical flow experiments in slowly diverging ducts are discussed in the light of this conclusion. A way from the neighborhood of the flash horizon, pressure-drop and kinetic energy changes are shown to scale with similar local Mach functions as those of single-phase compressible flow. Existing experimental data from vertical-upwards and horizontal two-phase flows in pipes indicate that the Mach number calculated on the basis of the local homogeneous state provides the optimum scaling performance. Scaling of the same experimental data using a Mach number based on the local nonhomogeneous state provides results that are in reasonably good agreement with the theoretical scaling guidelines and predictions, but is handicapped by considerable scatter in the scaled experimental variables.

Evaluation of Advanced Two-Phase Flow and Combustion Models for Predicting Low Emission Combustors

2000 ◽  
Vol 123 (4) ◽  
pp. 817-823 ◽  
Author(s):  
G. Klose ◽  
R. Schmehl ◽  
R. Meier ◽  
G. Maier ◽  
R. Koch ◽  
...  
Keyword(s):  
Experimental Data ◽  
Two Phase Flow ◽  
Numerical Models ◽  
Computational Method ◽  
Phase Model ◽  
Combustion Model ◽  
Phase Flow ◽  
Two Phase ◽  
Low Emission ◽  
Good Agreement

The development of low-emission aero-engine combustors strongly depends on the availability of accurate and efficient numerical models. The prediction of the interaction between two-phase flow and chemical combustion is one of the major objectives of the simulation of combustor flows. In this paper, predictions of a swirl stabilized model combustor are compared to experimental data. The computational method is based on an Eulerian two-phase model in conjunction with an eddy dissipation (ED) and a presumed-shape-PDF (JPDF) combustion model. The combination of an Eulerian two-phase model with a JPDF combustion model is a novelty. It was found to give good agreement to the experimental data.

Effect of Liquid Viscosity on Two-Phase Flow Development in a Vertical Large Diameter Pipe

2018 ◽  
Author(s):  
Abubakr Ibrahim ◽  
Buddhika Hewakandamby ◽  
Zhilin Yang ◽  
Barry Azzopardi
Keyword(s):  
Experimental Data ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Superficial Velocity ◽  
Phase Flow ◽  
Liquid Viscosity ◽  
Two Phase Flows ◽  
Two Phase ◽  
Entrance Effect ◽  
Flow Development

Effect of injector geometry on two phase flows is of profound importance to industry. If the injection method is found to vary the flow characteristics dramatically, it can be employed to obtain desirable two phase flow regimes/attributes and avoid rather unsought conditions. This could potentially save a lot of costs in the extraction and transportation of oil and gas as well as in many other applications. Moreover, the issue of flow development and dependency on the injection conditions is essential when modelling two phase flows. A lot of experimental data and empirical models may have been developed based on systems that may not be fully developed. Therefore, inaccurate modelling of the physical interactions of the flow gets adopted, and hence large divergence between models and experimental data produced by different researchers often transpires. Most of the published studies on entrance effect were conducted on air-water or steam-water systems because of their relevance to heat transfer units in the nuclear industry. This paper presents an extensive experimental investigation into the issue of flow development using two approaches; measuring void fraction at five axial stations along the test section, and using different geometries for bubble injection into the base of the pipe. The study focuses on how the entrance effect is influenced by the liquid viscosity. The experiments were conducted in a 127 mm diameter vertical pipe. The investigation is achieved by contrasting 180 runs produced using three different injector geometries, the runs were repeated using 4 different oil viscosities, making 2160 experimental run. Gas superficial velocity (Ugs) was varied between 0.01–5.40 m/s, while liquid superficial velocity (Uls) between 0.07–0.86 m/s. The viscosities investigated span between 4.0 cP up to 104.6 cP. The void fraction was measured using Electrical Capacitance Tomography (ECT) and the Wire Mesh Sensor (WMS). That in addition to differential pressure measurements.

Numerical Simulation of the Air-Water Two-Phase Flow Across a 90-Degree Vertical-Upward Elbow

2020 ◽  
Author(s):  
Shouxu Qiao ◽  
Wenyi Zhong ◽  
Sijia Hao ◽  
Peiyao Qi ◽  
Sichao Tan
Keyword(s):  
Liquid Phase ◽  
Void Fraction ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Interfacial Area ◽  
Phase Flow ◽  
Two Phase ◽  
Interfacial Area Concentration ◽  
Flow Models

Abstract The present study investigates the air-water two-phase flow across a 90-degree vertical-upward elbow with the computational fluid dynamics (CFD) simulation. The Eulerian-Eulerian two-fluid model and the Multi Size Group (MUSIG) model are used to predict the development of the detailed interfacial structures between the two phases. The axial development of the void fraction and the interfacial area concentration are investigated and benchmarked with the experimental data measured using the four-sensor conductivity probe. It is concluded that CFD simulation can predict the characteristics distributions of void fraction and interfacial area concentration and their development downstream of the elbow. The double-peaked void fraction distribution is found to be caused by the secondary flow induced by the elbow. The liquid phase on the outer curvature moves to the inner curvature and forms a double counter rotating vortex, entraining the bubbles to form a double-peaked distribution. The elbow effects become dissipated between 33 and 63 hydraulic diameters. The simulation results of liquid-phase and gas-phase parameters can be used to develop the theoretical two-phase flow models for the elbow region.

Average Volumetric Concentration in Two-Phase Flow Systems

1965 ◽  
Vol 87 (4) ◽  
pp. 453-468 ◽  
Author(s):  
N. Zuber ◽  
J. A. Findlay
Keyword(s):  
Experimental Data ◽  
Two Phase Flow ◽  
Weighted Average ◽  
Phase Flow ◽  
Nonuniform Flow ◽  
Volumetric Concentration ◽  
Two Phase ◽  
Wide Pressure Range ◽  
Wide Pressure ◽  
Good Agreement

A general expression which can be used either for predicting the average volumetric concentration or for analyzing and interpreting experimental data is derived. The analysis takes into account both the effect of nonuniform flow and concentration profiles as well as the effect of the local relative velocity between the phases. The first effect is taken into account by a distribution parameter, whereas the latter is accounted for by the weighted average drift velocity. Both effects are analyzed and evaluated. The results predicted by the analysis are compared with experimental data obtained for various two-phase flow regimes, with various liquid-gas mixtures in adiabatic, vertical flow over a wide pressure range. Good agreement with experimental data is shown.

Evaluation of Advanced Two-Phase Flow and Combustion Models for Predicting Low Emission Combustors

2000 ◽  
Author(s):  
G. Klose ◽  
R. Schmehl ◽  
R. Meier ◽  
G. Meier ◽  
R. Koch ◽  
...  
Keyword(s):  
Experimental Data ◽  
Two Phase Flow ◽  
Numerical Models ◽  
Computational Method ◽  
Phase Model ◽  
Combustion Model ◽  
Phase Flow ◽  
Two Phase ◽  
Low Emission ◽  
Good Agreement

The development of low emission aero engine combustors strongly depends on the availability of accurate and efficient numerical models. The prediction of the interaction between two-phase flow and chemical combustion is one of the major objectives of the simulation of combustor flows. In this paper, predictions of a swirl stabilized model combustor are compared to experimental data. The computational method is based on an Eulerian two-phase model in conjunction with an Eddy Dissipation (ED) and a presumed-shape-PDF (JPDF) combustion model. The combination of an Eulerian two-phase model with a JPDF combustion model is a novelty. It was found to give good agreement to the experimental data.

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