A new treatment of capillarity to improve the stability of IMPES two-phase flow formulation

2010 ◽  
Vol 39 (10) ◽  
pp. 1923-1931 ◽  
Author(s):  
Jisheng Kou ◽  
Shuyu Sun
Keyword(s):  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
New Treatment ◽  
The Stability

The influence of the Stokes and Archimedes forces on the stability of a two-phase flow

2003 ◽  
Vol 3 ◽  
pp. 266-270
Author(s):  
B.H. Khudjuyerov ◽  
I.A. Chuliev
Keyword(s):  
Spectral Method ◽  
Stability Region ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Solid Phase ◽  
Stability Characteristic ◽  
Phase Flow ◽  
Two Phase ◽  
The Stability

The problem of the stability of a two-phase flow is considered. The solution of the stability equations is performed by the spectral method using polynomials of Chebyshev. A decrease in the stability region gas flow with the addition of particles of the solid phase. The analysis influence on the stability characteristic of Stokes and Archimedes forces.

scholarly journals A New Capacitance Sensor for Measuring the Void Fraction of Two-Phase Flow Through Tube Bundles

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2088
Author(s):  
Wael Ahmed ◽  
Adib Fatayerji ◽  
Ahmed Elsaftawy ◽  
Marwan Hassan ◽  
David Weaver ◽  
...  
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Tube Bundle ◽  
Local Variation ◽  
Phase Flow ◽  
Capacitance Sensor ◽  
Two Phase ◽  
Element Analysis ◽  
Tube Bundles ◽  
The Stability

Evaluating the two-phase flow parameters across tube bundles is crucial to the analysis of vibration excitation mechanisms. These parameters include the temporal and local variation of void fraction and phase redistribution. Understanding these two-phase parameters is essential to evaluating the stability threshold of tube bundle configurations. In this work, capacitance sensor probes were designed using finite element analysis to ensure high sensor sensitivity and optimum response. A simulation-based approach was used to calibrate and increase the accuracy of the void fraction measurement. The simulation results were used to scale the normalized capacitance and minimize the sensor uncertainty to ±5%. The sensor and required conditioning circuits were fabricated and tested for measuring the instantaneous void fraction in a horizontal triangular tube bundle array under both static and dynamic two-phase flow conditions. The static calibration of the sensor was able to reduce the uncertainty to ±3% while the sensor conditioning circuit was able to capture instantaneous void fraction signals with frequencies up to 2.5 kHz.

The Flow-Structure Couplings of Fluidelastic Instability and the Effect of Frequency Detuning in Triangular Tube Bundles Subjected to a Two-Phase Flow

2021 ◽  
Author(s):  
Omar Sadek ◽  
Atef Mohany ◽  
Marwan A. Hassan
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Frequency Detuning ◽  
Two Phase ◽  
Stability Threshold ◽  
Damping Parameter ◽  
Tube Bundles ◽  
The Stability ◽  
Air Void

Abstract For decades, fluidelastic instability (FEI) has been known to cause dramatic mechanical failures in tube bundles. Therefore, it has been extensively studied to mitigate its catastrophic consequences. Most of these studies were conducted in controlled experiments where significant simplifications to the geometry and flow conditions were utilized. One of these simplifications is the assumption that all tubes have the same dynamic characteristics. However, in steam generators with U-bend tube configuration, the natural frequencies of tubes are nonuniform due to manufacturing tolerances and tubes' curvature in the U-bend region. Thus, this investigation aims to understand the rule of frequency variation (detuning) on FEI in two-phase flow. This includes investigating the effect of detuning on transverse and streamwise FEI for air-water mixture flow. The role of FEI damping and stiffness couplings was investigated over the entire range of air void fraction, or equivalently, the mass-damping parameter. It was found that frequency detuning could elevate the stability threshold caused by either coupling at high air void fraction in the case of transverse FEI. Furthermore, the frequency detuning had a marginal effect on the stability threshold for water flow. It was observed that the mass-damping parameter has a critical impact on FEI under detuning conditions.

Stability Analysis of Chaotic Wavy Stratified Fluid-Fluid Flow With the 1D Fixed-Flux Two-Fluid Model

2016 ◽  
Author(s):  
Avinash Vaidheeswaran ◽  
William D. Fullmer ◽  
Krishna Chetty ◽  
Raul G. Marino ◽  
Martin Lopez de Bertodano
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Two Phase Flow ◽  
Chaotic Behavior ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Two Fluid Model ◽  
The Stability ◽  
Two Fluid

The one-dimensional fixed-flux two-fluid model (TFM) is used to analyze the stability of the wavy interface in a slightly inclined pipe geometry. The model is reduced from the complete 1-D TFM, assuming a constant total volumetric flux, which resembles the equations of shallow water theory (SWT). From the point of view of two-phase flow physics, the Kelvin-Helmholtz instability, resulting from the relative motion between the phases, is still preserved after the simplification. Hence, the numerical fixed-flux TFM proves to be an effective tool to analyze local features of two-phase flow, in particular the chaotic behavior of the interface. Experiments on smooth- and wavy-stratified flows with water and gasoline were performed to understand the interface dynamics. The mathematical behavior concerning the well-posedness and stability of the fixed-flux TFM is first addressed using linear stability theory. The findings from the linear stability analysis are also important in developing the eigenvalue based donoring flux-limiter scheme used in the numerical simulations. The stability analysis is extended past the linear theory using nonlinear simulations to estimate the Largest Lyapunov Exponent which confirms the non-linear boundedness of the fixed-flux TFM. Furthermore, the numerical model is shown to be convergent using the power spectra in Fourier space. The nonlinear results are validated with the experimental data. The chaotic behavior of the interface from the numerical predictions is similar to the results from the experiments.

RELAXATION TWO-PHASE FLOW MODELS AND THE SUBCHARACTERISTIC CONDITION

2011 ◽  
Vol 21 (12) ◽  
pp. 2379-2407 ◽  
Author(s):  
TORE FLÅTTEN ◽  
HALVOR LUND
Keyword(s):  
Two Phase Flow ◽  
Relaxation Processes ◽  
Phase Flow ◽  
Equilibrium System ◽  
Two Phase ◽  
Flow Models ◽  
Wave Velocities ◽  
Relaxation Systems ◽  
The Stability ◽  
Analytical Expressions

The subcharacteristic condition for hyperbolic relaxation systems states that wave velocities of an equilibrium system cannot exceed the corresponding wave velocities of its relaxation system. This condition is central to the stability of hyperbolic relaxation systems, and is expected to hold for most such models describing natural phenomena. In this paper, we study a hierarchy of two-phase flow models. We consider relaxation with respect to volume transfer, heat transfer and mass transfer. We formally verify that our relaxation processes are consistent with the first and second laws of thermodynamics, and present analytical expressions for the wave velocities for each model in the hierarchy. Through an appropriate choice of variables, we prove directly by sums-of-squares that for all relaxation processes considered, the subcharacteristic condition holds for any thermodynamically stable equation of state.

ADAPTIVE FINITE ELEMENT METHODS FOR COMPRESSIBLE TWO-PHASE FLOW

2000 ◽  
Vol 10 (07) ◽  
pp. 963-989 ◽  
Author(s):  
E. BURMAN
Keyword(s):  
Two Phase Flow ◽  
Posteriori Error ◽  
Diffusion Method ◽  
Posteriori Error Estimate ◽  
Phase Flow ◽  
Adaptive Finite Element ◽  
Adaptive Finite Element Methods ◽  
Two Phase ◽  
Two Space Dimensions ◽  
The Stability

We apply the adaptive streamline diffusion method for compressible flow in conservation variables using P1×P0 finite elements to a conservative model of two-phase flow. The adaptive algorithm is based on an a posteriori error estimate involving certain stability factors related to a linearized dual problem. For a model problem we prove that the stability factors are bounded. We compute the stability factors for some numerical examples in one- and two-space dimensions.

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