Simplified two-group two-fluid model for three-dimensional two-phase flow Computational Fluid Dynamics for vertical upward flow

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.

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On Treatment of Negative Pressures in Fluid Dynamics

Heat Transfer: Volume 2 ◽

10.1115/ht2005-72500 ◽

2005 ◽

Author(s):

Iztok Tiselj ◽

Janez Gale

Keyword(s):

Fluid Dynamics ◽

Phase Transition ◽

Two Phase Flow ◽

Fluid Model ◽

Saturation Pressure ◽

Phase Flow ◽

Two Phase ◽

Negative Pressures ◽

Two Fluid Model ◽

Two Fluid

Rapid depressurization of a cold single-phase liquid leads to the onset of a vaporisation, i.e. the phase transition phenomena. Prior to the start and in the very first moment of the phase transition, pressure in the liquid may briefly drop to negative values, when initial liquid temperature is low enough. Metastable liquid in a state of tension is well known in static experiments, but is less known in the fluid dynamics. The present paper discusses some preliminary findings in the field of modeling of the negative pressures in transient water flows and subsequent phase transition with a single-pressure two-fluid model. A highly simplified single-pressure two-fluid model is used in the present work to describe the two-phase flow with negative liquid and positive vapor pressure. The assumption used at negative liquid pressures is equal temperature of liquid and newly generated vapor phase, while the gas pressure is assumed to be the saturation pressure at that temperature. Rather rough models seem to be sufficiently accurate due to the large uncertainty in the modeling of the single-to-two-phase flow transition, which strongly depends on the density of the nucleation sites in the liquid and at the wall.

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Analysis of Two-Phase Cavitating Flow with Two-Fluid Model Using Integrated Boltzmann Equations

Advances in Applied Mathematics and Mechanics ◽

10.4208/aamm.12-m1256 ◽

2013 ◽

Vol 5 (05) ◽

pp. 607-638 ◽

Cited By ~ 2

Author(s):

Shuhong Liu ◽

Yulin Wu ◽

Yu Xu ◽

Hua-Shu Dou

Keyword(s):

Turbulence Model ◽

Two Phase Flow ◽

Fluid Model ◽

Three Dimensional ◽

Cavitating Flow ◽

Phase Flow ◽

Two Phase ◽

Pump Sump ◽

Two Fluid Model ◽

Two Fluid

AbstractIn the present work, both computational and experimental methods are employed to study the two-phase flow occurring in a model pump sump. The two-fluid model of the two-phase flow has been applied to the simulation of the three-dimensional cavitating flow. The governing equations of the two-phase cavitating flow are derived from the kinetic theory based on the Boltzmann equation. The isotropic RNGk — ε — kcaturbulence model of two-phase flows in the form of cavity number instead of the form of cavity phase volume fraction is developed. The RNGk—ε—kcaturbulence model, that is the RNGk — eturbulence model for the liquid phase combined with thekcamodel for the cavity phase, is employed to close the governing turbulent equations of the two-phase flow. The computation of the cavitating flow through a model pump sump has been carried out with this model in three-dimensional spaces. The calculated results have been compared with the data of the PIV experiment. Good qualitative agreement has been achieved which exhibits the reliability of the numerical simulation model.

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SIMULATION METHODS OF TWO-PHASE FLOW BASED ON A HYPERBOLIC TWO-FLUID MODEL

Proceeding of First Thermal and Fluids Engineering Summer Conference ◽

10.1615/tfesc1.cmd.013060 ◽

2016 ◽

Author(s):

Moon-Sun Chung ◽

Sung-Jae Yi

Keyword(s):

Two Phase Flow ◽

Fluid Model ◽

Phase Flow ◽

Simulation Methods ◽

Two Phase ◽

Two Fluid Model ◽

Two Fluid

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Natural modes of the two-fluid model of two-phase flow

Physics of Fluids ◽

10.1063/5.0046189 ◽

2021 ◽

Vol 33 (3) ◽

pp. 033324

Author(s):

Alejandro Clausse ◽

Martín López de Bertodano

Keyword(s):

Two Phase Flow ◽

Fluid Model ◽

Phase Flow ◽

Two Phase ◽

Natural Modes ◽

Two Fluid Model ◽

Two Fluid

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A Physically Based, One-Dimensional Two-Fluid Model for Direct Contact Condensation of Steam Jets Submerged in Subcooled Water

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4029417 ◽

2015 ◽

Vol 1 (2) ◽

Cited By ~ 6

Author(s):

David Heinze ◽

Thomas Schulenberg ◽

Lars Behnke

Keyword(s):

Direct Contact ◽

Two Phase Flow ◽

Fluid Model ◽

Interfacial Area ◽

Phase Flow ◽

Two Phase ◽

One Dimensional ◽

Two Fluid Model ◽

Contact Condensation ◽

Two Fluid

A simulation model for the direct contact condensation of steam in subcooled water is presented that allows determination of major parameters of the process, such as the jet penetration length. Entrainment of water by the steam jet is modeled based on the Kelvin–Helmholtz and Rayleigh–Taylor instability theories. Primary atomization due to acceleration of interfacial waves and secondary atomization due to aerodynamic forces account for the initial size of entrained droplets. The resulting steam-water two-phase flow is simulated based on a one-dimensional two-fluid model. An interfacial area transport equation is used to track changes of the interfacial area density due to droplet entrainment and steam condensation. Interfacial heat and mass transfer rates during condensation are calculated using the two-resistance model. The resulting two-phase flow equations constitute a system of ordinary differential equations, which is solved by means of the explicit Runge–Kutta–Fehlberg algorithm. The simulation results are in good qualitative agreement with published experimental data over a wide range of pool temperatures and mass flow rates.

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Numerical Simulation and Analysis on Spray Drift Movement of Multirotor Plant Protection Unmanned Aerial Vehicle

Energies ◽

10.3390/en11092399 ◽

2018 ◽

Vol 11 (9) ◽

pp. 2399 ◽

Cited By ~ 5

Author(s):

Fengbo Yang ◽

Xinyu Xue ◽

Chen Cai ◽

Zhu Sun ◽

Qingqing Zhou

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Droplet Size ◽

Wind Field ◽

Flow Model ◽

Two Phase Flow ◽

Plant Protection ◽

Three Dimensional ◽

Phase Flow ◽

Two Phase

In recent years, multirotor unmanned aerial vehicles (UAVs) have become more and more important in the field of plant protection in China. Multirotor unmanned plant protection UAVs have been widely used in vast plains, hills, mountains, and other regions, and become an integral part of China’s agricultural mechanization and modernization. The easy takeoff and landing performances of UAVs are urgently required for timely and effective spraying, especially in dispersed plots and hilly mountains. However, the unclearness of wind field distribution leads to more serious droplet drift problems. The drift and distribution of droplets, which depend on airflow distribution characteristics of UAVs and the droplet size of the nozzle, are directly related to the control effect of pesticide and crop growth in different growth periods. This paper proposes an approach to research the influence of the downwash and windward airflow on the motion distribution of droplet group for the SLK-5 six-rotor plant protection UAV. At first, based on the Navier-Stokes (N-S) equation and SST k–ε turbulence model, the three-dimensional wind field numerical model is established for a six-rotor plant protection UAV under 3 kg load condition. Droplet discrete phase is added to N-S equation, the momentum and energy equations are also corrected for continuous phase to establish a two-phase flow model, and a three-dimensional two-phase flow model is finally established for the six-rotor plant protection UAV. By comparing with the experiment, this paper verifies the feasibility and accuracy of a computational fluid dynamics (CFD) method in the calculation of wind field and spraying two-phase flow field. Analyses are carried out through the combination of computational fluid dynamics and radial basis neural network, and this paper, finally, discusses the influence of windward airflow and droplet size on the movement of droplet groups.

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