Method of calculation of a methane concentration field in gob areas with a known velocity field based on the model of stream tubes

The basis theory for the turbulent diffusion of jet and flame has been presented previously [1, 2]. But that one applies only in quiet surrounding air with the effects of buoyancy neglected. In the present paper, the theory is developed further by establishing an integral model for a jet in more general conditions with variable inclined angles, under effects of gravity and surrounding air velocity in any direction compared to the jet axis. The system of equations is closed by turbulence k-E model and is solved by 4th order Runge-Kutta method. In the first stage, the model is applied to predict the velocity field, the concentration field and with development of a 0.3 m diameter jet.

Download Full-text

Insight of thermally stratified Jeffrey fluid flow inside porous medium subject to chemical species and melting heat transfer

Advances in Mechanical Engineering ◽

10.1177/1687814019876187 ◽

2019 ◽

Vol 11 (9) ◽

pp. 168781401987618

Author(s):

Mubashar Javed ◽

Muhammad Farooq ◽

Aisha Anjum ◽

Shakeel Ahmad

Keyword(s):

Heat Transfer ◽

Velocity Field ◽

Thermal Stratification ◽

Heterogeneous Reaction ◽

Concentration Field ◽

Chemical Species ◽

Internal Heat ◽

Nonlinear Problems ◽

Deborah Number ◽

Jeffrey Fluid

This article concentrates on two-dimensional magnetohydrodynamic stagnation flow of Jeffrey liquid on a nonlinearly stretching sheet which possesses variable thickness. Simultaneous impact of melting as well as thermal stratification is specifically investigated in this study due to their tremendous involvement in plenty of natural and industrial processes. Internal heat generation and presence of chemical species are considered to ponder at heat transfer properties. Series solution has been obtained by solving the developed nonlinear problems. Physical behavior of various controlling parameters such as velocity, thermal, and concentration fields are investigated. It has been found that temperature field decays due to higher intensity of thermal stratification parameter, but thickness of thermal boundary layer boosts up. Larger Deborah number results in incremented velocity field. For uplifted wall thickness parameter, velocity field depreciates. Concentration field declines for enhanced parameters of homogeneous as well as heterogeneous reaction. Moreover, velocity is decreasing function of porosity parameter.

Download Full-text

Recovery of average effective methane concentration field in the region of Kara and Barents Seas using a passive location of the atmosphere by wind

10.1063/1.5079118 ◽

2018 ◽

Author(s):

V. A. Poddubny ◽

E. S. Dubinkina ◽

J. I. Markelov ◽

A. G. Buevich ◽

K. L. Antonov ◽

...

Keyword(s):

Methane Concentration ◽

Concentration Field ◽

Passive Location

Download Full-text

Effects of Heat and Mass Transfer on Peristaltic Flow of Carreau Fluid in a Vertical Annulus

Zeitschrift für Naturforschung A ◽

10.1515/zna-2010-1004 ◽

2010 ◽

Vol 65 (10) ◽

pp. 781-792 ◽

Cited By ~ 13

Author(s):

Sohail Nadeem ◽

Noreen Sher Akbar

Keyword(s):

Mass Transfer ◽

Velocity Field ◽

Shooting Method ◽

Numerical Solutions ◽

Concentration Field ◽

Peristaltic Flow ◽

Frame Of Reference ◽

Carreau Fluid ◽

Long Wavelength ◽

Vertical Annulus

This article is devoted to the study of peristaltic transport of a Carreau fluid in a vertical annulus under the consideration of long wavelength. The flow is investigated in a wave frame of reference moving with the velocity of the wave. Exact solutions have been evaluated for temperature and concentration field, while approximated analytical and numerical solutions are found for the velocity field using (i) the perturbation method and (ii) the shooting method. The effects of various emerging parameters are investigated graphically.

Download Full-text

The Lagrangian Picture, Part I : Fundamentals of the Lagrangian Approach to Solute Transport

Applied Stochastic Hydrogeology ◽

10.1093/oso/9780195138047.003.0014 ◽

2003 ◽

Author(s):

Yoram Rubin

Keyword(s):

Velocity Field ◽

Solute Transport ◽

Complex Geometry ◽

Concentration Field ◽

Breakthrough Curves ◽

Lagrangian Approach ◽

Travel Times ◽

Solute Fluxes ◽

Reactive Solutes ◽

Solute Particle

This chapter explores the principles of the Lagrangian approach to solute transport, with an emphasis on the dispersive action of the spatial variability of the velocity field. We start by developing the tools for characterizing the displacement of a single, small solute particle that will subsequently be used for characterization of the concentration’s variability and uncertainty, and we continue with a discussion of the stochastic description of solute travel times and fluxes. The principles presented in this chapter will be employed in chapter 10 to derive tools for applications such as macrodispersion coefficients, solute travel time moments, the moments of the solute fluxes and breakthrough curves, and transport of reactive solutes. As has been observed in many field studies and numerical simulations, the motion of solute bodies in geological media is complex, making the geometry of the solute bodies hard to predict. Furthermore, the concentration varies erratically, sometimes by orders of magnitude, over very short distances. The variability of the velocity field plays a significant role in shaping this complex geometry, and makes it impossible to characterize the concentration field deterministically. The alternatives we will pursue include characterizing the concentration through its moments such as the expected value and variance, and other descriptors of transport such as solute fluxes and travel times. This line was pursued in chapter 8 using the Eulerian framework. In this chapter we pursue this line from the Lagrangian perspective. Applications of these concepts are presented in chapter 10. Let us consider the displacement of a marked solute particle over time.

Download Full-text

Investigations on Hydrogen Distribution and Mitigation Measures in the Containment Under Severe Accident

Volume 4: Computational Fluid Dynamics, Neutronics Methods and Coupled Codes; Student Paper Competition ◽

10.1115/icone14-89010 ◽

2006 ◽

Author(s):

Jian-Jun Xiao ◽

Zhi-Wei Zhou ◽

Xing-Qing Jing

Keyword(s):

Velocity Field ◽

Concentration Field ◽

The Other ◽

Severe Accident ◽

Mitigation Measures ◽

Parameter Fluctuation ◽

Hydrogen Transport ◽

Hydrogen Distribution ◽

Flammability Limits ◽

Transport And Mixing

During severe accident oxidation of the metallic components of the reactor core and the core-concrete interaction will produce hydrogen which may threaten the integrity of the containment. It is important to predict hydrogen transport and mixing in the containment, in order to determine whether the mixture can locally reach flammability limits, and install the hydrogen mitigation devices at a reasonable and suitable position. Several turbulence models in FLUENT and GASFLOW were adopted in this paper to investigate hydrogen transport and mixing in the containment, and the results were compared. The study indicates that RNG k–ε model can obtain better simulation in parameter fluctuation, velocity field, and hydrogen concentration field than the other models’. The results calculated by algebraic model in GASFLOW are largely different from the other results in the simulation of mass diffusion, momentum diffusion, and parameter fluctuation. The results of k–ε model in GASFLOW have the similar trend as the results of FLUENT in velocity field and concentration field. Three hydrogen mitigation measures were also studied in a simple closed room using the code GASFLOW. The results indicate that the combination of recombiners and igniters is a safe and effective way to reduce the risk of hydrogen combustion.

Download Full-text

Large-scale structures of scalar and velocity in a turbulent jet flow

14th International Symposium on Particle Image Velocimetry ◽

10.18409/ispiv.v1i1.28 ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Jesse Reijtenbagh ◽

Jerry Westerweel ◽

Willem Van de Water

Keyword(s):

Velocity Field ◽

Finite Time ◽

Large Scale ◽

Concentration Field ◽

Turbulent Jet ◽

Moving Frame ◽

Mean Flow ◽

Turbulent Structures ◽

Large Scale Structures ◽

Scale Structures

We study the relation between large-scale structures in the concentration field with those in the velocity field in a dye-seeded turbulent jet. The scalar concentration in a plane is measured using laser-induced fluorescence. Uniform concentration zones of an advected scalar are identified using cluster analysis. We simultaneously measure the two-dimensional velocity field using particle image velocimetry. The structures in the velocity field are characterized by finite-time Lyapunov exponents. The measurement of the scalarand velocity fields moves with the mean flow. In this moving frame, turbulent structures remain in focus long enough to observe well-defined ridges of the finite-time Lyapunov field. This field gauges the rate of point separation along Lagrangian trajectories; it was measured both for future and past times since the instant of observation. The edges of uniform concentration zones are correlated with the ridges of the past-time Lyapunov field, but not with those of the future-time Lyapunov field.

Download Full-text

Turbulent transport of discharged ground water in oceanic bottom boundary layers in a water channel experiment

10.5194/os-2019-116 ◽

2020 ◽

Author(s):

Nils Karow ◽

Leonie Kandler ◽

Martin Brede ◽

Sven Grundmann

Keyword(s):

Velocity Field ◽

Ground Water ◽

Optical Measurement ◽

Research Training ◽

Turbulent Transport ◽

Water Channel ◽

Concentration Field ◽

Measurement Technology ◽

Sea Bed ◽

Measurement Area

Abstract. In the context of the DFG research training Group Baltic Transcoast the scalar transport of discharged submarine groundwater and the included tracer substances will be investigated. The research focus is the mixing of ground water under the influence of waves in shallow coastal water. The waves will be generated by a Piston type wave generator and can be varied with respect to the specific wave parameters. In the water channel a permeable sea bed model is installed which allows the intrusion of a florescent tracer fluid into the measurement area. The transport of this tracer in the water column is affected by the wave motion and will be analysed using optical measurement technology. The methods used are on the one hand the Particle Image Velocimetry, to determine the velocity field in the measurement area. On the other hand, simultaneous Laser Induced Florescence will be used to obtain the concentration field. Thus, the relation between the unsteady velocity field and the mixing of the tracer can be determined quantitatively.

Download Full-text