Geometry of bluff body wakes

Kalra, T.R.; Uhlherr, P. H. T.

doi:10.1002/cjce.5450510606

Cited by 12 publications

(4 citation statements)

References 15 publications

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“…The results shown in Fig. 4 are very reasonable, and the final length of the turbulent wake is in good agreement with available experimental data [26].…”

Section: Modeling Results and Discussionsupporting

confidence: 84%

Numerical Simulation of Single Aluminum Particle Combustion (Review)

Beckstead

Liang

Pudduppakkam

2005

Combust Explos Shock Waves

138

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A two-dimensional, unsteady-state, kinetic-diffusion-vaporization-controlled numerical model for aluminum particle combustion is presented. The model solves the conservation equations, while accounting for species generation and destruction with a 15-reaction kinetic mechanism. Two of the major phenomena that differentiate aluminum combustion from hydrocarbon-droplet combustion, namely, condensation of the aluminum-oxide product and subsequent deposition of part of the condensed oxide onto the particle, are accounted for in detail with a submodel for each phenomenon. The effect of the oxide cap in the distortion of the species and temperature profiles around the particle is included into the model. The results obtained from the model, which include two-dimensional species and temperature profiles, are analyzed and compared with experimental data. The combustion process is found to approach a diffusion-controlled process for the oxidizers (O 2 , CO 2 , and H 2 O) and conditions treated. The flame-zone location and thickness are found to vary with the oxidizer. The result shows that the exponent of the particle-diameter dependence of the burning time is not a constant and changes from ≈1.2 for smaller-diameter particles to ≈1.9 for larger-diameter particles. Owing to deposition of the aluminum oxide onto the particle surface, the particle velocity oscillates. The effect of pressure is analyzed for a few oxidizers. Key words: aluminum particle, two-dimensional unsteady-state numerical model, kinetic mechanism, effect of the nature of the gaseous oxidizer, condensed oxide, oxide dissociation, oxide cap, burning time, species and temperature fields INTRODUCTIONAluminum has been added to propellants for many years as an extra energy source for the propellant. Thus, research on the combustion mechanism of burning aluminum has been an ongoing effort. A very significant effort was expended in the 1960s and 1970s shortly after the effects of aluminum were first conceived. In an early study, Glassman [1] and Brzustowski and Glassman [2] recognized that metal combustion would be analogous to hydrocarbon-droplet combustion, that the D 2 law ought to be applied, and that ignition and combustion ought to depend on the melting and boiling points of the metal and the oxide. Glassman speculated that ig-

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“…The results shown in Fig. 4 are very reasonable, and the final length of the turbulent wake is in good agreement with available experimental data [26].…”

Section: Modeling Results and Discussionsupporting

confidence: 84%

Numerical Simulation of Single Aluminum Particle Combustion (Review)

Beckstead

Liang

Pudduppakkam

2005

Combust Explos Shock Waves

138

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“…The separation angle also increased with the increasing Reynolds number, and this phenomenon is consistent with the results of numerical simulation [13]. The empirical formula obtained by the experimental method was the functional relationship between the separation angle and the Reynolds number when the Reynolds number was between 30 and 750 [14]. Based on this, a similar modified empirical formula also appears and the Reynolds number was between 300 and 3000 [15].…”

Section: Introductionsupporting

confidence: 83%

The Symmetry and Stability of the Flow Separation around a Sphere at Low and Moderate Reynolds Numbers

Zhou

2021

Symmetry

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The flow separation state reflects the symmetry and stability of flow around spheres. The three-dimensional structures of flow around a rigid sphere at moderate Reynolds number (Re) between 20 and 400 by using finite volume method with adaptive mesh refinement are presented, and the process of separation angles changing from stable to oscillating state with increasing of Re is analyzed. The results show that the flow is steady, and the separation angles are stable and axisymmetric at Re in less than 200. The flow is unsteady and time-periodic, and the flow separation becomes regular fluctuations and asymmetric at Re = 300, which leads to the nonzero value of lateral force and the phase difference between lift and lateral force. At Re = 400, the flow is unsteady, non-periodic, and asymmetric, as is the flow separation. It’s concluded that the flow separation angle increases when Re increases within a range between 40 and 200. With Re continues to increase, the flow separation state changes from stable to periodically regular until quasi-periodically irregular. The vortex structure changes from no shedding to asymmetric periodic shedding, and finally to asymmetric and intermittently periodic vortex shedding. These results have important implications for the stability of flow around spheres.

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“…An increase in the viscosity ratio results at the incipient of the vortex at lower Reynolds number. When the viscosity ratio tends to infinity, the critical Reynolds number tends to 20, which is in agreement with the critical Reynolds number of 20 for vortex formation behind a solid sphere as determined through the extrapolation of the vortex's length to zero by Kalra and Uhlherr [25], and by the numerical simulations of solid sphere by Pruppacher et al [26] and by Lin and Lee [27]. A correlation to predict this behaviour was developed…”

Section: Flow Pattern In and Around A Liquid Dropmentioning

confidence: 69%

Simulating sedimentation of liquid drops

Waheed

Henschke

Pfennig

2004

Numerical Meth Engineering

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SUMMARYThis work was carried out to investigate the effect of fluid properties on the flow pattern and on the sedimentation velocity of an axisymmetric steady flow of a Newtonian fluid past a liquid drop in an unbounded region. The governing equations of motion were solved by the finite element method. The results show that the flow pattern of a liquid drop depends strongly both on the Reynolds number and on the ratio of the viscosity between the drop and the surrounding flowing fluids. The viscosity ratio in the range 0.02 < * < 50 has appreciable effect on the drag coefficient. Finally, a correlation for the sedimentation velocity is presented.

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Geometry of bluff body wakes

Cited by 12 publications

References 15 publications

Numerical Simulation of Single Aluminum Particle Combustion (Review)

Numerical Simulation of Single Aluminum Particle Combustion (Review)

The Symmetry and Stability of the Flow Separation around a Sphere at Low and Moderate Reynolds Numbers

Simulating sedimentation of liquid drops

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