Modeling high-speed viscous liquid sheet atomization

Hydrodynamic and hydromagnetic stability

Modeling drop size distributions

Review of theory of distortion and disintegration of liquid streams

This paper presents a physicist's approach to Rayleigh-Benard convection widely illustrated with experimental results. The basis of the mechanism of the instability is simply presented with physical reasons for the existence of a critical threshold. A detailed examination of the spatial organization is made with discussion of ordered and disordered structures. Furthermore it is shown that the measurements of the local velocity give a good quantitative description of the convective state. A complete parallel between the Rayleigh-Benard convection near onset and a critical phenomenon is given in the framework of a mean field approach, including both spatial as well as temporal effects. Non-Boussinesq convection is presented as symmetry breaking, changing the second order transition into a (partially) first order transition. The last section is devoted to the ever present but still not completely understood question of the dynamics of the convective pattern; the importance of the existence and motio...

Rayleigh-bénard convection

This paper reports a temporal instability analysis of a moving thin viscous liquid sheet in an inviscid gas medium. The results show that surface tension always opposes, while surrounding gas and relative velocity between the sheet and gas favour, the onset and development of instability. It is found that there exist two modes of instability for viscous liquid sheets – aerodynamic and viscosity-enhanced instability – in contrast to inviscid liquid sheets for which the only mode of instability is aerodynamic. It is also found that axisymmetrical disturbances control the instability process for small Weber numbers, while antisymmetrical disturbances dominate for large Weber numbers. For antisymmetrical disturbances, liquid viscosity, through the Ohnesorge number, enhances instability at small Weber numbers, while liquid viscosity reduces the growth rate and the dominant wavenumber at large Weber numbers. At the intermediate Weber-number range, Liquid viscosity has complicated effects due to the interaction of viscosity-enhanced and aerodynamic instabilities. In this range, the growth rate curve exhibits two local maxima, one corresponding to aerodynamic instability, for which liquid viscosity has a negligible effect, and the other due to viscosity-enhanced instability, which is influenced by the presence and variation of liquid viscosity. For axisymmetrical disturbances, liquid viscosity always reduces the growth rate and the dominant wavenumber, aerodynamic instability always prevails, and although the regime of viscosity-enhanced instability is always present, its growth rate curve does not possess a local maximum.

On the temporal instability of a two-dimensional viscous liquid sheet

Abstract-A distribution function that is of the Nukiyama-Tanasawa type was derived using the information entropy. A simplified expression is obtained if the limits of the droplet size are assumed to be zero and infinity. This distribution function has only one adjustable constant. When compared with experimental data, agreement is reasonable. Incorporating appropriate minimum and maximum droplet diameters would only be necessary if the experimental data are very narrowly distributed. This can be done and is not a restriction on the deriv ed distribution function.

Droplet size distribution: a derivation of a Nukiyama-Tanasawa type distribution function

The results from visual observations and measurements of flows over axisymmetric conducted, and vertically mounted bluff-body combustors are presented for low Reynolds number. The flow visualization is accomplished by adding TiCI4 vapor into the central gaseous propane jet for cole reacting and combusting flows, or by injecting TiCI4-N2 mixture into the flow field behind bluff-body combustors through a probe for pure annular air jet. Vertical laser light sheets provide a remarkably detailed visualization of the dynamic structures in the recirculating zone behind the bluff-body combustors. For the pure annular air jet, an analytical expression was used to correlate the experimental data for the length of the recirculating zone as a function of annular Reynolds number This expression is used in the laminar, transitional and fully turbulent regimes. For the cold reacting flow, another analytical expression is used to correlate the experimental data for the axial location o Forward stagnation point as a funct...

A Study of Cold and Combusting Flow Around Bluff-Body Combustors

In this paper, the joint droplet size and velocity distribution is derived by applying information theory to the atomization process, along with the normalization of the probability distribution function and the physical conservation laws of mass, momentum and energy. The obtained distribution contains the Weber number as a variable, and agrees with experimental observations. An equation for the Sauter mean diameter (D32) is obtained which agrees with several of the expressions that have been obtained from correlations of experimental data. When the Weber number exceeds 4000, the results given by Li and Tankin (1987) are appropriate.

Derivation of Droplet Size Distribution in Sprays By Using Information Theory

A Mach-Zehnder interferometer was used to stud two-dimensional Benard convection cells. The experiments were performed with distilled water and sea water in the region where density is a linear function of temperature. Two-dimensional convection rolls were formed with Rayleigh numbers as great as 23400. Reversal in the temperature profile was obtained for R/Rc ≥ 3·8, and an overshoot of about 6% was observed at R/Rc = 9·2 and 13·8. This agrees with the values predicted theoretically by Veronis (1966) for stress-free boundaries and Royal (1969) for rigid boundaries. This disagrees with the experimental results of Gille (1967), who reports an overshoot of only 1 ½% at R/Rc = 16. Many of the other results agree with those of other experimenters, such as the relation between the cell height-to-width ratio and Rayleigh number, the relation between the Nusselt number and Rayleigh number, and the value of the critical Rayleigh number.

Richard S. Tankin

Papers

On the temporal instability of a two-dimensional viscous liquid sheet

Droplet size distribution: a derivation of a Nukiyama-Tanasawa type distribution function

A Study of Cold and Combusting Flow Around Bluff-Body Combustors

Derivation of Droplet Size Distribution in Sprays By Using Information Theory

Interferometric study of two-dimensional Benard convection cells