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Vol 5 - Issue 1

Thermodynamics of Interfaces and Fluid Mechanics

List of Articles

Drop vaporization frequency response: an approximate analytical solution for mixed injection regimes

This work is devoted to a theoretical analysis of evaporating mass frequency response to pressure oscillations of a spray of repetitively injected drops into a combustion chamber. A single stationary spherical droplet continuously fed with the same liquid fuel, so that its volume remains constant in spite of the evaporation, the so-called ‘mean droplet’ in the Heidmann analogy, represents this vaporizing spray of droplets. The feeding is realized with a liquid-liquid heat transfer coefficient by using a source point placed at the mean droplet centre, in such a way that only radial thermal convection and conduction effects are allowed inside the droplet during the process. This feeding procedure is now viewed as a proper boundary condition that is a mixed or a generalized feeding regime controlling the whole process of liquid fuel injection into the combustion chamber. Drawing upon a linear analysis based on the Rayleigh criterion, the evaporating mass response factor is evaluated. Effects due to the variation of the heat transfer coefficient and of the process characteristic times are analysed. Especially, an abrupt increase in the response function is related to the influence of the value of a particular fuel thermodynamic coefficient.

Hill’s vortex considérations

We examine cases of stationary vortices that can appear inside spherical liquid drops. The first case is that of an incompressible external flow of uniform speed at infinity, leading the liquid in the drop by friction to form a Hill vortex. In the second case, the external fluid does not interact by friction with the liquid, but the drop is subjected to an axial temperature gradient causing a variation in surface tension. This time it is the induced movement which entrains the internal liquid. Note that the two situations can lead to the same Hill vortex. Combined effects are envisioned. We are also interested in the time factor in these phenomena.

The fire of weapons

In this short article, we give a summary of combustion-based weapons and their effects. Flame throwers and thermobaric weapons, bombs: napalm, explosive devices, phosphorus bombs are mentioned. Then it comes to missiles, the space army and weapons pollution.

Shifting interface in the spacetime

The macroscopic balance equations of the fluid interfaces were established by considering two scales of length and by means of some approximations, such as the conservation of the mixed velocity vector and of the gradient parallel to the crossing of the interfacial zone. We generalize this method to the case of four-interfaces in the presence of electromagnetic fields. The transition to space-time is indeed a means of obtaining a homogeneous presentation of the balance sheets.

Other issues :


Volume 17- 1

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Volume 18- 2

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Volume 19- 3

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Volume 20- 4

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Volume 21- 5

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