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4 edition of Modelling density variation due to phase change during droplet impact found in the catalog.

Modelling density variation due to phase change during droplet impact

Mehdi Raessi

# Modelling density variation due to phase change during droplet impact

## by Mehdi Raessi

Written in English

Edition Notes

Thesis (M.A.Sc.) -- University of Toronto, 2003.

The Physical Object ID Numbers Series Canadian theses = -- Thèses canadiennes Format Microform Pagination 1 microfiche : negative. Open Library OL21299031M ISBN 10 0612844102 OCLC/WorldCa 57064110

In this paper, this phase field model in axisymmetric coordinates is used to numerically investigate the dynamics of droplet impact on solid surfaces. The numerical method is based on the energy stable scheme developed by Gao and Wang,20 Our objective is to quantify the influence of individual parameters on the droplet impact dynamics. Quantification of metal droplets ejected due to impinging gas jet on the surface of liquid metal is an important parameter for the understanding and for the modeling of the refining kinetics of reactions in slag-metal emulsion zone. In the present work, a numerical study has been carried out to critically examine the applicability of droplet generation rate correlation previously proposed by.

Phase separation of formation fluids in the subsurface introduces hydrodynamic perturbations which are critical for mass and energy transport of geofluids. Here, we present pore-scale lattice-Boltzmann simulations to investigate the hydrodynamical response of a porous system to the emergence of non-wetting droplets under background hydraulic gradients.   droplet science; explosive evaporation; multiphase physics; phase change; condensate freezing; Due to its frequent occurrence in nature and in everyday societal and technological applications, freezing of supercooled water has been studied intensively for decades (1 ⇓ ⇓ ⇓ ⇓ –6).Models that aim at describing and predicting ice nucleation, ice adhesion, the conditions for atmospheric.

The droplet model takes into account the variation of the droplet size due to condensation or evaporation according to the local supersaturation condition. Most of such works focused on the simulation of a small portion of the well mixed cloud-core and introduced an external forcing to reproduce the inflow of energy due to the larger-scale. The droplet impact velocity, viscosity and the nature of the solid surface (such as CA) are the key parameters. It should be noted that the dynamic contact angle (DCA) plays an important role in the problem of impinging of a droplet, as referred to in Liu. It decides the shape of the droplet during .

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### Modelling density variation due to phase change during droplet impact by Mehdi Raessi Download PDF EPUB FB2

The total volume of the droplet decreases during the impact process due to evaporation of some of the liquid. After the moment of impact at t ≈ the surface area of the liquid-vapor interface decreases rapidly for a short moment, which corresponds to the rapid wetting of the solid surface in the first few moments of the by: 2.

The predicted gas velocity and droplet velocity during combustion, gas temperature, droplet temperature, fuel vapor concentration, and oxygen concentration, using the full two-fluid model with a k-ε-k p two-phase turbulence model, a droplet evaporation model, and an EBU combustion model, are shown in Figs.

–, respectively. It is seen. The external phase, also called the nondroplet phase, forms the solid polymeric scaffold while the internal phase, or the droplet phase, consists of oil or water droplets (Silverstein, b). Simply put, the emulsion of oil in an aqueous/polymer phase allows for the development of a polymer shell around the oil droplets, resulting in a porous.

There are also a number of modeling studies on the droplet impact [16] [17][18][19] showing the details of the fluid and temperature fields inside the droplet during the impact process.

Studies. Droplet radius (r) and Wetness fraction (WF) or the heat release rate due to phase change ($$\dot{Q}$$) are important parameters in the design and operation of high-pressure (HP) wet steam equipment. However, heat transfer and phase change during impact were ignored.

An improved model was proposed by Pasandideh-Fard et al. () to track droplet free surface and solidification front. Drawing. The model of Bussmann et al., though three-dimensional, did not consider heat transfer and phase change during droplet impact.

Recently Zheng and Zhang [17] developed an adaptive level set method for moving boundary problems and applied the model to droplet spreading and solidification. Most of the studies reported for droplet impact and spreading on a substrate in a thermal spray coating process assume that droplet material solidifies as a pure substance, i.e., phase change occurs at a fixed temperature.

The alloy-type behavior of the droplet impact where it solidifies within liquidus and solidus temperature is not well reported. M. Raessi, J. Mostaghimi, Three-dimensional Modeling of Density Variation due to Phase Change in Complex Free Surface Flows, Numer. Heat Transfer Part B – Fundamental, 47 (6),p – Article; Google Scholar.

Thin solidification layers are developed at the centre and edges of the droplet right after the impact at ms; the solidification layers progress to the most contact surface as the droplets spreads at ms; the solidification rapidly takes over the droplet by ms; only a fraction of liquid remains within the internal edges of the.

Phase change and droplet dynamics for a free falling water droplet. During freezing, the water density decreases and the liquid volume expands, As the droplet accelerates, the aerodynamic forces tend to distort the original shape of the droplet.

Due to shear interaction of the two phases across the liquid-gas interface, the droplet has. It depends. Due to molecular rearrangement, density can change sharply at phase transition but it really depends on the phase transition and how you control temperature, pressure or both.

Take water for instance: Source: Water density This is a pl. Thermal shrinkage is a phenomenon caused by variation of density during solidification and cooling of molten metals. In our model, the Navier-Stokes equations along with energy equation including phase change are solved using a 2-D axisymmetric mesh.

We used the VOF method to track the free surface of droplet. A high-density-ratio lattice-Boltzmann model is employed for the computations. by the liquid crowns formed during successive droplet impact events.

free of phase change effects due to the. In this study, we performed model simulations to investigate the spatial, seasonal, and annual dew yield during 40 years (–) at ten locations reflecting the variation of climate and environmental conditions in Jordan.

In accordance with the climate zones in Jordan, the dew formation had distinguished characteristics features with respect to the yield, seasonal variation, and.

A single droplet impact onto a liquid Sessile images of water droplet during cloaking by the liquid phase of n-octadecane experimental data for the ridge height variation, due to the. As shown in Figure 1, a droplet impacts a spherical surface with a certain initial velocity, and the impact direction is parallel with the center line of droplet and moment when the droplet contacts the sphere is considered as the zero moment, t signifies the evolution time of droplet impacting process, in milliseconds.

In addition, u signifies the impact velocity, in meters per. In droplet combustion, (even in the spherically symmetric case) both molecular diffusion and bulk convection, termed Stephan flow, (produced as a result of phase changes at the droplet surface) are important phenomena.

For vigorously vaporizing droplets, the Stephan flow velocity dominates over the diffusion velocity near the droplet surface.

In probability theory, a log-normal (or lognormal) distribution is a continuous probability distribution of a random variable whose logarithm is normallyif the random variable X is log-normally distributed, then Y = ln(X) has a normal distribution.

Equivalently, if Y has a normal distribution, then the exponential function of Y, X = exp(Y), has a log-normal distribution. Droplet impact on a liquid surface is mostly controlled by the liquid droplet density (ρ), surface tension (σ), viscosity (μ), as well as droplet impact velocity (V), droplet diameter (D), and liquid film thickness (h).Droplet impact dynamics on liquid films is best explained by the Weber number (We = ρV D 2 /σ, a ratio of droplet inertia to surface tension), the Reynolds number (Re.

change in droplet size during nanoemulsion formation. propose a new model for the droplet breakup frequency for incorporation into the population balance model to capture the eﬀect of droplet viscosity, which has not been included in and density ρ d is deformed by the outer phase with.

The bubble entrapment during the recoil phase of the droplet impact is a result of air cavity closure followed by the formation of a singularity jet, which causes the bubble to oscillate at its.Phase Changes: Now that you understand the relationship between temperature, volume, and density, let's see what happens as substances go through phase changes.

As you can see in Picture #1, solids are most dense, liquids are in the middle, and gases are the least dense states for most substances.