Single droplet impacts onto deposited drops. Numerical analysis and comparison

The impact of a spherical water droplet onto a stationary sessile droplet lying on a solid wall is studied numerically using the volume-of-fluid methodology. The governing Navier-Stokes equations are solved both for the gas and liquid phase coupled with an additional equation for the transport of the liquid interface. An unstructured numerical grid is used along with an adaptive local grid refinement technique, which enhances the accuracy of the numerical results along the liquid-gas interface and decreases the computational cost. The stationary sessile droplet has been created from the prior impact of one or two water droplets falling onto the solid wall, while two solid walls have been studied−an aluminum substrate and a glass substrate. The material of the wall plays an important role because it has an impact on the droplet's wetting behavior. The numerical model is validated against corresponding experimental data presented in the first part of the present work (Nikolopoulos et al., 2010), showing good agreement. Furthermore, the numerical investigation sheds light on the governing physics of the phenomenon

Single-drop empirical models for spray impact on solid walls:A review

Simplified impingement models are largely used in numerical simulation of spray impingement on solid walls, since the direct simulation of multiple drop impact is outside of the present computer capabilities. These models are usually semiempirical, based on single-drop impact experimental data and some reasonable constraints to allow extrapolation to different impact conditions. This article presents a comparison of the most commonly used drop impingement models in the present scientific literature and in commercial codes. A classification of the models and a unified scheme is proposed in terms of driving variables and outcomes. Every model is then analyzed and its peculiarities and possible weaknesses are pointed out, especially those related to the physical consistency. Finally, a comparison among the various models for a possible use in Gasoline Direct Injection (GDI) and diesel spray simulation is presented

DESIGN OF A POLYMERIC MINI-CHANNELLED SYSTEM FOR THE COOLING OF A HIGH- ENERGY PARTICLE DETECTOR AT FERMILAB

ABSTRACT BTeV is a high-energy physics experiment, which is designed to proof several aspects of the so-called Standard Model. Precise measurements will reveal if the Standard Model contains breakdowns and therefore they will hint new matters for a more fundamental theory. One of BTeV's main goals is to precisely measure CP violation in the beauty quark system. CP violation was first observed in strange quarks in 1963 and recently in beauty quarks at BaBar and Belle. CP violation causes particles and antiparticles to behave differently. The BTeV experiment was approved by FERMILAB and was currently being developed. In fact a very recent decision from the Department of Energy (February 2005) cancelled the project due to budget restrictions

Secondary atomisation produced by single drop vertical impacts onto heated surfaces

The paper reports an experimental analysis of the secondary atomisation produced by the impact of a single drop on a solid heated surface. Different wall temperatures were used to study different boiling regimes. The size of secondary drops produced by the impact was measured by two techniques, namely the phase Doppler anemometry (PDA) and the image analysis technique (IAT); this allowed to extend the measurable size range from 5.5 lm up to few mm. Two impacting walls with different surface roughness were used to show the effect of this parameter on different atomisation regimes. The liquid viscosity was also varied in a limited range by using water–glycerol mixtures. Image analysis allowed also to define the details of the morphology of drop spreading and break-up