Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Selected Basic Flows and Forces
- Part I Collision of Liquid Jets and Drops with a Dry Solid Wall
- Part II Drop Impacts onto Liquid Surfaces
- Part III Spray Formation and Impact onto Surfaces
- 7 Drop and Spray Diagnostics
- 8 Atomization and Spray Formation
- 9 Spray Impact
- Part IV Collisions of Solid Bodies with Liquid
- Part V Solid–Solid Collisions
- Index
- References
9 - Spray Impact
from Part III - Spray Formation and Impact onto Surfaces
Published online by Cambridge University Press: 13 July 2017
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Selected Basic Flows and Forces
- Part I Collision of Liquid Jets and Drops with a Dry Solid Wall
- Part II Drop Impacts onto Liquid Surfaces
- Part III Spray Formation and Impact onto Surfaces
- 7 Drop and Spray Diagnostics
- 8 Atomization and Spray Formation
- 9 Spray Impact
- Part IV Collisions of Solid Bodies with Liquid
- Part V Solid–Solid Collisions
- Index
- References
Summary
The impact of sprays onto walls is of great industrial importance and for this reason has attracted the attention of researchers in an effort to predict the outcome. While some applications expressly avoid splashing, e.g. coating or spray painting, many result in a secondary spray. In fact, spray impact may even be used to intentionally change the size distribution of droplets in a spray, such as with inhalation nebulizers or in direct injection fuel systems. While Chapters 4, 5 and 6 dealt with the impact of single drops onto surfaces or liquid layers, the present chapter addresses the impact of sprays onto such surfaces. Fundamentally, similar questions are asked: how many secondary droplets of what size and velocity are generated and what part of the impacting liquid remains on the surface? If heat transfer is involved then interest lies with the heat flux density at the surface or the effective Nusselt number, which, as with single drops, will depend strongly on the temperature of the surface; hence on which regime of the Nukiyama curve describing heat transfer at the surface is applicable (Nukiyama 1934, Kutateladze 1963, Carey 1992). This chapter encompasses spray impact onto liquid films (Section 9.1), discusses the secondary spray formation in Section 9.2 and outlines useful empirical correlations in Section 9.3
Two main approaches are commonly used to predict the outcome of a spray impact with a rigid wall or with a wall covered by a liquid film. The first approach is formulated in the framework of an Euler/Lagrange numerical simulation and describes the spray as the superposition of a large number of isolated, non-interacting drops (Cossali et al. 2005). Numerous models for single drop impact have been proposed (Bai and Gosman 1995, Stanton and Rutland 1996, Mundo et al. 1998, Lee and Bergman 2002), all having empirical origins. Roisman et al. (1999), Moreira et al. (2010) and Park and Watkins (1996) have provided overviews of many existing models and presented also direct comparisons of their predictive capabilities. It is a characteristic of all models that they provide reliable predictions at most over the narrow range of impact parameters from which they were derived. Indeed, several models in use for spray impact are even based on the impact of single drops onto a dry surface, which may be completely inappropriate.
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- Information
- Collision Phenomena in Liquids and Solids , pp. 412 - 470Publisher: Cambridge University PressPrint publication year: 2017