Cavity Dynamics and Splashing Mechanism in Droplets

Inhaltsverzeichnis

1. Frontmatter

2. Chapter 1. Introduction

   Zhaohao Li, Xiaoyu Wang, Junwei Shen, Yuning Zhang

   Abstract

   This chapter introduces the cavitation atomization technology, which shows that it is a promising technology that can improve atomization efficiency. Furthermore, the research status of the cavitation collapse dynamics and the droplet splash dynamics contained in this technology is reviewed. The related literatures can help to explore the theoretical basis for the future development direction of the cavitation atomization technology. Finally, this chapter demonstrates the research structure of the book.

3. Chapter 2. Research Methods

   Zhaohao Li, Xiaoyu Wang, Junwei Shen, Yuning Zhang

   Abstract

   This chapter focuses on the research methods of dynamics of interactions between cavitation bubbles and droplets, including high-speed photographic experiments, theoretical analysis of bubble dynamics, and numerical simulation of OpenFOAM. From the experimental aspect, according to the droplet morphology produced in different modes, the droplets can be divided into hemispherical, ellipsoidal, and spherical droplets. The difference in the droplet morphology affects the analysis of dynamic behavior characteristics. From the theoretical view, based on the classical Rayleigh–Plesset equation, the dynamic equations of the cavitation bubble inside a droplet are developed considering the influence of surface tension and the viscous force. For the simulation, the governing equations are introduced together with the volume of fluid (VOF) and the large-eddy simulation (LES) methods.

4. Chapter 3. Dynamics of Cavitation Bubbles in a Droplet

   Zhaohao Li, Xiaoyu Wang, Junwei Shen, Yuning Zhang

   Abstract

   This chapter investigates the dynamic behaviors of the cavitation bubble in a droplet, including nucleation, jet and radial oscillations. On the one hand, a high-speed photography is employed to observe the dynamic behaviors together with the main influencing factors.

5. Chapter 4. Dynamics of Droplet Splashing Induced by Cavitation Bubble Collapse

   Zhaohao Li, Xiaoyu Wang, Junwei Shen, Yuning Zhang

   Abstract

   This chapter focuses on the dynamic characteristics of the droplet splashing induced by the collapse of the cavitation bubble. Firstly, the effect of the relative position of the cavitation bubble on the splashing behavior of a droplet is observed by the high-speed camera. Secondly, the flow field distribution near the gas–liquid interface is analyzed, including pressure field, velocity field, baroclinity, and vortex distribution. Finally, the critical stability criterion of the interface is further discussed, and the influencing mechanism of cavitation bubble collapse on the droplet splashing behavior is revealed together with the instantaneous droplet surface breaking.

6. Chapter 5. Dynamic Characteristics of a Vapor Bubble in a Droplet

   Zhaohao Li, Xiaoyu Wang, Junwei Shen, Yuning Zhang

   Abstract

   This chapter focuses on the comparisons of dynamic behaviors of droplets containing the air and the vapor. The fundamental reason for this difference lies in the existences of vapor condensation. Due to the phase transition, the velocity of fluid propagation and the mechanism of its interactions with shock waves may be changed. Based on this, it is of certain significance to investigate the dynamic characteristics of a vapor bubble inside a droplet. In this chapter, a numerical method is adopted to simulate the movement, deformation, collapse, and other processes of a vapor bubble, and a quantitative analysis is carried out on the local instantaneous pressure released during the collapse.

7. Chapter 6. Cavitation Dynamics Under the Influence of Diesel Droplet

   Zhaohao Li, Xiaoyu Wang, Junwei Shen, Yuning Zhang

   Abstract

   The viscosity, density, surface tension, and other physical properties of droplets have a great influence on the dynamic behaviors of cavitation bubbles. Taking diesel droplet as the research object, this chapter focuses on the mechanism of inertial force, viscous force, surface tension, aerodynamic force, and other forces during the growth and the collapse of cavitation bubble through numerical simulations.

8. Chapter 7. Conclusion

   Zhaohao Li, Xiaoyu Wang, Junwei Shen, Yuning Zhang

   Abstract

   In this book, experimental, theoretical, and numerical research methods are introduced to explore the interaction mechanisms between cavitation bubbles and droplets. The cavitation bubble dynamic characteristics under the influence of droplets and the droplet splashing characteristics induced by cavitation bubbles are discussed in detail. Through the comprehensive research of this book, the following main conclusions can be drawn.

9. Backmatter