Experiments were conducted on monodisperse streams of small ( 100 m) methanol and ethanol droplets, injected perpendicularly to the axis of an axisymmetric methane diffusion flame. After crossing the methane flame, the droplets ignited and continued to burn outside of the “domain of influence” of the gaseous flame till they eventually extinguished. The extinction behavior was studied as a funct...

The shape of a weightless spinning liquid droplet is governed by the balance between the surface tension and centrifugal forces. The axisymmetric shape for slow rotation becomes unstable to a nonaxisymmetric distortion above a critical angular velocity, beyond which the droplet progresses through a series of 2-lobed shapes. Theory predicts the existence of a family of 3- and 4-lobed equilibrium...

[1] The simultaneous measurements of vertical velocity and cloud droplet size distributions in cumuli collected during the RACORO field campaign over the Atmospheric Radiation Measurement Program’s Southern Great Plains site near Lamont, Oklahoma, US, are analyzed to determine the effects of vertical velocity on droplet number concentration, relative dispersion (the ratio of standard deviation ...

In this study, we investigate computationally the low-Reynolds-number droplet motion in a square micro-channel, a problem frequently encountered in microfluidic devices, enhanced oil recovery and coating processes. The droplet deformation and motion are determined via a three-dimensional spectral boundary element method for wall-bounded flows. The effects of the flow rate, viscosity ratio and d...

We theoretically derive the amplitude equations for a self-propelled droplet driven by Marangoni flow. As advective flow driven by surface tension gradient is enhanced, the stationary state becomes unstable and the droplet starts to move. The velocity of the droplet is determined from a cubic nonlinear term in the amplitude equations. The obtained critical point and the characteristic velocity ...

In this work, we derive the asymptotic expansion of the velocity field of a small deformable droplet immersed in an incompressible Newtonian fluid. Using an appropriate physical scaling of the surface tension with respect to the droplet volume we show that the first order of the asymptotic can be expressed in terms of the velocity field in absence of the droplet and a new kind of moment tensor ...

Cryogen spray cooling (CSC) is used to protect the epidermis during dermatologic laser surgery. To date, the relative influence of the fundamental spray parameters on surface cooling remains incompletely understood. This study explores the effects of mass flow rate and average droplet velocity on the surface heat flux during CSC. It is shown that the effect of mass flow rate on the surface heat...

Analysis of droplet formation in microfluidic systems is important to understand the operation of these devices, and to permit optimal design and process control. Droplet formation in microfluidic Tjunction devices was studied using experimental and numerical methods. The simulations agree well with experimental data from PDMS devices; they show that droplet pinch-off is controlled not by visco...

Splashing is a phenomenon often observed during liquid droplet impact onto a solid surface. The threshold of splashing is known to be related to droplet size, impact velocity, and physical properties of the liquid, but the mechanisms that initiate splashing are not understood completely. In accordance with the Kelvin-Helmholtz (K-H) instability analysis, recent studies have shown that ambient g...

While the threshold of splashing when liquid droplets impact against rigid solid surfaces is known to be related to the Weber number (We), the effect of ambient gas pressure (or density) and the impact angle have not been systematically studied. In this study, we examine the effects of droplet velocity, impact angle, and ambient gas pressure (or density) on the threshold of splashing. In our me...