Crown evolution kinematics of a camellia oil droplet impacting on a liquid layer

The phenomenon of droplet impact on the immiscible liquid is encountered in a variety of scenarios in nature and industrial production. Despite the exhaustive researches, it is not fully clear how the immiscibility of the droplet with impact liquid affects the crown evolution. The present work experimentally investigates the evolution kinematics of crown formed by a normal impact of camellia oil droplet on immiscible water layer. Based on discussion of dynamic impact behaviors for three critical Weber numbers (We), the radius of crown and its average spreading velocity are compared with those of previous theoretical models to discuss their applicability to the immiscible liquid. The evolution kinematics (morphology and velocity) are analyzed by considering the effects of We and layer thickness. Furthermore, the ability of crown expansion in radical and vertical directions is characterized by a velocity ratio. The results show that our experimental crown radius still follows a square-root function of evolution time, which agrees with the theoretical predictions. The dimensionless average spreading velocity decreases with We and follows a power-law, while the dimensionless average rising velocity remains constant. The velocity ratio is shown to be linearly increasing with We, demonstrating that the rising movement in crown evolution gradually enhances with We. These results are helpful for further investigation on the droplet impact on immiscible liquid layer.

Study of interface gas-liquid flow characteristics in a rectangular microchannel for wavy-annular flow

The aim of this work is an experimental study of a gas-liquid flow in a rectangular slit microchannel with a cross-section of 200 × 2045 μm. Ethanol/water (95/5) mixture and nitrogen are used as working liquid and gas, accordingly. The external T-mixer is used for obtaining of wavy-annular flow pattern. The experimental data on interfacial waves and their characteristics in the meniscus area on the short side of the microchannel are obtained using high-speed visualization for a wide range of gas and liquid superficial velocities. Images are processed using the Python libraries to define the average liquid layer thickness and maximum amplitude of waves. An increase of gas superficial velocity causes decreasing in the average liquid layer thickness and maximal amplitude of the liquid layer thickness. The waves on the liquid layer surface (maximal amplitude) can be three times larger than the average liquid layer thickness for presented liquid and gas velocities. With increasing gas superficial velocities more liquid displace from the meniscus area to the liquid film on the wide side of the microchannel.

Influence of thermal gravitational-capillary convection on temperature fields in a thin wall

The development of convective flow in a layer of ethyl alcohol when heating one of the vertical walls of a rectangular cavity was investigated experimentally. Thermal films were obtained, whose processing allowed plotting in time the distribution of temperature and temperature gradients on the free surface of the liquid layer and the opposite thin vertical wall of the cavity after the flow of heated liquid on it.