Исследование процесса коалесценции капель эмульсии в неоднородном переменном электрическом поле при наличии межфазной асфальтеновой пленки на границе раздела масло-вода

The behavior of a water-in-oil emulsion stabilized with asphaltenes under the action of an inhomogeneous alternating electric field has been studied. The experimental technique is based on the use of microfluidics, optical microscopy, and high-speed video filming. Quantitative estimates of the parameters characterizing the dynamics of the destruction of the emulsion, depending on the frequency and amplitude of the applied field, are obtained. The method will be useful in the development of effective methods for breaking emulsions and modifying existing technologies for separating oil emulsions into phases.

Optical Flow Tracking Velocimetry of Near-Field Explosions

To better understand the complex dynamics and physics associated with the rapid expansion of the detonation product fireball following an explosion, it is imperative to have a full description of its associated velocity field. Typical experimental techniques rely on simple single-point measurements captured from pressure transducers or Hopkinson pressure bars. In this technical design note, we aim to improve the current state-of-the-art by introducing a means to determine full velocity fields from high-speed video using Optical Flow Tracking Velocimetry. We demonstrate the significance of this method from our results by comparing velocity fields derived from high-speed video and a validated numerical model of the same case. A wider use of this technique will allow researchers to elucidate spatial and temporal features of explosive detonations, which could not be obtained thus far using single- point measurements.

CNN-based visual analysis to study local boiling characteristics

Visual analysis allows an estimate of different local boiling characteristics including bubble growth rate, departure diameters and frequencies of nucleation, nucleation site density and evolution of bubbles and dry spots in time. At the same time, visual determination of the presented characteristics in case of big amounts of data requires the development of the appropriate software which will allow not only determination of bubble location, but also an estimate of their sizes based on high-speed video. The presented problem can be solved by using the instance segmentation approach based on a convolutional neural network. In the presented work Mask R-CNN network architecture was used for estimation of the local boiling characteristics.

Visualization in the Ranque-Hilsch vortex tube using high-speed video recording

Visualisation via video recording was carryed out in a Ranque-Hilsch vortex tube with a square cross-section. Video files were captured at recording speeds from 1000 to 10 000 frames per second. The best video files were obtained at a shooting frequency of 7600 frames per second with an input pressure of 1 bar. The video confirmed the presence of a double helix in the flow core in the second section of the tube. The video files showed the presence of a circulation zone between the flow core and the periphery, which is constantly changing over time. It can be clearly seen the angle at which the particles move in the peripheral flow.

Determination of the geometry of laser-cutting fronts with high spatial and temporal resolution

The melt flow velocity and the local surface angles of the cutting front during laser fusion cutting of 10 mm AISI 304 were determined for a laser power of 8 kW and a feed rate of 2 m/min. The cut front was recorded with a polarization goniometer, which uses the polarization of the process emission to determine the local surface angles, allowing to calculate the orientation of the normal vector of the surface. The records in this work were carried out with a frame rate of 75 kHz and a spatial resolution of about 30 µm. This allowed to identify big and small structures moving down the cutting front and to determine their velocities. The approximate velocity of the small structures was 9.1 m/s and for the big structures approx. 2.5 m/s. The information of a usual high-speed video was compared with the additionally obtained geometry information.

Investigation of the bag-breakup phenomena of the spray generation processes during wind-wave interaction in the laboratory experiments with optical methods

Present paper devoted to the investigations with optical methods processes of artificially induced bag-breakup type of spray formation phenomenon within wind-wave interaction. Experiments were carried out on the Thermostratified Wind-Wave Tank of the IAP RAS. High-speed video filming with the shadow imaging method demonstrated that it was possible to artificially reproduce all the main stages of this phenomenon, which are also observed for the sporadically occurred ones: inflation of a thin membrane surrounded by a thicker rim, rupture of the membrane leading to the formation of small droplets, fragmentation of the rim with the formation of large droplets. Special processing of the images allowed us to estimate typical lifetimes and sizes of membrane for artificial bag-breakup events which turned out to be close to the same parameters for sporadically occurred ones.

Studying of the characteristics of a single bubble under subcooled liquid boiling

An experimental study of the characteristics of single (solitary) bubbles obtained by means of focused laser heating of the surface during the boiling of two subcooled liquids with significantly different properties: water and refrigerant R113 has been carried out. To obtain the most complete detailed information, the technique of synchronized high-speed video filming of the process in two mutually perpendicular planes with a frame rate of up to 150 kHz was used. It is shown that during the boiling of a subcooled liquid, the main mechanism of heat removal from the bubble dome into the surrounding liquid is an unsteady heat conductance. Differences in the behavior of solitary vapor bubbles in the case of boiling of two liquids (water and refrigerant R113) are shown.

High-speed camera recordings uncover previously unidentified elements of zebrafish mating behaviors integral to successful fertilization

The mating behavior of teleost fish consists of a sequence of stereotyped actions. By observing mating of zebrafish under high-speed video, we analyzed and characterized a behavioral cascade leading to successful fertilization. When paired, a male zebrafish engages the female by oscillating his body in high frequency (quivering). In response, the female pauses swimming and bends her body (freezing). Subsequently, the male contorts his trunk to enfold the female’s trunk. This behavior is known as wrap around. Here, we found that wrap around behavior consists of two previously unidentified components. After both sexes contort their trunks, the male adjusts until his trunk compresses the female’s dorsal fin (hooking). After hooking, the male trunk slides away from the female’s dorsal fin, simultaneously sliding his pectoral fin across the female’s gravid belly, stimulating egg release (squeezing/spawning). Orchestrated coordination of spawning presumably increases fertilization success. Surgical removal of the female dorsal fin inhibited hooking and the transition to squeezing. In a neuromuscular mutant where males lack quivering, female freezing and subsequent courtship behaviors were absent. We thus identified traits of zebrafish mating behavior and clarified their roles in successful mating.