In a zero-gravity environment, single bubble migration under forced vibrations in a rotating cylindrical vessel is investigated numerically using Ansys Fluent software. In order to track the bubble-liquid interface, the volume of fluid (VOF) method is applied. Bubble dynamics are discussed only when thermocapillary force is considered, then compared to two cases where either vibration or rotation is added. The impact of the three forces together is analyzed. Different flow patterns are observed. A small change in vibration parameters (amplitude and frequency), as well as angular velocity, always leads to bubble deceleration compared to the cases where only thermocapillary force is applied. This bubble velocity reduction is accentuated for high vibration amplitudes and angular velocity. The Rossby number was also found to decrease with higher rotational velocity, greater vibration amplitude, and increased bubble diameter. In addition, the bubble size strongly influences migration time.

This study investigates the dynamics of core-annular flow (CAF) focusing on the interaction between a high-viscosity Newtonian fluid in the core region and a power-law fluid within the annular region of a horizontal pipe. Through a combination of theoretical analysis and computational fluid dynamics (CFD) simulations, the effects of varying power law index of the annular fluid on velocity profiles and pressure drop within the CAF system are explored. The theoretical models are presented for a perfect CAF arrangement without considering the interfacial waves. The simulation studies are performed using ANSYS fluent to predict the flow behavior, velocity profiles, and pressure drop in the pipe having a high viscosity Newtonian core and a power law fluid in the annular region. The simulation studies are performed for three cases of power law index of the annular fluid (<i>n<sub>a</sub></i>): shear thinning (<i>n<sub>a</sub></i> = 0.8), Newtonian (<i>n<sub>a</sub></i> = 1), and shear thickening (<i>n<sub>a</sub></i> = 1.2). The pressure variation along pipe centerline and velocity profiles of the CAF arrangement are presented. It is observed that while the shear-thickening fluid in the annular region slows down the flow of core fluid, a shear-thinning fluid in the annular region assists the core fluid and ensures its more efficient transport in the pipeline. Possible explanations of the observed behavior of pressure drop and velocity profiles are also presented.

In high-power electronic applications, hypervapotrons are commonly used for efficient heat dissipation. The present study relates to the hypervapotron application in vacuum tubes of the ion cyclotron radio frequency source used in fusion reactors. The vacuum tube's outer jacket utilizes hypervapotron (HV) fins for cooling purpose. The initial phase of indigenous vacuum tube development involves the design and development of this jacket. This research examines different types of hypervapotron fin profiles and investigates the wall temperatures of the cooling jacket using a multiphase cooling approach. The objective of the study is to safeguard the expensive vacuum tube against potential failure caused by inadequate cooling. The analysis includes five types of fin profiles: rectangular, concave, trapezoidal, U-shaped, and inverted trapezoidal. The study employs Ansys CFX software to illustrate the variation in temperature across the fins. The results indicate that the wall temperatures vary across all the distinct types of fin profiles, with the flow and heat flux values. Comparing the results with the wall temperature of the U-type profile indivcates importance of fins' shape in heat transfer. In addition, a simulation has been conducted to model the fundamental impact of wall surface roughness. The increase in surface roughness value enabled the cooling jacket to maintain the lower wall temperature at the given heat flux values.