Multiphase flows appear in many industrial as well as natural phenomena, for instance carbon sequestration, steel-making, fuel combustion, food processing, rainfall, hail formation and lava flows. Any process involving melting, evaporation, solidification or involving two or more phases comes under this topic. Some of the less understood problems which are active areas of research in the field of multiphase flows are: moving contact lines, phase change, breakup and coalescence of jets and drops and flow of multiple non-Newtonian fluids.
Many of the above-mentioned processes are frequently influenced by temperature and concentration gradients. The presence of these gradients at the interface separating the fluids leads to interfacial tension gradients, which in turn induce tangential stresses, commonly known as Marangoni stresses. This phenomenon also plays a vital role in many technological applications, such as single crystal growth of silicon and turbine blades. However, it is very challenging to obtain the detailed flow features both numerically and experimentally. Therefore, one of the focus areas of the group is to obtain accurate numerical models of flows driven by temperature and concentration gradients.
Sonoprocess Engineering :
The application of ultrasound (also known as ‘sonochemistry’) in various research fields has attracted the scientists during the past decade. The ultrasound wave is a longitudinal wave comprising of alternate compression/rarefaction cycles inducing high velocity oscillatory motion of the fluid elements, commonly known as micro-streaming. Ultrasound irradiation basically increases/accelerates the chemical reactivity by a million fold. The principle behind this is the transient cavitation. Cavitation is nothing but the formation, growth, and implosive collapse of bubbles in a liquid, which causes generation of high local temperature and pressures (~5000K and 1000 atm) with a substantial heating and cooling rate of more than 109 K/s. The phenomenon of acoustic cavitation is observed only in liquid medium under high intensity ultrasonic irradiation. The two major components of transient cavitation are known as physical effect (i.e. micro-turbulence, acoustic or shock waves) and chemical effect (i.e. generation of reactive species like ●H, ●O, ●OH, HO2● etc.). Generally, the chemical effects of cavitation occur in homogeneous liquid phase and heterogeneous liquid-liquid or solid-liquid interfaces. Our research group works on the fundamental aspects of ultrasonics and sonochemistry focusing on understanding of physical and chemical effects of ultrasound and cavitation.
Renewable and Sustainable Energy :
The depletion of fossil fuels and the apparent pollution issues due to emission of greenhouse gases significantly impact the climate change. In order to avoid such situation, many countries around the world have already adopted the production of biofuels (such as biodiesel, bio-hydrogen etc.) as an alternative energy source to fossil fuels and oil. The use of biodiesel can reduce 57% of greenhouse gases compared to petroleum diesel (EPA, USA). Utilization of waste and oil (edible or non-edible) is the most promising and economical policy for production of biofuels. This not only gives an alternative resource for sustainable energy but also protects the environment by reducing greenhouse gases.
Water Treatment :
Water is the most precious natural resource on the planet. However, a very small fraction (~1%) of water is available for human consumption. With the shortage of water worldwide due to growing population, the treatment of water for producing sustainable and reliable source of water is thus among the major challenges of the 21st century. Our research group mainly focuses on the wastewater treatment and water reuse to meet the requirements for growing population and the process industries. To address these problems, we apply a wide range of expertise including chemical and biological techniques.