Dynamics of an air bubble rising in constant and varying viscosity media

The dynamics of a gas bubble rising in a liquid is observed in many natural phenomena, and also in industrial applications. Due to its practical relevance, this has been studied from many centuries and it continues to be a problem of great interest even today. The main objectives of the thesis are to investigate some novel problems on bubble rising in viscosity varying systems. In several situations one could observed viscosity stratified media. Two of them are considered in this work. (a) When viscosity stratification is inherently present in the surrounding medium (say, viscosity of the outer fluid is increasing linearly with height). (b) When the outer fluid is a non-Newtonian fluid, wherein the surrounding fluid viscosity varies due to the shear caused by the motion of the bubble. Three-dimensional numerical simulations and experiments are performed to study these flows. The flow dynamics is governed by mass, momentum and energy conservation equations. A volume-of-fluid (VoF) approach is used to track the interface separating the fluids. The computational and experimental approaches used in this study are discussed in Chapter 2. The validations of the present numerical solver are also performed in the same chapter. In order to compare the bubble behaviour in a medium with varying viscosity with that observed in a constant viscosity medium (standard system), the dynamics of a rising bubble in a standard air-water system is also investigated

Computational fluid dynamics using Graphics Processing Units: Challenges and opportunities

A new paradigm for computing fluid flows is the use of Graphics Processing Units (GPU), which have recently become very powerful and convenient to use. In the past three years, we have implemented five different fluid flow algorithms on GPUs and have obtained significant speed-ups over a single CPU. Typically, it is possible to achieve a factor of 50-100 over a single CPU. In this review paper, we describe our experiences on the various algorithms developed and the speeds achieved

A Study on the Limitations for Anupana

Ayurveda has a speciality that it can cater both healthy and sick people by using same raw drugs. Anupana is a wonder tool which helps to enhance drug action, change mode of action, helps to get rid of undesired effects, enhance bio availability and makes the medicine palatable as well as target oriented. Anupana is used for both medicine as well as food. Even though there are so many advantages of proper Anupana, there are many practical difficulties while selecting Anupana in day to day practice. Various reasons like availability, palatability, difficulty in preparations are few to name. Patient comes with such difficulties in every day practice which forces a Vaidya to use anything available and comfortable to the patient. This definitely results in action of medicine as well as food. This article aims to find out such hassles and ways to overcome it

Systems level roadmap for solvent recovery and reuse in industries

Recovering waste solvent for reuse presents an excellent alternative to improving the greenness of industrial processes. Implementing solvent recovery practices in the chemical industry is necessary, given the increasing focus on sustainability to promote a circular economy. However, the systematic design of recovery processes is a daunting task due to the complexities associated with waste stream composition, techno-economic analysis, and environmental assessment. Furthermore, the challenges to satisfy the desired product specifications, particularly in pharmaceuticals and specialty chemical industries, may also deter solvent recovery and reuse practices. To this end, this review presents a systems-level approach including various methodologies that can be implemented to design and evaluate efficient solvent recovery pathways

A Multi-featured Approach by Integrating Digital Hand and Dental X-Ray for Human Age Estimation

Traditionally, human bone age is estimated manually by inspecting the multiple body part X-ray images, which is extremely time-consuming and prone to error. The accuracy of the human estimate depends on the experience of the medical practitioner, and thus it suffers from intra- and inter-observer variability. Hence, efficient automatic approaches are required to determine human age with high accuracy. In this work, we propose a human age estimation technique using Deep Learning (DL) technique based on hand X-ray images combined with dental orthopantomographs (OPGs) is proposed. Here, the input X-ray image is pre-processed first using Non-Local Means (NLM) first, followed by Region of Interest (RoI) extraction. Later, color and position image augmentation are performed in order to balance the dataset. Thereafter, the salient features in the image are determined, and based on these features, human age estimation is carried out using the Deep Residual Network (DRN). Here, the DRN is trained using the Beluga whale lion optimization (BWLO) algorithm. Furthermore, the BWLO_DRN is examined for its superiority considering the model accuracy and is found to obtain value of 90.1% on hand-wrist and 89.9% OPG real time dataset, thus showing superior performance for hand-wrist images

Dynamics of rising bubble inside a viscosity-stratified medium

The rising bubble dynamics in an unconfined quiescent viscosity-stratified medium has been numerically investigated. This is frequently encountered in industrial as well as natural phenomena. In spite of the large number of studies carried out on bubbles and drops, very few studies have examined the influence of viscosity stratification on bubble rise dynamics. To the best of our knowledge, none of them have isolated the e ff ects of viscosity-stratification alone, even though it is known to influence the dynamics extensively, which is the main objective of the present study. By conducting time-dependent simulations, we present a library of bubble shapes in the Galilei and the Eötvös numbers plane. Our results demonstrate some counter-intuitive phenom- ena for certain range of parameters due to the presence of viscosity stratification in the surrounding fluid. We found that in a linearly increasing viscosity medium, for certain values of parameters, bubble undergoes large deformation by forming an elongated skirt, while the skirt tends to physically separate the wake region from the rest of the surrounding fluid. This peculiar dynamics is attributed to the migration of less viscous fluid that is carried in the wake of the bubble as it rises, and thereby creating an increasingly larger viscosity contrast between the fluid occupied in the wake region and the surrounding fluid, unlike that observed in a constant viscosity medium. It is also observed that the e ff ect of viscosity stratification is qualitatively di ff erent for di ff erent regimes of the dimensionless parameters. In future, it will be interesting to investigate this problem in three-dimensions

Comparative study of bupivacaine alone and bupivacaine along with buprenorphine in axillary brachial plexus block: a prospective, randomized, single blind study

Background: Different additives have been used to prolong brachial plexus block. We performed a prospective, randomized single-blind study to compare Bupivacaine alone and Bupivacaine along with Buprenorphine for onset, quality, and duration of block as well as post-operative analgesia and any complication in axillary brachial- plexus block.Methods: Randomized controlled study was carried out among 60 patients of either sex, aged 20-60 years. ASA grade I or II undergoing elective hand, forearm, elbow surgery under axillary brachial plexus block. Patients were randomly divided into two groups.Group-l received 30 ml of 0.35% Bupivacaine alone in axillary block.Group-II received 30 ml of 0.35% Bupivacaine with 3µg/kg Buprenorphine in axillary block. Time taken for onset and completion of motor and sensory block as well as complete duration of block were noted in both groups. Any complication during procedure, during surgery as well as post-operatively were noted and treated.Results: Addition of Buprenorphine (3µg/kg) to Bupivacaine mixture in peripheral nerve block did not affected the onset time for motor as well as sensory block. Mean duration of motor block was 284.33±78.94 mins. in group I and in group II 307.33±60.26 mins. Mean duration of sensory block 305.066±83.64 mins. in group I while 580.166±111.45 mins. in group II. It suggests duration of sensory block was prolonged in group II then group I.Conclusions: Addition of Buprenorphine to local anesthetic drug provides good post-operative analgesia. Buprenorphine significantly prolongs sensory block and lengthens duration of analgesia without prolonging duration of motor block

Two initially spherical bubbles rising in quiescent liquid

A pair of bubbles starting from rest and rising side-by-side in a liquid have been shown earlier to display spherical and ellipsoidal shapes. In contrast to earlier computational studies on the two-dimensional dynamics of a pair of bubbles, we study the fully three-dimensional motion of the bubbles in the inertial regime. We reveal the destabilizing nature of the interaction between the wakes of the bubbles, which causes them to rise in an oscillatory path. Such three dimensionality sets in earlier in time than for a single bubble and also at a lower inertia. The interaction leads to a mirror symmetry in the trajectories of the two bubbles, which persists for some time even in the high inertia regime where each path is chaotic. The effect of the inertia and initial separation on the mirror symmetry of the path, the vortex shedding pattern and the attraction/repulsion between the bubbles are examined. The bubble rise has been interestingly observed to be symmetrical about the plane perpendicular to the separation vector for all separation distances considered in the present study

Counter-intuitive evaporation in nanofluids droplets due to stick-slip nature

We experimentally investigate the evaporation characteristics of a sessile ethanol droplet containing Al$_2$O$_3$ and Cu nanoparticles of sizes 25 nm and 75 nm on a heated substrate using shadowgraphy and infrared imaging techniques. Our results demonstrate that the droplet contact line dynamics resulting from the presence of various nanoparticles plays a dominant role in the evaporation process. This is in contrast to the widely-held assumption that the enhanced evaporation rate observed in sessile nanofluid droplets is due to the higher thermal conductivity of the added nanoparticles. We observe that even though the thermal conductivity of Al$_2$O$_3$ is an order of magnitude lower than that of Cu, droplets containing 25 nm-sized Al$_2$O$_3$ exhibit pinned contact line dynamics and evaporate much more rapidly than droplets containing Cu nanoparticles of both sizes and 75 nm Al$_2$O$_3$ nanoparticles that exhibit stick-slip behaviour. We also found that the droplets with different nanoparticles display distinct thermal patterns due to the difference in contact line behaviour, which alters the heat transfer inside the droplets. We establish this counter-intuitive observation by analysing the temporal variations of the perimeter, free surface area, and deposition patterns on the substrate.Comment: 30 pages, 7 figures, Journal-Langmui