Somnath C. Roy

Bio: Somnath C. Roy is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Materials science & Thin film. The author has an hindex of 30, co-authored 143 publications receiving 3992 citations. Previous affiliations of Somnath C. Roy include Instituto Superior Técnico & Indian Institute of Technology Kharagpur.

Study on Flow and Turbulence Inside a Stirred Tank and Investigation on the Effects of Macroinstability on Trailing Vortex Structures

Abstract: Chemical process industries use stirred tank reactors (STR) for a variety of mixing and blending operations. Turbulent flow inside a baffled stirred tank reactor with a 45° pitched blade impeller is numerically studied using a large-eddy simulation (LES) technique with a body-fitted curvilinear mesh. The moving impeller geometries are modeled using an immersed boundary method (IBM). The instantaneous as well as time-averaged flow field suggests formation of trailing vortex due to the interaction of the fluid streams from the side and top edges of the blade. An enhanced distribution of turbulent kinetic energy has been observed in the vicinity of the trailing vortices. Instabilities occurring at a frequency lower than the frequency of impeller rotation are noticed from the time signal of the velocity components. The growth and break-up of the trailing vortices with this macro-instability frequency is observed. Turbulence is shown to be strongly anisotropic.Copyright © 2007 by ASME

A decision support algorithm to assess cost-effective control of detriments associated with a production planning system

Abstract: In systems where production of a commodity or service is accompanied by simultaneous generation of detriments, reduction of the latter usually implies increase in production cost. This leaves considerable scope for sustainable decisions regarding the extent to which control of detriments can be done in a cost effective manner. One example of such a system is production of power over an energy management scenario, where control of pollution from thermal units attracts considerable interest due to the environmental and economic implications. This paper presents an approach that decides the optimality for cost effective control of detriments accompanying a production process. The total burden on the production system is viewed in terms of two components, namely, a cost burden and a detriment burden; both considered relative to their values for the base case, which incorporates no control for detriments. The cost effective decision is obtained as an optimal tradeoff between the two burdens. The concept is formulated for the general production planning system, as well as for application to an energy management scenario. An illustrative case study adapted from the existing Indian energy scenario is used to highlight the applicability of the approach.

Immersed boundary simulation of flow through arterial junctions

Abstract: The present work demonstrates implementation of a mass-conserving sharp-interface immersed boundary for simulation of flows in branched arterial geometries. A simplistic two-dimensional arterial junction is considered to capture the preliminary flow physics in the aortic regions. Numerical solutions are benchmarked against established available experimental PIV results in Ensley et al (Annu. Thorac. Surg. 68(4):1384–1390, 1999) and numerical predictions in Gilmanov and Sotiropoulos (J. Comput. Phys. 207(2):457–492, 2005) and de Zelicourt et al (Comput. Fluids 38(9):1749–1762, 2009). Simulations are further carried out for pulsated flows and effects of blockages near the junctions (due to stenosis or atherosclerosis). Instabilities in the flow structures near the junction and the resulting changes in the downstream pulsation frequency were observed. These changes account for the physiological heart defects that arise from the poorly working valve (due to blockage), giving rise to chest pain and breathing instability, and can potentially be used as a detection tool for arterial diseases.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Nano‐photocatalytic Materials: Possibilities and Challenges

Abstract: Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.

Photocatalytic reduction of CO2 on TiO2 and other semiconductors.

Abstract: Rising atmospheric levels of carbon dioxide and the depletion of fossil fuel reserves raise serious concerns about the ensuing effects on the global climate and future energy supply. Utilizing the abundant solar energy to convert CO2 into fuels such as methane or methanol could address both problems simultaneously as well as provide a convenient means of energy storage. In this Review, current approaches for the heterogeneous photocatalytic reduction of CO2 on TiO2 and other metal oxide, oxynitride, sulfide, and phosphide semiconductors are presented. Research in this field is focused primarily on the development of novel nanostructured photocatalytic materials and on the investigation of the mechanism of the process, from light absorption through charge separation and transport to CO2 reduction pathways. The measures used to quantify the efficiency of the process are also discussed in detail.

An overview of current status of carbon dioxide capture and storage technologies

Abstract: Global warming and climate change concerns have triggered global efforts to reduce the concentration of atmospheric carbon dioxide (CO2). Carbon dioxide capture and storage (CCS) is considered a crucial strategy for meeting CO2 emission reduction targets. In this paper, various aspects of CCS are reviewed and discussed including the state of the art technologies for CO2 capture, separation, transport, storage, leakage, monitoring, and life cycle analysis. The selection of specific CO2 capture technology heavily depends on the type of CO2 generating plant and fuel used. Among those CO2 separation processes, absorption is the most mature and commonly adopted due to its higher efficiency and lower cost. Pipeline is considered to be the most viable solution for large volume of CO2 transport. Among those geological formations for CO2 storage, enhanced oil recovery is mature and has been practiced for many years but its economical viability for anthropogenic sources needs to be demonstrated. There are growing interests in CO2 storage in saline aquifers due to their enormous potential storage capacity and several projects are in the pipeline for demonstration of its viability. There are multiple hurdles to CCS deployment including the absence of a clear business case for CCS investment and the absence of robust economic incentives to support the additional high capital and operating costs of the whole CCS process.