Indian Institute of Technology Bombay

About: Indian Institute of Technology Bombay is a education organization based out in Mumbai, India. It is known for research contribution in the topics: Population & Thin film. The organization has 16756 authors who have published 33588 publications receiving 570559 citations.

Numerical simulation of flow through microchannels with designed roughness

Abstract: A three-dimensional numerical simulation of flow through serpentine microchannels with designed roughness in form of obstructions placed along the channels walls is conducted here. CFD-ACE+ is used for the numerical simulations. The effect of the roughness height (surface roughness), geometry, Reynolds number on the friction factor is investigated. It is found that the friction factor increases in a nonlinear fashion with the increase in obstruction height. The friction factor is more for rectangular and triangular obstructions and it decreases as the obstruction geometry is changed to trapezoidal. It is observed that the obstruction geometry, i.e., aspect ratio plays an important role in prediction of friction factor in rough channels. It is also found that the pressure drop decreases with the increase in the roughness pitch. Hence, the roughness pitch is an important design parameter for microchannels.

Global polarization measurement in Au+Au collisions

Abstract: The system created in noncentral relativistic nucleus-nucleus collisions possesses large orbital angular momentum. Because of spin-orbit coupling, particles produced in such a system could become globally polarized along the direction of the system angular momentum. We present the results of Lambda and (Lambda) over bar hyperon global polarization measurements in Au+Au collisions at root s(NN)=62.4 and 200 GeV performed with the STAR detector at the BNL Relativistic Heavy Ion Collider (RHIC). The observed global polarization of Lambda and (Lambda) over bar hyperons in the STAR acceptance is consistent with zero within the precision of the measurements. The obtained upper limit, |P-Lambda,P-(Lambda) over bar|<= 0.02, is compared with the theoretical values discussed recently in the literature.

Regional and seasonal variations in aerosol optical characteristics and their frequency distributions over India during 2001–2005

Abstract: [1] Regional and temporal variations in aerosol characteristics in 35 locations spread over seven different regions in India are studied during 2001-2005 from the daily mean MODIS Terra aerosol optical depth (AOD) and fine mode fraction (FMF) data. Northeast India has the lowest annual mean AOD of 0.28 while south comes next with 0.35. In the other regions AODs are higher than 0.35. Annual mean variations in AOD and FMFs in different regions do not show any noticeable increase or decrease during the 5-year period. High altitude locations are found to have lower AODs while densely populated, urban and industrialized locations have high AODs. Many locations show a winter low and summer high in AODs. Locations/regions dominated by pollution are found to have high FMF and high AODs, while regions in which natural (biogenic) aerosols are dominant had high FMF and range of AODs. The abundance of mechanically generated aerosols over a region results in low FMF and range of AODs. These features suggest that in addition to AOD variations knowledge on sources over a region are essential in understanding the FMF variations. Frequency distribution histograms of AODs and FMFs are consistent with the fact that aerosol sources exhibit seasonal and spatial variations over India. Dust activity peaks over north and west India during March-May which results in low FMFs as the aerosol distributions are influenced by large size dust aerosols. In Northeast FMFs are found to be higher than 0.8 throughout the year indicating the dominance of fine mode aerosols.