Satyajit Ghosh

Bio: Satyajit Ghosh is an academic researcher. The author has contributed to research in topics: Tropical cyclone. The author has an hindex of 1, co-authored 1 publications receiving 1 citations.

Countering tropical cyclonic storm impacts on low-rise houses

Abstract: PurposeThis study investigates the aerodynamics of the airflow over low-rise houses subjected to turbulent cyclonic winds along the South-eastern peninsular India, routinely afflicted by tropical cyclones. The purpose of this paper is to demonstrate how the power of modern computational fluid dynamics (CFD) and its engineering application accentuate decision-making at the planning stage of house designing in vulnerable areas.Design/methodology/approachThe Weather Research and Forecasting (WRF) model was used for first simulating the landfall of cyclone Hudhud, a real storm, and its effect in extant and new house designs. Results from the WRF model were utilized to configure further CFD simulations of airflow around house designs. The analyses yielded deep insights, often non-intuitive, into airflow patterns around these houses with disparate roof forms indicating new possibilities in redesigning houses along Indian coastal areas.FindingsThis study shows that storm-induced high TKE values warranted a fuller CFD-based study. The second major finding showed that for a 90° angle of attack, arguably the most destructive attack angle, a pitched roof (with a pitch angle of 10°) worked best – this is about half the recommended angle sourced from earlier empirical estimates dating back to the British Raj period. There is a thin layer of padded air cushion shielding the roof's vulnerable surface from the storm's most energetic parts.Originality/valueThe originality of this research lies in its discourse to systematically resolve the TKE distribution of a cyclone impacting a standalone house. In particular, the study presents a lucid demonstration of all the probable scenarios connecting cyclonic stresses with a roof response, inferred from a careful combination of results garnered from cyclonic storm modelling coupled with CFD analysis. Additionally, the paper also shows a graphic visual representation of the forces induced on different roof designs, presented as a checklist for the first time. This should serve as a ready reckoner for civic authorities involved in disaster management over cyclone-ravaged areas.

Engineered bioclimatic responses in ancient settlements: a case study

Abstract: The Mandya district of Karnataka, India, houses a unique Jain settlement constructed about 1000 years ago. Recent excavations by the Archaeological Survey of India (ASI) indicate a high degree of engineering skills among the builders of this settlement. Adapting to heat-stresses in a region where the Monsoons often failed was and is still a matter of concern. Ingenious methods were adopted to modulate bioclimatic responses to maintain thermal comfort indices. The Aretippurians used composite building fabrics which modulated heat transfer to the interiors. Indeed, the thermal transmittances for these composite fabrics were low to moderate for both the temple complexes as well as the dormitories; these were 0.27 Wm-1K-1 and 0.23 Wm-1K-1, respectively. A site visit revealed that a unique and engineered micro-climate was also made to prevail on this hilltop settlement housing several hundred Jain settlers. A granite skirted reservoir was indeed the piece-de-resistance promoting hydraulic air-conditioning for eight months of the year around the premises with copious winds blowing over a large and exposed rain-fed reservoir. This fanned chilled air across the open plan temples, courtyards, and lived-in areas. This paper explores bioclimatic responses for around 120 residents to the prevailing indoor settings modulated by an engineered microclimate. This was possible because of the staggered layout, unique building forms, use of mixed building fabric, and carefully chosen glazing ratios which yielded salubrious settings. Clearly, this entailed a complex interplay between the intercepted solar insolation, structure-driven turbulence, and the transfer of heat across the original composite walls within and around the complex, requiring a systematic experimental as well as modelling study. The experimental part of the project involved the calculation of the thermal transmittivity across the walls made up of fired bricks, granite, and limestone, and the theoretical part involved the use of appropriate software to reconstruct air flow and heat distribution across floors, walls, and ceilings to proxy the original flow pattern yielding the comfortable PMV (predicted mean vote) and PET (physiological equivalent temperature) values within these premises. This exercise may well lead to further explorations on indoor comfort adaptations in tropical settings with the use of many edifying vernacular idioms in ancient settlements which prevail even in modern layouts.