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Outbreak of a Tornado with Tropical Cyclone Yaas (2021) Formed over the Bay of Bengal
Nasreen Akter,M. Rafiuddin1 한국기상학회 2023 Asia-Pacific Journal of Atmospheric Sciences Vol.59 No.1
A tornado outbreak occurred in West Bengal (WB), India, about 15–16 h before the landfall of Cyclone Yaas formed in May 2021 over the Bay of Bengal. High-resolution analysis data have been used to investigate the possible tornadoes in terms of environmental conditions connecting to the cyclone. The WB tornado is found as intense as EF2–3 on the tornado scale and is likely associated with a mini-supercell. The total shear of 37 m s− 1 from 0–6 km above ground level (AGL) with strong clockwise rotation, the moderate instability (1504 J kg− 1) and the energy helicity index of 2.2 are the substantial convective parameters related to the WB tornado. Moreover, the favorable environment owning intense bulk shear, a larger value of storm-relative environmental helicity in the lowest 1 km AGL and high values of significant tornado parameter (STP) urge the potentiality of multiple tornadoes spawning in multi-days accompanying the landfalling Cyclone Yaas. The right-front quadrant of the cyclone is found to be more vulnerable for developing moderate to severe tornadoes within its rainbands. The positive potential vorticity anomalies evidence the cloud-scale cyclonic circulation from surface to 400 hPa with the maximum in the mid-level.
Exploiting the orbital motion of water particles for energy extraction from waves
M. Rafiuddin Ahmed,Mohammed Faizal,Krishnil Prasad,김창구,이영호 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.4
In wave motion, the water particles are known to follow orbital paths. This orbital motion was used to drive five-bladed Savonius rotors. Experiments were performed on an array of four rotors placed in a two-dimensional (2-D) wave channel. The flow around the rotors was documented using particle image velocimetry measurements. The submergence of the rotors and the distance between them were varied, and the rotational speeds of the rotors (Nn) were recorded at different wave frequencies. It was found that rotational speeds increased with an increase in the wave frequency, as it amplified the wave height that increased the kinetic energy of the particles in their orbital motion. The rotational speeds decreased when the distance between the rotors increased. High rotational speeds are recorded when the array of the rotors is placed close to the water surface at the smallest centre-to-centre distance between the rotors.