Unsteady RANS simulation of wind flow around a building shape obstacle

This work aims to find the origin and connection of the surface,near-wake,and far-wake structures in the flow encompassing a high-rise building for a high Reynolds number.The origin and interconnection of the stream-wise tip vortices,with the other components of the wake,is analysed in this study for the current scenario.The Unsteady Reynolds Averaged Navier-Stokes equations(URANS)together with the realizable k-εturbulence model have been used in this investigation to study the turbulent wake flow following a ground-surface-attached square shape building.A moderately big obstacle aspect ratio of 4,a Reynolds number of 12,000,and a thin evolving boundary layer thickness have been used in the flow modeling.The designed flow addresses the reversed-flows at the outlet during computation to improve the accuracy of the realizable k-e model.The Reynolds stress components are retrieved using the Boussinesq approach.The wake’s principal compositions,including span-wise-side eddies and area of high stream-wise vorticity in the uppermost portion of the wake,are illustrated by both three-dimensional(3D)representations and planner projections of the mean flow distributions.A braided vortex formation,composed of asymmetric hairpin vortexes,is witnessed in the far-wake area.The association of the near-wake vortex structures with the far-wake and near-wall flow,which is associated with the flow strengths,is also discussed.In this investigation,few areas of large stream-wise vorticity magnitude,like tip vortexes,are correlated to the 3D curving of the fluid motion,and tip vortices did not continuously reach to the free end part of the building.The 3D fluid motion interpretation,which combined several measurements of the flow distribution encompassing the cylinder,shows that the time-averaged near-wake structures are formed of two segments of distinct source and section of dominance.Furthermore,addressing reversed-flow during computation shows notable improvement in the results.

Vaccine efficacy and SARS-CoV-2 control in California and U.S.during the session 2020e2026:A modeling study

Background:Besides maintaining health precautions,vaccination has been the only prevention from SARS-CoV-2,though no clinically proved 100%effective vaccine has been developed till date.At this stage,to withhold the debris of this pandemic-experts need to know the impact of the vaccine efficacy rates,the threshold level of vaccine effectiveness and how long this pandemic may extent with vaccines that have different efficacy rates.In this article,a mathematical model study has been done on the importance of vaccination and vaccine efficiency rate during an ongoing pandemic.Methods:We simulated a five compartment mathematical model to analyze the pandemic scenario in both California,and whole U.S.We considered four vaccines,Pfizer(95%),Moderna(94%),AstraZeneca(79%),and Johnson&Johnson(72%),which are being used rigorously to control the SARS-CoV-2 pandemic,in addition with two special cases:a vaccine with 100%efficacy rate and no vaccine under use.SARS-CoV-2 related data of California,and U.S.were used in this study.Findings:Both the infection and death rates are very high in California.Our model suggests that the pandemic situation in California will be under control in the last quartile of the year 2023 if vaccination program is continued with the Pfizer vaccine.During this time,six waves may happen from the beginning of the immunization where the case fatality and recovery rates will be 1.697%and 98.30%,respectively.However,according to the considered model,this period might be extended to the mid of 2024 when vaccines with lower efficacy rates are used.On the other hand,the daily cases and deaths in the U.S.will be under control at the end of 2026 with multiple waves.Although the number of susceptible people will fall down to none in the beginning of 2027,there is less chance to stop the vaccination program if vaccinated with a vaccine other than a 100%effective vaccine or Pfizer,and at that case vaccination program must run till the mid of 2028.According to this study,the unconfirmed-infectious and infected cases will be under control at the end of 2027 and at the mid of 2028,respectively.Interpretation:The more effective a vaccine is,the less people suffer from this malign infection.Vaccines which are less than 90%effective do not have notable contribution to control the pandemic besides hard immunity.Furthermore,specific groups of people are getting prioritized initially,mass vaccination and quick responses are required to control the spread of this disease.