流体力学: オープンアクセス

Passive ventilation of buildings at night forms an essential part of a low-energy cooling strategy, enabling excess heat that has accumulated during the day to self-purge and be replaced with cooler night air. Instrumental to the success of a purge are the locations and areas of ventilation openings, and openings positioned at low and at high levels are a standard choice as there's then the expectation that a buoyancy-driven displacement flow will establish and persist. Desirable for his or her efficiency, displacement flows guide excess heat out through high-level openings and cooler air in through low-level openings. Herein we show that displacement flow can't be maintained for the complete duration of a purge. Instead, the flow must transition to an ‘unbalanced exchange flow’, whereby the cool inflow of air at low level is maintained but there's now a warm outflow and a cool inflow occurring simultaneously at the high-level opening. The internal redistribution of heat caused by this exchange alters the rate at which heat is self-purged and the time thought necessary to complete a purge. We develop a theoretical model that captures and predicts these behaviours. Our approach is distinct from all others which assume that a displacement flow will persist throughout the purge. Based on this enhanced understanding, and specifically that the transition to unbalanced exchange flow changes the rate of cooling and resultant emptying times, we anticipate that practitioners will be better placed to design passive systems that meet their target specifications for cooling.

Nanocrystalline materials like Sn doped In₂O₃ Indium Tin Oxide (ITO) were prepared by this Combustion technique and characterized. Presence of electronic centres in Nanocrystalline ITO is observed from Raman studies and therefore the same has been confirmed by photoluminescence studies. The oxidation properties of ITO were studied by X-ray Diffract meter grain sizes are confirmed by structural studies. As against the expectation of oxide on individual Nano grains of In-Sn alloy, ITO Nano grains grew into faceted Nano grains on heat treatment in air and O₂ atmosphere. The expansion of ITO under O₂ atmosphere showed pentagon symmetry. This Nanocrystalline ITO has been studied using Electron paramagnetic resonance (EPR) measurements. Structural studies by X-ray diffraction (XRD) showed the presence of dominant β phase with a minor quantity of α phase. In EPR, isotopic chemical shift peaks were observed and that they are assigned to originate from the α, β phases of ITO and grain boundary component respectively. From this study, different atomic arrangements were identified in grain boundaries compared to an equivalent within the grain in Nanocrystalline ITO.

In the low-Reynolds-number range below Re = 60,000, SD7003 and Ishii airfoils are referred to as high-performance low-Reynolds-number airfoils with a comparatively high lift-to-drag ratios. Although the aerodynamic characteristics at particular Reynolds numbers are thoroughly studied, research is lacking on how Reynolds numbers affect the aerodynamic characteristics that become pronounced for general low-Reynolds-number airfoils. This study investigates the Reynolds number dependence on the aerodynamic performance of those two airfoils. The results demonstrate that the Ishii airfoil is especially less hooked in to the Reynolds number of the lift curve compared to the SD7003 airfoil. Although there's a small difference within the high angles of attack above the utmost lift coefficient, the lift slope hardly changes, even when the Reynolds number varies.

A wind tunnel experiment was administered to characterize the flow surrounding rectangular prisms of varying permeability, each set mounted on a stationary plane-bed surface and subsequently on an erodible bed. Laser-Doppler anemometer measurements of the horizontal and vertical velocity components were obtained during a grid that included a neighbourhood adjacent to the windward face, enveloped the free end of the shape, and extended ≈6.5 element heights downwind of the rear wall. From these component measurements, the entire velocity (Tuw), turbulence intensity (TI), Reynold Stress (RS) and therefore the turbulence K.E. (TKE) were calculated throughout the sampling array. As compared to an impermeable same-sized cube, the near-surface TKE and RS were substantially reduced within the wake flow behind the permeable elements. Within the plane-bed experiments, TI generally increased downwind of the permeable cubes, opposite to the trend for the impermeable form. The excellence in TI was less pronounced, however, when the bed morphology developed scour marks. The impermeable cube had the most important amount of abrasion relative to its volume, in response to strong downwash along its windward face and therefore the development of an active horseshoe vortex. This coherent flow structure wasn't detected for all permeable forms and therefore the amount of scour was orders of magnitude less. This study would suggest that for restricting erosion, the efficiency of a surface-mounted element are often improved by making the walls of the shape permeable instead of solid, thereby increasing energy dissipation within the wake flow while reducing vortex impingement and bed shear stress. The study of the flow around surface-mounted, sharp-edged obstacles placed in a channel is fundamental to the understanding of the flow mechanisms for complex two- and three dimensional geometries. There exists a considerable amount of published data for flows over two-dimensional geometries such as ribs and fences. However, there are markedly fewer studies in the literature concerned with the flow around three dimensional obstacles. Of these, most are limited to the study of a single parameter, for example, the reattachment length. It is therefore the aim of this study to provide a general description of the flow around three-dimensional obstacles. Based on the flow visualization experiments performed for obstacles of different aspect ratio (width-to-height), the changes in the flow patterns as a function of aspect ratio are discussed qualitatively. Additionally, large-scale parameters such as the reattachment and separation lengths are discussed quantitatively. The flow around single, surface-mounted, prismatic obstacles submerged in a boundary layer at high Reynolds numbers depends on a large number of parameters.

Separation Techniques Webinar: It is our great pleasure to invite you to participate in the 9th Edition of International Conference and Exhibition on Separation Techniques which is an Online Webinarwhich will take place during 25-26 May 2020. The dedicated webinar theme is: An Insight into the Research Applications of Various Separation Techniques. The purpose of the webinar is to bring together Chemists, Chemistry Professionals and many experts to discuss the complex interactions of Separation Techniques. This meeting will enable exchange of ideas and knowledge between different disciplines for facilitating research and Lab researching collaborations focusing on Separation Techniques. Let’s join hands for the future of this world, for the Next-gen of mankind, for the prospective and collective efforts to change what is within our reach and means. The 2 days conference, held during May 25th to May 26th provides the leading academic scientists, researchers and scholars to share their experiences and research results about all aspects of Various Separation Techniques.