Numerical Simulation of Solid and Porous Fins’ Impact on Heat Transfer Performance in a Differentially Heated Chamber

The development of different industrial fields, including mechanical and power engineering and electronics, demands the augmentation of heat transfer in engineering devices. Such enhancement can be achieved by adding extended heat transfer surfaces to the heated walls or heat-generating elements. This investigation is devoted to the numerical analysis of natural convective energy transport in a differentially heated chamber with isothermal vertical walls and a fin system mounted on the heated wall. The developed in-house computational code has been comprehensively validated. The Forchheimer–Brinkman extended Darcy model has been employed for the numerical simulation of transport phenomena in a porous material. The partial differential equations written, employing non-primitive variables, have been worked out by the finite difference technique. Analysis has been performed for solid and porous fins with various fin materials, amounts and heights. It has been revealed that porous fins provide a very good technique for the intensification of energy removal from heated surfaces.

Impact of ohmic heating on energy transport in double diffusive Oldroyd-B nanofluid flow induced by stretchable cylindrical surface

The most important and significant research topic in mechanical and industrial engineering is the fluid flow with heat transport by a stretched surface because of the numerous applications. The impact of heat transport on product quality can be noticed in the field of chemical engineering, polymer processing, glass fiber production, hot rolling, metal extrusion, production of paper, and drawing of plastic films and wires. In light of such foregoing applications, an attempt is made to model the thermal and solutal diffusion phenomena in Oldroyd-B nanofluid flow over a stretching cylinder by using Buongiorno's model and Cattaneo-Cristov theory. To explore the heat flow mechanism in the flow, the effects of heat source/sink with ohmic heating are also considered. Additionally, the influence of chemical reactions is used to investigate the solutal transport process in nanofluid flow. The mathematical formulation section of the manuscript depicts the mathematical modeling of momentum, heat, and mass diffusion equations. The effect of dimensionless physical constraints on the flow, temperature, and concentration distributions of Oldroyd-B nanofluid flow are investigated using the homotopy analysis method (HAM) in Wolfram Mathematica. In the results and discussion section, graphical findings are displayed and physically justified. A section of concluding remarks is added at the end of the text to emphasize the study's major findings.

Observation of ballistic upstream modes at fractional quantum Hall edges of graphene

The presence of “upstream” modes, moving against the direction of charge current flow in the fractional quantum Hall (FQH) phases, is critical for the emergence of renormalized modes with exotic quantum statistics. Detection of excess noise at the edge is a smoking gun for the presence of upstream modes. Here, we report noise measurements at the edges of FQH states realized in dual graphite-gated bilayer graphene devices. A noiseless dc current is injected at one of the edge contacts, and the noise generated at contacts at length, L = 4 μm and 10 μm away along the upstream direction is studied. For integer and particle-like FQH states, no detectable noise is measured. By contrast, for “hole-conjugate” FQH states, we detect a strong noise proportional to the injected current, unambiguously proving the existence of upstream modes. The noise magnitude remains independent of length, which matches our theoretical analysis demonstrating the ballistic nature of upstream energy transport, quite distinct from the diffusive propagation reported earlier in GaAs-based systems.

Meridional energy transport extremes and the general circulation of NH mid-latitudes: dominant weather regimes and preferred zonal wavenumbers

The extratropical meridional energy transport in the atmosphere is fundamentally intermittent in nature, having extremes large enough to affect the net seasonal transport. Here, we investigate how these extreme transports are associated with the dynamics of the atmosphere at multiple scales, from planetary to synoptic. We use ERA5 reanalysis data to perform a wavenumber decomposition of meridional energy transport in the Northern Hemisphere mid-latitudes during winter and summer. We then relate extreme transport events to atmospheric circulation anomalies and dominant weather regimes, identified by clustering 500 hPa geopotential height fields. In general, planetary-scale waves determine the strength and meridional position of the synoptic-scale baroclinic activity with their phase and amplitude, but important differences emerge between seasons. During winter, large wavenumbers (k = 2 − 3) are key drivers of the meridional energy transport extremes, and planetary and synoptic-scale transport extremes virtually never co-occur. In summer, extremes are associated with higher wavenumbers (k = 4 − 6), identified as synoptic-scale motions. We link these waves and the transport extremes to recent results on exceptionally strong and persistent co-occurring summertime heat waves across the Northern Hemisphere mid-latitudes. We show that these events are typical, in terms of dominant regime patterns associated with extremely strong meridional energy transports.

Smart Culture and Heritage, the “Rare” Category of SSC Classifications

ISO and ITU propose some classifications regarding the smart sustainable cities services: energy, transport, health, tourism, education, safety, environment, governance, commerce, buildings, community. Culture and heritage is a rare category in these classifications, despite the fact they have to be always been included in an SSC ecosystem. They could play a key role in achieving the 17 SDGs due to some critical reasons: their deep roots in humanity, their wide spread across city life and environment, hence their horizontal connections with all the other SSC categories. There are many options of SSC structures, which have the potential to be dedicated on culture and heritage. QR codes, GIS., VR, apps, IoT, virtual events are some of them, widely implemented by cities. Via these ways, culture and heritage could 1) contribute to the humans' welfare index and 2) interact with the other sectors of the city ecosystem. Their added value to the sustainability process creates the necessity to be a distinctive category in international SSC classifications.

Mathematical model and experimental validation for the prediction of dissolved oxygen saturation in aquaculture ponds

Fluid mechanics is one of the oldest areas of physics with the greatest number of applications in everyday life. This area became more versatile when mass and energy transport equations were incorporated. Together, these equations allow describing a wide variety of case studies with great precision. Among cases available in the open literature, aquaculture is one of the most important due to the growing need for food sources for human consumption, the nutritional value of many fish varieties, the low cost of the maintenance of fish farms. Dissolved oxygen is one of the most relevant parameters ensuring water quality in fish farming. Many fish farms use permanent artificial aeration systems for maintaining the oxygen level within the recommended range used, causing an increasing energy consumption. Therefore, this work proposes an equation and validation, based on equations hydraulics and transport phenomenon, capable of determining the maximum concentration of dissolved oxygen in the body from the operating parameters of the tilapia rearing pond.

Parametric Decay of Alfvénic Wave Packets in Nonperiodic Low-beta Plasmas

The parametric decay of finite-size Alfvén waves in nonperiodic low-beta plasmas is investigated using one-dimensional (1D) hybrid simulations. Compared with the usual small periodic system, a wave packet in a large system under the absorption boundary condition shows different decay dynamics, including reduced energy transfer, localized density cavitation, and ion heating. The resulting Alfvén wave dynamics are influenced by several factors relating to this instability, including the growth rate, central wave frequency, and unstable bandwidth. A final steady state of the wave packet may be achieved when the instability does not have enough time to develop within the residual packet, and the packet size shows well-defined scaling dependencies on the growth rate, wave amplitude, and plasma beta. Under the proper conditions, enhanced secondary decay can also be excited in the form of a narrow, amplified wave packet. These results may help to interpret laboratory and spacecraft observations of Alfvén waves, and to refine our understanding of the associated energy transport and ion heating.