Mixed Convective Flow of a Visco Elastic Fluid Between Two Porous Parellel Plates

A diagnostic answer for the problem of sincerely grew loose convective circulation between two vertical parallel plates has been inspected in this paper. The trademark highlights of various parameters were talked about in element. it's miles considered that to be the Grashoff huge variety declines, the profiles are more and more illustrative in nature. Likewise, due to the fact the Grashoff range reductions the charge of the liquid medium increments. it is found that, the pinnacle pace is type of organized at a median separation most of the circulate geometry. similarly, as the Grashoff amount reductions, the imply essential thrust gives off an influence of being step by step main as impact of which the liquid movements quicker within the middle locale. Likewise, it is visible that, the speed increments because the Prandtl quantity discounts. in addition, it is considered that to be the Prandtl variety expands the mass transition diminishes. The mass transition is absolutely constrained thru the parameters, for instance, Reynolds range and Prandtl amount. The flow into supporter in each the instances does no longer differs lots. All above said outcomes and delineations accommodate with the outcomes built up by manner of M. Sajid, I. Pop, T. Hayat

Reconstructing Paleofluid Circulation at the Hercynian Basement/Mesozoic Sedimentary Cover Interface in the Upper Rhine Graben

In this paper, we focus on paleocirculation at the Hercynian basement/sedimentary cover interface in the tectonic environment of the Upper Rhine graben. The goal is to increase our understanding of the behavior of the fracture-fault network and the origin of the hydrothermal fluids. We studied orientations, mineral fillings, and fluid origins of fractures that crosscut the Hercynian granitic basement and the Permo-Triassic formations in relation to the major tectonic events. Because the Mesozoic formations and the Hercynian basement on the graben flanks and inside the graben do not have the same evolution after uplift, our study includes 20 outcrops on both graben flanks and cores of the Soultz-sous-Forêts geothermal wells located inside the graben. The Hercynian granitic basement and Permo-Triassic formations were affected by several brittle phases associated with fluid circulation pulses related to graben formation during the Tertiary. We distinguished at least four stages: (1) reactivation of Hercynian structures associated with pre-rift tectonics during the early Eocene and descending meteoric waters, characterized by shearing/cataclasis textures and precipitation of illite and microquartz; (2) initiation of convective circulation of deep hot brines mixed with descending meteoric waters at the Hercynian basement/sedimentary cover interface during this first stage of Eocene rifting, characterized by dolomite and barite fillings in reactivated Hercynian fractures; (3) N-S tension fractures associated with rift tectonics just prior to uplift of the graben shoulders during Oligocene extension and descending meteoric waters, characterized by cataclastic textures and precipitation of quartz, illite, hematite, and barite; and (4) current convective circulation of deep hot brines mixed with descending meteoric waters at the Hercynian basement/sedimentary cover interface, characterized by calcite and barite fillings within the graben. This convective circulation is today present in deep geothermal wells in the western part of the Rhine graben.

A Simple Model of a Balanced Boundary Layer Coupled to a Large-Scale Convective Circulation

Many simple models of large-scale tropical circulations do not include a frictional boundary layer. A simple model is presented where the convective circulation is coupled to the boundary layer convergence. In the free troposphere, convection and boundary layer heating try to relax to a moist adiabat from the local sea surface temperature with a time scale τc, but other processes act to maintain a weak temperature gradient. There is a mass balance between radiatively driven subsidence and the large-scale convective mass flux. For a prescribed Gaussian surface temperature, the model predicts a mass flux that varies as and a convective width proportional to its reciprocal. In the boundary layer, there can be significant horizontal temperature gradients and a balance between the pressure gradient and drag is assumed. Coupling between the two layers is mediated by the vertical velocity at the top of the boundary layer. The boundary layer constrains the circulation in three ways. First, it may lengthen the relaxation time scale compared to deep convection. Second, the evaporation in the nonconvecting region constrains the horizontal moisture advection. Third, it maintains a convective boundary layer where there is a convective mass flux; this condition cannot be satisfied if τc is too small or if the drag is too large, thus showing that such values are physically impossible. These results provide testable hypotheses concerning the physics and large-scale dynamics in weather and climate models.

Design of an Innovative Solar Updraft Aeration System for Fish Ponds in the Developing World Using Thermofluidic Computational Modelling

This paper introduces an innovative design concept for a low-cost solar-thermal aeration system for fish ponds which is amenable to implementation in resource-constrained settings. In its most basic form, the system consists of a metallic solar thermal collector and a heat transfer column (referred to as conduction element in this paper), which induces convective circulation by dissipating heat to the cooler, deeper layers of the pond. As a result of the circulation, oxygen generated by phytoplankton at the top of the pond is distributed throughout the water column, preventing oxygen losses to the atmosphere due to surface supersaturation and increasing the overall dissolved oxygen (DO) content in the pond. This paper presents a design study to evaluate different system configurations. Thermofluidic numerical models were implemented to systematically analyze and compare the mass flow rate through the draft tube induced by convection. Furthermore, parametric studies were performed to evaluate the effect of the insulation patch length and the aluminum plate thickness on the overall performance of the device (i.e. the induced mass flow rate through the draft tube). It was found that the two-fin configuration with split conduction elements was superior to the central rod design in terms of performance. In addition, it was found that depending on the insulation patch length, the induced mass flow rates can be increased up to 5 times. The results from the computational models indicate that the device can induce the convective circulation in order to improve the DO content at deep levels of the ponds and has potential to improve aquaculture productivity in resource-constrained settings. The results from this study will be used to configure systems for future field evaluations that will be performed in fish ponds in Bangladesh.

Natural convection and the evolution of a reactive porous medium

We describe a mathematical model of buoyancy-driven flow and solute transport in a saturated porous medium, the porosity and permeability of which evolve through precipitation and dissolution as a mineral is lost or gained from the pore fluid. Imposing a vertically varying equilibrium solubility creates a density gradient which can drive convective circulation. We characterise the onset of convection using linear stability analysis, and explore the further development of the coupled reaction–convection system numerically. At low Rayleigh numbers, the effect of the reaction–permeability feedback is shown to be destabilising through a novel reaction–diffusion mechanism; at higher Rayleigh numbers, the precipitation and dissolution have a stabilising effect. Over longer time scales, reaction–permeability feedback triggers secondary instabilities in quasi-steady convective circulation, leading to rapid reversals in the direction of circulation. Over very long time scales, characteristic patterns of porosity emerge, including horizontal layering as well as the development of vertical chimneys of enhanced porosity. We discuss the implications of these findings for more comprehensive models of reactive convection in porous media.