Open Enclosure Research Articles

Effect of Prandtl Number on Forced Convection in a Two Sided Open Enclosure Using Nanofluid

Analysis of Prandtl number effect on forced convective flow and thermal field characteristics inside an open cavity with porous wavy isothermal wall using water-CuO nanofluid have been performed numerically. The upper and lower surfaces are of temperature Th. The fluid enters from left and exits from right with initial velocity Ui and temperature Ti. Governing equations are discretized using the Finite Element Method. Simulation is carried out for a range of Prandtl number, Pr (from 1.47 to 8.81) and wave amplitude A (from 0 to 0.15) while Reynolds number, Re =100; Darcy number, Da = 100 and solid volume fraction, = 5%. Results are presented in the form of streamlines, isothermal lines, rate of heat transfer, average temperature of the fluid and velocity at mid-height of the channel for various Pr and A. Increasing Pr and lessening A causes the enhancement of heat transfer rate.© 2013 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v5i1.9641 J. Sci. Res. 5 (1), 67-75 (2013)

Effect of a magnetic field on natural convection in an open cavity subjugated to water/alumina nanofluid using Lattice Boltzmann method

In this paper, the effect of a magnetic field on natural convection in an open enclosure which subjugated to water/alumina nanofluid using Lattice Boltzmann method has been investigated. The cavity is filled with water and nanoparticles of Al2O3 at the presence of a magnetic field. Calculations were performed for Rayleigh numbers (Ra=104–106), volume fractions of nanoparticles (φ=0,0.02,0.04 and .0.06) and Hartmann number (0≤Ha≤90) with interval 30 while the magnetic field is considered horizontally. Results show that the heat transfer decreases by the increment of Hartmann number for various Rayleigh numbers and volume fractions. The magnetic field augments the effect of nanoparticles at Rayleigh number of Ra=106 regularly. Just as the most effect of nanoparticles for Ra=104 is observed at Ha=30, so the most influence of nanoparticles occurs at Ha=60 for Ra=105.

PRIMARY FEATHER FOLLICLE ABLATION IN COMMON PINTAILS (ANAS ACUTA ACUTA) AND A WHITE-FACED WHISTLING DUCK (DENDROCYGNA VIDUATA)

Eight 1-yr-old common pintails (Anas acuta acuta) and one 2-yr-old white-faced whistling duck (Dendrocygna viduata) were presented for the persistence of primary flight feathers 1 yr after pinioning. The birds were housed outdoors in an open enclosure necessitating flight prevention. The birds were placed under general anesthesia, and a diode laser was used to ablate the primary feather follicles of the previously pinioned wing. Swelling was the most common side effect seen in seven out of nine treated birds. Other side effects included ulceration, hyperemia, edema, and serosanguinous discharge. All side effects were resolved by 12 wk postprocedure. Laser feather follicle ablation was successful in 28 of 40 (70%) of the treated common pintail feathers, and flight was not observed 7 mo following the procedure in any of these birds. Feather follicle ablation was successful in two of six (33%) of the treated white-faced whistling duck feathers, and the bird in question was observed flying 5 mo after the procedure. Primary feather follicle ablation with a diode laser was a successful method of flight prevention in common pintails but was not effective for a white-faced whistling duck.

A Neolithic and Bronze Age Monument Complex and its Early Medieval Reuse: Excavations at Netherfield Farm, South Petherton, Somerset, 2006

An early Neolithic causewayed enclosure, a middle Neolithic long enclosure and an earlier Bronze Age open enclosure were among a group of prehistoric features discovered and examined by excavation at Netherfield Farm, South Petherton during archaeological mitigation work ahead of the construction of a natural gas pipeline between Ilchester and Barrington, Somerset, in 2006. Of particular interest were burnt deposits within the long enclosure ditches and a possible Bronze Age field system. Assemblages of pottery and flintwork contribute to the understanding of these features and a programme of radiocarbon dating has amplified the chronology of activity on the site. Evidence from a group of burnt and unburnt pits and a partial enclosure reveal the reuse of the site between the fifth and eighth centuries AD.

Lattice Boltzmann simulation of natural convection in an open enclosure subjugated to water/copper nanofluid

In this paper Lattice Boltzmann simulation of natural convection in an open enclosure which subjugated to water/copper nanofluid has been investigated. Calculations were performed for Rayleigh numbers (Ra = 10 4–10 6), volume fractions of nanoparticles ( 0 ≤ φ ≤ 0.05 ) and open enclosure aspect ratios ( 0.5 ≤ A ≤ 2 ). The comparisons show that the average Nusselt number increases with augmentation of Rayleigh number and the volume fraction of nanoparticles for whole ranges of aspect ratios. The average Nusselt number decreases as the aspect ratio increases at various Rayleigh numbers and different the nanoparticle volume fractions. But generally the most effect of nanoparticles on heat transfer enhancement is observed at the aspect ratio of A = 2. Also nanoparticles influence the heat transfer less at Ra = 10 5 among studied Rayleigh numbers.

Trapping of sound in an open rectangular cavity.

The trapping of sound in a rectangular enclosure, such as a corridor or street, and the noise disturbance caused by trapping, can be a serious problem to understanding speech or other acoustic events. In contrast to confined systems that sustain so‐called trapped modes, the behavior in a partially open enclosure is associated with leaky modes of the system that are “nearly” trapped but are still radiating some energy out of the system. This paper presents numerical modeling that has been developed to calculate the sound that can be nearly trapped in an open rectangular cavity such as the rectangular cross‐section of a street canyon that is excited by a number of sources switching on and off. The cavity is surrounded by an elastic half space, i.e., surrounded on three sides by absorbing walls, for which it is necessary to implement a set of numerical grids that are staggered in space and in time. Results are shown for combinations of different walls and different shaped geometries that minimize the radiation losses out of the cavity. The results are used to comment on the problems that can be caused by the trapping of sound in acoustic systems.

Magnetohydrodynamic mixed convection in a horizontal channel with an open cavity

The development of magnetic field effect on mixed convective flow in a horizontal channel with a bottom heated open enclosure has been numerically studied. The enclosure considered has rectangular horizontal lower surface and vertical side surfaces. The lower surface is at a uniform temperature T h while other sides of the cavity along with the channel walls are adiabatic. The governing two-dimensional flow equations have been solved by using Galarkin weighted residual finite element technique. The investigations are conducted for different values of Rayleigh number ( Ra), Reynolds number ( Re) and Hartmann number ( Ha). Various characteristics such as streamlines, isotherms and heat transfer rate in terms of the average Nusselt number ( Nu), the Drag force ( D) and average bulk temperature ( θ av ) are presented. The results indicate that the mentioned parameters strongly affect the flow phenomenon and temperature field inside the cavity whereas in the channel these effects are less significant.

Buoyancy- and Thermocapillary-Induced Convection of Cold Water in an Open Enclosure with Variable Fluid Properties

The aim of the present study is to investigate the buoyancy- and thermocapillary-induced convection of water near its density maximum in an enclosure with temperature-dependent properties. The viscosity and thermal conductivity of the water are varied with reference temperature. The governing equations are solved by the finite-volume method. The results are discussed for various values of reference temperature parameter, density inversion parameter, and Rayleigh and Marangoni numbers. It is observed that the temperature of maximum density leaves strong effects on flow and heat transfer due to the formation of bi-cellular structure and reduction of the average heat transfer. It is also observed that convection heat transfer is enhanced by thermocapillary force when buoyancy force is weaken.

Experimental study of Inclination angle and Surface Area Effects For Longitudinally Finned Cylinder on Free Convection Heat Transfer in an open Enclosure

Experimental study of Inclination angle and Surface Area Effects For Longitudinally Finned Cylinder on Free Convection Heat Transfer in an open Enclosure

Measurements of density profile evolution during the stably-stratified filling of an open enclosure

The stably-stratified filling of an open enclosure produces an interfacial gradient layer which is transported through the enclosure with the bulk flow. The evolution of this interfacial layer is strongly time-dependent and is driven by the nature of the interaction between the internal gravity waves and the inlet-driven interfacial shear. Measurements of density profile evolution have been completed for a rectangular enclosure with a single corner inlet and density variation produced by saline concentration. This system serves as a mass transfer analog to large-scale, thermally-stratified energy storage devices, preserving dynamic similitude in a laboratory-scale system. The experiments covered jet Reynolds numbers of 200–2200 and Froude numbers of 0.06–0.6 in an enclosure with a width 23 times the jet inlet height. The density profiles are seen to be strongly asymmetric and exhibit growth rates significantly different than due to simple one-dimensional molecular diffusion. In addition, shadowgraph and hydrogen bubble visualizations of the density and velocity fields in the gradient layer show the persistence of complex multi-dimensional flow structure even at relatively late stages of the filling process when the gradient layer has been transported well away from the enclosure inlet. The evolution of the vertical density profile has been compared quantitatively to a quasi one-dimensional model based upon empirical diffusivity coefficients.

Natural Convection: Analysis of Partially Open Enclosures With an Internal Heated Source

A numerical study of the thermal and fluid dynamic behavior of air in partially open two-dimensional enclosures is presented. An analysis is made based on two aspects of the radius, H/W = 1 and 2. The left and right walls are maintained at different constant temperatures, while the upper and bottom walls are thermally insulated. The enclosure has an opening on the right wall and a small heating source located on the bottom or left vertical wall, occupying three different positions. Numerical simulations were performed for several values of Rayleigh number (Ra e ) in the range between 103 and 106>, while the intensity of the two effects—the difference in temperature of the vertical walls and the internal heating source (Ra i )—was evaluated based on the relation R = Ra i /Ra e , in the range between 0 and 2,500. Representative results illustrating the effects of relation R on the streamlines and isotherms within the enclosures are reported. In addition, simulation results for the local and average Nusselt numbers on the heated and colded walls of the enclosures are presented and discussed for different values of the parameters R, Ra e , W H , and H/W. It is founded that the parameter modifications have significant effects on the average and local Nusselt numbers of the enclosures.

Transition from gravity- to inertia-dominated behavior computed for the turbulent stably-stratified filling of an open enclosure

This paper treats the unsteady mixed convection processes occurring during the stably-stratified bottom filling of an open enclosure with application to stratified thermal storage devices. Central to the performance of these devices is the extent of thermal mixing which occurs at the interface between the hot and cold fluid volumes as one or the other is displaced from the vessel. Useful volume fraction, a parameter reflecting the temperature limited usefulness of the stored fluid, and internal entropy generation are used to characterize the extent of thermodynamic losses in time and their variation with flow rates ranging from well-stratified to highly-mixed conditions. The transition to highly-mixed behavior is critically important since it limits the achievable energy discharge rates. Distinct trends in the variation of cumulative performance with Reynolds number indicate this transition occurs at Froude numbers of approximately one and lead to identification of a gravity-dominated and an inertia-dominated regime. In the gravity-dominated regime, the useful volume fraction increases linearly with time after an initial adjustment period and the turbulent diffusivity affects the variation of entropy generation only at the edges of the relatively distinct thermocline. Within the thermocline, the turbulent kinetic energy is completely damped by gravity. However, in the inertia-dominated or highly-mixed regime, the useful volume fraction starts to drop in the later stages of the filling process and appreciable entropy generation levels are distributed across a relatively wide thermocline with turbulent diffusivity playing a significant role throughout.

Characterization of obesity in Japanese monkeys (Macaca fuscata) in a pedigreed colony

Japanese monkey, Macaca fuscata, is recognized as the monkey species inhabiting the northernmost area in the world, and thus likely to possess unique fat-depositing mechanisms to resist cold weather in winter. We report that obese females are present in the Wakasa group of Japanese monkey reared in an open enclosure of the Primate Research Institute, Kyoto University. Eight of 12 females were categorized as obese, showing percentage body fat of over 22%. The levels of serum leptin (mean +/- SD, 4.9 +/- 2.3 ng/ml) measured in these obese monkeys were significantly higher than those of non-obese peers of the same group (n = 4; 1.2 +/- 0.5 ng/ml) and another Japanese monkey group (Takahama, n = 14; 0.8 +/- 0.25 ng/ml); however, serum levels of adiponectin, insulin, glucose, hemoglobin A1c, and fructosamine did not differ between obese and non-obese monkeys. Few serum lipid parameters such as triglyceride and cholesterol showed lower levels in obese monkeys than their non-obese peers. These results show that these obese monkeys in the Wakasa group have not developed obesity-related diseases/disorders such as diabetes. In the Wakasa group, the frequency of obese individuals was high in some maternal lineages, suggesting that genetic factors responsible for obesity may have been inherited in these lineages.

A Numerical Study of Natural Convection in Partially Open Enclosures With a Conducting Side-Wall

A numerical study of natural convection generated by a cold vertical wall of an enclosure with two openings on the opposite wall of finite thickness is presented. The enclosure is connected to an infinite reservoir filled with hot air. A two-dimensional laminar flow is assumed both within the enclosure and along the side of the bounding wall immersed into the reservoir. The effects of the size of the openings, spacing between the vertical walls and thermal resistance of the bounding wall are investigated. Numerical results are discussed for aspect ratios of the enclosure and Rayleigh numbers relevant to practical applications.

Integral Solutions for Transient Temperature Profiles in Stably-Stratified Open Enclosures

The stably-stratified filling of an enclosure produces an interfacial layer, or thermocline, separating the hot and cold fluid volumes which is transported through the vessel with the bulk flow. The evolution of this interfacial layer is characterized by profile asymmetries and growth rates not explained by simple molecular diffusion. The present paper presents integral solutions to the horizontally-averaged energy equation with variable diffusivities exhibiting these same characteristics. The formulation requires only two parameters in addition to those of the uniform diffusivity case. The solutions are compared to published data to illustrate determination of the empirical constants and show that key characteristics of the model, specifically a constant fill-line temperature and symmetric growth rates, are satisfied for a range of moderate flow rates. At higher flow rates, the layers are seen to exhibit an increasingly higher degree of growth rate asymmetry.

Management of heat stroke in a Sloth Bear Melursus ursinus

A male Sloth Bear aged about 10 years was let loose in his open enclosure as usual in the early morning hours of 16.v.2001. The Bear was quite normal till earlier that day with normal appetite and stools. After the cleaning operations, the usual diet (wheat flour cooked in milk) was offered in the feeding cubicle but the Bear did not come to the feeding cubicle and stayed in the open enclosure. At around 1730 hrs the zoo keeper reported that the Bear was sleeping in sternal recumbency and was not responding to his calls. Observations from outside the enclosure revealed that his breathing was shallow and fast and was panting. The Bear was pulled towards the bars of the enclosure with the help of a rope truss tied around the abdomen, and with a wooden pole. He tried to resist the operation and attempted to get up but could not. The rectal temperature revealed hyperthermia (105.40 F and rapid pulse (85/min), but the tone was feeble. The respiration rate was also high (55/min) and the he appeared very dull.

Numerical analysis of free convective flows in partially open enclosure

Laminar steady state buoyancy induced flows in a two-dimensional, air filled partial open enclosure with a discrete flush mounted iso-flux heat source on one of its walls is investigated numerically. The transport equations for energy and vorticity are solved with the aid of the ADI finite difference scheme on uniform mesh. Because of the specific application of the present study in the air cooling of electronic equipments, results are obtained only for a Prandtl number of 0.71 with an aspect ratio of 1.0 for a range of Rayleigh numbers, Ra (≤105), heat flux parameter, Q and opening parameter, A 0 using constant properties and Boussinesq approximation by imposing approximate conditions at the opening. Results of flow and temperature patterns, velocity and temperature profiles shows that the outgoing flow is governed by strong characteristics of the cavity condition whereas the incoming flow influenced by outside conditions. It is observed that Rayleigh number considerably affects the flow and thermal fields within the open enclosure when compared with intensity of heat flux and size of the opening.

Open Field or Enclosure? Peasants, Planters’ Agents and Lawyers in Jamaica, 1866–1875

AbstractThe fencing of boundaries so as to confine or exclude cattle was a major preoccupation in the most densely populated parishes of Jamaica in the mid nineteenth century. Part-time labourers (who constituted a new semi-peasantry) were being settled on the fringes of the old estates in increasing numbers, having been granted licenses or pretended leases for land on which they grew their crops. The same ‘attorneys’ who managed the older declining plantations where such squatting was arranged also tended to be introducing cattle in place of sugar and they wished to shift the costs of fencing onto their small ‘peasant’ occupiers. However, English law, which imposed an obligation to fence in cattle, initially assisted the peasantry. The attorneys therefore looked to New World models that would require those growing crops to fence out animals. This article examines actions in court and the agitation in more detail so as to suggest that fencing was a major source of inter-racial friction in the period before and after the Morant Bay rebellion, but with the outcome strongly favouring a late-century resurgence in the plantation economy.

Speech intelligibility in highway toll booths

The purpose of this study is to improve the working conditions at highway toll collection facilities. It is believed that the sustained noise levels create an unpleasant working condition and hamper communication between attendants and patrons. Controlling noise in this environment is particularly challenging because the toll booth is a partially open enclosure with reflecting walls which may amplify the traffic noise. Toll collection employees were surveyed in order to assess, among other factors, the influence of ambient traffic noise on speech intelligibility. The results suggest that communication problems exist and that active noise control (ANC) headsets are a potential solution. Low-frequency vehicular noises are believed to strongly contribute to the communication problem, and ANC systems are particularly effective at reducing such noise emissions. To adapt ANC headsets to this application, insertion loss measurements have been made for a variety of active headsets. Attention was given to the level of attenuation within the frequency range of speech intelligibility. Modifications are underway to optimize an active headset for speech intelligibility and noise reduction. Additional work includes modeling the acoustics of the environment with a ray-tracing software package. This modeling work will allow structural changes to be evaluated.

Application of the transfer configuration factors in radiation heat transfer

A new engineering method is presented for the analysis of radiation exchange within an open enclosure filled with an isothermal radiation gas. It is shown that the general class can be formulated of an open enclosure composed of black, diffusive-grey or spectral quantity. A number of new relations are derived between temperature, heat flux and effective radiation energy flux of surfaces. The method of determination of transfer configuration factors and dissipation losses is also presented. Whereas in previously-published methods, errors were possible if an equilibrium state were assumed, the current approach does not have this drawback, but enables the radiation gas temperature to be explicitly predicted. A special emphasis is put on the problems of radiation in enclosures composed of adiabatic surfaces which affect the measurement technique of surface emissivity. Calorimetric emission measurements of thermal radiation properties of opaque surfaces are also presented.