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1
Xu, Gang, and Aiqun Li. "Research on the mechanical characteristics and calculation method of concrete cavity shear wall." Advances in Structural Engineering 21, no. 12 (February 15, 2018): 1840–52. http://dx.doi.org/10.1177/1369433218757761.
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A series of non-linear analyses is presented in this article investigating the differences in mechanical characteristics of the common concrete shear wall, the concrete shear wall with concealed vertical slits, and the concrete cavity shear wall under monotonic loading. The numerical analyses define monotonic capacity curves and ductility. The results indicate that reasonable matching can be achieved in stiffness, capacity, and ductility, and non-linear behavior can be improved in cavity shear wall by changing the parameters of the cavity. A theoretical model of cavity shear wall structure is proposed to estimate the lateral displacement curve and the equivalent lateral stiffness. The effectiveness of the theoretical formula was validated by the results from numerical models with different parameters. The influence of cavity parameters on equivalent lateral stiffness is discussed, and the effect of different parameters is investigated. The results indicate that equivalent lateral stiffness of the shear wall can be reduced by increasing the length or the thickness of the cavity; the cavity’s effect on squat shear walls is significantly larger than that on slender walls.
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Goyal, Ajay, M. Shokry Rashwan, M. A. Hatzinikolas, and S. Zervos. "Structural performance of cavity walls constructed with units containing sawdust and shear connected to the brick veneer." Canadian Journal of Civil Engineering 21, no. 4 (August 1, 1994): 576–84. http://dx.doi.org/10.1139/l94-059.
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A series of experiments were conducted to investigate the behaviour of walls constructed using newly developed masonry sawdust blocks. Full-scale cavity walls consisting of the new masonry block backup and burnt clay brick veneer, connected together using metal connectors, were tested under lateral loads. The effects of block unit size, height of wall, reinforcement, grout, and cavity width on the behaviour of the wall were studied. The test results showed behaviour similar to that of walls constructed with lightweight concrete masonry units. A summary of the results is presented in this paper. Key words: masonry, cavity wall, shear connector, lateral loading, stiffness, veneer, sawdust block.
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Azzouz, El Amin, and Samir Houat. "Asymmetrical Flow Driving in Two-Sided Lid-Driven Square Cavity with Antiparallel Wall Motion." MATEC Web of Conferences 330 (2020): 01009. http://dx.doi.org/10.1051/matecconf/202033001009.
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The two-dimensional flow in a two-sided lid-driven cavity is often handled numerically for the same imposed wall velocities (symmetrical driving) either for parallel or antiparallel wall motion. However, in this study, we present a finite volume method (FVM) based on the second scheme of accuracy to numerically explore the steady two-dimensional flow in a two-sided lid-driven square cavity for antiparallel wall motion with different imposed wall velocities (asymmetrical driving). The top and the bottom walls of the cavity slide in opposite directions simultaneously at different velocities related to various imposed velocity ratios, λ = -2, -6, and -10, while the two remaining vertical walls are stationary. The results show that varying the velocity ratio and consequently the Reynolds ratios have a significant effect on the flow structures and fluid properties inside the cavity.
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Zubkov, Pavel T., and Eduard I. Narygin. "The effect of viscous dissipation on natural convection in a square cavity." Tyumen State University Herald. Physical and Mathematical Modeling. Oil, Gas, Energy 5, no. 3 (October 14, 2019): 118–30. http://dx.doi.org/10.21684/2411-7978-2019-5-3-118-130.
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This article studies the natural convection of a viscous, incompressible fluid in a square cavity in a gravitational field. The temperature of vertical walls is constant. The temperature of the left wall is higher than temperature of the right wall; the horizontal walls are considered thermally insulated. The initial condition for the temperature of a fluid in a square caviry is the constant and equals the temperature of the right wall. The initial condition for the velocity is zero. We consider only those cases where the obtained flow in the cavity is laminar. All thermophysical characteristics are assumed constant, except for one when the motion equation accounts for the gravity. Mathematical model is the Boussinesq approximation but the equation of conservation of energy contains Rayleigh dissipation function.<br> In this article, the authors have researched the effect of viscous dissipation on natural convection heat transfer in square field. The results show that viscous dissipation significantly affects the heat transfer through the cavity. This problem was solved with the finite volume method by algorithm SIMPLER for Pr=1, Gr=10<sup>4</sup>, and 10<sup>−5</sup>≤Ec≤10<sup>−3</sup>.
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Calle, Klaas, Charlotte Coupillie, Arnold Janssens, and Nathan Van Den Bossche. "Implementation of rainwater infiltration measurements in hygrothermal modelling of non-insulated brick cavity walls." Journal of Building Physics 43, no. 6 (October 31, 2019): 477–502. http://dx.doi.org/10.1177/1744259119883909.
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The watertightness of solid masonry walls is generally based on the concept of buffering and afterwards drying out the absorbed rainwater. In cavity walls, on the contrary, the air layer provides a capillary break between the inner and outer leafs allowing drainage of rainwater and preventing infiltration to the interior wall surface. For assessing moisture-related risks, heat, air and moisture models have proven to be a valuable tool, but in the case of cavity walls two problems arise: the degree of water infiltration into the cavity is unknown, and no consensus is available on the method that should be used to implement these infiltrations in a simulation. For example, for the existing buildings, it is worthwhile to investigate whether injecting cavity wall insulation induces an increase or decrease in moisture-related pathologies, in contrast to adopting a fixed performance criterion for assessment. However, to complete a thorough analysis of a brick cavity wall, it is first useful to review the hygrothermal behaviour of cavity walls as it has been previously described in the literature. As such, this article provides a summary of experimental water infiltration results for cavity walls as described in the literature, discusses experimental results of four test walls subjected to four test protocols and extracts from these results the water infiltration rate for implementation in heat, air and moisture models. Finally, several methods for implementing the infiltrations in heat, air and moisture simulations are presented and evaluated based on different damage criteria. In general, the new modelling approaches are considered to provide realistic results. Nonetheless, an in situ investigation on whether mortar bridges occur in the cavity due to poor workmanship remains crucial to understanding the hygrothermal response as mortar bridges are found to have a dominant impact on the risk of mould growth at the interior wall surface.
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Harvey, Steven A. "Open-cavity and closed-cavity (intact canal wall) tympanomastoidectomy." Operative Techniques in Otolaryngology-Head and Neck Surgery 7, no. 1 (March 1996): 50–54. http://dx.doi.org/10.1016/s1043-1810(96)80062-5.
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Smith, Peter G., Malcolm H. Stroud, and Joel A. Goebel. "Soft-Wall Reconstruction of the Posterior External Ear Canal Wall." Otolaryngology–Head and Neck Surgery 94, no. 3 (March 1986): 355–59. http://dx.doi.org/10.1177/019459988609400317.
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A simple method of reconstructing a previously removed posterior ear canal with an autogenous, bilaminar membrane is described. The resulting air-filled mastoid cavity is an anatomic extension of the middle ear cleft and is separated from the ear canal by a functional barrier that is continuous with the tympanic membrane. The acoustic characteristics of an associated tympanoplasty are not significantly altered, and many of the problems that are associated with an exteriorized cavity are avoided. In contradistinction to other methods of mastoid obliteration or reconstruction, the semitransparent nature of the soft canal wall allows inspection of the underlying cavity for residual or recurrent disease. The technique can be used to repair either a newly created cavity or a previous radical (or modified radical) mastoidectomy defect. The functional results of thirty ears reconstructed in this fashion are detailed. A variable amount of soft-wall retraction was noted postoperatively in 47% of the ears; however, the long-term functional results in these cases remain satisfactory.
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Chakroun, Walid. "Effect of Boundary Wall Conditions on Heat Transfer for Fully Opened Tilted Cavity." Journal of Heat Transfer 126, no. 6 (December 1, 2004): 915–23. http://dx.doi.org/10.1115/1.1798931.
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An experimental investigation was performed to study the effect of wall conditions as well as the tilt angle on heat transfer for fully opened tilted cavity. The cavity has a rectangular shape with a square cross section. One side is fully opened to the ambient, permitting air to flow inside the cavity by virtue of buoyancy. The cavity was selected to be long enough to simulate two-dimensional natural convection. Seven cases with different wall configurations were examined: (a) three of which with only one wall heated and the other two were insulated, (b) three of which with two walls heated and the other one was insulated, and (c) a case with all walls were heated. The heated walls were maintained at constant heat flux, which correspond to a constant Grashof number of 1.3×108. In each case, the cavity was rotated over a range of ±90 deg (measured from the vertical direction) in 15 deg increments. It was concluded that tilt angle, wall configuration, and the number of heated walls are all factors that strongly affect the convective heat transfer coefficient between the cavity and the ambient air. Empirical correlations were provided to predict the average Nusselt number at different inclination angles for all seven cases. It was found that the correlations could predict the result to within 4 to 10 percent, depending on the inclination angle and the case considered.
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Pey, Yin Yin, and Leok Poh Chua. "Effects of trailing wall modifications on cavity wall pressure." Experimental Thermal and Fluid Science 57 (September 2014): 250–60. http://dx.doi.org/10.1016/j.expthermflusci.2014.05.005.
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Ahmed Kadhim Hussein, Muhaiman Alawi Mahdi, and Obai Younis. "Numerical Simulation of Entropy Generation of Conjugate Heat Transfer in A Porous Cavity with Finite Walls and Localized Heat Source." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 84, no. 2 (July 25, 2021): 116–51. http://dx.doi.org/10.37934/arfmts.84.2.116151.
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In this research, the entropy production of the conjugate heat transfer in a tilted porous cavity in respect to heat source and solid walls locations has been studied numerically. Three different cases of the cavity with finite walls thickness and heat source locations are considered in the present study. For both cases one and two, the cavity considered has a vertical finite walls thickness, while the cavity with the horizontal finite walls thickness is considered for case three. For cases one and two, the left sidewall of the cavity is exposed to heat source, whereas the rest of this wall as well as the right sidewall are adiabatic. The upper and lower cavity walls are adiabatic. For case three, the lower wall is exposed to a localized heat source, while the rest of it is assumed adiabatic. The upper wall is cold, whereas the left and right sidewalls are adiabatic. The flow and thermal fields properties along with the entropy production are computed for the modified Rayleigh number (150 ? Ram ? 1000), thermal conductivity ratio (1 ? Kr ? 10), heat source length (0.2 ? B ? 0.6), aspect ratio (0.5 ? AR ? 2) and walls thickness (0.1 ? D1 ? 0.2 and 0.1 ? D2 ? 0.2) respectively. The results show that, the maximum values of the entropy generated from fluid friction develop close to the cavity wall-fluid interfacial, while the maximum values of the entropy generated from heat transfer develop nearby the heat source region. The average Bejan number (Beav) is higher than (0.5) for cases one and two. While for case three, it was found to be less than (0.5). Also, the results show that as the modified Rayleigh number, thermal conductivity ratio, heat source length and aspect ratio increased, the fluid flow intensity in the cavity increased. While, it decreased when the walls thickness increased. From the results, it is concluded that case three gives a higher heat transfer enhancement. The obtained results are compared against another published results and a good agreement is found between them.
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KANNO, Shu, and Nobuo TANAKA. "3C16 Acoustic power mode control theory of a double-wall cavity." Proceedings of the Symposium on the Motion and Vibration Control 2010 (2010): _3C16–1_—_3C16–10_. http://dx.doi.org/10.1299/jsmemovic.2010._3c16-1_.
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K., Venkatadri, Gouse Mohiddin S., and Suryanarayana Reddy M. "Hydromagneto quadratic natural convection on a lid driven square cavity with isothermal and non-isothermal bottom wall." Engineering Computations 34, no. 8 (November 6, 2017): 2463–78. http://dx.doi.org/10.1108/ec-06-2017-0204.
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Purpose This paper aims to focus on linear and non-linear convection in a lid-driven square cavity with isothermal and non-isothermal bottom surface. Design/methodology/approach It is assumed that the top moving wall is adiabatic and the bottom wall is heated in two modes, and the rest of the walls are maintained at uniform cold temperature. The coupled governing non-linear partial differential equations are solved numerically with MAC algorithm for conducting a parametric study with uniform and non-uniform temperature bottom wall. Findings The numerical results are depicted in the form of streamlines, temperature contours and variation of local Nusselt number. The local Nusselt number at the bottom wall of the cavity increases in presence of non-linear temperature parameter as compared with linear temperature parameter and heat transfer reduces with increasing of Ha for uniform and non-uniform heating of bottom wall. Research limitations/implications The numerical investigation is conducted for unsteady, two-dimensional natural convective flow in a square cavity. An extension of the present study with the effect of inclination of cavity, wavy walls and triangular cavity will be the interest of future work. Originality/value This work studies the effect of magnetic field in the presence of linear convection and non-linear convection. This study might be useful to cooling of electronic components, alloy casting, crystal growth and fusion reactors, etc.
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Sankar, M., S. Kiran, G. K. Ramesh, and Oluwole Daniel Makinde. "Natural Convection in a Non-Uniformly Heated Vertical Annular Cavity." Defect and Diffusion Forum 377 (September 2017): 189–99. http://dx.doi.org/10.4028/www.scientific.net/ddf.377.189.
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Natural convection from the linearly heated inner and/or outer walls of a vertical annular cavity has been numerically investigated. The bottom wall is uniformly heated and top cylindrical wall is thermally insulated. In this analysis, we considered two different thermal boundary conditions, namely case (I) and case (II) to understand the effect of non-uniform heating of inner and/or outer walls on the convective flow and subsequently the local and global heat transfer rate. For case (I), the inner and outer walls are heated linearly, while the linearly heated inner wall and cooled outer wall is considered in case (II). An implicit finite difference scheme is applied to solve the model equations of the problem. The numerical simulations in terms of streamlines and isotherms, local and global Nusselt numbers are presented to illustrate the effects of Rayleigh number and non-uniform thermal boundary conditions for a fixed Prandtl number of Pr = 0.7.
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Alsabery, Ammar I., Habibis Saleh, Mohammad Ghalambaz, Ali J. Chamkha, and Ishak Hashim. "Fluid-structure interaction analysis of transient convection heat transfer in a cavity containing inner solid cylinder and flexible right wall." International Journal of Numerical Methods for Heat & Fluid Flow 29, no. 10 (October 7, 2019): 3756–80. http://dx.doi.org/10.1108/hff-10-2018-0593.
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Purpose This paper aims to investigate the fluid structure interaction analysis of conjugate natural convection in a square containing internal solid cylinder and flexible right wall. Design/methodology/approach The right wall of the cavity is flexible, which can be deformed due to the interaction with the natural convection flow in the cavity. The top and bottom walls of the cavity are insulated while the right wall is cold and the left wall is partially heated. The governing equations for heat, flow and elastic wall, as well as the grid deformation are written in Arbitrary Lagrangian–Eulerian formulation. The governing equations along with their boundary conditions are solved using the finite element method. Findings The results of the present study show that the presence of the solid cylinder strongly affects the transient solution at the initial times. The natural convection flow changes the shape of the flexible right wall of the cavity into S shape wall due to the interaction of the flow and the structure. It is found that the increase of the flexibility of the right wall increases the average Nusselt number of the hot wall up to 2 per cent. Originality/value To the best of the authors' knowledge, the unsteady natural convection in an enclosure having a flexible wall and inner solid cylinder has never been reported before.
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Prasad, V., and A. Chui. "Natural Convection in a Cylindrical Porous Enclosure With Internal Heat Generation." Journal of Heat Transfer 111, no. 4 (November 1, 1989): 916–25. http://dx.doi.org/10.1115/1.3250806.
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A numerical study is performed on natural convection inside a cylindrical enclosure filled with a volumetrically heated, saturated porous medium for the case when the vertical wall is isothermal and the horizontal walls are either adiabatic or isothermally cooled. When the horizontal walls are insulated, the flow in the cavity is unicellular and the temperature field in upper layers is highly stratified. However, if the top wall is cooled, there may exist a multicellular flow and an unstable thermal stratification in the upper region of the cylinder. Under the influence of weak convection, the maximum temperature in the cavity can be considerably higher than that predicted for pure conduction. The local heat flux on the bounding walls is generally a strong function of the Rayleigh number, the aspect ratio, and the wall boundary conditions. The heat removal on the cold upper surface decreases with the aspect ratio, thereby increasing the Nusselt number on the vertical wall. The effect of Rayleigh number is, however, not straightforward. Several correlations are presented for the maximum cavity temperature and the overall Nusselt number.
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Liu, Yi, Zhi Guo Dou, and Li Wei Duan. "Numerical Investigation of Cavity Flow Field Characteristics in Supersonic Flow." Applied Mechanics and Materials 789-790 (September 2015): 368–72. http://dx.doi.org/10.4028/www.scientific.net/amm.789-790.368.
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The cold flow field in a two dimensional cavity of supersonic combustor has been simulated numerically by using the compressible flow Navier-Stokes equation with theκ-ωSST turbulence model. The flow field structure of different cavity aft wall slope angle (16°,30° and 90°) , different fore aft wall height ratio (1 and 2) and different length depth ratio (3 and 5) are analyzed. The conclusions are as follows: As cavity aft wall slope angle decreases, the compression wave formed at cavity leading separation corner shifts into expansion wave, the shear layer moves into cavity gradually; As cavity fore aft wall height ratio increases from one to two, the expansion wave formed at cavity leading separation corner strengthens and there is no compression wave formed at;As cavity length depth ratio increases from three to five, the compression or expansion wave formed at cavity leading separation corner weakens, cavity bottom wall pressure tends to be constant and aft wall pressure rises.
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Van Den Bossche, Nathan, Willem Huyghe, Jan Moens, Arnold Janssens, and Michel Depaepe. "Airtightness of the window–wall interface in cavity brick walls." Energy and Buildings 45 (February 2012): 32–42. http://dx.doi.org/10.1016/j.enbuild.2011.10.022.
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Bissinger, George. "Wall compliance and violin cavity modes." Journal of the Acoustical Society of America 113, no. 3 (March 2003): 1718–23. http://dx.doi.org/10.1121/1.1538199.
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Denisov, G. G., and I. M. Orlova. "Scattering in a corrugated-wall cavity." Radiophysics and Quantum Electronics 31, no. 6 (June 1988): 512–16. http://dx.doi.org/10.1007/bf01044655.
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Aradag, Selin, Kubra Asena Gelisli, and Elcin Ceren Yaldir. "Effects of Active and Passive Control Techniques on Mach 1.5 Cavity Flow Dynamics." International Journal of Aerospace Engineering 2017 (2017): 1–24. http://dx.doi.org/10.1155/2017/8253264.
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Supersonic flow over cavities has been of interest since 1960s because cavities represent the bomb bays of aircraft. The flow is transient, turbulent, and complicated. Pressure fluctuations inside the cavity can impede successful weapon release. The objective of this study is to use active and passive control methods on supersonic cavity flow numerically to decrease or eliminate pressure oscillations. Jet blowing at several locations on the front and aft walls of the cavity configuration is used as an active control method. Several techniques are used for passive control including using a cover plate to separate the flow dynamics inside and outside of the cavity, trailing edge wall modifications, such as inclination of the trailing edge, and providing curvature to the trailing edge wall. The results of active and passive control techniques are compared with the baseline case in terms of pressure fluctuations, sound pressure levels at the leading edge, trailing edge walls, and cavity floor and in terms of formation of the flow structures and the results are presented. It is observed from the results that modification of the trailing edge wall is the most effective of the control methods tested leading to up to 40 dB reductions in cavity tones.
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Zhang, Yannian, and Moncef L. Nehdi. "Experimental Study on Cast-In-Situ Masonry Cavity Walls Subjected to In-Plane Cyclic Loading." Infrastructures 5, no. 1 (January 15, 2020): 8. http://dx.doi.org/10.3390/infrastructures5010008.
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This study investigates the behavior of cast-in-situ masonry cavity walls subjected to in-plane quasi-static loading. Thirteen cast-in-situ masonry cavity walls and one solid wall were tested under combined axial and quasi-static lateral loads. Test parameters included the tie shape, tie layout, thickness of the insulating layer, and the level of axial compression. The problems related to shear capacity and failure mechanisms of cast-in-situ masonry cavity walls were analyzed. Experimental results indicate that failure of most wall specimens occurred via crushing at corners, accompanied by flexural and diagonal cracks in the inner leaves. The shape and layout of the ties had a limited effect on the shear strength of cast-in-situ masonry cavity walls, while axial compression had a positive influence on shear strength. The relative displacement between the inner and outer leaves was nearly zero before walls cracked and reached less than 2 mm at the ultimate load. The shape and layout of the ties had a slight influence on the coordination of inner and outer leaves, while the insulating layer thickness and axial compression had a negative effect. Hysteretic loops under quasi-static loading were spindle-like, and wall specimens exhibited large nonlinear deformation capacity, indicating adequate aseismic capability. A new formula for calculating the shear capacity of the cast-in-situ cavity masonry walls was proposed and was demonstrated to be accurate.
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Ishak, Muhamad Safwan, Ammar I. Alsabery, A. Chamkha, and Ishak Hashim. "Effect of finite wall thickness on entropy generation and natural convection in a nanofluid-filled partially heated square cavity." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 3 (November 16, 2019): 1518–46. http://dx.doi.org/10.1108/hff-06-2019-0505.
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Purpose The purpose of this paper is to study the effects of finite wall thickness on the natural convection and entropy generation in a square cavity filled with Al2O3–water nanofluid in the presence of bottom heat source. Design/methodology/approach The moving isothermal heater was placed on the bottom solid wall. The vertical walls (left and right walls) were fully maintained at low temperatures. The rest of the bottom solid wall along with the top horizontal wall was kept adiabatic. The boundaries of the domain are assumed to be impermeable; the fluid within the cavity is a water-based nanofluid having Al2O3 nanoparticles. The Boussinesq approximation is applicable. The dimensionless governing equations subject to the selected boundary conditions are solved using the finite difference method. The current proposed numerical method is proven excellent through comparisons with the existing experimental and numerical published studies. Findings Numerical results were demonstrated graphically in several forms including streamlines, isotherms and local entropy generation, as well as the local and average Nusselt numbers. The results reveal that the thermal conductivity and thickness of the solid wall are important control parameters for optimization of heat transfer and Bejan number within the partially heated square cavity. Originality/value According to the past research studies mentioned above and to the best of the authors’ knowledge, the gap regarding the problem with entropy generation analysis and natural convection in partially heated square cavity has yet to be filled. Because of this, this study aims to investigate the entropy generation analysis as well as the natural convection in nanofluid-filled square cavity which was heated partially. A square cavity with an isothermal heater located on the bottom solid horizontal wall of the cavity and partly cold sidewalls are essential problems in thermal processing applications. Hence, the authors believe that this present work will be a valuable contribution in improving the thermal performance.
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Belarche, Lahoucine, Btissam Abourida, Slawomir Smolen, and Touria Mediouni. "Effect of the Inclination on Three-Dimensional Incompressible Fluid Flow in a Discretely Heated Cavity." Key Engineering Materials 597 (December 2013): 3–8. http://dx.doi.org/10.4028/www.scientific.net/kem.597.3.
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Natural convection in inclined cubic cavity, discretely heated, is studied numerically using a three-dimensional finite volume formulation. Two heating square portions are placed on the vertical wall of the enclosure, while the rest of the considered wall is adiabatic. These sections, similar to the integrated electronic components, generate a heat flux q". The opposite vertical wall is maintained at a cold uniform temperature Tc and the other walls are adiabatic. The fluid flow and heat transfer in the cavity are studied for different sets of the governing parameters, namely the Rayleigh number Ra (103 ≤ Ra ≤ 107), the cavity inclination γ (- 45° ≤ γ ≤ 45°) and the position of the heating sections λ (0.3 ≤ λ ≤ 0.7). The dimensions of the heater sections, ε = D / H and the longitudinal aspect ratio of the cavity Ax = H / L are respectively fixed to 0.35 and 1.
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Abdel Aziz, Salem S., and Abdel-Halim Saber Salem Said. "Numerical Investigation of Flow and Heat Transfer over a Shallow Cavity: Effect of Cavity Height Ratio." Fluids 6, no. 7 (July 3, 2021): 244. http://dx.doi.org/10.3390/fluids6070244.
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Flow over shallow cavities is used to model the flow field and heat transfer in a solar collector and a variety of engineering applications. Many studies have been conducted to demonstrate the effect of cavity aspect ratio (AR), but very few studies have been carried out to investigate the effect of cavity height ratio (HR) on shallow cavity flow behavior. In this paper, flow field structure and heat transfer within the 3-D shallow cavity are obtained numerically for two height ratio categories: HR = 0.0, 0.25, 0.5, 0.75, and 1.0 and HR = 1.25, 1.5, 1.75, 2.0, 2.25, and 2.5. The governing equations, continuity, momentum, and energy are solved numerically and using the standard (K-ε) turbulence model. ANSYS FLUENT 14 CFD code is used to perform the numerical simulation based on the finite volume method. In this study, the cavity aspect ratio, AR = 5.0, and Reynolds number, Re = 3 × 105, parameters are fixed. The cavity’s bottom wall is heated with a constant and uniform heat flux (q = 740 W/m2), while the other walls are assumed to be adiabatic. For the current Reynolds number and cavity geometry, a single vortex structure (recirculation region) is formed and occupies most of the cavity volume. The shape and location of the vortex differ according to the height ratio. A reverse velocity profile across the recirculation region near the cavity’s bottom wall is shown at all cavity height ratios. Streamlines and temperature contours on the plane of symmetry and cavity bottom wall are displayed. Local static pressure coefficient and Nusselt number profiles are obtained along the cavity’s bottom wall, and the average Nusselt number for various height ratios is established. The cavity height ratio (HR) is an important geometry parameter in shallow cavities, and it plays a significant role in the cavity flow behavior and heat transfer characteristics. The results indicate interesting flow dynamics based on height ratio (HR), which includes a minimal value in average Nusselt number for HR ≈ 1.75 and spatial transitions in local Nusselt number distribution along the bottom wall for different HRs.
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Nayaki, V. P. M. Senthil, S. Saravanan, X. D. Niu, and P. Kandaswamy. "Natural Convection Cooling of an Array of Flush Mounted Discrete Heaters Inside a 3D Cavity." Advances in Applied Mathematics and Mechanics 9, no. 3 (January 17, 2017): 698–721. http://dx.doi.org/10.4208/aamm.2015.m1245.
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AbstractAn investigation of natural convective flow and heat transfer inside a three dimensional rectangular cavity containing an array of discrete heat sources is carried out. The array consists of a row and columnwise regular arrangement of identical square shaped isoflux discrete heaters and is flush mounted on a vertical wall of the cavity. A symmetrical isothermal sink condition is maintained by cooling the cavity uniformly from either the opposite wall or the side walls or the top and bottom walls. The other walls of the cavity are maintained adiabatic. A finite volume method based on the SIMPLE algorithm and the power law scheme is used to solve the conservation equations. The parametric study covers the influence of pertinent parameters such as the Rayleigh number, the Prandtl number, side aspect ratio of the cavity and cavity heater ratio. A detailed fluid flow and heat transfer characteristics for the three cases are reported in terms of isothermal and velocity vector plots and Nusselt numbers. In general it is found that the overall heat transfer rate within the cavity for Ra=107 is maximum when the side aspect ratio of the cavity lies between 1.5 and 2. A more complex and peculiar flow pattern is observed in the presence of top and bottom cold walls which in turn introduces hot spots on the adiabatic walls. Their location and size are highly sensitive to the side aspect ratio of the cavity and hence offers more effective ways for passive heat removal.
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Cheong, Huey Tyng, S. Sivasankaran, and M. Bhuvaneswari. "Natural convection in a wavy porous cavity with sinusoidal heating and internal heat generation." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 2 (February 6, 2017): 287–309. http://dx.doi.org/10.1108/hff-07-2015-0272.
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Purpose The purpose of this paper is to study natural convective flow and heat transfer in a sinusoidally heated wavy porous cavity in the presence of internal heat generation or absorption. Design/methodology/approach Sinusoidal heating is applied on the vertical left wall of the cavity, whereas the wavy right wall is cooled at a constant temperature. The top and bottom walls are taken to be adiabatic. The Darcy model is adopted for fluid flow through the porous medium in the cavity. The governing equations and boundary conditions are solved using the finite difference method over a range of amplitudes and number of undulations of the wavy wall, Darcy–Rayleigh numbers and internal heat generation/absorption parameters. Findings The results are presented in the form of streamlines, isotherms and Nusselt numbers for different values of right wall waviness, Darcy–Rayleigh number and internal heat generation parameter. The flow field and temperature distribution in the cavity are affected by the waviness of the right wall. The wavy nature of the cavity also enhances the heat transfer into the system. The heat transfer rate in the cavity decreases with an increase in the internal heat generation/absorption parameter. Research limitations/implications The present investigation is conducted for steady, two-dimensional natural convective flow in a wavy cavity filled with Darcy porous medium. The waviness of the right wall is described by the amplitude and number of undulations with a well-defined mathematical function. An extension of the present study with the effects of cavity inclination and aspect ratio will be the interest for future work. Practical implications The study might be useful for the design of solar collectors, room ventilation systems and electronic cooling systems. Originality/value This work examines the effects of sinusoidal heating on convective heat transfer in a wavy porous cavity in the presence of internal heat generation or absorption. The study might be useful for the design of solar collectors, room ventilation systems and electronic cooling systems.
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Selamat, M. S., R. Roslan, and I. Hashim. "Natural Convection in an Inclined Porous Cavity with Spatial Sidewall Temperature Variations." Journal of Applied Mathematics 2012 (2012): 1–10. http://dx.doi.org/10.1155/2012/939620.
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The natural convection in an inclined porous square cavity is investigated numerically. The left wall is assumed to have spatial sinusoidal temperature variations about a constant mean value, while the right wall is cooled. The horizontal walls are considered adiabatic. A finite difference method is used to solve numerically the nondimensional governing equations. The effects of the inclination angle of the cavity, the amplitude and wave numbers of the heated sidewall temperature variation on the natural convection in the cavity are studied. The maximum average Nusselt number occurs at different wave number. It also found that the inclination could influence the Nusselt number.
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Lyubimov, Dmitriy, and Alena Fedorenko. "External flow velocity and synthetic jets parameters influence on cavity flow structure and acoustics characteristics using RANS/ILES." International Journal of Aeroacoustics 17, no. 3 (March 14, 2018): 259–74. http://dx.doi.org/10.1177/1475472x18763858.
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An influence of synthetic jets on the flow in a three-dimensional cavity M219 was studied using RANS/ILES method. Calculations were performed for Mach numbers M0 = 0.85 and M0 = 1.5. Synthetic jets’ operating parameters such as their position, number, frequency, and amplitude were varied. An impact of these parameters and M0 on flow in the cavity, distributions, and levels of pressure fluctuations on the cavity walls as well as the narrowband spectra of pressure fluctuations were obtained. Synthetic jets located in front of a cavity may reduce peak pressure pulsations on the cavity back wall by 37% for a subsonic external flow. Moreover, it was found that synthetic jets may decrease the second and the third modes of pressure fluctuations on the back wall both for subsonic flow and supersonic case.
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Ahmed, Sameh, Zehba Raizah, and Abdelraheem Aly. "Magnetohydrodynamic convective flow of nanofluid in double lid-driven cavities under slip conditions." Thermal Science, no. 00 (2020): 141. http://dx.doi.org/10.2298/tsci190811141a.
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In this paper, we introduced a numerical analysis for the effect of a magnetic field on the mixed convection and heat transfer inside a two-sided lid-driven cavity with convective boundary conditions on its adjacent walls under the effects of the presence of thermal dispersion and partial slip. A single-phase model in which the water is the base fluid and a copper is nanoparticles is assumed to represent the nanofluid. The bottom and top walls of the cavity move in the horizontal direction with constant speed, while the vertical walls of the cavity are stationary. The right wall is mentioned at relatively low temperature and the top wall is thermally insulated. Convective boundary conditions are imposed to the left and bottom walls of the cavity and the thermal dispersion effects are considered. The finite volume method is used to solve the governing equations and comparisons with previously published results are performed. It is observed that the increase in the Hartmann number causes that the shear friction near the moving walls is enhanced and consequently the horizontal velocity component decreases.
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Sun, Cheng Fang, and Hui Qin Wu. "Experimental Research on the Mechanic Performance of the Cavity Wall Material." Advanced Materials Research 476-478 (February 2012): 1657–60. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.1657.
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As a new high strength and environmental protection material, the cavity wall material has attracted increasing attention. It is made from paper with alveolus triangle inside. It has two talent rights in China, which one is “A kind of Composite Paper Technique with High Strength”; another is “A Kind of Cavity Composite Material with Alveolus Triangle inside”. As the infilling-wall of the steel frame building, the cavity composite masonry is made of the cavity material as the core wall and between two sides of fine aggregate concrete with wire-meshes, which can increase the bearing capacity and stiffness of the steel frame, and improve ductility and earthquake resistant behavior. In this paper, the mechanic performance of the cavity wall material is tested. Test result show that the cavity wall material has many good performance including lightweight, high-strength, heat insulation and sound insulation, and is a kind of good infilling wall material of the steel frame building. Therefore, the cavity wall material has a good prospect of application and extension.
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Kowsary, F., and J. R. Mahan. "Radiative Characteristic of Spherical Cavities With Specular Reflectivity Component." Journal of Heat Transfer 128, no. 3 (July 28, 2005): 261–68. http://dx.doi.org/10.1115/1.2151196.
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An exact analytical method is presented for determination of emissive as well as absorptive performance of spherical cavities having diffuse-specular reflective walls. The method presented utilizes a novel coordinate transformation technique, which provides convenient means for setting up the governing radiant exchange integral equations. These equations are then solved by the usual iterative method devized for the Fredholm integral equation of the second kind. The suggested coordinate transformation is also utilized for determination of directional absorptivity of a fully specular spherical cavity when collimated radiation enters through its mouth from a specified direction. Results show that for a spherical cavity the dependence of the apparent emissivity on the degree of specularity is high when the emissivity of the cavity wall is low, but this dependence decreases as the emissivity of the cavity wall increases. Also there are situations, unlike cases of cylindrical and conical cavities, for which the purely diffuse spherical cavity is a more efficient emitter than the purely specular cavity having an identical geometry and wall emissivity. Moreover, it is shown that the apparent directional absorptivity of specular spherical cavities having small openings becomes highly fluctuating as the direction of the incident radiation changes
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Kim, D. M., and R. Viskanta. "Effect of Wall Heat Conduction on Natural Convection Heat Transfer in a Square Enclosure." Journal of Heat Transfer 107, no. 1 (February 1, 1985): 139–46. http://dx.doi.org/10.1115/1.3247370.
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This paper presents numerical and experimental results for buoyancy-induced flow in a two-dimensional, fluid-filled enclosure. Rectangular cavities formed by finite conductance walls of different void fractions and aspect ratios are considered. Parametric heat transfer calculations have been performed and results are presented and discussed. Local and average Nusselt numbers along the cavity walls are reported for a range of parameters of physical interest. The temperatures in the walls were measured with thermocouples, and the temperature distributions in the air-filled cavity were determined using a Mach-Zehnder interferometer. Good agreement has been obtained between the measured and the predicted temperatures in both the solid wall and in the fluid using the mathematical model. Wall heat conduction reduces the average temperature differences across the cavity, partially stabilizes the flow, and decreases natural convection heat transfer.
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Sobhy, Issam, Abderrahim Brakez, and Brahim Benhamou. "ANALYSIS FOR THERMAL BEHAVIOR AND ENERGY SAVINGS OF A SEMI-DETACHED HOUSE WITH DIFFERENT INSULATION STRATEGIES IN A HOT SEMI-ARID CLIMATE." Journal of Green Building 12, no. 1 (January 2017): 78–106. http://dx.doi.org/10.3992/1552-6100.12.1.78.
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The purpose of this research is to assess thermal performance and energy saving of a residential building in the hot semi-arid climate of Marrakech (Morocco). The studied house is built as usual in Marrakech without any thermal insulation except for its external walls, facing East and West, which are double walls with a 5 cm air gap in between (“cavity wall” technique). The cavity wall effective thermal conductivity was carefully calculated taking into account both radiation and convection heat transfers. Experimental results, obtained from winter and summer monitoring of the house, show well dampening of air temperature, thanks to its thermal inertia. However, this temperature remained outside the standard thermal comfort zone leading to large cooling/heating load. Simulation results indicate that the cavity wall contributes to an overall reduction of 13% and 5% of the house heating and cooling loads respectively. Moreover, the addition of XPS roof thermal insulation significantly enhances the heating and cooling energy savings to 26% and 40% respectively.
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Ma, Guangwei, Mingbo Sun, Guoyan Zhao, Pei Liu, Tao Tang, Li Fan, and Hongbo Wang. "Numerical Investigation of an Axisymmetric Model Scramjet Assisted with Cavity of Different Aft Wall Angles." International Journal of Aerospace Engineering 2021 (August 2, 2021): 1–17. http://dx.doi.org/10.1155/2021/7525824.
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An axisymmetric model scramjet assisted with cavity flameholder is numerically investigated. Three-dimensional Reynolds-averaged Navier-Stokes simulation is carried out to reveal the fuel mixing and combustion characteristics. The simulation results show reasonable agreements with experimental data. The analysis indicates that the axisymmetric and rectangular scramjet has some similarities to the cavity shear layer in the nonreacting flow field. The configuration of the cavity shear layer changes hugely due to the significant chemical reaction and heat release in the reacting flow field. Typically, two more configurations with different cavity aft wall angles are compared with the experimental configuration to optimize the configuration of the cavity. When the cavity aft wall angle is small, the cavity shear layer bends to the cavity floor and more fuel enters into and stays in the cavity, which results in poor fuel mixing performance. With the increase of the aft wall angle, the fuel distributes more uniformly and the fuel mixing efficiency improves. In the reacting flow field, the volume of the cavity full of hot products and free radicals increases while the interaction between the cavity and main flow decreases with the increase of the aft wall angle. The improved combustion efficiency shows that larger cavity volume weighs more than reduced interaction between the cavity and main flow. The combustion is more violent in the case with a larger aft wall angle. Therefore, a proper increase of the aft wall angle is beneficial to the performance of cavity-assisted axisymmetric scramjet when designing the cavity flameholder.
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Rocha, L. A. O., C. Biserni, and E. Lorenzini. "CONSTRUCTAL THEORY APPLIED TO THE GEOMETRIC OPTIMIZATION OF ELLIPTICAL CAVITIES INTO A SOLID CONDUCTING WALL." Revista de Engenharia Térmica 7, no. 2 (December 31, 2008): 81. http://dx.doi.org/10.5380/reterm.v7i2.61782.
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This work reports, according to Bejan’s Constructal theory, the geometric optimization of an elliptical cavity that intrudes into a solid conducting wall. The objective is to minimize the global thermal resistance between the solid and the cavity. There is uniform heat generation on the solid wall. The cavity is optimized for two sets of thermal conditions: isothermal cavity and cavity bathed by a steady stream of fluid. The solid conducting wall is isolated on the external perimeter. The total volume and the elliptical cavity volume are fixed while the geometry of the cavity is free to vary. The results show that the optimized geometrical shapes are relatively robust, i.e., insensitive to changes in some of the design parameters: the cavity shape is optimal when penetrates the conducting wall almost completely.
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Rahman, Md Mustafizur, M. Arif Hasan Mamun, M. Masum Billah, and Saidur Rahman. "Natural convection flow in a square cavity with internal heat generation and a flush mounted heater on a side wall." Journal of Naval Architecture and Marine Engineering 7, no. 2 (February 15, 2011): 37–50. http://dx.doi.org/10.3329/jname.v7i2.3292.
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In this study natural convection flow in a square cavity with heat generating fluid and a finite size heater on the vertical wall have been investigated numerically. To change the heat transfer in the cavity, a heater is placed at different locations on the right vertical wall of the cavity, while the left wall is considered to be cold. In addition, the top and bottom horizontal walls are considered to be adiabatic and the cavity is assumed to be filled with a Bousinessq fluid having a Prandtl number of 0.72. The governing mass, momentum and energy equations along with boundary conditions are expressed in a normalized primitive variables formulation. Finite Element Method is used in solution of the normalized governing equations. The parameters leading the problem are the Rayleigh number, location of the heater, length of the heater and heat generation. To observe the effects of the mentioned parameters on natural convection in the cavity, we considered various values of heater locations, heater length and heat generation parameter for different values of Ra varying in the range 102 to 105. Results are presented in terms of streamlines, isotherms, average Nusselt number at the hot wall and average fluid temperature in the cavity for the mentioned parameters. The results showed that the flow and thermal fields through streamlines and isotherms as well as the rate of heat transfer from the heated wall in terms of Nusselt number are strongly dependent on the length and locations of the heater as well as heat generating parameter.DOI: 10.3329/jname.v7i2.3292
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Maheandera Prabu, P., and K. P. Padmanaban. "Laminar Wall Jet Flow and Heat Transfer over a Shallow Cavity." Scientific World Journal 2015 (2015): 1–16. http://dx.doi.org/10.1155/2015/926249.
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This paper presents the detailed simulation of two-dimensional incompressible laminar wall jet flow over a shallow cavity. The flow characteristics of wall jet with respect to aspect ratio (AR), step length (Xu), and Reynolds number (Re) of the shallow cavity are expressed. For higher accuracy, third-order discretization is applied for momentum equation which is solved using QUICK scheme with SIMPLE algorithm for pressure-velocity coupling. Low Reynolds numbers 25, 50, 100, 200, 400, and 600 are assigned for simulation. Results are presented for streamline contour, velocity contour, and vorticity formation at wall and also velocity profiles are reported. The detailed study of vortex formation on shallow cavity region is presented for various AR,Xu, and Re conditions which led to key findings as Re increases and vortex formation moves from leading edge to trailing edge of the wall. Distance between vortices increases when the step length (Xu) increases. When Re increases, the maximum temperature contour distributions take place in shallow cavity region and highest convection heat transfer is obtained in heated walls. The finite volume code (FLUENT) is used for solving Navier-Stokes equations and GAMBIT for modeling and meshing.
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Prasad, V. "Thermal Convection in a Rectangular Cavity Filled With a Heat-Generating, Darcy Porous Medium." Journal of Heat Transfer 109, no. 3 (August 1, 1987): 697–703. http://dx.doi.org/10.1115/1.3248144.
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Two-dimensional, steady natural convection in a rectangular cavity filled with a heat-generating, saturated porous medium has been studied numerically for the case when the vertical walls of the cavity are isothermal and the horizontal walls are either adiabatic or cold. Results are presented in terms of the streamlines and isotherms, the maximum temperature in the cavity, and the local and overall Nusselt numbers. The buoyant flow together with the uniform heat generation produces a highly stratified medium at high Rayleigh numbers. Although the maximum temperature in the cavity θmax invariably increases with the Rayleigh number Ra and aspect ratio A, the rate of increase diminishes with this enhancement in Ra and A. However, the change in the horizontal wall boundary condition from adiabatic to cold reduces θmax. The local heat flux on the bounding walls is a strong function of the Rayleigh number, the aspect ratio, and the wall boundary conditions. The variation in overall Nusselt number is qualitatively similar to that observed in the case of a differentially heated cavity, and the present heat transfer rates are close to that for the cavity heated by applying a uniform heat flux. Several correlations are presented for maximum temperature and overall Nusselt number.
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Jeyakumar, S., Shan M. Assis, and K. Jayaraman. "Effect of Axisymmetric Aft Wall Angle Cavity in Supersonic Flow Field." International Journal of Turbo & Jet-Engines 35, no. 1 (March 26, 2018): 29–34. http://dx.doi.org/10.1515/tjj-2016-0027.
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AbstractCavity plays a significant role in scramjet combustors to enhance mixing and flame holding of supersonic streams. In this study, the characteristics of axisymmetric cavity with varying aft wall angles in a non-reacting supersonic flow field are experimentally investigated. The experiments are conducted in a blow-down type supersonic flow facility. The facility consists of a supersonic nozzle followed by a circular cross sectional duct. The axisymmetric cavity is incorporated inside the duct. Cavity aft wall is inclined with two consecutive angles. The performance of the aft wall cavities are compared with rectangular cavity. Decreasing aft wall angle reduces the cavity drag due to the stable flow field which is vital for flame holding in supersonic combustor. Uniform mixing and gradual decrease in stagnation pressure loss can be achieved by decreasing the cavity aft wall angle.
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Arıcı, Müslüm, Ensar Tütüncü, Hasan Karabay, and Antonio Campo. "Investigation on the melting process of phase change material in a square cavity with a single fin attached at the center of the heated wall." European Physical Journal Applied Physics 83, no. 1 (July 2018): 10902. http://dx.doi.org/10.1051/epjap/2018180092.
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In this study, melting of a phase change material (PCM) in a square cavity with a single fin attached at the center of the heated wall is studied numerically employing the enthalpy-porosity method. The opposite wall to the heated wall in the square cavity is cold. The other two adjacent walls are thermally insulated. Paraffin wax is chosen as a PCM due to its demonstrable favorable properties. The thermophysical properties of the paraffin wax are assumed to be a dual function of temperature and phase. The influence of the fin length on the melting process of the paraffin wax is examined. Moreover, the orientation of the square cavity on the melting process is scrutinized. The numerical results elucidate that the melting rates increase significantly by embedding the fin into the paraffin wax. As the fin length is incremented, the melting rate intensifies considerably during the early stages of melting. However, the effect of the fin length on the melting rate diminishes after a long period of heating has happened. It is also observed that the melting rate can be augmented significantly by changing the orientation of the heated wall in the square cavity.
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Piña-Ortiz, A., JF Hinojosa, JMA Navarro, and J. Xamán. "Experimental and numerical study of turbulent mixed convection in a cavity with an internal heat source." Journal of Building Physics 42, no. 2 (December 7, 2017): 142–72. http://dx.doi.org/10.1177/1744259117735451.
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In this study, experimental and numerical results of heat transfer in a ventilated cavity with an internal heat source are presented. The cavity represents a ventilated room with a person inside in a 1:3 scale. It has a vertical wall receiving a constant and uniform heat flux, while the opposite wall is kept at a constant temperature. The rest of the walls is adiabatic. The cavity has multiple inlets and outlets of air, considering ventilation by ducts of an air-conditioning system. Experimental temperature profiles were obtained at six different depths and heights consisting of 14 thermocouples each. Six turbulence models were evaluated against experimental data. The minimum average percentage differences between numerical and experimental average Nusselt numbers of the hot wall and heat source were 12.9% and 4.1% with the renormalized k–ε turbulence model.
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Khetib, Yacine, Ahmad Aziz Alahmadi, Ali Alzaed, Hamidreza Azimy, Mohsen Sharifpur, and Goshtasp Cheraghian. "Effect of Straight, Inclined and Curved Fins on Natural Convection and Entropy Generation of a Nanofluid in a Square Cavity Influenced by a Magnetic Field." Processes 9, no. 8 (July 30, 2021): 1339. http://dx.doi.org/10.3390/pr9081339.
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In this paper, the free convective heat transfer of nanofluids in a square cavity is simulated using a numerical method. The angle of the cavity could be changed in the horizontal axis from 0 to 90 degrees. The cavity is exposed under a constant magnetic field. Two opposite walls of the cavity are cold and warm, and the rest of the walls are insulated. On the hot wall, there are two fins with the same wall temperature. The equations were discretized by the finite volume method (FVM) and then solved using the SIMPLE algorithm. Three different fin configurations (straight, inclined and curved) were studied in terms of heat transfer rate and generation of entropy. According to the simulation results, the heat transfer rate was improved by tilting the fins toward the top or bottom of the cavity. At Ra = 105 and Ha = 20, the maximum heat transfer rate was achieved at a cavity inclination of 90° and 45°, respectively, for straight and curved fins. In the horizontal cavity, heat transfer rate could be improved up to 6.4% by tilting the fins and up to 4.9% by warping them. Increasing the Hartmann number from 0 to 40 reduced the Nusselt number and entropy generation by 37.9% and 33.8%, respectively.
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Howe, M. S. "Wall-Cavity Acoustic Green's Function at Low Mach Number." International Journal of Aeroacoustics 2, no. 3 (July 2003): 351–69. http://dx.doi.org/10.1260/147547203322986179.
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Analytical approximations are developed for the low Mach number, aeroacoustic Green's function for a rectangular or circular cylindrical open cavity in a plane, rigid wall. The formulae can be used to predict the sound radiated into the main flow from a knowledge of the hydrodynamic flow near the cavity. At low Mach numbers the sound is a small by-product of the main flow, whose hydrodynamic properties can first be determined from observation or from a numerical treatment of the incompressible Navier-Stokes equations. Detailed predictions are made of the lowest order, open cavity resonance frequencies, and it is shown how a resonance is excited by the unsteady drag, and also by the lift or drag force experienced by a small bluff body placed in the flow close to the cavity. The cavity resonance frequencies are complex, with imaginary parts depending primarily on radiation damping, which can be sufficiently large for a shallow, open cavity, that a distinct resonance peak is absent from the acoustic spectrum – for a square cavity such peaks are predicted only when the cavity depth exceeds about half the cavity length. For very shallow cavities the efficiency of sound production by volumetric pulsations within the cavity is comparable to that of free field turbulence quadrupoles, and therefore negligible at low Mach numbers.
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Javed, T., Z. Mehmood, M. A. Siddiqui, and Ioan Pop. "Effects of uniform magnetic field on the natural convection of Cu–water nanofluid in a triangular cavity." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 2 (February 6, 2017): 334–57. http://dx.doi.org/10.1108/hff-10-2015-0448.
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Purpose The purpose of this paper is to perform a numerical study for heat transfer through natural convection in the presence of a constant magnetic field in an incompressible steady nanofluid flow inside an isosceles triangular cavity. Design/methodology/approach For this flow problem, the left wall of the cavity subjected to uniform/nonuniform heat was considered, while right and bottom walls of the cavity were kept cold. The obtained equations were solved by using the Galerkin weighted residual technique. Results are computed for a wide range of parameters including Rayleigh number (Ra) (10^3 < Ra < 10^7), Hartman number (Ha) (0 < Ha < 60), and heat-generation/-absorption coefficient (q) (−10 < q < 10), while, Prandtl number (Pr) was kept fixed at 6.2. These computed results are presented in terms of stream functions, isotherms, Nusselt numbers and average Nusselt numbers through figures. Findings It is observed that, in case of uniform heating of the side wall, the strength of stream lines’ circulations increases with an increase in Ra and decreases with an increase in Ha. Similarly, by increasing heat-absorption coefficient q, an increase in the circulation strength is noted and the circulation cell moves towards the left wall in the presence of a heat sink (q < 0) and moves to the cold right wall in the presence of a heat source (q > 0). In the case of nonuniformly heated left wall in the presence of a heat source (q > 0), a higher-temperature gradient is observed in the cavity and isotherms are clustered to the left wall in the lower portion and to right wall in the upper portion; these appear to be straight and parallel to the x-axis near the bottom wall. On the other hand, the heat transfer rate along all the walls of the cavity is observed to be higher for smaller values of q. Whereas, Nusselt number along the bottom wall (Nu-B) increases with an increase in the values of x, while, that along the left wall (Nu-L) first increases and then decreases. But Nusselt number along the right wall (Nu-R) is found to be qualitatively opposite to Nu-L with an increase in distance x. Whereas, average Nusselt number increases with an increase in Rayleigh number Ra and heat-generation/-absorption coefficient q. Research limitations/implications The problem is formulated for an incompressible flow; viscous dissipation has been neglected, negligible induced magnetic field has been considered and local thermal equilibrium has been considered. Originality/value Results presented in this paper are original and new for the effects of a uniform magnetic field on the natural convection of Cu–water nanofluid in a triangular cavity. Hence, this study is important for researchers working in the area of heat transfer in cavity flows involving the nanofluid to become familiar with the flow behavior and properties.
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Nouri-Borujerdi, A., and F. Sepahi. "Turbulent Natural Convection in Partitioned Square Cavities with Different Lengths and Positions." Applied Mechanics and Materials 877 (February 2018): 313–19. http://dx.doi.org/10.4028/www.scientific.net/amm.877.313.
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The effect of partition on turbulent natural convection has been investigated numerically with different lengths and positions in an air filled square cavity. The top wall of the cavity is assumed to be cold and the other three walls are hot. Two-dimensional governing equations based on Reynolds-averaged Navier-Stokes equations are solved numerically by control volume method in a staggered grid manner. The iterative SIMPLE algorithm is also used to solve the discretized momentum equations to compute the intermediate velocity and pressure fields linked through the momentum equations. The hybrid differencing scheme which is based on a combination of central and upwind schemes is employed to discretize the convective and diffusion terms of the equations respectively. To describe the structure of turbulent flow which is changed due to the increasing importance of viscous effects, wall function was applied to simulate the turbulent flow. The results show that when the partition is placed on the top or bottom wall, the heat transfer rate through the bottom wall increases by increasing the partition length. The number of vortices established in the cavity depends on the partition length. Furthermore, when the partition is mounted on the left or right wall, only a small part of the top wall has a direct interaction with the left wall and the rest of that has an indirect interaction with the bottom wall.
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Aviram, D. P., A. N. Fried, and J. J. Roberts. "Thermal properties of a variable cavity wall." Building and Environment 36, no. 9 (November 2001): 1057–72. http://dx.doi.org/10.1016/s0360-1323(00)00042-1.
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Simpson, A., D. E. O'Connor, and A. D. Stuckest. "Mineral fibre filled cavity wall: Hygrothermal properties." Building Services Engineering Research and Technology 12, no. 4 (November 1991): 137–43. http://dx.doi.org/10.1177/014362449101200403.
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Fedriani, R., A. Caratti o Garatti, M. Koutoulaki, R. Garcia-Lopez, A. Natta, R. Cesaroni, R. Oudmaijer, D. Coffey, T. Ray, and B. Stecklum. "Mirror, mirror on the outflow cavity wall." Astronomy & Astrophysics 633 (January 2020): A128. http://dx.doi.org/10.1051/0004-6361/201936748.
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Aims. The inner regions of high-mass protostars are often invisible in the near-infrared, obscured by thick envelopes and discs. We aim to investigate the inner gaseous disc of IRAS 11101-5829 through scattered light from the outflow cavity walls. Methods. We observed the immediate environment of the high-mass young stellar object IRAS 11101-5829 and the closest knots of its jet, HH135-136, with the integral field unit VLT/SINFONI. We also retrieved archival data from the high-resolution long-slit spectrograph VLT/X-shooter. We analysed imaging and spectroscopic observations to discern the nature of the near-infrared CO emission. Results. We detect the first three bandheads of the υ = 2−0 CO vibrational emission for the first time in this object. It is coincident with continuum and Brγ emission and extends up to ~10 000 au to the north-east and ~10 000 au to the south-west. The line profiles have been modelled as a Keplerian rotating disc assuming a single ring in local thermodynamic equilibrium. The model output gives a temperature of ~3000 K, a CO column density of ~1 × 1022 cm−2, and a projected Keplerian velocity vK sin idisc ~ 25 km s−1, which is consistent with previous modelling in other high-mass protostars. In particular, the low value of vK sin idisc suggests that the disc is observed almost face-on, whereas the well-constrained geometry of the jet imposes that the disc must be close to edge-on. This apparent discrepancy is interpreted as the CO seen reflected in the mirror of the outflow cavity wall. Conclusions. From both jet geometry and disc modelling, we conclude that all the CO emission is seen through reflection by the cavity walls and not directly. This result implies that in the case of highly embedded objects, as for many high-mass protostars, line profile modelling alone might be deceptive and the observed emission could affect the derived physical and geometrical properties; in particular the inclination of the system can be incorrectly interpreted.
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Fusayama, Takeo. "Optimal Cavity Wall Treatment for Adhesive Restorations." Journal of Esthetic and Restorative Dentistry 2, no. 4 (July 1990): 95–99. http://dx.doi.org/10.1111/j.1708-8240.1990.tb00619.x.
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Rocha, L. A. O., G. C. Montanari, E. D. Dos Santos, and A. Da S. Rocha. "CONSTRUCTAL DESIGN APPLIED TO THE STUDY OF CAVITIES INTO A SOLID CONDUCTING WALL." Revista de Engenharia Térmica 6, no. 1 (June 30, 2007): 41. http://dx.doi.org/10.5380/reterm.v6i1.61816.
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This paper relies on the Constructal Design to optimize the geometry of a cavity that penetrates into a solid conducting wall. The objective is to minimize the global thermal resistance between the solid and the cavity. There is uniform heat generation on the solid wall. We studied three shapes of the cavity: rectangular, triangular, and elliptical. The total volume and the cavity volume are fixed with variable aspect ratios. The cavity shape is optimal when it penetrates the conducting wall completely. The rectangular cavity performs better than the elliptical and triangular ones. On the other side, the elliptical cavity has better performance than the triangular one. We also optimized a first construct, i.e., a cavity shaped as T. The performance of the T-shaped cavity is superior to that of the rectangular cavity optimized in the first part of the paper.