Walls Of Enclosure Research Articles

On the influence of circulation on fire whirl height

This work presents a numerical study of laboratory fire whirls. The Reynolds Stress Transport turbulence model RST is used together with Eddy Break-Up combustion and radiation models. The unsteady 3D fire whirl prediction assume the same swirl generator used in the laboratory consisting on enclosure walls to constrict airflow to enter tangentially in the facility. A low momentum fuel jet is located at the bottom centre of two halves of an offset hollow cylinder. A detailed comparison between available experimental data and numerical predictions, ranging from 2 to 300 kW is presented. The results are in good agreement with the available experimental data. The flame height dependence on circulation was deduced using scaling laws and validated with experimental data. For each heat release considered, a critical circulation was found that results in a maximum flame height. Turbulence fields predictions are discussed in light of the role of turbulent suppression and Richardson parameters.

A Novel System and Experimental Verification for Locating Partial Discharge in Gas Insulated Switchgears

Abstract Partial discharge location in gas insulated switchgears is important for timely identifying incipient problem and taking remedial actions to prevent later catastrophic breakdowns. This paper presents a new system including sensing terminals and hand-held intelligent terminals to locate partial discharge. Sensing terminals, housing the sensors, are attached to outside enclosure walls of the switchgear to collect acoustic signals, which are transmitted wirelessly to the hand-held terminals. The acoustic vibration caused by the discharge will propagate from the source, resulting in the highest intensity at the sensor closest to the discharge. By examining the signal signatures of the distributed sensors, the location of the partial discharge can be derived. The system is applied in both staged simulation environment and actual factory high voltage tests. The results have demonstrated that the system developed is highly effective in locating partial discharge in gas insulated switchgears and is suitable for practical applications.

The investigations on the heat transfer in thermal energy storage with time-dependent heat flux for power plants

The latent thermal energy storage (LTES) using phase change material (PCM) is able to improve the efficiency of power plants. However, the convectional TES using constant heat flux will reduce the ratio latent heat, leading to the higher temperature at the end of energy storage and more cost of heat preservation (more expensive material and thicker wall of enclosure). Consequently, the LTES with two energy storage tanks are proposed. The heating method is simplified as time-dependent heat flux boundary and the effects of periods, Rayleigh numbers and amplifications are studied numerically. The results show that the time-dependent scheme can reduce the final average temperature of PCM. However, the total melting time is nearly twice as much as that of constant scheme when the amplification is 1.0. In order to enhance the heat transfer, the heat flux applied to the TES is enlarged with amplification factor. When the amplification is 2.0, the latent heat gets energy from sensible heat and the temperature difference between wall and adjacent PCM is larger. As a result, the total melting time is decreased compared with the constant scheme.

Active Structural Acoustic Control of an Active Casing Placed in a Corner

Electric appliances used in workplaces and everyday life often generate a low-frequency noise, which affects human body systems. Passive methods employed to reduce noise are not effective at low frequencies. The classical approach to active noise control practically involves the generation of local zones of quiet, whereas at other areas the noise is reinforced. Moreover, it usually requires a large number of secondary sound sources. Hence, an active casing approach has been developed. The active casing panels’ vibrations are controlled to reduce the device noise emission. Efficiency of this method has been previously confirmed by the authors and the results have been reported in multiple journal publications. However, in the previous research experiments, the active casing was placed at a distance from the enclosure walls. In this research, the active casing is located in a corner and such placement is intentionally used to facilitate the active control system’s operation. The noise reduction performance is investigated at multiple configurations, including a range of distances from the corner and different error microphone arrangements. The analysis of both primary and secondary paths is given. Advantages and drawbacks of different active casing configurations are presented and discussed.

Leukemia in Ancient Egypt: Earliest case and state‐of‐the‐art techniques for diagnosing generalized osteolytic lesions

AbstractMalignant bone tumors are uncommon among archaeological skeletal remains, and the general skeletal involvement is even less frequent. Multiple myelomas along with metastases are the most common conditions in paleopathology, whereas malignant myeloproliferative diseases have only been described in a handful of cases.We present a probable case of acute lymphocytic leukemia in a skeleton of an individual from Ancient Egypt, dated to the end of the First Intermediate Period and the beginning of the Middle Kingdom (c 2160–2000 bc). The excavation of the Temple of Millions of Years of Thutmosis III located in el‐Assasif (Luxor, Upper Egypt) recovered a total of 41 complete individual from an associated grave‐Necropolis placed close to the north enclosure wall. The individual, a 16 to 21‐year‐old male, showed a severe disease affecting all the skeleton with, predominantly, osteolytic lesions and areas of new bone formation. Gross examination under magnification and X‐ray in field were performed.We review the paleopathological literature to compare the cases previously reported of malignant disease. The morphology and distribution of the lesions of the individual are discussed to make an adequate differential diagnosis in the individual. Several criteria suggest that the disease was most likely acute lymphocytic leukemia: The individual died before the age of 21, the patterns of the bone lesions as well as its distribution below the elbow and knee joints, the presence of a gap in the coronal suture, and the mandible involvement.If this is the case, it would be the oldest case of leukemia described in Ancient Egypt and could help to understand the evolution patterns of cancer in the history.

Natural convection in a square enclosure with two hot inner cylinders, Part II: The effect of two elliptical cylinders with various aspect ratios in a vertical array

In this study, two-dimensional numerical simulations were conducted for the natural convection in a cold square enclosure with a vertical array of two hot elliptical cylinders at Rayleigh numbers of 104 ≤ Ra ≤ 106. We observed the effect of the aspect ratios of the elliptical cylinders in the range of 0.25 ≤ AR ≤ 4.00. The immersed boundary method (IBM), which is based on the finite volume method (FVM), was used to capture the virtual wall boundary of the cylinders. The transition of the flow regime from steady state to unsteady state depends on the aspect ratio at Ra = 106. At low Rayleigh numbers of Ra = 104 and Ra = 105, the time- and surface-averaged Nusselt numbers for the enclosure walls increase with the AR of the upper elliptical cylinder. At a relatively high Rayleigh number of Ra = 106, the time- and surface-averaged Nusselt numbers of the enclosure walls increase by 3.9% at the upper elliptical cylinder at AR = 0.50 and at the lower elliptical cylinder at AR = 2.00 compared to two circular cylinders.

A major leak in a crude oil tank: Predictable and unexpected root causes

A 2000 m3 washer tank at a crude oil treatment plant suffered a structural collapse, involving total loss of integrity. A fast fracture initiated in a sector of the shell with a severe thickness reduction due to combined internal and external corrosion. The fracture bent and propagated horizontally, at the shell-roof intersection and at the joint between second and third courses, causing the almost instant opening of a large window. Due to the large initial leakage flow, the containment enclosure wall could not hold the spilled mixture of water and crude oil. The fast leaking wave damaged the breakwaters at the top of the wall, overpassed the enclosure and pushed out a sliding gate, thus causing total liquid leakage. Fracture and computational fluid dynamics models were developed to understand the origins of the failure, as well as to reconstruct the sequence of events. Deficiencies in tank construction, maintenance adequacy, and corrosion prevention were found to be the main root causes of the failure.

Experimental investigation of cross flow mixing in a randomly packed bed and streamwise vortex characteristics using particle image velocimetry and proper orthogonal decomposition analysis

The study of flow and heat transfer through porous media or randomly packed beds is important as these configurations are widely used in many engineering applications, for example, heat energy storage, chemical catalytic reactors, and nuclear reactors. The flow mixing characteristics in a cross-flow plane of a facility with randomly packed spheres at an aspect ratio of 6.3 were experimentally investigated. The velocity fields at several regions of the cross-flow plane located in the vicinity of the wall and in the pores between spheres were obtained by applying the matched-index-of-refraction and time-resolved particle image velocimetry (TR-PIV) techniques for Reynolds numbers ranging from 700 to 1700. The TR-PIV results revealed various flow patterns in the transverse plane of the packed spheres, including swirling flow structures aligned with the axial flow direction, a strong bypass flow near the enclosure wall, and a circulation region created when the bypass flow ejected into a large spatial gap. When the Reynolds number was increased, the peaks of root-mean-square fluctuating velocities, urms′ and vrms′, were found to increase approximately at the same ratio as the increase in Reynolds number, and the magnitude of the Reynolds stress increased considerably. In addition, the characteristics of flow mixing in different flow regions were investigated via the two-point cross-correlation of fluctuating velocities. Using Taylor’s hypothesis, the vorticity iso-surfaces were constructed. Thus, constructed iso-surfaces showed that shear layers generated from the bypass flow gaps were stretched, broken into smaller flow structures, and then evolved as vortex pairs when entering the neighboring gaps. The results obtained by applying proper orthogonal decomposition (POD) analysis to the velocity fields showed that the statistically dominant flow structures had approximately the same size and shape as those depicted by Taylor’s hypothesis. Vortex characteristics, such as populations, spatial distributions, and strengths, for various spatial regions and Reynolds numbers were obtained by a combination of POD analysis and vortex identification.

A numerical study on the three-dimensional natural convection with a cylinder in a long rectangular enclosure. Part I: Size effect of a circular cylinder or an elliptical cylinder

This study conducted three-dimensional numerical simulations of the natural convection in a long, cold, rectangular enclosure containing a hot, circular cylinder or an elliptical cylinder. The immersed boundary method (IBM) was used to capture the virtual wall boundary of the cylinder based on the finite volume method (FVM). Four radii of inner cylinders were considered in the Rayleigh number range of 104 ≤ Ra ≤ 106 as key simulation parameters to investigate the size effect of the circular and elliptical cylinders. The detailed effects were analyzed by visualization of the three-dimensional iso-surfaces of the temperature and vortical structures, as well as the three-dimensionality in the system. The heat transfer characteristics from the surfaces of a circular cylinder or elliptical cylinder and the walls of enclosure were addressed. The heat transfer characteristics were affected by the radius of the circular and elliptical cylinders.

Seismic Performance of Enclosure Wall in Postearthquake Temporary Prefabricated Light‐Weight Steel Structure

For the postearthquake temporary prefabricated light‐weight steel structure, the enclosure walls composed of prefabricated slender columns and prefabricated strip slabs were used in the structure, which were manufactured from construction waste, such as fragments of bricks and tiles, concrete fragments, and chippings of stones. In order to obtain more accurate seismic performance of enclosure walls, a full‐scale two‐story experimental model was built to be placed on a shake table. In the test, acceleration transducers were fixed to the enclosure walls and steel frame, which were used to obtain the maximum acceleration of the enclosure walls and steel frame as well as natural frequency of the experimental model subjected to the seismic signal including Kobe wave and El‐Centro wave. Moreover, pull‐on the rope displacement transducers fixed to the exterior walls parallel to the direction of vibration were used to obtain the story drifts. The results of the shake table test show that when the experimental model is subjected to earthquake with maximum acceleration, enclosure walls are not damaged, owing to flexible connection between the steel frame and enclosure walls. Earthquake reduces the stiffness of enclosure walls, and the natural frequency of the experimental model decreases with increasing maximum acceleration of the seismic signal. In addition, based on the acceleration amplification coefficient, the collaborative performance of the steel frame and enclosure wall is better. Besides, when the experimental model is subjected to earthquake with maximum acceleration, the maximum story drift angle is only 1/2615.

El Templo de Millones de Años de Thutmosis III en Luxor: estudio paleopatológico preliminar y nuevas perspectivas

"The excavation work at the site of the Temple of Millions of Years of Thutmosis III (West Thebes) has revealed a large amount of human remains (skeletons and mummies) uncovered from two main locations: tombs placed within or next to the enclosure walls of the temple dated from the beginning of the Middle Kingdom to the Late Period and graves from a necropolis of the First Intermediate Period – 11th Dynasty close to the north-eastern enclosure wall. The aim of this anthropological and paleopathological study is to compare a population over time: the individuals of the Late Period to those of the Middle Kingdom. A total of 191 individuals have been studied (2016-2017):..154 from the tombs placed inside the wall of the temple and 37 from the tombs close to north-eastern wall. Preliminary conclusions showed a higher percentage of skeletal stress markers in the individuals from the First Intermediate Period – 11th Dynasty, compared with those from the Late Period"

Major Geological Fissure through Prehistoric Lion Monument at Giza Inspired Split Lion Hieroglyphs and Ancient Egypt’s Creation Myth

In search of textual references to a monumental lion at Giza predating the Old Kingdom, we focused our investigation on the earliest use of three ancient Egyptian hieroglyphs depicting the frontal and caudal halves of a lion and a fissure-like symbol. These symbols first appear in Egypt’s proto- and early dynastic era and form part of Egypt’s earliest known set of written language symbols. During the First Dynasty, these symbols were both carved into ivory tags and painted onto jars to designate the quality of oil shipped as grave goods to both royal and private tombs. The same iconography and symbols appear in the creation story recorded on the frieze and upper register of the Edfu Temple’s enclosure wall, where the frontal and caudal animal parts are used to name two of seven personified creation words, the so-called d3jsw1, uttered during the act of creating the world from the primordial flood Mehit-wrt by Ptah. Here, we show that the appearance of such unusual icons in such different contexts can be explained by a prominent physical feature (a geological fissure) affecting the appearance of the Great Sphinx, thus demonstrating that the original monument including this feature existed before these hieroglyphs were invented. We have previously argued that the Great Sphinx was remodeled from the much older monumental lioness Mehit. Here, we provide further evidence that this monument existed in the form of a lion or lioness at least seven centuries before the time of Khafre (circa 2500 B.C.E.) challenging the conventional model which attributes the original creation of the Great Sphinx to this Old Kingdom ruler.

Computational parametric study of latent melting heat storage

This paper presents a numerical study of the melting process of a phase change material for the cooling of a heat source “electronic component”. The latter is protruding and mounted on a substrate "motherboard" in the center of the bottom wall of a rectangular enclosure. The enclosure is filled completely with PCM. A 2D non-dimensional mathematical model is developed based on the conservation equations of mass, momentum and energy. The enclosure aspect ratio ‘A’ effect on the thermal and hydrodynamic behavior of the PCM-based heat sink is investigated.

Histria. Scanarea laser 3D a Turnului I / Histria. 3D Laser scanning of the Tower I

Scanarea laser 3D a fost făcută cu un dispozitiv Leica ScanStation 2, cu următoarele caracteristici tehnice principale : laser pulsatoriu, dublu ax compensat cu rezoluție de 1 inch, densitate puncte scanate < 1 mm, max. 50.000 pct/ sec, zona de interes fiind turnul I al incintei histriene romane târzii, post-gotice. Turnul I face parte din primul monument cercetat după descoperirea Histriei – zidul de incintă roman târziu, a cărui primă fază este datată în a doua jumătate a sec. al III-lea p. Chr. Pe frontul de vest al fortificației romane târzii, Turnul I ocupă un loc important, deoarece a reprezentat, pentru prima fază a acestui ansamblu defensiv, turnul de colț. De altfel, el va fi în continuare turn de colț până la construirea fazei C a incintei, care se va deplasa spre sud, incluzând și noul cartier din sudul orașului – construit pe terenul câștigat ca urmare a acceleratului proces de înnisipare din aceste secole. Mai mult, Turnul I are o situație stratigrafică deosebit de complexă, fiind plasat într-un loc în care suprapune atât zidul de incintă elenistic al Acropolei, cât și prima fază a incintei romane târzii post-gotice, dar și elemente constructive ale termelor. În același timp, el este înglobat fazelor ulterioare de existență ale incintei romane târzii. Din aceste motive, Turnul I este dificil de cercetat, deoarece părți ale acestor structuri sunt identificabile în substrucția sa, iar altele se găsesc și pot fi observate și cercetate numai în interiorul său. La toate acestea, se adaugă și tehnica de construcție cu totul deosebită utilizată în momentul ridicării acestei părți a fortificației, care folosește în loc de fundație un pat de fusuri de coloană așezate transversal pe direcția zidului. Câteva date arheologice au fost confirmate cu ajutorul scanerului 3D : identificarea traseului fundaţiei şi a tehnicii de construcţie folosite pentru incinta elenistică – utilizarea unui radier din dale de calcar refolosite (aşa cum demonstrează execuţia îngrijită şi urmele de crampoane de fier), ca şi în cazul frontului de vest al acestei incinte ; identificarea unor elemente constructive (blocuri din elevaţia zidului de incintă elenistic), modificate ca urmare a contactului îndelungat al acestei structuri defensive cu apa mării, prezentă aici în respectiva perioadă ; identificarea zidului de incintă elenistic şi a modului în care el a fost suprapus de următoarele faze ale turnului ; identificarea în acest punct a fazei A a incintei romane post-gotice ; înregistrarea structurilor constructive din interiorul turnului I ; observarea modului de suprapunere a elementelor menţionate de către fazele B şi C ale incintei. Aceste observaţii au fost confirmate de rezultatele înregistrate în secțiunile care au fost deschise la est de curtina i, în interiorul cetăţii. Deși cercetarea a fost deosebit de dificilă din cauza prezenței pânzei de apă freatică, care acoperă permanent dalele de calcar care formează fundația incintei elenistice, acestea au putut fi înregistrate cu ajutorul scanerului 3D de mare precizie și al colegilor noștri constănțeni, Irina Sodoleanu și Laurențiu Cliante. Nu puţine sunt lucrările de specialitate care s-au ocupat, de-a lungul timpului, de incinta romană târzie a Histriei, din diferite puncte de vedere. Articolul de faţă îşi propune să prezinte rezultatele unui demers tehnologic, menit a-şi aduce contribuţia nu numai la cunoaşterea unei părţi a acestei fortificaţii şi la conservarea cunoştinţelor şi informațiilor, dar şi la adăugarea unui element de precizie, prin scanarea 3D, la înregistrările datelor constructive şi arheologice.

Delimited Funerary Spaces – Hellenistic Tumuli with Stone Enclosures at Kallatis

This article analyzes the practice of delimiting tumuli graves with stone enclosures, mainly in the Classical and Hellenistic cemeteries of Kallatis/ Callatis (Mangalia), a Dorian establishment on the western Black Sea, following the recent exploration of a monumental tumulus ensemble, the Documaci Mound, built at the end of the 4th c. BC-early 3rd c. BC at 3 km west of the ancient city limits. The mound, covering a chamber tomb with semi-cylindrical vault, plastered walls and dromos, was surrounded at its base, measuring around 169 m in circumference, by a stone wall, 1.2 m high and 87 cm thick. After offering a systematic description of the Documaci Mound enclosure wall, the authors take on the occasion to discuss certain funerary architectural developments in the Greek colonies on the western and northern Black Sea shores, related to the use of periboloi and other stone delimitations (stone rings, kerbs, krepidae) during the Classical period, establishing also general connections with the building trends of the early Hellenistic period of erecting imposing funerary monuments in contexts related to enhancement of the individual identity expression in Macedonia and Thrace.

The Basic Tasks in Evaluation of Ancient Structures Sustainability and in Estimation of Enclosure Walls Bearing Capacity

The Basic Tasks in Evaluation of Ancient Structures Sustainability and in Estimation of Enclosure Walls Bearing Capacity

Impact of co‐flow on the spray flame behaviour applied to nanoparticle synthesis

AbstractFlame spray pyrolysis (FSP) is an established process to synthesize nanoparticles of various metals and metal oxides. Applying open or enclosed configurations of the FSP reactor is an efficient tool to control the fuel‐oxidizer ratio in the reaction zone and, thus, the temperature distribution and the particle formation and growth process. In the present work, geometrical setups representing an open and an enclosed flame reactor are compared and their influence on the temperature, velocity, and particle characteristics is investigated. In addition, several distinct kinetic mechanisms for the combustion reactions are evaluated and their effects on the local reactor temperature and gas composition distribution are analyzed. An Eulerian‐Lagrangian approach is adopted to describe the multiphase turbulent gas‐droplet flow and a monodisperse approach based on the population balance equation (PBE) model is implemented to predict the particle formation and evolution. From the open reactor results, the air entrainment mass flow rate of gas into the flame is calculated. Several numerical experiments are performed with the enclosed setup. Supplying an appropriate co‐flow rate into the enclosed reactor results in similar flame behaviour as found for the open reactor configuration. By reducing the co‐flow gas, strong recirculation zones and particle deposition on the enclosure walls are observed. In this situation, the local temperature increases considerably, resulting in larger primary nanoparticle diameters.

A numerical study on the three-dimensional natural convection with a cylinder in a long rectangular enclosure. Part II: Inclination angle effect of the elliptical cylinder

This study conducted three-dimensional numerical simulations of the natural convection in a cold, long, rectangular enclosure containing a hot elliptical cylinder. The immersed boundary method (IBM) was used to capture the virtual wall boundary of the inner cylinder based on the finite volume method (FVM). The effect of inclination angles of 0° ≤ ψ ≤ 90° were analyzed by a visualization technique with various radii of the cylinder at a relatively high Rayleigh number of Ra = 106. The variation in the flow and thermal structures and the corresponding heat transfer characteristics were investigated in regard to the transition of the flow regime from the steady state to the unsteady state. The heat transfer characteristics from the cylinder surface and enclosure walls were also addressed. As a result, the heat transfer characteristics were improved by the variation in the inclination angle in accordance with the mean radius of the elliptical cylinder.

Optimal Thermal Characteristics of the Courtyard in the Hot and Arid Climate of Isfahan

The courtyard is a common and traditional architectural concept in Middle Eastern countries, especially Iran. This study presents practical solutions to arrive at the optimal form and features of a courtyard based on this traditional architecture to cope with the hot and arid climate of Isfahan, Iran. A model using the ENVI-met 3.1 software was used to simulate the courtyard orientation, the height of the wall enclosure, the albedo of the materials and the vegetation level in Isfahan. As the first step of the simulation, different orientations were simulated. Based on the results, the northern courtyard is recommended as the optimum orientation for the remainder of the simulation process. A high wall enclosure is recommended in the second step of simulation to ensure cool temperatures at noon and warmth at night. In the third step, it is advised to use low-albedo material in the courtyards to avoid the extra reflected radiation of used materials on the inhabitants. The final step suggests that more than 50% of the courtyard plan should be covered by greenery to ensure thermal comfort in the courtyards. Based on these suggestions, designers can create more sustainable courtyards that are better suited to the hot and arid climate of Isfahan.

MIXED CONVECTION HEAT TRANSFER IN TRUNCATED CONE ENCLOSURE AS SOLAR CONTAINER WITH INTERNAL CENTERED TRIANGLE OBSTACLE

In this study, the mixed convection heat transfer of the air inside a truncated cone enclosure with aspect ratio of (0.75, 1.75, 2, 2.45 and 2.65) with centered triangle obstacle height varying by (0, 2.5, 5, 7.5, 10, 12.5 and 20 cm) and the heated wall inclination angles of (20o, 30o, 40o, 50o, 60o), the Richardson number in the range of (7 to 11) was investigated numerically. The results are addressed to automotive a suggested solar container with titled solar collector. The heat transfer from the heat source (inclined solar collector) of the enclosure walls is investigated for mixed convection as interaction of the forced convection flow between the inlet and outlet port in the bottom wall. The parameters of heat source, Reynolds number, obstacle height, enclosure aspect ratio, and left and right walls titled angles are considered in this work. The numerical simulation of the problem is carried out using commercial CFD code. The results are given in terms of the streamlines, isothermal, and the enclosure Nusselt number that characterizes the heat transfer from the heat source and from the interior fluid to the enclosure walls, respectively. The results show that the interaction of the main flow and the flow at the heated walls and the buoyancy force at the heated walls increased by using a triangular obstacle and by increasing the obstacle heights, it increased by 20% when using obstacle at position of (h=5 cm). Also, it is found that the Nu increased with increasing Re and the wall heat flux. The Nu increased with increasing Ri in the case of using (h=0 and 5 cm) but it decreased slightly in the other cases and showed that the minimum value of Nu present at a heated wall inclination of θ=50o but the maximum value at θ=30o.