Academic literature on the topic 'Duct wall'
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Journal articles on the topic "Duct wall":
1
Hawwa, Muhammad A. "Sound Propagation in a Duct with Wall Corrugations Having Square-Wave Profiles." Mathematical Problems in Engineering 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/516982.
Abstract:
Acoustic wave propagation in ducts with rigid walls having square-wave wall corrugations is considered in the context of a perturbation formulation. Using the ratio of wall corrugation amplitude to the mean duct half width, a small parameter is defined and a two levels of approximations are obtained. The first-order solution produces an analytical description of the pressure field inside the duct. The second-order solution yields an analytical estimate of the phase speed of waves transmitting through the duct. The effect of wall corrugation density on acoustic impedance and wave speeds is highlighted. The analysis reveals that waves propagating in a duct with square-wave wall corrugation are slower than waves propagating in a duct with sinusoidal wave corrugation having the same corrugation wavelength.
2
Nair, M. N. B., and S. V. Subrahmanyam. "Ultrastructure of the Epithelial Cells and Oleogumresin Secretion in Boswellia Serrata (Burseraceae)." IAWA Journal 19, no. 4 (1998): 415–27. http://dx.doi.org/10.1163/22941932-90000662.
Abstract:
The ultrastructure of epithelial cells of oleo-gumresin ducts in Boswellia serrata, the source of Indian olibanum, is described. Oleo-gumresin ducts are present in primary and secondary phloem. The duct lumen forms an enlarged apoplastic space surrounded by epithelial cells. The epithelial cells are rich in dictyosomes, lipid bodies, mitochondria with dilated cristae, multivesicular bodies, osmiophilic materials, plastids and vesicIes. Plastids have poorly developed internal membranes. Dictyosomes and plastids are possible sites of resin synthesis. The gum component of the exudate is formed in dictyosomes and from the outer layers of the inner tangential wall (wall facing the duct lumen). This wall is replenished from inside by the activity of dictyosomes. The secretory materials are transported to the apoplast by granulocrine and eccrine secretion. They migrate through the loose microfibrils of the inner tangential wall into the duct lumen. Rarely, epithelial cells of young ducts have rudimentary plasmodesmata on the inner tangential wall which may be channels for passage of secretory materials into the duct lumen.
3
Morrison, Janice C., L. Carl Greve, and John M. Labavitch. "The Role of Cell Wall-degrading Enzymes in the Formation of Gum Ducts in Almond Fruit." Journal of the American Society for Horticultural Science 112, no. 2 (March 1987): 367–72. http://dx.doi.org/10.21273/jashs.112.2.367.
Abstract:
Abstract Cell wall-degrading enzymes were extracted from the cell wall free space of mesocarp tissue from immature almonds [Prunus dulcis(Mill.)D.A. Webb, ‘Nonpareil’]. The activities of several of these enzymes were found to correlate with the development of gum ducts in this tissue. Polygalacturonase (EC 3.2.1.15) and 1,3-β-D-glucanase (EC 3.2.1.39) activities rose sharply at, or just prior to, the early schizogenous stage of duct initiation, while increases in α-galactosidase (EC 3.2.1.22), β-galactosidase (EC 3.2.1.23), α-arabinosidase (EC 3.2.1.55), and α-mannosidase (EC 3.2.1.24) activities were correlated with the later lysigenous stage of duct formation. Cell wall analysis of almond mesocarp tissue sampled the week preceding gum duct formation determined that the predominant noncellulosic sugars present in the mesocarp cell walls are arabinose, galactose, xylose, and glucose, with smaller amounts of rhamnose and mannose also present. The walls also contain a high percentage of galacturonic acid and trace amounts of glucuronic acid. Methylation analysis of the cell walls confirmed that many of the specific glycosidic linkages that are cleaved by the enzymes tested are present in the mesocarp cell walls immediately prior to gum duct formation.
4
Mahmoud, Mohammed H., Fouad A. Saleh, and Abeer H. Faleh. "Compound Heat Transfer Enhancement in Dimpled and Sinusoidal Metal Solar Wall Ducts Fitted with Wired Inserts." Journal of Engineering 18, no. 05 (June 19, 2023): 591–610. http://dx.doi.org/10.31026/j.eng.2012.05.05.
Abstract:
An improved Metal Solar Wall (MSW) with integrated thermal energy storage is presented in this research. The proposed MSW makes use of two, combined, enhanced heat transfer methods. One of the methods is characterized by filling the tested ducts with a commercially available copper Wired Inserts (WI), while the other one uses dimpled or sinusoidal shaped duct walls instead of plane walls. Ducts having square or semi-circular cross sectional areas are tested in this work.A developed numerical model for simulating the transported thermal energy in MSW is solved by finite difference method. The model is described by system of three governing energy equations. An experimental test rig has been built and six new duct configurations have been fabricated and tested. Air is passed through the six ducts with Reynolds numbers from 1825 to 7300.Six, new, correlations for Nusselt number and friction factor are developed to assess the benefits that are gained from using the WI and the dimpled and sine-wave duct walls. It is found that higher heat transfer rates are achieved using the Dimpled, semi–circular duct with Wired Inserts (DCWI). Also, it is found that Nusselt number and the pressure drop in the DCWI are respectively(44.2% -100%) and (101.27% - 172.8%) greater than those of the flat duct with WI. The improvement in Nusselt number for flat duct with WI is found to be (1.4 – 2) times the values for flat duct with no WI. The results demonstrated that DCWI provides enhancements efficiency value that is higher than those obtained from other types of ducts. The developed MSW ducts have added to local knowledge a better understanding of the compound heat transfer enhancement.
5
Ahn, SooWhan, and MyungSung Lee. "Heat Transfer Augmentation in a Divergent Duct with Angled Ribs." International Journal of Air-Conditioning and Refrigeration 25, no. 01 (March 2017): 1750008. http://dx.doi.org/10.1142/s2010132517500080.
Abstract:
Heat transfer characteristics in the rectangular divergent duct with parallel angled ribs are experimentally compared with the straight smooth circular duct. The ribs with four different parallel angles ([Formula: see text], 45[Formula: see text], 60[Formula: see text], and 90[Formula: see text]) are glued on the duct’s two opposite walls as well as on the duct’s one sided wall only, respectively. The 0.72[Formula: see text]-inclined walls are installed at the two opposite walls of the rectangular divergent duct. The test section of 1000[Formula: see text]mm long has the cross section of [Formula: see text][Formula: see text]mm2 at inlet and [Formula: see text][Formula: see text]mm2 at exit. The ribbed walls are manufactured with a rib height [Formula: see text][Formula: see text]mm and the ratio of rib spacing ([Formula: see text]) to height([Formula: see text]) [Formula: see text] 10. The main findings are summarized that the increase in the dimensionless Nusselt number for the flow attack angles can be seen in the order of 90[Formula: see text], 30[Formula: see text], 60[Formula: see text], and 45[Formula: see text] at the two opposite ribbed divergent wall ducts, in addition, the average Nusselt number in the divergent rectangular duct with two opposite ribbed walls is somewhat greater than in the ribbed straight cross-sectional rectangular duct.
6
Ashrafizadeh, A., G. D. Raithby, and G. D. Stubley. "Direct Design of Ducts." Journal of Fluids Engineering 125, no. 1 (January 1, 2003): 158–65. http://dx.doi.org/10.1115/1.1514201.
Abstract:
This paper describes a method for calculating the shape of duct that leads to a prescribed pressure distribution on the duct walls. The proposed design method is computationally inexpensive, robust, and a simple extension of existing computational fluid dynamics methods; it permits the duct shape to be directly calculated by including the coordinates that define the shape of the duct wall as dependent variables in the formulation. This “direct design method” is presented by application to two-dimensional ideal flow in ducts. The same method applies to many problems in thermofluids, including the design of boundary shapes for three-dimensional internal and external viscous flows.
7
Mateshuk-Vatseba, L. R., I. I. Hirniak, and U. Y. Pidvalna. "Morphological features of the wall of common bile duct under the conditions of experimental opioid exposure." Reports of Morphology 26, no. 2 (October 12, 2020): 26–31. http://dx.doi.org/10.31393/morphology-journal-2020-26(2)-04.
Abstract:
The morphological condition of the bile ducts remains one of the most important problems of modern medical science. In order to obtain an analgesic effect in patients with acute cholangitis, opioids are often used. However, information on the effectiveness of opioids in the treatment of pathological conditions of the bile ducts is contradictory. The rapidly progressive destruction of the intrahepatic bile ducts associated with the use of narcotic agents has been described. Further study of the effect of opioids on the structural organization of the common bile duct is relevant. In order to establish the morphological state of the common bile duct under conditions of long-term opioid exposure, a study was performed on 24 sexually mature white male rats, aged 3.5-5.0 months and weighing 180-200 g, which were injected intramuscularly with Nalbuphine for 6 weeks. The study material is represented by histological specimens of the common bile duct of white rats. The “Aver Media” computer system was used to photograph microspecimens. The “ImageJ” computer program was used to measure the diameter of the lumen and the wall thickness of the common bile duct. After 2 weeks of Nalbuphine administration to white rats, plethora of wall microvessels and a significant increase in the longitudinal diameter of the lumen of the common bile duct were observed. After 4 weeks of the experiment, the common bile duct was dilated, the transverse and longitudinal diameters of its lumen almost doubled, pathological changes in its wall had all the signs of inflammation. In the later stages of the experiment (introduction of Nalbuphine for 6 weeks), the pathological changes increased and manifested by destructuring the wall of the common bile duct, disorganization of cholangiocytes, thinning of the cell layer due to detachment of cholangiocytes, polymorphism of their nuclei, destruction of intercellular junctions, stratification of its own plate, vacuolar dystrophy of the muscular membrane “varicose” expansion of venules, significant smooth muscle hyperplasia of arterioles, the presence of perivascular lymphocytic infiltrates in the duct wall.
8
Nilsson, Erik, Sylvain Ménard, Delphine Bard Hagberg, and Nikolaos-Georgios Vardaxis. "Acoustical Treatments on Ventilation Ducts through Walls: Experimental Results and Novel Models." Acoustics 4, no. 1 (March 18, 2022): 276–96. http://dx.doi.org/10.3390/acoustics4010017.
Abstract:
Sound reduction is complex to estimate for acoustical treatments on ventilation ducts through walls. Various acoustical treatments are available for ventilation ducts, including internal lining (absorption along the inner perimeter), external lagging (external sound insulation), silencer, and suspended ceilings. Previous studies have examined how silencers and the internal lining affect the sound transmission of ventilation ducts. However, there are few theories to predict the effect of external lagging in combination with ventilation ducts and how the total sound reduction is affected. This article aims to investigate different acoustical treatments and develop theoretical models when external lagging with stone wool is used to reduce flanking sound transmission via the surface area of ventilation ducts. Theoretical models are developed for external lagging and compared with measurement data. Measurements and theory are generally in good agreement over the third-octave band range of 100–5000 Hz. The developed models clarify that the distance closest to the wall has the main impact on sound reduction for a combined system with a wall and a ventilation duct. Suspended ceilings and silencers are found to be enough as acoustical treatments for certain combinations of ventilation ducts and walls. However, external lagging seems to be the only effective solution in offices and schools when a large ventilation duct passes through a wall with high sound reduction.
9
Maloshtan, Oleksandr, Rostyslav Smachilo, Oleksandr Tishchenko, Аndrii Nekludov, Мariia Klosova, and Оleg Volchenko. "THE ROLE OF THE INFECTIOUS FACTOR IN THE DEVELOPMENT OF CHOLANGITIS." JOURNAL OF THE NATIONAL ACADEMY OF MEDICAL SCIENCES OF UKRAINE, Issue 1; 2021 (May 26, 2021): 32–37. http://dx.doi.org/10.37621/jnamsu-2021-1-4.
Abstract:
Introduction. The problems of the pathogenesis of cholangitis have not been finally clarified to date. Aim: to investigate the dynamics of microbial contamination of the biliary tract in obstructive jaundice before and after decompression. Materials and methods. To determine the significance of the infectious factor in the development of acute cholangitis, bile from the common bile duct was examined in 40 patients with the biliary tract obstruction, which were divided into three groups according to the clinical course of the disease. Results. The quantitative infection indicators of the common bile duct were studied in asymptomatic choledocholithiasis, in obstructive jaundice without clinical manifestations of cholangitis and in a developed clinic of cholangitis. It has been proven that endoscopic decompression of the biliary tree allows to obtain an almost instant therapeutic effect, the number of colony-forming units of the pathogen decreases by almost three orders of magnitude within 3 days. However, in phlegmonous inflammation of the bile duct wall patients, this period was significantly lengthened, and the course of the disease, according to the Tokyo Guidelines (2013), was assessed as severe. Conclusion. In the study of quantitative infection indicators in patients with a bright clinic of cholangitis, a significant decrease in the number of colony-forming units was observed already on the third day after endoscopic papilosphincterotomy due to an adequate drainage effect. When a stone is driven into the large papilla of the duodenum, the common bile duct turns into an analogue of an abscess. Opening the papilla not only frees the mouth of the duct from the stone, but also provides free passage of the contents of the common bile duct (pus) into the duodenum. This provides an almost instant healing effect. When comparing the severity of cholangitis with the histological picture of the wall of the bile ducts (common bile duct, intrahepatic ducts), data were obtained that it is in patients with a severe form of the disease that phlegmonous inflammation of the wall of the duct system takes place. When comparing the severity of cholangitis with the histological picture of the wall of the bile ducts (common bile duct, intrahepatic ducts), data were obtained that phlegmonous inflammation of the wall of the duct system is observed precisely in patients with a severe form of the disease. Keywords: cholangitis, endoscopic decompression
10
Subrahmanyam, S. V., and J. J. Shah. "The Metabolic Status of Traumatic Gum Ducts in Moringa Oleifera Lam." IAWA Journal 9, no. 2 (1988): 187–95. http://dx.doi.org/10.1163/22941932-90001067.
Abstract:
Traumatic gum ducts develop lysigenously in the bark of Moringa oleifera Lam. as a result of injury. The phloem parenchyma cells at the locus of gum duct formation enlarge and are enriched with cytoplasm and nucleoplasm. These duct initials show higher succinic dehydrogenase (SDH) and acid phosphatase (ACPase) activities compared to the neighbouring cells. The duct initials undergo autolysis to form the duct lumen. The epithelial cells of a gum duct have various shapes and show intense staining for nucleic acids, proteins and insoluble polysaccharides as compared to the neighbouring cells. The epithelial cells are also rich in enzymes viz. SDH, ACPase and lipase. Epithelial cells show labyrinthine wall deposition. These deposits are more towards the duct lumen side than the radial wall side. The inner tangential wall of the epithelial cells facing the duct lumen appears swollen. The degenerating epithelial cells show diffuse reaction products of SDH and ACPase. Some epithelial cells accumulate phenolics and by autolysis of such cells their phenolic contents are released into the gum duct.
Dissertations / Theses on the topic "Duct wall":
1
Slabaugh, Carson. "HEAT TRANSFER AUGMENTATION IN A NARROW RECTANGULAR DUCT WITH DIMPLES APPLIED TO A SINGLE WALL." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2172.
Abstract:
Establishing a clean and renewable energy supply is the preeminent engineering challenge of our time. Turbines, in some form, are responsible for more than 98 percent of all electricity generated in the United State and 100 percent of commercial and military air transport. The operation of these engines is clearly responsible for significant consumption of hydrocarbon fuels and, in turn, emission of green house gases into the atmosphere. With such wide-scale implementation, it is understood that even the smallest increase in the operating efficiency of these machines can lead to enormous improvements over the current energy situation. These effects can extend from a reduction in the emission of greenhouse gases to lessening the nation s dependence of foreign energy sources to lower energy prices for the consumer. The prominent means of increasing engine efficiency is by raising the  Turbine Inlet Temperature  the temperature of the mainstream flow after combustion, entering the first stage of the turbine section. The challenge is presented when these temperatures are forced beyond the allowable limits of the materials inside the machine. In order to protect these components, active cooling and protection methods are employed. The focus of this work is the development of more efficient means of cooling  hot turbine components. In doing so, the goal is to maximize the amount of heat removed by the coolant while minimizing the coolant mass flow rate: by removing a greater amount of heat with a lower coolant mass flow rate, more compressed air is left in the mainstream gas flow for combustion and power generation. This study is an investigation of the heat transfer augmentation through the fully-developed portion of a narrow rectangular duct (AR=2) characterized by the application of dimples to the bottom wall of the channel. Experimental testing and numerical modeling is performed for full support and validation of presented findings. The geometries are studied at channel Reynolds numbers of 20000, 30000, and 40000. The purpose is to understand the contribution of dimple geometries in the formation of flow structures that improve the advection of heat away from the channel walls. Experimental data reported includes the local and Nusselt number augmentation of the channel walls and the overall friction augmentation throughout the length of the duct. Computational results validate local Nusselt number results from experiments, in addition to providing further insight to local flow physics causing the observed surface phenomena. By contributing to a clearer understanding of the effects produced by these geometries, the development of more effective channel-cooling designs can be achieved.M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering MSME
2
Krishnan, Vaidyanathan. "The nature of Turbulence in a Narrow Apex Angle Isosceles Triangular Duct." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3811.
Abstract:
An experimental investigation was performed to ascertain the nature of turbulence in a narrow apex angle isosceles triangular duct. The study involved the design and construction of a low noise, low turbulence wind tunnel that had an isosceles triangular test section with an apex angle of 11.5[degrees]. Experiments involved the measurement of velocity fluctuations using hot wire anemometry and wall pressure fluctuations using a condenser microphone. Measurement of the velocity fluctuations reconfirms the coexistence of laminar and turbulent regions at a given cross section for a range of Reynolds numbers. The laminar region is concentrated closer to the apex while the turbulent region is found closer to the base. The point of transition is a function of the Reynolds number and moves closer to the apex as the flow rate is increased. Moreover, it was found in this investigation that traditional scaling of the turbulent statistical quantities do not hold good in this geometry. Although velocity fluctuations showed distinctive flow regimes, no such distinction could be seen in the dynamic wall pressure data. The nature of the dynamic wall pressure was uniform throughout the entire cross section suggesting that wall pressure fluctuations, unlike the velocity fluctuations, are able to travel from the base to the apex, without being damped. This implies that the relationship between the velocity and the pressure fluctuations applicable in the other systems does not hold well in a narrow apex angle isosceles triangular duct. Further, the typical scaling relationships applied to wall pressure spectra of other geometries doesn't apply in this scenario and the ratio of the RMS pressure fluctuation to the mean shear is much higher compared to a flat plate or pipe flow situation.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering PhD
3
He, Long. "A Study of Immersed Boundary Method in a Ribbed Duct for the Internal Cooling of Turbine Blades." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78069.
Abstract:
In this dissertation, Immersed Boundary Method (IBM) is evaluated in ribbed duct geometries to show the potential of simulating complex geometry with a simple structured grid. IBM is first investigated in well-accepted benchmark cases: channel flow and pipe flow with circular cross-section. IBM captures all the flow features with very good accuracy in these two cases. Then a two side ribbed duct geometry is test using IBM at Reynolds number of 20,000 under fully developed assumption. The IBM results agrees well with body conforming grid predictions. A one side ribbed duct geometry is also tested at a bulk Reynolds number of 1.5⨉10⁴. Three cases have been examined for this geometry: a stationary case; a case of positive rotation at a rotation number (Ro=ΩDₕ/U) of 0.3 (destabilizing); and a case of negative rotation at Ro= -0.3 (stabilizing). Time averaged mean, turbulent quantities are presented, together with heat transfer. The overall good agreement between IBM, BCG and experimental results suggests that IBM is a promising method to apply to complex blade geometries. Due to the disadvantage of IBM that it requires large amount of cells to resolve the boundary near the immersed surface, wall modeled LES (WMLES) is evaluated in the final part of this thesis. WMLES is used for simulating turbulent flow in a developing staggered ribbed U-bend duct. Three cases have been tested at a bulk Reynolds number of 10⁵: a stationary case; a positive rotation case at a rotation number Ro=0.2; and a negative rotation case at Ro=-0.2. Coriolis force effects are included in the calculation to evaluate the wall model under the influence of these effects which are known to affect shear layer turbulence production on the leading and trailing sides of the duct. Wall model LES prediction shows good agreement with experimental data.Master of Science
4
Kandindi, Muteba. "Heat transfer and pressure drop investigation for prescribed heat fluxes on both the inner and outer wall of the annular duct." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/61299.
Abstract:
Heat exchangers are used in industrial processes to recover heat between two
processes fluids and are widely used. Although the equations for heat transfer and
pressure drop characteristics in a double pipe heat exchangers are available, there is
still need to completely understand how these characteristics interact which
geometrical factors like annular diameter ratio or some thermal boundaries conditions
which have not yet drawn more attention from the research community.
The purpose of this study was to experimentally measure the heat transfer and
pressure drop characteristics of a concentric annular duct of ratio 0.593 for different
heat fluxes simultaneously on the inner and outer tube in the turbulent flow regime
and to describe or discuss the impact or interaction of heat flux ratios on the flow and
heat transfer behaviour.
An experimental set]up was designed to achieve this goal. It consisted of an overall
facility and a removable test section. The test section allowed for the measurement of
the temperature along the length of the test section, the pressure drop, the heat flux
inputs and the flow rate. These quantities were used to determine the heat transfer
coefficients and friction factors of the!system.
The concentric duct was an annulus formed of a single (15.88]mm]outer diameter and
14.46]mm]inner diameter) copper tube inserted inside a 0.91mm] thick] copper tube of
26.76 mm of inner diameter. The overall length of the annular duct was 4.84 m. To
transfer heat, a heating element made of constantan wire was wrapped around each
heat transfer area.
Heat transfer and pressure drop data were obtained on heating the inner and the outer
wall separately with four different heat flux densities and eight heat flux ratio were
used for the case of simultaneously heating both walls. Reynolds numbers for
unilateral heating range from 5800 to 12 000 while bilateral heating were focus around
two Reynolds numbers, 6 500 and 9 500.
Satisfactory results were found between the measurements of this experiment and
currently available literature for the case of unilateral heating. An estimate of the
accuracy of the experimental setup showed the maximum relative error was about 5 %
in the determination of the Nusselt number and 1.8 % for the friction factor.
Diabatic friction factors have been presented using adiabatic friction factors with a
correction term which considered the effect of temperature difference between the
fluid and walls. Heat flux density ratio showed to have an impact on the heat transfer
characteristics. The Nusselt number on the inner wall could be enhanced by 19% with
increasing the heat flux ratio up to 2.3 times.Dissertation (MSc)--University of Pretoria, 2016.
Mechanical and Aeronautical Engineering
MSc
Unrestricted
5
Myers, Jeremy. "Computational Fluid Dynamics in a Terminal Alveolated Bronchiole Duct with Expanding Walls: Proof-of-Concept in OpenFOAM." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/5011.
Abstract:
Mathematical Biology has found recent success applying Computational Fluid Dynamics (CFD) to model airflow in the human lung. Detailed modeling of flow patterns in the alveoli, where the oxygen-carbon dioxide gas exchange occurs, has provided data that is useful in treating illnesses and designing drug-delivery systems. Unfortunately, many CFD software packages have high licensing fees that are out of reach for independent researchers. This thesis uses three open-source software packages, Gmsh, OpenFOAM, and ParaView, to design a mesh, create a simulation, and visualize the results of an idealized terminal alveolar sac model. This model successfully demonstrates that OpenFOAM can be used to model airflow in the acinar region of the lung under biologically relevant conditions.
6
Jamois, Alexis. "Modélisation et réalisation d'absorbants acoustiques par impression 3D : étude en incidence normale et application au traitement d'un conduit." Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0010.
Abstract:
Au cours des dernières années, il est devenu possible de réaliser des absorbants acoustiques dont la géométrie était difficile à produire auparavant, grâce au perfectionnement des techniques d’impression 3D. La facilité d’utilisation et les prix abordables de ces techniques permettent d’imaginer la conception de dispositifs absorbants sur mesure pour répondre à une demande spécifique très rapidement. Cela nécessite d’une part de pouvoir imprimer précisément les géométries conçues et d’autre part de pouvoir prédire la performance acoustique des matériaux imprimés dans la configuration souhaitée. Les objectifs de cette thèse sont d’étudier l’effet de la variabilité des dimensions d’échantillons produits par impression 3D sur la performance acoustique et d’examiner différentes méthodes pour prédire la performance acoustique allant d’approches microscopiques complètes mais coûteuses, à des approches macroscopiques rapides mais simplifiées. La stéréolithographie a été choisie pour imprimer les échantillons à la suite d’une revue des moyens d’impression évalués dans la littérature. Les géométries étudiées consistent en un empilement de volumes (sphériques ou cubiques), reliés dans les trois directions de l’espace par des canaux à l’image de cristaux cubiques. Une variante à double réseau permet également d’ouvrir quelques pistes en vue d’une optimisation des performances acoustiques. Pour étudier l’effet de la variabilité, un grand nombre d’échantillons a été fabriqué avec différents jeux de paramètres d’impression et les dimensions caractéristiques des échantillons produits ont été mesurées. Un choix judicieux des paramètres permet de réduire la dispersion. La pertinence d’une approche fluide équivalent est montrée : elle permet de reproduire fidèlement et à coût réduit les résultats d’une approche directe résolvant les équations de Navier-Stokes linéarisées dans les pores des échantillons. Dans cette approche, les paramètres JCAPL des fonctions du fluide équivalent sont identifiés à partir d’un volume élémentaire représentatif de l’échantillon. Les échantillons sont d’abord étudiés en incidence normale. Le caractère très résonnant des matériaux rend le coefficient d’absorption très sensible à tout écart entre les dimensions cibles et les dimensions effectivement réalisées. Il en est ainsi pour les dimensions intérieures (diamètre des sphères ou des canaux) et pour le diamètre propre de l’échantillon. La nature rigide des échantillons produits par impression 3D rend très délicate leur adaptation stricte au diamètre du tube de Kundt. Les résultats de la mesure et les prédictions sont cependant globalement en bon accord et confirment dans ce cas classiquement traité dans la littérature, la validité du modèle de fluide équivalent. Des échantillons ont été ensuite réalisés spécifiquement pour être testés en paroi de conduit, par mesure de la perte par transmission. Les résultats expérimentaux confirment là aussi la pertinence de l’utilisation de l’approche fluide équivalent pour prédire les performances de ce type de matériau dans des conditions moins classiquesConventional rigid porous materials such as wools or foams do not provide effective absorption at low frequencies in complex industrial environments. For these applications, the structures developed are generally quarter-wave resonators or Helmholtz resonators. In recent years, 3D printing techniques have made it possible to produce resonator geometries that were previously difficult to produce. The ease of use and affordability of these techniques means that it is now possible to create tailor-made absorbing devices to meet specific requirements very quickly. This long-term objective requires, on the one hand, validation of the reliability of the dimensions obtained during the production of absorbent structures and, on the other hand, the ability to effectively model a variety of geometries in different contexts. In this thesis, stereolithography was chosen to print the samples based on literature results. Studies have concluded that it is more accurate for acoustic devices than other techniques. The geometry chosen for this study consists in a stack of volumes (spherical or cubic), connected in the three directions of space by channels in the image of cubic crystals. A large number of samples were manufactured varying the production parameters in order to measure the variability of the characteristic dimensions of the samples. Among the various modelling approaches presented, the numerical tests carried out led to the choice of equivalent fluid modelling based on the identification of JCAPL parameters. They are identified in a representative volume homogenised throughout the sample. This homogenisation of behaviour is suited to the geometries studied because of their periodic nature. The reaction of the geometries we are considering makes impedance modelling impossible. The samples are first studied at normal incidence, in order to link the variability of realisation to the measured acoustic behaviour. The measurement results and the predictions are in good agreement. Some samples were made specifically for duct wall measurement, in order to validate the use of the equivalent fluid approach. These tests were also used to confirm the conclusions drawn for normal incidence. The variability of the geometry has a real impact on the acoustic behaviour, but the main problem with rigid 3D printed samples is their adaptation to the measurement benches
7
AIT, ALDJET BOUHADEF KHEDIDJA. "Evaporation d'eau entre plaques parallèles humides sous l'effet d'un écoulement d'air en convection forcée : application à l'évaluation des transferts couplés de chaleur et de masse." Poitiers, 1988. http://www.theses.fr/1988POIT2009.
Abstract:
Le modele theorique est vase sur la resolution des equations couplees de transport-diffusion de masse et de chaleur, au sein du fluide en ecoulement, pour un regime de couches limites laminaires bidimensionnelles stationnaires. Le couplage des deux problemes thermique et massique est realise par l'intermediaire des conditions parietales. Des correlations sont etablies entre le coefficient de transfert de masse et les parametres adimensionnels caracterisant le probleme. Des performances d'evaporation, suivant les debits d'air et les conditions d'entree imposees, en decoulent. Des resultats experimentaux detailles, sur l'exploration des champs de vitesses, temperatures, et humidites locales, sont ensuite presentes pour les deux cas de regime: laminaire et turbulent. Les coefficients d'echange massique, local et global sont egalement evalues
8
Eames, Ian. "Displacement of material by a solid body moving away from a wall." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362975.
9
Walgode, Vitor. "Analysis and design of rectangular ducts with thin walls." Thesis, The University of Sydney, 1992. https://hdl.handle.net/2123/26742.
Abstract:
The objective of this research project, is to investigate if the current design practice of rectangular ducts with thin walls is adequate and if it can be improved. In order to achieve this goal, the following steps were taken:
1. Investigation of the available background research relevant to this topic.
2. Development of a finite element analysis model representative of the duct behaviour
for the cases in which the most suitable theories have a preponderant experimental
basis, taking in consideration the limitations of the available software (MSC/fAL 2).
3. Evaluation of the possibility of design improvement based on the previous work.
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Sebastian, Robin. "Numerical simulation of acoustic propagation in a turbulent channel flow with an acoustic liner." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2297/document.
Abstract:
Les matériaux absorbants acoustiques, qui sont d’un intérêt stratégique en aéronautique pour la diminution passive du bruit des réacteurs d’avion, conduisent à une physique complexe où l’écoulement turbulent, des ondes acoustiques, et l’absorbant interagissent. Cette thèse porte sur la simulation de cette interaction dans le problème modèle d’un écoulement de canal turbulent avec des parois impédantes, par le biais de simulations numériques aux grandes échelles implicites, dans un contexte de calcul haute performance.Une étude est d’abord faite des grandes échelles dans un canal turbulent avec des parois rigides, en s’intéressant plus particulièrement à l’effet d’une faible compressibilité (Mach <3) sur les caractéristiques de ces échelles.Un canal turbulent avec une paroi de type impédance est ensuite simulé, avec une condition habituelle de périodicité dans le sens de l’écoulement. On observe que pour des faibles valeurs de la résistance et des fréquences de résonance basses, l’écoulement est instable, ce qui engendre une onde le long de l’absorbant, qui modifie la turbulence et augmente la trainée.Enfin, on se tourne vers une simulation de canal spatial en levant la condition de périodicité dans la direction de l’écoulement, ce qui permet d’introduire une onde acoustique en entrée de domaine. L’atténuation de l’onde dans l’écoulement turbulent est étudiée avec des parois rigides, puis un absorbant acoustique est introduit. Dans cette configuration plus réaliste, il est confirmé que l’écoulement peut devenir instable au bord amont de l’absorbant, ce qui empêche l’atténuation de l’onde acoustique incidenteAcoustic liners are a key technology in aeronautics for the passive reduction of the noise generated by aircraft engines. They are employed in a complex flow scenario in which the acoustic waves, the turbulent flow, and the acoustic liner are interacting.During this thesis, in a context of high performance computing, a compressible Navier-Stokes solver has been developed to perform implicit large eddy simulations of a model problem of this interaction: a turbulent plane channel flow with one wall modeled as an impedance condition.As a preliminary step the wall-turbulence in rigid channel flows and associated large-scale motions are investigated. A straightforward algorithm to detect these flow features is developed and the effect of compressibility on the flow structures and their contribution to the drag are studied. Then, the interaction between the acoustic liner and turbulent flow is investigated assuming periodicity in the streamwise direction. It is shown that low resistance and low resonance frequency tend to trigger flow instability, which modifies the conventional wall-turbulence and also results in drag increase.Finally, the simulation of a spatial channel flow was addressed. In this case no periodicity is assumed and an acoustic wave can be injected at the inlet of the domain. The effect of turbulence on sound attenuation is studied without liner, before a liner is introduced on a part of the channel bottom wall. In this more realistic case, it is confirmed that low resistance acoustic liners trigger an instability at the leading edge of the liner, resulting in drag increase and excess noise generation
Books on the topic "Duct wall":
1
Rotter, Gabe. Duck duck wally. New York: Simon & Schuster, 2007.
2
Cowley, Joy. Duck walk. Auckland, N.Z: Scholastic, 2002.
3
Paine, Phil. Another wall bites the dust. San Francisco, CA: Atlantis Express, 1989.
4
Rotter, Gabe. Duck duck wally: A novel. New York: Simon & Schuster, 2007.
5
Productions, Walt Disney. Walt Disney's Donald Duck. Franklin, TN: Dalmatian Press LLC., 2006.
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Disney, Walt. Walt Disney's Katrien Duck. Hoofddorp: Sanoma Media, 2012.
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Disney, Walt. Walt Disney's Donald Duck pocketbook. Hoofddorp: Sanoma Media, 2013.
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Barks, Carl. Walt Disney comics 1st appearances. Prescott, Ariz: Gladstone, 1994.
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Carey, Mary. Walt Disneyʼs Donald Duck, TV star! New York: Golden Book, 1988.
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Barks, Carl. Walt Disney's Donald Duck als politieagent. Hoofddorp: VNU Tijdschriften, 2000.
Book chapters on the topic "Duct wall":
1
Owolabi, Bayode. "Turbulent Wall-Driven Flows." In Characterisation of Turbulent Duct Flows, 83–102. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-19745-2_6.
2
Vinuesa, Ricardo, Eduard Bartrons, Daniel Chiu, Jean-Daniel Rüedi, Philipp Schlatter, Aleksandr Obabko, and Hassan M. Nagib. "On Minimum Aspect Ratio for Experimental Duct Flow Facilities." In Progress in Wall Turbulence 2, 201–11. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-20388-1_18.
3
Volchkov, E. P., V. P. Lebedev, M. I. Nizovtsev, and V. I. Terekhov. "The Flow Separation from a Duct Wall Caused by the Near-Wall Counterjet." In Separated Flows and Jets, 493–501. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-84447-8_65.
4
Do, Richard K., and Daniel T. Boll. "Diseases of the Gallbladder and the Biliary Tree." In IDKD Springer Series, 121–30. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27355-1_8.
Abstract:
AbstractCross-sectional imaging modalities including ultrasound (US), magnetic resonance (MR) imaging, and computed tomography (CT) play a critical role in the diagnosis of diseases of the biliary tract and gallbladder. Biliary imaging for evaluation of obstructive jaundice seeks to diagnose the level of obstruction and its cause. The identification of dilated bile ducts necessitates evaluation for strictures or filling defects, which is best performed with thin-section CT or T2-weighted MR cholangiography (MRCP). Choledocholithiasis with accompanying cholecystolithiasis is the most common cause of biliary obstruction and modern thin-section three dimensional MR cholangiography is highly sensitive and specific for the detection of stones. Recognition of gallbladder wall thickening and surrounding edema may be seen in acute cholecystitis, identification of bile duct wall thickening raises concern for cholangitis or malignancy. Primary sclerosing cholangitis and secondary sclerosing cholangitis such as recurrent pyogenic cholangitis, and IgG4 related sclerosing disease can develop chronic progressive cholestatic liver disease characterized by inflammation, fibrosis, and stricture of the bile ducts. Familiarity with the typical clinical and radiologic appearances of various etiologies of cholangiopathies and biliary malignancies is also important for accurate image interpretation.
5
Große, S., and W. Schröder. "High spanwise wall-shear stress events in turbulent duct flow." In Springer Proceedings in Physics, 935–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03085-7_235.
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Wauer, J. "Nonlinear Waves in a Fluid-Filled Planar Duct with a Flexible Wall." In IUTAM Symposium on Recent Developments in Non-linear Oscillations of Mechanical Systems, 321–32. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4150-5_32.
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Aksoy, H., and R. M. C. So. "Near-Wall Turbulence Models and Their Application to Flow in a Square Duct." In Transition, Turbulence and Combustion, 23–37. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1034-1_3.
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Maksimović, Čedo. "Turbulence Structure of a Developing Duct Flow with Near-Wall Injection of Drag Reducing Polymers." In The Influence of Polymer Additives on Velocity and Temperature Fields, 359–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-82632-0_29.
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Auger, J. M., and J. M. Ville. "Flow Effects on Measurement of the Modal Decomposition of Acoustic Field in a Hard Wall Cylindrical Duct." In Aero- and Hydro-Acoustics, 437–43. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-82758-7_41.
10
Mohammadi, Shahriar, and Romuald Skoda. "Assessment of Static and Dynamic Wall-Adapting Subgrid-Scale Models for Turbulent Channel and Square Duct Flows." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 185–97. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60387-2_20.
Conference papers on the topic "Duct wall":
1
Mimic, Dajan, Marcel Oettinger, Christoph Jätz, Florian Herbst, and Joerg R. Seume. "Thermal End-Wall Contouring." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90191.
Abstract:
Abstract In this paper, we propose the concept of thermal end-wall contouring (TEWC) as a novel approach to reducing secondary-flow and boundary-layer losses in turbomachines and ducts by means of thermally manipulating the boundary layer. We introduce, for the first time, the general concept of TEWC and provide a proof of concept using the example of a bent duct. The results demonstrate that a considerable impact on the flow field is achieved not only by mean heat flux across the end-wall of the duct, but also by the spatial distribution of the heat fluxes.
2
Hwang, J. J., C. S. Cheng, and Y. P. Tsia. "Heat Transfer Enhancement in Triangular Ducts With an Array of Side-Entry Wall/Impinged Jets." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-195.
Abstract:
An experimental study has been performed to measure local heat transfer coefficients and static well pressure drops in leading-edge triangular ducts cooled by wall/impinged jets. Coolant provided by an array of equally spaced wall jets is aimed at the leading-edge apex and exits from the radial outlet. Detailed heat transfer coefficients are measured for the two walls forming the apex using transient liquid crystal technique. Secondary-flow structures are visualized to realize the mechanism of heat transfer enhancement by wall/impinged jets. Three right-triangular ducts of the same altitude and different apex angles of β = 30 deg (Duct A), 45 deg (Duct B) and 60 deg (Duct C) are tested for various jet Reynolds numbers (3000≦Rej≦12600) and jet spacings (s/d = 3.0 and 6.0). Results show that an increase in Rej increases the heat transfer on both walls. Local heat transfer on both walls gradually decreases downstream due to the crossflow effect. At the same Rej, the Duct C has the highest wall-averaged heat transfer because of the highest jet center velocity as well as the smallest jet inclined angle. Moreover, the distribution of static pressure drop based on the local through flow rate in the present triangular duct is similar to that that of developing straight pipe flows. Average jet Nusselt numbers on the both walls have been correlated with jet Reynolds number for three different duct shapes.
3
Ganesan, Rajamohan, Ramesh Narayanaswamy, Alexander Gorin, and Kumar Perumal. "Experimental Study on Mixed Convection Heat Transfer for Thermally Developing Flow in Horizontal Ducts With Radiation Effects." In ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44174.
Abstract:
This research focuses on the interaction of surface radiation with laminar mixed convection heat transfer for thermally developing airflow in horizontal ducts. The duct cross section is made of two differentially heated isothermal vertical walls and two adiabatic horizontal walls. In a series of experiments, the Reynolds number is varied from about Re = 800 to Re = 1200, for two aspect ratios of the duct cross section. The hot wall temperature ranges from 27°C to 100 °C, and the emissivity of internal walls are 0.05 and 0.85. The total heat transfer from the hot wall to the cold wall of the duct depends on the mixed convection and also on the surface radiation heat transfer that takes place within the duct. Therefore, it is important that the effects of surface radiation must be properly understood, and accounted for, in the design and analysis of flow and heat transfer through ducts. The results presented here show the effect of surface radiation and mixed convection on the total heat transfer rate within the duct. The flow field within the duct is also made visible by a suitable smoke flow visualization method.
4
Hwang, Sang Dong, Han Ho Kim, Hyung Hee Cho, and Seung Bae Chen. "Heat Transfer in Wavy Duct With Different Corrugation Angle." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32098.
Abstract:
The present study investigates the effects of duct corrugation angle and flow velocity on the convective heat/mass transfer characteristics in wavy ducts applied in a primary surface heat exchanger. Local heat/mass transfer coefficients on the corrugated duct sidewall are determined using a naphthalene sublimation technique. The flow visualization technique is used to understand the overall flow structures inside the duct. The corrugation angles of the wavy ducts are 145° and 130°, and the duct aspect ratio is fixed at 7.3. The Reynolds numbers, based on the duct hydraulic diameter, vary from 1,000 to 5,000. The results show that secondary vortex flow cells, called Taylor-Go¨rtler vortices, exist periodically in the wavy duct. Therefore, non-uniform distributions of the heat/mass transfer coefficients are obtained on the duct walls. On the pressure-side wall, high heat/mass transfer cell-shaped regions appear due to the secondary vortex flows for both corrugation angles. On the suction-side wall, the heat transfer coefficients are lower than those on the pressure-side wall. The wavy duct with the corrugation angle of 130° has the stronger strength of the secondary vortex cells resulting in higher heat/mass transfer rates on the duct wall because the sharp turn enhances the development of the secondary flow cells.
5
CUMMINGS, A. "DUCT WALL BREAKOUT: FRIEND OR FOE?" In Autumn Conference Acoustics 2004. Institute of Acoustics, 2023. http://dx.doi.org/10.25144/18035.
6
Shmueli, H., G. Ziskind, and R. Letan. "Forced Convection in a Square Duct With a Wavy Wall." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17353.
Abstract:
In the present study, turbulent flow and heat transfer in a square duct with a heated wavy wall are investigated numerically using the Large Eddy Simulation (LES). A thorough validation of the numerical approach is done versus the existing results for both flat-wall square ducts and wavy-wall channels. It is demonstrated that a very good agreement is achieved with the literature in terms of global and local flow and heat transfer parameters. Heated wavy surfaces of various amplitudes are explored. The results are compared with those for a completely flat duct in terms of the friction factor and Nusselt number. It is shown that the friction factor increases practically linearly with the wave amplitude. On the other hand, the Nusselt number, averaged over the entire duct length, increases more steeply for the relatively small wave amplitude, but almost reaches a plateau for a further increase in the amplitude.
7
Paruchuri, Avinash, Jane Liu, and Stephen Idem. "Comparison of Finite Element Modeling With Measured Deflection of Spiral Flat Oval Duct." In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-68684.
Abstract:
Abstract Deformation was measured as a function of internal static gauge pressure for galvanized steel spiral 12 in. × 43 in. (305 mm × 1092 mm) flat oval ducts. Both unreinforced and externally reinforced ducts were considered. Dial deflection gauges were used to measure the duct deformation at prescribed locations on the top and bottom surface of the test duct and compared to corresponding predictions generated using a nonlinear finite element model that accounted for the self-weight of the duct walls. The Average Wall Thickness (AWT) method was utilized to account for the presence of a continuous spiral seam. Shell elements were employed to represent the thin-walled structure of the ducts. External trapeze reinforcements spaced 3 ft (0.91 m), 6 ft (1.83 m), and 12 ft (3.66 m) apart were modeled using beam elements. The non-linear finite element model of the duct system was found to yield realistic deformation predictions. It was concluded that finite element modeling can be used to guide decisions regarding the selection of a thicker duct wall, or inclusion of either internal or external reinforcement, if concerns exist about excessive duct or reinforcement deformation caused by high internal gauge pressures.
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Paruchuri, Avinash, Jane Liu, and Stephen Idem. "Unreinforced Flat Oval Duct Deformation Testing and Modeling." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23165.
Abstract:
Abstract Unreinforced 12 in. × 23 in. (305 mm × 584 mm) galvanized steel flat oval ducts were tested to measure deformations when internal static gauge pressures were applied. The experiments were performed on spiral seam non-corrugated duct. Finite element models with discrete ring seams and an average wall thickness approach were utilized to represent the continuous spiral seam, and therein predict duct deflections at prescribed locations along the duct wall. Predicted deflections from the finite element models were tabulated and compared to experimental data. Satisfactory agreement between model predictions and test data were obtained from a non-linear finite element analysis that employed a simplified average wall thickness to characterize the spiral seam and duct wall. It is straightforward to implement the average wall thickness methodology in finite element modeling of duct deformation.
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Karakasis, Marios K., Edward M. J. Naylor, Robert J. Miller, and Howard P. Hodson. "The Effect of an Upstream Compressor on a Non-Axisymmetric S-Duct." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23404.
Abstract:
This paper considers the effect of an upstream compressor stage on a compressor inter-spool duct. The duct geometry must be fixed early in the engine design process, well before the design of the upstream stages. It is therefore important that the designer has a good physical insight into how engine representative inlet conditions affect the limits of the duct design space. An experimental and computational investigation of two strutted inter-spool S-ducts was undertaken. Both were tested with and without an upstream stage present. The first duct is of a conventional axisymmetric design with a radius change to length ratio ΔR/L = 0.50. This duct is characteristic of the most extreme ducts considered in modern engine design. The second duct is of a non-axisymmetric design and is 20% shorter, ΔR/L = 0.625. This is well beyond the design limit of axi-symmetric strutted ducts. The paper shows that the presence of the upstream stage increases the duct loss by 54%. The rise in loss occurs on the hub wall and is the result of the incoming stator wakes pooling onto the hub wall, forming a row of contra-rotating streamwise vortex pairs adjacent to the hub wall. These vortices pump boundary layer fluid into the free stream, thus raising the mixing loss. In the non-axisymmetric duct an extra mechanism was observed. The streamwise vortex pairs act to ‘re-energise’ the boundary layer. This reduces strut secondary losses caused by the endwall contouring. The net result is that on the non-axisymmetric duct the presence of an upstream stage only increases the duct loss by 28%. Comparing the two ducts, it is shown that with engine representative inlet conditions, the conventional symmetric duct and 20% shorter non-axisymmetric duct have identical performance. This shows that low loss ducts can be designed which are significantly more extreme than current design limits.
10
Visser, Jan A., and Calvyn B. Coetzer. "A Finite Difference Simulation of the Heat Transfer Enhancement in a Typical Two Pass Ribbed Duct of a Cooled Turbine Blade Using Wall Functions." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-358.
Abstract:
Optimisation of the internal cooling duct of a modern turbine blade, consisting of ribbed and pin finned sections, is essential as the coolant flow introduces losses that need to be minimised. In the ribbed sections large variations in turbulence levels occur and the secondary flows associated with these ribs are responsible for significant local heat transfer variations. This paper presents a finite difference simulation of the friction losses and heat transfer rates in a typical duct with two passes. A standard k-ε turbulence model with wall functions is used as a turbulence closure model. The results show predicted heat transfer enhancement in a typical two pass duct for both smooth walls and a duct with ribs on the top and bottom surfaces. In the case of a smooth duct, predicted and measured results were in good agreement in areas where no recirculation occurred. At the ribbed walls, and in the areas where recirculation occurs, the simulations presented poor results. From the results can be concluded that a wall function based turbulence model does not provide sufficiently accurate results when applied to ribbed ducts and in particular sharp turns.
Reports on the topic "Duct wall":
1
In-depth survey report: partnering to control dust from fiber-cement siding, City Walk, Woodbury, Minnesota. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, April 2014. http://dx.doi.org/10.26616/nioshephb35814a.