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Letteratura scientifica selezionata sul tema "Compression flows"

Autore: Grafiati

Pubblicato: 22 febbraio 2025

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Articoli di riviste sul tema "Compression flows"

Ananin, S. I. "Structure of hydrogen compression plasma flows in a magnetoplasma compressor". Journal of Applied Mechanics and Technical Physics 32, n. 4 (1992): 465–71. http://dx.doi.org/10.1007/bf00851542.

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Chen, Hao, Hui-Jun Tan, Qi-Fan Zhang e Yue Zhang. "Buzz Flows in an External-Compression Inlet with Partially Isentropic Compression". AIAA Journal 55, n. 12 (dicembre 2017): 4286–95. http://dx.doi.org/10.2514/1.j056066.

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Ho, Yung-Han, Chih-Chun Chan, Wen-Hsiao Peng, Hsueh-Ming Hang e Marek Domanski. "ANFIC: Image Compression Using Augmented Normalizing Flows". IEEE Open Journal of Circuits and Systems 2 (2021): 613–26. http://dx.doi.org/10.1109/ojcas.2021.3123201.

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Rudy, David H., James L. Thomas, Ajay Kumar, Peter A. Gnoffo e Sukumar R. Chakravarthy. "Computation of laminar hypersonic compression-corner flows". AIAA Journal 29, n. 7 (luglio 1991): 1108–13. http://dx.doi.org/10.2514/3.10710.

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Astashynski, V. M., E. A. Kostyukevich, A. M. Kuzmitski, A. A. Mishchuk e P. N. Shoronov. "Interaction between oppositely directed compression plasma flows". Journal of Applied Spectroscopy 79, n. 4 (settembre 2012): 610–15. http://dx.doi.org/10.1007/s10812-012-9647-6.

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Tang, Chuanbo, Xihua Sheng, Zhuoyuan Li, Haotian Zhang, Li Li e Dong Liu. "Offline and Online Optical Flow Enhancement for Deep Video Compression". Proceedings of the AAAI Conference on Artificial Intelligence 38, n. 6 (24 marzo 2024): 5118–26. http://dx.doi.org/10.1609/aaai.v38i6.28317.

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Video compression relies heavily on exploiting the temporal redundancy between video frames, which is usually achieved by estimating and using the motion information. The motion information is represented as optical flows in most of the existing deep video compression networks. Indeed, these networks often adopt pre-trained optical flow estimation networks for motion estimation. The optical flows, however, may be less suitable for video compression due to the following two factors. First, the optical flow estimation networks were trained to perform inter-frame prediction as accurately as possible, but the optical flows themselves may cost too many bits to encode. Second, the optical flow estimation networks were trained on synthetic data, and may not generalize well enough to real-world videos. We address the twofold limitations by enhancing the optical flows in two stages: offline and online. In the offline stage, we fine-tune a trained optical flow estimation network with the motion information provided by a traditional (non-deep) video compression scheme, e.g. H.266/VVC, as we believe the motion information of H.266/VVC achieves a better rate-distortion trade-off. In the online stage, we further optimize the latent features of the optical flows with a gradient descent-based algorithm for the video to be compressed, so as to enhance the adaptivity of the optical flows. We conduct experiments on two state-of-the-art deep video compression schemes, DCVC and DCVC-DC. Experimental results demonstrate that the proposed offline and online enhancement together achieves on average 13.4% bitrate saving for DCVC and 4.1% bitrate saving for DCVC-DC on the tested videos, without increasing the model or computational complexity of the decoder side.

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Kang, Hyun-Su, Sung-Yeon Kim e Youn-Jea Kim. "Wet Compression Study for an Aero-Thermodynamic Performance Analysis of a Centrifugal Compressor at Design and Off-Design Points". Processes 10, n. 5 (9 maggio 2022): 936. http://dx.doi.org/10.3390/pr10050936.

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In this study, to analyze the effect of wet compression technology on the aero-thermodynamic performance of a centrifugal compressor, a numerical analysis study was conducted on the design point and off-design point. Wet compression technology sprays water droplets at the inlet of the compressor. During the compression process, water droplets evaporate, reducing the heat of compression and reducing the compression work, which improves the efficiency of the compressor. In wet compression technology, detailed research is needed for the application to compressors because the droplet behavior affects the internal flow. The main parameters for wet compression technology are the droplet size and injection rate selection, and the flow inside the compressor changed by the droplet behavior was analyzed. When the droplet size and injection rate were changed at the design point and the off-design point, it was confirmed that a small droplet size was effective in both areas, and it was confirmed that the performance improved as the flow rate increased. The internal flow changed greatly depending on the size of the droplet. As a result, the centrifugal compressor to which the wet compression technology was applied had a lower outlet temperature than dry compression at both the design point and the off-design point and had increases in the pressure ratio and efficiency. However, the surge margin decreased by about 2% in the surge region. The reason is that due to high-speed rotation, particles move in the outer diameter direction and are driven into a tip-leakage flow, and many stagnant flows occur without flowing into the main flow. Through the study results, it was possible to understand the effects of wet compression technology on the performance and efficiency increase of centrifugal compressors and the effects of particle behavior on the internal flow of the compressor at the off-design point.

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Neuschwander, T. B., B. R. Macias, A. R. Hargens e Q. Zhang. "Mild External Compression of the Leg Increases Skin and Muscle Microvascular Blood Flow and Muscle Oxygenation during Simulated Venous Hypertension". ISRN Vascular Medicine 2012 (10 dicembre 2012): 1–6. http://dx.doi.org/10.5402/2012/930913.

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We studied the effect of mild external leg compression on both skin and muscle microvascular flow, and muscle oxygenation in the leg of healthy subjects during simulated venous hypertension. Skin and muscle microvascular blood flows were measured using photoplethysmography (PPG), and muscle oxygenation was measured using near-infrared spectroscopy (NIRS). Both PPG and NIRS probes were placed over the anterior compartment of the right leg in 8 healthy subjects. Measurements were taken under three experimental conditions: external leg compression (40 mmHg); simulated venous hypertension (65 mmHg thigh cuff); external leg compression during simulated venous hypertension. Muscle oxygenation was measured only under external leg compression during simulated venous hypertension. Simulated venous hypertension decreased skin and muscle microvascular blood flows from 100% (baseline) to 35.8±2.9% and 31.9±1.3% (P<0.001), respectively. External leg compression during simulated venous hypertension caused 2-fold increases in both skin and muscle microvascular blood flows compared to simulated venous hypertension (P<0.001). Similarly, external leg compression during simulated venous hypertension significantly restored muscle oxygenation by 23±7% compared to its baseline (P<0.05). Our results demonstrate that mild external leg compression counteracts the decreases in skin microvascular flow, muscle microvascular flow, and muscle oxygenation induced by simulated venous hypertension in the leg.

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Lea, C. J., e A. P. Watkins. "Differential stress modelling of turbulent flows in model reciprocating engines". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 211, n. 1 (1 gennaio 1997): 59–77. http://dx.doi.org/10.1243/0954407971526227.

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A study is made here of the application of a differential stress model (DSM) of turbulence to flows in two model reciprocating engines. For the first time this study includes compressive effects. An assessment between DSM and k-ɛ results is made comparing with laser Doppler anemometry experimental data of the mean flow and turbulence intensity levels during intake and compression strokes. A well-established two-dimensional finite-volume computer code is employed. Two discretization schemes are used, namely the HYBRID scheme and the QUICK scheme. The latter is found to be essential if differentiation is to be made between the turbulence models. During the intake stroke the DSM results are, in general, similar to the k-ɛ results in comparison to the experimental data, except for the turbulence levels, which the DSM seriously underpredicts. This is in contrast to a parallel set of calculations of steady in-flow, which showed significant gains from using the DSM, particularly at the turbulence field level. The increased number of grid lines employed in those calculations contribute to this apparent difference between steady and unsteady flows, but cycle- to-cycle variations are more likely to be the primary cause, resulting in too high levels of turbulence intensity being measured. However, during the compression stroke the DSM returns vastly superior results to the k-ɛ model at both the mean flow and turbulence intensity levels. This is because the DSM generates an anisotropic shear stress field during the early stages of compression that suppresses the main vortical structure, in line with the experimental data.

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Genbach, A. A., e D. Y. Bondartsev. "An Analysis of Heat Exchange Crisis in the Capillary Porous System for Cooling Parts of Heat and Power Units". Proceedings of Higher Educational Institutions. Маchine Building, n. 12 (717) (dicembre 2019): 21–35. http://dx.doi.org/10.18698/0536-1044-2019-12-21-35.

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A model of dynamics of the vapor bubbles that emerge on solid surfaces of porous structures and the steam generating wall (bottom layer) is presented in this work. The model was filmed and photographed by a high-speed camera SKS-1М. The discharge of high heat flows (up to 2·106 W/m2) was maintained by the joint action of capillary and mass forces with the help of intensifiers. An analytical model was developed based on the theory of thermoelasticity. The limit state of the porous coating with poor thermal conductivity and the metal bottom layer was determined. Heat flows were calculated from the spontaneous birth of the vapour nucleus (10–8) to the material destruction (102–103 s), thus the interval from the process of relaxation to the maximum process (destruction) was described. The size of the pullout particles determined in the model at the moment of porous coating destruction showed good congruence with the experimental data obtained at the optic stand. The destruction of coating under the compression forces occurs much earlier than the tension forces. It is probable that the destruction will happen under the impact of the compression and shear forces. The intervals of the heat flow when such destruction takes place are different for quartz and granite coating. Each thickness of the pullout particles under the impact of compression forces has its limit values of the heat flows, which are located within the mentioned intervals. As the specific heat flow in the heated layer increases and, therefore, the heating time decreases, the impact of the compression stresses increases as well. Despite the high resistance to compression, destruction from the compressive heat tension occurs in more favorable conditions immediately, and in diminutive volumes. Experimental testing units, test conditions, the outcome of the heat exchange crisis, the limit state of the surface and the calculation of critical heat flows are presented. The capillary porous system that works under the joint action of capillary and mass forces is studied. The system has advantages compared to pool boiling, thin-film evaporators and heat pipes.

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Più fonti

Tesi sul tema "Compression flows"

Petukhou, Yu A., V. V. Uglov, N. T. Kvasov, A. V. Punko, I. L. Doroshevich, V. M. Astashynski e A. M. Kuzmitski. "Formation of silicon-based nanostructures by compression plasma flows". Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20860.

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The use of compression flows (CPF) for the formation of metal and silicide nanostructures for data storage devices, thermoelectric materials and solar cells is presented. The action of CPF with injected metallic powder results in the formation of coatings composed of spherical clusters with complex structure: each submicron cluster (0,1-0,2 μm radius) is formed from a number of nanosized ones (10-25 nm radius). The action of CPF on binary “metal-silicon” systems provides formation of branched silicon dendrites (tip radius ~ 200 nm, primary spacing ~ 1,2 μm); interdendritic space is filled with nanostructured (50-100 nm) “silicide-silicon” and “monosilicide-disilicide” composite due to melting of the surface layer, rapid solidification (~ 10-3 m/s) and constitutional overcooling. Mechanisms of formation of nanostructured composites on silicon surface and in thick surface layers is discussed in terms of order parameter evolution and non-equilibrium solidification models. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20860

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Söder, Martin. "Numerical Investigation of Internal Combustion Engine Related Flows". Licentiate thesis, KTH, Strömningsfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-124237.

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Internal combustion engines has been used for more than 100 years. The use of the abundant energy supply stored as hydrocarbon fueled unprecedented economic growth. The use of hydrocarbons increased the work output of human labor significantly, thus increasing the economy and prosperity. However, during the latter part of the twentieth century negative consequences of the internal combustion engine has been noticed. Initially the being emissions of local pollutants such as carbon monoxide, nitrogen oxides and unburnt hydrocarbons. These pollutants have to this day in the western world been reduced significantly and further reductions are under way. Thereafter, has the focus been shifted somewhat to global emissions such as carbon dioxide due to the effect on the climate. However, as the most accessible oil resources have been exhausted the price of oil has five folded since the turn of the century, straining the exponential economic growth enjoyed for two centuries. Heavy duty diesel engine efficiency is still below 50\%, there is thus a need and a possibility to further increase engine efficiency. In this thesis, work has been done to increase the understanding of the flow prior to combustion. A better knowledge of pre-combustion in-cylinder flow would increase the possibility to reduce engine emissions and fuel consumption, through better mixing and lower heat transfer. The work presented is ordered in such a way that the flow structures created during the intake is presented first. Thereafter, the effect of compression is investigated. Intake flow structures are studied using Large-Eddy Simulations (LES) and experiments on a steady swirl test rig. The effects of compression are studied using simulations of predefined flow structures undergoing compression. It is found that the flow structures created during intake is qualitatively different depending of intake valve lift. And that a single Swirl Number (SN) is an insufficient quantity to characterize the flow created at low valve lifts, due to high fluctuations. During compression it is found that a high swirl number suppress small scale turbulence while the compression has an increasing effect of axial fluctuations due to vorticity-dilation interaction. Additionally, it is shown that turbulent kinetic energy is introduced in the flow field by the piston in the absence of tumble breakdown.

QC 20130704

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Aziz, Saduman. "Perfect Gas Navier-stokes Solutions Of Hypersonic Boundary Layer And Compression Corner Flows". Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606661/index.pdf.

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The purpose of this thesis is to perform numerical solutions of hypersonic, high temperature, perfect gas flows over various geometries. Three dimensional, thin layer, compressible, Navier-Stokes equations are solved. An upwind finite difference approach with Lower Upper-Alternating Direction Implicit (LU-ADI) decomposition is used. Solutions of laminar, hypersonic, high temperature, perfect gas flows over flat plate and compression corners (qw=5°
, 10°
, 14°
, 15°
, 16°
, 18°
and 24°
) with eight different free-stream and wall conditions are presented and discussed. During the analysis, air viscosity is calculated from the Sutherland formula up to 1000°
K, for the temperature range between 1000 º
K and 5000 º
K a curve fit to the estimations of Svehla is applied. The effects of Tw/T0 on heat transfer rates, surface pressure distributions and boundary layer characteristics are studied. The effects of corner angle (&
#952
w) on strong shock wave/boundary layer interactions with extended separated regions are investigated. The obtained results are compared with the available experimental data, computational results, and theory.

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Zidi, Koceila. "Écoulement d'une suspension de particules en compression". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST197.

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L'étude des suspensions de particules est cruciale en raison de leur omniprésence dans divers domaines industriels et naturels. Comprendre leur comportement permet d'améliorer des procédés tels que la fabrication de matériaux composites, le traitement des eaux et l'étude des sédiments et des sols. Au cours des deux dernières décennies, la rhéologie des suspensions de particules a été largement étudiée en écoulements de cisaillement simple. Les expériences ont montré que la viscosité effective d'une suspension isodense et non-brownienne augmente avec la fraction volumique en particules. La question posée dans ma thèse est de savoir si les lois rhéologiques permettent de décrire le comportement des suspensions de particules dans des configurations plus complexes comme des écoulements de compression. Nous avons étudié expérimentalement le comportement des suspensions dans deux configurations d'écoulement de compression. Dans la première configuration, la suspension est comprimée entre un disque mobile s'approchant à vitesse imposée vers une paroi verticale. Des mesures locales de pression ont été réalisées, en faisant varier la fraction volumique de la suspension et la vitesse de compression. Un cadre théorique a été établi permettant de relier la différence de pression radiale dans l'écoulement de compression à la viscosité effective de la suspension et donc de la mesurer indirectement. Nous avons montré que la viscosité effective déduite par cette approche dans un écoulement de compression est identique à celle mesurée dans une configuration classique de cisaillement simple. Dans la deuxième configuration, la suspension est comprimée entre une sphère qui sédimente sous l'effet de son propre poids vers une paroi horizontale. Des mesures de vitesse de sédimentation de la sphère ont été réalisées. L'influence des paramètres de la suspension, tels que le diamètre et la concentration des particules, ainsi que des paramètres géométriques, comme le rayon de la sphère et la largeur du réservoir, a été étudiée. Dans la région loin de la paroi, le principe fondamental de la dynamique nous a permis de prédire la vitesse de sédimentation de la sphère et d'en déduire la viscosité effective de la suspension, qui correspond à celle du cisaillement simple. Nous avons montré que la suspension se comporte comme un fluide effectif newtonien. La dynamique d'approche de la sphère dans la suspension s'écarte de celle qu'elle aurait dans un fluide newtonien. Proche de la paroi, on applique la théorie de lubrification. Cette théorie prédit que la vitesse de sédimentation de la sphère évolue linéairement avec la distance par rapport à la paroi horizontale, avec une vitesse nulle au contact avec la paroi. Dans le cas de la suspension, la vitesse de sédimentation de la sphère évolue de manière non linéaire avec la distance à la paroi. Nous avons également mesuré une vitesse d'impact de la sphère non nulle avec la paroi. Nous avons proposé une relation empirique pour la vitesse d'approche qui permet de regrouper toutes les données expérimentales sur une courbe unique dans toute la gamme des paramètres étudiés
The study of particle suspensions is crucial due to their omnipresence in various industrial and natural domains. Understanding their behavior enables us to improve processes such as the manufacture of composite materials, water treatment and the study of sediments and soils. Over the past two decades, the rheology of particle suspensions has been extensively studied in simple shear flows. Experiments have shown that the effective viscosity of an isodense, non-Brownian suspension increases with the particle volume fraction. The question posed in my thesis is whether rheological laws can be used to describe the behavior of particle suspensions in more complex configurations such as compression flows. We have experimentally investigated the behavior of suspensions in two compression flow configurations. In the first configuration, the suspension is compressed between a moving disk approaching a vertical wall at an imposed velocity. Local pressure measurements were carried out, varying the volume fraction of the suspension and the compression velocity. A theoretical framework was established, enabling the radial pressure difference in the compression flow to be related to the effective viscosity of the suspension, and thus measured indirectly. We have shown that the effective viscosity deduced by this approach in compression flow is identical to that measured in a conventional simple shear configuration. In the second configuration, the suspension is compressed between a sphere sedimenting under its own weight towards a horizontal wall. Sedimentation velocity measurements of the sphere were carried out. The influence of suspension parameters, such as particle diameter and concentration, as well as geometric parameters, such as sphere radius and reservoir width, was investigated. In the region far from the wall, the fundamental principle of dynamics enabled us to predict the sedimentation velocity of the sphere and deduce the effective viscosity of the suspension, which corresponds to that of simple shear. We have shown that the suspension behaves like an effective Newtonian fluid. The approach dynamics of the sphere in the suspension deviate from those it would have in a Newtonian fluid. Close to the wall, lubrication theory is applied. This theory predicts that the sedimentation velocity of the sphere evolves linearly with distance from the horizontal wall, with zero velocity at contact with the wall. In the case of suspension, the sedimentation velocity of the sphere evolves non-linearly with distance from the wall. We also measured a non-zero impact velocity of the sphere with the wall. We have proposed an empirical relationship for the approach velocity that allows all the experimental data to be grouped on a single curve across the entire range of parameters studied

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Stapleton, Brian J. "An investigation of in-cylinder flows in a direct injection compression ignition engine using particle image velocimetry". Thesis, Loughborough University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529505.

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Söder, Martin. "Creation and destruction of in-cylinder flows : Large eddy simulations of the intake and the compression strokes". Doctoral thesis, KTH, Strömningsfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-164889.

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The aim of this thesis is to increase engine efficiency by studying the flow structures created in an engine cylinder during the intake phase and the effect of the subsequent compression. The invention of the combustion engine has enabled three centuries of economic growth fueled by energy stored as hydrocarbons. However, during the latter part of the twentieth century negative consequences on health and environment of the combustion engine were observed. In order to reduce emissions without increasing fuel consumption, improved knowledge of all physical processes occurring in the engine are necessary. The aim of this thesis is to increase the understanding of the flow prior to combustion, which can lead to reduced engine emissions and fuel consumption. Intake flow structures are studied using large eddy simulations and experiments on a steady swirl test rig. Flow acceleration was observed to reduce the swirl coefficient, and higher swirl coefficient was found during valve closing as compared to during valve opening. This implies that the rotation is stronger during the later part of the intake then what has been previously assumed. In addition, the computations show that the volume above the valves has a profound effect on the swirl created during the intake. To take this into account a novel way of calculating the swirl number was suggested. This approach gives a lower swirl number as compared to the commonly used Thien methodology. The effects of compression are studied using simulations of predefined flow structures undergoing compression. The peak turbulence levels were found to be increasing with tumble number and decreasing with swirl. It was noted that compression increased the turbulent fluctuations in the cylinder axis leading to anisotropic turbulence and that a small tilt angle was observed to have a significant effect on swirl homogeneity at top dead center. In this thesis, a new methodology was proposed and validated for calculation of in-cylinder turbulence for a flat piston. The results of the thesis enhance the understanding of the dynamic effects encountered during intake as well recognizing that a small tumble component has a strong effect on the flow structures prior to combustion. These results can be used to improve the simplified computational methods used to optimize the engine.

QC 20150420

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Legrand, Nicolas. "Numerical and modeling methods for multi-level large eddy simulations of turbulent flows in complex geometries". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMIR16/document.

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La simulation aux grandes échelles est devenue un outil d’analyse incontournable pour l’étude des écoulements turbulents dans des géométries complexes. Cependant, à cause de l’augmentation constante des ressources de calcul, le traitement des grandes quantités de données générées par les simulations hautement résolues est devenu un véritable défi qu’il n’est plus possible de relever avec des outils traditionnels. En mécanique des fluides numérique, cette problématique émergente soulève les mêmes questions que celles communément rencontrées en informatique avec des données massives. A ce sujet, certaines méthodes ont déjà été développées telles que le partitionnement et l’ordonnancement des données ou bien encore le traitement en parallèle mais restent insuffisantes pour les simulations numériques modernes. Ainsi, l’objectif de cette thèse est de proposer de nouveaux formalismes permettant de contourner le problème de volume de données en vue des futurs calculs exaflopiques que l’informatique devrait atteindre en 2020. A cette fin, une méthode massivement parallèle de co-traitement, adaptée au formalisme non-structuré, a été développée afin d’extraire les grandes structures des écoulements turbulents. Son principe consiste à introduire une série de grilles de plus en plus grossières réduisant ainsi la quantité de données à traiter tout en gardant intactes les structures cohérentes d’intérêt. Les données sont transférées d’une grille à une autre grâce à l’utilisation de filtres et de méthodes d’interpolation d’ordre élevé. L’efficacité de cette méthodologie a pu être démontrée en appliquant des techniques de décomposition modale lors de la simulation 3D d’une pale de turbine turbulente sur une grille de plusieurs milliards d’éléments. En outre, cette capacité à pouvoir gérer plusieurs niveaux de grilles au sein d’une simulation a été utilisée par la suite pour la mise en place de calculs basés sur une stratégie multi-niveaux. L’objectif de cette méthode est d’évaluer au cours du calcul les erreurs numériques et celles liées à la modélisation en simulant simultanément la même configuration pour deux résolutions différentes. Cette estimation de l’erreur est précieuse car elle permet de générer des grilles optimisées à travers la construction d’une mesure objective de la qualité des grilles. Ainsi, cette méthodologie de multi-résolution tente de limiter le coût de calcul de la simulation en minimisant les erreurs de modélisation en sous-maille, et a été appliquée avec succès à la simulation d’un écoulement turbulent autour d’un cylindre
Large-Eddy Simulation (LES) has become a major tool for the analysis of highly turbulent flows in complex geometries. However, due to the steadily increase of computational resources, the amount of data generated by well-resolved numerical simulations is such that it has become very challenging to manage them with traditional data processing tools. In Computational Fluid Dynamics (CFD), this emerging problematic leads to the same "Big Data" challenges as in the computer science field. Some techniques have already been developed such as data partitioning and ordering or parallel processing but still remain insufficient for modern numerical simulations. Hence, the objective of this work is to propose new processing formalisms to circumvent the data volume issue for the future 2020 exa-scale computing objectives. To this aim, a massively parallel co-processing method, suited for complex geometries, was developed in order to extract large-scale features in turbulent flows. The principle of the method is to introduce a series of coarser nested grids to reduce the amount of data while keeping the large scales of interest. Data is transferred from one grid level to another using high-order filters and accurate interpolation techniques. This method enabled to apply modal decomposition techniques to a billion-cell LES of a 3D turbulent turbine blade, thus demonstrating its effectiveness. The capability of performing calculations on several embedded grid levels was then used to devise the multi-resolution LES (MR-LES). The aim of the method is to evaluate the modeling and numerical errors during an LES by conducting the same simulation on two different mesh resolutions, simultaneously. This error estimation is highly valuable as it allows to generate optimal grids through the building of an objective grid quality measure. MR-LES intents to limit the computational cost of the simulation while minimizing the sub-grid scale modeling errors. This novel framework was applied successfully to the simulation of a turbulent flow around a 3D cylinder

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Beevers, A. "Transition Modelling for Axial Compressor Flows". Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/3479.

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Abstract The application of Menter's transition model (Menter et al. (2004a), here-after known as the ץ - θ model) available in the CFX CFD code, for use within an axial compressor design group was studied. Simulations of a range of turbomachinery applicable test cases were undertaken, including a range of transitional flat plates and a 2D compressor cascade. Results were com¬pared to experimental data and the results of simulations performed with standard turbulence models. The ץ - θ model significantly improved the prediction of the boundary layer development, compared to the turbulence models. Comparisons with ex¬perimental data were also good. Features such as mid-chord transitional separation bubbles were predicted with the ץ - θ model, but not with the turbulence models. The ץ - θ model offered no consistent improved accuracy over the κ - ω SST turbulence model when predicting leading edge separa¬tion bubbles. The more accurate simulation of the boundary layer enables a closer prediction of viscous losses. 2D and 3D unsteady simulations of a low-speed axial compressor stator blade boundary layer, subject to impinging rotor wakes, were conducted. The pur¬pose was to determine the performance of the ץ - θ model in this environment, as there is no available literature for this. For both simulations, the model gave a good qualitative agreement to experimental data in the prediction of passing rotor wake effects on the suction surface. The effects on the pressure surface transition region due to wake passing were poorly predicted. All models were simulated on low and high-speed axial compressor stages. Results showed no improvement over the turbulence models of the ץ - θ model to predict blade exit parameters. The ץ - θ model does not present a significant enough improvement in the prediction of the flow to warrant its regular use in the design of axial compressor blading. However, it presents a useful tool in the development of high lift compressor blading.

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South, Andrew Hartmut. "Low-flow compressor performance". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627299.

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Gabrielsson, Gustav. "Tissue Compression Flossing - A systematic review". Thesis, Linnéuniversitetet, Institutionen för idrottsvetenskap (ID), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-104249.

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Background: Compression Tissue Flossing (CTF) is getting more and more popular. However, it is still unclear about the usability and function of CTF. Objective: The main objective was to investigate the current evidence on the function and usability of CTF by doing a systematic review. Methods: A PRISMA checklist was used to write this systematic review. Inclusion criteria; studies that examined CTF and its different effects published 2013-2021. The exclusion criteria were studies that were not published in English. The information sources used in this systematic review was done on PubMed and EBSCO (MEDLINE, CINAHL, SPORTDiscus) and as hand research. The methodological quality was assessed using the Physiotherapy Evidence Database scale and the AMSTAR. The method used to present the results is by organized tables where the study results are shown. Results: A total of 25 articles was included in the review. A total of 509 participants (mean age 22,6) was included. The average physiotherapy database score was 56% (range= 18,1%-81,8%). 15 studies were considered as high quality, 10 as low quality. Compression Tissue Flossing showed many different significant effects as increased range of motion, countermovement jump, rate of force development, increased torque, jump height, jump velocity, reduced muscle contraction time, and perception of flexibility. Conclusions: The results of this study suggest that compression tissue flossing has a good potential to be used in different contexts of sports performance/medicine. More studies are needed to validate the use of different floss bands and use them in bigger epidemiological settings as it right now seems to lack in its consistency depending on the pressure and application.

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Più fonti

Libri sul tema "Compression flows"

H, Anderson Bernhard, Shaw Robert J. 1946- e United States. National Aeronautics and Space Administration., a cura di. Numerical simulation of supersonic compression corners and hypersonic inlet flows using the RPLUS2D code. [Washington, DC]: National Aeronautics and Space Administration, 1994.

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Center, Ames Research, a cura di. Steady secondary flows generated by periodic compression and expansion of an ideal gas in a pulse tube. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1999.

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B, Roebuck, e National Physical Laboratory (Great Britain), a cura di. Measuring flow stress in hot axisymmetric compression tests. Teddington: NPL, 1997.

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Neuhoff, F. Modifications to the inlet flow field of a transonic compressor rotor. Monterey, Calif: Naval Postgraduate School, 1985.

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Stalker, R. J. Thermodynamics and wave processes in high Mach number propulsive ducts. Washington: AIAA, 1989.

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1936-, Kawamura Takaichi, Bencze Daniel P e Ames Research Center, a cura di. Calculation of external-internal flow fields for mixed-compression inlets. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1987.

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Center, Ames Research, a cura di. Computations of unsteady multistage compressor flows in a workstation environment. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1992.

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S, Prahst P., e United States. National Aeronautics and Space Administration., a cura di. Inlet flow test calibration for a small axial compressor facility. [Washington, DC]: National Aeronautics and Space Administration, 1994.

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United States. National Aeronautics and Space Administration., a cura di. Blockage development in a transonic, axial compressor rotor. [Washington, D.C: National Aeronautics and Space Administration, 1997.

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Capitoli di libri sul tema "Compression flows"

Zeman, O., e G. N. Coleman. "Compressible Turbulence Subjected to Shear and Rapid Compression". In Turbulent Shear Flows 8, 283–96. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-77674-8_20.

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Leyland, P. "2D Hypersonic Viscous Flow over Compression Ramps". In Hypersonic Flows for Reentry Problems, 407–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77922-0_39.

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Haase, Werner. "Computational Results for Flows Over Compression Ramps". In Hypersonic Flows for Reentry Problems, 268–84. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76527-8_23.

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Leyland, Pénélope, Roland Richter e Tristan Neve. "High Speed Flows Over Compression Ramps". In Proceedings of the Ninth GAMM-Conference on Numerical Methods in Fluid Mechanics, 223–36. Wiesbaden: Vieweg+Teubner Verlag, 1992. http://dx.doi.org/10.1007/978-3-663-13974-4_22.

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Haase, Werner. "Viscous, Hypersonic Flows Over Compression Ramps". In Proceedings of the Eighth GAMM-Conference on Numerical Methods in Fluid Mechanics, 189–200. Wiesbaden: Vieweg+Teubner Verlag, 1990. http://dx.doi.org/10.1007/978-3-663-13975-1_20.

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Caughan, Frances Mc. "Dynamic Modelling of Axial Flow Compression Systems". In Instabilities and Turbulence in Engineering Flows, 151–71. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1743-2_8.

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Alsalihi, Zuheyr, e Herman Deconinck. "Viscous, 2-D, Laminar Hypersonic Flows Over Compression Ramps". In Hypersonic Flows for Reentry Problems, 152–66. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76527-8_15.

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Coleman, G. N., e N. N. Mansour. "Simulation and Modeling of Homogeneous Compressible Turbulence Under Isotropic Mean Compression". In Turbulent Shear Flows 8, 269–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-77674-8_19.

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Srinivas, K. "Computation of Hypersonic Flow Past a Compression Corner by a Spatial Marching Scheme". In Hypersonic Flows for Reentry Problems, 338–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77922-0_34.

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Ho, Yung-Han, Chih-Peng Chang, Peng-Yu Chen, Alessandro Gnutti e Wen-Hsiao Peng. "CANF-VC: Conditional Augmented Normalizing Flows for Video Compression". In Lecture Notes in Computer Science, 207–23. Cham: Springer Nature Switzerland, 2022. http://dx.doi.org/10.1007/978-3-031-19787-1_12.

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Atti di convegni sul tema "Compression flows"

Ravindran, S. S. "Artificial Compression POD Reduced Order Model for Control of MHD Flows". In 2024 American Control Conference (ACC), 3302–7. IEEE, 2024. http://dx.doi.org/10.23919/acc60939.2024.10644402.

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Wang, Jia, e Xiaolin Wu. "Information Flows in Video Coding". In 2010 Data Compression Conference. IEEE, 2010. http://dx.doi.org/10.1109/dcc.2010.21.

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Zheng, Qun, Yan Shao e Yinyong Zhang. "Numerical Simulation of Aerodynamic Performances of Wet Compression Compressor Cascade". In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-91125.

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The thermodynamic analyses and actual applications of wet compression have demonstrated its benefits for power augment. An aerodynamic flow field simulation of the wet compression compressor cascade can give more information about the cascade internal flow patterns. In this paper, a stage of wet compression compressor is simulated with computational fluid dynamics software. Three dimensional, two phases flows are numerically investigated under different water injected amount, different water droplet diameter etc. The CFD results present the details of wet compression compressor cascade flows. And the flow fields of wet compression are compared with those of dry compression.

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CHAMPNEY, J. "Modeling of turbulence for compression corner flows and internal flows". In 25th Joint Propulsion Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1989. http://dx.doi.org/10.2514/6.1989-2344.

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Dogrusoz, Saduman, Mehmet Kavsaoglu e Unver Kaynak. "Numerical solution of hypersonic compression corner flows". In 10th AIAA/NAL-NASDA-ISAS International Space Planes and Hypersonic Systems and Technologies Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2001. http://dx.doi.org/10.2514/6.2001-1750.

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Sardari, Mohsen, Ahmad Beirami e Faramarz Fekri. "Memory-assisted universal compression of network flows". In IEEE INFOCOM 2012 - IEEE Conference on Computer Communications. IEEE, 2012. http://dx.doi.org/10.1109/infcom.2012.6195842.

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Gerin-Roze, J., Mark Elert, Michael D. Furnish, Ricky Chau, Neil Holmes e Jeffrey Nguyen. "SELF-SIMILAR COMPRESSION FLOWS IN SPHERICAL GEOMETRY". In SHOCK COMPRESSION OF CONDENSED MATTER - 2007: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter. AIP, 2008. http://dx.doi.org/10.1063/1.2832992.

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Windsheimer, Marc, Fabian Brand e André Kaup. "Multiscale Augmented Normalizing Flows for Image Compression". In ICASSP 2024 - 2024 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). IEEE, 2024. http://dx.doi.org/10.1109/icassp48485.2024.10446147.

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Heuzé, Olivier, Mark Elert, Michael D. Furnish, William W. Anderson, William G. Proud e William T. Butler. "ANALYTICAL SOLUTION FOR ISENTROPIC FLOWS IN SOLIDS". In SHOCK COMPRESSION OF CONDENSED MATTER 2009: Proceedings of the American Physical Society Topical Group on Shock Compression of Condensed Matter. AIP, 2009. http://dx.doi.org/10.1063/1.3295139.

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Sun, Lanxin, Yijin Li, Qun Zheng e Rakesh Bhargava. "The Effects of Wet Compression on the Separated Flow in a Compressor Stage". In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50920.

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Effects of wet compression on the flow field within a compressor stage, particularly in presence of the separated flow region are not fully understood. Numerical simulations of 3D compressible separated flows within a wet compression compressor stage are carried out using a Computational Fluid Dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry compression. Under different operating conditions and with wet compression, this study presents the changes in the extent of separated region on the flow channel surfaces, compression efficiency, pressure ratio and specific compression work etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated.

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Rapporti di organizzazioni sul tema "Compression flows"

Hawley e Thorson. PR-015-13606-R01 Ultrasonic Meter Performance in Liquid Transients. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), giugno 2014. http://dx.doi.org/10.55274/r0010846.

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This research evaluated the performance of select ultrasonic meters in natural gas flows before, during, and after transient liquid contamination from compressor oil and glycol. The research program evaluated the performance recovery characteristics of each ultrasonic meter after an extended period of dry gas flow and after meter cleaning. The diagnostics of the meters were also monitored to determine if they could be used to determine the presence of liquid contamination.

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George e Hawley. PR-015-12600-R01 Ability of Ultrasonic Meters to Measure Accurately in Compressor-Induced Pulsating Flows. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), novembre 2013. http://dx.doi.org/10.55274/r0010808.

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Transmission and storage operations frequently move natural gas using reciprocating compressors that may generate flow pulsations. Most measurement systems cannot accurately measure the flow rate of a pulsating gas stream, and the resulting errors can cause inaccurate gas volumes and accounting imbalances. Recent advances in ultrasonic meters may provide the ability to function without measurement error in pulsating gas streams. Tests were performed to examine the relationship between ultrasonic meter transducer sampling rates, the frequency and amplitude of pulsations from reciprocating compressors, and meter accuracy as a possible basis for using ultrasonic meters in gas pipelines with varying pulsations. Two ultrasonic natural gas meters of current design were tested at SwRI in flows that simulated reciprocating compressor pulsations. Diagnostics and flow data were collected from the meters and analyzed to identify pulsation conditions in which the meters read accurately, or in which meter data could be used to correct measurement errors.

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Car, David, e Steven L. Puterbaugh. Fluid Mechanics of Compression System Flow Control. Fort Belvoir, VA: Defense Technical Information Center, luglio 2005. http://dx.doi.org/10.21236/ada444617.

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Lagus, P. L., e B. S. Flanagan. PR-197-723-R01 Compressor Flow Measurements. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), agosto 1988. http://dx.doi.org/10.55274/r0011964.

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The objective of the proposed research was to demonstrate the viability and utility of a constant flow tracer dilution technique for inferring the flowrate through a high-pressure natural gas centrifugal compressor. Testing was performed by injecting a known flowrate of tracer gas, sulfur hexafluoride(SF6), into a natural gas stream immediately upstream of an operating centrifugal compressor. Measurements of the diluted tracer gas concentration downstream of the compressor were made by means of electron capture gas chromatography. Knowledge of the injection concentration and injection flowrate coupled with the downstream diluted concentration and compressor operating characteristics allowed the inference of the actual flow through the compressor. Tracer inferred flowrates were then compared to flowrates measured by a custody transfer station downstream of the compressor station.

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George. PR-015-13603-R01 Meter Station Design Procedures to Minimize Pipe Flow-Induced Pulsation Error. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), ottobre 2013. http://dx.doi.org/10.55274/r0010099.

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This project explored the sources of flow-induced pulsations in natural gas meter stations and the detrimental effects the pulsations have on the measurement capabilities of three types of gas custody transfer meters: orifice meters, turbine meters, and ultrasonic meters. To supplement the PRCI-funded research on the effect of compressor pulsations on ultrasonic flow measurement, Southwest Research Institute (SwRI) has performed a study to identify best practices for meter station piping design that avoid generating or amplifying flow-induced pulsations. This study involved a literature review to identify features of meter station piping that (1) generate pulsations independently of compressors or (2) amplify pulsating flows entering station piping. Where possible, the study also worked to quantify the effect of flow-induced pulsations on meter accuracy. This information has been used to create best practices and methodologies for minimizing metering errors caused by pulsation. As a result of this research, various design techniques able to reduce or eliminate pulsations in meter station piping systems have been compiled. Mitigation practices specific to obstructions, flow restrictions, piping geometries, gaps, acoustically-induced pulsation, and flow-induced turbulence are discussed. Additionally, common methods of filtering high-frequency pulsations are discussed in detail.

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Alexeenko, A. A., S. F. Gimelshein, E. P. Muntz e Andrew Ketsdever. Modeling of Thermal Transpiration Flows for Knudsen Compressor Optimization. Fort Belvoir, VA: Defense Technical Information Center, gennaio 2005. http://dx.doi.org/10.21236/ada433782.

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Lagus, P. L., e R. A. Grot. PR-221-9215-R01 Manufacture Pre-Production Gas Flow Measurement System. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), dicembre 1995. http://dx.doi.org/10.55274/r0011966.

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Measurement of the throughput of a natural gas compressor can be undertaken using a constant flow tracer dilution technique. In this technique, a constant flow of tracer is introduced into the piping upstream of the compressor while samples of diluted tracer are measured downstream of the compressor. The samples are analyzed using a specially configured analyzer. Knowledge of the injection rate and injection concentration coupled with the downstream measurement of tracer concentration allows the throughput through the compressor to be calculated. Under this contract, three systems were fabricated and were to be provided to operating pipeline companies for use and evaluation. Each system consisted of an SF6 analyzer, a high-pressure SF6 tracer injection module, and a gas sampling and analyzer support module. The design was modified based on the findings from the field evaluation and a final inspection.

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Shiva, B. G. GMC-93-T03 Regenerative Heat Transfer in Reciprocating Compressors. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), novembre 1993. http://dx.doi.org/10.55274/r0011944.

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Evaluates the impact of heat transfer on reciprocating compressor performance, especially with respect to flow capacity. This paper gives results of the experimental measurements done to determine the contribution of regenerative heat transfer to suction gas heating and its comparison with earlier empirical models. It forms part of ongoing research on estimating the effects of heat transfer on compressor performance with a view to modeling such effects for improved prediction of compressor performance.

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Li, Baisong, e Bo Xu. PR-469-19604-Z01 Auto Diagnostic Method Development for Ultrasonic Flow Meter. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), febbraio 2022. http://dx.doi.org/10.55274/r0012204.

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The objectives of this research are to develop methods for performing ultrasonic flow meter (USM) diagnostic evaluation automatically and a software tool with all necessary attachments. USM-based diagnostics have been established and thirteen categories of knowledge rules of existing cases have been learned and integrated. A search engine for relevant standards, specifications, and other documents of the measurement system has been developed, which enables the free search of text content. Further, with the assistance of modern reasoning techniques, the authorized user only needs to configure an EXCEL file or scripts to activate the rules of the knowledge base by using Drools technology. Therefore, the integration of any potential knowledge rules is convenient and requires no professional skills or changing of the internal source code of the software. Secondly, a new flow meter diagnostic method is proposed based on multiple information methodologies and it is based on the real-time measurement data, operation data, and video data if applicable. The method is intended to identify abnormal states of the measurement system on a real-time basis with the assistance of the knowledge rules and to provide a strategy for mitigating the meter error of components within the measurement system. Thirdly, the applications of Gaussian quadrature diagnostics in daily acquisition nomination change situations and compressor-induced pulsating flow scenarios have been investigated and results are shown in the document. Based on the results, it can be concluded that the measurement uncertainty caused by compressor-induced pulsating flows is obvious, while the measurement uncertainty caused by daily acquisition nomination change is relatively smaller. The software is then developed based on the knowledge, the idea of multiple information methods, and applications of the Gaussian quadrature diagnostics method with all necessary attachments. The architecture, the algorithm, and a few examples are introduced.

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Lagus, P. L., B. S. Flanagan e C. F. Gilbert. PR-197-911-R01 Development of Compressor Performance and Efficiency Evaluation. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), ottobre 1990. http://dx.doi.org/10.55274/r0012073.

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There were two objectives for the program described in this Final Report: 1) to develop and test a portable system to measure flow (and horsepower) in an operating centrifugal natural gas compressor, and 2) to understand and reduce the possible sources of error in the constant flow tracer dilution technique.

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