Academic literature on the topic 'Throughflow model'
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Journal articles on the topic "Throughflow model"
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Yang, Chen, Hu Wu, Jinguang Yang, and Michele Ferlauto. "Time-marching throughflow analysis of multistage axial compressors based on a novel inviscid blade force model." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 14 (April 2019): 5239–52. http://dx.doi.org/10.1177/0954410019840588.
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A time-marching throughflow method for the off-design performance analysis of axial compressors is described. The method is based on the Euler equations, and a new inviscid blade force model is proposed in order to achieve desired flow deflection. The flow discontinuity problems at the leading and trailing edges are tackled by automatic correction of blade mean surface using cubic spline interpolation. Empirical loss models have been integrated into the throughflow model in order to simulate the viscous force effects in the real three-dimensional flow. Two test cases have been presented to validate the throughflow model, including the transonic fan rotor – NASA Rotor 67 working at a near-peak-efficiency point and a 1.5-stage high-speed axial compressor with inlet guide vane operating at 68% nominal speed. Reasonable flow parameters distributions have been obtained in the Rotor 67 fan calculating results, and accurate overall performance characteristics have also been predicted at the strong off-design condition for the 1.5-stage axial compressor. The CPU time of both cases cost less than one minute at one operating point. The results indicate that the developed time-marching throughflow model is effective and efficient in the turbomachinery performance analysis.
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Yang, Chen, Juan Du, Hongwu Zhang, Hu Wu, Qing Tang, and Jinguang Yang. "Time-Marching Throughflow Analysis of Centrifugal Compressors with Boundary Conditions Based on Newton’s Method." Applied Sciences 12, no. 13 (June 29, 2022): 6576. http://dx.doi.org/10.3390/app12136576.
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The meridional distribution of the flow parameters inside the centrifugal compressor is of great importance to its overall performance, as well as its matching performance under a thermal cycle. A time-marching throughflow method for the off-design performance analysis of the centrifugal compressor is described. The method is based on the strictly conservative throughflow-governing equations, and an improved method of boundary-condition enforcement is developed based on Newton’s method to achieve a robust and fast throughflow simulation. An inviscid blade force model was adopted to obtain the flow deflection inside the blade passage. Empirical loss models were integrated into the throughflow model to simulate the viscous force effects in the real three-dimensional flow. Two test cases are presented to validate the throughflow method by comparisons with the experimental data or CFD results, including the NASA low-speed centrifugal compressor (LSCC) and the Allison high-performance centrifugal compressor (HPCC). The simulation indicated that the developed enforcement method for the inlet and outlet boundary conditions significantly improves the computational robustness. For both the LSCC and HPCC cases, reasonable flow-parameter distribution was obtained and accurate overall characteristics were also predicted under the off-design conditions. The results indicated that the developed time-marching throughflow method is effective and efficient for the performance analysis of centrifugal compressors.
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Howard, M. A., and S. J. Gallimore. "Viscous Throughflow Modeling for Multistage Compressor Design." Journal of Turbomachinery 115, no. 2 (April 1, 1993): 296–304. http://dx.doi.org/10.1115/1.2929235.
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An existing throughflow method for axial compressors, which accounts for the effects of spanwise mixing using a turbulent diffusion model, has been extended to include the viscous shear force on the endwall. The use of a shear force, consistent with a no-slip condition, on the annulus walls in the throughflow calculations allows realistic predictions of the velocity and flow angle profiles near the endwalls. The annulus wall boundary layers are therefore incorporated directly into the throughflow prediction. This eliminates the need for empirical blockage factors or independent annulus boundary layer calculations. The axisymmetric prediction can be further refined by specifying realistic spanwise variations of loss coefficient and deviation to model the three-dimensional endwall effects. The resulting throughflow calculation gives realistic predictions of flow properties across the whole span of a compressor. This is confirmed by comparison with measured data from both low and high-speed multistage machines. The viscous throughflow method has been incorporated into an axial compressor design system. The method predicts the meridional velocity defects in the endwall region and consequently blading can be designed that allows for the increased incidence, and low dynamic head, near the annulus walls.
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Hamm, A., H. Remeth, and N. Schilling. "Ecosystem model for a lake with high throughflow." SIL Proceedings, 1922-2010 23, no. 2 (August 1988): 796–800. http://dx.doi.org/10.1080/03680770.1987.11899716.
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Schneider, Niklas, and Tim P. Barnett. "Indonesian throughflow in a coupled general circulation model." Journal of Geophysical Research: Oceans 102, no. C6 (June 15, 1997): 12341–58. http://dx.doi.org/10.1029/97jc00022.
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Feng, Xue, HaiLong Liu, FuChang Wang, YongQiang Yu, and DongLiang Yuan. "Indonesian Throughflow in an eddy-resolving ocean model." Chinese Science Bulletin 58, no. 35 (July 26, 2013): 4504–14. http://dx.doi.org/10.1007/s11434-013-5988-7.
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Wei, Jun, M. T. Li, P. Malanotte-Rizzoli, A. L. Gordon, and D. X. Wang. "Opposite Variability of Indonesian Throughflow and South China Sea Throughflow in the Sulawesi Sea." Journal of Physical Oceanography 46, no. 10 (October 2016): 3165–80. http://dx.doi.org/10.1175/jpo-d-16-0132.1.
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AbstractBased on a high-resolution (0.1° × 0.1°) regional ocean model covering the entire northern Pacific, this study investigated the seasonal and interannual variability of the Indonesian Throughflow (ITF) and the South China Sea Throughflow (SCSTF) as well as their interactions in the Sulawesi Sea. The model efficiency in simulating the general circulations of the western Pacific boundary currents and the ITF/SCSTF through the major Indonesian seas/straits was first validated against the International Nusantara Stratification and Transport (INSTANT) data, the OFES reanalysis, and results from previous studies. The model simulations of 2004–12 were then analyzed, corresponding to the period of the INSTANT program. The results showed that, derived from the North Equatorial Current (NEC)–Mindanao Current (MC)–Kuroshio variability, the Luzon–Mindoro–Sibutu flow and the Mindanao–Sulawesi flow demonstrate opposite variability before flowing into the Sulawesi Sea. Although the total transport of the Mindanao–Sulawesi flow is much larger than that of the Luzon–Mindoro–Sibutu flow, their variability amplitudes are comparable but out of phase and therefore counteract each other in the Sulawesi Sea. Budget analysis of the two major inflows revealed that the Luzon–Mindoro–Sibutu flow is enhanced southward during winter months and El Niño years, when more Kuroshio water intrudes into the SCS. This flow brings more buoyant SCS water into the western Sulawesi Sea through the Sibutu Strait, building up a west-to-east pressure head anomaly against the Mindanao–Sulawesi inflow and therefore resulting in a reduced outflow into the Makassar Strait. The situation is reversed in the summer months and La Niña years, and this process is shown to be more crucially important to modulate the Makassar ITF’s interannual variability than the Luzon–Karimata flow that is primarily driven by seasonal monsoons.
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Humphries, U. W., and D. J. Webb. "On the Indonesian Throughflow in the OCCAM 1/4 degree ocean model." Ocean Science 4, no. 3 (July 28, 2008): 183–98. http://dx.doi.org/10.5194/os-4-183-2008.
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Abstract. The Indonesian Throughflow is analysed in two runs of the OCCAM 1/4 degree global ocean model, one using monthly climatological winds and one using ECMWF analysed six-hourly winds for the period 1993 to 1998. The long-term model throughflow agrees with observations and the value predicted by Godfrey's Island Rule. The Island Rule has some skill in predicting the annual signal each year but is poor at predicting year to year and shorter term variations in the total flow, especially in El Niño years. The spectra of transports in individual passages show significant differences between those connecting the region to the Pacific Ocean and those connecting with the Indian Ocean. On investigation we found that changes in the northern transports were strongly correlated with changes in the position of currents in the Celebes Sea and off Halmahera. Vertical profiles of transport are in reasonable agreement with observations but the model overestimates the near surface transport through the Lombok Strait and the dense overflow from the Pacific through the Lifamatola Strait into the deep Banda Sea. In both cases the crude representation of the passages by the model appears responsible. In the north the model shows, as expected, that the largest transport is via the Makassar Strait. However this is less than expected and instead there is significant flow via the Halmahera Sea. If Godfrey's Island Rule is correct and the throughflow is forced by the northward flow between Australia and South America, then the Halmahers Sea route should be important. It is the most southerly route around New Guinea to the Indian Ocean and there is no apparent reason why the flow should go further north in order to pass through the Makassar Strait. The model result thus raises the question of why in reality the Makassar Strait route appears to dominate the throughflow.
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Humphries, U. W., and D. J. Webb. "On the Indonesian throughflow in the OCCAM 1/4 degree ocean model." Ocean Science Discussions 4, no. 2 (March 21, 2007): 325–70. http://dx.doi.org/10.5194/osd-4-325-2007.
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Abstract. The Indonesian Throughflow is analysed in two runs of the OCCAM 1/4 degree global ocean model, one using monthly climatological winds and one using ECMWF analysed six-hourly winds for the period 1993 to 1998. The long-term model throughflow agrees with observations and the value predicted by Godfrey's Island Rule. The Island Rule has some skill in predicting the annual signal each year but is poor at predicting year to year and shorter term variations in the total flow especially in El Nino years. The spectra of transports in individual passages show significant differences between those connecting the region to the Pacific Ocean and those connecting with the Indian Ocean. This implies that different sets of waves are involved in the two regions. Vertical profiles of transport are in reasonable agreement with observations but the model overestimates the near surface transport through the Lombok Strait and the dense overflow from the Pacific through the Lifamatola Strait into the deep Banda Sea. In both cases the crude representation of the passages by the model appears responsible. In the north the model shows, as expected, that the largest transport is via the Makassar Strait. However this is less than expected and instead there is significant flow via the Halmahera Sea. If Godfrey's Island Rule is correct and the throughflow is forced by the northward flow between Australia and South America, then the Halmahers Sea route should be important. It is the most southerly route around New Guinea to the Indian Ocean and there is no apparent reason why the flow should go further north in order to pass through the Makassar Strait. The model result thus raises the question of why in reality the Makassar Strait route appears to dominate the throughflow.
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Smith, Nils Solheim, Ganesh H. R. Ravindra, and Fjóla Guðrún Sigtryggsdóttir. "Numerical Modeling of the Effects of Toe Configuration on Throughflow in Rockfill Dams." Water 13, no. 13 (June 22, 2021): 1726. http://dx.doi.org/10.3390/w13131726.
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The rockfill toe structure situated within the downstream slope of rockfill dams is an integral part of a defense mechanism safeguarding the dam structure in throughflow situations. Recent studies have concluded that the rockfill toe structure can have significant impacts on throughflow development and stability of rockfill dams under scenarios of accidental throughflow caused by overtopping of the dam core. The ability to numerically model the effect of various toe configurations on flow through rockfill dams can support the design of effective toe drainage structures for rockfill dams. Development and calibration of a reliable numerical modeling tool in this regard has been challenging owing to lack of availability of extensive datasets from physical modeling investigations. This study further employs datasets gathered by a recent physical modeling study investigating the effects of various toe configurations on throughflow development in rockfill dam models. A commercial numerical seepage modeling tool with an option for non-Darcy flow was calibrated against the datasets with good calibration metrics. The study is novel in providing a rare report on the usage of this option. The calibrated tool can further be employed to carry out a wide array of simulations to arrive at an ideal design for a toe structure for rockfill dams and for assessment of hydraulic performance of toe structures.
Dissertations / Theses on the topic "Throughflow model"
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Atmadipoera, Agus. "Indonesian throughflow water in the major outflow straits(Lombok, Ombai, Timor) : from instant data and numerical model." Paris 6, 2009. http://www.theses.fr/2009PA066325.
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Ce travail se concentre sur une région clef de la circulation océanique globale avec le passage des eaux du Pacifique tropical dans l’Océan Indien à travers l’archipel indonésien, l’ « Indonesian throughflow (ITF) ». Cette région a été l’objet d’une coopération internationale d’envergure, INSTANT1, entre l’Indonésie, la France, les Pays-Bas, les USA et l’Australie. Une quantité importante de nouvelles données de courant, de température et de salinité ont été recueillies à cette occasion pendant les campagnes océanographiques auxquelles j’ai participé. Ma thèse analyse ces données pour étudier la variabilité spatiale et temporelle des « Indonesian Throughflow Water (ITW) », à leur sortie dans l’Océan Indien. Les données sont analysées en utilisant les sorties du modèle ORCA du LOCEAN afin de compléter les lacunes temporelles et spatiales inévitables des mesures. Il est démontré dans une première partie l’importance des eaux peu salées et plus chaude de la mer de Java qui modifient les eaux superficielles provenant du détroit de Makassar. Les caractéristiques de ces eaux affectent ensuite les eaux plus profondes par mélanges verticaux dus aux fortes marées dans la région au cours de la progression de l’ITF vers l’est de la Mer de Florès aux détroits de sortie vers l’Océan Indien. L’ITW apparaît le plus chaud et le moins salé dans la thermocline depuis la période de transition, avril-juin jusqu’à la mousson de sud-est, juillet-septembre. La deuxième partie s’intéresse au plateau continental australien, le Sahul, où il est montré que l’apport d’eau salée provenant de l’Océan Indien pendant la mousson de nord ouest contribue pour 12% du transport total à Timor dans les premier 318m, en moyenne annuelle et peut représenter 40% du transport de l’ITF à travers le passage pendant la mousson de nord ouest. La troisième partie tente d’expliquer la présence d’un courant profond au dessus du seuil du passage de Timor par la propagation d’ondes de Kelvin excitées dans l’Océan tropical Indien par des coups de vent d’ouest et piégées le long de la côte indonésienne. Ces ondes se propagent vers le sud et pénètrent dans les mers indonésiennes à travers les détroits ouverts sur l’Océan Indien et seule la partie profonde de ces ondes atteignent le seuil du passage de Timor. Ce courant en va-et-vient intéresse les eaux profondes et a une moyenne non nulle vers le bassin de Timor dont la topographie interdit la sortie vers les mers indonésiennes. Un courant vertical doit donc exister, produit par des mélanges verticaux.
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Wekerle, Claudia [Verfasser], Qiang [Akademischer Betreuer] Wang, Peter [Akademischer Betreuer] Lemke, and Thomas [Akademischer Betreuer] Jung. "Dynamics of the Canadian Arctic Archipelago throughflow: A numerical study with a finite element sea ice and ocean model / Claudia Wekerle. Gutachter: Peter Lemke ; Thomas Jung. Betreuer: Qiang Wang." Bremen : Staats- und Universitätsbibliothek Bremen, 2013. http://d-nb.info/1072077787/34.
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Villanoy, Cesar Laurel. "Modification of the throughflow water properties in the Indonesian seas." Thesis, The University of Sydney, 1993. https://hdl.handle.net/2123/26591.
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Vertical mixing in the Indonesian Seas has been considered to be responsible for the apparent freshness of the throughflow when 'it enters the Indian Down. A three-dimensional primitive equation numerical model of the Indonesian Seas forced with a prescribed throughflow, transport consisting of North Pacific waters, is used to determine local dynamic processes which may modify the characteristics of the throughflow properties. The lack of long-term current measurements in the Indonesian Seas presents some difficulties in determining the certainty of the derived velocity fields. As an alternative, the model temperature and salinity fields are compared to observed hydrographic data which has a relatively better coverage throughout the Indonesian Seas. A 15 Sv net transport through the Indonesian Seas is suggested based on the model’s more realistic reproduction of the hydrographic structure compared to a throughflow with a smaller magnitude. A pure North Pacific source for the throughflow is also not capable of producing the salinity structure in the Banda Sea as suggested by previous studies and the required amount of salt to fit the model salinity structure with observations in the Banda Sea is estimated to be 3.3x10‘3 kg.
Most of the throughflow transport occurs in western boundary flows and is largely topographically controlled. The separation of an upper and lower layer circulation pattern is controlled by the depth of the sill in Makassar Strait. Vertical excursions in the vicinity of this sill seen level of the in model results coincide upper salinity maximum with regions where are found. Seasonal large horizontal gradients at the upwelling and longer residence times due to weaker flows in the Banda Sea results in a more effective mixing of the already weakened salinity structure of the waters from Makassar Strait/Flores Sea. Net heat and freshwater flux estimates also reveal significant departures at 200 up to 100 m between the Pacific inflow and Indian outflow, suggesting the considerable redistribution of heat and salt in the Indonesian Seas.
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Gill, Andrew. "A comparison between stall prediction models for axial flow compressors." Thesis, Stellenbosch : Stellenbosch University, 2006. http://hdl.handle.net/10019.1/18702.
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Thesis (MScEng)--Stellenbosch University, 2006.ENGLISH ABSTRACT: The Stellenbosch University Compressor Code (SUCC) has been developed for the purpose of predicting the performance of axial flow compressors by means of axisymmetric inviscid throughflow methods with boundary layer blockage and empirical blade row loss models. This thesis describes the process of the implementation and verification of a number of stall prediction criteria in the SUCC. In addition, it was considered desirable to determine how certain factors influence the accuracy of the stall prediction criteria, namely the nature of the computational grid, the choice of throughflow method used, and the use of a boundary layer blockage model and a radial mixing model. The stall prediction criteria implemented were the di®usion factor limit criterion, de Haller's criterion, Aungier's blade row criterion, Aungier's boundary layer separation criterion, Dunham's, Aungier's and the static-to-static stability criteria. The compressors used as test cases were the Rofanco 3-stage low speed compressor, the NACA 10-stage subsonic compressor, and the NACA 5-stage and 8-stage transonic compressors. Accurate boundary layer blockage modelling was found to be of great importance in the prediction of the onset of stall, and that the matrix throughflow Method provided slightly better accuracy than the streamline curvature method as implemented in the SUCC by the author. The ideal computational grid was found to have many streamlines and a small number of quasi-orthogonals which do not occur inside blade rows. Radial mixing modelling improved the stability of both the matrix throughflow and streamline curvature methods without significantly affecting the accuracy of the stall prediction criteria. De Haller's criterion was over-conservative in estimating the stall line for transonic conditions, but more useful in subsonic conditions. Aungier's blade row criterion provided accurate results on all but the Rofanco compressor. The diffusion factor criterion provided over- optimistic predictions on all machines, but was less inaccurate than de Haller's criterion on the NACA 5-stage transsonic machine near design conditions. The stability methods performed uniformly and equally badly, supporting the claims of other researchers that they are of limited usefulness with throughflow simulations. Aungier's boundary layer separation method failed to predict stall entirely, although this could reflect a shortcoming of the boundary layer blockage model.
AFRIKAANSE OPSOMMING: Die Stellenbosch University Compressor Code (SUCC) is ontwikkel om die prestasie van aksiaalvloei kompressors te voorspel met behulp van aksisimmetriese nie-viskeuse deurvloeimetodes met grenslaagblokkasie en empiriese modelle vir die verliese binne lemrye. Hierdie tesis beskryf die proses waarmee sekere staakvoorspellingsmetodes in die SUCC geïmplementeer en geverifieer is. Dit was ook nodig om die effek van sekere faktore, naamlik die vorm van die berekeningsrooster, die keuse van deurvloeimetode en die gebruik van `n grenslaagblokkasiemodel en radiale vloeivermengingsmodel op die akuraatheid van die staakvoorspellingsmetodes te bepaal. Die staakvoorspellingsmetodes wat geïmplementeer is, is die diffusie faktor beperking metode, de Haller se metode, Aungier se lemrymetode, Aungier se grenslaagmetode en die Dunham, Aungier en die statiese-tot-statiese stabiliteitsmetodes. Die kompressors wat gebruik is om die metodes te toets is die Rofanco 3-stadium lae-spoed kompressor, die NACA 10-stadium subsoniese kompressor en die NACA 5- en 8-stadium transsoniese kompressors. Daar is vasgestel dat akkurate grenslaagblokkasie modelle van groot belang was om `n akkurate aanduiding van die begin van staking te voorspel, en dat, vir die SUCC, die Matriks Deurvloei Metode oor die algemeen 'n bietjie meer akkuraat as die Stroomlyn Kromming Metode is. Daar is ook vasgestel dat die beste berekeningsrooster een is wat baie stroomlyne, en die kleinste moontlike getal quasi-ortogonale het, wat nie binne lemrye geplaas mag word nie. Die numeriese stabiliteit van beide die Matriks Deurvloei en die Stroomlyn Kromming Metode verbeter deur gebruik te maak van radiale vloeivermengingsmodelle, sonder om die akkuraatheid van voorspellings te benadeel. De Haller se metode was oorkonserwatief waar dit gebruik is om die staak-lyn vir transsoniese vloei toestande, maar meer nuttig in die subsoniese vloei gebied. Aungier se lemrymetode het akkurate resultate gelewer vir alle kompressors getoets, behalwe die Rofanco. Die diffusie faktor metode was oor die algemeen minder akuraat as Aungier se metode, maar meer akkuraat as de Haller se metode vir transsoniese toestande. Die stabiliteitsmetodes het almal ewe swak gevaar. Dit stem ooreen met die bevindings van vorige navorsing, wat bewys het dat hierdie metodes nie toepaslik is vir simulasies wat deurvloeimetodes gebruik nie. Aungier se grenslaagmetode het ook baie swak gevaar. Waarskynlik is dit as gevolg van tekortkomings in die grenslaagblokkasiemodel.
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Ricci, Martina. "Improvements in CFD-based throughflow methods for analysis and design of axial turbines." Doctoral thesis, 2020. http://hdl.handle.net/2158/1192780.
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The research activity presented in this work has been devoted to the extension and improvement of a CFD-based throughflow code aimed at the development of a meridional analysis tool for modern industrial design systems for turbomachinery.
The throughflow code inherits its numerical scheme from a state-of-the-art CFD solver (TRAF code) and incorporates real gas capabilities, three-dimensional flow features, and spanwise mixing models. Secondary flow effects are introduced via a concentrated vortex model. Tip gap and shroud leakage effects are modelled in terms of source vectors in the system of governing equations. Also, film cooling and purge flow injections are taken into account as source terms vectors that are applied in selected regions of the meridional flowpath. The impact of part-span shrouds and snubbers are considered, on a local basis, through suitable body force fields.
The advection upstream splitting method (AUSM+ -up) upwind strategy has been adopted as a basis to construct a numerical flux scheme explicitly suited for throughflow applications. The original formulation has been adapted to handle real gas flows and to embed the treatment of body force fields in a fully consistent framework. In order to relieve the time-step limitations associated with source terms, an implicit treatment of the axisymmetric and force vectors has been considered.
During the research activity a methodology for gas turbines off-design analyses, based on the application of the throughflow method, has also been developed.
The effectiveness of the proposed methodology will be discussed by reporting the results obtained for three of the test cases used for the validation activity, for which detailed experimental data are available (the T106 high-lift, low-pressure turbine blade, the KTH 4b subsonic high-pressure steam turbine stage, and the CT3 stage high-pressure transonic gas turbine). Each one of these allows us the assessment of the various physical models included in the framework.
Finally, the capabilities of the throughflow procedure is assessed by applying it to the study of some industrial axial turbine configurations designed and manufactured by Ansaldo Energia. The first one is a four-stage, air-cooled gas turbine. A detailed analysis at design point will be presented together with an extensive off-design study over a wide range of operating conditions with varying expansion ratios and operating speed. The last two test cases are the low-pressure modules of two large steam turbines. The assessment of the throughflow predictions will be discussed by scrutinizing them against 3D CFD analyses carried out with the TRAF code and the available experimental data.
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Berger, AP. "Mean circulation of the Indonesian throughflow and a mechanism of its partitioning between outflow passages : a regional model study." Thesis, 2020. https://eprints.utas.edu.au/34790/1/Berger_whole_thesis.pdf.
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The Indonesian Throughflow (ITF) is the only low latitude connection of the global circulation and is an essential pathway for mass, heat and salt exchange between the Pacific and Indian Oceans. The ITF is a boundary current constrained by topography and is characterised by two source pathways, a western and an eastern. At the exit to the Indian Ocean, observations show the ITF partitions amongst the three major outflow straits. The westernmost, Lombok Strait, has the lowest transport even though it is expected to carry most of the flow given that the ITF is a boundary current and this strait is a direct continuation of the western pathway. Heat and saltwater transports are different in each outflow strait and thus exchanged properties depend on the partitioning, consequently affecting the contribution to the Indian Ocean. In this study, we explore the ITF circulation and local dynamics that control the ITF partitioning.
To explore what controls ITF partitioning in the context of western boundary current theories, we simulate a steady ITF in a high-resolution (4-km) regional model. The forcing consists of time-averaged velocity, temperature and salinity fields from the global model Ocean Forecasting Australia Model v3 (OFAM3). We investigate what sets the amount of western pathway water that exits via Lombok Strait in the regional model. Our reference simulation confirms the two ITF pathways and gives a mean ITF of 14.1 Sv and an outflow partitioning of 0.2:0.4:0.4 (Lombok:Ombai:Timor), consistent with observations. Focusing on the western pathway, comprising 70% of the total ITF, we investigate the routes this water follows to the Indian Ocean. Here we consider partitioning as the ratio between transport in Lombok and Makassar Straits. Relative to only Makassar Strait transport, Lombok Strait still has the lowest transport portion of the three outflows (27%). Idealised perturbation experiments help us to investigate boundary current dynamics; combinations of slip/non-slip boundary conditions and linear/non-linear advection in the momentum equations illustrate the effects of current width (CW) on partitioning. Our key finding from this analysis is that the CW in the Makassar Strait controls the Lombok Strait transport; a narrower boundary current can fit more flow through a narrow strait. To understand what sets the CW, we perform a vorticity budget. The reference simulation reveals that the leading order term that balances change in planetary vorticity is advection of vorticity. The vorticity term diagnostics for the perturbation experiments suggest non-linearity is the main term controlling the ITF current width.
We test how CW influences partitioning in more realistic conditions and evaluate how low-frequency variability affects partitioning, analysing 18-yr of a global fully-realistic model OFAM3. Consistent with our perturbation experiments, we find CW in Makassar Strait controls transport in Lombok Strait. Further, we find that, on the inter-annual scale, the Makassar Strait CW is approximately constant. This suggests that Makassar Strait may be saturated and similar dynamics could also take place upstream in the ITF western pathway. Specifically, we find that the width of Makassar Strait constrains the CW, independent of variations in CW at the upstream inflow ITF at Mindanao boundary current. As a consequence, during years when Mindanao current is wide at the Indonesian Seas entrance, the flow does not entirely fit in Makassar Strait. This flow that did not fit in Makassar Strait joins the eastern pathway. The increase of inflow in the eastern pathway produces a change in transport at Timor Passage, providing a link between variability at Timor Passage and that of the Mindanao.
Our results suggest that, given the ITF complexity, the simple concept of partitioning cannot be easily used as a proxy for ITF transports and predictions cannot be made based on single strait measurements. The ITF western pathway provides a more direct connection to the Indian Ocean compared to the eastern pathway. The changes eastern pathway waters undergo while circulating in the Indonesian Seas are crucial for understanding heat and tracers exchange between the two oceans. Finally, understanding what controls the ITF circulation and its variability is critical to better predicting how the ITF responds to climate change.
Book chapters on the topic "Throughflow model"
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Schiller, Andreas, Susan E. Wijffels, and Janet Sprintall. "Chapter 8 Variability of the Indonesian Throughflow: A Review and Model-to-Data Comparison." In Elsevier Oceanography Series, 175–494. Elsevier, 2007. http://dx.doi.org/10.1016/s0422-9894(06)73008-2.
Full textConference papers on the topic "Throughflow model"
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Dunham, John. "A New Endwall Model for Axial Compressor Throughflow Calculations." In ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/94-gt-075.
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It is well recognised that the endwall regions of a compressor — in which the annulus wall flow interacts with the mainstream flow — have a major influence on its efficiency and surge margin. Despite many attempts over the years to predict the very complex flow patterns in the endwall regions, current compressor design methods still rely largely on empirical estimates of the aerodynamic losses and flow angle deviations in these regions. This paper describes a new phenomenological model of the key endwall flow phenomena treated in a circumferentially-averaged way. It starts from Hirsch and de Ruyck’s annulus wall boundary layer approach, but makes some important changes. The secondary vorticities arising from passage secondary flows and from tip clearance flows are calculated. Then the radial interchanges of momentum, energy and entropy arising from both diffusion and convection are estimated The model is incorporated into a streamline curvature program. The empirical blade force defect terms in the boundary layers are selected from cascade data. The effectiveness of the method is illustrated by comparing the predictions with experimental results on both low speed and high speed multistage compressors. It is found that the radial variation of flow parameters is quite well predicted, and so is the overall performance, except when significant endwall stall occurs.
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Wu, Hong, Qiushi Li, and Sheng Zhou. "Optimization of Highly Loaded Fan Rotor Based on Throughflow Model." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27603.
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This paper presents an optimization method for fan/compressor which couples throughflow model solving axisymmetric Euler equations with adaptive simulated annealing (ASA) algorithm. One of the advantages of this optimization method is that it spends much less time than 3D optimization due to the rapid solving of throughflow model. In addition, the optimization space is quite extensive because more design variables can be adjusted in throughflow phase, such as swirl distribution, hub curve and sweep. To validate this optimization method, a highly loaded fan rotor with pressure ratio of 3.06 as a baseline is optimized. During the optimization process, the objective function is total pressure ratio, moreover, mass flow and efficiency are selected as the constraint conditions. Three important design variables including swirl distribution, hub curve and sweep are parameterized using Bezier curve, and then optimized in throughflow model independently, finally the optimum designs are validated using 3D viscous CFD solver. It is shown that pressure ratio and rotor loading can be improved further through optimizing swirl distribution, however, hub and sweep curves take more effects on mass flow and efficiency respectively. The optimization results demonstrate the advantage and feasibility of this optimization method.
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Thomas, J. P., and O. Le´onard. "Investigating Circumferential Non-Uniformities in Throughflow Calculations Using an Harmonic Reconstruction." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50328.
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The computation time and the extraction of useful information remain severe drawbacks to systematic use of modern three-dimensional Navier-Stokes codes in a design procedure of multistage turbomachines. That explains why throughflow simulation is still widely used at industrial scale. The main limitation of throughflow is however the need for empirical models to reproduce blade-flow interactions and major 3D flow features. The purpose of this work is to investigate the degree to which empiricism could be reduced by using the averaged-passage equations of Adamczyk, combined with an harmonic closure strategy. To that aim, results of a computation performed with a steady three-dimensional Navier-Stokes code are used to calculate some of the additional terms of the circumferentially-averaged equations, the so-called circumferential stresses. The importance of the latter to bring back the mean effect of circumferential non-uniformities is proven by injecting them into a throughfow simulation. The frequency spectrum of these terms is next investigated and it is demonstrated that an harmonic reconstruction can model the circumferential stresses.
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Chaquet, Jose M., Roque Corral, and Alfredo Fernandez. "Accurate Method to Reproduce Throughflow Results With a Meanline Solver." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63153.
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A novel method to generate meanline models from through-flow results of low pressure turbines (LPT) is presented. Using a fast optimization approach, it is shown that it is possible to reproduce with the reduced fidelity model the main performance variables of the throughflow case, such as stage powers, pressure ratios, Mach numbers or Smith charts, with negligible errors in practical terms. Providing two throughflow models (a three-stage LPT rig and a six-stage plus an outlet guide vane LPT), it is discussed which variables should be matched in order to obtain a representative meanline model. It is studied as well the radial angle influence on the matching process. Using meanline models could have some benefits in the fast assessment of geometry and operation conditions changes due to their flexibility, robustness and easy setup compared with a throughflow simulation.
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Ba, Wei, and Xiaodong Ren. "Aero-Thermal Coupled Throughflow Method With Cooling Model Based on Flow Network Analysis." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63614.
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The aero-thermal coupled phenomenon is significant in the modern cooled turbine, and it is necessary to consider the cooling effect in the throughflow design phase. A new cooling model based on flow network analysis for the aero-thermal coupled throughflow method was developed to consider the film cooling effect and predict the blade wall temperature downstream of the film cooling holes. The flow network analysis is introduced into the cooling model to determine the flow rate of each cooling hole. The mixing loss caused by film cooling is investigated as local total pressure loss, and the heat transfer influence caused by film cooling is considered by the film cooling effectiveness estimated by empirical correlation. The blade heat transfer downstream the film cooling holes is calculated from pressure and suction surfaces separately, based on main flow parameters calculated by the streamline curvature method. The experimental data of the C3X profile is selected for the cooling model verification. The film cooling flow rate calculated by the flow network analysis agrees well with the experimental data, and the calculated temperatures of both the pressure and suction surfaces downstream the film cooling holes are also in accordance with the experimental data. Therefore, aero-thermal coupled throughflow method with this cooling model can be a powerful tool for preliminary design of cooled turbine.
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Howard, M. A., and S. J. Gallimore. "Viscous Throughflow Modelling for Multi-Stage Compressor Design." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-302.
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An existing throughflow method for axial compressors, which accounts for the effects of spanwise mixing using a turbulent diffusion model, has been extended to include the viscous shear force on the endwall. The use of a shear force, consistent with a no-slip condition, on the annulus walls in the throughflow calculations allows realistic predictions of the velocity and flow angle profiles near the endwalls. The annulus wall boundary layers are therefore incorporated directly in the throughflow prediction. This eliminates the need for empirical blockage factors or independent annulus boundary layer calculations. The axisymmetric prediction can be further refined by specifying realistic spanwise variations of loss coefficient and deviation to model the three-dimensional endwall effects. The resulting throughflow calculation gives realistic predictions of flow properties across the whole span of a compressor. This is confirmed by comparison with measured data from both low and high speed multi-stage machines. The viscous throughflow method has been incorporated into an axial compressor design system. The method predicts the meridional velocity defects in the endwall region and consequently blading can be designed which allows for the increased incidence, and low dynamic head, near to the annulus walls.
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Gui, X., and S. Zhou. "A Transonic Compressor Design Methodology Including the Influence of 3D Passage Shock Waves." 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-078.
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Throughflow theory, as a design problem, is extensively used in the design of transonic axial flow compressors and fans. The losses caused by a simplified passage shock named shock loss model were taken into account in the design of transonic stages. However, the influences of shock waves on flow fields are still under development for transonic design. This problem is studied in the present paper. The basic equations of the throughflow method are re-derived under the concept of discontinuous passage averaging, and then, the distribution shock forces acied on the averaged throughflow fields are obtained. To evaluate these effects on averaged throughflow fields, a passage shock structure model is developed based on the previous models. Finally, the shock influences are assessed and compared in the present paper. It is demonstrated that the distribution shock forces have dramatically effects on the results of design.
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Li, Jian, Dongrun Wu, Jinfang Teng, Mingmin Zhu, and Xiaoqing Qiang. "The Effects of Incidence and Deviation on the CFD-Based Throughflow Analysis." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14293.
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Abstract A major concern in the Computational Fluid Dynamics (CFD)-based throughflow calculation is the treatment of the incidence and deviation. This paper investigates the effects of the incidence and deviation on the CFD-based throughflow analysis by a time-marching throughflow model. The model is realized by solving complete Navier-Stokes equations with a single grid in the g-wise direction. The inviscid blade force is determined by calculating a pressure difference between the pressure and suction surfaces. The losses are introduced by imposing a blade surface skin friction factor converted from the pressure loss coefficient. And the flow discontinuity problem at the leading and trailing edges is resolved by modifying the mean blade surface to accommodate the incidence and deviation. The sensitivity of the throughflow results to the modification strategy of the mean blade surface is studied through response surface method. And the Kriging-assisted genetic algorithm (GA) is applied to determine the optimal distributions of incidence and deviation in the streamwise direction for NASA Rotor 37. Finally, four examples are provided to validate the throughflow model and to demonstrate the effects of incidence and deviation on CFD-based throughflow analysis at off-design conditions.
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Dunham, J. "Analysis of High Speed Multistage Compressor Throughflow Using Spanwise Mixing." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-013.
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Previous RAE papers have described the application of an S1-S2 flow calculation system, which does not model spanwise mixing, to the RAE C147 high speed research core compressor. Although this has proved a valuable design and analysis tool, it is shown by comparison with detailed interstage traverse measurements that it does not model accurately the radial profiles of stagnation temperature, pressure and flow angle as they develop through the C147. Published work utilising low speed compressor measurements has shown that the inclusion of spanwise mixing terms in throughflow analysis can improve the modelling of radial profiles while allowing more realistic loss models to be used. This paper describes the application of the Gallimore/Cumpsty spanwise mixing model to the C147 compressor. A brief description of the modelling is given, especially the simple annulus wall model not covered by the Gallimore/Cumpsty papers. Then a model of the C147 flow is constructed using simple endwall loss and deviation assumptions, together with other changes needed to represent what seems to be a hub stall. It is concluded that the mixing terms enable realistic radial distributions of loss and deviation to reproduce the observed flow. The temperature mixing terms are particularly important in a high speed unit because they prevent the erroneous accumulation of high temperatures near the walls.
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Vo¨lker, Lutz, Michael Casey, John Dunham, and Heinrich Stu¨er. "The Influence of Lean and Sweep in a Low Pressure Steam Turbine: Throughflow Modelling and Experimental Measurements." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50188.
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This paper describes experimental and throughflow investigations on two configurations of a model three-stage low pressure steam turbine. A companion paper describes 3D CFD simulations of the same turbine test data. Global performance measurements and detailed flow field measurements with pneumatic flow probes were carried out to quantify the changes in the design due to the introduction of sweep in the last stator nozzle vanes. An existing 2D throughflow code was improved to enable the present calculations to be completed. The test results have been used in this paper to calibrate the 2D throughflow model, by adjustment of empirical correlation data to match the experimental data on one of the configurations. This throughflow model was then used to examine the influence of lean and sweep on the design. The results identify that throughflow calculations can model the global effects of lean and sweep in the last stages of steam turbines. Some insight is gained on the losses across the span for the different configurations and on the benefits of lean and sweep in reducing the hub reaction in such stages.
Reports on the topic "Throughflow model"
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Ko, Hon-Yim, R. J. Dunn, and Tom Hollingsworth. Study of Embankment Performance during Overtopping and Throughflow. Report 3. Model-Prototype Comparison Studies. Fort Belvoir, VA: Defense Technical Information Center, April 1989. http://dx.doi.org/10.21236/ada207954.
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