Academic literature on the topic 'Suction Envelop'
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Journal articles on the topic "Suction Envelop"
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Kumar, K. M., P. Venkateswaran, and P. Suresh. "Effective Fuel Consumption by Improving Cooling Water Flow Rate in IC Engine." Applied Mechanics and Materials 812 (November 2015): 112–17. http://dx.doi.org/10.4028/www.scientific.net/amm.812.112.
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The coolant (water) pump assumes an important role of cooling system in IC engines. With upgrading of the engine power by turbocharging and turbo inter cooling, the water pump capacity needs to be increased corresponding to the power. This capacity enhancement has to be achieved without calling for a major change in the existing water pump, envelop and related fitment details. This requires a clear understanding of centrifugal pump for its performance parameter. One such engine is upgraded by turbocharging from 195PS to 240PS @2200 rpm. Improving water pump flow by changing the impeller dimensions, impeller casing, increase the suction, delivery pipe diameter had been done. Validation of the water pump in its actual engine installation was taken up as a part of the research work. Flow rate comparison of the new pump with the existing pump was made and the results were analyzed. The new water pump gives better flow rates for the engine speeds up to1800 rpm, beyond which the flow rate is slightly lesser than the existing pump.
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Tang, Gary X., and James Graham. "A possible elasticplastic framework for unsaturated soils with high-plasticity." Canadian Geotechnical Journal 39, no. 4 (August 1, 2002): 894–907. http://dx.doi.org/10.1139/t02-024.
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The paper proposes a new elasticplastic framework for unsaturated, high-plasticity, clayey soils and sandclay mixtures. The framework considers possible coupling of stress- and suction-induced hardening, leading to a yield surface that is closed or "capped" as suctions increase. This produces a stress state boundary surface in three-dimensional pqs stress space (where p is the net mean stress, q is the deviator stress, and s is the matric suction) which differs from that of other conceptual models of its kind. Yielding, a hardening law, and failure criteria for saturated soils are incorporated into the stress state boundary surface. Two parameters, equivalent pressure pe and stress ratio ηs, are introduced to form the basis of the proposed elasticplastic framework for highly plastic soils with high suctions. This provides an alternative for the stress variables net mean stress and matric suction that are commonly used in modeling unsaturated soils with lower plasticity and lower suctions. This framework has allowed results of experiments on an unsaturated sandbentonite mixture to be successfully described using elastoplasticity. Yield and failure envelopes associated with the proposed state boundary surface in pqs space can be normalized using pe and ηs in such a way that they agree with a comparable envelope for saturated specimens. Key words: unsaturated, elasticplastic, triaxial, matric suction, state boundary surface, sand-bentonite.
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Gong, Xiu Bin, Qing Lai Fan, and Ke Wu. "Bearing Capacity of Suction Caisson for Offshore Floating Wind Turbine." Advanced Materials Research 243-249 (May 2011): 4718–22. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4718.
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Presented in this paper are the three-dimensional nonlinear finite element analyses of the failure envelopes of suction caisson under torsion, vertical and lateral pullout combined load in soft clay. The soft clay under undrained condition is simulated by perfectly elasto-plastic Tresca model. Through the numerical analyses, the failure envelopes for combined loading (V-T、H-T、V-H-T) of suction caisson is reviewed. And the mathematical expression of failure envelope is deduced. It is shown that (1) the circular plastic failure area is outward-extending. (2) The bearing capacity of suction caisson foundation in V-T、H-T load spaces is increasing with the aspect ratio L/D. (3) The equation of failure envelope can be used to evaluate the stability of suction caisson foundation for offshore floating wind turbine.
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Hossain, Md Akhtar, and Jian-Hua Yin. "Shear strength and dilative characteristics of an unsaturated compacted completely decomposed granite soil." Canadian Geotechnical Journal 47, no. 10 (October 2010): 1112–26. http://dx.doi.org/10.1139/t10-015.
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Shear strength and dilative characteristics of a re-compacted completely decomposed granite (CDG) soil are studied by performing a series of single-stage consolidated drained direct shear tests under different matric suctions and net normal stresses. The axis-translation technique is applied to control the pore-water and pore-air pressures. A soil-water retention curve (SWRC) is obtained for the CDG soil from the equilibrium water content corresponding to each applied matric suction value for zero net normal stress using a modified direct shear apparatus. Shear strength increases with matric suction and net normal stress, and the failure envelope is observed to be linear. The apparent angle of internal friction and cohesion intercept increase with matric suction. A greater dilation angle is found at higher suctions with lower net normal stresses, while lower or zero dilation angles are observed under higher net normal stresses with lower suctions, also at a saturated condition. Experimental shear strength data are compared with the analytical shear strength results obtained from a previously modified model considering the SWRC, effective shear strength parameters, and analytical dilation angles. The experimental shear strength data are slightly higher than the analytical results under higher net normal stresses in a higher suction range.
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Gan, J. K. M., D. G. Fredlund, and H. Rahardjo. "Determination of the shear strength parameters of an unsaturated soil using the direct shear test." Canadian Geotechnical Journal 25, no. 3 (August 1, 1988): 500–510. http://dx.doi.org/10.1139/t88-055.
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Multistage direct shear tests have been performed on saturated and unsaturated specimens of a compacted glacial till. A conventional direct shear apparatus was modified in order to use the axis-translation technique for direct shear tests on unsaturated soils. The soil can be subjected to a wide range of matric suctions. The testing procedure and some typical results are presented. Nonlinearity in the failure envelope with respect to matric suction was observed. Suggestions are made as to how best to handle the nonlinearity from a practical engineering standpoint. Key words: shear strength, unsaturated soils, negative pore-water pressures, soil suction, direct shear.
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Hoyos, Laureano R., Jairo E. Yepes, Claudia L. Velosa, and Anand J. Puppala. "Unsaturated Shear Strength of Compacted Clayey Soil via Suction-controlled Ring Shear Testing." E3S Web of Conferences 195 (2020): 03024. http://dx.doi.org/10.1051/e3sconf/202019503024.
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An experimental program has been undertaken to assess both peak and residual shear strength parameters of statically compacted, moderate plasticity clayey soil under suction-controlled conditions, resulting in a defined set of suction-dependent peak and residual failure envelopes over a relatively wide range of suction states, from 0 to 300 kPa. The experimental program was accomplished in a servo/suction-controlled ring shear apparatus, which is suitable for testing unsaturated soils under large deformations via the axis-translation technique. Test results substantiate the crucial role that has been observed to be played by the imposed matric suction on the residual shear strength of compacted clayey soils. For the range of net normal stress (0-200 kPa) and matric suction (0-300 kPa) states investigated, the increase in either peak or residual shear strength, with increasing matric suction, was found to be manifestly nonlinear. Furthermore, a distinct correspondence was observed between the nonlinearity of the peak shear strength envelope, with respect to increasing matric suction, and the soil-water retention properties of the clayey soil. Results, in general, suggest that a conceptual residual shear strength framework for unsaturated soils, similar to that postulated for peak shear strength, can eventually be formulated as more experimental evidence of this kind is made available.
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Vilar, Orencio Monje. "A simplified procedure to estimate the shear strength envelope of unsaturated soils." Canadian Geotechnical Journal 43, no. 10 (October 1, 2006): 1088–95. http://dx.doi.org/10.1139/t06-055.
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Procedures that allow the prediction of some properties of unsaturated soils or the minimization of the number of tests needed to measure them are advantageous because the control of suction during testing is a formidable task that is time consuming and involves a great degree of expertise. A simplified procedure is proposed in this paper to estimate the shear strength of an unsaturated soil. The procedure is based on an empirical hyperbolic function that has been successfully used to fit experimental data. The function requires two input values, namely the shear strength of a saturated sample and the shear strength of an air-dried sample tested without the need for suction control. Samples tested under a controlled suction larger than the maximum suction expected in the problem can, alternatively, replace the air-dried samples. Both alternatives were tested against results for various soils reported in the literature. The good agreement between the estimates and the experimental data indicates that the proposed procedure is promising and reliable for estimating preliminary unsaturated shear strength parameters.Key words: unsaturated soil, suction, shear strength, prediction, laboratory tests.
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Kabošová, Lenka, Isak Foged, Stanislav Kmeť, and Dušan Katunský. "Hybrid design method for wind-adaptive architecture." International Journal of Architectural Computing 17, no. 4 (November 8, 2019): 307–22. http://dx.doi.org/10.1177/1478077119886528.
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The linkage of individual design skills and computer-based capabilities in the design process offers yet unexplored environment-adaptive architectural solutions. The conventional perception of architecture is changing, creating a space for reconfigurable, “living” buildings responding, for instance, to climatic influences. Integrating the element of wind to the architectural morphogenesis process can lead toward wind-adaptive designs that in turn can enhance the wind microclimate in their vicinity. Geometric relations coupled with material properties enable to create a tensegrity-membrane structural element, bending in the wind. First, the properties of such elements are investigated by a hybrid method, that is, computer simulations are coupled with physical prototyping. Second, the system is applied to basic-geometry building envelopes and investigated using computational fluid dynamics simulations. Third, the findings are transmitted to a case study design of a streamlined building envelope. The results suggest that a wind-adaptive building envelope plays a great role in reducing the surface wind suction and enhancing the wind microclimate.
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Wang, Zhi Yun, Mao Tian Luan, and Lu Shen. "Bearing Capacity of Suction Caisson Foundations Using FEM Analysis." Advanced Materials Research 243-249 (May 2011): 2112–15. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2112.
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To understand features of bearing capacity of suction caisson foundation is one of the key issues in design and construction of deep-water marine structures. In this paper, the general-purpose finite element analysis package ABAQUS is employed to conduct three-dimensional numerical analyses on load-carrying features of suction caisson foundation under vertically uplift load, horizontal load and moment. Then the ultimate bearing capacity of suction caisson foundation for undrained condition of the soil is evaluated by displacing-controlling procedure. Moreover, three-dimensional failure envelope of suction caisson foundation under combine loading condition are established by the proposed numerical procedure.
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Hoyos, Laureano, Roya Davoodi-Bilesavar, Ujwalkumar Patil, Jairo Yepes-Heredia, Diego Pérez-Ruiz, and José Cruz. "Behavior of unsaturated cohesive-frictional soils over a whole range of suction/thermo-controlled stress paths and modes of deformation." Soils and Rocks 44, no. 3 (July 20, 2021): 1–12. http://dx.doi.org/10.28927/sr.2021.066621.
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The present work documents some of the most recent experimental evidence of the thermohydro-mechanical behavior of compacted soils over a whole range of suction- and/or thermo-controlled stress paths and modes of deformation, including data from a series of triaxial, true triaxial, plane strain, ring shear, and resonant column tests conducted on different types of cohesive-frictional soils in the low-to-medium matric suction range under either room temperature or thermally controlled conditions. The work has been accomplished at the Advanced Geomechanics Laboratory of the University of Texas at Arlington, focusing primarily on the following essential features of unsaturated soil behavior: (1) Loading-collapse and apparent tensile strength loci assessed from suction-controlled triaxial and true triaxial testing on clayey sand, (2) Critical state lines from suction-controlled plane strain testing on silty soil, (3) Peak and residual failure envelopes from suction-controlled ring shear testing on clayey soil, (4) Frequency response curves and cyclic stress-strain hysteretic loops from thermo-controlled, constant-water content resonant column testing on clayey soil, and (5) Residual failure envelopes from suction/thermo-controlled ring shear testing on clayey soil. The work is intended to serve as a succinct yet reasonably thorough state-of-the-art paper contribution to PanAm-UNSAT 2021: Third Pan-American Conference on Unsaturated Soils, Rio de Janeiro, Brazil, July 21-25, 2021.
Dissertations / Theses on the topic "Suction Envelop"
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Supachawarote, Chairat. "Inclined load capacity of suction caisson in clay." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0188.
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This thesis investigates the capacity and failure mode of suction caissons under inclined loading. Parametric finite element analyses have been carried out to investigate the effects of caisson geometry, loading angle, padeye depth (i.e. load attachment point), soil profile and caisson-soil interface condition. Displacement-controlled analyses were carried out to determine the ultimate limit state of the suction caissons under inclined load and the results presented as interaction diagrams in VH load space. VH failure interaction diagrams are presented for both cases where the caisson-soil interface is fully-bonded and where a crack is allowed to form along the side of the caisson. An elliptical equation is fitted to the normalised VH failure interaction diagram to describe the general trend in the case where the caisson-soil interface is fully-bonded. Parametric study reveals that the failure envelope in the fully-bonded case could be scaled down (contracted failure envelope) to represent the holding capacity when a crack is allowed to form. A stronger effect of crack on the capacity was observed in the lightly overconsolidated soil, compared to the normally consolidated soil. The sensitivity of caisson capacity to the changes in load attachment position or loading angle was quantified based on the load-controlled analyses. It was found that, for caisson length to diameter ratios of up to 5, the optimal centreline loading depth (i.e. where the caisson translates with no rotation) is in the range 0.65L to 0.7L in normally consolidated soil, but becomes shallower for the lightly overconsolidated soil profile where the shear strength profile is more uniform. The reduction of holding capacity when the padeye position is shifted from the optimal location was also quantified for normally consolidated and lightly overconsolidated soil profiles at loading angle of 30 [degrees]. Upper bound analyses were carried out to augment the finite element study. Comparison of holding capacity and accompanying failure mechanisms obtained from the finite element and upper bound methods are made. It was found that the upper bound generally overpredicted the inclined load capacity obtained from the finite element analyses especially for the shorter caisson considered in this study. A correction factor is introduced to adjust the upper bound results for the optimal condition. Comparisons of non-optimal capacity were also made and showed that the agreement between the upper bound and finite element analyses are sensitive to the change in the centreline loading depth when the caisson-soil interface is fully bonded, but less so when a crack forms.
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"A Soil Suction-Oedometer Method and Design Soil Suction Profile Recommendations for Estimation of Volume Change of Expansive Soils." Doctoral diss., 2019. http://hdl.handle.net/2286/R.I.53773.
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abstract: The experience base of practitioners with expansive soils is largely devoid of directly measured soil suction. This historical lack of soil suction measurement represents an impediment to adoption of modern unsaturated soil engineering to problems of expansive soils. Most notably, soil suction-based analyses are paramount to proper design of foundations in expansive soils. Naturally, the best method to obtain design suction profiles is to perform an appropriate geotechnical investigation that involves soil moisture change-appropriate drilling depths, sampling intervals, and requisite laboratory testing, including suction measurement. However, as practitioners are slow to embrace changes in methodology, specifically regarding the adoption of even relatively simple suction measurement techniques, it has become imperative to develop a method by which the routine geotechnical procedures currently employed can be used to arrive at acceptable approximations of soil suction profiles.
Herein, a substitute, or surrogate, for soil suction is presented, such that the surrogate agrees with observed field soil suction patterns and provides estimates of soil suction that are acceptable for use in practice. Field investigations with extensive laboratory testing, including direct suction measurement, are used in development of the soil suction surrogate. This surrogate, a function of water content and routinely measured soil index properties, is then used in estimation of field expansive soil suction values. The suction surrogate, together with existing geotechnical engineering reports, is used to augment the limited existing database of field soil suction profiles. This augmented soil suction profile database is used in development of recommendations for design suction envelopes and design suction profiles. Using the suction surrogate, it is possible to proceed from the beginning to the end of the Suction-Oedometer soil heave/shrinkage analysis without directly measuring soil suction. The magnitude of suction surrogate-based heave estimates is essentially the same as heave estimates obtained using direct soil suction measurements.
The soil suction surrogate-based approach, which uses a complete-stress-state approach, considering both net normal stress and soil suction, is an intermediate step towards the adoption of unsaturated soil engineering in expansive soils analyses, wherein direct soil suction measurements are routinely made.Dissertation/Thesis
Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019
Conference papers on the topic "Suction Envelop"
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Yuan-Hung, Kuo, and Wei Bo-Siou. "Suction Pile Allowable Suction Pressure Envelopes Based on Soil Failure and Structural Buckling." In Offshore Technology Conference. Offshore Technology Conference, 2015. http://dx.doi.org/10.4043/25687-ms.
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Pelerin, Jean-Luc, David Terribile, Emmanuel Sergent, and Gerard Fernandez. "Suction Pile Splash Zone Crossing Modelling." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-19089.
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Abstract One of the critical phases that drive allowable seastates during suction pile installation is the splash zone crossing (SPZC). Offshore experience shows that anticipated loads and slack events are often over predicted, which directly affect installation vessel operability. If conservatism is required to prevent damaging installation assets, a better risk balance is required to avoid unnecessary asset stand-by. Despite the above, basin tests have shown that the peak load/slack criteria can also be under-estimated with the current methodology which may lead to a dangerous situation offshore. Because the applicable methodology is regardless of the installation crane capacity (i.e. slack) and because it does not account for the entrapped water dynamics, it cannot accurately predict the loads on the crane. We present here a physics based model of the free surface inside the suction pile that provides the loads applied on the crane while crossing the splash zone. This allows mitigation to be incorporated from day-1 of design phase and avoid late change from installation contractor while pile are fabricated and increase their vessel operability in the meantime. The model accounts for the entrapped air compressibility, the air/water flow through the pile openings, the vessel motion and the surrounding wave field. The numerical implementation has been performed in Python and packaged as an Orcaflex module. Some of the model physical parameters such as the opening pressure drop coefficients have been derived with the help of CFD. The impact of the free surface on the pile top cap is modelled as a polynomial function of the impact velocity and the coefficients values have been derived using CFD. The model has been validated against model tests and compared to field measurements and observations. The numerical results have shown good agreement with both model tests and offshore measurements at a qualitative level (the observed phenomenon are properly reproduced) and at a quantitative level. The application of the validated model to projects will allow broadening of the operating envelope and the optimization of the installation vessel planning by reducing the standby time. This new methodology shows some high potential and could be applied to projects on a more regular basis.
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Xu, ZHANG. "Load bearing analysis of suction bucket structure and analysis of foundation envelope under different loading modes." In 2021 2nd International Conference on Big Data and Informatization Education (ICBDIE). IEEE, 2021. http://dx.doi.org/10.1109/icbdie52740.2021.00051.
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Kay, S., and E. Palix. "Caisson Capacity in Clay: VHM Resistance Envelope: Part 3—Extension to Shallow Foundations." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49077.
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Suction embedded caissons are efficient and economic solutions to anchor floating structures. A more recent caisson application is to support seafloor structures such as manifolds, PLEMs, pumps, etc. For a deepwater hydrocarbon field, many types of seafloor structures are required, each with their own characteristics and slightly different design. Caisson designs increasingly use resistance envelope methodology. This eliminates non-linear 3D FE analyses (except for assessing responses or soil reactions), and facilitates probabilistic and optimisation analyses. In general, there is a requirement for a reliable method of assessing caisson capacity under general VHM load. Resistance envelope equations for “deep” circular caissons (1.5 < L/D < 6) have been presented by Kay and Palix (2010) for a wide range of soil undrained shear strength profiles. This paper extends the study to cover near-surface caissons (i.e. 0 ≤ L/D ≤ 1.5). As in previous studies, a quasi 3D non-linear finite element program (HARMONY) was the primary numerical analysis tool. Three soil shear strength profiles were investigated for 13 caisson embedment ratios. In the range 0 ≤ L/D ≤ 1.5, VHM envelope shapes transform from a “scallop” at L/D ≈ 0 into a “tongue” above a critical caisson embedment ratio (L/D)crit of about 0.5 The equations originally developed for the rotated ellipse/ellipsoid (i.e. “tongue”-shaped envelope) in Kay and Palix (2010) for L/D ≤ 1.5 have been extended for (L/D)crit ≥ L/D. All parameters are simple functions of L/D and soil shear strength profile. Major limitations and assumptions made were (a) foundation-soil tension was permitted and (b) no internal scoop failure (i.e. within the soil plug inside the caisson) was possible. These are important for low L/D: both may adversely affect VHM resistance.
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Parbat, Sarwesh, Li Yang, Minking Chyu, Sin Chien Siw, and Ching-Pang Lee. "Numerical Study of Heat Transfer in Novel Wavy Trailing Edge Design for Gas Turbine Airfoils." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91123.
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Abstract The strive to achieve increasingly higher efficiencies in gas turbine power generation has led to a continued rise in the turbine inlet temperature. As a result, novel cooling approaches for gas turbine blades are necessary to maintain them within the material’s thermal mechanical performance envelope. Various internal and external cooling technologies are used in different parts of the blade airfoil to provide the desired levels of cooling. Among the different regions of the blade profile, the trailing edge (TE) presents additional cooling challenges due to the thin cross section and high thermal loads. In this study, a new wavy geometry for the TE has been proposed and analyzed using steady state numerical simulations. The wavy TE structure resembled a sinusoidal wave running along the span of the blade. The troughs on both pressure side and suction side contained the coolant exit slots. As a result, consecutive coolant exit slots provided an alternating discharge between the suction side and the pressure side of the blade. Steady state conjugate heat transfer simulations were carried out using CFX solver for four coolant to mainstream mass flow ratios of 0.45%, 1%, 1.5% and 3%. The temperature distribution and film cooling effectiveness in the TE region were compared to two conventional geometries, pressure side cutback and centerline ejection which are widely used in vanes and blades for both land-based and aviation gas turbine engines. Unstructured mesh was generated for both fluid and solid domains and interfaces were defined between the two domains. For turbulence closer, SST-kω model was used. The wall y+ was maintained < 1 by using inflation layers at all the solid fluid interfaces. The numerical results depicted that the alternating discharge from the wavy TE was able to form protective film coverage on both the pressure and suction side of the blade. As a result, significant reduction in the TE metal was observed which was up to 14% lower in volume averaged temperature in the TE region when compared to the two baseline conventional configurations.
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Winka, James R., Joshua B. Anderson, David G. Bogard, Michael E. Crawford, and Emily J. Boyd. "Convex Curvature Effects on Film Cooling Adiabatic Effectiveness." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95243.
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Surface curvature is known to have significant effects on film cooling performance, with convex curvature inducing increased film effectiveness and concave curvature causing decreased film effectiveness. Generally, these curvature effects have been presumed to scale with 2r/d at the film cooling hole location, where r is the radius of curvature and d is coolant hole diameter. In this study, the validity of this scaling of curvature effects are examined by performing experiments in regions of large and low curvature on a model vane. Single rows of cylindrical holes were placed at various locations along the high curvature section of the suction side of the vane. For the first series of experiments, a single row of holes was placed at two locations with different local surface curvature. The coolant hole diameters were then adjusted to match 2r/d values. Results from these experiments showed that there was better correspondence of film performance when using the 2r/d scaling, but there was not an exact matching of performance. A second series of experiments focused on evaluating the effects of curvature downstream of the coolant holes. One row of holes was placed at a position upstream of the highest curvature, while another row was placed at a downstream position such that the radius of curvature was equivalent for the two rows of holes. Results indicated that the local radius of curvature is not sufficient in understanding the performance of film cooling. Instead, the curvature envelope downstream of the coolant holes plays a significant role on the performance of film cooling for cylindrical holes.
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Fletcher, Nathan, Christopher R. Marks, and Molly H. Donovan. "Secondary Flow Response to Endwall Jets in a Low Pressure Turbine." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15284.
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Abstract Due to the significant losses contributed by the secondary flow features, an active flow control system was implemented in a low-pressure turbine linear cascade which consisted of localized endwall jets with small mass ratios to perturb the dominant passage vortex. Benefits included significant area-averaged total pressure loss reduction and improved exit angle deviations which help to open the design envelope to application of high-lift front-loaded blades. This report looks to reveal the impact of steady and pulsed endwall blowing on the secondary flow dynamics. High-speed stereoscopic particle image velocimetry for an in-passage measurement plane was utilized to investigate the time-dependent behavior of key flow features such as the passage vortex. At baseline conditions, the passage vortex is characterized by time-varying oscillatory motion in the pitchwise direction, streamwise undulation, bursting, and fluctuating strength. Upon actuation of endwall jets, some of these defining dynamics of key flow features were greatly affected. A complementary investigation of the endwall jets mounted outside of a turbine environment in order to study the emitted structures at varying conditions was used to explain the observations found in the turbine passage. Insights into the secondary flow responsiveness demonstrated that loss reduction was realized by inducing reduced coherence of the passage vortex. Despite pulsed blowing at discrete frequencies associated with the passage vortex, there was no indication that instability excitation was exploited. Rather, the endwall jets acted as a periodic shape-change to the endwall which weakened the passage vortex and forced it closer to the suction-surface.
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Frosina, Emma, Adolfo Senatore, Assunta Andreozzi, Gianluca Marinaro, Dario Buono, Gennaro Bianco, Domenico Auriemma, Francesco Fortunato, Fulvio Damiano, and Pino Giliberti. "Study of the Sloshing in a Fuel Tank Using CFD and EFD Approaches." In ASME/BATH 2017 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fpmc2017-4337.
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This paper is focused on the study of the sloshing in the fuel tank of vehicles. As well known, fluid dynamic in an automotive fuel tank have to be studied and optimized to allow the correct fuel suction in all driving conditions, prevent undesired slosh noise and limit its influence on fuel vapor formation and management. Experimentation to predict the sloshing with a good accuracy depends on the ability to replace real working parameters and conditions like accelerations, decelerations, slope variations and rotations. This paper shows results obtained studying the sloshing inside a reference tank with computational fluid-dynamic and experimental approaches. The test bench for automotive fuel tank, employed in this analysis, has been designed by Moog Inc. on specification from Fiat Chrysler Automobiles and it is aimed at covering the wider possible range of dynamic conditions. It basically consists of a hexapod, which uses six independent actuators arranged in three triangles and connecting a base and a top platform, thus allowing all six DOFs. Above the top platform is mounted a tilt table with two additional actuators, to extend pitch and roll envelope, thus the name of “8-DOF bench”. A dedicated CFD model has been built up using a CFD commercial code. The model has been integrated with the multiphase tool in order to correctly reply the real free surface. Results, numerical and experimental, have been post-processed with Matlab® comparing percentage gaps of the free surfaces each other. The comparison has shown a good agreement. This research is the result of a scientific collaboration between the Industrial Engineering Department of University of Naples Federico II and FCA Fiat Chrysler Automobiles.
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Lázaro, Benigno J., Ezequiel González, David Cadrecha, Antonio Antoranz, and Jorge Parra. "Low Reynolds Number Response of High Efficiency, Intermediate Pressure Compressor Profiles." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63283.
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Current trends on intermediate pressure, axial compressors designs for aeroengine applications demand to extend their operation envelope into low Reynolds number regimes, of the order of 105 based on the real chord and inlet velocity (Re). In this range, a very limited open experimental database on profile performance can be found. Furthermore, in order to propose high efficiency designs for this regime, it is critical to determine and to understand the profile behaviour with respect to different operating parameters. In this work, a detailed experimental study of a proposed high efficiency, intermediate pressure compressor aerofoil has been carried out, both for design and off-design flow incidences, in the range 1.5 · 105 < Re < 3.5 · 105,. The experimental facility is a low-speed linear cascade where different boundary suction strategies have been implemented to optimize the flow periodicity and to minimize pressure gradient perturbations induced by end-wall secondary flow development, in an effort to ensure high quality, 2D passage flow evolution both at design and significant off-design incidences. High resolution total pressure loss and LDV traverses performed at different streamwise locations have been carried out to describe the flow evolution. The characterizations performed at close to nominal incidence give a profile loss dependence on the Reynolds number that exhibits two clearly differentiated ranges, with the lower one exhibiting a higher profile loss dependence on the Reynolds number. At large off-design incidences, the profile loss coefficient practically becomes independent of the Reynolds number, rapidly increasing as the incidence is increased. In both cases physical arguments and scaling laws based on the experimental evidence are proposed to explain the profile behavior. RANS and URANS based CDF simulations have been also conducted, showing their ability and limitations to capture the experimentally observed aerofoil behavior.
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Saavedra, J., and G. Paniagua. "Transient Performance of Separated Flows: Characterization and Active Flow Control." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75128.
Full textAbstract:
The aerothermal performance of the low pressure turbine in UAVs’ is significantly abated at high altitude, due to boundary layer separation. During past years different flow control strategies have been proposed to prevent boundary layer separation, such as dielectric barrier discharges, synthetic jets, vortex generators. However, the optimization of the control approach requires a better characterization of the separated regions at several frequencies. The present investigation analyzes the behavior of separated flows, and specifically reports the inception, reattachment and separation length, that allows the development of more efficient methods to manipulate flow separation under non-tempo-rally uniform inlet conditions. The development of separated flows under sudden flow accelerations or pulsating inlet conditions were investigated with series of numerical simulations including Unsteady Reynolds Average Navier Stokes and Large Eddy Simulations. The present research was performed on a wall mounted hump, which imposes an adverse pressure gradient representative of the suction side of low pressure turbines. The heat transfer and wall shear stresses were fully documented, as well as the flow velocity and temperature profiles at different axial locations to characterize the near wall flow properties and the thermal boundary layer. Through a sudden flow acceleration we looked into the dynamic response of the shear layer detachment as it is modulated by the mean flow evolution. Similarly, we studied the behavior of the recirculation bubble under periodic disturbances imposed by sinusoidal inlet total pressure signals at various frequencies ranging from 10 to 500 Hz. During each period the Reynolds number oscillates between 40000 and 180000 (based on a characteristic length of 0.1 m). Finally, as a first step into the flow control approach we added a slot in our geometry to allow flow injection and ingestion just upstream of the separation inception. Exploring the behavior of the separated region at different slot pressure conditions we defined the envelope for its periodic actuation. Thanks to that analysis, we found that matching the actuator frequency with the frequency response of the separated region the performance of the actuation is boosted.