Letteratura scientifica selezionata sul tema "Expansion pipe flow"
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Articoli di riviste sul tema "Expansion pipe flow"
1
Togun, Hussein, Tuqa Abdulrazzaq, Salim Kazi e Ahmad Badarudin. "Augmented of turbulent heat transfer in an annular pipe with abrupt expansion". Thermal Science 20, n. 5 (2016): 1621–32. http://dx.doi.org/10.2298/tsci140816138t.
Testo completoAbstract (sommario):
This paper presents a study of heat transfer to turbulent air flow in the abrupt axisymmetric expansion of an annular pipe. The experimental investigations were performed in the Reynolds number range from 5000 to 30000, the heat flux varied from 1000 to 4000 W/m2, and the expansion ratio was maintained at D/d=1, 1.25, 1.67 and 2. The sudden expansion was created by changing the inner diameter of the entrance pipe to an annular passage. The outer diameter of the inner pipe and the inner diameter of the outer pipe are 2.5 and 10 cm, respectively, where both of the pipes are subjected to uniform heat flux. The distribution of the surface temperature of the test pipe and the local Nusselt number are presented in this investigation. Due to sudden expansion in the cross section of the annular pipe, a separation flow was created, which enhanced the heat transfer. The reduction of the surface temperature on the outer and inner pipes increased with the increase of the expansion ratio and the Reynolds number, and increased with the decrease of the heat flux to the annular pipe. The peak of the local Nusselt number was between 1.64 and 1.7 of the outer and inner pipes for Reynolds numbers varied from 5000 to 30000, and the increase of the local Nusselt number represented the augmentation of the heat transfer rate in the sudden expansion of the annular pipe. This research also showed a maximum heat transfer enhancement of 63-78% for the outer and inner pipes at an expansion ratio of D/d=2 at a Re=30000 and a heat flux of 4000W/m2.
2
Sherza, Jenan S. "Theoretical Investigation of The Major and Minor Losses in Pipes and Fittings". Babylonian Journal of Mechanical Engineering 2024 (20 marzo 2024): 12–18. https://doi.org/10.58496/bjme/2024/003.
Testo completoAbstract (sommario):
The present study aims to investigate major pressure losses in pipes and minor losses in certain pipe fittings, such as sudden expansion. Initially, the relationships for calculating major and minor losses were derived by applying Bernoulli's equation to the studied components. Flow velocity, pipe diameter, and pipe length effects on major losses were examined. Additionally, the impact of velocity on minor losses in sudden expansion was analysed. The results demonstrated that major losses, represented by friction, significantly vary with changes in flow velocity, pipe diameter, and pipe length. It was found that increasing the pipe diameter by 200% leads to a 6% reduction in major losses. Moreover, increasing the length and velocity results in proportional increases in major losses. Regarding minor losses, the findings indicated that these losses in sudden expansion increase by a factor of six with the increase in velocity.
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LI, X. F., G. H. TANG, T. Y. GAO e W. Q. TAO. "SIMULATION OF NEWTONIAN AND NON-NEWTONIAN AXISYMMETRIC FLOW WITH AN AXISYMMETRIC LATTICE BOLTZMANN MODEL". International Journal of Modern Physics C 21, n. 10 (ottobre 2010): 1237–54. http://dx.doi.org/10.1142/s0129183110015804.
Testo completoAbstract (sommario):
Axisymmetric flow is of both fundamental interest and practical significance. A recently derived axisymmetric lattice Boltzmann model [J. G. Zhou, Phys. Rev. E78, 036701 (2008)] is adopted for studying several typical axisymmetric flows. First, the Hagen–Poiseuille flow in circular pipes is validated and the Poiseuille flow in annular cylinders is studied under different values of the radius ratio. Second, pulsatile flow in an axisymmetric pipe with a sinusoidal pressure gradient is conducted. Third, flows through pipes with various constrictions or expansions are discussed. Finally, we extend the axisymmetric lattice Boltzmann method for non-Newtonian flow. It is found that the obtained numerical results agree well with available analytical solutions. It is also observed that constriction or expansion in a pipe influences the velocity distribution of the flow significantly. In addition, the results demonstrate that the modified axisymmetric lattice Boltzmann model is capable of handling non-Newtonian flow.
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Khezzar, L., J. H. Whitelaw e M. Yianneskis. "Round Sudden-Expansion Flows". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 200, n. 6 (novembre 1986): 447–55. http://dx.doi.org/10.1243/pime_proc_1986_200_154_02.
Testo completoAbstract (sommario):
This paper describes an experimental investigation of the water flows through one axisymmetric and two asymmetric round sudden expansions from a 48 mm to an 84 mm diameter pipe and eccentricities of the pipe axes of 0, 5 and 15 mm respectively. Flow visualization revealed the presence of vortex rings downstream of the plane of expansion for transitional Reynolds numbers (Re, based on the upstream pipe diameter and bulk flow velocity) and reattachment lengths were determined in the Reynolds number range 120–40 000 for all three cases. Detailed measurements of the three mean velocity components and corresponding fluctuations were obtained by laser anemometry for Re = 40000. Wall static pressure measurements are also presented. The results show that asymmetry of the inlet geometry strongly influences the distribution of mean and turbulence quantities downstream of the expansion and results in three-dimensional reattachment. In all three flows, the mean flow was nearly uniform and the turbulence nearly homogeneous at distances of seven diameters of the large pipe downstream of the expansion. Higher levels of turbulence were found in the asymmetric ducts with maxima twice those in the axisymmetric duct.
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Hayashi, Thamy C., Isabel Malico e J. F. C. Pereira. "Analysis of the Flow at the Interface of a Porous Media". Defect and Diffusion Forum 283-286 (marzo 2009): 616–21. http://dx.doi.org/10.4028/www.scientific.net/ddf.283-286.616.
Testo completoAbstract (sommario):
The influence of inserting ceramic foam in a pipe with a 1:4 sudden expansion was numerical investigated. The foam, with a thickness to diameter ratio of 0.60, was positioned at different distances from the sudden pipe expansion wall. Three different porosities were analyzed (10, 20 and 60 pores per inch) for pore Reynolds numbers in the range of 20-400, corresponding to pipe Reynolds numbers of 2400 to 22000 in the pipe section upstream the sudden expansion. Predictions of the sudden pipe expansion cavity assuming laminar flow within the foam yield the penetration of the separated flow region into the foam. Considering turbulent flow in the porous foam and the model of Pedras and Lemos [14] prevents this penetration. The numerical and physical models used could not reproduce completely the foam influence on the separated turbulent flow region between the sudden pipe expansion and the foam inlet.
6
Kaewchoothong, Natthaporn, Makatar Wae-Hayee, Passakorn Vessakosol, Banyat Niyomwas e Chayut Nuntadusit. "Flow and Heat Transfer Characteristics of Impinging Jet from Expansion Pipe Nozzle with Air Entrainment Holes". Advanced Materials Research 931-932 (maggio 2014): 1213–17. http://dx.doi.org/10.4028/www.scientific.net/amr.931-932.1213.
Testo completoAbstract (sommario):
Flow and heat transfer characteristics of impinging jet from expansion pipe were experimentally and numerically investigated. The expansion pipe nozzle was drilled on expansion wall for increasing an entrainment of ambient air into a jet flow. The diameter of round pipe nozzle was d=17.2 mm and the diameter of expansion pipe was fixed at D=68.8 mm (=4d). The number of air entrainment holes was varied at 4, 6 and 8 holes, and the expansion pipe length was examined at L= 2d, 4d and 6d. In this study, the expansion pipe exit-to-plate distance was fixed at H=2d and the Reynolds number of jet was studied at Re=20,000. Temperature distribution on the impinged surface was acquired by using an infrared camera. The numerical simulation was carried out to reveal the flow field. The results show that the ambient air enters through the holes and subsequently blocked the entrainment of ambient air into the jet flow. It causes to enhance the heat transfer particularly at stagnation point higher than the case of conventional pipe: 4.68% for 4 holes at L=2d, 6.4% and 6.28% for 4 holes and without holes at L=4d and 5.48% for 8 holes at L=6d.
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Topakoglu, H. C., e M. A. Ebadian. "Viscous laminar flow in a curved pipe of elliptical cross-section". Journal of Fluid Mechanics 184 (novembre 1987): 571–80. http://dx.doi.org/10.1017/s0022112087003021.
Testo completoAbstract (sommario):
In this paper, the analysis on secondary flow in curved elliptic pipes of Topakoglu & Ebadian (1985) has been extended up to a point where the rate-of-flow expression is obtained for any value of flatness ratio of the elliptic cross-section. The analysis is based on the double expansion method of Topakoglu (1967). Therefore, no approximation is involved in any step other than the natural limitation of the finite number of calculated terms of the expansions. The obtained results are systematically plotted against the curvature of centreline of the curved pipe for different values of Reynolds number.
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Sisavath, Sourith, Xudong Jing, Chris C. Pain e Robert W. Zimmerman. "Creeping Flow Through an Axisymmetric Sudden Contraction or Expansion". Journal of Fluids Engineering 124, n. 1 (18 ottobre 2001): 273–78. http://dx.doi.org/10.1115/1.1430669.
Testo completoAbstract (sommario):
Creeping flow through a sudden contraction/expansion in an axisymmetric pipe is studied. Sampson’s solution for flow through a circular orifice in an infinite wall is used to derive an approximation for the excess pressure drop due to a sudden contraction/expansion in a pipe with a finite expansion ratio. The accuracy of this approximation obtained is verified by comparing its results to finite-element simulations and other previous numerical studies. The result can also be extended to a thin annular obstacle in a circular pipe. The “equivalent length” corresponding to the excess pressure drop is found to be barely half the radius of the smaller tube.
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Chang, K. C., W. D. Hsieh e C. S. Chen. "A Modified Low-Reynolds-Number Turbulence Model Applicable to Recirculating Flow in Pipe Expansion". Journal of Fluids Engineering 117, n. 3 (1 settembre 1995): 417–23. http://dx.doi.org/10.1115/1.2817278.
Testo completoAbstract (sommario):
A modified low-Reynolds-number k-ε turbulence model is developed in this work. The performance of the proposed model is assessed through testing with fully developed pipe flows and recirculating flow in pipe expansion. Attention is specifically focused on the flow region around the reattachment point. It is shown that the proposed model is capable of correctly predicting the near-wall limiting flow behavior while avoiding occurrence of the singular difficulty near the reattachment point as applying to the recirculating flow in sudden-expansion pipe.
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Baughn, J. W., M. A. Hoffman, R. K. Takahashi e Daehee Lee. "Heat Transfer Downstream of an Abrupt Expansion in the Transition Reynolds Number Regime". Journal of Heat Transfer 109, n. 1 (1 febbraio 1987): 37–42. http://dx.doi.org/10.1115/1.3248064.
Testo completoAbstract (sommario):
The heat transfer downstream of an axisymmetric abrupt expansion in a pipe in the transition Reynolds number regime has been investigated experimentally. In these experiments the wall of the downstream pipe was heated to give a constant heat flux into the air flow. The ratio of the upstream to downstream pipe diameters was 0.8 and the downstream Reynolds number ranged from 1420 to 8060. Within a narrow range of Reynolds numbers, around 5000, the position of the maximum Nusselt number was found to shift considerably. This interesting behavior may be associated with the flow instabilities in sudden expansions which have been observed by others.
Tesi sul tema "Expansion pipe flow"
1
Selvam, Kamal. "Transition to turbulence in circular expansion pipe flow". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMLH32/document.
Testo completoAbstract (sommario):
La thèse traite de recherches numériques et expérimentales sur l’écoulement à traves des conduites circulaires ou des tubes avec une petite entrée et un diamètre de sortie plus grand, parfois appelées élargissement ou divergents. L’écoulement dans un élargissement est globalement stable pour des nombres de Reynolds élevés. Ainsi la simulation numérique de ce type d’écoulement nécessite de grands domaines de calcul contenant la zone de recirculation, qui croît linéairement. En outre, les études expérimentales dans les élargissements brusques indiquent que la transition se produit à des nombres de Reynolds plus faibles que prévue par la théorie linéaire de stabilité. La raison pour cette transition précoce est due à la présence d’imperfections dans le dispositif expérimental, qui agit comme une perturbation d’amplitude finie de l’écoulement. Des simulations numériques directes des équations de Navier-Stokes ont été réalisées avec deux types différents de perturbations (i) l’inclination et (ii) le vortex. Tout d’abord, la perturbation de type inclinaison, qui est appliqué à l’entrée, crée une zone de recirculation asymétrique, puis se casse pour former une turbulence localisée en aval de l’expansion. Deuxièmement, la perturbation de type vortex, crée des structures qui ressemblent à un mode azimutal d’ordre inférieur, déjà identifié comme une perturbation optimale amplifiée. Il croît en raison de l’instabilité convective, puis forme une tâche de turbulence localisée. Enfin, la corrélation spatiale et la décomposition en modes propres révèlent que cette turbulence localisée obtient son énergie de l’écoulement d’entréeThe thesis deals with numerical and experimental investigations of flow through circular pipes with smaller inlet and larger outlet diameter, also known as expansion pipes. The hydrodynamic expansion pipe flow is globally stable for high Reynolds number. In order to numerically simulate these types of flows, large computational domains that could accommodate the linearly growing symmetric recirculation region is needed. Moreover, experimental studies of expansion pipe flows indicate that the transition occurs at lower Reynolds number than predicted by the linear stability theory. The reason for early transition is due to the presence of imperfections in the experimental setup, which acts as a finite-amplitude perturbation of the flow. Three-dimensional direct numerical simulations of the Navier-Stokes equations with two different types of perturbations (i) the tilt and (ii) the vortex are investigated. First, the tilt perturbation, which applied at the inlet, creates an asymmetric recirculation region and then breaks to form localised turbulence downstream the expansion section. Second, the vortex perturbation, creates structures that looks like lower order azimuthal mode, resembles an optimally amplified perturbation. It grows due to convective instability mechanism and then breaks to form localised turbulence. Spatial correlation and the proper orthogonal decomposition reveal that this localised turbulence gains it energy from the core flow coming out of the inlet pipe
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Latrech, Oussama. "Τurbulence cοntrοl in a diverging pipe flοw : Stabilizing Edge States and Reducing Energy Dissipatiοn". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMLH17.
Testo completoAbstract (sommario):
Lors de l’écoulement de fluides dans des conduites, les pertes par frottement liées à la turbulence sont responsables de la majeure partie de l’énergie consommée, représentant près de 10% de la consommation mondiale d’électricité. Afin de réduire notre empreinte énergétique, il est essentiel de développer des méthodes novatrices pour pomper les fluides de manière plus efficiente.Il est désormais bien établi que la turbulence s’organise autour d’un ensemble de solutions invariantes instables. En mettant en œuvre des stratégies de contrôle adaptées, il est possible de forcer l’écoulement à évoluer vers des régions de l’espace des phases plus favorables énergétiquement.Cette thèse porte sur la transition sous-critique vers la turbulence dans différentes configurations de conduites divergentes à l’aide de simulations numériques détaillées. Il a été observé que des angles de divergence plus importants réduisent généralement les nombres de Reynolds critiques nécessaires pour le déclenchement de la turbulence, bien que cet effet varie selon les configurations spécifiques, telles que les conduites à expansion brusque. L’influence de l’angle de divergence et du nombre de Reynolds sur la position des puffs turbulents stationnaires et des points de réattachement des zones de recirculation a également été analysée. De manière notable, des angles plus grands et des nombres de Reynolds plus élevés conduisent à une stabilisation des puffs turbulents et des points de réattachement plus proches du point d’expansion, en contraste avec la croissance linéaire des zones de recirculation observée en régime laminaire.En adoptant une approche de système dynamique, cette thèse explore également la stabilisation de l’état de moindre dissipation, connu sous le nom d’edge state, via des stratégies de contrôle par rétroaction. Bien qu’une stabilisation complète n’ait pas été atteinte, des réductions significatives de la traînée visqueuse et une amélioration de l'efficacité énergétique ont été obtenues. Dans une configuration de conduite divergente présentant une symétrie miroir, ces stratégies ont conduit à des économies d’énergie notables sur une large plage de nombres de Reynolds. À l’inverse, dans des configurations de conduites divergentes sans symétrie, l’efficacité de ces stratégies était plus restreinte et limitée à une gamme étroite de nombres de Reynolds autour du seuil de transition vers la turbulence. En outre, la robustesse et l’efficacité de ces stratégies de contrôle par rétroaction ont été évaluées dans des conditions simulant des scénarios opérationnels réels, démontrant ainsi leur potentiel d’application en milieu expérimental.Cette thèse analyse également la dynamique des edge states dans les écoulements divergents, en utilisant la méthode classique de bisection dans le cadre de la simulation numérique directe (DNS) via l'outil Nek5000. Ces techniques ont d’abord été appliquées aux conduites droites, validant ainsi les résultats de recherches précédentes et établissant une référence pour des analyses comparatives dans des géométries plus complexes. Par la suite, la méthode a été appliquée à une configuration de conduite à expansion brusque, où le suivi des edge states a révélé des défis majeurs en raison de la tendance de l’écoulement à transitionner vers un régime turbulent en raison d’une potentielle instabilité linéaire. Enfin, l’algorithme a été appliqué à une configuration à expansion graduelle, où des événements de bouffées quasi-périodiques ont été observés, déclenchant un cycle auto-entretenu de turbulence, alimenté par des mécanismes convectifs et une instabilité de la couche de cisaillementWhen driving fluids through pipes, the increased friction losses associated with turbulence are responsible for the majority of the energy used, corresponding to nearly 10 % of the global electric energy consumption. If one wants to succeed in reducing our energy footprint, discovering innovative ways to efficiently pump fluids is crucial.It is now understood that turbulence is organized around a set of unstable invariant solutions. By implementing bespoke control schemes, it is possible to force the flow into a more energetically favorable region of the phase space.This thesis focuses on the subcritical transition to turbulence in various divergent pipe configurations through detailed numerical simulations. It was found that larger divergence angles generally reduce the critical Reynolds numbers required for the onset of turbulence, though this effect varies with specific pipe configurations such as sudden expansion pipe. The influence of divergence angle and Reynolds number on the positioning of stationary turbulent puffs and the reattachment points of recirculation zones was also investigated. Notably, larger angles and higher Reynolds numbers cause both puffs and reattachment points to stabilize closer to the expansion point in contrast to the linear growth of the recirculation zones observed in laminar flow conditions.Adopting a dynamical system perspective, the thesis also examines the stabilization of the least dissipative state, known as the edge state, through feedback controls schemes. While complete stabilization was not achieved, significant reductions in viscous drag and enhanced energy efficiency were observed. In a divergent pipe configuration with mirror symmetry, these strategies resulted in substantial energy savings across a broad range of Reynolds numbers. Conversely, in full divergent pipe configurations without symmetry, the effectiveness of these strategies was more limited and restricted to a narrow range around of Reynolds number around the onset of turbulence. Moreover, the robustness and efficiency of these feedback strategies were evaluated under conditions simulating practical operational scenarios, demonstrating their potential applicability in experimental settings.This thesis also analyses the dynamics of edge states in divergent pipe flows, using classical bisection method within the DNS framework Nek5000. We applied these techniques in straight pipes, validating previous research findings and establishing a baseline for further comparative analysis in more complex geometries. Subsequently, the method was applied to a sudden expansion pipe configuration where edge tracking revealed significant challenges due to the flow’s tendency to quickly revert to turbulence due to a potential linear instability. Finally, the algorithm was applied to a gradual expansion pipe, where quasi-periodic bursting events were observed, initiating a self-sustaining cycle of turbulence driven by convective mechanisms and shear layer instability
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Blyth, Mark Gregory. "Steady flow in dividing and merging pipes". Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/7633.
Testo completo
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Jow, Shu-Ping, e 周書平. "Flow-field of Sudden-Expansion Pipe with Transverse Side-Flow". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/37486287704603687387.
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Jiang-Lin, Shih, e 施江林. "Flow field of sudden-expansion pipe with different swirling distributions". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/89319243269203069159.
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LIU, XUE-HUI, e 劉雪慧. "Numerical simulation and visualization for turbulent flow in pipe expansion". Thesis, 1988. http://ndltd.ncl.edu.tw/handle/96648043827107656101.
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Lin, Heng-Sheng, e 林恆生. "Numerical Simulation of Turbulent Separation Flow in Bend and Sudden Expansion Pipe Flow". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/88749070899273041455.
Testo completoAbstract (sommario):
碩士國立臺灣大學
應用力學研究所
87
This research employs the numerical simulation of the turbulent separation flow in bend and sudden expansion pipe. The standard k-ε model, RNG k-ε model and Reynolds Stress model are used in this study. The results will compare with the experimental data, and it shows that that RNG k-ε model yields substantially better predictions than standard k-ε model and Reynolds Stress model in these flow field. Then the RNG k-ε model is used to simulate the flow in bend with guidevane. The results show that to install guidevane in bend will eliminate the recirculation region, and provide more uniform flow in downstream. Beside, we also use the RNG k-ε model to simulate the flow of sudden expansion pipe with side injection. The results are just a small amomut of side flow intensity will change the main flow field in the sudden expansion pipe.
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Lin, chi-chen, e 林智全. "Experimental investigation of separation flow and perturbation in dden expansion pipe". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/96648012999671276695.
Testo completoAbstract (sommario):
碩士國立臺灣大學
應用力學研究所
81
The instability of the flow through axisymmetricn pipe caused by small thermal interference is experimentally studied low and high Reynolds number region in the project. The flow in region of low Reynolds number is qualitatively investigated by visualization, and the flow in the high Reynolds number is measured by LDA. An asymmetric flow structure caused by a small thermal difference the upstream and downstream of sudden- expansion pipe with only magnitude .minpl 0.15 .degree.C is found in the low speed flow time in the literature. The influential parameters for the flow the asymmetric flow include the temperature difference, the and the Reynolds number, and they are investigated in thisively. The asymmetric flow structure is very sensitive to theference between upstream and downstream of the sudden-expansion pipe, structure of asymmetric flow remains quite stable after the perturbation of pressure-wave from pipe downstream and the of momentum from the side-flow near the expansion. The separated flow becomes symmetric for the case of high Reynolds number. The reattachment length for Re=1000 .bksimlr. 100000 and the velocities in high Reynolds number (Re = 15200) is measured bynemometer. The results could be used as a data bank for the furtherand numerical modelling.
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王子銘. "The measurement and analysis of the flow in the single expansion chamber exhaust pipe". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/99674512132115855065.
Testo completoAbstract (sommario):
碩士國立中興大學
機械工程學系
87
Exhaust noise constitutes the major part of the total noise emitted from motorcycle engines, especially for two stroke engines with small displacement volume. The temporal variations of the velocity and pressure inside the exhaust pipe play an important role in determining the total sound pressure level and the spectral characteristics of exhaust noise. Usually one dimensional unsteady gasdynamic model was adopted to calculate the exhaust flow in the past. This approach worked well for exhaust pipes of simple geometry. However, high frequency components of the noise generated from exhaust flow could be underestimated for complex exhaust pipes with the conventional one dimensional approach. The objective of this research is to investigate the flow characteristics in the exhaust pipe of a small two stroke motorcycle engine. A multi dimensional flow model coupled with an engine cycle model was used instead of the conventional one dimensional model to calculate the periodic flow in exhaust pipes. Both analysis and measurements of the temporal variations of the velocity and pressure variations inside the exhaust pipe were carried out in this study. The engine cycle simulation software BOOST was adopted to model the two stroke motorcycle engine. The intake system was analyzed with one dimensional model while the crankcase and the cylinder were analyzed with zero dimensional model. A CFD package FIRE was applied to model the three dimensional periodic flow in the exhaust pipe. The three dimensional exhaust pipe model and the one/zero dimensional engine model were then combined together and the associated numerical programs were executed concurrently to obtain the periodic variations of the pressure and flow in the exhaust pipe. As in the part of measurement, a commercial moped engine was used for testing in this study. An exhaust pipe with single expansion chamber was attached to the engine exhaust port. The engine was driven with an electric motor at constant speeds. The temporal as well as the spatial variations of the flow inside the exhaust pipe were measured with a hot wire anemometer and the pressure variations were measured with pressure transducers located at several locations along the axial length of the exhaust pipe. Results of calculation of the three dimensional exhaust pipe model showed that as the flow in the exhaust pipe reached a stable periodic state, two circulating zones occurred in the expansion chamber. These two circulating zones grew and decayed sequentially and then merged together to become a large circulation at the end of an engine cycle. The process of growth and decay repeated in each engine cycle. Calculation results of the three dimensional exhaust pipe model were quite different from those of the one dimensional exhaust pipe model obtained previously. The complex flow pattern occurring inside the expansion chamber has not been observed in the results of conventional one dimensional exhaust pipe model. However, the pressure variations in the exhaust pipe obtained from the conventional one dimensional model are close to those obtained in the present study. The spatial pressure variations in the expansion chamber are within 0.1 kPa at all times during the flow period, and the pressure distribution along the length of the pipe is close to a plane wave. As in the straight pipe connecting the engine exhaust port and the muffler, the calculated velocity distribution in the present study was close to that obtained from previous one dimensional calculation. Comparing the measured data with the calculated results showed that the location and the moving speed of the circulating zones as well as the major frequency components of the velocity variations in the expansion can be predicted correctly. However, the calculated velocity amplitudes and phase angles did not agree very well with the measured data. As comparisons of the instantaneous flow at the exit of the exhaust pipe, results of the three dimensional model are closer to the measured data than those obtained from the conventional one dimensional model concerning the velocity amplitudes and phase angles. However, discrepancies of the average flow in the whole cycle still exist between the calculated results and the measured data for both the cases of one dimensional model and three dimensional model.
Libri sul tema "Expansion pipe flow"
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Sultanian, B. K. A study of sudden expansion pipe flow using an algebraic stress model of turbulence. New York: AIAA, 1986.
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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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Escudier, Marcel. Introduction to Engineering Fluid Mechanics. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.001.0001.
Testo completoAbstract (sommario):
Turbojet and turbofan engines, rocket motors, road vehicles, aircraft, pumps, compressors, and turbines are examples of machines which require a knowledge of fluid mechanics for their design. The aim of this undergraduate-level textbook is to introduce the physical concepts and conservation laws which underlie the subject of fluid mechanics and show how they can be applied to practical engineering problems. The first ten chapters are concerned with fluid properties, dimensional analysis, the pressure variation in a fluid at rest (hydrostatics) and the associated forces on submerged surfaces, the relationship between pressure and velocity in the absence of viscosity, and fluid flow through straight pipes and bends. The examples used to illustrate the application of this introductory material include the calculation of rocket-motor thrust, jet-engine thrust, the reaction force required to restrain a pipe bend or junction, and the power generated by a hydraulic turbine. Compressible-gas flow is then dealt with, including flow through nozzles, normal and oblique shock waves, centred expansion fans, pipe flow with friction or wall heating, and flow through axial-flow turbomachinery blading. The fundamental Navier-Stokes equations are then derived from first principles, and examples given of their application to pipe and channel flows and to boundary layers. The final chapter is concerned with turbulent flow. Throughout the book the importance of dimensions and dimensional analysis is stressed. A historical perspective is provided by an appendix which gives brief biographical information about those engineers and scientists whose names are associated with key developments in fluid mechanics.
Capitoli di libri sul tema "Expansion pipe flow"
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Wagner, C., e R. Friedrich. "Turbulent Flow in a Sudden Pipe Expansion". In Fluid Mechanics and Its Applications, 544–48. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0457-9_99.
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Wang, Jiao, e Yaan Hu. "Experimental Investigation of Hydrodynamics on Abrupt-Expansion Pipe Behind Control Valve of Hydro-Driven Shiplift". In Lecture Notes in Civil Engineering, 406–17. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-6138-0_36.
Testo completoAbstract (sommario):
AbstractControl valve is the special core equipment of hydro-driven ship lift, it is similar to the electric motor of the electric driven ship lift, which is the key to the safe and efficient operation of ship lift. Hydro-driven ship lift requires very high performance of control valve. It not only needs to control the flow accurately, but also to meet the needs of large flow. It is difficult to avoid cavitation for control valve to work under high pressure difference. How to control the erosion and destruction of valves and pipelines caused by cavitation is related to the operation safety and efficiency of hydro-driven ship lift. Sudden expansion of pipe behind the valve is a simple and efficient valve cavitation suppression technology. Aiming at typical control valve (plunger valve), this paper uses physical model tests and theoretical analysis to study the effect of sudden expansion of pipe behind the valve on the flow resistance characteristics of valves, and comprehensively consider the effects of valve type, flow pattern, and flow pulsation. According to the analysis, the relationship between sudden expansion ratio of the pipe and valve flow coefficient is obtained, and the test results are in good agreement with the theoretical analysis. Based on the theoretical analysis and considered the effect of cavitation defense, the expansion ratio for this type of abrupt expansion pipe is suggested to be 3.00. This study has guiding significance for the anti-cavitation technology of industrial valves, and can be used as a reference for the design of pipelines for water delivery and pressure regulation projects.
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Wagner, C., e R. Friedrich. "Reynolds stress budgets of low Reynolds number pipe expansion flow". In Advances in Turbulence VI, 51–54. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0297-8_13.
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Huang, Jun-hong, Fan Jiang e Ju Yan. "Study on Flow Characteristics of Annular Flow in Sudden Expansion and Contraction Pipe". In Proceedings of the 2022 International Petroleum and Petrochemical Technology Conference, 169–85. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2649-7_17.
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Rennels, Donald C., e Hobart M. Hudson. "Expansions". In Pipe Flow, 113–29. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118275276.ch11.
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Sommerfeld, M., H. H. Qiu e D. Koubaridis. "The Influence of Swirl on the Particle Dispersion in a Pipe Expansion Flow". In Applications of Laser Techniques to Fluid Mechanics, 142–62. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-61254-1_8.
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Terekhov, Viktor, e Maksim Pakhomov. "Numerical Simulation of Flow Structure and Heat Transfer in a Swirling Gas-Droplet Turbulent Flow Through a Pipe Expansion". In Springer Proceedings in Physics, 93–100. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-30602-5_12.
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Davidson, P. A. "Vortex Breakdown". In The Dynamics of Rotating Fluids, 321–36. Oxford University PressOxford, 2024. http://dx.doi.org/10.1093/9780191994272.003.0015.
Testo completoAbstract (sommario):
Abstract A thin vortex tube can undergo a sudden expansion, often leading to instability and turbulence, if subject to an external deceleration. This is called vortex breakdown, and it is often observed in swirling flow in a slowly diverging pipe, and in the scroll vortices that develop on the upper surface of a delta wing. Simple model problems are presented for vortex breakdown, both in pipes and on delta wings. However, attempts to develop a generalized theory of vortex breakdown have proved to be problematic, as discussed towards the end of the chapter. Indeed, despite many analytical and experimental studies, the entire subject of vortex breakdown remains somewhat uncertain.
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Wagner, C., e R. Friedrich. "A-Priori Tests of Reynolds Stress Transport Models in Turbulent Pipe Expansion Flow". In Engineering Turbulence Modelling and Experiments 4, 83–92. Elsevier, 1999. http://dx.doi.org/10.1016/b978-008043328-8/50007-2.
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Diwakar, Philip, Yuqing Liu e Ismat ElJaouhari. "Evaluation of Flange Leakage due to Thermal Bowing and Shock". In Ageing and Life Extension of Offshore Facilities, 267–74. ASME, 2022. http://dx.doi.org/10.1115/1.885789_ch21.
Testo completoAbstract (sommario):
During a flaring event, some operating conditions in an LNG plant cause liquid refrigerant to be introduced into a flare header causing large temperature gradients between the bottom and top wall and lead to vertical and lateral displacements along with rotation of the horizontal header. This thermal bowing is a serious problem with risk of flange leakage due to differential thermal expansion between bolts and flange and pipe cracks at high stress concentration location as it lifts off the supports. This paper evaluates the introduction of warm gas into the flare header to prevent a flange leakage as a mitigation attempt. This paper recounts the use of Fluid Structure Interaction (FSI) to study bowing and flange leakage mitigation. The liquid flowing from the lateral into the main header pipe is multiphase in the dispersed, stratified, slug or annular flow régime. Multiphase flows with heat transfer are analyzed using Computational Fluid Dynamics (CFD) and conjugate heat transfer for steel. The temperatures on the metal are then transferred to a Finite Element Analysis (FEA) and analyzed for thermal stresses and deformation due to bowing. Elastic plastic Service Criteria Assessment per ASME BPVC Sec-VIII, Div.2 Part 5.2.4.3 (b) is performed to calculate Von-Mises, peak stresses and derive membrane and bending stresses on the hub, bolts, and gasket. These stresses are compared to ASME standard allowable limits. Based on these results, risk of flange leakage is evaluated, and mitigations are recommended to reduce the risk.
Atti di convegni sul tema "Expansion pipe flow"
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Moallemi, Nima, e Joshua Brinkerhoff. "STATISTICS OF TURBULENT AND LAMINARIZING FLOW IN A CIRCULAR PIPE WITH A GRADUAL EXPANSION". In Tenth International Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2017. http://dx.doi.org/10.1615/tsfp10.530.
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Darihaki, Farzin, Jun Zhang e Siamack A. Shirazi. "Application of Scale-Resolving Simulations and Hybrid Models for Contraction-Expansion Pipe Flows". In ASME 2021 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/fedsm2021-65917.
Testo completoAbstract (sommario):
Abstract Contractions and expansions are commonly found in various piping systems including flow control in the oil and gas industry. They impose complex flow characteristics such as flow recirculation, boundary layer separation and unsteady re-attachment. Computational Fluid Dynamics (CFD) using RANS simulations can offer general information about the time-averaged flow properties in expansion and contraction geometries including the pressure drop across the fitting. However, they generally fail to provide details of turbulent flow such as shedding of vortices and high turbulent intensities which are observed in experimental data at the expansion and contraction regions. Large Eddy Simulations (LES) can resolve a turbulence spectrum by filtering Navir-Stokes equations over the computational cells. In this study, LES is utilized to examine a sudden-contraction and expansion pipe flow. Furthermore, Stress-Blended Eddy Simulations (SBES) as a hybrid LES-RANS model is employed for comparison. All of these Scale-Resolving Simulations (SRS) are examined against the experimental data and compared to commonly used RANS simulations. Various flow parameters are examined at different locations for a 50.8 mm pipe which is suddenly reduced to a 25.4 mm pipe and then suddenly expands to the original size, and highlights of each model are presented. The details of the turbulent flow in these geometries are critical to many applications such as particle-laden flows and this investigation would provide insight into the appropriate flow modeling in the expansion and contraction geometries.
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Beladi, Behnaz, e Hendrik C. Kuhlmann. "Flow Over a Sudden Expansion in an Annular Pipe: Steady Axisymmetric Flow and its Stability". In ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7896.
Testo completoAbstract (sommario):
The stability of the axisymmetric incompressible Newtonian flow in an annular pipe suddenly expanding radially inward is investigated. The axisymmetric steady basic flow is discretized using primitive variables and second-order finite volumes on a staggered grid. The resulting algebraic equations are solved by Newton–Raphson iteration. A three-dimensional global linear stability analysis is performed. The solutions to the linear stability problem are represented by normal modes. The generalized eigenvalue problem is solved using an implicitly restarted Arnoldi algorithm which is provided by the ARPACK library and a Cayley transformation. Stability boundaries have been computed for a range of parameters varying the outlet radius ratio. The physical instability mechanisms are studied by a an posteriori analysis of the kinetic energy transferred between the basic state and the critical mode. Neutral curves and critical modes are presented and the instability mechanisms are discussed.
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Bennett, I., A. Tourlidakis e R. L. Elder. "Detailed Measurements Within a Selection of Pipe Diffusers for Centrifugal Compressors". In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-092.
Testo completoAbstract (sommario):
It is well established that the flow between the impeller tip and the diffuser throat is very influential on the performance and flow range of a centrifugal compressor stage. Detailed measurements of a parametric selection of pipe diffusers have been carried out within this region using a combination of conventional pneumatic and high speed pressure transducers. Four pipe diffuser designs were examined. The first and datum consisted of 31 pipes, representing a design with minimal meridional step (or sidewall expansion) between impeller tip and diffuser throat. The step size was increased to 1.3 for the second design resulting in a 22 pipe diffuser. A further increase of sidewall expansion ratio to 1.7 with 13 pipes was completed following favourable results from the 22 pipe tests. The final diffuser was of hybrid design consisting of an oval rather than circular throat cross-section. This departure allowed for a 13 pipe diffuser without sidewall expansion. Flow range and performance comparisons are made in addition to detailed measurements which clearly show that strong planar pulsations dominate the distorted diffuser throat flow. Larger pressure pulsations are quantified for the designs with low numbers of pipes.
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Middelberg, J. M., T. J. Barber, S. S. Leong, K. P. Byrne e E. Leonardi. "CFD Analysis of the Acoustic and Mean Flow Performance of Simple Expansion Chamber Mufflers". In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61371.
Testo completoAbstract (sommario):
The acoustic and mean flow performance of different configurations of simple expansion chamber mufflers has been considered. The different configurations include extended inlet/outlet pipes and baffles inside the expansion section of the muffler. Both the acoustic and mean flow performance has been evaluated for each muffler. The acoustic CFD model of the muffler uses an axisymmetric grid with no mean flow and a single period sinusoid of suitable amplitude and duration imposed at the inlet boundary. The time history of the acoustic pressure and particle velocity are recorded at two points, one in the inlet pipe and the other in the outlet pipe. These time histories are Fourier transformed and the transmission loss of the muffler is calculated. The mean flow model of the muffler uses the same geometry, but has a finer mesh and has a suitable inlet velocity applied at the inlet boundary and the pressure drop across the muffler is found. The acoustic performance is compared with published experimental results.
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SULTANIAN, B., G. NEITZEL e D. METZGER. "A study of sudden expansion pipe flow using an algebraic stress model of turbulence". In 4th Joint Fluid Mechanics, Plasma Dynamics and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1986. http://dx.doi.org/10.2514/6.1986-1062.
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Pakhomov, Maksim A., e V. V. Terekhov. "Modeling of flow patterns and heat transfer in gas-droplets turbulent flow downstream of a pipe sudden expansion". In THMT-12. Proceedings of the Seventh International Symposium On Turbulence, Heat and Mass Transfer Palermo, Italy, 24-27 September, 2012. Connecticut: Begellhouse, 2012. http://dx.doi.org/10.1615/ichmt.2012.procsevintsympturbheattransfpal.130.
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Hammad, Khaled J. "Heat Transfer Enhancement in Annular Shear-Thinning Flows Over a Sudden Pipe Expansion". In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70609.
Testo completoAbstract (sommario):
Heat transfer enhancement in suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid is studied within the steady laminar flow regime. Conservation of mass, momentum, and energy equations, along with the power-law constitutive model are numerically solved. The impact of inflow inertia, annular-nozzle-diameter-ratio, k, power-law index, n, and Prandtl numbers, is reported for: Re = {50, 100}, k = {0, 0.5, 0.7}; n = {1, 0.8, 0.6}; and Pr = {1, 10, 100}. Heat transfer enhancement downstream of the expansion plane, i.e., Nusselt numbers, Nu, higher than the fully developed value, in the downstream pipe, is observed only for Pr = 10 and 100. Higher Prandtl numbers, power-law index values, and annular diameter ratios, in general, reflect a more dramatic heat transfer augmentation downstream of the expansion plane. Heat transfer augmentation for Pr = 10 and 100, is more dramatic for suddenly expanding annular flows, in comparison with suddenly expanding pipe flow. For a given annular diameter ratio and Reynolds numbers, increasing the Prandtl number from Pr = 10 to Pr = 100, always results in higher peak Nu values, for both Newtonian and shear-thinning non-Newtonian flows.
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Murase, Michio, Yoichi Utanohara, Ikuo Kinoshita, Noritoshi Minami e Akio Tomiyama. "Numerical Calculations on Countercurrent Air-Water Flow in Small-Scale Models of a PWR Hot Leg Using a VOF Model". In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75116.
Testo completoAbstract (sommario):
In the case of loss of the residual heat removal (RHR) systems under mid-loop operation during shutdown of a PWR plant, reflux cooling by a steam generator (SG) is expected, and the generated steam in a reactor core and the condensed water in the SG form a countercurrent flow in a hot leg, which consists of a horizontal pipe, an elbow and an inclined pipe. In order to improve a countercurrent flow model of a transient analysis code, countercurrent air-water tests were conducted using the 1/15th scale model of the PWR hot leg at Kobe University and the authors conducted numerical calculations of the 1/15th scale tests using the thermal-hydraulic analysis code FLUENT6.3.26 and an Euler-Euler model or a VOF model. In the tests and calculations, however, the expansion of the inclined pipe in the PWR hot leg was not simulated. In this study, using the VOF model, the authors conducted numerical calculations for a 1/15th scale model of the PWR hot leg with the expansion of the inclined pipe, which mitigates CCFL (countercurrent flow limitation) there. The calculated flow patterns in the hot leg using the VOF model were quite different with the data for the 1/15th tests without the expansion of the inclined pipe due to underestimation of CCFL characteristics at the upper end of the inclined pipe, but became similar with the observed results for the 1/15th scale model with the expansion of the inclined pipe due to the mitigation of CCFL at the inclined pipe. The results indicate that the VOF model could not correctly calculate air-water two-phase flows at the upper part of the inclined pipe but could calculate two-phase flows in the horizontal pipe.
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Hammad, Khaled J. "Annular Shear-Thinning Flow Over an Axisymmetric Sudden Expansion". In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66149.
Testo completoAbstract (sommario):
Suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid were numerically investigated within the steady laminar flow regime. The power-law constitutive equation is used to model the rheology of interest. A parametric study is performed to reveal the influence of annular diameter ratio, k, and power-law index, n, over the following range of parameters: k = {0, 0.5, 0.7} and n = {1, 0.8, 0.6}. Flow separation and entrainment, downstream of the expansion plane, creates two recirculation regions. The first is a central recirculation region between the expansion plane and the flow stagnation point along the centerline. A second, corner recirculation region forms between the expansion plane and the flow reattachment point along the wall. The results demonstrate impact of the investigated geometrical and rheological parameters on the extent and intensity of both flow recirculation regions, the wall shear stress distribution, and the evolution and redevelopment characteristics of the flow downstream the expansion plane.
Rapporti di organizzazioni sul tema "Expansion pipe flow"
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Rosenfeld, Hart e Zulfiqar. L51994 Acceptance Criteria for Mild Ripples in Pipeline Field Bends. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), settembre 2003. http://dx.doi.org/10.55274/r0010395.
Testo completoAbstract (sommario):
Field bends in large diameter pipe are routinely used in the construction of oil and gas pipelines. Mild ripples along the intrados are often unavoidable where such bends have a high D/t or high yield strength. Present regulations and industry standards differ in their treatment of mild ripples, ranging from silence to prohibition, depending upon interpretation. Consequently, the application of acceptance standards for such features is inconsistent, leading to variable standards of inspection and probable scrapping of otherwise sound bends. Finite element analysis (FEA) was used to estimate the effect of ripple magnitude and spacing on stresses due to pressure and bending. Stress concentration factors derived from the models were used with a suitable fatigue damage rule to estimate the effect of ripple parameters on service life. Results were benchmarked against the available test data. The results indicate that (1) mild or shallow ripples up to 2 percent of the pipe diameter in crest-to-trough dimension would not be expected to be harmful in gas transmission pipelines operating under conditions normally encountered in the gas transportation industry; (2) mild or shallow ripples up to 1 percent of the pipe diameter in crest-to-trough dimension would not be expected to be harmful in hazardous liquid transportation pipelines operating under conditions normally encountered in the liquid transportation industry; (3) the presence of ripples could eventually be harmful to long-term integrity in a severe cyclic loading (pressure, thermal expansion, flow-induced vibration) environment, or where soil movement could take place. Recommendations are made for ASME Code criteria specifically permitting mild ripples within stated limits.