Articoli di riviste: "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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Monprapussorn, T., C. Athisakul e S. Chucheepsakul. "Nonlinear Vibrations of an Extensible Flexible Marine Riser Carrying a Pulsatile Flow". Journal of Applied Mechanics 74, n. 4 (22 novembre 2006): 754–69. http://dx.doi.org/10.1115/1.2711226.

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The influence of transported fluid on static and dynamic behaviors of marine risers is investigated. The internal flow of the transported fluid could have a constant, a linear, or a wave velocity. The riser pipe may possibly experience the conditions of high extensibility, flexibility, and large displacements. Accordingly, the mathematical riser models should be governed by the large strain formulations of extensible flexible pipes transporting fluid. Nonlinear hydrodynamic dampings due to ocean wave–pipe interactions implicate the high degree of nonlinearity in the riser vibrations, for which numerical solutions are determined by the state–space–finite-element method. It is revealed that the impulsive acceleration of internal flow could seriously relocate the vibrational equilibrium positions of the riser pipe. The fluctuation of the pulsatile flow relatively introduces the expansion of amplitudes and the reduction of frequencies of the riser vibrations. The pulsatile frequencies of the internal flow in wave aspect could reform the oscillation behavior of the conveyor pipe.

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Abbazov, I., M. Khodjiev, A. Salimov e F. Egamberdiyev. "Investigation of air velocity in expanding and contracting pipes for the transport of fibrous materials". IOP Conference Series: Earth and Environmental Science 1142, n. 1 (1 marzo 2023): 012101. http://dx.doi.org/10.1088/1755-1315/1142/1/012101.

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Abstract Uzbekistan is implementing comprehensive measures to produce a wide range of high-quality and inexpensive textile and light industry products based on the production and deep processing of cotton fiber, which is the main textile raw material, to prevent waste and increase its competitiveness. This article, to a certain extent, serves to implement the tasks specified in the Decree of the Cabinet of Ministers dated November 25, 2018 No. 53 “On additional measures to organize the activities of cotton and textile industries and clusters” and other regulatory and legal documents related to this activity. The science of cotton transport by pneumatic transport has a long history, and with an air flow speed of more than 28 m/s, cotton is distributed more evenly over the pipe section. In it, the transportation process is carried out mainly in the suspended state of the material. With a decrease in the air flow velocity from 25.0 m/s, an analysis of the literature on the uneven distribution of material over the pipe section was carried out. It has been practically proven that an increase in the expansion angle in expanding or contracting pipes depends on air resistance, and the expansion or contraction angle depends on the speed of air movement at the point of expansion or contraction of the pipe. Therefore, the optimal value of the angle of expansion or contraction of expanding or contracting pipes was determined.

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Torii, Shuichi, e Wen-Jei Yang. "Secondary Flow Phenomena in an Axially Rotating Flow Passage with Sudden Expansion or Contraction". International Journal of Rotating Machinery 5, n. 2 (1999): 117–22. http://dx.doi.org/10.1155/s1023621x9900010x.

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This paper investigates rotational effects on secondary flow in rotating flow passages with sudden expansion or contraction. Consideration is given to laminar flow. The governing boundary-layer equations are discretized by means of a finite-difference technique and numerically solved to determine the distributions of velocity vector under the appropriate boundary conditions. The Reynolds number (Re) and rotation rate are varied to determine their effects on the formation ofsecondary flows. It is disclosed from the study that: (i) when laminar flow is introduced into an axially rotating pipe with expansion, the stretch ofthe secondary flow zone is amplified with an increase in the rotation rate and Re, and (ii) in contrast, for axially rotating pipe flows with contraction, the secondary flow region is somewhat suppressed due to pipe rotation, and the change is slightly affected by the rotation rate and Re. Results may find applications in automotive and rotating hydraulic transmission lines.

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Sun, Qi Guo, Xiong Shi Wang, Ying Wang e Zhi Hong Li. "The Characteristics of the Annular Flow through the Sudden-Expansion Pipe of the Oil-Air Lubrication System". Advanced Materials Research 889-890 (febbraio 2014): 358–62. http://dx.doi.org/10.4028/www.scientific.net/amr.889-890.358.

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The characteristics of the sudden-expansion pipe in oil-air lubrication system have been analyzed based on Fluent. The results show that the pressure and oil film mutate when the annular flow through the sudden-expansion pipe and the suddenly change of position of pressure and film is not affected by the inlet air velocity, however, the strength of pressure and film is in direct ratio with the inlet air velocity. The film of oil-air annular flow in the pipeline before the suddenly expanding part is well-distributed, but the distribution after that is widely affected by the air velocity and the pipe diameter, and furthermore the larger air velocity and pipe diameter increase the degree of dispersion of the annular flow film.

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KERSWELL, R. R., e O. R. TUTTY. "Recurrence of travelling waves in transitional pipe flow". Journal of Fluid Mechanics 584 (25 luglio 2007): 69–102. http://dx.doi.org/10.1017/s0022112007006301.

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The recent theoretical discovery of families of unstable travelling-wave solutions in pipe flow at Reynolds numbers lower than the transitional range, naturally raises the question of their relevance to the turbulent transition process. Here, a series of numerical experiments are conducted in which we look for the spatial signature of these travelling waves in transitionary flows. Working within a periodic pipe of 5D (diameters) length, we find that travelling waves with low wall shear stresses (lower branch solutions) are on a surface in phase space which separates initial conditions which uneventfully relaminarize and those which lead to a turbulent evolution. This dividing surface (a separatrix if turbulence is a sustained state) is then minimally the union of the stable manifolds of all these travelling waves. Evidence for recurrent travelling-wave visits is found in both 5D and 10D long periodic pipes, but only for those travelling waves with low-to-intermediate wall shear stress and for less than about 10% of the time in turbulent flow at Re = 2400. Given this, it seems unlikely that the mean turbulent properties such as wall shear stress can be predicted as an expansion solely over the travelling waves in which their individual properties are appropriately weighted. Instead the onus is on isolating further dynamical structures such as periodic orbits and including them in any such expansion.

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Sommerfeld, M., A. Ando e D. Wennerberg. "Swirling, Particle-Laden Flows Through a Pipe Expansion". Journal of Fluids Engineering 114, n. 4 (1 dicembre 1992): 648–56. http://dx.doi.org/10.1115/1.2910081.

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The present study concerns a particle-laden, swirling flow through a pipe expansion. A gas-particle flow enters the test section through a center tube, and a swirling air stream enters through a coaxial annulus. The swirl number based on the total inflow is 0.47. Numerical predictions of the gas flow were performed using a finite-volume approach for solving the time-averaged Navier-Stokes equations. The predicted mean velocity profiles showed good agreement with experimental results when using the standard k-ε turbulence model. The turbulent kinetic energy of the gas phase, however, is considerably underpredicted by this turbulence model, especially in the initial mixing region of the two jets. The particle dispersion characteristics in this complex flow were studied by using the Lagrangian method for particle tracking and considering the particle size distribution. The influence of the particle phase onto the fluid flow was neglected in the present stage, since only low particle loadings were considered. The particle mean velocities were again predicted reasonably well and differences between experiment and simulation were only found in the velocity fluctuations, which is partly the result of the underpredicted turbulent kinetic energy of the gas phase. The most sensitive parameter for validating the quality of numerical simulations for particle dispersion is the development of the particle mean number diameter which showed reasonable agreement with the experiments, except for the core region of the central recirculation bubble. This, however, is attributed again to the predicted low turbulent kinetic energy of the gas phase.

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Wang, Weibing, e Yongsheng Ren. "Erosion-Corrosion of AISI 302 Stainless Steel Sudden Expansion Pipes in High Salt Wastewater: Effect of Fluid Flow on Different Positions of a Sudden Expansion Pipe". Corrosion 77, n. 4 (2 febbraio 2021): 461–69. http://dx.doi.org/10.5006/3618.

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Erosion-corrosion (E-C) is common in chemical industries. Sudden expansion pipes (SEP) are one of the flow components which may experience severe erosion rates. Computational fluid dynamic modeling (CFD) and flow-through experiments were used to study E-C for a SEP of AISI 302 stainless steel. A typical geometry for SEP was investigated: 20 mm diameter inlet pipe, 40 mm diameter outlet pipe, with an inlet flow rate of 0.1 m/s, and 10 wt% concentration of SiO2. CFD simulation results showed that turbulence energy and wall shear were highest at 5 mm and fluid axial velocity was lowest at 5 mm from the inlet/outlet SEP connection point. E-C test results showed that the most severe E-C occurred between 5 mm and 7 mm downstream of the SEP. At deeper lengths into SEP, the corrosion rate decreased and remained constant. The results indicated that increasing wall shear and turbulence energy increased the mechanical effects of particles on SEP and hence increased the E-C rates of the reattachment point. This work provides a means of understanding E-C behavior and predicting erosion damage of SEP.

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Tumin, Anatoli. "Receptivity of pipe Poiseuille flow". Journal of Fluid Mechanics 315 (25 maggio 1996): 119–37. http://dx.doi.org/10.1017/s0022112096002364.

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The receptivity problem is considered for pipe flow with periodic blow–suction through a narrow gap in the pipe wall. Axisymmetric and non-axisymmetric modes (1, 2, and 3) are analysed. The method of solution is based on global eigenvalue analysis for spatially growing disturbances in circular pipe Poiseuille flow. The numerical procedure is formulated in terms of the collocation method with the Chebyshev polynomials application. The receptivity problem is solved with an expansion of the solution in a biorthogonal eigenfunction system, and it was found that there is an excitation of many eigenmodes, which should be taken into account. The result explains the non-similar character of the amplitude distribution in the downstream direction that was observed in experiments.

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Vittal Shenoy, Dhanush, Mostafa Safdari Shadloo, Jorge Peixinho e Abdellah Hadjadj. "Direct numerical simulations of laminar and transitional flows in diverging pipes". International Journal of Numerical Methods for Heat & Fluid Flow 30, n. 1 (11 luglio 2019): 75–92. http://dx.doi.org/10.1108/hff-02-2019-0111.

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Purpose Fluid flows in pipes whose cross-sectional area are increasing in the stream-wise direction are prone to separation of the recirculation region. This paper aims to investigate such fluid flow in expansion pipe systems using direct numerical simulations. The flow in circular diverging pipes with different diverging half angles, namely, 45, 26, 14, 7.2 and 4.7 degrees, are considered. The flow is fed by a fully developed laminar parabolic velocity profile at its inlet and is connected to a long straight circular pipe at its downstream to characterise recirculation zone and skin friction coefficient in the laminar regime. The flow is considered linearly stable for Reynolds numbers sufficiently below natural transition. A perturbation is added to the inlet fully developed laminar velocity profile to test the flow response to finite amplitude disturbances and to characterise sub-critical transition. Design/methodology/approach Direct numerical simulations of the Navier–Stokes equations have been solved using a spectral element method. Findings It is found that the onset of disordered motion and the dynamics of the localised turbulence patch are controlled by the Reynolds number, the perturbation amplitude and the half angle of the pipe. Originality/value The authors clarify different stages of flow behaviour under the finite amplitude perturbations and shed more light to flow physics such as existence of Kelvin–Helmholtz instabilities as well as mechanism of turbulent puff shedding in diverging pipe flows.

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Lebon, Benoît, Jorge Peixinho, Shun Ishizaka e Yuji Tasaka. "Subcritical transition to turbulence in a sudden circular pipe expansion". Journal of Fluid Mechanics 849 (18 giugno 2018): 340–54. http://dx.doi.org/10.1017/jfm.2018.421.

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The results of experiments on the flow through a circular sudden expansion pipe at moderate Reynolds numbers are presented. At five diameters upstream of the expansion, laminar flow was disturbed by a (constant) cross-flow jet, a suction or a (periodic in–out) synthetic jet from a hole in the wall. When the disturbance exceeded a critical value of the control parameter depending on the Reynolds number, localised turbulent patches formed downstream of the expansion at fixed axial positions. For the cross-flow jet, the onset of turbulent patches is related to the velocity ratio of the mean jet velocity to the mean pipe velocity. At low velocity ratio, turbulent patches formed intermittently. For the suction disturbance, the flow experienced a strong asymmetry of the recirculation region and required a larger velocity ratio before the turbulent patch formed. For the synthetic jet, the amplification of wavy disturbances into turbulent patches and their axial positions are controlled by the driving frequency. Overall, these results suggest the existence of different mechanisms for the development of localised turbulent patches.

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Kells, James A., e C. D. Smith. "Head recovery at submerged abrupt conduit outlets". Canadian Journal of Civil Engineering 15, n. 2 (1 aprile 1988): 272–74. http://dx.doi.org/10.1139/l88-035.

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The question of an abrupt expansion in a pipeline from one diameter to a larger diameter is a classical problem dealt with in most undergraduate fluid mechanics texts. A problem not dealt with, but which is far more common in practice, is the abrupt expansion at the terminal end of a pipe where the flow expands into an open channel downstream. It is often assumed that the entire velocity head for the pipe flow is lost. This is not necessarily true. In this paper, the experimental study of an abrupt expansion into an open channel is reported. Several different channel shapes are used in an attempt to determine shape effect, if any. It is concluded that the primary variable affecting the head loss is the ratio of the upstream to downstream flow area, called the area ratio. Key words: abrupt expansion, conduit outlet, head recovery, head loss, area ratio.

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Akiyoshi, T., K. Fuchida, S. Shirinashihama e T. Tsutsumi. "Effectiveness of Anti-Liquefaction Techniques for Buried Pipelines". Journal of Pressure Vessel Technology 116, n. 3 (1 agosto 1994): 261–66. http://dx.doi.org/10.1115/1.2929585.

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In this paper, effectiveness of several existing anti-liquefaction methods for preventing large deformations of pipelines for lateral flow of liquefied grounds during earthquakes are investigated and compared, as well as a proposed method which fixes pipelines with expansion joints parallel to auxiliary continuous pipes using iron tie-plates. Stiffness of liquefied soils around pipes is represented as a static coefficient of subgrade reaction, based on the experiments on the interaction between liquefied sand deposits and pipes. Pipeline-spring systems which are characterized by those coefficients are analyzed based on the theory of “a beam on an elastic foundation” and transfer matrix method. Computations are performed with respect to the key parameters of pipes, coefficient of subgrade reaction, and several fixing conditions between pipes and underground structures. The sliding displacements of pipelines, rotational angles of joints, and stresses of pipelines are compared for such anti-liquefaction methods as soil-improving methods (sand-compaction pile or ballast-replaced soil methods) and structural-stiffening methods (parallel pipe or pile-supporting methods).

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Wang, Dong, David J. White e Mark F. Randolph. "Large-deformation finite element analysis of pipe penetration and large-amplitude lateral displacement". Canadian Geotechnical Journal 47, n. 8 (agosto 2010): 842–56. http://dx.doi.org/10.1139/t09-147.

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Seabed pipelines must be designed to accommodate thermal expansion — which is commonly achieved through controlled lateral buckling — and to resist damage from submarine slides. In both cases, the pipe moves laterally by a significant distance and the overall pipeline response is strongly influenced by the lateral pipe–soil resistance. Here, the process of pipe penetration and lateral displacement is investigated using a large-deformation finite element method, with a softening rate–dependent soil model being incorporated. The calculated soil flow mechanisms, pipe resistances, and trajectories agree well with plasticity solutions and centrifuge test data. It was found that the lateral resistance is strongly influenced by soil heave during penetration and the berm formed ahead of the pipe during lateral displacement. For “light” pipes, the pipe rises to the soil surface and the soil failure mechanism involves sliding at the base of the berm. In contrast, “heavy” pipes dive downwards and a deep shearing zone is mobilized, expanding with continuing lateral movement. The different responses are reconciled by defining an “effective embedment” that includes the effect of the soil berm or wall ahead of the pipe. The relationship between normalized lateral resistance and effective embedment is well fitted using a power law.

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Ando, Toshitake, Toshihiko Shakouchi, Hiroyuki Yamamoto e Koichi Tsujimoto. "726 Flow characteristics and control of separated shear flow in sudden expansion pipe". Proceedings of the Fluids engineering conference 2005 (2005): 111. http://dx.doi.org/10.1299/jsmefed.2005.111.

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Mahmood, Raid A., Khalid Saleh, Veyan A. Musa, Enass Massoud, Ahmad Sharifian-Barforoush e Lokman A. Abdulkareem. "Two-Phase Flow Development of R134a in a Horizontal Pipe: Computational Investigation". International Journal of Heat and Technology 39, n. 5 (31 ottobre 2021): 1532–40. http://dx.doi.org/10.18280/ijht.390515.

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To improve the performance of vapor compression refrigeration systems that use vertical gravitational flash tank separators, the liquid separation efficiency of the vertical gravitational flash tank separator requires to be approved. To approach this improvement, the two-phase flow development and its behavior after the expansion device need to be investigated and predicted. For thus, this paper presents a three-dimensional computational investigation of the two-phase flow development of R134a after the expansion device in a horizontal pipe. Computational Fluid Dynamic (CFD) was used to predict the two-phase development and its behavior in the horizontal pipe. ANSYS 16.2 program was used to generates the geometry of the three-dimensional horizontal pipe of 2 meters long and 25 mm inner diameter. The hexahedral mesh was generated and it is assessed to obtain the optimum mesh size and number. Eulerian-Eulerian two-phase model was used with k-ɛ turbulence model. R134a was used as a working fluid in the horizontal pipe utilizing four different inlet diameters: 12, 12.5, 25, and 50.0 mm. Mass flux and vapor quality have been changed from 288 to 447 kg/m2.s and from 10 to 20% respectively. Results were validated against experimental results from the literature and revealed that the separation region length is affected by the initial phase velocities, inlet vapor quality, and inlet tube diameter. An empirical correlation to predict the expansion region length is proposed as a function of Froude, Webber, and Lockhart-Martinelli numbers.

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DUGUET, Y., A. P. WILLIS e R. R. KERSWELL. "Slug genesis in cylindrical pipe flow". Journal of Fluid Mechanics 663 (5 ottobre 2010): 180–208. http://dx.doi.org/10.1017/s0022112010003435.

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Transition to uniform turbulence in cylindrical pipe flow occurs experimentally via the spatial expansion of isolated coherent structures called ‘slugs’, triggered by localized finite-amplitude disturbances. We study this process numerically by examining the preferred route in phase space through which a critical disturbance initiates a ‘slug’. This entails first identifying the relative attractor – ‘edge state’ – on the laminar–turbulent boundary in a long pipe and then studying the dynamics along its low-dimensional unstable manifold, leading to the turbulent state. Even though the fully turbulent state delocalizes at Re ≈ 2300, the edge state is found to be localized over the range Re = 2000–6000, and progressively reduces in both energy and spatial extent as Re is increased. A key process in the genesis of a slug is found to be vortex shedding via a Kelvin–Helmholtz mechanism from wall-attached shear layers quickly formed at the edge state's upstream boundary. Whether these shedded vortices travel on average faster or slower downstream than the developing turbulence determines whether a puff or a slug (respectively) is formed. This observation suggests that slugs are out-of-equilibrium puffs which therefore do not co-exist with stable puffs.

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27

Pakhomov, Maksim A., e Viktor I. Terekhov. "Modeling of Turbulent Heat-Transfer Augmentation in Gas-Droplet Non-Boiling Flow in Diverging and Converging Axisymmetric Ducts with Sudden Expansion". Energies 15, n. 16 (12 agosto 2022): 5861. http://dx.doi.org/10.3390/en15165861.

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The effect of positive (adverse) and negative (favorable) longitudinal pressure gradients on the structure and heat transfer of gas-droplet (air and water) flow in axisymmetric duct with sudden expansion are examined. The superimposed pressure gradient has a large influence on the flow structure and heat transfer in a two-phase mist flow in both a confuser and a diffuser. A narrowing of the confuser angle leads to significant suppression of flow turbulence (more than four times that of the gas-drop flow after sudden pipe expansion without a pressure gradient at φ = 0°). Recirculation zone length decreases significantly compared to the gas-droplet flow without a longitudinal pressure gradient (by up to 30%), and the locus of the heat-transfer maximum shifts slightly downstream, and roughly aligns with the reattachment point of the two-phase flow. Growth of the diffuser opening angle leads to additional production of kinetic energy of gas flow turbulence (almost twice as much as gas-droplet flow after a sudden pipe expansion at φ = 0°). The length of the flow recirculating region in the diffuser increases significantly compared to the separated gas-droplet flow without a pressure gradient (φ = 0°), and the location of maximum heat transfer shifts downstream in the diffuser.

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28

Said, S. A. M., M. A. Habib e M. O. Iqbal. "Heat transfer to pulsating turbulent flow in an abrupt pipe expansion". International Journal of Numerical Methods for Heat & Fluid Flow 13, n. 3 (1 maggio 2003): 286–308. http://dx.doi.org/10.1108/09615530310464517.

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A numerical investigation aimed at understanding the flow and heat transfer characteristics of pulsating turbulent flow in an abrupt pipe expansion was carried out. The flow patterns are classified by four parameters; the Reynolds number, the Prandtl number, the abrupt expansion ratio and the pulsation frequency. The influence of these parameters on the flow was studied in the range 104<Re<5×104, 0.7<Pr<7.0, 0.2<d/D<0.6 and 5<f<35. It was found that the influence of pulsation on the mean time‐averaged Nusselt number is insignificant (around 10 per cent increase) for fluids having a Prandtl number less than unity. This effect is appreciable (around 30 per cent increase) for fluids having Prandtl number greater than unity. For all pulsation frequencies, the variation in the mean time‐averaged Nusselt number, maximum Nusselt number and its location with Reynolds number and diameter ratio exhibit similar characteristics to steady flows.

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29

Banis, Kārlis. "The Effect of separated Expansion Chamber Parameters on Exhaust Pressure Oscillations in Single Cylinder Motorcycle Engine". Rural Sustainability Research 43, n. 338 (1 agosto 2020): 42–51. http://dx.doi.org/10.2478/plua-2020-0006.

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AbstractThis paper investigates the effect of separated exhaust expansion chamber parameters on pressure oscillations in spark-ignited internal combustion (IC) gasoline engines. It is known that exhaust expansion chambers are becoming increasingly more popular among both – original equipment (OE) and aftermarket equipment (AE) exhaust system manufacturers for performance-oriented motorcycles equipped with mainly single cylinder engines, but the companies are reluctant to reveal any detailed principles of operation of the mentioned expansion chambers. The subject of this research is the type of expansion chamber (separate) as used on performance-oriented motorcycles, particularly its’ effect on exhaust pressure pulsations as different chamber volumes, locations and passage sizes are tested. Time-dependent computational fluid dynamics (CFD) analysis was carried out in Solidworks Flow Simulation environment on a simplified exhaust header pipe model imitating engine operation at full load and steady speed. Honda CRF450R motorcycle engine was used as the example and fully defined using a 1D engine performance calculator software to determine the combustion chamber pressure and exhaust valve lift at any given crankshaft position. Volume flow rate of exhaust gasses at the header pipe inlet was calculated based on engine parameters and operating speed. The average pressure values with respect to physical time were measured and graphed across the header pipe inlet cross-section. Eight different header pipe and exhaust expansion chamber combinations were modelled, tested, and results compared at low, medium and high engine speeds. It was found that the presence of exhaust expansion chamber tends to dampen the amplitude and decrease the frequency of pressure oscillations generated at the opening of the exhaust valve(s). Observations show that the addition of an expansion chamber as per design of performance-oriented motorcycles helps to decrease the negative effect of engine tuning while also dampening the positive effect.

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30

El-Askary, W. A., I. M. Eldesoky, O. Saleh, Samy M. El-Behery e A. S. Dawood. "Behavior of downward turbulent gas–solid flow through sudden expansion pipe". Powder Technology 291 (aprile 2016): 351–65. http://dx.doi.org/10.1016/j.powtec.2016.01.002.

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31

ANDO, Toshitake, Toshihiko SHAKOUCHI, Hiroyuki YAMAMOTO e Koichi TSUJIMOTO. "Control of Flow Separation and Drag Reduction of Abrupt Expansion Pipe". Transactions of the Japan Society of Mechanical Engineers Series B 72, n. 717 (2006): 1125–30. http://dx.doi.org/10.1299/kikaib.72.1125.

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32

VOUTSINAS, Alexandros, Toshihiko SHAKOUCHI, Koichi TSUJIMOTO e Toshitake ANDO. "Fluctuating Phenomena and Flow Control of Bubbly Two-Phase Flow Through Sudden Expansion Pipe". Journal of Fluid Science and Technology 4, n. 1 (2009): 84–94. http://dx.doi.org/10.1299/jfst.4.84.

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33

Pazanin, Igor. "Asymptotic solution for the Darcy-Brinkman-Boussinesq flow in a pipe with helicoidal shape". Theoretical and Applied Mechanics 45, n. 2 (2018): 189–203. http://dx.doi.org/10.2298/tam180424008p.

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We study the fluid flow and heat transfer in a helical pipe filled with a sparsely packed porous medium. Motivated by the engineering applications, pipe?s thickness and the distance between two coils of the helix have the same small order of magnitude, whereas the fluid inside the pipe is assumed to be cooled (or heated) by the exterior medium. After writing the dimensionless Darcy?Brinkman?Boussinesq system in curvilinear coordinates, we employ the multi-scale expansion technique to formally derive the effective model valid for small Brinkman?Darcy number. The obtained asymptotic solution is given in the explicit form which is important with regards to numerical simulations. Comparison with our previous results on the straight-pipe flow is also provided.

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34

Ahmad Yani, Ratnawati e Ardyanto Darmanto. "Analisa Kerugian Head Akibat Perluasan Dan Penyempitan Penampang Pada Sambungan 90o". Jurnal Teknik Juara Aktif Global Optimis 1, n. 1 (30 giugno 2021): 46–55. http://dx.doi.org/10.53620/jtg.v1i1.10.

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PVC pipe (polyvinyl chloride), galvanized, and stainless steel are types of pipes that are widely used, especially for delivering clean water to people's homes or in the industrialized world. This research was conducted by collecting data such as: flow rate (Q), pressure height (h), pipe flow velocity (v), time (s), and head loss (H), data were collected and calculated to determine pressure loss, effect variations in discharge changes and loss coefficients. From the experimental results, it was found that for the narrowing of the cross section at a discharge of 25 liters / second the value of the head loss was greater, which was located in the galvanic pipe, namely 0.09568, then followed by a discharge of 20 liters / second the value was 0.06454 and a discharge of 15 ltr / second the value was 0 , 03723. While the smallest value in panampang narrowing lies in PVC pipe, at a discharge of 25 ltr / second the value is 0.05957, at a discharge of 20 ltr / second the value is 0.03989 and at a discharge of 15 ltr / second the value is 0.02303. Likewise in the expansion of the cross-section, the greatest value lies in the galvanized pipe. For a debit of 25 ltr / second the value obtained is 0.03526, a debit of 20 ltr / second the value is 0.02355, a debit of 15 ltr / second the value is 0.01352. While the smallest value is located on the stainless steel pipe, the value is 0.02688 for the flow rate of 25 liters / second, the value for 20 liters / second is 0.01811, the value for 15 liters / second is 0.01044.

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35

Matvienko, O. V., A. E. Litvinova e N. S. Firsanova. "The Cross model of liquid polymer- bitumen binder structure in a pipe with sudden expansion". Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 24, n. 5 (27 ottobre 2022): 151–68. http://dx.doi.org/10.31675/1607-1859-2022-24-5-151-168.

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The paper investigates the liquid polymer-bitumen binder in a pipe with a sudden expansion. At small values of the expansion parameter, the formation of a high-viscosity liquid zone occurs in the axial region, and the effective viscosity decreases at the periphery and nearwall zones. The destruction process of structural bonds, which intensively proceeds near the flow from the supply pipe, leads to a decrease in the effective viscosity. The formation of a corner area of reverse flows is accompanied by the increase in the effective viscosity.

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36

Yang, Jaw-Yen, Li-Hsin Hung e Yao-Tien Kuo. "Semiclassical Lattice Boltzmann Simulations of Rarefied Circular Pipe Flows". Communications in Computational Physics 10, n. 2 (agosto 2011): 405–21. http://dx.doi.org/10.4208/cicp.060210.270810a.

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AbstractComputations of microscopic circular pipe flow in a rarefied quantum gas are presented using a semiclassical axisymmetric lattice Boltzmann method. The method is first derived by directly projecting the Uehling-Uhlenbeck Boltzmann-BGK equations in two-dimensional rectangular coordinates onto the tensor Hermite polynomials using moment expansion method and then the forcing strategy of Halliday et al. [Phys. Rev. E., 64 (2001), 011208] is adopted by adding forcing terms into the resulting microdynamic evolution equation. The determination of the forcing terms is dictated by yielding the emergent macroscopic equations toward a particular target form. The correct macroscopic equations of the incompressible axisymmetric viscous flows are recovered through the Chapman-Enskog expansion. The velocity profiles and the mass flow rates of pipe flows with several Knudsen numbers covering different flow regimes are presented. It is found the Knudsen minimum can be captured in all three statistics studied. The results also indicate distinct characteristics of the effects of quantum statistics.

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37

Li, Xue, Ning Zhou, Xuanya Liu, Weiqiu Huang, Bing Chen e Vamegh Rasouli. "Numerical simulation of the influence of pipe length on explosion flame propagation in open-ended and close-ended pipes". Science Progress 103, n. 4 (ottobre 2020): 003685042096160. http://dx.doi.org/10.1177/0036850420961607.

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The pipeline length exerts great influence on flame propagation characteristics, Realizable [Formula: see text] model and Premixed combustion model were used to study the influence of pipe length on propane-air explosion flame in open-ended and close-ended pipes. Using the numerical model verified by experiments, the changes of flame structure and flame propagation speed are studied. The result showed that the Realizable model was in good agreement with the experimental results. It also proved that the reflected wave produced a strong interference on the flame front, which promoted the formation of tulip flame. Besides, some obvious vortices were usually generated in the burned gas after the tulip flame formed, which will affect the flow field around the flame front and thus exert influence on the flame structure. The formation mechanism of tulip flame as well as the flame self-acceleration is different in open-ended and close-ended pipes. In close-ended pipes, the reflection wave at the pipe end and the reflection-induced countercurrent both promote the formation of tulip flame. As the flame propagates to the pipe end, the flame propagation is inhibited by the compression wave formed by the rapid expansion of combustion products under high temperature. While, in open-ended pipes, the turbulence induced by the opening at the pipe end is the main cause of tulip flame formation. The flame acceleration depends on the combustion reaction of unburned gas, so the velocity of flame propagation continues to increase. Generally, the maximum flame propagation velocity in the open-ended pipe is larger than that in the close-ended pipe.

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38

Sanmiguel-Rojas, E., e T. Mullin. "Finite-amplitude solutions in the flow through a sudden expansion in a circular pipe". Journal of Fluid Mechanics 691 (12 dicembre 2011): 201–13. http://dx.doi.org/10.1017/jfm.2011.469.

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AbstractResults of three-dimensional numerical simulations of the flow through a sudden expansion in a pipe are presented. The axisymmetric state is known to be stable over the range of Reynolds numbers studied, but recent experimental results suggest bifurcation phenomena. A resolution of this dichotomy between calculation and experiment is provided using imperfections to promote the nonlinear development of asymmetric steady states. These lose stability to disordered motion and the boundary between the steady and time-dependent flows has been established over a range of parameters. Moreover, disordered flows are found to co-exist with the axisymmetric regime when the disturbance is removed from the flow. Hence we provide direct numerical evidence for multiplicity of solutions for the axisymmetric expansion problem, which may have relevance to pipe flows.

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39

Stro¨ll, H., F. Durst, M. Peric´, J. C. F. Pereira e G. Scheuerer. "Study of Laminar, Unsteady Piston-Cylinder Flows". Journal of Fluids Engineering 115, n. 4 (1 dicembre 1993): 687–93. http://dx.doi.org/10.1115/1.2910200.

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The present paper concerns numerical investigation of a piston-driven, axisymmetric flow in a pipe assembly containing a sudden expansion. The piston closes the larger of the two pipes. The impulsively starting intake flow is the topic of this investigation. Results of numerical calculations and laser-Doppler measurements are presented to provide an insight into the features of the flow. The calculation procedure employed in this study is based on a finite-volume method with staggered grids and SIMPLE-algorithm for pressure-velocity coupling (Patankar and Spalding, 1972). The convection and diffusion fluxes in the Navier-Stokes equations are discretized with first order upwind and second order central differences, respectively. A fully implicit Euler scheme is used to discretize the temporal derivatives. The Navier-Stokes equations were suitably transformed to allow prediction of the flow within the inlet pipe (fixed grid) and cylinder region (moving grid) simultaneously (once-through procedure). Laser-Doppler measurements of both axial and radial velocity components were performed. Refractive index matching was used to eliminate the wall curvature effects. For each measuring point 20 cycles were measured, showing high repetition rates. Comparison of measured and predicted velocity profiles shows good agreement.

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40

Donkin, Seth, e David Herrin. "An experimental study of flow-induced noise from perforated pipes". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 264, n. 1 (24 giugno 2022): 139–50. http://dx.doi.org/10.3397/nc-2022-708.

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An experimental study was performed to understand the generated flow noise by perforated pipes inside of concentric tube resonators. Six perforated pipes with 2% to 45% open areas and hole diameters ranging from 0.8 mm to 4.65 mm are considered. The six concentric tube resonators are compared to a straight pipe and a simple expansion chamber. All cases are tested at ten flow velocities ranging from 0.1 Mach to 0.28 Mach with a 0.02 Mach increment. The effect of the hole diameter and perforation rate on the noise generation and the overall level of the radiated noise is examined. It is found that the whistle frequency is inversely proportional to the hole diameter and proportional to the flow velocity. The amplitude of the generated flow noise is proportional to the perforation rate. Finally, an insertion loss method is used to demonstrate that minimizing the hole diameter and perforation rate decreases the generated flow noise.

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41

Li, Lin, e David Z. Zhu. "Modulation of transient pressure by an air pocket in a horizontal pipe with an end orifice". Water Science and Technology 77, n. 10 (1 maggio 2018): 2528–36. http://dx.doi.org/10.2166/wst.2018.213.

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Abstract In urban drainage systems, a sudden increase in the flow rate can cause the transition of the flow from open channel to pipe flow, and the entrapment of large air pockets in sewers, which might result in serious geysers and water-hammer like pressure events. This paper presents a numerical analysis of flow processes associated with the pressurization and release of an air pocket in order to study its influence on transient pressure in a horizontal pipe with an end orifice. The influence of the air pocket inside the pipe on the peak pressure can be described in two distinct regimes. In regime I for the pipe with a small orifice, the peak pressure is modulated by the pressurization and expansion of the air pocket and its subsequent damping. In regime II for the pipe with a large orifice, air can be quickly expelled, and the water column directly impinges on the pipe end wall and causes water-hammer like pressure. With the increase of the orifice size, the peak pressure decreases due to the change in the water velocity. In the study cases, the peak pressure in regime I is about two times the inlet pressure, while it can be more than forty times in regime II.

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42

González, José, Andrés Meana-Fernández, Iván Vallejo Pérez e Jesús M. Fernández Oro. "Minor Loss Coefficient for Abrupt Section Changes in a Cylindrical Pipe Using a Numerical Approach". Fluids 9, n. 7 (26 giugno 2024): 152. http://dx.doi.org/10.3390/fluids9070152.

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Abrupt section changes are a classic problem in the study of flow in cylindrical ducts or pipes. For its analysis, there are a wide set of exiting data from previous studies, among which some authors stand out and will be mentioned. Those previous works have been used to obtain reliable results for the resolution of section changes along a pipe, either due to cross area increases or reductions on a 1D basis. It is also known that a numerical 2D axisymmetric simulation (CFD) could find a consistent result compared to experimental data in almost all fluid flow fields. The main novelty of the present study is the development of a simple numerical approach used to solve the minor loss calculation. Firstly, a theoretical analysis is developed, and then the results of the numerical simulations carried out on the behavior that affects the water and air flow rate in an abrupt section change, for both contraction and expansion problems, are presented. In both cases, the results are analyzed with different meshes (discretizations) and turbulence models. Finally, the obtained numerical results are compared with those in the technical literature. Also, a theoretical approach is shown in order to show a whole frame of the discussion. The core results are the loss coefficient evolution as a function of the section change both for the sudden contraction and the expansion of a pipe flow. As the results follow the existing experimental values, it is concluded that the developed model provides a feasible and quick design tool to analyze possible geometrical changes without the need for further experiments.

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43

Su, Haonan, Huazheng Chen, Rongsheng Zhu e Qiang Fu. "Effect of reduced diameter pipeline and impeller position on the performance of reactor coolant pump". Journal of Physics: Conference Series 2707, n. 1 (1 febbraio 2024): 012036. http://dx.doi.org/10.1088/1742-6596/2707/1/012036.

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Abstract In the reactor coolant pump experiments, there are cases where different impellers are replaced on the same volute for experiments, but due to the different diameter of the impeller inlet, there will be a sudden expansion between the inlet pipeline and the impeller inlet, resulting in a decrease in the efficiency of the pump. In order to solve this problem, a scheme of using an inlet pipe with a reduced diameter structure and changing the position of the impeller was proposed, and based on the three-dimensional incompressible Reynolds N-S equation, the reactor coolant pump device was numerically simulated by CFD software. The data simulation results of the reduced diameter structure, straight pipe flow field and changing the position of the impeller were compared with the model experiments, and the reliability of the calculation results was verified. The results show that the inlet pipe with reduced diameter structure and the method of changing the position of the impeller can effectively solve the problem of efficiency decline caused by the sudden expansion of the flow channel.

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44

Orel, Vadym, Bohdan Pitsyshyn e Tetiana Konyk. "HYDRODYNAMICAL INSTABILITY OF NEWTONIAN FLOW BEFORE AN AXISYMMETRIC SUDDEN CONTRACTION". Theory and Building Practice 2021, n. 2 (15 dicembre 2021): 32–38. http://dx.doi.org/10.23939/jtbp2021.02.032.

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The sizes of the vortex region before the axisymmetric sudden contraction of the circular pipe at the Newtonian flow have been investigated. Area ratios 0.250 and 0.500 were considered. The sizes of the vortex region have the extreme dependence with a maximum at the transition of the laminar flow into a turbulent flow one. When the Reynolds number at the laminar flow increase, these sizes also increase, and they decrease at the turbulent flow. In both cases, the sizes of the vortex region are proportional to the Reynolds number. A transition region between laminar flow and turbulent flow lies in the range of the Reynolds number from 3000 to 5300 and 750…1300, determined by the diameter of a bigger pipe of sudden expansion and a step height correspondingly

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45

Doresic, Tvrtko, e Igor Pazanin. "Curved-pipe flow with boundary conditions involving Bernoulli pressure". Electronic Journal of Differential Equations 2024, n. 01-?? (22 ottobre 2024): 63. http://dx.doi.org/10.58997/ejde.2024.63.

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In this article, we study the steady-state flow of the incompressible viscous fluid through a thin distorted pipe with an arbitrary central curve. We prescribe the inflow and outflow boundary conditions involving the Bernoulli pressure with a given pressure drop. Using the multiscale expansion technique with respect to the pipe's thickness, we construct the higher-order asymptotic approximation of the flow given by the explicit formulae for the velocity and pressure. We also perform a detailed error analysis justifying the usage of the proposed solution and indicating its order of accuracy. For more information see https://ejde.math.txstate.edu/Volumes/2024/63/abstr.html

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46

Selvam, Kamal, Jorge Peixinho e Ashley P. Willis. "Flow in a circular expansion pipe flow: effect of a vortex perturbation on localised turbulence". Fluid Dynamics Research 48, n. 6 (7 novembre 2016): 061418. http://dx.doi.org/10.1088/0169-5983/48/6/061418.

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47

Nejad, A. S., e S. A. Ahmed. "Flow field characteristics of an axisymmetric sudden-expansion pipe flow with different initial swirl distribution". International Journal of Heat and Fluid Flow 13, n. 4 (dicembre 1992): 314–21. http://dx.doi.org/10.1016/0142-727x(92)90001-p.

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48

Cao, Z., Z. Wang, J. Deng, X. Guo e L. Lu. "Unsteady friction model modified with compression–expansion effects in transient pipe flow". Journal of Water Supply: Research and Technology-Aqua 71, n. 2 (19 gennaio 2022): 330–44. http://dx.doi.org/10.2166/aqua.2022.144.

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Abstract This paper aims to modify the conventional one-coefficient instantaneous acceleration-based (IAB) model for better prediction of unsteady friction behavior. In this work, the energy dissipation caused by viscous stress during fluid volume compression–expansion (CE) was derived from the compressible Navier–Stokes equation. It is found that the energy dissipation term can be expressed by the product of the second-order partial derivative of velocity in space and the second viscosity coefficient. On this basis, a modified IAB-CE model was developed with the energy dissipation term and solved by the method of characteristic (MOC). The numerical results obtained from the modified model showed a good agreement with the four test cases, where the relative errors are improved by 0.26, 2.03, 9.56, and 36.67%, compared with the results from the original IAB model. The estimation for wave peak and valley is improved as well. Furthermore, the Bradley equation can be applied to establish the relationship between the dissipation coefficient and the Reynolds number. The modified model developed in this study takes into account the fluid CE effects and improves the prediction accuracy of wave amplitude of unsteady flow.

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49

Zhang, Dawei, e Afshin Goharzadeh. "Effect of Sudden Expansion on Two-Phase Flow in a Horizontal Pipe". Fluid Dynamics 54, n. 1 (gennaio 2019): 123–36. http://dx.doi.org/10.1134/s0015462819010178.

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50

Koronaki, E. D., H. H. Liakos, M. A. Founti e N. C. Markatos. "Numerical study of turbulent diesel flow in a pipe with sudden expansion". Applied Mathematical Modelling 25, n. 4 (marzo 2001): 319–33. http://dx.doi.org/10.1016/s0307-904x(00)00055-x.

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