Direct numerical simulation of transitional flow in a finite length curved pipe

Hashemi, Amirreza; Fischer, Paul; Loth, Francis

doi:10.1080/14685248.2018.1497293

Cited by 15 publications

(8 citation statements)

References 25 publications

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“…To show the unsteady behavior properly they discussed the power spectrum density. Hashemi et al [15] addressed velocity fluctuation with flow transition and the consequences of bifurcation in turbulent flow through the curved tubing. Alonso et al [16] explained the variation of flow patterns in respect of time for a vertical cylinder.…”

Section: Introductionmentioning

confidence: 99%

A computational modeling on transient heat and fluid flow through a curved duct of large aspect ratio with centrifugal instability

et al. 2021

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Due to remarkable applications of the curved ducts in engineering fields, scientists have paid much attention to invent new characteristics of curved-duct flow in mechanical systems. In the ongoing study, a computational modeling of fluid flow and energy distribution through a curved rectangular duct of large aspect ratio is presented. Governing equations are enumerated by using a spectral-based numerical technique together with the function expansion and collocation method. The main purpose of the paper is to analyze the effect of centrifugal force in the flow transition as well as heat transfer in the fluid. The investigations are performed for the aspect ratio, Ar = 4; the curvature ratio, $$\delta = 0.5$$ δ = 0.5 ; the Grashof number, $${\text{Gr}} = 1000$$ Gr = 1000 ; and varying the Dean number, $$0 < {\text{Dn}} \le 1000.$$ 0 < Dn ≤ 1000 . It is found that various types of flow regimes including steady-state and irregular oscillations occur as Dn is increased. To well understand the characteristics of the flow phase spaces and power spectrum of the solutions are performed. Next, pattern variations of axial and secondary flow velocity with isotherms are illustrated for different Dn’s. It is revealed that the flow velocity and the isotherms are significantly influenced by the duct curvature and the aspect ratio. Convective heat transfer and temperature gradients are calculated which explores that the fluids are diversified due to centrifugal instability, and as a consequence the overall heat transfer is enhanced significantly in the curved duct.

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Section: Introductionmentioning

confidence: 99%

A computational modeling on transient heat and fluid flow through a curved duct of large aspect ratio with centrifugal instability

et al. 2021

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“…Chandratilleke et al (2013) offered a numerical and experimental investigation of flow-through both rectangular and elliptical channels with heat transfer effects. Hashemi et al (2018) the axial flow with the change of time through a finite length curved pipe. Rahmani et al (2019) represented the isotherms contours where they employed finite Fourier transform and the method to calculate the heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Investigation on Energy Distribution in Steady and Unsteady Flow Instabilities through a Bend Square Pipe

et al. 2021

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Fluid flow analysis through a bend pipe is extensively conducted in practical and cell separation operations. It is observed that flow behaviors in the bend pipe are influenced by some parameters such as curvature, aspect ratio, etc. As a result, various phenomena, steady solution branches, unsteady solutions, energy transfer are changed. In this paper, the acts of flows are performed together for fixed curvature, δ = 0.2, and Prandtl number, Pr = 7.0 (water). Here, for a wide variety of Dean numbers (100 ≤ Dn ≤ 1000) and three fixed Grashof numbers, Gr = 100, 500, and 1000; time-independent solutions with linear stabilities are investigated first where only the first steady branch exhibits linear stability out of two steady solution branches obtained. Then, different flow transitions between the required range of Dean numbers (Dn) and several Grashof numbers (Gr) are investigated using time-dependent solutions. Power spectrum density (PSD) is further revealed in order to gain a deeper understanding of periodic and multi-periodic flows. Flow velocity contours including axial flow (AF) and secondary flow (SF) and their temperature profiles (TP) are also exposed. The SFs reveal that two- to four-vortex flows are produced due to the turning of steady branch and the flow instabilities. Furthermore, the energy transfer between the cooled and heated sidewalls of the pipe is calculated. Finally, a link between centrifugal and body force with the energy transfer has been shown in this research which reveals that the fluid has merged that certainly rises the overall energy transfer.

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“…Secondary structures due to the unsteady flow through a curved duct were investigated by Krishna et al [9]. The fluctuation of axial velocity with respect to time was analyzed by Hashemi et al [10] for both finite and infinite length curved pipes. Mondal et al [11] investigated unsteady behavior of fluid flows in a non-rotating curved rectangular duct with respect to the Nusselt number for different aspect ratios.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on the Transition of Fluid Flow Characteristics Through a Rotating Curved Duct

Hasan

Islam

Badsha

et al. 2020

International Journal of Applied Mechanics and Engineering

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Time-dependent flow investigation through rotating curved ducts is utilized immensely in rotating machinery and metal industry. In the ongoing exploration, time-dependent solutions with flow transition through a rotating curved square duct of curvature ratio 0.009 have been performed. Numerical calculations are carried out for constant pressure gradient force, the Dean number Dn = 1000 and the Grashof number Gr=100 over a wide range of the Taylor number values –1500 ≤ Tr ≤ 1500 for both positive and negative rotation of the duct. The software Code::Blocks has been employed as the second programming tool to obtain numerical solutions. First, time evolution calculations of the unsteady solutions have been performed for positive rotation. To clearly understand the characteristics of regular and irregular oscillations, phase spaces of the time evolution results have been enumerated. Then the calculations have been further attempted for negative rotation and it is found that the unsteady flow shows different flow instabilities if Tr is increased or decreased in the positive or in the negative direction. Two types of flow velocities such as axial flow and secondary flow and temperature profiles have been exposed, and it is found that there appear two- to four-vortex asymmetric solutions for the oscillating flows for both positive and negative rotation whereas only two-vortex for the steady-state solution for positive rotation but four-vortex for negative rotation. From the axial flow pattern, it is observed that two high-velocity regions have been created for the oscillating flows. As a consequence of the change of flow velocity with respect to time, the fluid flow is mixed up in a great deal which enhances heat transfer in the fluid.

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Direct numerical simulation of transitional flow in a finite length curved pipe

Cited by 15 publications

References 25 publications

A computational modeling on transient heat and fluid flow through a curved duct of large aspect ratio with centrifugal instability

A computational modeling on transient heat and fluid flow through a curved duct of large aspect ratio with centrifugal instability

Investigation on Energy Distribution in Steady and Unsteady Flow Instabilities through a Bend Square Pipe

Numerical Investigation on the Transition of Fluid Flow Characteristics Through a Rotating Curved Duct

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