scholarly journals Pitch Variations Study on Helically Coiled Pipe in Turbulent Flow Region Using CFD

2020 ◽  
Vol 38 (4) ◽  
pp. 775-784
Author(s):  
Anwer F. Faraj ◽  
Itimad D.J. Azzawi ◽  
Samir G. Yahya
Keyword(s):  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Flow Region ◽  
Dean Number ◽  
Ansys Fluent ◽  
Commercial Code

A computational fluid dynamics (CFD) study was conducted to analyse the flow structure and the effect of varying the coil pitch on the coil friction factor and wall shear stress, through utilising different models’ configurations. Three coils were tested, all of them having the same diameter and coil diameter: 0.005m and 0.04m respectively. Pitch variations began with 0.01, 0.05, 0.25 m for the first, second and third model respectively. Two turbulence models, STD(k-ϵ) and STD(k-w), were utilised in this simulation in order to determine the turbulence model which could capture most of the flow characteristics. A comparison was made between the STD(k-ϵ) and STD(k-w) models in order to analyse the pros and cons of each model. The results were validated with Ito’s equation for turbulent flow and compared with Filonenko’s equation for a straight pipe. The governing equations were discretized using finite volumes method and the SIMPLE algorithm was used to solve the equations iteratively. All the models were simulated using the ANSYS Fluent solver CFD commercial code. The results showed that in turbulent flows, Dean number had a stronger effect on reducing coil friction factor than the increment in pitch dimension.

scholarly journals Friction Factor Estimation for Turbulent Flows in Corrugated Pipes with Rough Walls

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Maxim Pisarenco ◽  
Bas van der Linden ◽  
Arris Tijsseling ◽  
Emmanuel Ory ◽  
Jacques Dam
Keyword(s):  
Boundary Condition ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Flow Behavior ◽  
Turbulence Models ◽  
Computational Grids ◽  
Law Of The Wall ◽  
Fully Developed Turbulent Flow ◽  
The Right

The motivation of the investigation is the critical pressure loss in cryogenic flexible hoses used for LNG transport in offshore installations. Our main goal is to estimate the friction factor for the turbulent flow in this type of pipes. For this purpose, two-equation turbulence models (k−ϵ and k−ω) are used in the computations. First, the fully developed turbulent flow in a conventional pipe is considered. Simulations are performed to validate the chosen models, boundary conditions, and computational grids. Then a new boundary condition is implemented based on the “combined” law of the wall. It enables us to model the effects of roughness (and maintain the right flow behavior for moderate Reynolds numbers). The implemented boundary condition is validated by comparison with experimental data. Next, the turbulent flow in periodically corrugated (flexible) pipes is considered. New flow phenomena (such as flow separation) caused by the corrugation are pointed out and the essence of periodically fully developed flow is explained. The friction factor for different values of relative roughness of the fabric is estimated by performing a set of simulations. Finally, the main conclusion is presented: The friction factor in a flexible corrugated pipe is mostly determined by the shape and size of the steel spiral, and not by the type of the fabric, which is wrapped around the spiral.

scholarly journals Friction Factor Estimation for Turbulent Flows in Corrugated Pipes With Rough Walls

2009 ◽  
Author(s):  
Maxim Pisarenco ◽  
Bas van der Linden ◽  
Arris Tijsseling ◽  
Emmanuel Ory ◽  
Jacques Dam
Keyword(s):  
Boundary Condition ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Flow Behavior ◽  
Turbulence Models ◽  
Computational Grids ◽  
Law Of The Wall ◽  
Fully Developed Turbulent Flow ◽  
The Right

The motivation of the investigation is critical pressure loss in cryogenic flexible hoses used for LNG transport in offshore installations. Our main goal is to estimate the friction factor for the turbulent flow in this type of pipes. For this purpose, two-equation turbulence models (k–ε and k–ω) are used in the computations. First, fully developed turbulent flow in a conventional pipe is considered. Simulations are performed to validate the chosen models, boundary conditions and computational grids. Then a new boundary condition is implemented based on the “combined” law of the wall. It enables us to model the effects of roughness (and maintain the right flow behavior for moderate Reynolds numbers). The implemented boundary condition is validated by comparison with experimental data. Next, turbulent flow in periodically corrugated (flexible) pipes is considered. New flow phenomena (such as flow separation) caused by the corrugation are pointed out and the essence of periodically fully developed flow is explained. The friction factor for different values of relative roughness of the fabric is estimated by performing a set of simulations. Finally, the main conclusion is presented: the friction factor in a flexible corrugated pipe is mostly determined by the shape and size of the steel spiral, and not by the type of the fabric which is wrapped around the spiral.

scholarly journals Effect of Secondary Vortex Flow Near Contact Point on Thermal Performance in the Plate Heat Exchanger with Different Corrugation Profiles

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1328 ◽  
Author(s):  
Hyung Ju Lee ◽  
Seong Hyuk Lee
Keyword(s):  
Friction Factor ◽  
Thermal Performance ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Contact Point ◽  
Flow Characteristics ◽  
Ansys Fluent ◽  
Plate Heat ◽  
Flow Mixing ◽  
Commercial Code

The present study numerically investigates thermal performance and turbulent flow characteristics of chevron-type plate heat exchangers with sinusoidal, trapezoidal, triangular, and elliptical corrugation profiles. The commercial code of ANSYS Fluent (v. 17.0) is used for computational fluid dynamics (CFD) simulation with the realizable k-ε model. In particular, we focus on the influence of configuration shape on a substantial change in flow direction near the contact point, yielding local vorticity. As a result, secondary vortical motions are observed in the flow passage with vorticity that is distributed locally and which changes near the contact point. Higher flow mixing generated and distributed by the secondary vortical motions contributes to the increase of the Colburn j-factor as well as the friction factor. The highest Colburn j-factor and friction factor are obtained for an elliptical profile, compared to other shapes, because of the increase in the vortex strength near the contact point.

Numerical and Experimental Analysis of Turbulent Flow in Corrugated Pipes

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Henrique Stel ◽  
Rigoberto E. M. Morales ◽  
Admilson T. Franco ◽  
Silvio L. M. Junqueira ◽  
Raul H. Erthal ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Magnitude ◽  
Geometric Configurations ◽  
Corrugated Surfaces ◽  
Friction Factors

This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements.

Particle Collision Effect on Turbulent Prandtl Number in Gas-Solid Flows

2006 ◽  
Author(s):  
Zohreh Mansoori ◽  
Majid Saffar-Avval ◽  
Hasan Basirat-Tabrizi ◽  
Goodarz Ahmadi ◽  
Payam Ramezani
Keyword(s):  
Prandtl Number ◽  
Turbulent Flow ◽  
Time Scale ◽  
Turbulence Models ◽  
Flow Region ◽  
Eddy Diffusivity ◽  
Particle Collision ◽  
Turbulent Prandtl Number ◽  
Particle Collisions ◽  
Particle Properties

Traditional gas-solid turbulence models using constant or the single-phase gas turbulent Prandtl number cause error in the thermal eddy diffusivity and thermal turbulent intensity fields calculation. The thermo-mechanical turbulence model is based on solving the hydrodynamic transport equations of the turbulent kinetic energy and turbulent time scale, beside the thermal turbulent equations of temperature variance and thermal turbulence time scale. This model has the ability to calculate the turbulent Prandtl number directly by computing the eddy viscosity and the thermal eddy diffusivity through the values of turbulence fluctuation velocity and thermal variances and time scales. A four way Eulerian/Lagrangian formulation was used to study the effect of particle properties on the turbulent flow and thermal fields, as well as on turbulent Prandtl number in a gas-solid developing pipe flow. Inter-particle collisions were included and the Lagrangian trajectory analysis was used. The earlier results showed that turbulent Prandtl number is influenced by the variations of gas and particle properties and also inter-particle collisions in a fully-developed riser. In the current study, the developing gas-solid flow region in a pipe was considered and the variation of turbulent flow field due to inter-particle collision was evaluated.

A Functional Scaling Relationship for Laminar to Turbulent Flow Regimes

2011 ◽  
Author(s):  
George Papadopoulos
Keyword(s):  
Turbulent Flow ◽  
Stokes Equations ◽  
Initial Conditions ◽  
Flow Characteristics ◽  
Flow Region ◽  
Flow Regimes ◽  
Transitional Flow ◽  
Turbulent Regime ◽  
Flow Profile ◽  
Scaling Relationship

A dimensional analysis that is based on the scaling of the two-dimensional Navier-Stokes equations is presented for correlating bulk flow characteristics arising from a variety of initial conditions. The analysis yields a functional relationship between the characteristic variable of the flow region and the Reynolds number for each of the two independent flow regimes. A linear relationship is realized for the laminar regime, while a nonlinear relationship is realized for the turbulent regime. Both relationships incorporate mass-flow profile characteristics to fully capture the effects of initial conditions on the variation of the characteristic variables. The union of these two independent relationships is formed utilizing the concept of flow intermittency to further expand into a generic scaling relationship that incorporates transitional flow effects to fully encompass solutions spanning the laminar to turbulent flow regimes. The results of the analysis are discussed within the context of several flow phenomena (e.g. pipe flow, jet flow & separated flow) resulting from various initial and boundary conditions.

Measurement of Semi-Local Friction Factor of Gas Flow in Micro-Tube

2013 ◽  
Author(s):  
D. Kawashima ◽  
Y. Asako
Keyword(s):  
Surface Roughness ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Gas Flow ◽  
Flow Region ◽  
Nitrogen Gas ◽  
Gaseous Flow ◽  
Flow Through ◽  
Local Pressures ◽  
Measured Pressure

This paper presents experimental results on friction factor of gaseous flow in a PEEK micro-tube with relative surface roughness of 0.04 %. The experiments were performed for nitrogen gas flow through the micro-tube with 514.4 μm in diameter and 50 mm in length. Three pressure taps holes with 5 mm interval were drilled and the local pressures were measured. Friction factor is obtained from the measured pressure differences. The experiments were conducted for turbulent flow region. The friction factor obtained by the present study are compared with those in available literature and also numerical results. The friction factor obtained is slightly higher than the value of Blasius formula.

Numerical investigation on turbulent convective heat transfer of nanofluid flow in a square cross-sectioned duct

2019 ◽  
Vol 29 (4) ◽  
pp. 1432-1447 ◽  
Author(s):  
Gülbanu Şenay ◽  
Metin Kaya ◽  
Engin Gedik ◽  
Muhammet Kayfeci
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Flow Characteristics ◽  
Constant Heat Flux ◽  
Ansys Fluent ◽  
Square Duct ◽  
Content Type ◽  
Volume Fractions ◽  
Darcy Friction Factor

Purpose The purpose of this study is to numerically investigate the heat transfer enhancement by using two different nanofluids flow throughout the square duct under a constant heat flux (500 × 103 W/m2). Design/methodology/approach In numerical computations, ANSYS Fluent code based on the finite volume method was used to solve governing equations by iteratively. Water, Al2O3-water and TiO2-water nanofluids were used for different flow velocities changing 1 m/s to 8 m/s (i.e. Reynolds number varying from 3,000 to 100,000). Findings The results were compared with results published previously in the literature and close agreement was observed especially considering Dittus and Boelter correlation for water. It was found that from the obtained results, increasing flow velocity and volume fractions of nanoparticles has caused to increase Nu number for all cases. Besides, variations of pressure drop, Darcy friction factor are presented graphically and discussed in detail. The results are consistent with a deviation of 1.3 to 15 per cent with the results of other researchers. Originality/value The effects of the Re numbers and volume fractions of nanoparticles (0.01 ≤ Φ ≤ 0.04) on the heat transfer and fluid flow characteristics such as average Nu number, pressure drop (ΔP) and Darcy friction factor (f) were investigated.

Numerical Analysis of Turbulent Flow Over a Wavy Wall in a Channel

2016 ◽  
Author(s):  
Vinicius Martins Segunda ◽  
Scott Ormiston ◽  
Mark Tachie
Keyword(s):  
Turbulent Flow ◽  
Turbulence Models ◽  
Moment Closure ◽  
Recirculation Region ◽  
Wavy Wall ◽  
Viscosity Models ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Flow Phenomena ◽  
Second Moment Closure

A commercial CFD code (ANSYS CFX, release 16.2) is used to predict the turbulent flow phenomena over a wavy wall. The present work will provide numerical simulations of flow in a channel with a wavy lower wall using a variety of turbulence models available in the CFD commercial code. Eddy viscosity models and Second Moment Closure models were used with wall function available. Those turbulence models had different predictions for the flow field, in which were evaluated: velocity profiles, pressure distribution, wall shear stress, recirculation region and turbulence quantities. A comparison between their predictions will be presented. The validation of results is performed by comparison to experimental data from previous studies and also LES simulations.

Laminar flow in rotating curved pipes

1996 ◽  
Vol 329 ◽  
pp. 373-388 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Experimental Data ◽  
Laminar Flow ◽  
Friction Factor ◽  
Flow Structure ◽  
Flow Characteristics ◽  
Laminar Flows ◽  
Dean Number ◽  
Governing Parameter ◽  
Curved Pipes ◽  
Wide Range

When a curved pipe rotates about the centre of curvature, the fluid flowing in it is subjected to both Coriolis and centrifugal forces. Based on the analogy between laminar flows in stationary curved pipes and in orthogonally rotating pipes, the flow characteristics of fully developed laminar flow in rotating curved pipes are made clear and definite by similarity arguments, computational studies and using experimental data. Similarity arguments clarify that the flow characteristics in loosely coiled rotating pipes are governed by three parameters: the Dean number KLC, a body force ratio F and the Rossby number Ro. As the effect of Ro is negligible when Ro is large, computational results are presented for this case first, and then the effect of Ro is studied. Flow structure and friction factor are studied in detail. Variations of flow structure show secondary flow reversal at F ≈ −1, where the two body forces are of the same order but in opposite directions. It is also shown how the Taylor–Proudman effect dominates the flow structure when Ro is small. Computed curves of the friction factor for constant Dean number have their minimum at F ≈ −1. A composite parameter KL is introduced as a convenient governing parameter and used to correlate the characteristics. By applying KL to the analogy formula previously derived for two limiting flows, a semi-empirical formula for the friction factor is presented, which shows good agreement with the experimental data for a wide range of the parameters.

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