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.

CFD-Analysis of Fully Developed Turbulent Flow and Heat Transfer in a Unitary Cell of a Cross Corrugated Plate Pattern Heat Exchanger

2007 ◽  
Author(s):  
Sassan Etemad ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Turbulent Flow ◽  
Friction Factor ◽  
The Other ◽  
Computational Grids ◽  
Flow And Heat Transfer ◽  
Shear Process ◽  
Secondary Motion ◽  
Fully Developed Turbulent Flow

The turbulent flow and the heat transfer in a unitary cell of a cross corrugated plate pattern heat exchanger has been studied using Chen’s high-Re k-ε model, Suga’s low-Re k-ε model, the RSM and the V2F model at a Reynolds number of 4930. The ability of these models in predicting the mean Nusselt number and Fanning friction factor has been investigated. The V2F model predicted higher heat transfer and friction factors than the other models. It was observed that the upper and lower flow in the unitary cell interact throw a shear process. This in turn initiates a complex secondary flow pattern which promotes the heat transfer. The V2F model predicted the strongest shear process. This may explain the fact that it also predicted the highest values of heat transfer and friction factor compared to the other models. The shear flow also caused high levels of turbulent kinetic energy in the centre of the unitary cell. The observed secondary motion is believed to be an efficient means of increasing the heat transfer coefficient with limited pressure drop penalty. It is also demonstrated that despite the geometrical complexity, high quality computational grids can be created and thereby details of the flow and heat transfer phenomena can be studied. The RSM appeared to be instable and gave results similar to Chen’s k-ε model. Therefore, its use is not motivated for such applications.

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.

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.

Assessment of Different Turbulence Models in Helically Coiled Pipes Through Comparison With Experimental Data

2012 ◽  
Author(s):  
Marco Colombo ◽  
Antonio Cammi ◽  
Marco E. Ricotti
Keyword(s):  
Turbulent Flow ◽  
Great Influence ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Test Facility ◽  
Wall Functions ◽  
Pressure Drops ◽  
Fully Developed Turbulent Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Helical Geometry

This paper deals with a comprehensive study of fully developed single-phase turbulent flow and pressure drops in helically coiled channels. To the aim, experimental pressure drops were measured in an experimental campaign conducted at SIET labs, in Piacenza, Italy, in a test facility simulating the Steam Generator (SG) of a Generation III+ integral reactor. Very good agreement is found between data and some of the most common correlations available in literature. Also more data available in literature are considered for comparison. Experimental results are used to assess the results of Computational Fluid Dynamics (CFD) simulations. By means of the commercial CFD package FLUENT, different turbulence models are tested, in particular the Standard, RNG and realizable k-ε models, Shear Stress Transport (SST) k-ω model and second order Reynolds Stress Model (RSM). Moreover, particular attention is placed on the different types of wall functions utilized through the simulations, since they seem to have a great influence on the calculated results. The results aim to be a contribution to the assessment of the capability of turbulence models to simulate fully developed turbulent flow and pressure drops in helical geometry.

Fluid Flow and Heat Transfer Behavior for Turbulent Flows in a Tube With Vortex Generator Pairs for an Efficient Heat Exchanger

2018 ◽  
Author(s):  
Md. Islam ◽  
Z. Chong ◽  
S. Bojanampati
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Flow Behavior ◽  
Vortex Generator ◽  
Tube Diameter ◽  
Vortex Generators ◽  
Blockage Ratio ◽  
Delta Winglet

Various technologies have been developed to enhance flow mixing and heat transfer in order to develop an efficient compact heat exchanging devices. Vortex generators/turbulent promoters generate the vortices which reduce the boundary layer thickness and introduce the better mixing of the fluid to enhance the heat transfer. In this research experimental investigations have been carried out to study the effect of delta winglet vortex generator pairs on heat transfer and flow behavior. To generate longitudinal vortex flow, two pairs of the delta winglet vortex generators (DWVG) with the length of 10mm and winglet-pitch to tube-diameter ratio (PR = 4.8) are mounted on the inner wall of a circular tube. The DWVG pairs with two different winglet-height to tube-diameter ratios (Blockage ratio, BR = 0.1 and 0.2), three attack angles (α = 10°, 20°, 30°) and three spacings between leading edges (S = 10, 15 and 20mm) are studied. The experiments were conducted with DWVGs pairs for the air flow range of Reynolds numbers 5000–25000. The influence of the DWVGs on heat transfer and pressure drop was investigated in terms of the Nusselt number and friction factor. The experimental results indicate that DWVG pair in a tube results in a considerable enhancement in Nusselt number (Nu) with some pressure penalty. It is found that DWVG increases Nu up to 85% over the smooth tube. It is also observed that Nusselt number increases with Re, blockage ratio and attack angle. Friction factor decreases with Re but increases with blockage ratio, spacing and attack angle. And 30° DWVG pair with S = 20mm, BR = 0.2 gets the highest friction factor. The Highest thermal performance enhancement (TPE) was noticed for α = 10°, S = 20mm, BR = 0.2 for turbulent flows. To obtain qualitative information on the flow behavior and vortex structures, flow was visualized by laser sheet using smoke as a tracer supplied at the entrance of the test section. The generation and development of longitudinal vortices influenced by DWVG pairs were clearly observed.

Parallel Dynamic Large Eddy Simulation of Turbulent Flow Around MIRA Model

2002 ◽  
Author(s):  
H. G. Choi ◽  
S. W. Kang ◽  
J. Y. Yoo
Keyword(s):  
Boundary Condition ◽  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Experimental Result ◽  
Open Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Parallel Code ◽  
Grid Points

For the large scale computation of turbulent flows around an arbitrarily shaped body, a parallel LES (large eddy simulation) code has been recently developed in which domain decomposition method is adopted. METIS and MPI (message passing interface) libraries are used for domain partitioning and data communication between processors, respectively. For unsteady computation of the incompressible Navier-Stokes equation, 4-step splitting finite element algorithm [1] is adopted and Smagorinsky or dynamic LES model can be chosen for the modeling of small eddies in turbulent flows. For the outlet (open) boundary condition, a Dirichlet boundary condition for the pressure is proposed. For the validation and performance-estimation of the parallel code, a three-dimensional laminar flow generated by natural convection inside a cube has been solved. We have confirmed that our code gives accurate results compared with previous studies. Regarding the speed-up of the code, the present parallel code with parallel block-Jacobi preconditioner is about 50 times faster than the corresponding serial code with 64 processors when approximately one million grid points are used. Most of the CPU time is consumed in solving elliptic type pressure equation. For the validation of LES models, turbulent channel flows are simulated at Re = 180, which is based on the channel half height and friction velocity using 51 × 71 × 71 grid system. It has been shown that our results agree well with the well-known results by Kim et al. [2] with less grid points than used by them in terms of time-averaged velocity field and velocity fluctuation. Lastly, we have solved the turbulent flow around MIRA (Motor Industry Research Association) model at Re = 1.6 × 106 which is based on the model height and inlet free stream velocity. Both Smagorinsky and dynamic models are tested, comparing estimated drag coefficients and pressure distribution along the model surface with the existing experimental data [3]. With the help of the parallel code developed in this study, we are able to obtain a unsteady solution of the turbulent flow field around a vehicle discretized by approximately three million grid points within two weeks when 32 IBM-SP2-processors are used. The calculated drag coefficient agrees better with the experimental result [3] than those using two equation turbulence models [4].

A Methodology for Simulating Compressible Turbulent Flows

2005 ◽  
Vol 73 (3) ◽  
pp. 405-412 ◽  
Author(s):  
Hermann F. Fasel ◽  
Dominic A. von Terzi ◽  
Richard D. Sandberg
Keyword(s):  
Turbulent Flows ◽  
Compressible Flows ◽  
Bluff Body ◽  
Turbulence Modeling ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Fine Grid ◽  
Local Flow

A flow simulation Methodology (FSM) is presented for computing the time-dependent behavior of complex compressible turbulent flows. The development of FSM was initiated in close collaboration with C. Speziale (then at Boston University). The objective of FSM is to provide the proper amount of turbulence modeling for the unresolved scales while directly computing the largest scales. The strategy is implemented by using state-of-the-art turbulence models (as developed for Reynolds averaged Navier-Stokes (RANS)) and scaling of the model terms with a “contribution function.” The contribution function is dependent on the local and instantaneous “physical” resolution in the computation. This physical resolution is determined during the actual simulation by comparing the size of the smallest relevant scales to the local grid size used in the computation. The contribution function is designed such that it provides no modeling if the computation is locally well resolved so that it approaches direct numerical simulations (DNS) in the fine-grid limit and such that it provides modeling of all scales in the coarse-grid limit and thus approaches a RANS calculation. In between these resolution limits, the contribution function adjusts the necessary modeling for the unresolved scales while the larger (resolved) scales are computed as in large eddy simulation (LES). However, FSM is distinctly different from LES in that it allows for a consistent transition between RANS, LES, and DNS within the same simulation depending on the local flow behavior and “physical” resolution. As a consequence, FSM should require considerably fewer grid points for a given calculation than would be necessary for a LES. This conjecture is substantiated by employing FSM to calculate the flow over a backward-facing step and a plane wake behind a bluff body, both at low Mach number, and supersonic axisymmetric wakes. These examples were chosen such that they expose, on the one hand, the inherent difficulties of simulating (physically) complex flows, and, on the other hand, demonstrate the potential of the FSM approach for simulations of turbulent compressible flows for complex geometries.

Fully Developed Turbulent Flow in Annuli

1964 ◽  
Vol 86 (4) ◽  
pp. 835-842 ◽  
Author(s):  
J. A. Brighton ◽  
J. B. Jones
Keyword(s):  
Turbulent Flow ◽  
Turbulence Intensity ◽  
Small Diameter ◽  
Reynolds Numbers ◽  
Mean Velocity ◽  
Law Of The Wall ◽  
Velocity Gradients ◽  
Circular Pipes ◽  
Fully Developed Turbulent Flow ◽  
Annular Pipes

For annular pipes with diameter ratios from 0.0625 to 0.562 and with Reynolds numbers from 46,000 to 327,000, mean-velocity distributions and the location of the maximum mean velocity for each flow condition are presented. The point of maximum mean velocity in turbulent flow occurs at a smaller radius than in laminar flow. Velocity profiles are compared with the law of the wall and the velocity-defect law and are found to deviate from the usual correlations whenever the radial distribution of Reynolds stress, which was also measured, is far from linear. This occurs in the inner profiles for small diameter ratios. Mixing length and eddy-viscosity distributions were determined from accurate measurements of velocity gradients. Turbulence intensity distributions are presented, and these in conjunction with already published distributions for flow in circular pipes and for flow between parallel planes provide knowledge of turbulence-intensity distributions for all cases of fully developed, one-dimensional flow.

Effect of Asymmetric Jet Placement on Turbulent Flow Structure Inside a Jet-Stirred Reactor

2010 ◽  
Author(s):  
Khaled J. Hammad ◽  
Ivana M. Milanovic
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Flow Structure ◽  
Turbulence Models ◽  
Vortex Identification ◽  
Reynolds Decomposition ◽  
Fully Developed Turbulent Flow ◽  
Identification Technique ◽  
Turbulent Flow Structure ◽  
Wall Interaction

Particle Image Velocimetry (PIV) was used to investigate the turbulent flow structure inside a jet-stirred cylindrical vessel. The submerged jet issued vertically downward from a long pipe ensuring fully developed turbulent flow conditions at the outlet. The Reynolds number based on jet mean exit velocity was 15,000. The effect of symmetric and asymmetric nozzle placement within the vessel on the resulting flow patterns was also studied. The measured turbulent velocity fields are presented using Reynolds decomposition into mean and fluctuating components, which, for the selected flow configuration, inflow and boundary conditions, allow for straightforward assessment of turbulence models and numerical schemes. The flow field was subdivided into three regions: the jet, the jet-wall interaction and bulk of vessel. Proper Orthogonal Decomposition (POD) analysis was applied to identify the most energetic coherent structures of the turbulent flow field in the bulk of tank region. The swirling strength vortex identification technique was used to detect the existence and strength of vortical structures in the jet region.

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