A CFD Simulation of Near Wall Turbulent Flow in Concentric Annulus

2013 ◽  
Author(s):  
Aziz Rahman ◽  
Fabio Ernesto Rodriguez Corredor ◽  
Majid Bizhani ◽  
Ergun Kuru
Keyword(s):  
Experimental Data ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Water Flow ◽  
Simulation Study ◽  
Cfd Simulation ◽  
Concentric Annulus ◽  
Sst Model ◽  
Cfd Analyses ◽  
Near Wall

A CFD simulation study was conducted to analyse the near wall turbulence characteristics of water flow through concentric annulus. The continuity and momentum equations were solved by using a commercial CFD package (CFX 14) with the Shear-Stress-Transport (SST) model option. The simulation results were compared to the experimental data obtained by using high resolution Particle Image Velocimetry (PIV) analyses of water flow in a horizontal concentric annulus. A fully developed turbulent flow of water through a horizontal flow loop (ID = 9.5 cm) with concentric annular geometry (inner to outer pipe radius ratio = 0.4) was used for comparison purpose. Reynolds number ranged from 17,500 to 68,500. Annular velocity profile obtained from simulation study showed good agreement with the experimental data. Near wall velocity profile obtained from CFD simulation followed the universal wall law (u+ = y+) up to y+ = 11. CFD analyses using the SST model resulted a good number of velocity data up to y+ = 11, which is normally a very difficult task to achieve experimentally. The CFD analyses using SST model is computationally inexpensive and therefore, can be conveniently used for investigating the near wall turbulent characteristics of flow in concentric annulus.

Near Wall Turbulence Characteristics of a Drag Reducing Polymer Fluid Flow in Concentric Annulus Using CFD

2013 ◽  
Author(s):  
Aziz Rahman ◽  
Fabio Ernesto Rodriguez Corredor ◽  
Majid Bizhani ◽  
Ergun Kuru
Keyword(s):  
Experimental Data ◽  
Wall Turbulence ◽  
Power Law Fluid ◽  
Flow Rates ◽  
Concentric Annulus ◽  
Polymer Fluid ◽  
Sst Model ◽  
Drag Reducing Polymer ◽  
Near Wall Turbulence ◽  
Near Wall

A CFD simulation was conducted to analyze the near wall turbulence characteristics of a drag reducing (DR) polymer fluid (0.12% V/V) flow through concentric annulus. The continuity and momentum equations were solved by using a commercial CFD package (CFX 14) with the Shear-Stress-Transport (SST) model option. The simulation results were compared to the experimental data obtained by using high resolution Particle Image Velocimetry (PIV) analyses of drag reducing polymer fluid flow in a horizontal concentric annulus. A fully developed turbulent flow of water through a horizontal flow loop (ID = 9.5 cm) with concentric annular geometry (inner to outer pipe radius ratio = 0.4) was used for comparison purpose. The flow rates ranged from 3.92 to 5.95 kg/s. Drag reducing PHPA solutions behaved as a power law fluid with the rheological model (μ = Kγn−1) for the shear rate of 1/s to 600/s. Bulk and near wall velocity profile obtained from simulation showed good agreements with the experimental data. Drag reducing polymer reduce the Reynolds stresses level due to weaker and fewer turbulent eddies formation near the wall. Results of the simulation study also showed that if the flow rates of power law fluid increased from 3.92 to 5.95 kg/s, the drag reduction in the annuli is increased from 10% to 20% compared to water case indicating the strong damping to turbulent kinetic energy in the flow. The CFD analyses using SST model is computationally inexpensive and, therefore, can be conveniently used for investigating the flow characteristics of drag reducing polymer fluids in concentric annulus.

Characterization of Time-Averaged Turbulence Statistics for Shear Thinning Fluid in Horizontal Concentric Annulus Using RANS Based CFD Simulation

2016 ◽  
Author(s):  
Xiao Xiong ◽  
Mohammad Azizur Rahman ◽  
Yan Zhang
Keyword(s):  
Cfd Simulation ◽  
Model Simulation ◽  
Polymer Concentration ◽  
Shear Thinning ◽  
Turbulent Shear ◽  
Wall Region ◽  
Turbulence Statistics ◽  
Concentric Annulus ◽  
Sst Model ◽  
Shear Thinning Fluid

A RANS based shear stress transportation (SST) model was employed in this study to validate experimental results from a recent literature, which investigated the fully developed turbulent flow for a non-Newtonian shear thinning fluid, containing drag reduction polymer additives in a horizontal concentric annulus (inner to outer radio θ = 0.4). The polymer concentration varied from 0.07% V/V to 0.12% V/V and three mass flow rates from 3.92 kg/s to 5.95 kg/s were analyzed. The viscous property of the fluid was modeled by the power-law model. Simulation performed with the commercial code of ANSYS-CFX indicated that the SST model with default model constants overestimated the turbulence statistics of shear thinning flow in the near wall region where y+<60. As an effort to improve simulation accuracy, one of the model constants α1 was tuned in this study for the first time. Simulation results obtained from the modified model showed better agreement with experimental data compared to those from the default one. The present study represents a successful benchmark task for simulating turbulent shear thinning flow in concentric annuli with modified turbulence model constants.

Simplified theory of the near-wall turbulent layer of Newtonian and drag-reducing fluids

1982 ◽  
Vol 119 ◽  
pp. 423-441 ◽  
Author(s):  
M. A. Goldshtik ◽  
V. V. Zametalin ◽  
V. N. Shtern
Keyword(s):  
Velocity Profile ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Outer Boundary ◽  
Viscous Sublayer ◽  
Viscous Layer ◽  
Mean Velocity ◽  
Turbulent Layer ◽  
The Mean ◽  
Near Wall

We propose a simplified theory of a viscous layer in near-wall turbulent flow that determines the mean-velocity profile and integral characteristics of velocity fluctuations. The theory is based on the concepts resulting from the experimental data implying a relatively simple almost-ordered structure of fluctuations in close proximity to the wall. On the basis of data on the greatest contribution to transfer processes made by the part of the spectrum associated with the main size of the observed structures, the turbulent fluctuations are simulated by a three-dimensional running wave whose parameters are found from the problem solution. Mathematically the problem reduces to the solution of linearized Navier-Stokes equations. The no-slip condition is satisfied on the wall, whereas on the outer boundary of a viscous layer the conditions of smooth conjunction with the asymptotic shape of velocity and fluctuation-energy profiles resulting from the dimensional analysis are satisfied. The formulation of the problem is completed by the requirement of maximum curvature of the mean-velocity profile on the outer boundary applied from stability considerations.The solution of the problem does not require any quantitative empirical data, although the conditions of conjunction were formulated according to the well-known concepts obtained experimentally. As a result, the near-wall law for the averaged velocity has been calculated theoretically and is in good agreement with experiment, and the characteristic scales for fluctuations have also been determined. The developed theory is applied to turbulent-flow calculations in Maxwell and Oldroyd media. The elastic properties of fluids are shown to lead to near-wall region reconstruction and its associated drag reduction, as is the case in turbulent flows of dilute polymer solutions. This theory accounts for several features typical of the Toms effect, such as the threshold character of the effect and the decrease in the normal fluctuating velocity. The analysis of the near-wall Oldroyd fluid flow permits us to elucidate several new aspects of the drag-reduction effect. It has been established that the Toms effect does not always result in thickening of the viscous sublayer; on the contrary, the most intense drag reduction takes place without thickening in the viscous sublayer.

Annular Flow—A Note on the Turbulent Velocity Profile

1958 ◽  
Vol 62 (575) ◽  
pp. 830-831 ◽  
Author(s):  
Henry Barrow
Keyword(s):  
Experimental Data ◽  
Velocity Profile ◽  
Velocity Distribution ◽  
Power Law ◽  
Annular Flow ◽  
Turbulent Velocity ◽  
Concentric Annulus ◽  
Annular Section ◽  
Modified Power Law

The Important characteristics of the turbulent velocity profile of a plain concentric annulus and some of the methods of correlating the velocity distribution are briefly reviewed. The average velocities in an annular section are examined and some experimental data is correlated by a modified power law.

Effect of Near Wall Turbulence on the Particle Removal From Bed Deposits in Horizontal Wells

2016 ◽  
Author(s):  
Majid Bizhani ◽  
Ergun Kuru ◽  
Sina Ghaemi
Keyword(s):  
Velocity Profile ◽  
Turbulent Flow ◽  
Reynolds Stress ◽  
Turbulence Intensity ◽  
Experimental Program ◽  
Local Velocity ◽  
Cutting Bed ◽  
Cuttings Bed ◽  
The Impact ◽  
Near Wall

Although solids entrainment and deposition mechanisms have been studied extensively over the years, our understanding of fluids-particle interactions near bed interface is still limited. Progress toward such understanding has been relatively slow because of the difficulties inherent simultaneous measurement of local solids transport and adjacent near-bed fluid flow. With the introduction of non-intrusive measurement techniques such as Particle Image Velocimetry (PIV), it is now possible to determine the instantaneous velocity field and observe particle deposition/resuspension simultaneously under non-uniform flow conditions. An experimental program was conducted to investigate different aspects of turbulent flow of water over the cuttings bed deposited in horizontal annuli. A large-scale horizontal flow loop consisting of 9 m long high quality optic glass pipes (95 mm ID of outer pipe and 38 mm OD of inner pipe) equipped with state of the art PIV system has been used for the experiments. Turbulent flow over cuttings bed experiments were conducted at superficial Reynolds numbers of 9300 and 10800. Natural irregular shaped quartz sands with 3 different mean sieve sizes of 260, 350 and 600 micron were used as solid particles. The proposed work was accomplished through several tasks: i-) conduct experiments to measure the instantaneous local velocity profile during turbulent flow in the horizontal concentric annuli and examine the effect of stationary cutting bed on the local velocity profile, Reynolds stress and turbulence intensity; ii-) investigate the impact of particle size on the near-wall turbulent activities. Results have indicated that existence of a cuttings bed on the lower side of the wellbore dramatically alters the near wall velocity profile comparing to the case with no cuttings bed. Presence of cuttings bed causes the maximum velocity to shift toward the inner pipe. Presence of stationary cutting bed causes a reduction in Reynolds stress, axial and radial turbulence intensity, which in turn, would adversely affect the hole cleaning. Larger cuttings slightly enhanced turbulent stress and radial intensities. However, the increase in these entities as a result of increasing cutting size was far less than the decrease in them as a consequence of presence of stationary cutting bed. Axial turbulence intensity was the same in the core flow away from the cuttings bed for flow with and without a cuttings bed. However, the peak of axial intensities is shown to be less for flow near the cuttings bed.

scholarly journals Assessment of RANS turbulence closure models for predicting airflow in neutral ABL over hilly terrain

2021 ◽  
Author(s):  
Amahjour Narjisse ◽  
Khamlichi Abdellatif
Keyword(s):  
Experimental Data ◽  
Wind Speed ◽  
Cfd Simulation ◽  
Turbulence Models ◽  
Computational Time ◽  
Recirculation Region ◽  
Leeward Side ◽  
Hilly Terrain ◽  
Steep Hill ◽  
Near Wall

AbstractImplementing wind farms in heights of a hilly terrain where wind speed is expected to be large may be viewed as a means to increase wind energy production without occupying fertile lands. Micro sitting of a wind farm in these conditions can gain dramatically from CFD simulation of fluid flow in the ABL above complex topography. However, this issue still poses tough challenges regarding the turbulence model to be used and the way to operate the near wall treatment in the presence eventually of separation. In this work, prediction capacity of RANS turbulence models was studied for a typical hill under the assumption of steady state and incompressible airflow regime in neutral ABL. Two models were analyzed by using COMSOL Multiphysics software packages. These included standard , and shear-stress transport . The most up-to-date procedures dedicated to near wall treatment were applied along with refined closer coefficients adjusted for the particular case of ABL. Considering wind tunnel test data, performance of the previous models was discussed in terms of converging mesh, computational time, reattachment point position and propensity of the model to retrieve the right level of turbulence flow in conditions of neutral stratifications. Then, a numerical simulation of the turbulent airflow over two slopes shapes of the symmetry hill by the validation of the experimental data has been then carried out. Both turbulence models agree well with air-velocity tested windward of the hills H3 and H5. Therefore, it was found that the standard model performs very well at the different positions of the low slope hill, and at the summit of a steep hill, but it over-predicts wind speed close to the wall, which requires an improvement of the near-wall treatment. However, the model in neutral case of the ABL was given consistent simulation results with experimental data for prediction of the flow separation and recirculation region at the leeward side of a steep hill, whereas standard model under the neutral condition and the model by using standard coefficients were failed to predict accurately detailed characteristics of recirculation region process.

Investigation of the influence of the flow structure on the accuracy of flow measurement before a hydrometric structure in an open channel

2020 ◽  
pp. 41-44
Author(s):  
Anatoly Kusher
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Water Flow ◽  
Flow Measurement ◽  
Water Discharge ◽  
Critical Depth ◽  
Flow Measurements ◽  
Study Results ◽  
Flow Velocity Profile ◽  
Upstream Flow

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.

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