RANS Modelling of a Swirling Flow Interacting With a Conical Bluff Body

2018 ◽  
Author(s):  
J. Song ◽  
N. Kharoua ◽  
L. Khezzar ◽  
M. Alshehhi
Keyword(s):  
Flow Rate ◽  
Bluff Body ◽  
Swirling Flow ◽  
Flow Behavior ◽  
Tangential Velocity ◽  
Turbulence Models ◽  
Scale Model ◽  
Axial Distance ◽  
Computational Domain ◽  
Swirl Generator

Phase separation using swirling flows is a technique used in inline separators. In the present study, an existing separator device generates a swirling flow which interacts with a conical hollow bluff body to where the air phase is collect. We use the commercial CFD code Fluent to simulate and investigate the characteristics of single-phase turbulent swirling flow interaction with a solid conical bluff body on a laboratory-scale model. The simulation work employed different RANS turbulence models; namely, RNG k-ε, SST k-ω and RSM. A constant velocity was imposed at the inlet of the computational domain while a constant pressure was prescribed at the outlet. The results are validated against experimental measurements. The effect of flow rate was investigated. The resulting flow is investigated around the bluff body and within the whole outlet pipe downstream of the swirl generator because the separation depends strongly on the flow behavior in this extended region. The core flow reversal persists up to the bluff body at high flow rates. This is significant in terms of phase behavior in the separation application in addition to the loads on the bluff body. The profiles of the tangential velocity corresponded to a Rankine vortex swirling flow type along the whole axial distance. The results show that the RSM gives the best accuracy among the three RANS models compared with the experimental data. The rate of swirl decay decreases as the flow rate increases. For the lowest flow rate, the swirl decay followed an exponential trend which becomes almost linear for the highest flow rate considered. At low swirl intensities, the pressure peaks are observed on the bluff body apex while, at high swirl intensities, the reversal flow generates the lowest pressure at the centerline affecting the cone as well.

Local Velocity Measurements and Computational Fluid Dynamics (CFD) Simulations of Swirling Flow in a Cylindrical Cyclone Separator

2001 ◽  
Author(s):  
Ferhat M. Erdal ◽  
Siamack A. Shirazi
Keyword(s):  
Swirling Flow ◽  
Flow Behavior ◽  
Tangential Velocity ◽  
Turbulence Models ◽  
Laser Doppler Velocimeter ◽  
Cfd Simulations ◽  
Contour Maps ◽  
Cylindrical Cyclone ◽  
Contour Plots ◽  
Local Measurements

Abstract Local measurements and 3-D CFD simulations in Gas-Liquid cylindrical Cyclone (GLCC©) separators are scarce. The main objective of this study is to conduct local measurements and 3-D CFD simulations to understand the swirling flow behavior in a cylindrical cyclone with one inclined tangential inlet. Axial and tangential velocities and turbulent intensities across the GLCC© diameter were measured at 24 different axial locations (12.5″ to 35.4″ below the inlet) by using a Laser Doppler Velocimeter (LDV). The liquid flow rate was 72GPM, which corresponds to an average axial velocity of 0.732 m/s and Reynolds number of 66,900. Measurements are used to create color contour plots of axial and tangential velocity and turbulent kinetic energy. Color contour maps revealed details of the flow behavior. Additionally, 3-D CFD simulations with different turbulence models are conducted. Simulations results are compared to LDV measurements.

Experiments and Large Eddy Simulation of Swirling Flow in a Pipe

2018 ◽  
Author(s):  
Zhang Tianxing ◽  
Nabil Kharoua ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi ◽  
Shrinivas Bojanampati
Keyword(s):  
Kinetic Energy ◽  
Large Eddy Simulation ◽  
Swirling Flow ◽  
Fluid Velocity ◽  
Tangential Velocity ◽  
Scale Model ◽  
Axial Distance ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean

Swirling flows in pipes are encountered in several industrial applications for separation or mixing purposes. In this work turbulent swirling flow is generated using a new swirl generator in the form of thick-walled pipe with multi-radial holes which is lodged inside a larger cylindrical housing, called the Swirl Cage. The swirling flow exiting from the Swirl Cage feeds into a long pipe where the Reynolds number based on the pipe diameter and average velocity is equal to 40836.67. Large Eddy Simulation (LES) is used to calculate the swirling flow and explore its characteristics in conjunction with the Dynamic Kinetic Energy Subgrid-Scale model. Experiments were conducted using LDV and the results are used for validation purposes and for the discussion of the flow features. The results are discussed in relation with the mean fluid velocity and its RMS component. Profiles of the mean tangential velocity reveal a Rankine vortex swirling flow type along the whole axial distance. The core flow was slightly oscillating exhibiting a processing vortex behavior reflected by the radial velocities at the centerline. The profiles of the turbulent kinetic energy were characterized by a peak at the centerline increasing in magnitude with the axial distance. The swirl number decayed from 1.5 right at the outlet of the swirl cage to unity close to the outlet of the pipe.

Local Velocity Measurements and Computational Fluid Dynamics (CFD) Simulations of Swirling Flow in a Cylindrical Cyclone Separator

2004 ◽  
Vol 126 (4) ◽  
pp. 326-333 ◽  
Author(s):  
Ferhat M. Erdal ◽  
Siamack A. Shirazi
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Swirling Flow ◽  
Flow Behavior ◽  
Tangential Velocity ◽  
Turbulence Models ◽  
Laser Doppler Velocimeter ◽  
Cfd Simulations ◽  
Cylindrical Cyclone ◽  
Local Measurements

Local measurements and 3D CFD simulations in gas-liquid cylindrical cyclone separators are scarce. The main objective of this study is to conduct local measurements and 3D CFD simulations to understand the swirling flow behavior in a cylindrical cyclone with one inclined tangential inlet. Axial and tangential velocities and turbulent kinetic energy across the cylinder diameter ID=0.089m were measured at 24 different axial locations (0.32–0.90 m below the inlet) by using a laser Doppler velocimeter (LDV). The liquid flow rate was 16.4m3/h, which corresponds to an average axial velocity of 0.732 m/s and Reynolds number of 66,900. Measurements are used to create color contour plots of axial and tangential velocity and turbulent kinetic energy. Color contour maps revealed details of the flow behavior. Additionally, 3D CFD simulations with different turbulence models are conducted. Simulations results are compared to LDV measurements.

Analysis of Turbulent Swirling Flow in an Isothermal Gas Turbine Combustor Model

2014 ◽  
Author(s):  
A. C. Benim ◽  
S. Iqbal ◽  
A. Nahavandi ◽  
W. Meier ◽  
A. Wiedermann ◽  
...  
Keyword(s):  
Swirling Flow ◽  
Turbulence Models ◽  
Scale Model ◽  
Gas Turbine Combustor ◽  
Wall Functions ◽  
Swirl Velocity ◽  
Subgrid Scale Model ◽  
German Aerospace ◽  
Isothermal Gas ◽  
Upstream Flow

Isothermal turbulent swirling flow in a model combustor is computationally and experimentally investigated. The main purpose was the validation of turbulence models for this flow type. The experiments were carried out at the German Aerospace Centre (DLR), Stuttgart. For the modeling, the validation of the LES approach, applying the Smagorinsky subgrid-scale model, using wall-functions, takes a central role in the present study. URANS calculations based on SST and RSM were also performed. An analysis for LES showed that a sufficient resolution is indeed obtained for grid index values proposed in the literature. It was also observed that coarser grids can still deliver useful results. LES results were observed to be quite accurate, except the swirl velocity in the outer parts of the jet, which was under-predicted. URANS results were not that good, whereas the RSM performed better than the SST, especially in predicting the swirl velocity in the outer parts. An investigation performed on different domain sizes indicated that the outlet boundary formulation has some influence on the prediction of the upstream flow. The influence of the differencing scheme on LES was also investigated.

Streamwise Development of Co-Rotating, Paired Vortices Created by Tangential Injection

2003 ◽  
Author(s):  
Mary V. Holloway ◽  
Heather L. McClusky ◽  
Donald E. Beasley
Keyword(s):  
Swirling Flow ◽  
Tangential Velocity ◽  
Reynolds Numbers ◽  
Velocity Fields ◽  
Flow Structures ◽  
Lateral Velocity ◽  
Swirl Generator ◽  
Swirl Chamber ◽  
Image Velocimetry ◽  
Downstream Development

The present experimental study investigates the interaction and downstream development of two localized swirling flow structures created using a tangential injection method. A swirl generator is placed at the inlet of a 52.1 mm diameter pipe. The swirl generator consists of two swirl chambers with inner diameters of 23.8 mm. Each swirl chamber has a design swirl number of 7.14. Water is injected into each swirl chamber by two tangential injection ports. The injection ports are tangent to the swirl chamber and perpendicular to the axis of the pipe. The two co-rotating vortices created in the swirl generator interact freely within the pipe downstream of the swirl generator. The objective of the present study is to document the interaction between the two vortices and the downstream development of the flow. Lateral velocity fields are obtained using particle image velocimetry (PIV). Time-averaged lateral velocity fields and tangential velocity profiles are presented for several axial locations downstream of the swirl generator. Reynolds numbers of 11,000 and 17,000 are investigated. Results document the streamwise development and interaction between the two co-rotating vortices created by tangential injection. As the two swirling structures develop in the streamwise direction, three different types of flow patterns are identified. The first consists of two distinct swirling flow structures. Further downstream of the swirl chamber, the two swirling structures merge and form a single swirling flow structure with an elliptic core. In the third flow pattern, the center core of the swirling flow has a circular shape.

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.

scholarly journals Numerical investigation of operating pressure effects on the performance of a vortex tube

2014 ◽  
Vol 18 (2) ◽  
pp. 507-520 ◽  
Author(s):  
Nader Pourmahmoud ◽  
Hassan Zadeh ◽  
Omid Moutaby ◽  
Abdolreza Bramo
Keyword(s):  
Turbulent Flows ◽  
Vortex Tube ◽  
Swirling Flow ◽  
Vortex Chamber ◽  
Pressure Effects ◽  
Dynamics Simulation ◽  
Working Fluid ◽  
Axial Distance ◽  
Computational Domain ◽  
Operating Pressure

A three-dimensional computational fluid dynamics simulation of a vortex tube has been carried out to realize the effects of operating pressure. The highly rotating flow field structure and its characteristic are simulated and analyzed with respect to various operating inlet pressure ranges. Numerical results of compressible and turbulent flows are derived by using of the standard k-? turbulence model, where throughout the vortex tube was taken as a computational domain. The main object of the present research is to focus on the importance of identifying the suitable inlet gas pressure corresponds to used vortex tube geometry. Achieving a highly swirling flow and consequently maximum cold temperature difference were the key parameters of judgment. The results revealed that these acceptable conditions of machine performance can be provided when the inlet operating pressure is appropriate both to mechanical structure of machine and physical properties of working fluid. The stagnation point location in the axial distance of vortex tube and Mach number contours in the vortex chamber as additional information are extracted from flow filed; such that interpretation of shock wave formation regions may be accounted as significant features of investigation. Finally, some results of the CFD models are validated by the available experimental data and shown reasonable agreement, and other ones are compared qualitatively.

Numerical Studies on Combustor-Turbine Interaction at the Large Scale Turbine Rig (LSTR)

2017 ◽  
Author(s):  
Jonathan Hilgert ◽  
Martin Bruschewski ◽  
Holger Werschnik ◽  
Heinz-Peter Schiffer
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Guide Vane ◽  
Turbulence Models ◽  
Detailed Examination ◽  
Computational Domain ◽  
Complex Flow ◽  
Lean Burn ◽  
Swirl Generator ◽  
Nozzle Guide

In order to fully understand the physical behavior of lean burn combustors and its influence on high pressure turbine stages in modern jet engines, the use of Computational Fluid Dynamics (CFD) promises to be a valuable addition to experimental techniques. The numerical investigations of this paper are based on the Large Scale Turbine Rig (LSTR) at Technische Universität Darmstadt, Germany which has been set up to explore the aerothermal combustor turbine interaction. The underlying numerical grids of the simulations take account of the complex cooling design to the fullest extent, considering coolant cavities, cooling holes and vane trailing edge slots within the meshing process. In addition to the k-ω-SST turbulence model, Scale-Adaptive Simulation (SAS) is applied for a computational domain comprising swirl generator and nozzle guide vanes in order to overcome the shortcomings of eddy viscosity turbulence models with regard to streamline curvature. The numerical results are compared with Five Hole Probe measurements at different streamwise locations showing good agreement and allowing for a more detailed examination of the complex flow physics caused by the interaction of turbine flow with lean-burn combustion and advanced film-cooling concepts. Moreover, numerically predicted Nu-contours on the hub end wall of the nozzle guide vane are validated by means of Infrared Thermography measurements.

Velocity Characteristics of a Confined Highly-Turbulent Swirling Flow Near a Swirl Plate (Data Bank Contribution)

1994 ◽  
Vol 116 (4) ◽  
pp. 685-693 ◽  
Author(s):  
R. X. Shi ◽  
B. Chehroudi
Keyword(s):  
Flow Rate ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Air Flow ◽  
Tangential Velocity ◽  
Velocity Profiles ◽  
Air Flow Rate ◽  
Reversed Flow ◽  
Swirl Number ◽  
Flow Rates

Axial and tangential components of the velocity vector are measured using a Laser Doppler Velocimeter (LDV) system in a confined highly turbulent isothermal swirling flow near a swirl plate. The flow has essential features of swirl-stabilized flame combustors. Throughout this study, a constant “nominal” swirl number of 0.36 is generated by air jets from a set of slots in a swirl plate. A low-speed coflowing air, referred to as dilution air, is uniformly distributed around the swirling flow by use of an annular-shaped honeycomb. Three different swirling air flow rates with a fixed dilution flow rate are studied and results are discussed. Detailed mean axial and tangential velocity profiles at several axial locations show that the size and the strength of the central recirculation zone are strongly dependent on the swirling air flow rate. Increasing the swirl air flow rate increases both the radial extent and the axial length of the central recirculation zone. Mean total and reversed air flow rates are calculated by integrating the mean axial velocity profiles. In the setup used in this study and up to the axial positions investigated, the reversed flow rate as a percent of the total flow rate seems to be linearly proportional to the reversed-flow zone area, being independent of the swirl air flow rate at a fixed nominal swirl number value. As swirl air flow rate is increased, the root mean square (rms) of the axial and tangential velocity fluctuations increase monotonically at almost all radial positions except sufficiently away from the swirl plate and near the chamber axis. Several velocity biasing correction methods are reviewed. A simple velocity biasing correction scheme is applied in this study to investigate its effect on the conclusions reached in the study.

Analysis of Highly Swirled, Turbulent Flows in Dump Combustor With Exit Contraction

2005 ◽  
Author(s):  
Daniel A. Nickolaus ◽  
Clifford E. Smith
Keyword(s):  
Turbulent Flows ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Turbulence Models ◽  
Flow Patterns ◽  
Navier Stokes ◽  
Computational Domain ◽  
Recirculation Flow ◽  
Dump Combustor ◽  
Radial Profiles

Highly swirled flows are commonly used in gas turbine combustors to stabilize the flame and enhance fuel-air mixing. Experiments by D. G. Lilley, 1985 have shown that swirling flow patterns (i.e. recirculation zones) are dramatically impacted by a downstream contraction. For unconstricted swirling flow, a large, central recirculation zone is formed, while for constricted swirling flows, the recirculation zone can be annular in shape and high (positive) axial velocity is seen on the centerline of the combustor. Over the past 20 years, steady-state Reynolds Averaged Navier Stokes (RANS) solutions with various turbulence models have not been able to mimic the flowfield patterns for swirling flow with a downstream contraction. In this study, Large Eddy Simulation (LES) calculations were performed that correctly predicted the recirculation flow patterns for swirling flow with a downstream contraction. In addition, LES predicted radial profiles of swirl velocity agreed well with measurements, including the solid body vortex core on the centerline of the combustor. RANS produced inferior predictions. Two cases with 45° swirlers and a dump combustor with and without a downstream contraction were modeled. The LES predictions were compared with RANS predictions and Lilley’s measurements. The computational domain included flow through the swirl vanes, the combustor, and the contraction area. The unstructured, parallel CFD-ACE+ code was used, with the Localized Dynamic kinetic Energy Model (LDKM) for subgrid turbulence.

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