Numerical Study of the Mean and Filtered Characteristics of Turbulent Jets Impinging on Convex and Flat Surfaces Using LES

2012 ◽  
Author(s):  
Adra Benhacine ◽  
Zoubir Nemouchi ◽  
Lyes Khezzar ◽  
Nabil Kharoua
Keyword(s):  
Convex Surface ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulent Jets ◽  
Scale Model ◽  
Wall Jet ◽  
Potential Core ◽  
Flat Surfaces ◽  
Free Jet ◽  
Eddy Simulation

A numerical study of a turbulent plane jet impinging on a convex surface and on a flat surface is presented, using the large eddy simulation approach and the Smagorinski-Lilly sub-grid-scale model. The effects of the wall curvature on the unsteady filtered, and the steady mean, parameters characterizing the dynamics of the wall jet are addressed in particular. In the free jet upstream of the impingement region, significant and fairly ordered velocity fluctuations, that are not turbulent in nature, are observed inside the potential core. Kelvin-Helmholtz instabilities in the shear layer between the jet and the surrounding air are detected in the form of wavy sheets of vorticity. Rolled up vortices are detached from these sheets in a more or less periodic manner, evolving into distorted three dimensional structures. Along the wall jet the Coanda effect causes a marked suction along the convex surface compared with the flat one. As a result, relatively important tangential velocities and a stretching of sporadic streamwise vortices are observed, leading to friction coefficient values on the curved wall higher than those on the flat wall.

Large Eddy Simulation of Cross Flow in Pipe Junction

2018 ◽  
Author(s):  
Jiajun Chen ◽  
Yue Sun ◽  
Hang Zhang ◽  
Dakui Feng ◽  
Zhiguo Zhang
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Exciting Force ◽  
Navier Stokes ◽  
Pipe Network ◽  
Eddy Simulation ◽  
Large Eddy

Mixing in pipe junctions can play an important role in exciting force and distribution of flow in pipe network. This paper investigated the cross pipe junction and proposed an improved plan, Y-shaped pipe junction. The numerical study of a three-dimensional pipe junction was performed for calculation and improved understanding of flow feature in pipe. The filtered Navier–Stokes equations were used to perform the large-eddy simulation of the unsteady incompressible flow in pipe. From the analysis of these results, it clearly appears that the vortex strength and velocity non-uniformity of centerline, can be reduced by Y-shaped junction. The Y-shaped junction not only has better flow characteristic, but also reduces head loss and exciting force. The results of the three-dimensional improvement analysis of junction can be used in the design of pipe network for industry.

scholarly journals An Experimental and Computational Investigation of Flow in a Radial Inlet of an Industrial Pipeline Centrifugal Compressor

1994 ◽  
Author(s):  
M. B. Flathers ◽  
G. E. Bache ◽  
R. Rainsberger
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Results ◽  
Scale Model ◽  
Navier Stokes ◽  
Angle Distribution ◽  
Computational Results ◽  
Industrial Pipeline ◽  
Design Schedule

The flowfield of a complex three dimensional radial inlet for an industrial pipeline centrifugal compressor has been experimentally determined on a half scale model. Based on the experimental results, inlet guide vanes have been designed to correct pressure and swirl angle distribution deficiencies. The unvaned and vaned inlets are analyzed with a commercially available fully 3D viscous Navier-Stokes code. Since experimental results were available prior to the numerical study, the unvaned analysis is considered a postdiction while the vaned analysis is considered a prediction. The computational results of the unvaned inlet have been compared to the previously obtained experimental results. The experimental method utilized for the unvaned inlet is repeated for the vaned inlet and the data has been used to verify the computational results. The paper will discuss experimental, design and computational procedures, grid generation, boundary conditions, and experimental versus computational methods. Agreement between experimental and computational results is very good, both in prediction and postdiction modes. The results of this investigation indicate that CFD offers a measurable advantage in design, schedule and cost and can be applied to complex, three dimensional radial inlets.

Three-Dimensional Numerical Simulation of the Flow around Two Side-by-Side Cylinders of Different Diameters

2014 ◽  
Vol 721 ◽  
pp. 199-202
Author(s):  
Zhen Xiao Bi ◽  
Zhi Han Zhu
Keyword(s):  
Numerical Simulation ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Simulation Method ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Eddy Simulation ◽  
Drag And Lift ◽  
Different Diameters

This paper presents the calculation of hydrodynamic characteristics of two side-by-side cylinders of different diameters in three dimensional incompressible uniform cross flow by using Large-eddy simulation method based on dynamical Smagorinsky-Lilly sub-grid scale model. Solution of the three dimensional N-S equations were obtained by the finite volume method. The numerical simulation focused on investigating the characteristic of the pressure distribution (drag and lift force), vorticity field and turbulence Re=. Results shows that, the asymmetry of the time –averaged velocity distribution in the flow direction behind the two cylinders is very obvious; the frequency of eddy shedding of the small cylinder is about twice of the large one. The turbulence of cylinders is more obvious.

Large Eddy Simulation of Flow around a Cylinder at Re=3900 Using a CFD Code

2011 ◽  
Vol 94-96 ◽  
pp. 1707-1710 ◽  
Author(s):  
Yao Zhen Li
Keyword(s):  
Large Eddy Simulation ◽  
Three Dimensional ◽  
Scale Model ◽  
Subgrid Scale ◽  
Flow Around A Cylinder ◽  
Cpu Time ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Subgrid Scale Model ◽  
Better Than

Flow over circular cylinder at Reynolds number 3900 is studied numerically using the technique of Large Eddy Simulation .As a result, strong three-dimensional characteristics are revealed in flow around a cylinder at Re=3900. As spanwise and streamwise mesh refinement is done respectively, result improves similarly. But the CPU time consumed is too much when refinement meshes are used. Also the simulation result with Smagorinsky subgrid-scale model is investigated to be better than subgrid-scale k model.

scholarly journals Numerical analysis on the performance of Dual Rotor wind turbine

2020 ◽  
Vol 8 (03) ◽  
pp. 352-368
Author(s):  
Hazem Ali Abdel Karim ◽  
Ahmed Reda El-Baz ◽  
Nabil Abdel Aziz Mahmoud ◽  
Ashraf Mostafa Hamed
Keyword(s):  
Wind Turbine ◽  
Rotational Speed ◽  
Pitch Angle ◽  
Numerical Study ◽  
Three Dimensional ◽  
Scale Model ◽  
Power Coefficient ◽  
Peak Performance ◽  
Small Scale ◽  
Cfd Simulations

This study investigates the aerodynamic performance of wind turbines aiming to maximize the power extracted from the wind. The study is focusing on the effect of introducing a second rotor to the main rotor of the wind turbine in what is called a dual rotor wind turbine (DRWT).  The numerical study took place on the performance of small-scale model of wind turbine of 0.9 m diameter using S826 airfoil. Both the Co-rotating and Counter rotating configurations were investigated at different tip speed ratios (TSR) and compared with the performance of the single rotor wind turbine (SRWT). Many parameters were studied for dual rotor turbines. These include the spacing between the two rotors, the pitch angle of the rear rotor and the rotational speed of ratio rear to front rotor. Three-dimensional simulations performed and employed using CFD simulations with Multi Reference Frame (MRF) technique. The Co Rotating Wind Turbine (CWT) and Counter Rotating Wind Turbine (CRWT) found to have better performance compared to that of the SRWT with an increase ranging from 12 to 14% in peak power coefficient. Moreover, the effect of changing the pitch angle of the rear rotor on the overall performance found to be of a negligible effect between angles 0⁰ until 2⁰ degrees tilting toward the front rotor. On the other hand, the ratio of rotational speed of the rear rotor to the front rotor found to cause a further increase in the peak performance of the CWT and CRWT ranging from 3 to 5%.

scholarly journals EFFECT OF THE SPANWISE DISCRETISATION ON TURBULENT FLOW PAST A CIRCULAR CYLINDER

2021 ◽  
Vol 158 (A1) ◽  
Author(s):  
S Kim ◽  
P A Wilson ◽  
Z Chen
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Scale Model ◽  
Spatial Density ◽  
Eddy Simulation ◽  
Large Eddy

The effect of the spanwise discretisation on numerical calculations of the turbulent flow around a circular cylinder is systematically assessed at a subcritical Reynolds number of 10000 in the frame of three-dimensional large-eddy simulation. The eddy-viscosity k-equation subgrid scale model is implemented to evaluate unsteady turbulent flow field. Large-eddy simulation is known to be a reliable method to resolve such a challenging flow field, however, the high computational efforts restrict to low Reynolds number flow or two-dimensional calculations. Therefore, minimum spatial density in the spanwise direction or cylinder axis direction needs to be carefully evaluated in order to reduce high computational resources. In the present study, the influence of the spanwise resolutions to satisfactorily represent three- dimensional complex flow features is discussed in detail and minimum spatial density for high Reynolds flow is suggested.

Effects of the Shape of a Nozzle With Chevrons on the Dynamics of Turbulent Impinging Jet

2016 ◽  
Author(s):  
Sadek Horra ◽  
Zoubir Nemouchi ◽  
Lyes Khezzar
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Impinging Jet ◽  
Point Of View ◽  
Geometrical Parameters ◽  
Free Jet ◽  
Fundamental Point ◽  
Nozzle Shape ◽  
Heat And Fluid Flow ◽  
Plate Distance

This work is a numerical study of a turbulent impinging jet issuing from a nozzle with chevrons. The Reynolds number based on the jet exit velocity and nozzle diameter is equal to 5000 corresponding to a low Mach number of 0.0057 at the nozzle exit. The main objectives of the investigation, inspired by the work of Violato et al. (Int. J. of Heat and Fluid Flow, 37, 2012), are to highlight, from a fundamental point of view, the effects of the nozzle shape and the nozzle-to-plate distance on the mean parameters characterizing the dynamics of the flow in question. The nozzle configurations considered are a circular nozzle without chevrons and nozzles provided with 4 and 6 chevrons. The nozzle-to-plate distance ranges from 2 to 6 nozzle diameters. All the other flow conditions and geometrical parameters used in the different cases treated are identical. Interesting features of the flow are revealed by the obtained results of averaged three-dimensional fields of velocity and turbulent kinetic energy, particularly close to the wall. An attempt is made to bring additional insight into the phenomena in the free jet, the impingement region and the wall jet when using 4, 6 and no chevrons, for different nozzle-to-plate distances.

An Experimental and Computational Investigation of Flow in a Radial Inlet of an Industrial Pipeline Centrifugal Compressor

1996 ◽  
Vol 118 (2) ◽  
pp. 371-384 ◽  
Author(s):  
M. B. Flathers ◽  
G. E. Bache ◽  
R. Rainsberger
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Results ◽  
Scale Model ◽  
Navier Stokes ◽  
Angle Distribution ◽  
Computational Results ◽  
Industrial Pipeline ◽  
Design Schedule

The flow field of a complex three-dimensional radial inlet for an industrial pipeline centrifugal compressor has been experimentally determined on a half-scale model. Based on the experimental results, inlet guide vanes have been designed to correct pressure and swirl angle distribution deficiencies. The unvaned and vaned inlets are analyzed with a commercially available fully three-dimensional viscous Navier–Stokes code. Since experimental results were available prior to the numerical study, the unvaned analysis is considered a postdiction while the vaned analysis is considered a prediction. The computational results of the unvaned inlet have been compared to the previously obtained experimental results. The experimental method utilized for the unvaned inlet is repeated for the vaned inlet and the data have been used to verify the computational results. The paper will discuss experimental, design, and computational procedures, grid generation, boundary conditions, and experimental versus computational methods. Agreement between experimental and computational results is very good, both in prediction and postdiction modes. The results of this investigation indicate that CFD offers a measurable advantage in design, schedule, and cost and can be applied to complex, three-dimensional radial inlets.

A large eddy simulation study to assess low-speed wind and baffle orientation effects in a water treatment sedimentation basin

2018 ◽  
Vol 2017 (2) ◽  
pp. 412-421 ◽  
Author(s):  
Danial Goodarzi ◽  
Kaveh Sookhak Lari ◽  
Abolghasem Alighardashi
Keyword(s):  
Large Eddy Simulation ◽  
Wastewater Treatment Plants ◽  
Numerical Study ◽  
Three Dimensional ◽  
Passive Scalar ◽  
Hydraulic Performance ◽  
Water And Wastewater Treatment ◽  
Particle Tracing ◽  
Eddy Simulation ◽  
Large Eddy

Abstract Hydraulic performance of clarifiers in water and wastewater treatment plants significantly affects the settling efficiency of suspended particles. Structural and ambient parameters can deteriorate this performance. Through a verified three dimensional numerical study, we evaluated hydraulic performance and settling efficiency in a rectangular clarifier with a nominal hydraulic retention time (HRT) of 1 h and options for structural baffles with angles of 20°, 30°, 45° and 70°. Large eddy simulation and Lagrangian particle tracing were used to trace particles 80 to 850 μm in diameter. A passive scalar tracer study was conducted to reveal discrepancies in nominal and real HRT. By posing a 5 m/s wind, ten different scenarios were simulated. The wind caused 17% and 6% reduction in HRT and settling efficiency, respectively. Baffles improved these indicators with the 45° baffle showing the best performance with an approximate settling efficiency of 93%. The study highlighted the importance of using baffles, in particular for small size particles for which influencing factors such as wind deteriorate their settling efficiency.

Numerical Investigation of the Three-Dimensional Flow Structure About a Revolving Wing

2012 ◽  
Author(s):  
Daniel J. Garmann ◽  
Miguel R. Visbal ◽  
Paul D. Orkwis
Keyword(s):  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Vortex System ◽  
Aerodynamic Loads ◽  
Eddy Simulation ◽  
Data Reduction Technique ◽  
The Stability

A numerical study is conducted to examine the vortex structure about a revolving wing in quiescent flow employing a high-fidelity, implicit large eddy simulation (ILES) technique found to be effective in simulating flows that exhibit interspersed regions of laminar, transitional, and turbulent flows. The revolving wing configuration consists of a single, aspect ratio one rectangular plate extended out a distance of 0.5 chords from the origin. Shortly after the onset of the motion, the rotating wing generates a stable and coherent vortex system across the leading edge and wing root that remains throughout the motion. The aerodynamic loads are also analyzed and found to remain mostly constant during the maneuver. Transitional effects on the vortex system are investigated over a range of Reynolds numbers (3,000 < Re < 15,000). It is found that higher Reynolds numbers promote more breakdown of the leading edge and root vortices, but do not alter the stability of the vortex system. The aerodynamic loads also show little sensitivity to Reynolds number with the higher Reynolds numbers producing only moderately higher forces. Comparisons with recent experimental PIV measurements using a PIV-like data reduction technique applied to the computational solution show very favorable agreement with the mid-span velocity and vorticity contours.

Sign in / Sign up

Export Citation Format

Share Document