scholarly journals NUMERICAL INVESTIGATION OF TURBULENT FORCED CONVECTIVE FLOWS OVER A PAIR OF CIRCULAR CYLINDERS

2012 ◽  
Vol 11 (1-2) ◽  
pp. 77 ◽  
Author(s):  
E. D. Dos Santos ◽  
F. M. V. Da Silva ◽  
I. C. Acunha Jr. ◽  
M. M. Galarça ◽  
L. A. Isoldi ◽  
...  
Keyword(s):  
Turbulent Flows ◽  
Fluid Dynamic ◽  
Circular Cylinders ◽  
Streamwise Direction ◽  
Convective Flows ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Thermal Patterns ◽  
Prandtl Numbers ◽  
Volume Method

The present study presents large eddy simulation (LES) of forced convective heat transfer in transient, two-dimensional, incompressible turbulent flows over a pair of cylinders with two different arrangements: 1) with two circular cylinders in tandem (both cylinders are in line with the streamwise direction of the flow, β = 0º) and 2) two side-by-side circular cylinders (where both cylinders are placed transversally to the streamwise direction of the flow, β = 90º). The dynamic Smagorinsky model is employed for the sub-grid treatment. The simulations are based on the finite volume method solution for the conservation equations of mass, momentum and energy. Both simulations are performed with Reynolds and Prandtl numbers of ReD = 22000 and Pr = 0.71, respectively. The results showed that the transient fluid dynamic and thermal patterns are strongly affected by the configuration of circular cylinders. The kind of arrangement led to a difference of nearly 20 % for time-averaged Nusselt number (NuD).

Large Eddy Simulation of Hydraulic Characteristics of Flow around Two Parallel Circular Cylinders

2012 ◽  
Vol 468-471 ◽  
pp. 1862-1865
Author(s):  
X.J. Zhao ◽  
W.L. Wei ◽  
Xi Wang ◽  
Ming Qin Liu
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flows ◽  
Circular Cylinders ◽  
Hydraulic Characteristics ◽  
Step Method ◽  
Fractional Step Method ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Engineering Problems ◽  
Total Velocity

large eddy simulation cooperated with a physical fractional-step method was applied to simulate steady flow around two parallel circular cylinders. The total velocity vectors, pressure contours and vorticity magnitude are obtained. The modeling results conform to physical law, and show that the large eddy simulation theory has powerful capacity in simulation of microstructures of turbulent flows, and can be widely applied to the solution of real engineering problems.

Large Eddy Simulation of Gas-Liquid Two-Phase Flow for a Nested Type Fixed-Cone Valve

2012 ◽  
Vol 170-173 ◽  
pp. 2458-2463
Author(s):  
Y.L. Liu ◽  
B. Lv ◽  
W.L. Wei
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flows ◽  
Free Fluid ◽  
Step Method ◽  
Fractional Step Method ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Volume Method ◽  
Free Fluid Surface

large eddy simulation cooperated with a physical fractional-step method is applied to simulate steady flow around a nested type fixed-cone valve; and the equations are solved with the finite volume method. The free fluid surface is simulated by the VOF method. The pressure contours and vorticity magnitude are obtained. The modeling results conform to physical law, and show that the large eddy simulation theory has powerful capacity in simulation of microstructures of turbulent flows, and the function of the nested type fixed-cone valve for energy dissipating is good.

Simulating flow separation from continuous surfaces: routes to overcoming the Reynolds number barrier

2009 ◽  
Vol 367 (1899) ◽  
pp. 2885-2903 ◽  
Author(s):  
Michael Leschziner ◽  
Ning Li ◽  
Fabrizio Tessicini
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Major Elements ◽  
Wall Layer ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Models ◽  
High Reynolds ◽  
Near Wall

This paper provides a discussion of several aspects of the construction of approaches that combine statistical (Reynolds-averaged Navier–Stokes, RANS) models with large eddy simulation (LES), with the objective of making LES an economically viable method for predicting complex, high Reynolds number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail: one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

scholarly journals Large-Eddy Simulation Analyses of Heated Urban Canyon Facades

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3078
Author(s):  
Carlo Cintolesi ◽  
Francesco Barbano ◽  
Silvana Di Sabatino
Keyword(s):  
Urban Canopy ◽  
Pollutant Removal ◽  
Present Contribution ◽  
Convective Flows ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Isothermal Case ◽  
Definition Of ◽  
New Formulation ◽  
Heating Up

Thermal convective flows are common phenomena in real urban canyons and strongly affect the mechanisms of pollutant removal from the canyon. The present contribution aims at investigating the complex interaction between inertial and thermal forces within the canyon, including the impacts on turbulent features and pollutant removal mechanisms. Large-eddy simulations reproduce infinitely long square canyons having isothermal and differently heated facades. A scalar source on the street mimics the pollutant released by traffic. The presence of heated facades triggers convective flows which generate an interaction region around the canyon-ambient interface, characterised by highly energetic turbulent fluxes and an increase of momentum and mass exchange. The presence of this region of high mixing facilitates the pollutant removal across the interface and decreases the urban canopy drag. The heating-up of upwind facade determines favourable convection that strengthens the primary internal vortex and decreases the pollutant concentration of the whole canyon by 49% compare to the isothermal case. The heating-up of the downwind facade produces adverse convection counteracting the wind-induced motion. Consequently, the primary vortex is less energetic and confined in the upper-canyon area, while a region of almost zero velocity and high pollution concentration (40% more than the isothermal case) appears at the pedestrian level. Finally, numerical analyses allow a definition of a local Richardson number based on in-canyon quantities only and a new formulation is proposed to characterise the thermo-dynamics regimes.

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