Large eddy simulation of a forward–backward facing step for acoustic source identification

Addad, Yacine; Laurence, Dominique; Talotte, Corinne; Jacob, Marc C.

doi:10.1016/s0142-727x(03)00050-x

Cited by 58 publications

(24 citation statements)

References 15 publications

(10 reference statements)

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“…13 were successfully reproduced in a large eddy simulation ͑LES͒ performed by the same group. 14 It was confirmed that the largest acoustic source is located in the separated region upstream of the wall discontinuity. In recent papers, Camussi et al 15,16 measured the pressure fluctuations at the wall of a shallow cavity representing a backward-forward step sequence.…”

Section: Statistical Properties Of Wall Pressure Fluctuations Over a mentioning

confidence: 84%

Statistical properties of wall pressure fluctuations over a forward-facing step

et al. 2008

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This work describes an experimental study of the flow field and wall pressure fluctuations induced by quasi-two-dimensional incompressible turbulent boundary layers overflowing a forward-facing step (FFS). Pressure fluctuations are measured upstream and downstream of an instrumented FFS step model installed inside a large scale recirculation water tunnel, while two-dimensional (2D) velocity fields are measured close to the step via 2D particle image velocimetry (PIV). The overall flow physics is studied in terms of averaged velocity and vorticity fields for different Reynolds numbers based on the step's height. The wall pressure statistics are analyzed in terms of several indicators, including the root mean squares and probability density functions of the pressure fluctuations, demonstrating that the most relevant flow structure is the unsteady recirculation bubble formed at the reattachment region downstream of the step. Pressure spectra and cross correlations are computed as well, and the convection velocity characterizing the propagation of hydrodynamic perturbations is determined as a function of the distance to the vertical side of the step. The simultaneous measurement of time-resolved PIV fields and wall pressure signals enabled us to compute the pressure/velocity cross correlations in the region downstream of the step and substantiated the relevant role played by the recirculation bubble. (C) 2008 American Institute of Physics

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Section: Statistical Properties Of Wall Pressure Fluctuations Over a mentioning

confidence: 84%

Statistical properties of wall pressure fluctuations over a forward-facing step

et al. 2008

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“…The Smagorinsky SGS model was used with C s = 0.1, which is recommended by (Shah, 1998) for flow past a blunt obstacle. Note that the Smagorinsky model is widely used by researchers to simulate this kind of flow, with considerable success (Shah, 1998;Hanna et al, 2002;Addad et al, 2003;Stoesser et al, 2003). Shah (1998) and Stoesser et al (2003) also compared the Smagorinsky model with the dynamic model for flow over bluff obstacles.…”

Section: Large-eddy Simulationmentioning

confidence: 99%

LES and RANS for Turbulent Flow over Arrays of Wall-Mounted Obstacles

Xie

Castro

2006

Flow Turbulence Combust

232

138

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Abstract. Large-eddy simulation (LES) has been applied to calculate the turbulent flow over staggered wall-mounted cubes and staggered random arrays of obstacles with area density 25%, at Reynolds numbers between 5 × 10 3 and 5 × 10 6 , based on the free stream velocity and the obstacle height. Re = 5 × 10 3 data were intensively validated against direct numerical simulation (DNS) results at the same Re and experimental data obtained in a boundary layer developing over an identical roughness and at a rather higher Re. The results collectively confirm that Reynolds number dependency is very weak, principally because the surface drag is predominantly form drag and the turbulence production process is at scales comparable to the roughness element sizes. LES is thus able to simulate turbulent flow over the urbanlike obstacles at high Re with grids that would be far too coarse for adequate computation of corresponding smooth-wall flows. Comparison between LES and steady Reynolds-averaged Navier-Stokes (RANS) results are included, emphasising that the latter are inadequate, especially within the canopy region.

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“…Reliability and numerical accuracy of LES for complex turbulent flows have been well established through many comparative studies between LES and experimental measurements. Recently, for example, even a separated turbulent flow over a forward-backward facing step has been successfully simulated with LES by Addad et al 9) They also demonstrated in a different study that the same LES could be applied to accurately simulate a buoyant wall-jet. 10) Since the present flow geometry is a combination of separated flow and curved wall-jet, it is expected that LES is capable of producing reliable computational results for the flow geometry of our concern.…”

Section: Numerical Analysis Of 3-d Unsteady Compressiblementioning

confidence: 99%

A Noble Gas Wiping System to Prevent the Edge Overcoating in Continuous Hot-dip Galvanizing

Ahn

Chung

2006

ISIJ Int.

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A noble method is proposed to prevent the edge overcoating (EOC) that may develop near the edge of the steel strip in the gas wiping process of continuous hot-dip galvanizing. In our past study (ISIJ International, Vol. 27 (2003), No. 10, pp. 1495No. 10, pp. -1501, it was found that the EOC is caused by the alternating vortices which are generated by the collision of two opposing jets in the region outside the steel strip. In the present study, the flow field around the gas wiping system has been analyzed numerically and it was found that when the two opposing jets collide at an angle much less than 180°, the alternating vortices disappear and the impinging pressure on the steel strip surface becomes nearly uniform. In order to deflect both jets downward by a certain angle, a cylinder with small diameter is installed tangentially to each exit of the lower lips of the two-dimensional opposing jets. The three dimensional flow field with the proposed device is analyzed numerically by using the commercial CFD software, STAR-CD. And the coating thickness is calculated by solving the boundary layer momentum equation with an integral analysis method. In order to compare the present noble method with the conventional edge baffle plate method to prevent the EOC, the flow field with edge baffle plates is also calculated. The calculation results show that the tangentially installed cylinder at the lower lip of the jet exit is significantly more effective than the edge baffle plate.KEY WORDS: continuous hot-dip galvanizing; edge overcoating; impinging jet; gas wiping.In the present study, the 3-D unsteady compressible turbulent flow field with the proposed configuration with a pair of cylinders in the continuous hot-dip galvanizing system is simulated by using a commercial CFD software, to find out how the cylinder affects the flow behavior of the wiping gas. The simulation results for the impinging pressure and the shear stress on the steel strip surface are used to calculate the thickness of the adhered zinc film by the noble integral analysis method of the boundary layer momentum equation. 7) In addition, the flow field generated by the edge baffle plate is also analyzed to compare its performance for reduction of the EOC with that of the cylinder installed at the lower lip of the air knife nozzle. Numerical Analysis Numerical Analysis of 3-D Unsteady CompressibleFlow In the continuous hot-dip galvanizing process, a heattreated steel strip is passed through a molten zinc bath and the molten zinc is adhered on the steel strip surfaces. Usually, the thickness of the adhered zinc film is nearly 10 times thicker than desired one, and the excessive zinc is removed by nitrogen gas jets. This wiping gas jet system is often called the air knife system. Usually, the Mach number of the nitrogen gas flow is in a range of 0.3-0.6. Therefore, in addition to the continuity and momentum equations, the equation of state and the energy equation are needed. Large Eddy Simulation (LES) is used to solve the turbulent equations, of which f...

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Large eddy simulation of a forward–backward facing step for acoustic source identification

Cited by 58 publications

References 15 publications

Statistical properties of wall pressure fluctuations over a forward-facing step

Statistical properties of wall pressure fluctuations over a forward-facing step

LES and RANS for Turbulent Flow over Arrays of Wall-Mounted Obstacles

A Noble Gas Wiping System to Prevent the Edge Overcoating in Continuous Hot-dip Galvanizing

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