Influence of diametral acoustic mode on cavity flow dynamics: Zonal large eddy simulation and proper orthogonal decomposition

In this article, we describe the use of proper orthogonal decomposition (POD) to investigate how the dominant wake structures of a bluff-body-stabilized turbulent premixed flame are affected by the heat released by the flame itself. The investigation uses a validated large eddy simulation (LES) to simulate the dynamics of the bluff-body's wake (Blanchard et al., 2014, “Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Wake Dynamics Validation,” ASME J. Eng. Gas Turbines Power, 136(12), p. 122603; Blanchard et al., 2014, “Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Combustion Dynamics Validation,” ASME J. Eng. Gas Turbines Power, 136(12), p. 121504). The numerical simulations allow the effect of heat release, shown as the ratio of the burned to unburned temperatures, to be varied independently from the Damköhler number. Five simulations are reported with varying fractions of the heat release ranging from 0% to 100% of the value of the baseline experiment. The results indicate similar trends reported qualitatively by others, but by using POD to isolate the dominant heat release modes of each simulation, the decomposed data can clearly show how the previously reported flow structures transition from asymmetric shedding in the case of zero heat-release to a much weaker, but fully symmetric shedding mode in the case of full heat release with a much more elongated and stable wake.

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Single Orifice Diesel Injector Flow Characterization and the Impact of Needle Lift Using Large Eddy Simulation and Proper Orthogonal Decomposition

Journal of Fluids Engineering ◽

10.1115/1.4041642 ◽

2018 ◽

Vol 141 (5) ◽

Cited By ~ 2

Author(s):

Mohamed Chouak ◽

Louis Dufresne ◽

Patrice Seers

Keyword(s):

Large Eddy Simulation ◽

Proper Orthogonal Decomposition ◽

Three Dimensional ◽

Orthogonal Decomposition ◽

Wall Turbulence ◽

Mean Flow ◽

Eddy Simulation ◽

Large Eddy ◽

Proper Orthogonal ◽

The Impact

The flow in the injector's sac volume has been reported to influence diesel-injector nozzle flow, but few studies have characterized sac volume. Our study modeled flow in the sac volume using a large Eddy simulation (LES) approach to gain better insight into the complexity of the flow dynamics. It focused on the effect of fixed needle lifts on sac-volume internal flow of a single-hole injector with emphasis on large-scale unsteadiness; three-dimensional proper orthogonal decomposition (POD) was used to analyze the flow. The near-wall turbulence resolution of the elaborated computational fluid dynamics (CFD) model has been validated with direct numerical simulation (DNS) results in the canonical case of fully developed channel flow. The main findings are: (1) an enlarging flow jet entering the sac volume with decreasing small scales of turbulence was observed as needle lift increased. (2) three-dimensional POD revealed that the mean flow energy was nearly constant at low needle lifts (6%, 8%, and 10%) and decreased twofold at the higher needle lift of 31%. (3) The analysis of fluctuating modes revealed that flow restructuring occurred with increasing needle lift as three different energy distributions were observed with the lowest (6%), intermediary (8%, 10%, and 16%), and highest needle lifts (31%). (4) Finally, the analysis of the POD-reduced-order model has shown that the lowest frequency of mode 1, which carries the highest fluctuating energy, is responsible for the oscillation of the main rotating structure within the sac volume that causes fuel-jet enlarging/narrowing with time. This oscillation of the main structure was found to decrease with increased needle lift.

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Adaptation of Phase-Lagged Boundary Conditions to Large Eddy Simulation in Turbomachinery Configurations

Journal of Turbomachinery ◽

10.1115/1.4032044 ◽

2015 ◽

Vol 138 (4) ◽

Cited By ~ 3

Author(s):

Gaelle Mouret ◽

Nicolas Gourdain ◽

Lionel Castillon

Keyword(s):

Large Eddy Simulation ◽

Industrial Applications ◽

Orthogonal Decomposition ◽

Navier Stokes ◽

Compression Method ◽

Promising Technique ◽

Computing Power ◽

Eddy Simulation ◽

Large Eddy ◽

Proper Orthogonal

With the increase in computing power, large eddy simulation (LES) emerges as a promising technique to improve both knowledge of complex physics and reliability of turbomachinery flow predictions. However, these simulations are very expensive for industrial applications, especially when a 360 deg configuration should be considered. The objective of this paper is thus to adapt the well-known phase-lagged conditions to the LES approach by replacing the traditional Fourier series decomposition (FSD) with a compression method that does not make any assumptions on the spectrum of the flow. Several methods are reviewed, and the proper orthogonal decomposition (POD) is retained. This new method is first validated on a flow around a circular cylinder with rotating downstream blocks. The results show significant improvements with respect to the FSD. It is then applied to unsteady Reynolds-averaged Navier–Stokes (URANS) simulations of a single-stage compressor in 2.5D and 3D as a first validation step toward single-passage LES of turbomachinery configuration.

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Adaptation of Phase-Lagged Boundary Conditions to Large-Eddy Simulation in Turbomachinery Configurations

Volume 2B: Turbomachinery ◽

10.1115/gt2015-42516 ◽

2015 ◽

Cited By ~ 3

Author(s):

Gaelle Mouret ◽

Nicolas Gourdain ◽

Lionel Castillon

Keyword(s):

Fourier Series ◽

Large Eddy Simulation ◽

Industrial Applications ◽

Orthogonal Decomposition ◽

Compression Method ◽

Promising Technique ◽

Computing Power ◽

Eddy Simulation ◽

Large Eddy ◽

Proper Orthogonal

With the increase in computing power, large eddy simulation (LES) emerges as a promising technique to improve both knowledge of complex physics and reliability of turbomachinery flow predictions. However these simulations are very expensive for industrial applications, especially when a 360° configuration should be considered. The objective of this paper is thus to improve the well-known phase lagged conditions to the LES approach by replacing the traditional Fourier Series Decomposition (FSD) by a compression method which does not make any assumption on the spectrum of the flow. Several methods are reviewed and the Proper Orthogonal Decomposition (POD) is retained. This new method is first validated on a flow around a circular cylinder with rotating downstream blocks. The results show significant improvements with respect to FSD. It is then applied to URANS simulations of a single stage compressor in 2.5D and 3D as a first validation step toward single-passage LES of turbomachinery configuration.

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