Large-Eddy and RANS Simulations of a Normal Shock Train in a Constant-Area Isolator

In future Ultra-High By-Pass Ratio turboengines, the turbomachinery noise (fan and turbine stages mainly) is expected to increase significantly. A review of analytical models and numerical methods to yield both tonal and broadband contributions of such noise sources is presented. The former rely on hybrid methods coupling gust response over very thin flat plates of finite chord length, either isolated or in cascade, and acoustic analogies in free-field and in a duct. The latter yields tonal noise with unsteady Reynolds-Averaged Navier–Stokes (u-RANS) simulations, and broadband noise with Large Eddy Simulations (LES). The analytical models are shown to provide good and fast first sound estimates at pre-design stages, and to easily separate the different noise sources. The u-RANS simulations are now able to give accurate estimates of tonal noise of the most complex asymmetric, heterogeneous fan-Outlet Guiding Vane (OGV) configurations. Wall-modeled LES on rescaled stage configurations have now been achieved on all components: a low-pressure compressor stage, a transonic high-pressure turbine stage and a fan-OGV configuration with good overall sound power level predictions for the latter. In this case, hybrid Lattice–Boltzmann/very large-eddy simulations also appear to be an excellent alternative to yield both contributions accurately at once.

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RANS and Large Eddy Simulation of Internal Combustion Engine Flows—A Comparative Study

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4026165 ◽

2014 ◽

Vol 136 (5) ◽

Cited By ~ 22

Author(s):

Xiaofeng Yang ◽

Saurabh Gupta ◽

Tang-Wei Kuo ◽

Venkatesh Gopalakrishnan

Keyword(s):

Large Eddy Simulation ◽

High Speed ◽

Combustion Engine ◽

Flow Analysis ◽

Partial Geometry ◽

Computational Domain ◽

Mean Flow ◽

Eddy Simulation ◽

Large Eddy ◽

Rans Simulations

A comparative cold flow analysis between Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) cycle-averaged velocity and turbulence predictions is carried out for a single cylinder engine with a transparent combustion chamber (TCC) under motored conditions using high-speed particle image velocimetry (PIV) measurements as the reference data. Simulations are done using a commercial computationally fluid dynamics (CFD) code CONVERGE with the implementation of standard k-ε and RNG k-ε turbulent models for RANS and a one-equation eddy viscosity model for LES. The following aspects are analyzed in this study: The effects of computational domain geometry (with or without intake and exhaust plenums) on mean flow and turbulence predictions for both LES and RANS simulations. And comparison of LES versus RANS simulations in terms of their capability to predict mean flow and turbulence. Both RANS and LES full and partial geometry simulations are able to capture the overall mean flow trends qualitatively; but the intake jet structure, velocity magnitudes, turbulence magnitudes, and its distribution are more accurately predicted by LES full geometry simulations. The guideline therefore for CFD engineers is that RANS partial geometry simulations (computationally least expensive) with a RNG k-ε turbulent model and one cycle or more are good enough for capturing overall qualitative flow trends for the engineering applications. However, if one is interested in getting reasonably accurate estimates of velocity magnitudes, flow structures, turbulence magnitudes, and its distribution, they must resort to LES simulations. Furthermore, to get the most accurate turbulence distributions, one must consider running LES full geometry simulations.

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Numerical Investigation of the Flow Around a Simplified Wheel in a Wheelhouse

Journal of Fluids Engineering ◽

10.1115/1.4004992 ◽

2011 ◽

Vol 133 (11) ◽

Cited By ~ 7

Author(s):

S. Krajnović ◽

S. Sarmast ◽

B. Basara

Keyword(s):

Experimental Data ◽

Numerical Investigation ◽

Large Eddy Simulations ◽

Experimental Investigations ◽

Previous Knowledge ◽

Flow Physics ◽

Large Eddy ◽

Rans Simulations

The flow around generic wheels in wheel housings used in previous experimental investigations is studied using large eddy simulations (LES). A comparison is given here of the results of the simulations with existing experimental data and previous results of RANS simulations. Both instantaneous and time-averaged flows are described, showing agreement with previous knowledge and adding new insight in flow physics. Two different widths of the wheel housing are used in the simulations, and their influence on the flows is studied. The present work shows that the width of the wheel housing has an influence on flows on both the inside and the outside of the wheelhouse.

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Characterization of Shock Train Structures inside Constant-Area Isolators of Model Scramjet Combustors

44th AIAA Aerospace Sciences Meeting and Exhibit ◽

10.2514/6.2006-816 ◽

2006 ◽

Cited By ~ 18

Author(s):

Kuo-Cheng Lin ◽

Chung-Jen Tam ◽

Kevin Jackson ◽

Dean Eklund ◽

Thomas Jackson

Keyword(s):

Shock Train ◽

Constant Area ◽

Scramjet Combustors

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Confinement effects in shock wave/turbulent boundary layer interactions through wall-modelled large-eddy simulations

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.505 ◽

2014 ◽

Vol 758 ◽

pp. 5-62 ◽

Cited By ~ 58

Author(s):

Iván Bermejo-Moreno ◽

Laura Campo ◽

Johan Larsson ◽

Julien Bodart ◽

David Helmer ◽

...

Keyword(s):

Turbulent Flows ◽

Separation Bubble ◽

Incident Shock ◽

Large Eddy Simulations ◽

Periodic Case ◽

Shock Train ◽

Mean Flow ◽

Lateral Confinement ◽

Large Eddy ◽

Shock System

AbstractWe present wall-modelled large-eddy simulations (WLES) of oblique shock waves interacting with the turbulent boundary layers (TBLs) (nominal$\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\delta _{99}=5.4\ \mathrm{mm}$and${\mathit{Re}}_{\theta }\approx 1.4\times 10^4$) developed inside a duct with an almost-square cross-section ($45\ \mathrm{mm}\times 47.5\ \mathrm{mm}$) to investigate three-dimensional effects imposed by the lateral confinement of the flow. Three increasing strengths of the incident shock are considered, for a constant Mach number of the incoming air stream$M\approx 2$, by varying the height (1.1, 3 and 5 mm) of a compression wedge located at a constant streamwise location that spans the top wall of the duct at a 20° angle. Simulation results are first validated with particle image velocimetry (PIV) experimental data obtained at several vertical planes (one near the centre of the duct and three near one of the sidewalls) for the 1.1 and 3 mm-high wedge cases. The instantaneous and time-averaged structure of the flow for the stronger-interaction case (5 mm-high wedge), which shows mean flow reversal, is then investigated. Additional spanwise-periodic simulations are performed to elucidate the influence of the sidewalls, and it is found that the structure and location of the shock system, as well as the size of the separation bubble, are significantly modified by the lateral confinement. A Mach stem at the first reflected interaction is present in the simulation with sidewalls, whereas a regular shock intersection results for the spanwise-periodic case. Low-frequency unsteadiness is observed in all interactions, being stronger for the secondary shock reflections of the shock train developed inside the duct. The downstream evolution of secondary turbulent flows developed near the corners of the duct as they traverse the shock system is also studied.

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