Compression of a Swirling and Tumbling Flow

Large Scale ◽

Large Eddy Simulations ◽

Flow Structures ◽

Large Eddy ◽

Tumbling Motion ◽

The effect of compression on a swirling/tumbling flow is studied using Large-Eddy Simulations (LES). In this study the geometry investigated is a cylinder with an artificially created swirling/tumbling motion. During compression the evolution of turbulence and vorticity are investigated. An increase of turbulence and vorticity is observed and linked to vorticity-dilatation interaction. It is shown that for swirling/tumbling flows turbulent kinetic energy available at Top Dead Center (TDC) is introduced by the piston through the vorticity-dilatation interaction and that turbulence increases independently of the presence of instability of the large scale flow structures.

Assessment Measures for LES Applications

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2006-98015 ◽

2006 ◽

Author(s):

I. Celik ◽

M. Klein ◽

J. Janicka

Keyword(s):

Kinetic Energy ◽

Power Spectra ◽

Grid Size ◽

Large Eddy Simulations ◽

Large Eddy ◽

Modeling Errors ◽

The Common ◽

Assessment Measures ◽

Molecular Viscosity

Anticipating that Large Eddy Simulations will increasingly become the future engineering tool for research, development and design, it is deemed necessary to formulate some quality assessment measures that can be used to judge the resolution of turbulent scales and the accuracy of predictions. In this context some new and refined measures are proposed above and beyond those already published by the authors in the common literature. These new measures involve (a) fraction of total turbulent kinetic energy, (b) relative grid size with respect to Kolmogorov or Taylor scales, (c) relative effective sub-grid/numerical viscosity with respect to molecular viscosity, and (d) some property related to power spectra of turbulent kinetic energy. In addition, an attempt is made to segregate the contributions from numerical and modeling errors. Proposed measures are applied to various benchmark cases, and validated against fully resolved LES and/or DNS whenever possible. Along the same line of thinking, the authors present a perspective for verification of under-resolved direct numerical simulations.

Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development ◽

Large Eddy Simulation of a Turbulent Non-Reacting Spray Jet

10.1115/icef2015-1033 ◽

2015 ◽

Cited By ~ 5

Author(s):

B. Hu ◽

S. Banerjee ◽

K. Liu ◽

D. Rajamohan ◽

J. M. Deur ◽

...

Keyword(s):

Kinetic Energy ◽

Large Eddy Simulation ◽

Cell Size ◽

Adaptive Mesh Refinement ◽

Large Scale ◽

Flow Behavior ◽

Similarity Index ◽

Eddy Simulation ◽

We performed Large Eddy Simulation (LES) of a turbulent non-reacting n-Heptane spray jet, referred to as Spray H in the Engine Combustion Network (ECN), and executed a data analysis focused on key LES metrics such as fraction of resolved turbulent kinetic energy and similarity index. In the simulation, we used the dynamic structure model for the sub-grid stress, and the Lagrangian-based spray-parcel models coupled with the blob-injection model. The finest mesh-cell size used was characterized by an Adaptive Mesh Refinement (AMR) cell size of 0.0625 mm. To obtain ensemble statistics, we performed 28 numerical realizations of the simulation. Demonstrated by the comparison with experimental data in a previous study [7], this LES has accurately predicted global quantities, such as liquid and vapor penetrations. The analysis in this work shows that 14 realizations of LES are sufficient to provide a reasonable representation of the average flow behavior that is benchmarked against the 28-realization ensemble. With the current mesh, numerical schemes, and sub-grid scale turbulence model, more than 95% of the turbulent kinetic energy is directly resolved in the flow regions of interest. The large-scale flow structures inferred from a statistical analysis reveal a region of disorganized flow around the peripheral region of the spray jet, which appears to be linked to the entrainment process.

Large-eddy simulations of turbulent mixing layers using the stretched-vortex model

Journal of Fluid Mechanics ◽

10.1017/s002211201000580x ◽

2011 ◽

Vol 671 ◽

pp. 507-534 ◽

Cited By ~ 10

Author(s):

T. W. MATTNER

Keyword(s):

Large Scale ◽

Large Eddy Simulations ◽

Mixing Layers ◽

Reynolds Stresses ◽

Mean Velocity ◽

Subgrid Model ◽

Large Eddy ◽

Schmidt Numbers ◽

Self Similar ◽

The stretched-vortex subgrid model is used to run large-eddy simulations of temporal mixing layers at various Reynolds and Schmidt numbers, with different initial and boundary conditions. A self-similar flow is obtained, during which the growth rate, mean velocity and Reynolds stresses are in accord with experimental results. However, predictions of the amount of mixed fluid, and of the variation in its composition across the layer, are excessive, especially at high Schmidt number. More favourable comparisons between experiment and simulation are obtained when the large-scale flow is quasi-two-dimensional; however, such states are not self-similar and not sustainable. Present model assumptions lead to predictions of the continued subgrid spectrum with a viscous cutoff that is dependent on grid resolution.

On the prediction of turbulent kinetic energy in channel flow using wall-modeled large eddy simulations

AIAA Scitech 2020 Forum ◽

10.2514/6.2020-1329 ◽

2020 ◽

Author(s):

Mohamed Sayed ◽

Muhamed Hadziabdic ◽

Abdelouahab Dehbi ◽

Bojan Niceno ◽

Konstantin Mikityuk

Keyword(s):

Kinetic Energy ◽

Channel Flow ◽

Large Eddy Simulations ◽

Correction: On the prediction of turbulent kinetic energy in channel flow using wall-modeled large eddy simulations

AIAA Scitech 2020 Forum ◽

10.2514/6.2020-1329.c1 ◽

2020 ◽

Author(s):

Mohamed Sayed ◽

Muhamed Hadziabdic ◽

Abdelouahab Dehbi ◽

Bojan Niceno ◽

Konstantin Mikityuk

Keyword(s):

Kinetic Energy ◽

Channel Flow ◽

Large Eddy Simulations ◽

Reconstruction of large scale flow structures in a stirred tank from limited sensor data

AIChE Journal ◽

10.1002/aic.17348 ◽

2021 ◽

Author(s):

Kirill Mikhaylov ◽

Stelios Rigopoulos ◽

George Papadakis

Keyword(s):

Large Scale ◽

Sensor Data ◽

Stirred Tank ◽

Flow Structures ◽

Plasma assisted combustion: Effects of O3 on large scale turbulent combustion studied with laser diagnostics and Large Eddy Simulations

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2014.05.092 ◽

2015 ◽

Vol 35 (3) ◽

pp. 3487-3495 ◽

Cited By ~ 18

Author(s):

A. Ehn ◽

J.J. Zhu ◽

P. Petersson ◽

Z.S. Li ◽

M. Aldén ◽

...

Keyword(s):

Turbulent Combustion ◽

Large Scale ◽

Laser Diagnostics ◽

Large Eddy Simulations ◽

Plasma Assisted Combustion ◽

Investigation of the Large Scale Flow Structures in Dual Planar Attaching Jets

44th AIAA Aerospace Sciences Meeting and Exhibit ◽

10.2514/6.2006-313 ◽

2006 ◽

Author(s):

Nan Gao ◽

Dan Ewing

Keyword(s):

Large Scale ◽

Flow Structures ◽

Investigation on hydrodynamic forces leading to coarse particle entrainment using Large-Eddy Simulations

10.5194/egusphere-egu21-13221 ◽

2021 ◽

Author(s):

Gaston Latessa ◽

Angela Busse ◽

Manousos Valyrakis

Keyword(s):

Experimental Data ◽

Flow Field ◽

Large Scale ◽

Large Eddy Simulations ◽

Flow Conditions ◽

Mean Flow ◽

Protection Measures ◽

Practical Applications ◽

Particle Entrainment ◽

The prediction of particle motion in a fluid flow environment presents several challenges from the quantification of the forces exerted by the fluid onto the solids -normally with fluctuating behaviour due to turbulence- and the definition of the potential particle entrainment from these actions. An accurate description of these phenomena has many practical applications in local scour definition and to the design of protection measures.In the present work, the actions of different flow conditions on sediment particles is investigated with the aim to translate these effects into particle entrainment identification through analytical solid dynamic equations.Large Eddy Simulations (LES) are an increasingly practical tool that provide an accurate representation of both the mean flow field and the large-scale turbulent fluctuations. For the present case, the forces exerted by the flow are integrated over the surface of a stationary particle in the streamwise (drag) and vertical (lift) directions, together with the torques around the particle&#8217;s centre of mass. These forces are validated against experimental data under the same bed and flow conditions.The forces are then compared against threshold values, obtained through theoretical equations of simple motions such as rolling without sliding. Thus, the frequency of entrainment is related to the different flow conditions in good agreement with results from experimental sediment entrainment research.A thorough monitoring of the velocity flow field on several locations is carried out to determine the relationships between velocity time series at several locations around the particle and the forces acting on its surface. These results a relevant to determine ideal locations for flow investigation both in numerical and physical experiments.Through numerical experiments, a large number of flow conditions were simulated obtaining a full set of actions over a fixed particle sitting on a smooth bed. These actions were translated into potential particle entrainment events and validated against experimental data. Future work will present the coupling of these LES models with Discrete Element Method (DEM) models to verify the entrainment phenomena entirely from a numerical perspective.