Large-Eddy Simulations and Lidar Measurements of Vortex-Pair Breakup in Aircraft Wakes

AIAA Journal ◽  
10.2514/2.535 ◽  
1998 ◽  
Vol 36 (8) ◽  
pp. 1439-1445 ◽  
Author(s):  
D. C. Lewellen ◽  
W. S. Lewellen ◽  
L. R. Poole ◽  
R. J. DeCoursey ◽  
G. M. Hansen ◽  
...  
Keyword(s):  
Vortex Pair ◽  
Large Eddy Simulations ◽  
Large Eddy ◽  
Lidar Measurements

Large-eddy simulations and lidar measurements of vortex-pair breakup in aircraft wakes

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1439-1445 ◽  
Author(s):  
D. C. Lewellen ◽  
W. S. Lewellen ◽  
L. R. Poole ◽  
C. A. Hostetler ◽  
R. J. DeCoursey ◽  
...  
Keyword(s):  
Vortex Pair ◽  
Large Eddy Simulations ◽  
Large Eddy ◽  
Lidar Measurements

Large Eddy Simulations of Film-Cooling Flows With a Micro-Ramp Vortex Generator

2011 ◽  
Author(s):  
Aaron F. Shinn ◽  
S. Pratap Vanka
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Large Eddy Simulations ◽  
Wind Tunnel Experiments ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Flows ◽  
Large Eddy

Large Eddy Simulations were performed to study the effect of a micro-ramp on an inclined turbulent jet interacting with a cross-flow in a film-cooling configuration. The micro-ramp vortex generator is placed downstream of the film-cooling jet. Changes in vortex structure and film-cooling effectiveness are evaluated and the genesis of the counter-rotating vortex pair in the jet is discussed. Results are reported with the jet modeled using a plenum/pipe configuration. This configuration was designed based on previous wind tunnel experiments at NASA Glenn Research Center, and the present results are meant to supplement those experiments. It is found that the micro-ramp improves film-cooling effectiveness by generating near-wall counter-rotating vortices which help entrain coolant from the jet and transport it to the surface. The pair of vortices generated by the micro-ramp are of opposite sense to the vortex pair embedded in the jet.

scholarly journals Comparison of Large Eddy Simulations of a convective boundary layer with wind LIDAR measurements

2012 ◽  
Vol 8 (1) ◽  
pp. 83-86 ◽  
Author(s):  
J. G. Pedersen ◽  
M. Kelly ◽  
S.-E. Gryning ◽  
R. Floors ◽  
E. Batchvarova ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Geostrophic Wind ◽  
Large Eddy Simulations ◽  
Horizontal Wind ◽  
Convective Boundary ◽  
Horizontal Wind Speed ◽  
Large Eddy ◽  
Lidar Measurements ◽  
Wind Lidar

Abstract. Vertical profiles of the horizontal wind speed and of the standard deviation of vertical wind speed from Large Eddy Simulations of a convective atmospheric boundary layer are compared to wind LIDAR measurements up to 1400 m. Fair agreement regarding both types of profiles is observed only when the simulated flow is driven by a both time- and height-dependent geostrophic wind and a time-dependent surface heat flux. This underlines the importance of mesoscale effects when the flow above the atmospheric surface layer is simulated with a computational fluid dynamics model.

Large-eddy simulations of a round jet in crossflow

1999 ◽  
Vol 379 ◽  
pp. 71-104 ◽  
Author(s):  
LESTER L. YUAN ◽  
ROBERT L. STREET ◽  
JOEL H. FERZIGER
Keyword(s):  
Coherent Structures ◽  
Vortex Pair ◽  
Large Eddy Simulations ◽  
Back Side ◽  
Round Jet ◽  
Turbulent Statistics ◽  
Jet Trajectory ◽  
Large Eddy ◽  
Crossflow Velocity ◽  
Counter Rotating Vortex Pair

This paper reports on a series of large-eddy simulations of a round jet issuing normally into a crossflow. Simulations were performed at two jet-to-crossflow velocity ratios, 2.0 and 3.3, and two Reynolds numbers, 1050 and 2100, based on crossflow velocity and jet diameter. Mean and turbulent statistics computed from the simulations match experimental measurements reasonably well. Large-scale coherent structures observed in experimental flow visualizations are reproduced by the simulations, and the mechanisms by which these structures form are described. The effects of coherent structures upon the evolution of mean velocities, resolved Reynolds stresses, and turbulent kinetic energy along the centreplane are discussed. In this paper, the ubiquitous far-field counter-rotating vortex pair is shown to originate from a pair of quasi-steady ‘hanging’ vortices. These vortices form in the skewed mixing layer that develops between jet and crossflow fluid on the lateral edges of the jet. Axial flow through the hanging vortex transports vortical fluid from the near-wall boundary layer of the incoming pipe flow to the back side of the jet. There, the hanging vortex encounters an adverse pressure gradient and breaks down. As this breakdown occurs, the vortex diameter expands dramatically, and a weak counter-rotating vortex pair is formed that is aligned with the jet trajectory.

scholarly journals Evaluation of large-eddy simulations forced with mesoscale model output for a multi-week period during a measurement campaign

2017 ◽  
Vol 17 (11) ◽  
pp. 7083-7109 ◽  
Author(s):  
Rieke Heinze ◽  
Christopher Moseley ◽  
Lennart Nils Böske ◽  
Shravan Kumar Muppa ◽  
Vera Maurer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mesoscale Model ◽  
Large Eddy Simulations ◽  
Model Output ◽  
Synoptic Scale ◽  
High Definition ◽  
Shallow Cumulus ◽  
Large Eddy ◽  
Lidar Measurements ◽  
The Mean

Abstract. Large-eddy simulations (LESs) of a multi-week period during the HD(CP)2 (High-Definition Clouds and Precipitation for advancing Climate Prediction) Observational Prototype Experiment (HOPE) conducted in Germany are evaluated with respect to mean boundary layer quantities and turbulence statistics. Two LES models are used in a semi-idealized setup through forcing with mesoscale model output to account for the synoptic-scale conditions. Evaluation is performed based on the HOPE observations. The mean boundary layer characteristics like the boundary layer depth are in a principal agreement with observations. Simulating shallow-cumulus layers in agreement with the measurements poses a challenge for both LES models. Variance profiles agree satisfactorily with lidar measurements. The results depend on how the forcing data stemming from mesoscale model output are constructed. The mean boundary layer characteristics become less sensitive if the averaging domain for the forcing is large enough to filter out mesoscale fluctuations.

Large Eddy Simulations of Film-Cooling Flows With a Micro-Ramp Vortex Generator

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Aaron F. Shinn ◽  
S. Pratap Vanka
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Large Eddy Simulations ◽  
Wind Tunnel Experiments ◽  
Turbulent Structures ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Large Eddy

Large eddy simulations were performed to study the effect of a micro-ramp on an inclined turbulent jet interacting with a cross-flow in a film-cooling configuration. The micro-ramp vortex generator is placed downstream of the film-cooling jet. Changes in vortex structure and film-cooling effectiveness are evaluated. Coherent turbulent structures characteristic of a jet in a cross-flow are analyzed and the genesis of the counter-rotating vortex pair in the jet is discussed. Results are reported for two film-cooling configurations, where the primary difference is the way the jet inflow boundary conditions are prescribed. In the first configuration, the jet conditions are prescribed using a precursor simulation and in the second the jet is modeled using a plenum/pipe configuration. The latter configuration was designed based on previous wind tunnel experiments at NASA Glenn Research Center, and the present results are meant to supplement those experiments. It is found that the micro-ramp improves film-cooling effectiveness by generating near-wall counter-rotating vortices which help entrain coolant from the jet and transport it to the surface. The pair of vortices generated by the micro-ramp are of opposite sense to the vortex pair embedded in the jet.

Large Eddy Simulations of a Three-Row Leading Edge Film Cooling Geometry

2008 ◽  
Author(s):  
Sai Shrinivas Sreedharan ◽  
Danesh K. Tafti
Keyword(s):  
Film Cooling ◽  
Lateral Displacement ◽  
Vortex Pair ◽  
Leading Edge ◽  
Large Eddy Simulations ◽  
Cylinder Surface ◽  
Stagnation Region ◽  
Single Vortex ◽  
Blowing Ratio ◽  
Large Eddy

A three-row leading edge film cooling geometry is investigated using Large-Eddy Simulations (LES) at a freestream Reynolds number of 32,000 and blowing ratio of 0.5 with lateral injection of 45° to the surface and 90° compound injection. The stagnation jet interacts with the mainstream through the generation of ring vortices which quickly breakdown and convect along the cylinder surface. The coolant penetrates the mainstream both laterally and normal to the surface resulting in increased mixing and turbulence generation. As the coolant loses transverse and lateral momentum it is pushed back to the surface in the stagnation region after which it convects downstream along the blade surface. Surface coverage is uniform but weak with spanwise-averaged effectiveness ranging from 0.1 to 0.3 in the stagnation region. The primary off-stagnation coolant and mainstream interaction is through the generation of a counter-rotating vortex pair in the immediate wake, but which quickly degenerates to a single vortex which entrains free-stream fluid near the surface at the aft-end of the jet. In contrast to the stagnation row, the coolant stays in close proximity to the surface and does not undergo a large lateral displacement along the spanwise pitch. As a consequence it provides good local coverage along its trajectory but barely covers half the lateral pitch. Hence, spanwise-averaged effectiveness is of the same order as at stagnation starting at 0.3 downstream of injection to 0.1 about 6d downstream.

Large-eddy simulations of the vortex-pair breakup in aircraft wakes

AIAA Journal ◽  
1996 ◽  
Vol 34 (11) ◽  
pp. 2337-2345 ◽  
Author(s):  
D. C. Lewellen ◽  
W. S. Lewellen
Keyword(s):  
Vortex Pair ◽  
Large Eddy Simulations ◽  
Large Eddy

scholarly journals Evaluation of large-eddy simulations forced with mesoscale model output for a multi-week period during a measurement campaign

2016 ◽  
Author(s):  
Rieke Heinze ◽  
Christopher Moseley ◽  
Lennart Nils Böske ◽  
Shravan Muppa ◽  
Vera Maurer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mesoscale Model ◽  
Large Eddy Simulations ◽  
Model Output ◽  
Synoptic Scale ◽  
High Definition ◽  
Shallow Cumulus ◽  
Large Eddy ◽  
Lidar Measurements ◽  
The Mean

Abstract. Large-eddy simulations (LES) of a multi-week period during the HD(CP)2 (High-Definition Clouds and Precipitation for advancing Climate Prediction) Observational Prototype Experiment (HOPE) conducted in Germany are evaluated with respect to mean boundary layer quantities and turbulence statistics. Two LES models are used in a semi-idealized setup through forcing with mescoscale model output to account for the synoptic-scale conditions. Evaluation is performed based on the HOPE observations. The mean boundary layer characteristics like the boundary layer depth are in a principal agreement with observations. Simulating shallow-cumulus layers in agreement with the measurements poses a challenge for both LES models. Variance profiles agree satisfactorily with lidar measurements. The results depend on how the forcing data stemming from mesoscale model output is constructed. The mean boundary layer characteristics become less sensitive if the averaging domain for the forcing is large enough to filter out mesoscale fluctuations.

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