Some Factors Influencing the Vortical Flow Structures on Delta Wings

2008 ◽  
Author(s):  
Emre Gürdamar ◽  
Yüksel Ortakaya ◽  
Bülent Korkem ◽  
Serpil Kaya
Keyword(s):  
Vortical Flow ◽  
Flow Structures ◽  
Delta Wings ◽  
Factors Influencing

scholarly journals Vortical Flow Structures Induced by Red Blood Cells in Capillaries

2021 ◽  
Author(s):  
François Yaya ◽  
Johannes Römer ◽  
Achim Guckenberger ◽  
Thomas John ◽  
Stephan Gekle ◽  
...  
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Vortical Flow ◽  
Flow Structures

Flow structures and particle deposition patterns in double-bifurcation airway models. Part 2. Aerosol transport and deposition

2001 ◽  
Vol 435 ◽  
pp. 55-80 ◽  
Author(s):  
J. K. COMER ◽  
C. KLEINSTREUER ◽  
C. S. KIM
Keyword(s):  
Particle Deposition ◽  
Air Flow ◽  
Reynolds Numbers ◽  
Companion Paper ◽  
Stokes Number ◽  
Vortical Flow ◽  
Flow Structures ◽  
Particle Distributions ◽  
Deposition Patterns ◽  
Inlet Conditions

The flow theory and air flow structures in symmetric double-bifurcation airway models assuming steady laminar, incompressible flow, unaffected by the presence of aerosols, has been described in a companion paper (Part 1). The validated computer simulation results showed highly vortical flow fields, especially around the second bifurcations, indicating potentially complex particle distributions and deposition patterns. In this paper (Part 2), assuming spherical non-interacting aerosols that stick to the wall when touching the surface, the history of depositing particles is described. Specifically, the finite-volume code CFX (AEA Technology) with user-enhanced FORTRAN programs were validated with experimental data of particle deposition efficiencies as a function of the Stokes number for planar single and double bifurcations. The resulting deposition patterns, particle distributions, trajectories and time evolution were analysed in the light of the air flow structures for relatively low (ReD1 = 500) and high (ReD1 = 2000) Reynolds numbers and representative Stokes numbers, i.e. StD1 = 0.04 and StD1 = 0.12. Particle deposition patterns and surface concentrations are largely a function of the local Stokes number, but they also depend on the fluid–particle inlet conditions as well as airway geometry factors. While particles introduced at low inlet Reynolds numbers (e.g. ReD1 = 500) follow the axial air flow, secondary and vortical flows become important at higher Reynolds numbers, causing the formation of particle-free zones near the tube centres and subsequently elevated particle concentrations near the walls. Sharp or mildly rounded carinal ridges have little effect on the deposition efficiencies but may influence local deposition patterns. In contrast, more drastic geometric changes to the basic double-bifurcation model, e.g. the 90°-non-planar configuration, alter both the aerosol wall distributions and surface concentrations considerably.

Large Eddy Simulation of the Flow Around a Diffuser-Equipped Bluff Body in Ground Effect

2011 ◽  
Author(s):  
Lara Schembri Puglisevich ◽  
Gary Page
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Vortex Formation ◽  
Ground Effect ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Flow Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features

Unsteady Large Eddy Simulation (LES) is carried out for the flow around a bluff body equipped with an underbody rear diffuser in close proximity to the ground, representing an automotive diffuser. The goal is to demonstrate the ability of LES to model underbody vortical flow features at experimental Reynolds numbers (1.01 × 106 based on model height and incoming velocity). The scope of the time-dependent simulations is not to improve on Reynolds-Averaged Navier Stokes (RANS), but to give further insight into vortex formation and progression, allowing better understanding of the flow, hence allowing more control. Vortical flow structures in the diffuser region, along the sides and top surface of the bluff body are successfully modelled. Differences between instantaneous and time-averaged flow structures are presented and explained. Comparisons to pressure measurements from wind tunnel experiments on an identical bluff body model shows a good level of agreement.

On the vortex dynamics of shear-driven deep cavity flows with asymmetrical walls

2016 ◽  
Vol 94 (12) ◽  
pp. 1344-1352 ◽  
Author(s):  
D. Cornu ◽  
L. Keirsbulck ◽  
F. Kerhervé ◽  
F. Aloui ◽  
M. Lippert
Keyword(s):  
Physical Nature ◽  
Wall Pressure ◽  
Vortical Flow ◽  
Flow Structures ◽  
Cavity Flows ◽  
Convective Structures ◽  
Deep Cavity ◽  
Image Velocimetry ◽  
Flow Features ◽  
Deep Cavities

The influence of the length-to-depth aspect ratio and of wall asymmetry on the main vortical flow structures evolving in rectangular two-dimensional deep cavities is studied experimentally using wall-pressure and particle image velocimetry (PIV) measurements. Wall-pressure and cavity flow statistics have been analyzed and shown that the flow features are strongly affected especially by the asymmetry. An emphasis is given concerning the behavior of the shear layer oscillations that are compared to the analytical deep-cavity model prediction proposed by P.J.W. Block (NASA Tech. Note. 1976). The results show good agreement with Block’s model if the value of the convection velocity is properly adjusted. Stochastic estimation of the cavity flows demonstrates that convective structures are involved downstream of the cavity along the wall and highlights the physical nature of the pressure-producing flow structures.

Prediction of tunnel wall upwash for delta wings including vortex breakdown effects

1999 ◽  
Vol 103 (1021) ◽  
pp. 139-142 ◽  
Author(s):  
L. W. Traub
Keyword(s):  
Vortex Breakdown ◽  
Side Wall ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Wall Effects ◽  
Integral Expression ◽  
Image System ◽  
Tunnel Wall ◽  
Delta Wings ◽  
Side Walls

AbstractAn incompressible method is presented to predict the upwash corrections associated with vortical flow as a result of wind-tunnel side wall effects. An image system is used to simulate the tunnel side walls which are assumed to be solid. An integral expression is formulated, representing the average upwash induced over the wing by the image system. Wall effects may be determined for flows with and without vortex breakdown. Comparisons of the results with upwash predictions from a Navier-Stokes study show close accord. The upwash expression also displayed the ability to successfully predict corrections for flows involving vortex breakdown.

scholarly journals Examining the Kinematic Structures within which Lightning Flashes are Initiated using a Cloud-Resolving Model

2021 ◽  
Author(s):  
Vicente Salinas ◽  
Eric C. Bruning ◽  
Edward R. Mansell
Keyword(s):  
Electric Fields ◽  
Careful Consideration ◽  
Vortical Flow ◽  
Flow Structures ◽  
Lightning Flash ◽  
Turbulent Eddies ◽  
Supercell Storms ◽  
Flow Features ◽  
Cloud Resolving Model ◽  
Eddy Flow

Abstract Lightning is frequently initiated within the convective regions of thunderstorms, and so flash rates tend to follow trends in updraft speed and volume. It has been suggested that lightning production is linked to the turbulent flow generated by updrafts as turbulent eddies organize charged hydrometeors into complex charge structures. These complex charge structures consist of local regions of increased charge magnitudes between which flash initiating electric fields may be generated. How turbulent kinematics influences lightning production, however, remains unclear. In this study, lightning flashes produced in a multi-cell and two supercell storms simulated using The Collaborative Model for Multiscale Atmospheric Simulation (COMMAS) were examined to identify the kinematic flow structures within which they occurred. By relating the structures of updrafts to thermals, initiated lightning were expected to be located where the rate of strain and rotational flow are equal, or between updraft and eddy flow features. Results showed that the average lightning flash is initiated in kinematic flow structures dominated by vortical flow patterns, similar to those of thermals, and the structures’ kinematics are characterized by horizontal vorticity and vertical shearing. These kinematic features were common across all cases and demonstrated that where flash initiating electric fields are generated is along the periphery of updrafts where turbulent eddies are produced. Careful consideration of flow structures near initiated flashes is consistent with those of thermals rising through a storm.

Manipulating Tumble and Swirl Flows in Cylinder of a Motored Four-Valve Engine by Inlet Deflection Valve

2008 ◽  
Vol 24 (4) ◽  
pp. 333-345 ◽  
Author(s):  
R. F. Huang ◽  
J. H. Yu ◽  
C.-N. Yeh
Keyword(s):  
Turbulence Intensity ◽  
Vortical Flow ◽  
Flow Structures ◽  
Inlet Stream ◽  
Air Stream ◽  
Engine Cylinder ◽  
Swirl Flows ◽  
Measured Time ◽  
Valve Engine ◽  
Cylinder Flow

AbstractEffects of the inlet-stream deflection on the temporal and spatial evolution processes of the in-cylinder flow structures (tumble/swirl) and turbulence intensities in the symmetry and diametral planes of a motored four-valve, four-stroke engine are diagnosed by using a particle image velocimeter. The inception, establishment, and evolution of the tumbling/swirling vortical flow structures during the intake and compression strokes in the engine cylinder with/without inlet-stream deflection are depicted and compared. Quantitative strengths of the rotating vortical flow motions are presented by dimensionless parameters (tumble and swirl ratios) which can represent the mean angular velocity of the vortices in the target plane. The turbulence intensity is calculated by using the measured time-varying velocity data. The results show that by deflecting the inlet air-stream the tumble and swirl ratios of the in-cylinder flow are appreciably increased by about 0.1 and the turbulence intensity is increased by about 5 ∼ 10%.

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