TRACKING COHERENT STRUCTURES IN MASSIVELY-SEPARATED AND TURBULENT FLOWS

Coherent vortex structures are tracked in simulations of massively-separated and turbulent flows. Topological Lagrangian saddle points are found using intersections of the positive and negative finite-time Lyapunov exponent (FTLE) ridges, and these points are then followed in order to track individual coherent structure motion in both a complex interacting three-dimensional flow (turbulent channel) and during vortex formation (two-dimensional bluff body shedding). For a simulation of wall-bounded turbulence in a channel flow, tracking Lagrangian saddles shows that the average structure convection speed exhibits a similar trend as a previously published result based on velocity and pressure correlations, giving validity to the method. When this tracking method is applied in a study of a circular cylinder in cross-flow it shows that Lagrangian saddles rapidly accelerate away from the cylinder surface as the vortex sheds. This saddle behavior is compared with the time-resolved static pressure distribution on the circular cylinder, yielding locations on a cylinder surface where common sensors could detect this phenomenon, which is not available from force measurements or vortex circulation calculations. The current method of tracking coherent structures yields insight into the behavior of the coherent structures in both of the diverse flows presented, highlighting the breadth of its potential application.

[1]  Ding Wei,et al.  Study on the transports in transient flow over impulsively started circular cylinder using Lagrangian coherent structures , 2015, Commun. Nonlinear Sci. Numer. Simul..

[2]  J. Dabiri,et al.  Pinch-off of non-axisymmetric vortex rings , 2014, Journal of Fluid Mechanics.

[3]  George Haller,et al.  Experimental and numerical investigation of the kinematic theory of unsteady separation , 2008, Journal of Fluid Mechanics.

[4]  L. Graftieaux,et al.  Combining PIV, POD and vortex identification algorithms for the study of unsteady turbulent swirling flows , 2001 .

[5]  C. Williamson.  Vortex Dynamics in the Cylinder Wake , 1996 .

[6]  Jinhee Jeong,et al.  On the identification of a vortex , 1995, Journal of Fluid Mechanics.

[7]  E. Konstantinidis,et al.  Uncovering large-scale coherent structures in natural and forced turbulent wakes by combining PIV, POD, and FTLE , 2012 .

[8]  Kunihiko Taira,et al.  Detecting Vortex Formation and Shedding in Cylinder Wakes Using Lagrangian Coherent Structures , 2017 .

[9]  Melissa A. Green,et al.  Detection of Lagrangian coherent structures in three-dimensional turbulence , 2007, Journal of Fluid Mechanics.

[10]  G. Haller.  Distinguished material surfaces and coherent structures in three-dimensional fluid flows , 2001 .

[11]  Fazle Hussain,et al.  Propagation velocity of perturbations in turbulent channel flow , 1993 .

[12]  Alfredo Soldati,et al.  Experimental investigation on interactions among fluid and rod-like particles in a turbulent pipe jet by means of particle image velocimetry , 2014, Experiments in Fluids.

[13]  J. Vétel,et al.  Towards the detection of moving separation in unsteady flows , 2015, Journal of Fluid Mechanics.

[14]  H Nishimura,et al.  Aerodynamic characteristics of fluctuating forces on a circular cylinder , 2001 .

[15]  G. Haller,et al.  Coherent Lagrangian vortices: the black holes of turbulence , 2013, Journal of Fluid Mechanics.

[16]  Paul S Krueger,et al.  Sensitivity of Lagrangian coherent structure identification to flow field resolution and random errors. , 2010, Chaos.

[17]  M. Gharib,et al.  Role of the tip vortex in the force generation of low-aspect-ratio normal flat plates , 2007, Journal of Fluid Mechanics.

[18]  S. K. Robinson,et al.  Coherent Motions in the Turbulent Boundary Layer , 1991 .

[19]  G. Tadmor,et al.  Closed-loop Lagrangian separation control in a bluff body shear flow model , 2003 .

[20]  Frank Thiele,et al.  Obtaining phase averaged turbulence properties in the near wake of a circular cylinder at high Reynolds number using POD , 2007 .

[21]  Jerrold E. Marsden,et al.  Horseshoes in hurricanes , 2010 .

[22]  J. Gerrard.  The mechanics of the formation region of vortices behind bluff bodies , 1966, Journal of Fluid Mechanics.

[23]  Yannick Hoarau,et al.  Turbulence properties in the cylinder wake at high Reynolds numbers , 2006 .

[24]  Kamran Mohseni,et al.  A ridge tracking algorithm and error estimate for efficient computation of Lagrangian coherent structures. , 2010, Chaos.

[25]  Chih-Yung Wen,et al.  Experimental and numerical study of the separation angle for flow around a circular cylinder at low Reynolds number , 2004, Journal of Fluid Mechanics.

[26]  Yannick Hoarau,et al.  Near-Wake Turbulence Properties in the High Reynolds Number Incompressible Flow Around a Circular Cylinder Measured by Two- and Three-Component PIV , 2006 .

[27]  R. Martinuzzi,et al.  COHERENT VORTICAL AND STRAINING STRUCTURES IN THE FINITE WALL-MOUNTED SQUARE CYLINDER WAKE , 2012, Proceeding of Seventh International Symposium on Turbulence and Shear Flow Phenomena.

[28]  George Haller,et al.  Hyperbolic and elliptic transport barriers in three-dimensional unsteady flows , 2013, 1306.6497.

[29]  Gustavo Goni,et al.  Oceanic mesoscale eddies as revealed by Lagrangian coherent structures , 2008 .

[30]  Mike Campbell,et al.  Actual VIV Fatigue Response of Full Scale Drilling Risers: With and Without Suppression Devices , 2008 .

[31]  Carl M. Larsen,et al.  On fatigue damage accumulation from in-line and cross-flow vortex-induced vibrations on risers , 2006 .

[32]  Clarence W. Rowley,et al.  The unsteady three-dimensional wake produced by a trapezoidal pitching panel , 2011, Journal of Fluid Mechanics.

[33]  Matteo Astorino,et al.  Computational analysis of an aortic valve jet with Lagrangian coherent structures. , 2010, Chaos.

[34]  Jean-Luc Thiffeault,et al.  Detecting coherent structures using braids , 2011, 1106.2231.

[35]  Kenneth S. Breuer,et al.  Vortex formation and shedding from a cyber-physical pitching plate , 2016, Journal of Fluid Mechanics.

[36]  K. Mulleners,et al.  The onset of dynamic stall revisited , 2012 .

[37]  G. Haller.  Lagrangian coherent structures from approximate velocity data , 2002 .

[38]  R. Adrian.  Structure of Turbulent Boundary Layers , 2013 .

[39]  M. S. Chong,et al.  A general classification of three-dimensional flow fields , 1990 .

[40]  Osamu Inoue,et al.  Sound generation by a two-dimensional circular cylinder in a uniform flow , 2002, Journal of Fluid Mechanics.

[41]  Michael R Allshouse,et al.  Lagrangian based methods for coherent structure detection. , 2015, Chaos.

[42]  G. Haller.  A variational theory of hyperbolic Lagrangian Coherent Structures , 2010 .

[43]  P. Moin,et al.  Eddies, streams, and convergence zones in turbulent flows , 1988 .

[44]  John O Dabiri,et al.  A Lagrangian approach to identifying vortex pinch-off. , 2009, Chaos.

[45]  Kwitae Chong,et al.  Fluid transport and coherent structures of translating and flapping wings. , 2010, Chaos.

[46]  P. Moin,et al.  Unstructured Large Eddy Simulation for Prediction of Noise Issued from Turbulent Jets in Various Configurations , 2011 .

[47]  G. Haller,et al.  Geodesic theory of transport barriers in two-dimensional flows , 2012 .

[48]  J. Gerrard,et al.  Vorticity measurements in the near wake of a circular cylinder at low Reynolds numbers , 1993, Journal of Fluid Mechanics.

[49]  Melissa A. Green,et al.  Detection and tracking of vortex phenomena using Lagrangian coherent structures , 2015 .

[50]  André Garon,et al.  On the flow separation in the wake of a fixed and a rotating cylinder. , 2015, Chaos.

[51]  P. Moin,et al.  Turbulence statistics in fully developed channel flow at low Reynolds number , 1987, Journal of Fluid Mechanics.