123 citations · 700 across the 31 of their papers we have counts for
21 papers · 1 filter
Statistical State Dynamics Eigenmodes and Equilibria support Couette Turbulence
Brian F. Farrell, Petros J. Ioannou
Wide-channel Couette (WCC) turbulence consists primarily of quasi-steady roll-streak structures (RSS) maintained by a self-sustaining process (SSP), yet the Navier-Stokes equations…
Statistical state dynamics modes and equilibria underlie the structure and mechanism of wide channel Couette turbulence
Brian F. Farrell, Petros J. Ioannou
Wide channel Couette (WCC) turbulence is striking in being dominated by a large-scale spanwise periodic structure composed of streamwise streaks and associated roll superstructures…
Statistical state dynamics-based study of the stability of the mean statistical state of wall-bounded turbulence
Brian F. Farrell, Petros J. Ioannou
Turbulence in wall-bounded flows is characterized by stable statistics. Although, in many turbulent systems, this stable statistical state corresponds to a stable fixed point of an…
Investigating nonlinearity in wall turbulence: regenerative versus parametric mechanisms
B. F. Farrell, E. Kim, H. J. Bae +2
Both linear growth processes associated with non-normality of the mean flow and nonlinear interaction transferring energy among fluctuations contribute to maintaining turbulence. H…
Mechanism of Roll-Streak Structure Formation and Maintenance in Turbulent Shear Flow
B. F. Farrell, P. J. Ioannou, M. -A. Nikolaidis
In wall-bounded shear flow the primary coherent structure is the streamwise roll and streak (R-S). Absent of an associated instability the R-S has been ascribed to non-normality me…
POD-based study of turbulent plane Poiseuille flow: comparing structure and dynamics between quasi-linear simulations and DNS
Marios-Andreas Nikolaidis, Petros J. Ioannou, Brian F. Farrell +1
Turbulence in the restricted nonlinear (RNL) dynamics is analyzed and compared with DNS of Poiseuille turbulence at . The structures are obtained by POD analysis of the two…
Synchronization of Low Reynolds Number Plane Couette Turbulence
Marios-Andreas Nikolaidis, Petros J. Ioannou
We demonstrate that a separation of the velocity field in large and small scales according to a streamwise Fourier decomposition identifies subspaces with stable Lyapunov exponents…
Parametric mechanism maintaining Couette flow turbulence verified in DNS implies novel control strategies
Brian F. Farrell, Petros J. Ioannou, Marios-Andreas Nikolaidis
The no-slip boundary condition results in a velocity shear forming in fluid flow near a solid surface. This shear flow supports the turbulence characteristic of fluid flow near bou…
Statistical State Dynamics Based Study of the Role of Nonlinearity in the Maintenance of Turbulence in Couette Flow
Brian F. Farrell, Petros J. Ioannou, Marios-Andreas Nikolaidis
While linear non-normality underlies the mechanism of energy transfer from the externally driven flow to the perturbation field that sustains turbulence, nonlinearity is also known…
The mechanism by which nonlinearity sustains turbulence in plane Couette flow
Marios-Andreas Nikolaidis, Brian F. Farrell, Petros J. Ioannou
Turbulence in wall-bounded shear flow results from a synergistic interaction between linear non-normality and nonlinearity in which non-normal growth of a subset of perturbations c…
A statistical state dynamics approach to wall-turbulence
Brian F. Farrell, Dennice F. Gayme, Petros J. Ioannou
This paper reviews results from the study of wall-bounded turbulent flows using statistical state dynamics (SSD) that demonstrate the benefits of adopting this perspective for unde…
Statistical state dynamics-based analysis of the physical mechanisms sustaining and regulating turbulence in Couette flow
Brian F. Farrell, Petros J. Ioannou
This paper describes a study of the self-sustaining process in wall-turbulence based on a second order statistical state dynamics (SSD) model of Couette flow. SSD models with this…
Instability of the roll/streak structure induced by free-stream turbulence in pre-transitional Couette flow
Brian F. Farrell, Petros J. Ioannou, Marios-Andreas Nikolaidis
Although the roll/streak structure is ubiquitous in pre-transitional wall-bounded shear flow, this structure is linearly stable if the idealization of laminar flow is made. Lacking…
A statistical state dynamics-based study of the structure and mechanism of large-scale motions in plane Poiseuille flow
Brian F. Farrell, Petros J. Ioannou, Javier Jiménez +3
The perspective of statistical state dynamics (SSD) has recently been applied to the study of mechanisms underlying turbulence in various physical systems. An example implementatio…
A minimal model of self-sustaining turbulence
Vaughan Thomas, Brian F. Farrell, Petros J. Ioannou +1
In this work we examine the turbulence maintained in a Restricted Nonlinear (RNL) model of plane Couette flow. This model is a computationally efficient approximation of the second…
Statistical State Dynamics: a new perspective on turbulence in shear flow
Brian F. Farrell, Petros J. Ioannou
Traditionally, single realizations of the turbulent state have been the object of study in shear flow turbulence. When a statistical quantity was needed it was obtained from a spat…
Self-sustaining turbulence in a restricted nonlinear model of plane Couette flow
Vaughan L. Thomas, Binh K. Lieu, Mihailo R. Jovanović +3
This paper demonstrates the maintenance of self-sustaining turbulence in a restricted nonlinear (RNL) model of plane Couette flow. The RNL system is derived directly from the Navie…
Turbulence in the highly restricted dynamics of a closure at second order: comparison with DNS
Navid C. Constantinou, Adrian Lozano-Durán, Marios-Andreas Nikolaidis +3
S3T (Stochastic Structural Stability Theory) employs a closure at second order to obtain the dynamics of the statistical mean turbulent state. When S3T is implemented as a coupled…
Emergence and equilibration of jets in beta-plane turbulence: applications of Stochastic Structural Stability Theory
Navid C. Constantinou, Brian F. Farrell, Petros J. Ioannou
Stochastic Structural Stability Theory (S3T) provides analytical methods for understanding the emergence and equilibration of jets from the turbulence in planetary atmospheres base…
Stochastic Structural Stability Theory applied to roll/streak formation in boundary layer shear flow
Brian F. Farrell, Petros J. Ioannou
Stochastic Structural Stability Theory (SSST) provides an autonomous, deterministic, nonlinear dynamical system for evolving the statistical mean state of a turbulent system. In th…
Optimal excitation of two dimensional Holmboe instabilities
Navid C. Constantinou, Petros J. Ioannou
Highly stratified shear layers are rendered unstable even at high stratifications by Holmboe instabilities when the density stratification is concentrated in a small region of the…