Brian F. Farrell
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View article: Fluctuation covariance-based study of roll-streak dynamics in Poiseuille flow turbulence
Fluctuation covariance-based study of roll-streak dynamics in Poiseuille flow turbulence Open
Although the roll-streak (R-S) is fundamentally involved in the dynamics of wall turbulence, the physical mechanism responsible for its formation and maintenance remains controversial. In this work we investigate the dynamics maintaining t…
View article: Statistical state dynamics-based study of the stability of the mean statistical state of wall-bounded turbulence
Statistical state dynamics-based study of the stability of the mean statistical state of wall-bounded turbulence Open
In wall turbulence, the time-mean flow is returned to after almost any disturbance, which indicates that it is a stable statistical feature underlying the disorder of turbulence. However, the stability of this statistical feature can not b…
View article: Fluctuation covariance-based study of roll-streak dynamics in Poiseuille flow turbulence
Fluctuation covariance-based study of roll-streak dynamics in Poiseuille flow turbulence Open
Although the roll-streak (R-S) is fundamentally involved in the dynamics of wall-turbulence, the physical mechanism responsible for its formation and maintenance remains controversial. In this work we investigate the dynamics maintaining t…
View article: POD-based study of turbulent plane Poiseuille flow: comparing structure and dynamics between quasi-linear simulations and DNS
POD-based study of turbulent plane Poiseuille flow: comparing structure and dynamics between quasi-linear simulations and DNS Open
Turbulence in the restricted nonlinear (RNL) dynamics is analysed and compared with direct numerical simulations (DNS) of Poiseuille turbulence at Reynolds number $R=1650$ . The structures are obtained by proper orthogonal decomposition (P…
View article: Statistical state dynamics-based study of the stability of the mean statistical state of wall-bounded turbulence
Statistical state dynamics-based study of the stability of the mean statistical state of wall-bounded turbulence Open
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 associated statistical state dynamics (SSD) closed at seco…
View article: Migratory beekeeping facilitates genetic admixture in populations of the honeybee parasite Varroa destructor
Migratory beekeeping facilitates genetic admixture in populations of the honeybee parasite Varroa destructor Open
Understanding the rapid evolution of agricultural pests can inform mitigation efforts and provide comprehensive models for natural systems and examples for the consequences of anthropogenic global change. It is suspected that the practice …
View article: POD-based study of structure and dynamics in turbulent plane Poiseuille flow: comparing quasi-linear simulations to DNS
POD-based study of structure and dynamics in turbulent plane Poiseuille flow: comparing quasi-linear simulations to DNS Open
Turbulence structure in the quasi-linear restricted nonlinear (RNL) model is analyzed and compared with DNS of turbulent Poiseuille flow at Reynolds number R=1650. The turbulence structure is obtained by POD analysis of the two components …
View article: POD-based study of turbulent plane Poiseuille flow: comparing structure and dynamics between quasi-linear simulations and DNS
POD-based study of turbulent plane Poiseuille flow: comparing structure and dynamics between quasi-linear simulations and DNS Open
Turbulence in the restricted nonlinear (RNL) dynamics is analyzed and compared with DNS of Poiseuille turbulence at $R=1650$. The structures are obtained by POD analysis of the two components of the flow partition used in RNL dynamics: the…
View article: Vertically Sheared Horizontal Flow-Forming Instability in Stratified Turbulence: Analytical Linear Stability Analysis of Statistical State Dynamics Equilibria
Vertically Sheared Horizontal Flow-Forming Instability in Stratified Turbulence: Analytical Linear Stability Analysis of Statistical State Dynamics Equilibria Open
Vertically banded zonal jets are frequently observed in weakly or nonrotating stratified turbulence, with the quasi-biennial oscillation in the equatorial stratosphere and the ocean’s equatorial deep jets being two examples. Explaining the…
View article: Statistical state dynamics of vertically sheared horizontal flows in two-dimensional stratified turbulence
Statistical state dynamics of vertically sheared horizontal flows in two-dimensional stratified turbulence Open
Simulations of strongly stratified turbulence often exhibit coherent large-scale structures called vertically sheared horizontal flows (VSHFs). VSHFs emerge in both two-dimensional (2D) and three-dimensional (3D) stratified turbulence with…
View article: Statistical State Dynamics Based Study of the Role of Nonlinearity in the Maintenance of Turbulence in Couette Flow
Statistical State Dynamics Based Study of the Role of Nonlinearity in the Maintenance of Turbulence in Couette Flow Open
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 to play an essential role. The goal of this study is to be…
View article: Parametric mechanism maintaining Couette flow turbulence verified in DNS\n implies novel control strategies
Parametric mechanism maintaining Couette flow turbulence verified in DNS\n implies novel control strategies Open
The no-slip boundary condition results in a velocity shear forming in fluid\nflow near a solid surface. This shear flow supports the turbulence\ncharacteristic of fluid flow near boundaries at Reynolds numbers above\n$\\approx1000$ by maki…
View article: Parametric mechanism maintaining Couette flow turbulence verified in DNS implies novel control strategies
Parametric mechanism maintaining Couette flow turbulence verified in DNS implies novel control strategies Open
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 boundaries at Reynolds numbers above $\approx1000$ by making a…
View article: Statistical state dynamics based theory for the formation and equilibration of Saturn's north polar jet
Statistical state dynamics based theory for the formation and equilibration of Saturn's north polar jet Open
Coherent jets with most of the kinetic energy of the flow are common in\natmospheric turbulence. In the gaseous planets these jets are maintained by\nincoherent turbulence excited by small-scale convection. Large-scale coherent\nwaves are …
View article: Instability of the roll-streak structure induced by background turbulence in pretransitional Couette flow
Instability of the roll-streak structure induced by background turbulence in pretransitional Couette flow Open
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 an instability, the large transient growth of the roll/str…
View article: A Theory Based on Statistical State Dynamics for the Formation of Jets and Associated Density Layers in Stratified Turbulence
A Theory Based on Statistical State Dynamics for the Formation of Jets and Associated Density Layers in Stratified Turbulence Open
Stratified turbulence is characterized by strong anisotropy and a red energy spectrum. Moreover, in many cases the energetic large scales consist of coherent horizontal structures such as vertically sheared horizontal flows, also called st…
View article: Statistical State Dynamics of Vertically Sheared Horizontal Flows in\n Two-Dimensional Stratified Turbulence
Statistical State Dynamics of Vertically Sheared Horizontal Flows in\n Two-Dimensional Stratified Turbulence Open
Simulations of strongly stratified turbulence often exhibit coherent\nlarge-scale structures called vertically sheared horizontal flows (VSHFs).\nVSHFs emerge in both two-dimensional (2D) and three-dimensional (3D) stratified\nturbulence w…
View article: Instability of the roll-streak structure induced by background turbulence in pre-transitional Couette flow
Instability of the roll-streak structure induced by background turbulence in pre-transitional Couette flow Open
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 an instability, the large transient growth of the roll/str…
View article: Structure and mechanism in a second-order statistical state dynamics model of self-sustaining turbulence in plane Couette flow
Structure and mechanism in a second-order statistical state dynamics model of self-sustaining turbulence in plane Couette flow Open
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 form are referred to as S3T models and self-sustain turbule…
View article: Investigation of Thermo-Magnetic Processing in Application to Heavy Duty Truck Suspension Components
Investigation of Thermo-Magnetic Processing in Application to Heavy Duty Truck Suspension Components Open
Thermomagnetic processing (TMP) was examined as a methodology for increasing transformation rate during heat treatment in steel tubes. Two potential benefits were investigated, reduced energy consumption and improved mechanical properties.…
View article: A POD-based analysis of turbulence in the reduced nonlinear dynamics system
A POD-based analysis of turbulence in the reduced nonlinear dynamics system Open
The structure of turbulence in a reduced model of turbulence (RNL) is analyzed by means of a Proper Orthogonal Decomposition (POD modes). POD analysis was carried out on two different components of the flow, the roll/streak and the perturb…
View article: Investigation of Thermo-Magnetic Processing in Application to Heavy Duty Truck Suspension Components - Final CRADA Report
Investigation of Thermo-Magnetic Processing in Application to Heavy Duty Truck Suspension Components - Final CRADA Report Open
Thermomagnetic processing (TMP) was examined as a methodology for increasing transformation rate during heat treatment in steel tubes. Two potential benefits were investigated, reduced energy consumption and improved mechanical properties.…
View article: Structure and mechanism of turbulence under dynamical restriction in plane Poiseuille flow
Structure and mechanism of turbulence under dynamical restriction in plane Poiseuille flow Open
The perspective of statistical state dynamics (SSD) has been applied to the study of mechanisms underlying turbulence in various physical systems. An example application of SSD is that of the second order closure, referred to as stochastic…
View article: Statistical state dynamics of jet/wave coexistence in beta-plane turbulence
Statistical state dynamics of jet/wave coexistence in beta-plane turbulence Open
Jets are commonly observed to coexist in the turbulence of planetary atmospheres with planetary scale waves and embedded vortices. These large-scale coherent structures arise and are maintained in the turbu-lence on time scales long compar…