The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform

Arne V. Johansson - One of the best experts on this subject based on the ideXlab platform.

  • recurrent bursts via Linear Processes in turbulent environments
    Physical Review Letters, 2014
    Co-Authors: Geert Brethouwer, Yohann Duguet, P. Schlatter, Dan S Henningson, Arne V. Johansson
    Abstract:

    Large-scale instabilities occurring in the presence of small-scale turbulent fluctuations are frequently observed in geophysical or astrophysical contexts but are difficult to reproduce in the laboratory. Using extensive numerical simulations, we report here on intense recurrent bursts of turbulence in plane Poiseuille flow rotating about a spanwise axis. A simple model based on the Linear instability of the mean flow can predict the structure and time scale of the nearly periodic and self-sustained burst cycles. Poiseuille flow is suggested as a prototype for future studies of low-dimensional dynamics embedded in strongly turbulent environments.

  • Recurrent bursts via Linear Processes in turbulent environments
    Physical Review Letters, 2014
    Co-Authors: Geert Brethouwer, Yohann Duguet, P. Schlatter, Dan S Henningson, Arne V. Johansson
    Abstract:

    Large-scale instabilities occurring in the presence of small-scale turbulent fluctuations are frequently observed in geophysical or astrophysical contexts but are difficult to reproduce in the laboratory. Using extensive numerical simulations, we report here on intense recurrent bursts of turbulence in plane Poiseuille flow rotating about a spanwise axis. A simple model based on the Linear instability of the mean flow can predict the structure and time scale of the nearly periodic and self-sustained burst cycles. Poiseuille flow is suggested as a prototype for future studies of low-dimensional dynamics embedded in strongly turbulent environments. Environments with strong fluctuations frequently display regular or chaotic large-scale dynamics. Well-known astro-physical examples are the reversals of large-scale planetary magnetic fields, which are chaotic for Earth but time periodic for the Sun [1]. Other geophysical and astrophysical man-ifestations of large-scale instabilities include climate cycles on Earth [2] and solar flares [3]. Random reversals of a large-scale circulation are also found in Rayleigh-Bénard convection [4], and in von Kármán [5] and laboratory fluid dynamo experiments [6]. Recurrent large-scale oscillations or bursts like in toka-mak plasmas [7] and accretion disks [8] are important manifestations of large-scale instabilities in the presence of (strong) fluctuations. Because of their complexity and the very different scales involved, bursting phenomena are frequently investigated in the laboratory using simplified flow prototypes that capture the essential features of these large-scale instabilities. Such prototypes are usually based on simple geometries while the dominant mechanisms under study are preserved, e.g., the interaction between shear and rotation, convection or Lorentz forces. A bifurcation from full turbulence to an intermittently bursting turbulent regime was recently observed in large-gap Taylor-Couette flows with counterrotating cylinders [9]. The bifurcation was found to coincide with the optimal torque parameters. A striking feature of the large-scale instabilities in the aforementioned systems is their apparent low dimensionality, despite the fact that they happen in environments with intrinsic strong (usually turbulent) fluctuations. Nevertheless, the fundamen-tal cause of these large-scale dynamics is not always under-stood and it is often arduous to derive elementary models from first principles. In this Letter, we describe the occurrence of violent time-periodic bursts in an as yet unexplored parameter range of turbulent plane rotating Poiseuille flow (RPF), seen as a canonical example of interaction between shear and rota-tion. The flow develops a large-scale Linear instability under the influence of rotation even though it is strongly turbulent. This Linear instability is followed by a distinct sequence of Processes leading to a self-sustaining cycle of recurrent bursts of turbulence. We demonstrate that the Linear instability of the mean flow captures the essential features of the recurrent bursts. We thus argue that RPF is a relevant example of low-dimensional dynamics embedded in a high-dimensional system with strong fluctuations, and can serve as a new prototype for future studies of large-scale dynamics. The RPF case considered here is a pressure-driven plane channel flow between two smooth parallel flat walls subject to a global rotation about the spanwise axis orthogonal to the mean flow and parallel to the walls; see Fig. 1 for a schematic. The velocity field u is governed by the incom-pressible Navier-Stokes equations in the rotating frame

Geert Brethouwer - One of the best experts on this subject based on the ideXlab platform.

  • recurrent bursts via Linear Processes in turbulent environments
    Physical Review Letters, 2014
    Co-Authors: Geert Brethouwer, Yohann Duguet, P. Schlatter, Dan S Henningson, Arne V. Johansson
    Abstract:

    Large-scale instabilities occurring in the presence of small-scale turbulent fluctuations are frequently observed in geophysical or astrophysical contexts but are difficult to reproduce in the laboratory. Using extensive numerical simulations, we report here on intense recurrent bursts of turbulence in plane Poiseuille flow rotating about a spanwise axis. A simple model based on the Linear instability of the mean flow can predict the structure and time scale of the nearly periodic and self-sustained burst cycles. Poiseuille flow is suggested as a prototype for future studies of low-dimensional dynamics embedded in strongly turbulent environments.

  • Recurrent bursts via Linear Processes in turbulent environments
    Physical Review Letters, 2014
    Co-Authors: Geert Brethouwer, Yohann Duguet, P. Schlatter, Dan S Henningson, Arne V. Johansson
    Abstract:

    Large-scale instabilities occurring in the presence of small-scale turbulent fluctuations are frequently observed in geophysical or astrophysical contexts but are difficult to reproduce in the laboratory. Using extensive numerical simulations, we report here on intense recurrent bursts of turbulence in plane Poiseuille flow rotating about a spanwise axis. A simple model based on the Linear instability of the mean flow can predict the structure and time scale of the nearly periodic and self-sustained burst cycles. Poiseuille flow is suggested as a prototype for future studies of low-dimensional dynamics embedded in strongly turbulent environments. Environments with strong fluctuations frequently display regular or chaotic large-scale dynamics. Well-known astro-physical examples are the reversals of large-scale planetary magnetic fields, which are chaotic for Earth but time periodic for the Sun [1]. Other geophysical and astrophysical man-ifestations of large-scale instabilities include climate cycles on Earth [2] and solar flares [3]. Random reversals of a large-scale circulation are also found in Rayleigh-Bénard convection [4], and in von Kármán [5] and laboratory fluid dynamo experiments [6]. Recurrent large-scale oscillations or bursts like in toka-mak plasmas [7] and accretion disks [8] are important manifestations of large-scale instabilities in the presence of (strong) fluctuations. Because of their complexity and the very different scales involved, bursting phenomena are frequently investigated in the laboratory using simplified flow prototypes that capture the essential features of these large-scale instabilities. Such prototypes are usually based on simple geometries while the dominant mechanisms under study are preserved, e.g., the interaction between shear and rotation, convection or Lorentz forces. A bifurcation from full turbulence to an intermittently bursting turbulent regime was recently observed in large-gap Taylor-Couette flows with counterrotating cylinders [9]. The bifurcation was found to coincide with the optimal torque parameters. A striking feature of the large-scale instabilities in the aforementioned systems is their apparent low dimensionality, despite the fact that they happen in environments with intrinsic strong (usually turbulent) fluctuations. Nevertheless, the fundamen-tal cause of these large-scale dynamics is not always under-stood and it is often arduous to derive elementary models from first principles. In this Letter, we describe the occurrence of violent time-periodic bursts in an as yet unexplored parameter range of turbulent plane rotating Poiseuille flow (RPF), seen as a canonical example of interaction between shear and rota-tion. The flow develops a large-scale Linear instability under the influence of rotation even though it is strongly turbulent. This Linear instability is followed by a distinct sequence of Processes leading to a self-sustaining cycle of recurrent bursts of turbulence. We demonstrate that the Linear instability of the mean flow captures the essential features of the recurrent bursts. We thus argue that RPF is a relevant example of low-dimensional dynamics embedded in a high-dimensional system with strong fluctuations, and can serve as a new prototype for future studies of large-scale dynamics. The RPF case considered here is a pressure-driven plane channel flow between two smooth parallel flat walls subject to a global rotation about the spanwise axis orthogonal to the mean flow and parallel to the walls; see Fig. 1 for a schematic. The velocity field u is governed by the incom-pressible Navier-Stokes equations in the rotating frame

Shankar Narasimhan - One of the best experts on this subject based on the ideXlab platform.

  • sensor network design of Linear Processes using genetic algorithms
    Computers & Chemical Engineering, 1998
    Co-Authors: Shankar Narasimhan
    Abstract:

    A generalized sensor network design algorithm for finding the optimal placement of sensors in a Linear mass flow process has been developed and implemented. The algorithm developed in this work is based on a combination of concepts drawn from graph theory and genetic algorithms. The sensor network is designed to optimize a single criterion of cost, reliability or estimation accuracy, using a minimum number of sensors. Application to a steam-metering network of a methanol plant demonstrates the versatility of this method.

  • sensor network design for maximizing reliability of Linear Processes
    Aiche Journal, 1993
    Co-Authors: Shankar Narasimhan
    Abstract:

    The problem of selecting the variables to be measured in order to maximize process reliability was tackled in our previous articles (Ali and Narasimhan, 1993, 1995). In this article, this approach is extended to the optimal design of sensor networks for biLinear Processes. Diverse Processes, such as a mineral beneficiation plant, a separation system of a synthetic juice plant, and a crude preheat train of a refinery are used to illustrate the utility of this approach.

Yohann Duguet - One of the best experts on this subject based on the ideXlab platform.

  • recurrent bursts via Linear Processes in turbulent environments
    Physical Review Letters, 2014
    Co-Authors: Geert Brethouwer, Yohann Duguet, P. Schlatter, Dan S Henningson, Arne V. Johansson
    Abstract:

    Large-scale instabilities occurring in the presence of small-scale turbulent fluctuations are frequently observed in geophysical or astrophysical contexts but are difficult to reproduce in the laboratory. Using extensive numerical simulations, we report here on intense recurrent bursts of turbulence in plane Poiseuille flow rotating about a spanwise axis. A simple model based on the Linear instability of the mean flow can predict the structure and time scale of the nearly periodic and self-sustained burst cycles. Poiseuille flow is suggested as a prototype for future studies of low-dimensional dynamics embedded in strongly turbulent environments.

  • Recurrent bursts via Linear Processes in turbulent environments
    Physical Review Letters, 2014
    Co-Authors: Geert Brethouwer, Yohann Duguet, P. Schlatter, Dan S Henningson, Arne V. Johansson
    Abstract:

    Large-scale instabilities occurring in the presence of small-scale turbulent fluctuations are frequently observed in geophysical or astrophysical contexts but are difficult to reproduce in the laboratory. Using extensive numerical simulations, we report here on intense recurrent bursts of turbulence in plane Poiseuille flow rotating about a spanwise axis. A simple model based on the Linear instability of the mean flow can predict the structure and time scale of the nearly periodic and self-sustained burst cycles. Poiseuille flow is suggested as a prototype for future studies of low-dimensional dynamics embedded in strongly turbulent environments. Environments with strong fluctuations frequently display regular or chaotic large-scale dynamics. Well-known astro-physical examples are the reversals of large-scale planetary magnetic fields, which are chaotic for Earth but time periodic for the Sun [1]. Other geophysical and astrophysical man-ifestations of large-scale instabilities include climate cycles on Earth [2] and solar flares [3]. Random reversals of a large-scale circulation are also found in Rayleigh-Bénard convection [4], and in von Kármán [5] and laboratory fluid dynamo experiments [6]. Recurrent large-scale oscillations or bursts like in toka-mak plasmas [7] and accretion disks [8] are important manifestations of large-scale instabilities in the presence of (strong) fluctuations. Because of their complexity and the very different scales involved, bursting phenomena are frequently investigated in the laboratory using simplified flow prototypes that capture the essential features of these large-scale instabilities. Such prototypes are usually based on simple geometries while the dominant mechanisms under study are preserved, e.g., the interaction between shear and rotation, convection or Lorentz forces. A bifurcation from full turbulence to an intermittently bursting turbulent regime was recently observed in large-gap Taylor-Couette flows with counterrotating cylinders [9]. The bifurcation was found to coincide with the optimal torque parameters. A striking feature of the large-scale instabilities in the aforementioned systems is their apparent low dimensionality, despite the fact that they happen in environments with intrinsic strong (usually turbulent) fluctuations. Nevertheless, the fundamen-tal cause of these large-scale dynamics is not always under-stood and it is often arduous to derive elementary models from first principles. In this Letter, we describe the occurrence of violent time-periodic bursts in an as yet unexplored parameter range of turbulent plane rotating Poiseuille flow (RPF), seen as a canonical example of interaction between shear and rota-tion. The flow develops a large-scale Linear instability under the influence of rotation even though it is strongly turbulent. This Linear instability is followed by a distinct sequence of Processes leading to a self-sustaining cycle of recurrent bursts of turbulence. We demonstrate that the Linear instability of the mean flow captures the essential features of the recurrent bursts. We thus argue that RPF is a relevant example of low-dimensional dynamics embedded in a high-dimensional system with strong fluctuations, and can serve as a new prototype for future studies of large-scale dynamics. The RPF case considered here is a pressure-driven plane channel flow between two smooth parallel flat walls subject to a global rotation about the spanwise axis orthogonal to the mean flow and parallel to the walls; see Fig. 1 for a schematic. The velocity field u is governed by the incom-pressible Navier-Stokes equations in the rotating frame

Dan S Henningson - One of the best experts on this subject based on the ideXlab platform.

  • recurrent bursts via Linear Processes in turbulent environments
    Physical Review Letters, 2014
    Co-Authors: Geert Brethouwer, Yohann Duguet, P. Schlatter, Dan S Henningson, Arne V. Johansson
    Abstract:

    Large-scale instabilities occurring in the presence of small-scale turbulent fluctuations are frequently observed in geophysical or astrophysical contexts but are difficult to reproduce in the laboratory. Using extensive numerical simulations, we report here on intense recurrent bursts of turbulence in plane Poiseuille flow rotating about a spanwise axis. A simple model based on the Linear instability of the mean flow can predict the structure and time scale of the nearly periodic and self-sustained burst cycles. Poiseuille flow is suggested as a prototype for future studies of low-dimensional dynamics embedded in strongly turbulent environments.

  • Recurrent bursts via Linear Processes in turbulent environments
    Physical Review Letters, 2014
    Co-Authors: Geert Brethouwer, Yohann Duguet, P. Schlatter, Dan S Henningson, Arne V. Johansson
    Abstract:

    Large-scale instabilities occurring in the presence of small-scale turbulent fluctuations are frequently observed in geophysical or astrophysical contexts but are difficult to reproduce in the laboratory. Using extensive numerical simulations, we report here on intense recurrent bursts of turbulence in plane Poiseuille flow rotating about a spanwise axis. A simple model based on the Linear instability of the mean flow can predict the structure and time scale of the nearly periodic and self-sustained burst cycles. Poiseuille flow is suggested as a prototype for future studies of low-dimensional dynamics embedded in strongly turbulent environments. Environments with strong fluctuations frequently display regular or chaotic large-scale dynamics. Well-known astro-physical examples are the reversals of large-scale planetary magnetic fields, which are chaotic for Earth but time periodic for the Sun [1]. Other geophysical and astrophysical man-ifestations of large-scale instabilities include climate cycles on Earth [2] and solar flares [3]. Random reversals of a large-scale circulation are also found in Rayleigh-Bénard convection [4], and in von Kármán [5] and laboratory fluid dynamo experiments [6]. Recurrent large-scale oscillations or bursts like in toka-mak plasmas [7] and accretion disks [8] are important manifestations of large-scale instabilities in the presence of (strong) fluctuations. Because of their complexity and the very different scales involved, bursting phenomena are frequently investigated in the laboratory using simplified flow prototypes that capture the essential features of these large-scale instabilities. Such prototypes are usually based on simple geometries while the dominant mechanisms under study are preserved, e.g., the interaction between shear and rotation, convection or Lorentz forces. A bifurcation from full turbulence to an intermittently bursting turbulent regime was recently observed in large-gap Taylor-Couette flows with counterrotating cylinders [9]. The bifurcation was found to coincide with the optimal torque parameters. A striking feature of the large-scale instabilities in the aforementioned systems is their apparent low dimensionality, despite the fact that they happen in environments with intrinsic strong (usually turbulent) fluctuations. Nevertheless, the fundamen-tal cause of these large-scale dynamics is not always under-stood and it is often arduous to derive elementary models from first principles. In this Letter, we describe the occurrence of violent time-periodic bursts in an as yet unexplored parameter range of turbulent plane rotating Poiseuille flow (RPF), seen as a canonical example of interaction between shear and rota-tion. The flow develops a large-scale Linear instability under the influence of rotation even though it is strongly turbulent. This Linear instability is followed by a distinct sequence of Processes leading to a self-sustaining cycle of recurrent bursts of turbulence. We demonstrate that the Linear instability of the mean flow captures the essential features of the recurrent bursts. We thus argue that RPF is a relevant example of low-dimensional dynamics embedded in a high-dimensional system with strong fluctuations, and can serve as a new prototype for future studies of large-scale dynamics. The RPF case considered here is a pressure-driven plane channel flow between two smooth parallel flat walls subject to a global rotation about the spanwise axis orthogonal to the mean flow and parallel to the walls; see Fig. 1 for a schematic. The velocity field u is governed by the incom-pressible Navier-Stokes equations in the rotating frame