Three-dimensional direct numerical simulations of an incompressible open square cavity flow are c... more Three-dimensional direct numerical simulations of an incompressible open square cavity flow are conducted. Features of the permanent (non-linear) regime together with the linear stability analysis of a two-dimensional steady base flow are discussed. Spanwise boundary conditions are periodic and control parameters set such that the shear layer is stable against Kelvin-Helmholtz modes. Three branches of destabilising modes are found. The most destabilising branch is associated with steady modes, over a finite range of spanwise wavenumbers. The two other branches provide unsteady modes. Features of each branches are recovered in the permanent regime: wavelength of the most powerful spanwise Fourier mode, swaying phenomenon, angular frequencies, indicating that modes of each branches are selected and interact in the permanent flow.
Des mesures PIV résolues en temps sont effectuées sur un écoulement de cavité afin d'identifi... more Des mesures PIV résolues en temps sont effectuées sur un écoulement de cavité afin d'identifier le couplage entre la couche de cisaillement qui se développe au-dessus de la cavité, et le tourbillon de la recirculation dans la cavité. Des moyennes de phases sont calculées en prenant pour référence la position d'une structure tourbillonnaire de la couche de cisaillement. Un critère de stabilité de l'écoulement est déterminé pour les différentes phases.
Proteins take on their function in the cell by interacting with other proteins or biomolecular co... more Proteins take on their function in the cell by interacting with other proteins or biomolecular complexes. To study this process, computational methods, collectively named protein docking, are used to predict the position and orientation of a protein ligand when it is bound to a protein receptor or enzyme, taking into account chemical or physical criteria. This process is intensively studied to discover new biological functions for proteins and to better understand how these macromolecules take on these functions at the molecular scale. ...
The transition to unsteadiness of a three-dimensional open cavity flow is investigated using the ... more The transition to unsteadiness of a three-dimensional open cavity flow is investigated using the joint application of direct numerical simulations and fully three-dimensional linear stability analyses, providing a clear understanding of the first two bifurcations occurring in the flow. The first bifurcation is characterized by the emergence of Taylor–Görtler-like vortices resulting from a centrifugal instability of the primary vortex core. Further increasing the Reynolds number eventually triggers self-sustained periodic oscillations of the flow in the vicinity of the spanwise end walls of the cavity. This secondary instability causes the emergence of a new set of Taylor–Görtler vortices experiencing a spanwise drift directed toward the spanwise end walls of the cavity. While a two-dimensional stability analysis would fail to capture this secondary instability due to the neglect of the lateral walls, it is the first time to our knowledge that this drifting of the vortices can be ent...
This paper reports results obtained with two-dimensional numerical simulations of viscous incompr... more This paper reports results obtained with two-dimensional numerical simulations of viscous incompressible flow in a symmetric channel with a sudden expansion and contraction, creating two facing cavities; a so-called double cavity. Based on time series recorded at discrete probe points inside the double cavity, different flow regimes are identified when the Reynolds number and the intercavity distance are varied. The transition from steady to chaotic flow behaviour can in general be summarized as follows: steady (fixed) point, period-1 limit cycle, intermediate regime (including quasi-periodicity) and torus breakdown leading to toroidal chaos. The analysis of the intracavity vorticity reveals a ‘carousel’ pattern, creating a feedback mechanism, that influences the shear-layer oscillations and makes it possible to identify in which regime the flow resides. A relation was found between the ratio of the shear-layer frequency peaks and the number of small intracavity structures observed ...
The aim of the present study is to characterize the velocity field in a cylindrical standing-wave... more The aim of the present study is to characterize the velocity field in a cylindrical standing-wave resonator, filled with nitrogen confined at high mean pressure, with a thermoacoustic wave generator. First order velocity (acoustic field) and second order velocity (streaming field) are measured simultaneously with Particle Image Velocimetry (PIV), based on the optical flow technique. Two methods are used in:
We present an experimental parametric study of spanwise centrifugal instabilities in an open cavi... more We present an experimental parametric study of spanwise centrifugal instabilities in an open cavity flow. We show that the mode selected at threshold depends on the cavity streamwise aspect ratio. For small aspect ratio, a steady mode is enhanced, while travelling waves are observed for large aspect ratio. The bifurcation is found to be supercritical for all configurations. Sidewall effects are shown to generate secondary flows that carry the vortical patterns. Spanwise confinement enhances the family of steady modes relative to the family of oscillatory modes. These results are discussed with respect to predictions from linear stability analyses and other flows developing centrifugal instabilities.
Three-dimensional direct numerical simulations of an incompressible open square cavity flow are c... more Three-dimensional direct numerical simulations of an incompressible open square cavity flow are conducted. Features of the permanent (non-linear) regime together with the linear stability analysis of a two-dimensional steady base flow are discussed. Spanwise boundary conditions are periodic and control parameters set such that the shear layer is stable against Kelvin-Helmholtz modes. Three branches of destabilising modes are found. The most destabilising branch is associated with steady modes, over a finite range of spanwise wavenumbers. The two other branches provide unsteady modes. Features of each branches are recovered in the permanent regime: wavelength of the most powerful spanwise Fourier mode, swaying phenomenon, angular frequencies, indicating that modes of each branches are selected and interact in the permanent flow.
Des mesures PIV résolues en temps sont effectuées sur un écoulement de cavité afin d'identifi... more Des mesures PIV résolues en temps sont effectuées sur un écoulement de cavité afin d'identifier le couplage entre la couche de cisaillement qui se développe au-dessus de la cavité, et le tourbillon de la recirculation dans la cavité. Des moyennes de phases sont calculées en prenant pour référence la position d'une structure tourbillonnaire de la couche de cisaillement. Un critère de stabilité de l'écoulement est déterminé pour les différentes phases.
Proteins take on their function in the cell by interacting with other proteins or biomolecular co... more Proteins take on their function in the cell by interacting with other proteins or biomolecular complexes. To study this process, computational methods, collectively named protein docking, are used to predict the position and orientation of a protein ligand when it is bound to a protein receptor or enzyme, taking into account chemical or physical criteria. This process is intensively studied to discover new biological functions for proteins and to better understand how these macromolecules take on these functions at the molecular scale. ...
The transition to unsteadiness of a three-dimensional open cavity flow is investigated using the ... more The transition to unsteadiness of a three-dimensional open cavity flow is investigated using the joint application of direct numerical simulations and fully three-dimensional linear stability analyses, providing a clear understanding of the first two bifurcations occurring in the flow. The first bifurcation is characterized by the emergence of Taylor–Görtler-like vortices resulting from a centrifugal instability of the primary vortex core. Further increasing the Reynolds number eventually triggers self-sustained periodic oscillations of the flow in the vicinity of the spanwise end walls of the cavity. This secondary instability causes the emergence of a new set of Taylor–Görtler vortices experiencing a spanwise drift directed toward the spanwise end walls of the cavity. While a two-dimensional stability analysis would fail to capture this secondary instability due to the neglect of the lateral walls, it is the first time to our knowledge that this drifting of the vortices can be ent...
This paper reports results obtained with two-dimensional numerical simulations of viscous incompr... more This paper reports results obtained with two-dimensional numerical simulations of viscous incompressible flow in a symmetric channel with a sudden expansion and contraction, creating two facing cavities; a so-called double cavity. Based on time series recorded at discrete probe points inside the double cavity, different flow regimes are identified when the Reynolds number and the intercavity distance are varied. The transition from steady to chaotic flow behaviour can in general be summarized as follows: steady (fixed) point, period-1 limit cycle, intermediate regime (including quasi-periodicity) and torus breakdown leading to toroidal chaos. The analysis of the intracavity vorticity reveals a ‘carousel’ pattern, creating a feedback mechanism, that influences the shear-layer oscillations and makes it possible to identify in which regime the flow resides. A relation was found between the ratio of the shear-layer frequency peaks and the number of small intracavity structures observed ...
The aim of the present study is to characterize the velocity field in a cylindrical standing-wave... more The aim of the present study is to characterize the velocity field in a cylindrical standing-wave resonator, filled with nitrogen confined at high mean pressure, with a thermoacoustic wave generator. First order velocity (acoustic field) and second order velocity (streaming field) are measured simultaneously with Particle Image Velocimetry (PIV), based on the optical flow technique. Two methods are used in:
We present an experimental parametric study of spanwise centrifugal instabilities in an open cavi... more We present an experimental parametric study of spanwise centrifugal instabilities in an open cavity flow. We show that the mode selected at threshold depends on the cavity streamwise aspect ratio. For small aspect ratio, a steady mode is enhanced, while travelling waves are observed for large aspect ratio. The bifurcation is found to be supercritical for all configurations. Sidewall effects are shown to generate secondary flows that carry the vortical patterns. Spanwise confinement enhances the family of steady modes relative to the family of oscillatory modes. These results are discussed with respect to predictions from linear stability analyses and other flows developing centrifugal instabilities.
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