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Computational aeroacoustics of human phonation
Šidlof, Petr ; Zörner, S.
The current paper presents a CFD model of flow past vibrating vocal folds coupled to an acoustic solver, which calculates the sound sources from the flow field in a hybrid approach. The CFD model is based on the numerical solution of 3D Navier-Stokes equations on a time-dependent domain, solved by cell-centered finite volume method. To capture the fine turbulent scales important for the acoustic source calculations, the equations are discretized and solved on large computational meshes up to 3.2M elements. The CFD simulations were run in parallel using domain decomposition method and OpenMPI implementation of the MPI standard. Aeroacoustic simulations are calculated in a separate step by Lighthill’s acoustic analogy, which determines the acoustic sources based on the fluid field. This is done with the research code CFS++ which employs the finite element method (FEM).
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Numerical simulations of the flow with the prescribed displacement of the airfoil and comparison with experiment
Řidký, Václav ; Šidlof, Petr ; Vlček, Václav
The work is devoted to comparing measured data with the results of numerical simulations. As mathematical model was used mathematical model whitout turbulence for incompressible flow In the experiment was observed the behavior of designed NACA0015 airfoil in airflow. For the numerical solution was used OpenFOAM computational package, this is open-source software based on finite volume method. In the numerical solution is prescribed displacement of the airfoil, which corresponds to the experiment. The velocity at a point close to the airfoil surface is compared with the experimental data obtained from interferographic measurements of the velocity field. Numerical solution is computed on a 3D mesh composed of about 1 million ortogonal hexahedron elements. The time step is limited by the Courant number. Parallel computations are run on supercomputers of the CIV at Technical University in Prague and on a computer cluster of the Faculty of Mechatronics of Liberec . Run time is fixed at five periods, the results from the fifth periods and average value for all periods are then be compared with experiment.
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Computational aeroacoustics of human phonation
Šidlof, Petr ; Zoerner, S.
The current paper presents a CFD model of flow past vibrating vocal folds coupled to an acoustic solver, which calculates the sound sources from the flow field in a hybrid approach. The CFD model is based on the numerical solution of 3D Navier-Stokes equations on a time-dependent domain, solved by cell-centered finite volume method. To capture the fine turbulent scales important for the acoustic source calculations, the equations are discretized and solved on large computational meshes up to 3.2M elements. The CFD simulations were run in parallel using domain decomposition method and OpenMPI implementation of the MPI standard. Aeroacoustic simulations are calculated in a separate step by Lighthill’s acoustic analogy, which determines the acoustic sources based on the fluid field. This is done with the research code CFS++ which employs the finite element method (FEM).
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Unsteady flows in convergent channel with stationary walls
Pořízková, P. ; Kozel, Karel ; Horáček, Jaromír
A current challenging question is a mathematical and physical description of the mechanism for transforming the airflow energy in human vocal tract (convergent channel) into the acoustic energy representing the voice source in humans. Goal of this work is to describe mathematical model of flow in 2D convergent channel which involves attributes of real flow as is “Coanda phenomenon”, vortex convection and diffusion, jet flapping etc. along with lower call on computer time, due to later extension in 3D channel flow.
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Numerical comparison of unsteady compressible viscous flow in convergent channel
Pořízková, P. ; Kozel, Karel ; Horáček, Jaromír
This study deals with a numerical solution of a 2D flows a compressible viscous fluids in a convergent channel for low inlet airflow velocity. Three governing systems – Full system, Adiabatic system, Iso-energetic system based on the Navier-Stokes equations for laminar flow are tested. The numerical solution is realized by finite volume method and the predictor-corrector MacCormack scheme with Jameson artificial viscosity using a gird of quadrilateral cells. This unsteady grid of quadrilateral cells is considered in the form of conservation laws using Arbitrary Lagrangian-Eulerian method. The numerical results, acquired from a developed program. Are presented for inlet velocity ûĄ = 4,12ms-1 and Reynolds number Re = 4 x 103.
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On higher-order space-time discretization of an nonlinear aeroelastic problem with the consideration of large displacements
Sváček, P. ; Horáček, Jaromír
This paper focuses on the mathematical and numerical modelling of interaction of the two-dimensional incompressible fluid flow and a flexibly supported airfoil section wit control section. A simplified problem is considered: The flow is modelled by the system of Navier-Stokes equations and the structure motion is described with the aid of nonlinear ordinary differential equations. The time-dependent computational domain is taken into account by the Arbitrary Lagrangian-Eulerian method. Higher order time discretization is considered within the stabilized finite element method. The application of the described method is shown.
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Numerical experiment of compressible flow in convergent channel- pressure spectral analysis
Pořízková, P. ; Kozel, Karel ; Horáček, Jaromír
This study deals with a numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The flow is described by the system of Navier-Stokes equations for laminar flows. The numerical solution is implemented using the finite volume method (FVM) and the predictor-corrector MacCormack scheme with Jameson artificial viscosity using a gird of quadrilateral cells. The numerical results of unsteady flows in the channel are presented for inlet velocity uĄ = 4.12m/s, inlet Reynolds number ReĄ = 4481 and wall motion frequency 100Hz.
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Numerical experiment of flow Mach in vocal tract
Pořízková, P. ; Kozel, K. ; Horáček, Jaromír
This study deals with the numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall, nearly closing the channel during oscillations. The channel is a simplified model of the glottal space in the human vocal tract. The flow is described by the full system of Navier-Stokes equations or by adiabatic system equations.
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