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Numerické simulace interakce neviskozního a viskozního proudění nestlačitelné tekutiny s vibrujícím profilem
Honzátko, R. ; Horáček, Jaromír ; Kozel, Karel
The work deals with a numerical solution of the interaction of 2D incompressible flows and a freely vibrating profile with large amplitudes. The profile can oscillate around an elastic axis and in the vertical direction. The motion of the profile is described by two nonlinear ordinary differential equations solved numerically using four-order Runge-Kutta method. The Euler or Navier-Stokes equations represent the inviscid or viscous flows. Numerical schemes of the finite volume method are applied on a structured quadrilateral C-mesh. The method of artificial compressibility and dual-time stepping method are employed for numerical solution. Deformations of the computational domain due to the profile motion are treated using the ALE method.
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Vibrace leteckéhoj profilu se třemi stupni volnosti vybuzené proudem vzduchu
Růžička, M. ; Feistauer, M. ; Horáček, Jaromír ; Sváček, Petr
The subject of this article is the numerical simulation of the interaction of two-dimensional incompressible viscous fluid and a vibrating airfoil with large amplitudes. a solid airfoil with three degrees of freedom can rotate around the elastic axis, oscillate in the vertical direction and its flap can rotate. the numerical simulation consists of the finite element solution of the Navier-Stokes equations coupled with a system of nonlinear ordinary differential equations describing the airfoil motion. The time-dependent computational domain and moving grid are taken into account with the aid of the Arbitrary Lagrangian-eulerian (ALE) formulation. High Reynolds numbers up to 10 6 require the application of a suitable stabilization of the finite element discretization. Numerical tests and comparison with NASTRAN solver prove that the developed method is sufficiently accurate and robust.
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Vizualizace nestacionárního proudění kolem vibrujícího profilu
Vlček, Václav ; Horáček, Jaromír ; Luxa, Martin ; Veselý, Jan
The contribution presents results of optical measurements of flow field around a vibrating double circular arc (DCA) 18% profile elastically supported in the measurement section of a wind tunnel. The profile can vibrate with two degrees of freedom for translation and rotation. the schlieren and interferometry methods were used for visualization of a two-dimensional flow in different phase of the profile motion. The measurements were performed in a subsonic wind tunnel above the airflow velocity for loss of the system stability by flutter, thus the vibration amplitudes were relatively large up to about+-4mm for vertical translation and +-6 degrees for angle of rotation around the elastic axis. The images of the flow field were recorded for prescribed phase delays during one oscillation period of the profile from which the pressure and velocity were evaluated in given time instants.
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Dynamic characteristics and stability of cylindrical shell conveying fluid
Horáček, Jaromír ; Dubuc, F.
Natural frequencies and the thresholds for loosing the hydroelastic stability of thin-walled cylindrical shell conveying fluid are theoretically studied. Potential flow theory for fluid and semi-membrane theory for the shell are used. The viscous fluid forces are modelled by the Darcy law. The fundamental importance of boundary conditions considered for fixing the edges of the cylindrical shell of finite length is shown.
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