
Selfexcited oscillation properties of the profile NACA0015 in subsonic flow
Zolotarev, Igor ; Vlček, Václav ; Kozánek, Jan
Selfexcited oscillations of the profile NACA0015 in subsonic flow were realized in the wind tunnel. The plunge support had the same elasticity for all experiments, the pitch support had seven different elasticity parameters. During our experiments different types of selfexcited vibration (flutter, stall flutter) were observed. Range of Mach numbers was M = 0.08–0.45, corresponding range of Reynolds numbers is Re = (1–5)·105, when the chord length is used as the characteristic dimension of the profile.\n


DYMAMESI 2017
Kozieň, M. ; Pešek, Luděk ; Zolotarev, Igor
The Colloquium Dymamesi is continuing near the 20 years history of two conferences Dynamics of Machines and Interaction and Feedbacks. From 2017 the Colloquium is organized within the CzechPolish (IT ASCR Prague & CUT Crakow) collaboration and the first one was held in CUT in Cracow. The prezentations were divided into the three sections: dynamics of machines, interactions and energetics. The Colloquium DYMAMESI 2017 was for the first time supported also by Programme Strategy 21 (AV21).

 

Some experimentally determined properties of a profile in case of selfexcited oscillations in subsonic flow
Vlček, Václav ; Zolotarev, Igor ; Kozánek, Jan ; Šidlof, Petr ; Štěpán, M.
In the wind tunnel of the Institute of Thermomechanics of the AS CR,v .v. i., experiments were realized with the profile NACA0015 in the presence of the selfexcited oscillation. The oscillation of the profile with pitch and plunge degrees of freedom was excited by the subsonic air flow. The plunge support had the same elasticity for all experiments, the pitch support had seven different values of elasticity. Within experiments different types of selfexcited vibration (flutter, stall flutter, deep stall flutter) were realized. Range of Mach numbers were M=0.08–0.45, when the chord length is used as the characteristic dimension of the profile. The frequency and amplitude characteristics of the oscillating profile were experimentally determined.\n


The effect of the pitch support elasticity on the NACA0015 profile aeroelastic properties
Vlček, Václav ; Zolotarev, Igor ; Kozánek, Jan
The aeroelastic experiments realized in wind tunnel of the Institute of Thermomechanics with Mach numbers M ~ 0.200.22 and with the interval of Reynolds numbers Re = (2.42.6).105, are presented. These results correspond to the selfexcited vibration of the profile NACA0015 with two degrees of freedom allowing the profile rotation in 1/3chord axis and allowing the vertical displacement of the profile. The dependence of vibration frequency on the windflow velocity has been obtained. Comparing with the previous experiments the influence of the pitch support elasticity on the profile aeroelastic properties was determined.


Computation of aerodynamic damping in aeroelastic system based on analytical and numerical approach
Chládek, Štěpán ; Horáček, Jaromír ; Zolotarev, Igor
The paper describes computation of aerodynamic damping and natural frequencies of aeroelastic systems. The damping is a critical parameter for the stability analysis of aeroelastic systems. Structural damping of the system is important for very low fluid flow velocities, however by increasing the flow velocity, the aerodynamic damping dominates in the instability search. The damping can be evaluated in time or in frequency domain. The presented computation of aerodynamic damping consists of two analytical and one numerical approach. The analytical approaches are represented by the wellknown pk method and the unsteady panel method. The pk method is based on Theodorsen unsteady aerodynamics and on the computation of complex eigenvalues of the system as functions of the flow velocity. The unsteady panel method enables the computation of the interaction between aeroelastic system and fluid flow. The aerodynamic damping is evaluated in time domain from the system response to given initial conditions. The numerical approach is based on the finite volume method (FVM) modelling the complete fluidstructure interaction (FSI) coupled problem. The aerodynamic damping is also computed from the system response to a given initial condition. The results of the mentioned methods are compared for the profile NACA 0012 with two degrees of freedom (2DOF) for plunge and pitch motion around an elastic axis.


ENGINEERING MECHANICS 2016  Book of full texts
Zolotarev, Igor ; Radolf, Vojtěch
The 22nd International Conference EM2016 aims to provide a forum for researchers, industry practitioners, engineers and postgraduate scholars to promote exchange and disseminate knowledge and experiences of the most recent results and advances in a wide range of topics in Engineering Mechanics, including, but not limited to: Biomechanics, Dynamics, Fluid Mechanics, Fracture Mechanics, Kinematics, Mechanics of Solids, Mechatronics, Reliability of Structures and Thermomechanics.


DYMAMESI 2016  proceedings
Zolotarev, Igor ; Pešek, Luděk
Proceedings of the Colloquium DYNAMICS OF MACHINES AND MECHANICAL SYSTEMS WITH INTERACTIONS (DYMAMESI), that was held in the Institute of Thermomechanics in Prague, March 1  2, 2016 deal with problems structural and multibody dynamics, in coupled interacting systems as aeroelasticity, hydroelasticity, biomechanics, systems with feedbacks and mechatronics. The published papers was divided into the two parts: Interactions  vibration of dynamic systems coupled with surroundings, mechanical systems with feedbacks, mechatronic active elements, measurement methods and identification in interaction problems, interactions in biomechanics, aero and hydroelasticity in rotational engines (bearings, blades, sealings, spaces), analytical and numerical methods in solutions of interactions and Dynamics of Machines  dynamics and vibrations of mechanical systems and solids, nonlinear systems  stability, bifurcations, chaos, damping technologies  materials, active elements, methods, identification, vibrodiagnostics, fatigue, computational mechanics and experiments.


Evaluation of aerodynamic damping and natural frequencies from numerical simulations and experiments
Chládek, Štěpán ; Horáček, Jaromír ; Zolotarev, Igor
The paper describes different ways for aerodynamic damping and natural frequencies evaluation in a problem of fluidstructure interaction. It is useful for both numerical simulations and experimental measurements. The Fourier transform is used for the frequency evaluation and the damping is evaluated both in time and frequency domain. Significant influence of the chosen sampling frequency and the length of time record on the accuracy of the results are demonstrated both in the numerical simulation and in the experiment that was performed with the flexibly supported profile NACA 0012 with two degrees of freedom.


Some atypical flutter characteristics of the NACA0015 profile
Vlček, Václav ; Zolotarev, Igor ; Kozánek, Jan ; Štěpán, M.
The part of the aeroelastic experiments with profile carried out in wind tunnel of the Institute of Thermomechanics, v.v.i. at stream velocity M = 0.150.38 in the interval of Reynolds numbers Re = (1.85.0)•105 is presented. The results relate to the selfexcited vibration of the profile NACA0015, which had two degrees of freedom allowing rotation and transverse displacement of the profile. The elasticity of the two degrees of freedom support has not been, during the experiments, changed. The dependence of Strouhal numbers on the speed of the stream.has been obtained. In one case the excitation of an unstable state occured and during the measurement the jump to a stable state arised. The kinematics of the model during this transition is described.in detail.
