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Dynamical analysis of bistable mechanical oscillator
Byrtus, M. ; Půst, Ladislav
The contribution deals with analysis of dynamical properties of 1 DOF bistable mechanical oscillator. First the mathematical model is formulated. The original mathematical model is approximated by Duffing equation as it is commonly used. These two models are compared and it is shown how they differ in both static and dynamical response. The dynamical response is studied using bifurcation analysis performed by brute force numerical integration in time domain to detect area of interest from dynamical point of view. Such a bistable mechanical system can appear in many technical applications and therefore the proper modelling plays a significant role.
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Running flutter waves in the model of turbine blades cascade
Půst, Ladislav ; Pešek, Luděk
This contribution is connected with the paper on the previous conference, where the origin and properties of forced running waves produced by flowing steam through cascade of stationary and rotating wheels with different numbers of blades in the steam turbine were investigated. Due to the aero-elastic forces of this steam flow, these comparatively small vibrations can excite strong flutter running waves. Presented contribution is oriented on the analysis of dynamic properties of computational model of blades cascade, where the flutter is modelled by two types of Van der Pol self-excitation forces.
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Asymmetry of the response probability density of a system with parametric random noises
Náprstek, Jiří ; Fischer, Cyril
Recording of time variable processes is accompanied by various internal disturbing effects as a rule. They influence parameters of the measuring facility, transducer-device transmission, etc. These parasitic processes are usually of the random character and, consequently, they exercise as parametric noises. Moreover, the input signal mostly consists of a useful signal which can be taken as composed from deterministic and random additive part. Various combinations of these noises are the origin of random and also systematic measuring errors which can have under certain circumstances a cumulative character, deteriorate the output signal quality and can lead finally to the stochastic stability loss. These effects can be theoretically described using differential systems with stochastic coefficients and stochastic right hand side considering all input and output processes to be of the Markov type.
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