Vasily V. Vedeneev

Experimental investigation of single-mode panel flutter in supersonic gas flow

Panel flutter theory distinguishes between two types of the loss of stability, namely, the flutter of the coupled type and the single-mode flutter. The flutter of the coupled type is well studied, both theoretically and experimentally. The single-mode flutter has been theoretically studied only quite recently. This study is devoted to the experimental investigation of the single-mode panel flutter. The fact of its generation under actual conditions is established and the stability range is determined.

Experimental observation of single-mode panel flutter in a supersonic gas flow

Abstract. Single mode flutter is a type of panel flutter, which cannot be analyzed theoretically using conventional piston theory, and for this reason it is studied very little. No previous experiments, where this type of panel flutter was detected, were conducted. In this paper a plate, designed such that it cannot experience ”classical” coupled-type flutter, but can experience single mode flutter, is tested. Analysis of the tested data clearly indicates the occurrence of single mode panel flutter.

Transonic Panel Flutter in Accelerating or Decelerating Flow Conditions

Nonlinear panel flutter oscillations at transonic and low supersonic flow speed demonstrate rich panel dynamics, which includes bifurcations of the limit cycle, coexisting of different limit cycles...

Flutter of infinite elastic plates in the boundary-layer flow at finite Reynolds numbers

The stability of an infinite elastic plate in supersonic gas flow is investigated taking into account the presence of the boundary layer formed on the plate surface. The effect of viscous and temperature disturbances of the boundary layer on the behavior of traveling waves is studied at large but finite Reynolds numbers. It is shown that in the case of the small boundary layer thickness viscosity can have both stabilizing and destabilizing effect depending on the phase velocity of disturbance propagation.

Experimental Validation of Numerical Blade Flutter Prediction

Blade flutter of modern gas-turbine engines is one of the main issues that engine designers have to face. The most used numerical method that is employed for flutter prediction is the energy method. Although a lot of papers are devoted to the analysis of different blade wheels, this method was rarely validated by experiments. Typical mesh size, time step, and various modeling approaches that guarantee reliable flutter prediction are not commonly known, whereas some examples show that predictions obtained through nonvalidated codes can be inaccurate. In this paper, we describe our implementation of the energy method. Analysis of convergence and sensitivity to various modeling abstractions are carefully investigated. Numerical results are verified by compressor and full engine flutter test data. It is shown that the prediction of flutter onset is rather reliable so that the modeling approaches presented in this paper can be used by other researchers for the flutter analysis of industrial compressor blades.

NONLINEAR MULTI-MODAL PANEL FLUTTER OSCILLATIONS AT LOW SUPERSONIC SPEEDS

In this paper aeroelastic instability of a plate in a gas flow is investigated by direct time-domain numerical simulation. Plate deformation and gas flow are simulated in solid and fluid codes, respectively, with direct coupling between these codes. A series of simulations under different parameters has been conducted.Three types of the plate response have been observed: stability, static divergence and flutter. Depending on Mach number, two types of flutter were detected: single mode flutter and coupled mode flutter. At M = 1.8, a good correlation between the present study and the piston theory for coupled mode flutter has been obtained. At lower M, from 1 to 1.6, single mode flutter in 1st, 2nd and higher modes has been observed. Amplitudes and frequencies of flutter limit cycle oscillations have been studied. It is shown that limit cycle oscillations can occur in form of pure one-mode oscillations, or include 1:2 internal resonance, when fluttering mode excites another mode. In the region of Mach numbers from 1.3 to 1.5, where several plate modes are simultaneously unstable, transition from periodic to quasi-chaotic flutter oscillations occurs.© 2014 ASME

Formation of free round jets with long laminar regions at large Reynolds numbers

The paper describes a new, simple method for the formation of free round jets with long laminar regions by a jet-forming device of ∼1.5 jet diameters in size. Submerged jets of 0.12 m diameter at Reynolds numbers of 2000–12 560 are experimentally studied. It is shown that for the optimal regime, the laminar region length reaches 5.5 diameters for Reynolds number ∼10 000 which is not achievable for other methods of laminar jet formation. To explain the existence of the optimal regime, a steady flow calculation in the forming unit and a stability analysis of outcoming jet velocity profiles are conducted. The shortening of the laminar regions, compared with the optimal regime, is explained by the higher incoming turbulence level for lower velocities and by the increase of perturbation growth rates for larger velocities. The initial laminar regions of free jets can be used for organising air curtains for the protection of objects in medicine and technologies by creating the air field with desired properties not mixed with ambient air. Free jets with long laminar regions can also be used for detailed studies of perturbation growth and transition to turbulence in round jets.The paper describes a new, simple method for the formation of free round jets with long laminar regions by a jet-forming device of ∼1.5 jet diameters in size. Submerged jets of 0.12 m diameter at Reynolds numbers of 2000–12 560 are experimentally studied. It is shown that for the optimal regime, the laminar region length reaches 5.5 diameters for Reynolds number ∼10 000 which is not achievable for other methods of laminar jet formation. To explain the existence of the optimal regime, a steady flow calculation in the forming unit and a stability analysis of outcoming jet velocity profiles are conducted. The shortening of the laminar regions, compared with the optimal regime, is explained by the higher incoming turbulence level for lower velocities and by the increase of perturbation growth rates for larger velocities. The initial laminar regions of free jets can be used for organising air curtains for the protection of objects in medicine and technologies by creating the air field with desired properties n...

A New Method for the Formation of Free Jets with Long Laminar Regions

A new method for the formation of free jets with long laminar regions using a small-size device is proposed. A free jet with a 0.12 m diameter at Reynolds numbers in the range of 2000–12560 is experimentally studied using thermoanemometer measurements of velocity and turbulent fluctuations profiles and laser visualisation of the flow. It is shown that the designed technology forms the free jet with a laminar region length of 5.5 jet diameters for an optimal regime with Re \(\sim 10000\). Numerical simulation of the flow in the forming unit and an inviscid hydrodynamic instability analysis of the jet with calculated profiles have been conducted to explain the existence of the optimal regime.

EXPERIMENTAL STUDY OF SINGLE MODE PANEL FLUTTER

Single mode flutter is a type of panel flutter, which cannot be analyzed theoretically using conventional piston theory, and for this reason it is studied very little. In this paper a plate, designed such that it cannot experience “classical” coupled-type flutter, but can experience single mode flutter, is tested. Analysis of the tested data clearly indicates the occurrence of single mode panel flutter.Copyright

NUMERICAL ANALYSIS OF SINGLE MODE PANEL FLUTTER IN A VISCOUS GAS FLOW

In this paper single mode panel flutter, which occurs at low supersonic Mach numbers, is studied. Numerical analysis which does not require solution of coupled FSI problem has been conducted. Flutter boundaries obtained are compared with previously known analytical results.Copyright