On vibrations of tubes filled by a gas-liquid bubbly medium

V.S.Fedotovsky, T.N.Vereshchagina, L.V.Terenik

State Scientific Center of the Russian Federation

Institute for Physics and Power Engineering named after A.I.Leipunsky

Bondarenko sq., 1, Obninsk, Kaluga Region, 249033, Russia

 

It is rather feasible approach for many vibroacoustic processes in heterogeneous mediums to be considered by means of efficient dynamic properties concept, which was developed by authors [1] during last years. Accordingly to the concept, a heterogeneous medium could be presented by a pseudo-uniform continuum with several efficient dynamic properties depending on medium component properties and vibroacoustic impact parameters. This approach provides enough clear account of the phenomena occurred after relative inter-phase vibration motion.

Gas and liquid density difference under bending vibrations of a tube with bubbly medium results in bubble vibrations under more pronounced amplitude than liquid does it. Therefore, inertial impact of the bubbly medium on tube vibrations is less than such calculated according actual mixture density. In such manner, the procedure for calculating the natural vibrations frequency of the system after well-established equations for linear tube mass should be supplemented by adding a mass due to medium vibrodensity.

On the other hand, the medium's dissipative losses, due to relative bubble/liquid displacements, result in hydrodynamic damping, i.e. resonance amplitudes of tube vibrations become decreasing ones. The fact is resulting to the vibroviscosity term providing an opportunity to account influence of the inertial and viscous interphase interaction on damping the tube vibrations.

The paper present experimental results for vibrodensity and vibroviscosity of gas-liquid medium with spherical bubbles; they are compared against theoretical equations. Bubbles shape evolution influence during relative bubbles to liquid displacement is discussed. The issue includes solving both the translational bubble vibration equation and the bubble vibration equation on the first spheroidal mode. Calculation results indicate a virtual existence of vibrodynamic properties dispersion due to resonance bubbles vibrations on the spheroidal mode. Experimental data of the authors ensure qualitative agreement of their computation findings.