Experimental Studies of the Turbulent Flow with Imposed Unsteadiness Structure

Author Name(s): Sabina M. Rzaeva, Lida A. Feoknistova, Tatiana V. Rzaeva, Irina P. Talipova
Author Email: aida_8691@rambler.ru

Abstract

The results of experimental studies of developed turbulent flow in a circular tube with superimposed flow pulsations are presented. They performed the measurements of time-averaged static pressure losses, instantaneous velocity values ​​in the cross section of the pipe and pulsation pressure components over a wide frequency range of superimposed airflow pulsations. They determined a nonmonotonic dependence of static pressure variation change on the frequency of superimposed pulsations. New data are obtained on the spatial temporal characteristics of turbulent flow in a pipe with superimposed flow pulsations. The phase shifts between parameter pulsations are revealed.

Introduction

Non stationary turbulent flows are often found in many technical devices the work of which is related to the flow of liquid and gas. Non-stationarity is the change of one or another flow characteristic in time. Turbulent flows are non-stationary flows a priori, since the parameters of the turbulent flow (velocity, temperature, etc.) vary in time randomly, even when the average values ​​of these parameters are not changed. An example of nonstationary turbulent flows is the flow at the outlet of a piston pump, the flow on the suction and the exhaust of the internal combustion engine, the boundary layer on the surface of the gas turbine blade rotating in the tracks behind the stator blades, the flow in the combustion chamber at the start and operation of the jet engine, etc.

At present, the most the kinematic structure of movable turbulent boundary layers is the most studied one. There are experimental studies by Bukreev and Shakhin, Grigoriev and Fafurin, Ramapryan and Tu, Achary and Reynolds, Cousteau, Carlson, Parikh, Simpson, Hartner, Misushin, Shemer, Iguchi and others.

The systematic theoretical and experimental studies of the turbulent gas flow under the conditions of hydrodynamic nonstationarity were carried out by G.A. Dreicer and V.M. Kraev [1-3]. The study of currents with periodic flow pulsations is complicated by the essential dependence of the hydrodynamic parameter profiles on the frequency and the amplitude of the superimposed pulsations. However, the obtained data do not provide a complete picture of flow nonstationarity factor influence through the channel on the hydrodynamic parameters in general and the hydraulic resistance in particular.

The purpose of the present studies is to obtain the experimental data on the spatial-temporal kinematic structure of a turbulent flow in a circular tube with periodic flow nonstationarity.

Conclusions

The experimental data about spatial-temporal structure of a turbulent flow in the tube with periodic nonstationarity are obtained. A nonmonotonic dependence of pressure drop change on the frequency of superimposed pulsations is established. The phase shifts between the pulsations of the parameters are revealed. It is established that in some flow regimes the amplitude of pressure pulsations exceeds the averaged pressure velocity. It is shown that the velocity profile becomes less filled in the phase of pressure increase, and the intensity of the velocity pulsations increases, and in certain regimes the probability to cause short-term flow separation near the pipe wall is high according to the frequency of superimposed pulsations.

Acknowledgements

The work is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University.

References

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