The fundamental natural frequency and critical flow velocity evaluation of a simply supported stepped pipe conveying fluid

Abstract EN

This work investigated the fundamental natural frame frequency and critical inlet flow velocity of the simply supported stepped pipe conveying fluid.

The influence of some outline parameters, similar pipe diameter ratio with different cross-sectional areas (sudden enlargement or sudden contraction), length ratio, and thickness were studied.

A theoretical model for the dynamic behavior of the pipe was investigated.

The dynamic behavior of the stepped pipe carrying fluid was described by means of finite element technique.

A computer program has been promoted utilizing Matlab language in order to predict the vibration characteristics and to embrace the theoretical work.

It was found that the fundamental natural frequency of the stepped pipe decreased in different percentages with increasing inlet fluid flow velocity.

The outer diameter ratio, length ratio, and thickness of the stepped pipe conveying fluid had a great effect on the dynamic behavior of stepped pipe.

The fundamental natural frame frequency increased as the length ratios (L2/L1) and the outer diameter ratios (Od2/Od1) decreased.

When the length ratio of the pipe being less than 1, the effect of the diameter ratio on the critical inlet flow velocity was obvious.

As the outer diameter ratios (Od2/Od1) increased, the inlet critical flow velocity increased, until being reached to the maximum value, then it dropped smoothly.

The fundamental frame frequency of the stepped pipe increased as the thickness of the stepped pipe increased until being reached to the maximum value ,then it dropped smoothly.

For each inlet fluid flow velocity, length ratios, and diameter ratios there was an optimum pipe thickness that gave the best dynamic characteristics