内激励型振荡衰减流作用下输流管道动力不稳定分析

振荡衰减流作为一种内激励形式,对输流管道的稳定性和共振特性将产生影响.基于输流管道横向振动运动微分方程,引入指数衰减函数模拟水锤发生时流速呈现的振荡衰减特性,推导得到内激励型振荡衰减流作用下输流管道动力不稳定区域的表达式.在无衰减周期脉动流激励条件下,计算得到两种不同支撑输流管道的不稳定区域,与前人数值研究结果吻合良好...

Dynamic instability analysis of pipeline conveying fluid under action of internally excited oscillation attenuation flow

As an internal excitation form,oscillation attenuation flow significantly affects the stability and resonance characteristics of fluid-conveying pipeline.Here,based on the differential equation of transverse vibration of pipeline conveying fluid,the exponential attenuation function was introduced to simulate oscillation attenuation characteristics of flow velocity when water hammer happening,and the expression of dynamic instability region of pipeline conveying fluid under the action of internally excited oscillation attenuation flow was derived.Under the condition of unattenuated periodic pulsating flow excitation,the unsteady regions of two kinds of pipelines with different supports were calculated,they were in good agreement with the previous numerical results published.Meanwhile,compared with the velocity time history calculated using viscoelastic pipe model under water hammer,it was shown that the proposed velocity expression can better reflect bidirectional attenuation characteristics of flow in the pipeline under water hammer excitation.Furthermore,the influence of attenuation characteristic parameters on the unstable region of simply supported pipeline was analyzed.The results showed that the influence of the internally excited oscillation attenuation flow on the transverse vibration of the pipeline can’t be ignored;when the flow velocity attenuation coefficient b increases,the unstable region moves downward,and when the initial flow velocity u 0 increases,shifting phenomenon becomes more obvious;at the same time,with passage of time and increase in attenuation coefficient b,the faster the flow velocity attenuation and the faster the closure of unstable region;when flow velocity attenuation reaches 0,water hammer process is over,unstable area of pipeline disappears.