Abstract In addition to the traditional hollow circular sections used in marine structures, other hollow sections have attracted the attention of architects and design engineers due to their mechanical characteristics such as torsional rigidity and local strength against impact loading. The purpose of this study is to investigate dynamic response of pipes conveying fluid with variable wall thickness through both circumferential and axial directions. Pipes with variable wall thickness have different flexural rigidities about two different principal axes. This property allows these pipes to be oriented efficiently, meet various design requirements and resist the applied loads. The results of this investigation provide a better insight into the physics and dynamic behavior of non-circular pipes conveying fluid. Two different geometries are studied, (i) the pipe is assumed with a general non-circular cross section with variable wall thickness along the circumferential direction, (ii) both inner and outer boundaries of the pipe cross section are assumed to be circles whereas the wall thickness of the pipe along axial direction is varied with a specified function. The governing differential equations of the problem are derived using Timoshenko beam theory with the effect of shear deformation included in the formulation. The discretization of the problem domain is done using the finite element method. Consequently, a modal analysis is employed to calculate the critical flow velocities of the pipe with clamped-clamped end conditions. The effects of different cross sections on the critical flow velocity are investigated. The importance of Coriolis forces on the presence of coupled-mode flutter and re-stabilization point are also discussed for different values of mass ratio.

中文翻译：

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周向和轴向变壁厚输送流体管道的动力学行为

摘要 除了用于海洋结构的传统空心圆型材外，其他空心型材因其抗扭刚度和抗冲击载荷局部强度等力学特性而引起了建筑师和设计工程师的关注。本研究的目的是研究管道在周向和轴向上输送壁厚可变的流体的动态响应。具有可变壁厚的管道在两个不同的主轴上具有不同的弯曲刚度。这种特性使这些管道能够有效地定向，满足各种设计要求并抵抗施加的载荷。这项调查的结果提供了对输送流体的非圆形管道的物理和动态行为的更好的了解。研究了两种不同的几何形状，(i) 假设管道具有沿圆周方向壁厚可变的一般非圆形横截面， (ii) 假设管道横截面的内外边界都是圆形，而管道的壁厚沿圆周方向轴向随特定函数变化。该问题的控制微分方程是使用 Timoshenko 梁理论推导出来的，公式中包含剪切变形的影响。问题域的离散化是使用有限元方法完成的。因此，采用模态分析来计算具有夹紧-夹紧末端条件的管道的临界流速。研究了不同截面对临界流速的影响。