Bhargav Vikas N, Francescato Nicola, Mettelsiefen Holger, Usmani Abdullah Y, Scarsoglio Stefania, Raghav Vrishank
Auburn University, Department of Aerospace Engineering, Auburn, 36849, AL, USA.
Politecnico di Torino, Department of Mechanical and Aerospace Engineering, Turin, 10129, Italy.
J Fluids Struct. 2024 Jun;127. doi: 10.1016/j.jfluidstructs.2024.104122. Epub 2024 Apr 24.
The interactions between fluid flow and structural components of collapsible tubes are representative of those in several physiological systems. Although extensively studied, there exists a lack of characterization of the three-dimensionality in the structural deformations of the tube and its influence on the flow field. This experimental study investigates the spatio-temporal relationship between 3D tube geometry and the downstream flow field under conditions of fully open, closed, and slamming-type oscillating regimes. A methodology is implemented to simultaneously measure three-dimensional surface deformations in a collapsible tube and the corresponding downstream flow field. Stereophotogrammetry was used to measure tube deformations, and simultaneous flow field measurements included pressure and planar Particle Image Velocimetry (PIV) data downstream of the collapsible tube. The results indicate that the location of the largest collapse in the tube occurs close to the downstream end of the tube. In the oscillating regime, sections of the tube downstream of the largest mean collapse experience the largest oscillations in the entire tube that are completely coherent and in phase. At a certain streamwise distance upstream of the largest collapse, a switch in the direction of oscillations occurs with respect to those downstream. Physically, when the tube experiences constriction downstream of the location of the largest mean collapse, this causes the accumulation of fluid and build-up of pressure in the upstream regions and an expansion of these sections. Fluctuations in the downstream flow field are significantly influenced by tube fluctuations along the minor axes. The fluctuations in the downstream flowfield are influenced by the propagation of disturbances due to oscillations in tube geometry, through the advection of fluid through the tube. Further, the manifestation of the LU-type pressure fluctuations is found to be due to the variation in the propagation speed of the disturbances during the different stages within a period of oscillation of the tube.
可塌陷管道中流体流动与结构部件之间的相互作用代表了多个生理系统中的此类相互作用。尽管已进行了广泛研究，但在管道结构变形的三维特征及其对流场的影响方面仍缺乏相关描述。本实验研究在完全打开、关闭和撞击式振荡状态下，探究了三维管道几何形状与下游流场之间的时空关系。实施了一种方法来同时测量可塌陷管道中的三维表面变形及相应的下游流场。使用立体摄影测量法来测量管道变形，同时进行的流场测量包括可塌陷管道下游的压力和平面粒子图像测速（PIV）数据。结果表明，管道中最大塌陷的位置靠近管道下游端。在振荡状态下，最大平均塌陷下游的管道部分在整个管道中经历最大的振荡，这些振荡完全相干且同相。在最大塌陷上游的某个流向距离处，振荡方向相对于下游发生了转变。从物理角度来看，当管道在最大平均塌陷位置下游经历收缩时，这会导致流体在上游区域积聚和压力升高，进而使这些部分膨胀。下游流场的波动受到沿短轴方向管道波动的显著影响。下游流场的波动受到管道几何形状振荡引起的扰动传播的影响，这种扰动通过流体在管道中的平流作用传播。此外，发现LU型压力波动的表现是由于在管道振荡周期的不同阶段扰动传播速度的变化所致。
