Flow-Induced Vibrations of a Rotated Square Tube Array Subjected to Single-Phase Cross-Flow

This paper investigates the flow-induced vibration (FIV) and possibility of fluidelastic instability occurrence in a rotated square geometry tube array through a series of experimental tests. All experiments presented here were conducted in water cross-flow. The array pitch spacing ratio of approximately P/D=1.64 is somewhat larger than that commonly found in typical steam generators. The stability of a single flexible tube as well as multiple flexible tubes were investigated. The tubes were free to vibrate purely in the streamwise direction or the transverse direction relative to the upstream flow. A single flexible tube, in the otherwise rigid tube array, was found to undergo large amplitude vibrations (up to 40 % D) in the transverse direction. Tube vibration frequency analysis indicated the presence of two frequency components related to vorticity shedding in the array. This potential vorticity-induced-vibrations (VIV) and potential coupling between VIV and FEI are discussed in the paper. Test results for streamwise flow-induced vibrations are also presented. Results in water flow show a possible effect related to flow periodicity at low velocity. At significantly high flow velocities, the tubes are found to fully restabilize. This restabilization after VIV locking has not been previously reported as an unlocking result. The present results suggest that the flow-induced vibration of tubes in a rotated square array configuration is significantly more complex than in other geometries, particularly for the streamwise vibration case.

The Postbuckling Behavior of Compressed Elastica Inside a Flexible Tube: Experimental and Numerical Investigation

The post-buckling behavior of an elastic fiber subjected to lateral constraints is of practical importance in a wide range of medical and engineering applications. The vast majority of existing studies have adopted the assumption that the lateral constrains are fixed in space and rigid. This assumption is often far from the reality of the physical complexity of the abovementioned systems. In this paper, we study analytically, numerically, and experimentally, the behavior of an elastic fiber that is subjected to compressive force and constrained by a flexible tube. The latter marks a point of departure from available research. Our experiments provide quantitative information related to the overall behavior of the system, like force-shortening relation and deflection of the flexible tube. That information is complemented by finite-element simulations that enable in-depth analysis of the deformation of the fiber as well as contact characteristics between the fiber and the inner wall of the flexible tube. Finally, a simple mathematical model, aimed at providing analytical insights, is presented. Overall, the theoretical, numerical, and experimental results are in very good agreement. They highlight the fact that the behavior of a compressed fiber that is constrained by a deformable tube significantly deviates from that of a fiber constrained inside a rigid cylinder. Moreover, it is shown that the overall behavior as well as the evolution of contact between the fiber and the cylinder heavily depend on the ratio between the stiffness of the fiber and the lateral stiffness of the tube.

Esophageal Obstruction in Buffaloes (Bubalus bubalis) Resulting from the Ingestion of Potato Tubers

Total 32 emergency cases of buffaloes with esophageal obstruction resulting from the ingestion of potato tubers during their grazing are described. Treatment comprised immediate rumen trocarisation by a 14g syringe, premedication with IM xylazine (0.05 mg/kg), and passing a designed stout flexible tube to dislodge the obstruction to the rumen. The results were 100% successful recovery without any complications.

Flow-Induced Vibration Behaviour of a Rotated Square Tube Array Subjected to Cross-Flow

The present paper presents experimental tests investigating flow-induced vibration and possible fluidelastic instability (FEI) in a rotated square geometry tube array. The pitch spacing ratio of approximately P/D = 1.64 is somewhat larger than that found in typical array geometries. Experiments were conducted in water flow. The stability of a single flexible tube as well as multiple flexible tubes was investigated. The tubes were free to vibrate purely in the streamwise direction or the transverse direction relative to the upstream flow. A single flexible tube, in the otherwise rigid tube array, was found to undergo large amplitude vibrations (up to 40% D) in the transverse direction. Tube vibration response PSDs indicated the presence of two frequency components related to vorticity shedding in the array. This potential vorticity-induced-vibrations (VIV) and potential coupling between VIV and FEI is discussed in the paper. Test results for streamwise flow-induced vibrations are also presented. Results in water flow show a possible effect related to VIV at low velocity. At significantly high flow velocity, the tubes are found to fully restabilize. This restabilization after VIV locking has not been previously reported as an unlocking result. The present results suggest that flow-induced vibration of tubes in a rotated square array configuration is significantly more complex than in other geometries, particularly for the streamwise vibration case.

Peristaltic pumping of Ellis fluid through a flexible tube with complete slip effects

The paper investigates the role of complete velocity slip on the axisymmetric peristaltic transport of Ellis fluid through a uniform flexible tube considering the long wavelength and tiny Reynolds number assumptions. The equations governing the axisymmetric flow are solved and provided the analytical expressions for axial velocity, stream function, pressure difference for shear thickening and shear thinning fluids and the effect of emerging parameters on the pressure rise with time averaged flux and stream line patterns have been discussed graphically. The trapping phenomenon results showed that the size of trapping bolus enhances with increasing values of first and second slip parameters.