Coupling and Damping Effects on the Dynamics of Submerged Expanded Tubes in Borehole Wells

Hydraulic expansion of submerged tubes is accomplished by propelling a mandrel through it using differential pressure. This process deforms the tube beyond its elastic limit. Toward the end of the expansion process, the mandrel pops out of the tube resulting in displacement, stress, and pressure waves propagating through the system. A mathematical model has been developed to describe the dynamics of the tube-fluid system due to the pop-out phenomenon. The model takes into consideration the coupling effect between fluids and the structure, as well as the inherent system damping of its response. An analytical solution describing the wave propagation in the tube-fluid system was obtained. The model identified the potential failure locations and showed that the inherent system damping reduced the chances of failure but could not eliminate it completely. In addition, it showed that the coupling effect was more prominent in the tube as compared to the outer and inner fluids. Furthermore, a sensitivity analysis was conducted in order to investigate the effect of the geometrical and material properties on the response. The sensitivity analysis showed that the coupling effect vanished with the increase in tube stiffness and reached an asymptotic value with an increase in formation stiffness

Experimental Study and Numerical Simulation of Domes Under Wind Load

Dome structures are of architectural significance in many applications ranging from building decorations to fluid confinement usage such as pressure vessels and storage tanks in the petrochemical industry. Most domes are subjected to severe external loads caused by wind flow. Therefore, careful material selection and structural design of domes is imperative to avoid any unexpected failure. This paper presents the design of an experimental set-up to study the flow behavior around ABS dome models of hemispherical and elliptical shapes and their structural integrity under wind loads. The objective of this paper is to determine the dome’s wall thickness for various geometrical shapes. The domes were placed inside a wind tunnel where the wind speed was varied from 60 to 100 km/hr and pressure distribution on the surface of the dome roof was measured. Pressure measurements were carried out for various attack angles with respect to its centerline using a data acquisition system programmed in LabVIEW™. In addition, flow visualization of the air flow around the dome was carried out using a smoke generator. The experimental study was supplemented by a numerical simulation of the air flow around domes to mimic experiments using Computational Fluid Dynamics (CFD) techniques. The effect of wind on the dome structural integrity was studied using finite element analysis. The experimental results were used to validate the CFD models from which pressure distribution around domes were obtained. Results related to the pressure distribution around domes obtained from the CFD analysis were used as loading conditions to study the structural integrity of the domes using ANSYS™. Preliminary experimental results of wind speed effect on a hemispherical/elliptical dome revealed pressure variations for various angles of attack and height inclination along the dome roof surface.</jats:p