A Coupled Two-Way Fluid-Structure Interaction Analysis for the Dynamics of a Partially Confined Cantilevered Pipe Under Simultaneous Internal and External Axial Flow in Opposite Directions

This paper presents the results of a coupled two-way fluid-structure interaction analysis of a slender flexible vertical cantilevered pipe hanging concentrically within a shorter rigid tube forming an annulus. The pipe is subjected to internal and annular flows simultaneously. This system has applications in brine production and salt-cavern hydrocarbon storage. In the present study, the fluid-structure problem is solved with a finite-volume-based CFD code for the fluid domain coupled to a finite-element-based CSM code for the structural domain. The numerical results obtained for the free-end displacement of the central pipe versus the annular/internal flow velocity ratio U_o/U_i are presented and compared with those obtained from experiment. The capability of the numerical model to predict the onset of the experimentally observed flutter instability in the system is also examined. This provides a better insight into the dynamics of the system.

Development of micro soap bubble generator for PIV tracer using home stereolithography 3D printer

A micro soap bubble generator for tracers for PIV measurement was developed using a home stereolithography 3D printer. The nozzle has a coaxial triple pipe structure, and an orifice cap is attached to the nozzle head. The inner diameter of the central pipe is 0.7 mm, and the wall thickness of the central pipe is 0.7 mm. From the comparison of the smoke wire visualization result of the flow around the cylinder placed under the mainstream flow velocity of 3 m/s and the PIV measurement result, it was confirmed that the generated micro soap bubbles have good followability to the flow. Generated bubbles’ particle size was estimated to be Φ0.2 mm at the minimum and Φ6.3 mm at the maximum. The most common was Φ0.9 mm ± 0.1 mm, accounting for more than 50% of the total.

Axisymmetric model of the sealing cylinder in service: analytical solutions

The stress state analysis of the sealing cylinder is of great significance for the safe operation of the sealing system. In this study, we probe a sealing system that can be simplified as an axisymmetric problem. In service, the rubber around the central pipe contacts the casing under the action of the axial pressure, and thus the sealing function is realized. The analytical solution of the stress at the sealing interface is derived based on the Love strain function in the axisymmetric configuration. Then, the relationship between the axial pressure and the gap (between the sealing cylinder and the casing) is presented, and the contact pressure at the contact interface is also given. The numerical simulation is performed, which is in agreement with the analytical solutions in the two deformation stages. The obtained results in the current work have also been comprehensively compared with the previous results, to give suggestions for engineering selection. These findings are beneficial to obtain a deep understanding on the mechanism of the sealing process, and provide some inspirations on the new types of sealing tools for mechanical engineering, chemical engineering, petroleum engineering, etc.

A unit-cell model for thermal regulation of degradation of organics in solid waste

It is a well appreciated fact that temperature is one of the key factors influencing the degradation of organics. Heat exchangers are a viable option that can be used to adjust the temperature in solid waste to an extent most suitable for waste degradation. This paper focuses on an experimental and theoretical investigation of the feasibility of using a water-circulating heat exchanger for thermal regulation of waste degradation. A cylindrical bioreactor with a central pipe connected to a water circulation system is devised and instrumented. The changes in temperature and gas production were monitored during the degradation of the organic component of the waste. Test results with and without thermal regulation are analyzed and compared. In addition, an analytical model is proposed to simulate the symmetrical heat transport behavior subjected to heat exchange. Heat generation due to the degradation of organics is taken into account. There was a good correlation between the analytical model prediction and the experimental data obtained from the laboratory test and field monitoring.

Simulation of the effectiveness of longitudinal rectangular fins on the efficiency of the double pipe heat exchanger

In this article, a mathematical simulation of a double pipe heat exchanger is carried out, having the longitudinal rectangular fins with the dimension of (2*3*1000) mm, mounted on the outer surface of the inner tube of the heat exchanger. In this paper, the advantage of using of that type of fins and its effect on the effectiveness of the heat exchanger are studied with the help of the computer program. The carried out research allowsmaking the calculation to find the optimum design parameters of heat exchangers. The outer tube diameter is (34.1mm) while the inner tube diameter is (16.05mm). The tubes wall thickness is (1.5mm) and the model length was (1 m). The hot water is flowing through the inner tube in parallel with the cold water that passing the outer tube. The hot and cold water temperature at the inlet is (75°C & 30°C) respectively. The mass flow rate inside the central pipe is (0.1 kg/s) while the annular pipe carrying (0.3 kg/s). In the present work, the program ANSYS Workbench 15.0 was used to find out the results of heat transfer as well as the behavior of liquids inside the heat exchangers.

Analysis of Subsea Umbilical Mechanical Behavior Under Simultaneous Bending, Tension and Torsion

One of the major failure modes of an umbilical is found to occur under simultaneous bending, tension and torsion. Umbilical cables are compatible in bending but have a rigid response to tension and torsion, hence validation the axisymmetric performance of it, is a significant matter. This paper has applied theoretical models to analyze umbilical cables mechanical behavior under combined loading. Lanteigne (1985) theoretical model, which its feature is a large-diameter central pipe umbilical cross section with homogeneous materials that a number of wires helically wrapped around it, is developed in this article. The equilibrium equations are presented and showed the helical elements effects on bending, tension and torsion of the umbilical cable.

Kill Line Model Cross Flow Inline Coupled Vortex-Induced Vibration

Currents and waves cause flow-structure interaction problems in systems installed in the ocean. Particularly for bluff bodies, vortices form in the body wake, which can cause strong structural vibrations (Vortex-Induced Vibrations, VIV). The magnitude and frequency content of VIV is determined by the shape, material properties, and size of the bluff body, and the nature and velocity of the oncoming flow. Riser systems are extensively used in the ocean to drill for oil wells, or produce oil and gas from the bottom of the ocean. Risers often consist of a central pipe, surrounded by several smaller cylinders, including the kill and choke lines. We present a series of experiments involving forced in-line and cross flow motions of short rigid sections of a riser containing 6 symmetrically arranged kill and choke lines. The experiments were carried out at the MIT Towing Tank. We present a systematic database of the hydrodynamic coefficients, consisting of the forces in phase with velocity and the added mass coefficients that are also suitable to be used with semi-empirical VIV predicting codes.

Radiant recuperator modelling and design

Recuperators are frequently used in glass production and metallurgical processes to preheat combustion air by heat exchange with high temperature flue gases. Mass and energy balances of a 15 m high, concurrent radiant recuperator used in a glass fiber production process are given. The balances are used: for validation of a cell modeling method that predicts the performance of different recuperator designs, and for finding a simple solution to improve the existing recuperator. Three possible solutions are analyzed: to use the existing recuperator as a countercurrent one, to add an extra cylinder over the existing construction, and to make a system that consists of a central pipe and two concentric annular ducts. In the latter, two air streams flow in opposite directions, whereas air in the inner annular passage flows concurrently or countercurrently to flue gases. Compared with the concurrent recuperator, the countercurrent has only one drawback: the interface temperature is higher at the bottom. The advantages are: lower interface temperature at the top where the material is under maximal load, higher efficiency, and smaller pressure drop. Both concurrent and countercurrent double pipe-in-pipe systems are only slightly more efficient than pure concurrent and countercurrent recuperators, respectively. Their advantages are smaller interface temperatures whereas the disadvantages are their costs and pressure drops. To implement these solutions, the average velocities should be: for flue gas around 5 m/s, for air in the first passage less than 2 m/s, and for air in the second passage more than 25 m/s.

Optimization of Secondary Cooling on Rectangular Bloom Based on Subproblem Approximation Method

For understanding the surface and internal defects of Q195 steel of 150mm×220mm rectangular bloom, a solidification heat transfer mathematics model based on temperature measuring is established. Meanwhile, the secondary cooling water is optimized according to the metallurgical criteria by means of subproblem approximation method. The results showed that: after the optimizing result is applied in actual production, the water consumption is reduced 8.2~11.5%, the quality of bloom improved obviously, and the defects such as central pipe, center porosity and internal cracks are reduced respectively.

Analysis of the Influence of Mini-Pipes Diameter in the Performance of a Non-Conventional Rotary Dryer

Conventional rotary dryers are used in many industrial sectors. The present work analyzes the drying of granulated fertilizers in a non-conventional dryer. The major characteristic of this new dryer is the presence of an aerated system consisting of a central pipe from which a series of mini-pipes conduct the hot air directly to the particle bed that is flowing at the bottom. This work has tested several diameters of mini pipes and the better experimental results were obtained with mini pipes of 9 mm.