Tubes

: This research aims to develop, analyze, and evaluate a new type of structural element that will enhance the crashworthiness of naval vehicles by providing outstanding energy absorption with minimal weight. The structural element is an array of concentric fiber reinforced composite tubes with extension-twist coupling and ultra-high Poisson's ratio. The tubes are configured to crush or shear internal foam as a means of absorbing energy. This interim report includes technical progress, plans, publications, and various administrative matters. In the current period, work has focused on evaluating the mechanisms of energy absorption in composite tubular structures and the development of analytical models for predicting the deformation and damage in these tubular structures. A significant effort was dedicated towards developing the manufacturing and testing technology for tubes having extension-twist coupling. This effort culminated in the successful demonstration, for the first time...

Failure investigation was carried out on a refinery steam boiler that had a history of good performance with few leakages and damages that were successfully weld repaired. The steam boiler tubes were observed to have developed several perforations / punctures on numerous furnace chamber tubes, twenty two years after commissioning. In the course of the investigation, background data and history of failure were collected with available photographic evidences, visual examination, low magnification examination, chemical analysis, SEM analysis, EDS analysis, macrostructure examination, microstructure examination, tensile test hardness and micro-hardness tests. It was concluded that the failure of the tubes were due to upsets in the water chemistry that has promoted caustic gouging from ID at localized places. Adjustments to boiler water chemistry which should be made to maintain strict congruent phosphate pH control was then recommended.

Fiber reinforced polymer (FRP) tubes are an attractive form of concrete confinement, where the tubes can fulfill multiple functions of: (i) formwork, (ii) confinement reinforcement, (iii) protective shell against corrosion, weathering, and chemical attacks. This paper reports on the development and testing of a new type of rectangular FRP tube that is designed to improve the inherently low confinement effectiveness of rectangular FRP tubes. Axial compression tests were conducted to investigate confinement effectiveness of rectangular tubes with various arrangements. The tubes were designed as column confinement reinforcement and were manufactured using unidirectional carbon fiber sheets. The effects of the tube corner radius and the presence of internal FRP reinforcement were investigated experimentally. The results of the experimental investigation indicate that confinement of rectangular columns with FRP tubes leads to substantial improvement in the ductility of the columns. Confinement provided by the FRP tube may also improve the axial load-carrying capacity of the rectangular columns if the confinement effectiveness of the FRP tube is sufficiently high. The results also indicate that the FRP tube developed by the authors and presented in this study provides significantly higher confinement effectiveness than that of conventional rectangular FRP tubes.

Measurements and numerical modeling are applied to observe and predict the interactive influence of sub-micron gas borne particles in an erosive turbulent combustion wall boundary layer. Some of the experiments and computations discussed are directed to study of turbulent free shear layers. Others ephasize wall boundary layers. The common purpose of all of these studies is to generate information on the particle interaction mechanisms active in alteration and reduction of the turbulent transport and the consequent reduction of the erosive heat and mass transfer. Primary emphasis here is given to analysis of erosive two phase wall boundary layers encountered in solid propellant combustion situations. Examples are gun barrel, rocket nozzle, and coal-fired gas turbine combustion flow fields.

The peristaltic mechanism of a Jeffrey fluid in a circular tube is investigated. The rheological effects and compressibility of the fluid are taken into account. The modeled equations are solved using perturbation technique when the ratio of the wave amplitude to the radius of the pore is small. In the second order approximation, a net flow due to a travelling wave is obtained and effects of Reynolds number, relaxation and retardation times, compressibility of the fluid and tube radius are studied. It is noticed that for the Jeffrey fluid the back flow only occurs for large values of the relaxation time and small values of the retardation time (less than 10 in the present analysis). Another interesting observation is that oscillatory behavior of the net flow rate in the Jeffrey fluid is less than that of a Maxwell fluid. Several results of other fluid models can be deduced as the limiting cases of our situation.

This study aimed to evaluate the start-up and the adaptation of an anaerobic horizontal-flow immobilized biomass (HAIB) reactor in order to treat wastewater from a primary processing of coffee fruits. The reactor was built with PVC tubes of 0.2 m in diameter and 3.2 m in length. The system was filled with cubes of polyurethane foam for immobilization of active biomass. The reactor presented a total capacity of 0.1 m3 and reaction volume equal to 0.04 m3. 49% of organic matter. Removal efficiency was observed, with medium organic volumetric loads equal to 2.66 kg m-3 d-1 (as chemical oxygen demand). The supplementary addition of alkalinity and the previous biomass inoculation provided a stable start-up of the reactor, as confirmed by the reduction of volatile acids and an adaptation of the present microbiology community. The systems showed resistance to changes in flow and in the organic load observed; the levels of phenol and potassium monitored did not cause inhibition of the biological activity. A better control on the changes in load rates is an important topic for the next studies.

Peristaltic flow of a third grade fluid in a circular cylindrical tube is undertaken when the no-slip condition at the tube wall is no longer valid. The governing nonlinear equation together with nonlinear boundary conditions is solved analytically by means of the perturbation method for small values of the non-Newtonian parameter, the Debroah number. A numerical solution is also obtained for which no restriction is imposed on the non-Newtonian parameter involved in the governing equation and the boundary conditions. A comparison of the series solution and the numerical solution is presented. Furthermore, the effects of slip and non-Newtonian parameters on the axial velocity and stream function are discussed in detail. The salient features of pumping and trapping are discussed with particular focus on the effects of slip and non-Newtonian parameters. It is observed that an increase in the slip parameter decreases the peristaltic pumping rate for a given pressure rise. On the contrar...

Abstract: Cruise PGC00-003 was a collaborative experiment between the University of Victoria, the Geological Survey of Canada, and the Naval Re-search Laboratory. The program focused on seafloor vents that may be sites of significant fluid and methane flux. ...