Parent Tube Research Articles

Scaling laws for optimized power-law fluid flow in self-similar tree-like branching networks

The power-law fluid flow in tree-like self-similar branching networks is prevalent throughout the natural world and also finds numerous applications in technology such as oil recovery and microfluidic devices. We investigate analysis of optimal power-law fluid flow conditions and the optimal structures within tree-like branching networks, focusing on maximizing flow conductance under the constraint of the network tube’s volume and the surface area. The study considered fully developed laminar power-law fluid flow regimes without considering any losses in the network system. A key observation was the sensitivity of the dimensionless effective flow conductance to the network’s geometrical parameters. We found that the maximum flow conductance occurs when a dimensionless radius ratio β∗ satisfies the equation β∗=N−1/3 and β∗=N−(n+1)/(3n+2) under constrained tube-volume and surface-area, respectively. Here, N represents the bifurcation number of branches splitting at each junction, and n is the fluid power-law index. We further find that this optimal condition occurs when pressure drops are equipartition across each branching level. We validated our results with various experimental results and theories under limiting conditions. Further, Hess–Murray’s law is justified and extended for the shear-thinning and shear-thickening fluid flows for an arbitrary number of branches N. Further, in this study, we also derive the relationships between the geometrical and flow characteristics of the parent and daughter tubes as well as the generalized scaling laws at the optimal conditions for the other essential parameters such as tube-wall stresses, length ratios, mean velocities, tube-volume, and surface-area of the tube distributing within the networks. We find that the fluid power-law index n does not influence the constrained tube-volume scaling at the optimal conditions; however, the scaling laws vary with n under the constrained tube’s surface area. These findings offer valuable design principles for developing efficient transport and flow systems.

An Introduction to Diopatra, the Amazing Ecosystem Engineering Polychaete.

The annelid genus Diopatra occurs in all major oceans but is best represented in the shallow depths of warmer waters, where it lives in elaborately decorated tubes. This paper provides an introduction to the animals, discussing their history and diversity. We describe and illustrate its morphology and geographic distribution. While they were thought to be predominantly gonochoristic, recent reproductive studies show that several species are protandric simultaneous hermaphrodites. Development is by broadcast spawning with a brief pelagic stage or direct development in the parental tube or egg mass attached to it. Diopatra is a key ecosystem engineer, altering water flow and deposition and increasing the availability of refugia. We also discuss its harvesting as fishing bait, its role as an alien or introduced species, its capacity to regenerate, its therapeutic potential, and its applications as a bioindicator species for climate change, geographic distribution changes, and dispersal.

Identification of Anisotropic Coefficients in the Non-Principal Axis Directions of Tubular Materials Using Hole Bulging Test.

We propose an experimental method to identify anisotropic coefficients in non-principal axis directions of thin-walled tubes. The method involves extracting specimens from the parent tubes and machining a hole in the axial center. The specimens are then inserted into a tube without a hole. The inner diameter of the specimen is theoretically equal to the outer diameter of the inner tube. The double-layer tube undergoes free bulging under internal pressure in our self-developed experimental equipment, with the hole on the specimen expanding simultaneously. The stress states around the hole are uniaxial, and the hole deformation can reflect the anisotropic plastic flow characteristics of the tube. Furthermore, based on the information obtained from the proposed experimental method, a hybrid numerical-experimental method was used to identify the anisotropic coefficients of tubes. Through FE simulations, the relationships between the thickness, stress, and strain states around the hole, the hole shape, and anisotropic coefficients of non-principal axis directions are revealed, and the factors that affect the hole deformation are analyzed. Finally, the hole bulging experiments and FE simulations of AA6061-O extruded tube were conducted, and modeled with Hill48 and calibrated by uniaxial tensile and hoop tensile tests. Its in-plane anisotropy coefficients in any direction are given for the first time which first increase and then decrease from 0° to 90°, reaching a maximum of 1.13 in 60° and a minimum of 0.69 in 0°. This work can provide the key experimental data for establishing an accurate anisotropic plastic constitutive model of thin-walled tubes.

The oldest mineralized bryozoan? A possible palaeostomate in the lower Cambrian of Nevada, USA.

All skeletal marine invertebrate phyla appeared during the Cambrian explosion, except for Bryozoa with mineralized skeletons, which first appear in the Early Ordovician. However, the skeletal diversity of Early Ordovician bryozoans suggests a preceding interval of diversification. We report a possible earliest occurrence of palaeostomate bryozoans in limestones of the Cambrian Age 4 Harkless Formation, western United States. Following recent interpretations of the early Cambrian Protomelission as a soft-bodied bryozoan, our findings add to the evidence of early Cambrian roots for the Bryozoa. The Harkless fossils resemble some esthonioporate and cystoporate bryozoans, showing a radiating pattern of densely packed tubes of the same diameter and cross-sectional shape. Further, they show partitioning of new individuals from parent tubes through the formation of a separate wall, a characteristic of interzooecial budding in bryozoans. If confirmed as bryozoans, these fossils would push back the appearance of mineralized skeletons in this phylum by ~30 million years and impact interpretations of their evolution.

Interference-fit joining of Cu-SS composite tubes by electromagnetic crimping for different surface profiles

This paper explores the possibility of producing an improved interference-fit tubular joint between pure copper and stainless steel tube by electromagnetic crimping (EMC). Successful joints are obtained with optimal parameters consisting of the outer surface profile of the inner tube and discharge energy. Joints exceeding the strength of the parent tube are formed without any metallic bond formation. Three destructive testings, namely, pull-out, compression and torsion tests, have confirmed the successful joint formation as the failure occurs in the copper base tube. Analysis of failure mechanisms has revealed joint behaviour at various discharge energies and surface profiles. Among smooth, knurled and threaded surface profiles with different discharge energy levels, knurled surface provides best joint strength at 6.2 kJ, which has shown a failure in the parent Cu tube during all three destructive testings. Radial deformation of the tubes is measured and compared for different discharge energy and surface profile. No metallic bond formation and the wavy interface are observed between the joining partners during microstructural analysis. Furthermore, no elemental overlapping is observed during energy dispersive spectroscopy mapping analysis indicating an absence of diffusion. Higher micro-hardness is observed near the Cu-SS tubular joint interface due to strain hardening caused by high-velocity impact.

Microstructural characterization of cold-worked 316 stainless steel flux thimble tubes irradiated up to 100 dpa in a commercial Pressurized Water Reactor

Two flux thimble tubes (FTTs) made of 15% cold-worked 316 stainless steel (SS) were harvested from Ringhals Pressurized Water Reactor (PWR) Unit 2, with peak damages of 76 and 100 displacements per atom (dpa) after 29 and 34 years’ service, respectively. Specimens sectioned from parent tubes were comprehensively characterized with nominal damage levels of ∼0, ∼41, ∼74, 76, and 100 dpa at a nominal temperature range of 285–323 °C. Both FTTs contained helium and hydrogen gases as transmutation products. The helium follows a production rate of ∼9.8 appm/dpa, while environmental factors complicate hydrogen production obscuring an exact H/dpa ratio. Irradiation-induced dislocation loops, nano-cavities, solute clusters, and microsegregation were all observed. The dislocation loops and nano-cavities indicated saturation at 41 dpa. The solute clusters continued to evolve with Ni–Si clusters formed at 41 dpa, and Ni–Si–Mn–P clusters formed at 74 and 100 dpa, but neither clusters exhibited distinct diffraction patterns at any damage levels. Solute clusters were observed to frequently be co-located with dislocation loops, but fully decorated loops were rarely detected. Significant radiation-induced segregation (RIS) was observed around grain boundaries at all damage levels. The modified inverse Kirkendall (MIK) model captured the RIS behavior of major elements. Large cavities within or around an Mn–S rich region were observed for the first time. Through all the damage levels, void swelling is always below 0.05%, making significant dimensional change unlikely in core internals when used at similar conditions. Meanwhile, the role of overwhelming nanocavities, presumably helium bubbles, should be considered in other potential degradation mechanisms, including irradiation-assisted stress corrosion cracking, embrittlement, and loss of fracture toughness, which remain the concerns for extended operation of nuclear power plants.

Friction Stir Processing of AA6063-T6 Tubes and End Forming Characterization at Varying Tool Pin Profiles

The effect of tool pin profiles on the end forming performance of friction stir processed (FSPed) Al6063-T6 tubes has been studied. FSP is done in the longitudinal direction of the tube. Straight cylindrical pin, tapered cylindrical pin, and stepped cylindrical pin (STP) are selected. End expansion, end reduction, and end beading experiments are conducted. The load-displacement curve and instabilities are evaluated and predicted by finite element simulations and the strain mapping method. The STP generates better ductility and a better strain hardening exponent because of the reduction in dislocation density in the stir zone. This has a considerable effect on load requirement and displacement at failure during end expansion and end beading, whereas it has an insignificant effect during end reduction. The hardness index of FSPed tubes improves during end forming because of strain hardening, which is appropriate for structural applications in industries. FSPed tubes perform equal to that of parent tubes in terms of energy absorption during end beading and end reduction, whereas it is not so in end expansion, highlighting the applicability of FSPed tubes for tube beading and reduction applications. Instabilities in the form of longitudinal crack, wrinkling, and overlap are observed. The predicted instability results agree well with experimental data during end reduction and end beading, and they have reasonable agreement during end expansion.

Towards Methodologies for Optimal Fluid Networks Design

Tree flow networks are ubiquitous in nature and abound in engineered systems. A parent tube branching into two daughter tubes is the main building block of these networks. These branched tubes should be designed to provide easier access to flow under different size constraints. Optimal tree networks follow a homothetic scaling where the sizes of tubes have the same ratios between successive generations. In this study, different approaches aiming at optimal design of bifurcating tubes are presented and compared. The cross-sectional area of the tubes is obtained using two methods, based on Lagrange multipliers with a size constraint to respect, and including the size limitations directly into the function to optimize via chain rule. The optimal length of the tubes is obtained based both on the equipartition of forces/resistances and on the equal thermodynamic distance. These methods can be understood as a way of connecting entropy generation and the size of branching tubes. This study shows that applying the Lagrange Multiplier Method and applying the chain rule with constraint provides the same result. A similar result is obtained when the equipartition of forces/resistances and equal thermodynamic distance design methods are applied. These results are valid for different size constraints. In summary, our paper provides a comprehensive comparison of the different methods for a better choice, and is intended to provide insights into tree networks of tubes of any shape under different size constraints, for design and analysis.

Residual stress analyses in multilayer PP/GFP/PP composite tube

The present paper is a contribution in analysing residual stress in multilayer composite tube used for conveying drinking water. The tube is made of three layers spread in one-fourth outer polypropylene layer, one-half central glass-fibre-polypropylene layer, and one-fourth inner polypropylene layer. The contribution of each layer involved in forming the composite tube has been shown through the improvement of yield stress by 80%. Residual stresses have been measured using the Crampton technique and layer removal method. In the parent tube, negative residual stress is obtained for a ratio of tube length to tube diameter L/D0 ≥ 1.4, with a magnitude of 91% significant comparing with the yield stress of the material. The distribution of the residual stress through the wall of the tube has followed a sigmoid curve that is characterised by a three-order polynomial engineering model showing negative stresses at the outer surface and positive stresses at the inner surface. The observation suggests that compressive residual stresses act through 80% of the wall thickness of the tube. Hence, the presence of the central GFP layer permits to equilibrate the distribution of the stresses during the service life of the tube. The residual stress distribution is in good agreement with the evolution of mechanical absorbed energy per unit volume material according to its location within the parent tube. For an equivalent pipe in diameter and thickness, the residual stress in composite pipe is ten times higher than that in PE pipe.

Asexual reproduction of tubular fossils in the terminal Neoproterozoic Dengying Formation, South China

Tubular fossils are an abundant and diverse component of late Ediacaran benthic communities. However, with rare exceptions, their development and modes of asexualreproduction remain poorly resolved. With the deeper research and more specimens recovered, the types of asexual reproduction of tubular fossils are clarified. Three-dimensionally phosphatized tubes from the Ediacaran Dengying Formation in Lijiagou (southern Shaanxi Province, China) provide a window into the reproduction of late Ediacaran tubular fossils. In this paper, we document two different styles of asexual reproduction associated with two morphotypes of the biomineralized tubular fossil and propose upper Ediacaran index fossil Cloudina (type A with bud from the aperture of parent tube and type B with new bud from the lateral of parent tube, type C with two similar diameter individual tubes) and the new genus Multiconotubus (type E and type F with individual tubes but living in the parent tube). What is the most important is that based on the internal structure of dichotomous Multiconotubus, and observing means of x-ray micro-tomography, we can see clearly the internal structure and we propose a new growth strategy for this organism. In this paper, we emphasize the asexual budding reproduction and the multiple common wall reproduction.

Two new species of Mooreonuphis (Annelida: Onuphidae) from Australia.

Two new species of Mooreonuphis, a genus best known from the coasts of the Americas, are described from Australia, bringing the number of recognized Mooreonuphis species to 23. Mooreonuphis ariasi n. sp. was collected from off Sydney to Wollongong, New South Wales in sandy sediments, in depths of 25-50 m and M. wilsoni n. sp. in the Bass Strait and Tasmania, in 89-130 m. The two new Australian species are among the smallest and the only known abranchiate species in the genus. The summer collections of M. ariasi n. sp. contained a large number of brooders with their young undergoing asynchronous direct development in the parental tube. Nothing is known about the development of M. wilsoni n. sp.

Failure evaluation of SA 210C riffle water wall tubes in 70 MW CFBC boiler

Abstract Boiler tubes used as water walls made up of ferritic steels is having some finite life, because of prolonged exposure in the furnace at elevated temperature, stress and aggressive environment, tube failure taking place. Now a day's premature failure of the boiler tube mainly in water walls is one of the very common phenomena in the thermal power plants. The present investigation was done on the as-received ASTM SA 210C failed boiler tube steel used as water walls in the Circulating Fluidized Bed Combustion (CFBC) coal fired thermal power plant. An attempt has been made to understand the cause, because identifying correct failure mechanism often helps to perform meaningful life assessment and also to prevent the future Boiler Tube Failure (BTF). The as-received of failed tube along with the parent (unused) tube from the water wall raiser panel were selected to study for mechanical and metallurgical properties. Tensile test and micro hardness examinations were carried out on both the parent tube and failed tube. Visual examination reveals “fish-mouth” appearance of the as-received failed tube because of short-term overheating. The micro structure of the parent metal has the conventional structure of ferrite (white constituent) and pearlite (dark constituent), whereas for the as- received failed tube reveals Widmanstatten ferrite. A detailed structure - property relationship has been made by using the combined techniques of Optical Microscopy (OM), SEM/EDAX and XRD. Tensile fractography depicts the presence of micro-voids coalescence in the fibrous network shows ductile mode failure in the as-received failed boiler tubes.

Constructal branching design for fluid flow and heat transfer

Our focus is space-filling networks to deliver and distribute flows. Here we report an analytical analysis of optimal branching networks of tubes for both fluid flow and heat transfer. This attempt results in the structural features of these networks, mainly on relationships between the size of the parent and daughter tubes at bifurcations, and the branching angles of the bifurcations. The process of construction of these networks is described for both laminar and turbulent flow, Newtonian and power-law fluids, and constant and pulsatile flows. The extended design rules obtained in this study are compared with the optimal branching rules available in the literature. Structural features of bifurcating tubes under different flow regimes are also analyzed.

Pressure Model for Capillary Tree-Shaped Fractal Networks

Capillary tree networks can be efficiently used for several applications. These trees display the same patterns at different levels of scale, which is a property found in fractal objects. This paper combines a thermodynamic formulation with the geometric characteristics of the tree fractal network, to describe the equilibrium capillary pressure. The model proposed here accounts for, in addition to physical properties of the fluids, the fractal dimension, the scale factor between the size of parent and daughter tubes, and the branching level. The effect of each of these properties on the capillary pressure is also investigated.

End forming behaviour of friction stir processed Al 6063-T6 tubes at different tool rotational speeds

The main aim of this work is to study the end forming behaviour of friction stir processed Al 6063-T6 tubes fabricated at different tool rotational speeds. Tube expansion, tube reduction and tube beading are performed on the friction stir processed and parent tubes. The load, thinning and hardness evolution during the end forming operations are evaluated. A rotational speed yielding moderate combination of initial hardness and hardening index of the friction stir processed zone governs the maximum load required during end forming. Tube reduction and tube beading need larger load because of tube thickening, as compared to tube expansion, in which tube thinning is witnessed. The friction stir processed zone of the processed tube undergoes larger thinning and thickening as compared to base material in tube expansion and reduction, respectively, while base material thickens more in tube beading. The hardness and strain hardening exponent difference govern such thickness evolution. Mechanical instabilities like failure of friction stir processed zone, wrinkling and overlapping of friction stir processed zone, and fine cracks development are seen during the end forming operations. The effect of rotational speed on the hardness and grain size distribution of friction stir processed zone is negligible. The hardness of processed zone is found to increase after end forming operations.

The social feather duster worm Bispira brunnea (Polychaeta: Sabellidae): aggregations, morphology and reproduction

ABSTRACTThe fan worm Bispira brunnea is one of the most attractive sabellid polychaetes from Caribbean coral reef areas and it is exploited for ornamental purposes. An understanding of the structure of its aggregations, morphology and reproductive biology will provide information required to facilitate artificial propagation of this species. Ten aggregations were collected in October 2013, February and March 2014 in the Majahual reef lagoon, Mexican Caribbean. Whole aggregations were examined under light microscopy and scanning electron microscopy and the histology of oogenesis was determined. Aggregations were composed of 24–56 individuals and included juveniles and adults. The adults (5–20 mm) did not display any noticeable form of sexual dimorphism. In B. brunnea both sexual (hermaphroditism or gonochorism) and asexual reproduction occurred at the same time within the population: 92.71% reproduced sexually and 52% by architomy. The buds produced by architomy were inside the parental tube, at three regenerative stages. The sex ratio was 36.75% males, 33.11% females, 22.84% hermaphrodites and 7.28% unknown (gametes not seen). Gametes were distributed in the last thoracic segments and throughout the abdomen. Oogenesis was extra-ovarian, development followed four discrete stages and the oocytes were small and asynchronous (60.97 μm in diameter). Sperm morphology was adapted to external fertilization in the water column. Sequential (protandrous) hermaphroditism is suggested to occur in B. brunnea. The pyramidellid ectosymbiont mollusc Odostomia (Eulimastoma) caniculatum is recorded here for the first time as being associated with a sabellid worm.

The Eating and Drinking Ability Classification System in a population-based sample of preschool children with cerebral palsy.

To determine (1) the reproducibility of the Eating and Drinking Ability Classification System (EDACS); (2) EDACS classification distribution in a population-based cohort with cerebral palsy (CP); and (3) the relationships between the EDACS and clinical mealtime assessment, other classifications, and health outcomes. This was a cross-sectional population-based cohort study of 170 children with CP at 3 years to 5 years (mean 57.6mo, standard deviation [SD] 8.3mo; 105 males, n=65 females). Functional abilities were representative of a population sample (Gross Motor Function Classification System level I=74, II=34, III=21, IV=18, V=23). The EDACS was the primary classification of mealtime function. The Dysphagia Disorders Survey was the clinical mealtime assessment. Gross motor function was classified using the Gross Motor Function Classification System. EDACS classification had 88.3% intrarater agreement (κ=0.84, intraclass correlation coefficient=0.95; p<0.001) and 51.7% interrater agreement (κ=0.36, intraclass correlation coefficient=0.79; p<0.001). In total, 56.5% of children were classified as EDACS level I. There was a strong stepwise relationship between the Dysphagia Disorders Survey and EDACS (r=0.96, p<0.001). Parental stress (odds ratio=1.3, p=0.05) and feeding tubes (odds ratio=6.4, p<0.001) were significantly related to more limited function on the EDACS. The EDACS presents a viable adjunct to clinical assessment of feeding skills in children with CP for use in surveillance trials and clinical practice. A rating addendum would be a useful contribution to the tool to enhance reproducibility.

Design of high field tool coil for magnetic pulse welding

The Accelerator and Pulse Power Division (APPD), BARC has developed strong Bitter coil with field shaper and 70 kJ, 25 kV electromagnetic manufacturing machine, for forming and welding applications. They conducted investigations into possibility of using Electromagnetic Pulsed Technology (EMPT) in joining austenitic –austenitic stainless steels, using samples fabricated to simulate tube and caps with coil developed at laboratory. The coil has been designed for industrial mass production that consists of four numbers of copper discs axially reinforced with non-magnetic steel studs. The polyamide films are used as coil and stud liner whereas Fibre Reinforced Plastic (FRP) is used as inter disc insulation. This paper discusses the design details of the 20kV, 250kA, 10 kHz Bitter coil, field shaper with replaceable inserts. This designed coil has been regularly used at rated value and generating the field of 35-40T in volume of O8.8mmX13mm. The steel tube to plug joints developed by this tool qualified helium leak better than 1.2x10 -9 mBar.litre.s -1 and parent tube failed under pull out test but joint was intact.

Optimal Branching Structure of Fluidic Networks with Permeable Walls.

Biological and engineering studies of Hess-Murray's law are focused on assemblies of tubes with impermeable walls. Blood vessels and airways have permeable walls to allow the exchange of fluid and other dissolved substances with tissues. Should Hess-Murray's law hold for bifurcating systems in which the walls of the vessels are permeable to fluid? This paper investigates the fluid flow in a porous-walled T-shaped assembly of vessels. Fluid flow in this branching flow structure is studied numerically to predict the configuration that provides greater access to the flow. Our findings indicate, among other results, that an asymmetric flow (i.e., breaking the symmetry of the flow distribution) may occur in this symmetrical dichotomous system. To derive expressions for the optimum branching sizes, the hydraulic resistance of the branched system is computed. Here we show the T-shaped assembly of vessels is only conforming to Hess-Murray's law optimum as long as they have impervious walls. Findings also indicate that the optimum relationship between the sizes of parent and daughter tubes depends on the wall permeability of the assembled tubes. Our results agree with analytical results obtained from a variety of sources and provide new insights into the dynamics within the assembly of vessels.

Investigation of intergeneric crossability of Vicia faba L. and Thermopsis turcica Kit Tan, Vural et Küçüködük

An unilocular ovary is often observed in the Fabaceae family. Thermopsis turcica Kit Tan, Vural et Kucukoduk is an endemic, rare plant species in Turkey that is distinguished by its multi-carpellary apocarpous ovaries. No research has been conducted on the crossing of T. turcica with other species to date. Vicia faba L. (fababean) (2n = 12), which is one of the oldest crops used for human and animal consumption, and Thermopsis turcica (2n = 18) were selected to explore the possibility of increasing yield in edible crops by intergeneric crossing. When T. turcica was used as a male parent, pollen germination and pollen tube growth appeared to be normal and globular embryo formation was observed, but hybrid seeds aborted due to post-fertilization barriers. In contrast, in all crosses in which T. turcica was used as a maternal parent, an embryo was not obtained, and viability of the pistil did not exceed 10 days after pollination. Also, in the samples left to free pollination, pistils died in a few days after anthers were removed just before pre-anthesis. Inability to obtain viable seeds by hybridization of Vicia faba and T. turcica should not be considered as a demonstration of complete incompatibility of the species in intergeneric crosses. The present report constitutes the first study on this issue.