Slender Tube Research Articles

Elasto-capillary circumferential buckling of soft tubes under axial loading: existence and competition with localised beading and periodic axial modes

We provide an extension to previous analysis of the localised beading instability of soft slender tubes under surface tension and axial stretching. The primary questions pondered here are as follows: under what loading conditions, if any, can bifurcation into circumferential buckling modes occur, and do such solutions dominate localisation and periodic axial modes? Three distinct boundary conditions are considered: in case 1 the tube’s curved surfaces are traction-free and under surface tension, whilst in cases 2 and 3 the inner and outer surfaces (respectively) are fixed to prevent radial displacement and surface tension. A linear bifurcation analysis is conducted to determine numerically the existence of circumferential mode solutions. In case 1 we focus on the tensile stress regime given the preference of slender compressed tubes towards Euler buckling over axisymmetric periodic wrinkling. We show that tubes under several loading paths are highly sensitive to circumferential modes; in contrast, localised and periodic axial modes are absent, suggesting that the circumferential buckling is dominant by default. In case 2, circumferential mode solutions are associated with negative surface tension values and thus are physically implausible. Circumferential buckling solutions are shown to exist in case 3 for tensile and compressive axial loads, and we demonstrate for multiple loading scenarios their dominance over localisation and periodic axial modes within specific parameter regimes.

Analysis of the turbulent flow patterns generated in isotropic porous media composed of aligned or centered cylinders

The analysis of the turbulent flow inside porous media composed of infinite arrangements of cylinders with square and circular cross sections disposed in aligned or centered configuration is presented. The porosity (ϕ) was varied from 0.3 to 0.8, at a pore Reynolds number Rep=105, representing fully turbulent flow conditions. The flow cases were solved numerically by using the low-Reynolds Abe-Kondoh-Nagano version of the k-ε model. New correlations are provided for the domains composed of aligned particles in terms of ϕ for the volume averaged turbulence kinetic energy (k), its dissipation rate (ε), and macroscopic pressure gradient (MPG). These correlations are especially useful when it is not possible to model the local details of the porous media in macroscopic turbulence modeling. The highest energetic losses in terms of volume averaged k, ε, and MPG was found for the centered square arrangement. In all cases, these parameters increased abruptly as ϕ decreased, as the pore-scale local pressure gradients and turbulent kinetic energy dissipation rate levels increased. Depending on the case, they were triggered by a combination of sudden expansion-contraction of the flow channels, flow impingement, and the decrease of the effective flow area by flow recirculation. In all cases, the pore-scale local pressure gradients and turbulent kinetic energy dissipation rate levels increased abruptly as ϕ decreased, and consequently the energy losses increased. The tracer dispersion presented similar low homogeneity times for the centered cylinder arrangements. At each porous media, the variations of turbulence intensity, effective flow area, and tortuosity levels in terms of ϕ were not as significant as those observed for the local pressure gradient and dissipation rate. This effect may be considered to improve mixing and reduce pressure drops in devices such as static mixers, heat exchangers, cooling fins arrays, and other devices composed of slender tubes.

An improved heat transfer model for steam-air mixture condensation with the curvature effect on vertical tubes

The condensation heat transfer on the external surface of a vertical slender tube in the steam-air mixture environment was investigated. The condensation heat transfer was analyzed using various open experimental datasets. A new model for the steam condensation with noncondensable gases applicable to the tubular configuration was developed. The proposed model is based on the analogy between heat and mass transfer; in particular, the correlation incorporates the effects of tube curvature under turbulent free convection conditions together with the wavy film effect. In addition, the film-vapor interfacial temperature was used to calculate the heat transfer coefficient and various physical properties, through an iterative technique instead of the wall temperature, which is commonly used in experimental correlations for convenience. Thereafter, the effects of three correction factors were individually investigated. The wavy film effect considerably changed the condensation heat transfer, about 20% on average. The curvature effect was also found to make a meaningful effect according to the convection conditions. And, the adoption of interfacial temperature was found to make a maximum 7% adjustment, but it would make a more significant effect in high heat transfer conditions. Overall, the proposed model predicted the experimental datasets reasonably well, i.e., within ±30% accuracy.

Ecological distribution and soil-vegetation analysis of the indigenous vegetable panawil (Leptosolena haenkei C. Presl.) in specific areas of Benguet and Mountain Province, Philippines

One plant that is indigenous to the Cordillera Region is an herb locally known as panawil (Leptosolena haenkei C. Presl.). It is known as the most distinct in Zingiberaceae Family because of its large flowers with extremely long and slender corolla tube extended from the calyx. The flowers are gathered for consumption during the boot stages before the plant fully blooms. The study was conducted to identify the distribution of panawil in its ecological habitat, assess the abundance and frequency, and analyze the soil chemical properties under different elevations. The study disclosed that panawil thrives at an altitudinal range of 600–1200 m above sea level. Growing in clusters along its natural habitat such as near agroecosystems, river banks, grasslands, and pine forest ecosystems. The soil-vegetation analysis revealed the importance value (IV) of panawil ranked fourth (17.97) in the lower altitude and ranked fifth (15.61) in the upper altitude among its associated plant species growing in the same location. Soil analysis showed that both in Benguet and Mountain Province, the soil chemical properties such as phosphorus (20 ppm), soil organic matter (6 ppm), and pH (6.79) are generally higher in the lower altitude as compared to the upper altitude.

Acoustic Tamm states in slender tubes

We present an analytical and numerical study of the possibility of existence of surface localized modes, the so-called Tamm states, in a one-dimensional (1D) comb-like phononic crystal (PnC). The structure is made out of periodic array of stubs of lengths d2 grafted along a waveguide and separated from each other by a tube of length d1. We show the existence of surface modes for the semi-infinite structure. In particular, when one considers two complementary semi-infinite systems obtained by cutting the infinite one into two parts, we obtain one surface mode per gap induced by the surface of the two complementary systems. Furthermore, we demonstrate that these surface modes can be detected from the maxima and minima of the transmission spectrum, when the finite structure is grafted vertically along a homogeneous acoustic waveguide. That means that one can observe experimentally this type of modes for acoustic waves in slender tubes. These results may find many practical applications in noise control and highly sensitive PnC sensors.

Overall buckling characteristics of slender FRP-foam sandwich tube under axial compression

Compared with laminated FRP (Fiber Reinforced Plastic) tube, FRP-foam sandwich tube can improve the stability of the member and better exert the high strength of FRP. It can be used in civil engineering as compression member with lightweight, high bearing capacity and corrosion resistance. In order to study the compression characteristics of this new type of compression member, axial compression tests on the slender FRP-foam sandwich tubes were carried out compared with laminated composite tube. It was found that the main failure mode is overall buckling of this slender sandwich tube. Then the Perry-Robertson's formula based on the edge failure criterion was adopted as the basic form of the overall stability coefficient calculation formula for the sandwich tube. Afterwards the parameters of the formula were obtained based on the experimental results. As a result, the calculation equation of the overall stability coefficient for the FRP-foam sandwich tube was derived.1

The Hydrostatic Paradox Redux

A good paradox has the viewer confused, but the best paradoxes lead the viewer to try to understand what is happening. One of my favorites is the hydrostatic paradox, in which a short and slender column of water supports a relatively enormous weight. Figure 1 shows this paradox in action. In the picture a student weighing 60 pounds stands on a platform placed atop a flat water-filled rubber hot-water bottle. Connected to the bottle is a slender upright glass tube, also filled with water. A column of water only four or so feet high supports the student.

Thermal performance of a thermal management system with a thin plate and a slender tube for prismatic batteries

SummaryThe temperature of high‐power lithium‐ion batteries has a great influence on their performance, safety, and stability; thus the battery thermal management system (BTMS) is a key component of electric vehicles. In this paper, a novel liquid‐cooling BTMS with a thin plate and a slender tube is proposed for prismatic batteries, four different cooling structures of the tube are designed to achieve a high temperature uniformity, and a three‐dimensional numerical model is established. The effects of different cooling structures, battery discharge rates, coolant inlet velocities and inner diameters of the slender tube on the thermal performance are investigated. The results indicate that design S3, for which the length of the effective heat transfer tube distributed by each battery increases gradually along the flow direction of the coolant, exhibits the best thermal management performance among the four designed cooling structures, especially in terms of the temperature uniformity. When the inner diameter of the slender tube is 2 mm and the inlet velocity is not less than 0.5 m/s, the maximum temperature difference between the batteries is reduced to 4.23°C at a 2C discharge rate. This study can provide guidance for the structural design of BTMSs for prismatic batteries.

Exact solutions of bending deflection for single-walled BNNTs based on the classical Euler–Bernoulli beam theory

Abstract At the nanolevel, a classical continuum approach seems to be inapplicable to evaluate the mechanical behaviors of materials. With the introduction of scale parameter, the scale effect can be reasonably described by the modified continuum theory. For boron nitride nanotubes (BNNTs), the scale effect can be reflected by the curvature and the dangling bonds at both ends, mainly the former for a slender tube. This study aims to achieve a good capability of classical Euler–Bernoulli theory to directly predict the bending behaviors of single-walled BNNTs without introducing scale parameters. Elastic properties of BNNTs involving the scale effect have been first conducted by using an atomistic-continuum multiscale approach, which is directly constructed based on the atomic force field. The well-determined hexagonal boron nitride sheet is inherited in the present study of single-walled BNNTs which can be viewed as rolling up a boron nitride sheet into a seamless hollow cylinder. Euler–Bernoulli theory solution of bending deflection on the basis of the present thickness is found to be much closer to the atomistic-continuum simulation results than the commonly used interlayer space. Case studies with different tubular lengths, radii and constraints are investigated, and from which the yielded scattered scale parameters in modified continuum theories are discussed.

Description of a new genus and species (Eutardigrada: Richtersiidae) from Colombia, with comments on the family Richtersiidae.

The new genus of the macrobiotoid family Richtersiidae Guidetti, Rebecchi, Bertolani, Jönsson, Kristensen Cesari, 2016 Crenubiotus gen. nov. is described, based on Crenubiotus crenulatus comb. nov. (Richters, 1904a) and on Colombian specimens formerly attributed to Macrobiotus cf. crenulatus and here described, after re-examination, as Crenubiotus revelator sp. nov. The new genus is characterised by an additional ventral thickening on the anterior portion of the ventral lamina, dorsal apophysis absent or very reduced, modified stylet furcae, claws equal in structure to those of Richtersius Pilato Binda, 1989, and very probably also Adorybiotus Maucci Ramazzotti, 1981 and Diaforobiotus Guidetti, Rebecchi, Bertolani, Jönsson, Kristensen Cesari, 2016; and, in the known species, cuticular pores, two macroplacoids, large well dentate lunules and a characteristic egg. The new species Crenubiotus revelator sp. nov. differs from Crenubiotus crenulatus comb. nov. in having smaller cuticular pores, a medio-ventral tooth in the buccal armature, more slender buccal tube, slightly more caudal stylet supports, slightly more slender claws, and in details of the egg. The description of the new genus, and new observations on Adorybiotus, Richtersius and Diaforobiotus, allowed the authors to complete the morphological scenario within the family Richtersiidae giving further support to such family.

Revisiting steady viscous flow of a generalized Newtonian fluid through a slender elastic tube using shell theory

AbstractA flow vessel with an elastic wall can deform significantly due to viscous fluid flow within it, even at vanishing Reynolds number (no fluid inertia). Deformation leads to an enhancement of throughput due to the change in cross‐sectional area. The latter gives rise to a non‐constant pressure gradient in the flow‐wise direction and, hence, to a nonlinear flow rate–pressure drop relation (unlike the Hagen–Poiseuille law for a rigid tube). Many biofluids are non‐Newtonian, and are well approximated by generalized Newtonian (say, power‐law) rheological models. Consequently, we analyze the problem of steady low Reynolds number flow of a generalized Newtonian fluid through a slender elastic tube by coupling fluid lubrication theory to a structural problem posed in terms of Donnell shell theory. A perturbative approach (in the slenderness parameter) yields analytical solutions for both the flow and the deformation. Using matched asymptotics, we obtain a uniformly valid solution for the tube's radial displacement, which features both a boundary layer and a corner layer caused by localized bending near the clamped ends. In doing so, we obtain a “generalized Hagen–Poiseuille law” for soft microtubes. We benchmark the mathematical predictions against three‐dimensional two‐way coupled direct numerical simulations (DNS) of flow and deformation performed using the commercial computational engineering platform by ANSYS. The simulations show good agreement and establish the range of validity of the theory. Finally, we discuss the implications of the theory on the problem of the flow‐induced deformation of a blood vessel, which is featured in some textbooks.

Second-order analysis of lattice booms considering restraint from the web members

Lattice booms, used in mobile cranes, are welded using slender high-strength steel tubes, and their carrying capacity is determined through the local stability of the chords. However, of the two methods for calculating it, the overall stability formula of axially compressed members is too conservative, and geometrically nonlinear analysis with imperfections is too complicated to apply. To achieve a more accurate and simple calculation of the local chord stability, a second-order analysis considering restraint from web members and initial geometric imperfections is proposed. This study demonstrates that web members not only reduce the maximum chord deflection but also supply a restraint moment for the chords, thereby reducing the maximum stress of the chords, which was ignored or partially ignored in the past. A numerical example is presented to verify the effectiveness and correctness of the second-order analysis of the maximum stress on the chords presented in this paper. This method can be extended to the design and analysis of other similar lattice structures.

Seismic Behavior of Hollow-Core Composite Bridge Columns Having Slender Inner Steel Tubes

Seismic Behavior of Hollow-Core Composite Bridge Columns Having Slender Inner Steel Tubes

Vibration control of loosely supported cross-flow heat exchanger tube undergoing fluid elastic instability

In this theoretical work, the effect of support stiffness in controlling the nonlinear vibration of loosely supported cross-flow heat exchanger tube and support-impact forces is studied. The bending of slender heat exchanger tube is modelled using Euler-Bernoulli beam theory. The cross-flow induced forces on tube are modelled using quasi-steady flow model whereas the loose support is modelled with trilinear spring model. The Galerkin discretisation and time integration are used to solve the nonlinear governing differential equation of motion. From the results, it is observed that with the reduction of support stiffness, the chaotic motion of the tube gradually changes to periodic motion, the drastic changes in the acceleration of the tube during its motion reduces, and also the magnitude of the contact forces greatly reduces. Thus, if the support is made of low stiffness material or placing a low stiffer buffer layer over stiff support, the vibration and impact forces can be significantly reduced..

Low-velocity impact of clamped slender rectangular sandwich tubes with metal foam core

The main purpose of this work is to investigate the yield criterion and dynamic response of fully clamped slender rectangular sandwich tubes with metal foam core struck by a low-velocity heavy mass. A plastic yield criterion is proposed for the rectangular sandwich tubes with metal foam core. Using the yield criterion, analytical solutions are derived for the dynamic response of fully clamped slender rectangular sandwich tubes with metal foam core struck by a low-velocity heavy mass, in which the foam core strength effect and the interaction of bending and stretching are considered. Numerical calculations are carried out to predict the dynamic response of the rectangular sandwich tubes under low-velocity impact. The analytical model captures the numerical results reasonably. The effects of foam core strength and wall thickness of tube on the dynamic response are discussed in detail. It is shown that the present analytical model can reasonably predict the dynamic response of the rectangular sandwich tube with metal foam core under the low-velocity impact.

Acoustic demultiplexer based on Fano and induced transparency resonances in slender tubes

We give an analytical demonstration of the possibility to realize a simple phononic demultiplexer based on Fano and acoustic induced transparency resonances. The demultiplexer consists of a Y-shaped waveguide with an input line and two output lines. Each output line contains two stubs grafted either at a given position or at two positions far from the input line. We derive in closed form the expressions for a selective transfer of a single propagating mode through one line keeping the other line unaffected.

Determination of minimum miscible pressure in CO2-crude oil system of Changqing Oilfield

Carbon dioxide miscible flooding in low permeability sandstone reservoir can greatly enhance the recovery, the minimum miscible pressure (MMP) is the starting point of miscible flooding. Its determination is very important for oilfield development. In this paper, the internationally widely accepted thin tube experiment method and the bubble riser method are used to compare the minimum miscible pressure. Research results show that the minimum miscibility pressure obtained by slender tube displacement experiment is 22.12 MPa. The minimum miscible pressure measured by the bubbler method is 32.33 MPa, and the error result is large.

30 T scanning tunnelling microscope in a hybrid magnet with essentially non-metallic design

We report on the construction and performance of the first hybrid resistive-superconducting magnet (HM) based scanning tunnelling microscope (STM) above 30 T. This custom-design HM-STM features a novel design of the STM head unit, whose tip-sample approach is implemented using a slender piezoelectric tube (PZT). The scanner shares part of PZT by fixing a sapphire frame onto the front quarter of PZT to construct a compact tip-sample loop, realising an outer diameter of 8.8 mm, which makes it compatible with a narrow sample space. Its main components are made of non-metallic materials of sapphire, which allows it to be immune from eddy currents and to operate under the condition of strong magnetic field fluctuation from a hybrid magnet, as well as cryogen-free cryocooler magnet systems. To analyse the stiffness of the STM head unit, the eigenfrequencies with 11 kHz and 12 kHz in bending modes, 25 kHz in a torsional mode, and 67 kHz in a longitudinal mode were simulated by finite element analysis; also, the drifting rates of the STM in ambient conditions in the X-Y plane and Z direction were measured at 25.5 and 38.2 pm/min, respectively. We present the first atomic images in magnetic fields up to 30.1 T in an HM. The raw data show the stable and distinguished performance while ramping up to maximum fields, indicating the new device's potential capability of operating in the future 45T-hybrid magnet and hundred-field pulsed magnet. Meanwhile, our compact and concentric cylindrical STM insert can operate in the low-temperature tubular sample space housed by the HM bore to develop low-temperature and extreme high-magnetic field STM.

Yushulin Oilfield CO2- Comparison of minimum miscibility pressure test results for crude oil system

Miscible displacement of carbon dioxide in low permeability sandstone reservoirs can greatly improve oil recovery. The minimum miscible pressure is the starting point of miscible flooding. Its determination is very important for oilfield development. In this paper, the error analysis of the results measured by empirical formulas is carried out by the internationally accepted slim tube experiment method. Research results show that the minimum miscibility pressure obtained by slender tube displacement experiment is 22.12 MPa. The maximum, minimum and average miscibility pressures predicted by empirical formula method are 32.33 MPa, 7.85 MPa and 19.76 MPa, respectively. The relative error of the average minimum miscibility pressure predicted by all empirical formulas is 10.67%. The least relative error is the Yelling and Metcalfe correlation method, the relative error is 8.82%.

Nonlinear vibrations of a nuclear fuel rod supported by spacer grids

The internal components of Pressurized Water Reactors (PWRs), particularly nuclear fuel assemblies, must be able to withstand Flow Induced Vibrations (FIVs) during operating conditions and during extreme accident conditions, such as earthquakes. Nuclear fuel assemblies are composed of long slender tubes, filled with uranium pellets that are bundled together by periodic support provided by spacer grids. Spacer grids are square structures used to increase thermal mixing in the core and provide support to the fuel rods and guide tubes allowing for the installation and removal of nuclear fuel rods. Nevertheless, spacer grids constitute a nonlinear flexible boundary condition experiencing friction forces and impacts complicating the dynamics of the fuel rod-spacer grid system. In order to improve safety margins in the design of nuclear fuel assemblies, it is of great interest to understand the nonlinear behavior at the interface of the spacer grids with the fuel rods, investigating the complexity due to the nonlinear evolution of the system stiffness and damping properties. In particular, the effect of the constant evolution of the vibration amplitude as a function of the change of the excitation forces on the dynamics of the fuel rod response is still undetermined. Experiments were carried out in quiescent water and in air to understand the nonlinear vibration response of a single zirconium fuel rod supported by spacer grids. The vibration response under a step-sine harmonic excitation at different force amplitude levels in the frequency neighborhood of the fundamental mode was measured. The response of the rod displayed nonlinear phenomena such as the shift of the resonant frequencies, multiple solutions with some instabilities (jumps) and hysteresis, and a weak one-to-one internal resonance. Tests were performed on an empty rod and on a rod filled with tungsten pellets representative of nuclear fuel. The pellets were let free to move and were subsequently blocked axially to reproduce the effect of the beginning-of-life constraint in operational nuclear plants. The experimental data were processed by means of a simplified identification procedure to extract the damping parameters of the vibrating system. The equivalent viscous damping is found to increase and to be a function of the level of excitation and of the peak vibration amplitude.