Influence Of Cross-sectional Shape Research Articles

Gas transport law in inorganic nanopores considering the influence of cross section shape and roughness

To study the gas transport characteristics in rough inorganic nanopores, the effective pore size models of circular and rectangular nanopores are established, considering the influence of the adsorption water film, rock surface roughness, effective stress and the shape of the nanopore section. On this basis, the gas flow patterns are coupled, and the gas transport models in circular and rectangular rough nanopore are established respectively. The effectiveness of this model is verified by comparing it with experimental data and other scholars' models. At the same time, the effects of roughness, cross-sectional shape, cross-sectional aspect ratio, and humidity on gas migration are analyzed. The results indicate that regardless of the cross-sectional shape, an increase in roughness will lead to varying degrees of reduction in the apparent permeability of micro and nano pores. When the pressure is small, the influence of roughness on the gas permeability of rectangular cross-section nanopores is greater than that of circular cross-section nanopores. As the pressure increases, the influence of roughness on the gas permeability of rectangular and circular cross-section nanopores tends to be the same. The influence of roughness on the water saturation of rectangular cross-section nanopores is less than that on circular cross-section nanopores.

Influence of Cross-Sectional Shape on Flow Capacity of Open Channels

Open-channel flow can be easily found in nature and engineering projects, and the channels’ cross-sections are of various shapes. Research on the flow capacity of open channels with different cross-sections can help deepen our understanding of the dependence of open channels’ general characteristics on cross-sectional shapes at a theoretical level. Furthermore, it has potential practical value in engineering projects. Through theoretical analysis, experimental research, and numerical calculation, two conclusions can be drawn in the present article: (1) A general expression for flow capacity was deduced based on viscous fluid theory, and a parameter describing the influence of cross-sectional shapes on flow capacity, CQ, was obtained. The advantage of our method is that the expression can be used to calculate the parameter directly, which varies with general and flow field characteristics. Another advantage is that the parameter can describe general and flow field characteristics in a uniform way. (2) The width-to-wetted perimeter ratio was selected to describe the cross-sectional shapes. The dependence of the parameter, CQ, on cross-sectional shapes can be summarized as follows: In laminar flow, the parameter depends on the width-to-wetted perimeter ratio only. In turbulent flow at a medium or low Reynolds number, the parameter varied with width-to-wetted perimeter ratio and Reynolds number. In turbulent flow at a high Reynolds number, the parameter was independent of the width-to-wetted perimeter ratio.

THE FRACTAL MATHEMATICAL MODELS FOR SPONTANEOUS AND FORCED IMBIBITION WITH DIFFERENT CROSS-SECTION SHAPES IN SHALE OIL RESERVOIR

Large-scale hydraulic fracturing is the critical technology for effective shale oil production. However, the imbibition flow mechanisms of fracturing fluid in shale micropores and the influence of shale microstructure and physical properties are still indistinct, which makes the optimization goal of fracturing flowback unclear and restricts the enhancement of shale oil recovery. Therefore, based on SEM and XRD experiments, it is analyzed that shale has the characteristics of multiple pores, which are divided into organic pores, brittle mineral pores, and clay pores. Nonetheless, how the tube cross-section controls the interface displacement is not well discussed in the available literature, especially in irregular triangles, rectangles and other non-circular shapes. This paper studies the influence of cross-section shapes on the capillary force by considering the corner flow of the wetting phase, and it analyzes the imbibition dynamics of different types of pores. Using the shale multi-pores physical model and fractal theory, the shale semi-analytical solution models of SI and FI are established. Theoretical analysis of the water imbibition mechanisms shows that the key factors controlling SI and FI volume include imbibition time, fluid properties, pore cross-section shapes, tortuosity, and forced pressure.

Cylinder aeroacoustics: experimental study of the influence of cross-section shape on spanwise coherence length

New data and review of the spanwise coherence length is provided for flows over cylinders of different cross-sections: circular of diameter d, and rectangular of sectional aspect ratios (breadth (b) to height (d) ratio AR = b/d) of 1, 2 and 3. In the present measurements, the body has both d and spanwise length of 70d fixed, and the Reynolds number (based on d) range 6000–27,000 is covered. Two-point data are obtained from two hot-wire probes, one fixed in the symmetry plane and the other moving on the corresponding spanwise axis. Their position in a cross plane are deduced from preliminary measurement of the mean flow with a single probe, allowing fair comparisons between the different geometries and the introduction of uncertainty bars on coherence length values. At all tested regimes, a very good agreement is noticed between velocity-based and pressure-based coherence experimental data. Coherence length definitions are revisited, and the aeroacoustically consistent, integral length definition is selected, allowing fair synthesis of literature data into a single chart and empirical functions. Definitions for coherence decay models (e.g. Gaussian or Laplacian) are also adapted so that coherence length and coherence integral shall be equivalent. This preliminary work on coherence data and its spanwise integration enables transparent regressions and model selection. Generally, the Gaussian model is relevant for the lift peak, while the coherence exhibits a Laplacian decay at harmonics. On average, at peak Strouhal number, the coherence length for the circular and square cylinders is of 5d while it is of the order of 15d for the rectangular sections. It is concluded that the flow over those latter geometries is still a two-dimensional dynamics at the tone frequency. These values are almost preserved over the tested Reynolds number range. Coherence length value at harmonics is extensively documented. Spanwise coherence length is also discussed as an ingredient of acoustic efficiency.

The Influence of Cross-Section Shape on Failure of Rock Surrounding the Main Tunnel in a Water-Sealed Cavern

The influence of cross-section shape on rock stability was investigated by designing a similar model test and numerical simulation using particle flow code (PFC). The test results showed that the left- and right-hand sides of the entrance are subjected to tension, mainly forming vertical cracks or oblique cracks with a large dip angle. The vicinity of the entrance is subjected to the shear effect and the overall failure of the model is brittle in the similar test. Mesoscopic fractures mainly appear as tensile fractures, and a small number of shear fractures are found in the vicinity of the entrance. A long narrow coalescent-fracture zone is separately formed at the left- and right-hand sides of the entrance when approaching peak load in PFC test. Stress concentration occurs at the end of the long axis of the elliptic cross-section. The stress is high at the arch foot and spandrel of a horseshoe-shaped cross-section and a coalescent fracture zone formed at the arch foot on the right-hand side caused the tunnel to fail. The ovoid-shaped and vertical-wall-arched cross-sections are under significant tension, owing to the force chains distributed along the tunnel wall, show a large included angle with the tunnel wall. From the perspective of bearing capacity, a circle is the best section. From the perspective of failure mode, the horseshoe-shaped section is more suitable for use in corresponding practical engineering.

Influence of cross-section shape on energy harvesting from transverse flow-induced vibrations of bluff bodies

Hydroelastic experiments have been carried out in a free surface water channel to study the influence of the cross-section shape on the mechanical energy transfer from a uniform flow to a self-excited crossflow oscillating prism. Seventeen cross-section shapes were tested with the same mechanical properties (say, mass ratio and mechanical damping) and aspect ratio. Then, the study was focused on the role of the cross-section shape and reduced velocity on the prism dynamics and energy transfer from the fluid flow. It has been found that the geometric centroid of the semi-cross-section and the afterbody length of the cross-section represent a simple and effective metric to characterise the energy transfer. Two related dimensionless geometric parameters are introduced. The dependence of the energy transfer with these two parameters is studied and used to design successfully ‘in advance’ cross-section shapes with high energy transfer efficiencies. It has been observed from particle image velocimetry measurements that large energy transfer shapes are those in which, under strong oscillations, the flow follows the cross-section contour of one side and is fully detached on the other side.

Stationary Gas Dynamics and Heat Transfer of Turbulent Flows in Straight Pipes at Different Turbulence Intensity

The gas-dynamic and heat-exchange behaviours of air flows in gas-dynamic systems have a significant impact on the efficiency and environmental performance of most technical equipment (heat engines, power plants, heat exchangers, etc.). Therefore, it is a relevant task to obtain reliable experimental data and physical laws on the influence of cross-sectional shape and initial turbulence intensity on gas dynamics and the level of heat transfer. In this study, data were experimentally obtained on the instantaneous values of the local velocity and local heat transfer coefficients of stationary air flows in straight pipes with circular, square, and triangular cross-sections at different initial values of the turbulence intensity. The measurements were carried out with a constant temperature hot-wire anemometer, thermocouples, and pressure sensors. Based on the research results, data on the turbulence intensity and averaged local heat transfer along the length of pipes with different cross-sections were summarised. It has been established that turbulence intensity in a square pipe is up to 40% higher than in a round channel; in a triangular channel, on the contrary, it is up to 28% lower. After the air flow’s initial turbulence, the relaxation of the flow in square and triangular pipes occurs faster than in a round channel. It is found that the initial intensity of turbulence leads to an increase in the averaged local heat transfer, which is typical of all investigated pipe configurations and initial conditions.

Influence of Cross-Section Shape and FRP Reinforcement Layout on Shear Capacity of Strengthened RC Beams.

The evaluation of the shear capacity of an FRP-strengthened reinforced-concrete beam is challenging due to the complex interaction between different contributions provided by the concrete, steel stirrup and FRP reinforcement. The shape of the beam and the FRP inclination can have paramount importance that is not often recognized by the models that are suggested by codes. The interaction among different resisting mechanisms has a significant effect on the shear capacity of beams, since it can cause a reduction in the efficiency of some resisting mechanisms. A comparative study of the performance in the shear resistance assessment provided by three models with six different effectiveness factors (R) is performed, considering different cross-section shapes, FRP wrapping schemes, inclination and anchorage systems. The results revealed that the cross-section shape, the FRP inclination and the efficiency of the FRP anchorages have a significant effect on the shear strength of beams. The analysis results show that the three models are able to provide an accurate average estimation of shear strength (but with a coefficient of variation up to 0.35) when FRP reinforcement orthogonal to the beam axis is considered, while a significant underestimation (up to 19%) affected the results for inclined FRP reinforcement. Moreover, all the models underestimated the resistance of beams with a T section.

Influence of cross-section shape on granular column collapses

We investigate granular column collapses with different column cross-sections and associate the cross-section shape influence with a finite-size analysis. Previous research, confined to initially circular configurations, reviewed the importance of granular column collapse studies and concluded that the run-out distance scales with the initial aspect ratio. In this work, granular columns with three different types of initial column cross-sections (square, equilateral triangular, and rectangular cross-sections) are simulated using the discrete element method (DEM). We explore how non-circular cross-sections lead to different run-out distances. Based on the previously obtained finite-size analysis, we further link the initial radius in different directions to the relative size of a column and perform the finite-size analysis to explain the cross-section influence. In the end, a universal relationship, which includes frictional properties, relative sizes, and the cross-section influence, is proposed. Our results are shown to have direct relevance to various natural and engineering systems.

A study on the influence of cross-sectional shapes and convolutions on PVDF fiber properties

Polyvinylidene fluoride (PVDF) is a piezoelectric polymer for the potential massive production of smart textiles, facing the difficulty of synergetic improving its fiber strength and softness. Strengthening of flexible PVDF fibers via drawing incurs the reduction of fiber softness. Here, inspired by the cotton fibers, this study aimed to construct a strong and soft PVDF fiber by regulating its cross-sectional shape and longitudinal convolution. Mechanism of increasing softness by longitudinal spiral twisting was conducted during the strengthening of PVDF fibers with favorable cross-sectional shapes. Then circular, flat and kidney shaped PVDF fibers were prepared to conduct drawing and twisting under different parameters. The influences of cross-sectional shapes and convolutions on PVDF fiber properties were examined using scanning electron microscope (SEM), X ray diffraction (XRD), universal stretch meter and AFM. Results indicated that all the fibers became strong but rigid with increased drawing ratios, mainly due to their corresponding attenuation to increase fiber inner crystallization and surface smoothness. In specialty, the circular fiber had a higher crystallization increase ratio (106.3%) than that of kidney (74.7%) and flat (73.1%) fibers. Surprisingly, all drawn fibers became flexible and further strengthened after tensile twisting within 400 T/m. Overall the optimum strong and flexible fibers were obtained by 400 T/m tensile twisting of the 2 times drawn flat PVDF fibers.

Optical phonons in core-shell semiconductor prism nanowires affected by the cross-section shape

As building blocks of modern optoelectronic devices, semiconductor core-shell nanowires are usually prisms. The Raman spectra of the nanowires can vary with the cross-section shape and size. In the framework of the dielectric continuum and Loudon's uniaxial crystal models, we investigate the influence of cross-section shape on the optical phonons in prism core-shell nanowires. It is found that while the layer components decide the modes contained in the optical phonon spectra, the shape of a cross-section mainly affects the linewidth of a spectrum. Our calculations show that the electrostatic potentials of phonons have symmetry with the cross-section, while the dispersion relationships extend to bands in prism nanowires due to the cross-section's anisotropy, in contrast with the single dispersion lines in cylindrical ones. The anisotropy of optical phonons becomes apparent in the nanowires with fewer cross-section sides. Increasing the core area can narrow the dispersion bands, approaching the single lines of cylindrical nanowires as the area gets infinitely large. Reducing the gap between the layers' components can make the anisotropy of optical phonons weaker but not disappear. The theoretical results help to interpret the variation of the Raman spectra with the cross-section shape in the nanowires and related optical and electrical properties.

The cross-sectional effects of ribbon arch wires on Class II malocclusion intermaxillary traction: a three-dimensional finite element analysis

BackgroundThe application of intermaxillary traction is often accompanied by the unexpected movement of dentition, especially anchorage teeth. The aim of this study was to comprehensively compare the influence of cross-sectional shape of ribbon arch wires with edgewise and round wires on intermaxillary traction in Class II malocclusion treatment using FEA simulation.MethodsThe dentofacial structure was simulated in finite element software. A retraction force of 1.5 N was applied to different cross-sectional orthodontic arch wires: a ribbon wire (0.025 × 0.017-in. and 0.025 × 0.019-in.), a rectangular wire (0.017 × 0.025-in. and 0.019 × 0.025-in.) and a round wire (Φ 0.018-in. and Φ 0.020-in.).ResultsAmong the three groups, ribbon wire (0.025 × 0.017-in. and 0.025 × 0.019-in.) exhibited the lowest displacement in the X-axis (12.61 μm and 12.77 μm, respectively) and Z-axis (8.99 μm and 9.06 μm, respectively). However, the 0.025 × 0.017-in. ribbon wire showed the highest Y-axis displacement. In the round wire group, Φ 0.020-in. wire displayed less rotation than Φ 0.018-in. wire, where the sagittal, frontal and occlusal rotation of Φ 0.020-in. wire was almost half of that of Φ 0.018-in. wire. The movement of the first molar region was intermediate between the ribbon arch group and the round wire group. Notably, the values of the 0.025 × 0.017-in. arch wire displacement, which were higher than those of any other group, peaked at 0.019 mm in the central incisor region with a spike-like shape. The deformation range of the Φ 0.018-in. wire group was the largest in this study.ConclusionsThe cross-section of the arch wire influenced force delivery in Class II intermaxillary traction. With the same shape, a larger cross-sectional area led to less mandibular dentition movement. For the rectangular arch wire and ribbon arch wire groups, since the height and width were inverted, the vertical displacement of anchorage teeth in the ribbon wire group was reduced, but the possibility of buccal tipping in mandibular anterior teeth also increased.

Influence of cylinder breadth and shape on the onset of flow unsteadiness and the aeolian tone level

The Reynolds number for the onset of flow unsteadiness is determined for several canonical geometries (triangles, rectangles, ellipses and lozenges) at different sectional breadth (L) to height (d) ratios (aspect ratio AR=L∕d), for more than 70 shapes. The flow is modeled using a direct Navier–Stokes incompressible two-dimensional solver and the shape is defined by an Immersed Boundary Method. The employed procedure takes the fluctuation of the velocity in the wake as the criterion to define the unsteadiness and a binary search to find the transition. This procedure yields critical Reynolds number Rec values in agreement with available data in the literature. When AR approaches zero, the five shapes lead to almost the same value of 31, which corresponds to Rec for a flat plate normal to the flow. It is then found that Rec grows exponentially with the aspect ratio, the influence of the cross section shape being accounted for by a single regression parameter. For all aspect ratios, the ellipse exhibits the highest Rec, and the front-pointing triangle the lowest, the three other geometries laying in between those two. The physics of the influence of cross-section shape on Rec is analyzed, considering its link with recirculation length in particular. An exploitation of the results is outlined for the analysis of recent aeroacoustic shape optimizations at fixed Re=150, through correlation between the lift fluctuation at this regime with the distance to the onset of unsteadiness it corresponds to.

Influence of Cross-Sectional Shape on the Mechanical Properties of Concrete Canvas and CFRP-Reinforced Columns

Fiber-reinforced polymer (FRP) wrapping has become an attractive strengthening technique for concrete columns. However, the ingress of corrosion into the concrete through the gap of CFRP fiber greatly reduces the durability of concrete and the bearing capacity of specimens. Concrete canvas, a kind of corrosion-resistant and refractory material, is a promising method to enhance durability and carrying capacity. In this study, the concrete canvas (CC) and carbon fiber-reinforced polymer (CFRP) were used to jointly reinforce columns with square cross section, octagonal cross section, circular cross section, and elliptical cross section. The influence of section shape on the strengthening effect of the axial compression column was investigated by the axial compression test. The results showed that the section shape had a significant influence on the reinforcement effect of the axial compression column. The carrying load capacity and ductility coefficient of different columns follow this order: square column < oval-shaped columns < octagonal columns < circle columns. The increased amplitude of bearing capacity for the different columns with the increase of CC layers follows this order: square columns < oval-shaped columns < circle column < octagonal columns. Compared with the unconstraint columns, the bearing capacity of adopting two-layer CC columns increased by 129%, 155%, 150%, and 139% for the square, octagonal, circular, and elliptical columns, respectively. The octagonal column has the largest increase range. Compared with the unconstraint columns, the bearing capacity of adopting two-layer CC columns increased by 348%, 318%, 310%, and 296% for the square, octagonal, elliptical, and circular columns, respectively. The square column has the largest increase range. The stress concentration phenomenon of all section shapes was weakened after the CC was used. The application of the CC on CFRP-reinforced columns improves column ductility significantly, with some degree of increase in bearing capacity.

Experimental investigation and optimization on field shaper structure parameters in magnetic pulse welding

Magnetic pulse welding is a high-speed welding technology, which is suitable for welding light metal materials. In the magnetic pulse welding system, the field shaper can increase the service life of the coil and contribute to concentrating the magnetic field in the welding area. Therefore, optimizing the structure of the field shaper can effectively improve the efficiency of the system. This paper analyzed the influence of cross-sectional shape and inner angle of the field shaper on the ability of concentrating magnetic field via COMSOL software. The structural strength of various field shapers was also analyzed in ABAQUS. Simulation results show that the inner edge of the field shaper directly affects the deformation and welding effect of the tube. So, a new shape of field shaper was proposed and the experimental results prove that the new field shaper has better performance than the conventional field shaper.

Seismic performance of concrete walls reinforced by high-strength bars: cyclic loading test and numerical simulation

This study examines the influence of cross-section shape on the seismic behaviour of high-strength steel reinforced concrete shear walls (HSS-RC) designed with Grade HRB 600 MPa reinforcement. As part of the study, two flexure-dominant walls with rectangular and T-shaped cross-sections, are tested under reversed cyclic loading. Seismic performance is evaluated by studying the failure characteristics, hysteretic curves, energy dissipation, ductility, and reinforcing bar strains in the two walls. As part of the numerical study, two-dimensional (2D) and three-dimensional (3D) finite element modelling (FEM) are used to predict the seismic response of the rectangular and T-shaped walls, respectively. The test results show that compared to the rectangular wall, the flange in the T-shaped HSS-RC wall increased strength, energy dissipation and stiffness, but decreased ductility. The analytical hysteretic curves calculated using 2D and 3D FEM analyses show good agreement with the experimental test results.

The effect of cathode channel blockages on the enhanced mass transfer and performance of PEMFC

The design of flow field has a great influence on the mass transfer and performance of PEMFC (proton exchange membrane fuel cell) and lots of research works focus on this area. In this paper, 3D PEMFC models with a single straight channel are established to investigate the effect of blockages on mass transfer and performance. The influence of cross section shapes of blockages and dimensionless blockage length are discussed. Results show that cross section shapes of blockages have a great impact on the enhancement of mass transfer in PEMFC. The flow-guide part and the suppression part should occur together to enhanced the mass transfer with the flow-guide part upstream and the part suppression downstream. The ratio of the single blockage length to the channel length and the ratio of the blockage length to the spacing length also have a great impact on the enhancement of mass transfer in PEMFC. The PEMFC could obtain a superior performance as the ratio of the blockage length to the spacing length and the ratio of the total block length to the channel length are 0.5 and 30%, respectively.

Influence of cross-section shape on structure and properties of Lyocell fibers

Three kinds of Lyocell fibers with different cross-sections including circular, H-shape, and Y-shape (abbreviated as O-, H-, and Y-Lyocell) were prepared by a dry-jet wet spinning method. The effects of cross-sectional shape on structure and properties of Lyocell fibers were evaluated. The results showed H-Lyocell and Y-Lyocell exhibited triangular and dumbbell cross-sections, respectively, due to die swell. Both non-roundness factor and crystallinity of different cross-sectional Lyocell fibers were in the order of H-Lyocell > Y-Lyocell > O-Lyocell. All cross-sectional Lyocell fibers showed similar values of fineness and tensile strength. The profiled Lyocell fibers were superior to circular Lyocell fibers in terms of luster, dyeing properties, and moisture regain. The dye uptake and fixation rate of Lyocell fibers were influenced by shape in the order H-Lyocell > Y-Lyocell > O-Lyocell; while for luster and moisture regain the order was Y-Lyocell > H-Lyocell > O-Lyocell. Profiled Lyocell fibers are expected to open broader prospects in different textile or composite fields due to their various advantages versus conventional circular Lyocell fibers.

Numerical investigation of the influence of cross-sectional shape and corrosion damage on failure mechanisms of RC bridge piers under earthquake loading

The study presented in this paper describes the coupled influence of corrosion and cross-sectional shape on failure mechanism of reinforced concrete (RC) bridge piers subject to static and dynamic earthquake loading. To this end, two RC columns varied in cross-sectional shape and corrosion degree are considered. An advanced nonlinear finite element model, which accounts for the impact of corrosion on inelastic buckling and low-cycle fatigue degradation of reinforcing bars is employed. The proposed numerical models are then subjected to a series of monotonic pushover and incremental dynamic analyses. Using the analyses results, the failure mechanisms of the columns are compared at both material and component levels. Furthermore, using an existing model in the literature for uncorroded columns, a dimensionless corrosion dependent local damage index is developed to assess the seismic performance of the examined corroded RC columns. The proposed new damage index is validated against the nonlinear analyses results. It is concluded that the combined influence of corrosion damage and cross-sectional shape result in multiple failure mechanisms in corroded RC columns.

Experimental and Numerical Analyses for Earth Pressure Distribution on High-Filled Cut-and-Cover Tunnels

The use of high-filled cut-and-cover tunnels (HFCCTs) provides an ideal solution for reclaiming usable land in northwestern China because of the unique landforms of the Loess Plateau. Different from traditional tunnel boring methods, the HFCCT is first constructed and then backfilled in layers in the trench. Due to the backfill above the cut-and-cover tunnel (CCT) is required in quantity, currently, the existed estimating methods of the earth pressure may not suit the high-filled constructions. The ability to estimate the load on such tunnels and high backfill projects is extremely important. Conceptually, the Marston-Spangler (M-S) theory for buried culverts may be used to estimate earth pressure on HFCCTs. However, the earth pressure would be quite different from that of buried culverts in terms of the backfill volume, cross-sectional shape of structure, and foundation conditions. This paper presents physical experiments and numerical investigations to verify the influence of cross-sectional shape (arch and rectangle) of CCTs, foundation settlement, and load reduction using expanded polystyrene (EPS) for the vertical earth pressure (VEP) distribution and vertical displacement around a CCT. The experimental results agree well with the numerical analysis results. Moreover, further comparisons were also made to analytical analysis based on M-S theory. The comparison results indicate that analytical solutions for buried culverts cannot be applied to HFCCTs directly. In order to obtain the earth pressure accurately, designers must consider many influential factors.