Effects Of Cross-sectional Geometry Research Articles

The effect of cross-sectional geometry on the high-speed narrow open channel flows: An updated Reynolds stress model study

This numerical study investigates the effect of the channel cross-sectional geometries, namely archway, circular, and horseshoe on the mean velocity fields, secondary currents, turbulence characteristics, and bed shear stress distributions in supercritical narrow open channel flows. Six uniform flow simulations, combining two filling ratios comparable to sediment bypass tunnel flows, were performed in OpenFOAM. An updated Speziale-Sarkar-Gatski Reynolds stress model was used, which was validated with experimental data for a rectangular channel flow. Near the bottom corner, the sidewall curvature increment alters the verticality of secondary flows, distances the secondary velocity isovels, and bulges the longitudinal velocity isovels toward the boundaries which increases the local bed shear stress. It also restricts the vertical growth of the developing intermediate vortex and the lateral growth of the bottom vortex, which are attributed to the reductions of turbulence anisotropy gradient at the corner zone. Furthermore, it minimizes the converging of the contour lines of primary Reynolds shear stress as the sidewall curvature modifies the near sidewall longitudinal velocity gradient. Circular cross-sections produced 1.7% – 2.3% higher laterally averaged shear velocities U*l than archway, which are insignificant to be regarded as shear stress concentration. At the top corner, the curved sidewall distorts the flow property contour lines and influences the inner secondary vortex. The aspect ratio reduction swells the bottom vortex and decreases U*l. Overall, a horseshoe cross-section is the suitable choice for sediment carrying channels as it can provide sufficiently wide invert while minimizing the low-momentum fluid zones and the bed shear stress undulation.

Axial stress versus strain responses of CFRP confined concrete containing electronic waste aggregates

This research work investigates the axial stress versus strain responses of un-strengthened and carbon fiber reinforced polymer (CFRP) composites strengthened concrete specimens made with electronic waste coarse aggregates. For this purpose, 36 circular and non-circular 300 mm high concrete specimens constrained with CFRP sheets and partially replaced with E-waste coarse aggregates were prepared. The effect of cross-sectional geometry, 20% partial substitution of natural coarse aggregates with E-waste aggregates, corner effect of non-circular concrete specimens, confinement of specimens with CFRP sheets, and effect of the number of confinement sheets were also studied. In control concrete specimens, the coarse aggregates were 848 kg/m3 and E-waste aggregates were 212 kg/m3. The cement was 475 kg/m3 and fine aggregates were 655 kg/m3. Test results indicated that compressive strength is reduced by substituting natural coarse aggregates with E-waste aggregates. At the same time, compressive strength increased to 71%, 33%, and 25% for circular, square, and rectangular concrete specimens, respectively, by CFRP confinement. Whereas the axial strain increased to 1100%, 250%, and 133%, for circular, square, and rectangular concrete specimens, respectively, by CFRP confinement. CFRP sheets also enhanced the Poisson's ratio. Because of the greater confinement given by a double CFRP layer, it is more effective than a single layer. Furthermore, results also indicated that strength reduction in non-circular concrete specimens was greater than in circular concrete specimens for all studied cases. In the end, for theoretical calculations, strength and strain models for confined concrete suggested by different researchers were applied and compared with experimental results. In comparison to the experimental findings, theoretical data showed that most of the models were either on the higher or on the lower side, while only some model results matched well with the experimental data.

Elastic critical local buckling stress in cold-formed lipped channel and hat sections under uniform compression

The classical design approach for the elastic critical local buckling load of the cold-formed open section (CFOS) neglects the plate element interaction at the cross-section, which compromises the benefits of CFOSs designed for high performance. To derive a novel formula for the local buckling coefficient, taking into account the plate element interaction at the cross-section, a series of displacement functions for expressing the buckling deformations of the web, flanges, and lips caused by local buckling in CFOSs is proposed in this paper. The effect of cross-sectional geometry on the buckling coefficient was investigated using the proposed formula derived from Timoshenko’s plate buckling theory. Further, simplified formulae were proposed for the buckling coefficient and half wavelength of the elastic critical local buckling for practical use. The reliabilities of the proposed formulae were verified by comparing the results obtained from the proposed formulae with the analysis results based on the finite element method and finite strip method.

The effect of cross-section geometry on the lateral–torsional behavior of thin-walled beams: Analytical and numerical studies

In this paper, the elastic lateral–torsional behavior of simple beams is discussed by presenting a novel analytical solution and performing numerical studies. The motivation of the presented research is the observation that classic analytical prediction and finite element prediction are, typically, significantly different when the second-order nonlinear behavior of beams with initial imperfections is analyzed. To understand and explain the observed differences, a novel analytical model is worked out for the geometrically nonlinear analysis of beams with initial geometric imperfections. The advancement in the presented analytical solution is the explicit consideration of the changing geometry as the load increases. The most important steps of the derivations are summarized, and the resulting formulae are briefly discussed. The derivations are done for general cross-sections, however, the bending is assumed to act in one of the principal planes. Numerical studies are also presented, focusing on mono-symmetric cross-sections. As part of the numerical studies, first, the results of the new analytical formulae are compared to those from shell finite element analysis. The results suggest that the new formulae can capture the most essential elements of the behavior observed in the shell finite element calculations, justifying that the cross-section shape might have a significant effect on the nonlinear lateral–torsional behavior of beams. Then the effect of the lateral–torsional buckling is predicted by calculating buckling reduction factors, using the results of the geometrically nonlinear finite element calculations. The capacity prediction results, again, justify that the cross-section shape, as well as the sign of the assumed geometric imperfection, might have a non-negligible effect on the buckling reduction factors, and on the capacity of the member.

Effect of cross-sectional geometry on the compression fatigue behavior of NiTi refrigerants

Elastocaloric refrigeration requires refrigerants with a good heat transfer ability and a high fatigue life. A million-level fatigue life can be normally obtained for NiTi refrigerants via compressive loading. However, existing compression-based NiTi elastocaloric prototypes only focus on tube refrigerants, and no research has been reported on the cross-sectional geometry design and its influence on the compression fatigue behavior of NiTi refrigerants. Here, we propose tubular NiTi refrigerants of hole-type, fin-type, and layer-type cross sections and compare their compression fatigue behavior with NiTi tubes of the same cross-sectional area under cyclic loading of 20 Hz and 900 MPa. Results show that to achieve a larger specific heat transfer area (SA), the compression fatigue life of NiTi tubes monotonically decreases because of the decrease in the wall-thickness, while the layer-type NiTi refrigerant maintains a relatively high fatigue life of 1.7 × 106 cycles at a high SA level (3.83 cm2 g−1). This gives us insight into enhancing elastocaloric refrigerants’ heat transfer ability and fatigue life via geometry design.

Effect of Cross-Sectional Geometry on Hydrothermal Behavior of Microchannel Heat Sink

Abstract The aim of this paper is to numerically analyze the hydrothermal behavior of different cross-sectional geometries of microchannel heat sinks (MCHSs) and conduct a comparative analysis of traditional and non-traditional designs using ANSYS Fluent. It is expected that the proposed design discussed in this paper will improve the performance of MCHSs by maximizing the cooling capability and minimizing the thermal resistance and entropy generation rate, thus leading to better energy efficiency. The channel designs include a rectangular microchannel (RMC), a circular microchannel (CMC), an elliptical microchannel (EMC), a trapezoidal microchannel (TMC), a hexagonal microchannel (HMC), and a new microchannel (NMC) which has a plus-like shape. The discussed geometry of the NMC is designed in such a way that it maximizes the cross-sectional area and the wetted perimeter of the channel, keeping the hydraulic diameter constant ( D h = 412 {D_{h}}=412 µm). The performance of various channels is compared on the basis of pressure drop, wall temperature, thermal enhancement factor, thermal resistance, thermal transport efficiency, and entropy generation rates. It has been observed that the NMC is capable of cooling effectively and it can achieve a minimum wall temperature of 305 K, thus offering the lowest thermal resistance ( R th {R_{\mathrm{th}}} ), irreversible heat loss, and entropy generation rate. Moreover, the NMC has achieved the highest value of the thermal enhancement factor, i. e., 1.13, at Re = 1 , 000 \mathrm{Re}=1,000 . Similarly, it has the highest thermal transport efficiency of almost 97 % at Re = 1 , 000 \mathrm{Re}=1,000 , followed by the TMC and the RMC. Overall, the NMC has achieved the best performance in all aspects, followed by the RMC and TMC. The performance of the EMC, the CMC, and the HMC was found to be the worst in this study.

Effects of cross-section geometry on performance of corrugated miniature heat sink: Uniform, convergent, divergent, and hybrid cases

This study aims to improve the performance of a corrugated miniature heat sink by altering the cross-section size of the routes. Fully convergent and fully divergent as well as six hybrid models in terms of cross-section size are introduced and compared to the uniform model. The investigations are carried out on a water based system (Reynolds numbers ranged from 85 to 1145). The inferred outcomes of numerical simulations (that are experimentally validated by a pre-calibrated setup) indicate that converging and diverging routes cross-section can considerably affect both the flow and the heat transfer of the fluid in the corrugated-route. The maximum heat transfer coefficient occurs in a hybrid model, whereas the largest pressure drop tacks place in the fully convergent model. Compared to the uniform cross-section model, the heat transfer coefficient varies from −11.9% to 34.1%, and the pressure drop varies from −55.6% to 114.7%. To specify the model providing the best overall performance, the corresponding index values are compared for all the models. It is found that the fully divergent model has the highest value of index, which is about 1.81, followed by the hybrid models with a divergent pattern at the upstream. In conclusion, it is detected that diverging the cross-section of the corrugated route can be an efficient technique to enhance the thermal performance of heat sinks.

The effect of cross-section geometry on the performance of a solar nanofluid heater in a parabolic solar receiver: A comparison study

Backgroundsolar collectors play a considerable role in transferring the irradiative thermal energy to the working fluid flow. The geometrical manipulation can enhance the performance of solar energy systems and helps to improve solar energy extraction for going forward to the sustainable development of countries. Structural modifications along with choosing efficient geometry should be followed for solar collectors. To address this issue, the current numerical work compares three various cross-sections, potentially used in the solar collectors, as the rectangle, triangle, and trapezoid. Methodthe collector is filled with nanographene-water nanofluid. The numerical simulation for various Reynolds numbers, volume fractions of nanoparticles and cross-section shapes are performed and the changes in the hydraulic and thermal performance of the fluid flow are appraised. Findingsit is shown that the Nusselt number and pressure drop achieve a higher value by increasing the Reynolds number and the volume fraction of nanoparticles. The rectangular duct presents the best thermal behavior by smearing the hot zone on the absorber plate and the Nusselt number at least 72% higher than the other geometries, for Re = 18, 000. At the highest Reynolds number, the rectangular duct can mitigate 5% the pressure drop compared to the other geometries. The performance evaluation criteria for the rectangular duct is 14 and 9%, respectively, for the volume fraction of 1 and 2%, more than the triangular duct, having the least value of the performance.

Effects of cross-sectional geometry on flow characteristics in spiral separators

ABSTRACT As flowing film gravity concentrators, spiral separators are extensively used in the processing of numerous minerals. Appropriate design of their cross-sectional geometries has been known as an effective method to improve the performance of spiral separators. However, limited work has been published on the impact of cross-sectional geometry on flow field characteristics in spiral separators. In this study, the effects of cross-sectional geometries with various parabolic profiles (|x|=m|y| n ) of a spiral separator on the flow film thickness, flow pattern and flow regime were investigated by numerical simulation. The validity of the simulation approach was confirmed by the reasonably good agreement between the predicted and measured flow film thickness in the own laboratory spiral separator. Results have shown that the flow film thickness and the mean primary velocity in the inner and middle troughs are reduced by decreasing downward bevel angle or increasing parabolic index. The dominant region of the secondary flow can be expended inward by increasing the downward bevel angle and decreasing the parabolic index. As the radial position extends inward, a larger downward bevel angle is more conducive to improving the intensity of secondary flow. A wider laminar flow region can be obtained with a smaller downward bevel angle or a larger parabolic index. The flow film thickness has a significant positive correlation with the trough slope in the inner and middle troughs. It is recommended that the matching relationship between material properties and flow field characteristics should be fully considered when selecting the cross-sectional geometry. Thus, this study aids the structural design of the cross-sectional geometries of spiral separators.

The Effects of Cross-Sectional Geometry on Wave-Induced Loads for Underwater Vehicles

This article investigates the role that cross-sectional geometry plays on the magnitude and phase of wave-induced linear loads experienced by an underwater vehicle operating near the surface. A towing tank with wave making capabilities is used to measure the wave-induced forces and moments on various cross-sectional shapes experimentally. These are compared to predictions we made using a framework that can handle non-body-of-revolution geometries. In many cases, our experimental results were the opposite of the theoretical predictions. For instance, according to the predictions, for long wavelengths, the aspect ratio of a rectangle should not influence the linear heave force. However, we found that the heave force was proportional to the planform area of the rectangle. This study is a systematic investigation of the effects that changing the cross-sectional shape from a body-of-revolution to either a square, rectangular, or asymmetric shape, has on the wave-induced loads.

Model Testing on the Effects of Section Geometry and Stiffness on the Cyclic Lateral Behavior of Piles in Loose Sand

In this study, two-way cyclic lateral loading tests with constant displacement amplitude are performed to investigate the effect of cross section geometry and modulus of elasticity on the behavior of model piles in sand. Various laboratory pile models were tested in a metal test tank equipped with various facilities including cyclic lateral loading system, devices to measure displacement and pressure along the pile, an inverter to adjust or change loading frequency, sand raining system, etc. Different cross section geometries, including square and circular shapes, were used for piles made of polyethylene and polyurethane. A loading frequency of 0.29 Hz and a total number of 145 loading cycles were used for all the tests. Results revealed that in constant displacement amplitude tests, both lateral load resistance of the pile head and stiffness of the pile–soil system increase with an increase in the number of loading cycles; however, the rate of increase gradually decreases. It is shown that these variations may be formulated using a logarithmic relationship, which includes a degradation parameter reflecting rate of these changes. For tests with different pile cross section shapes, dimensions, and moduli of elasticity, the degradation parameter varied from 0.08 to 0.18. The pile head load and stiffness of the pile–soil system at the end of the 145th cycle varied from 1.4 to 1.85 times those of the first cycle for different section shapes, dimensions, and moduli of elasticity.

Evaluation of stress distribution in nickel-titanium rotary instruments with different geometrical designs subjected to bending and torsional load: a finite element study

IntroductionGeometrical designs of nickel-titanium (NiTi) rotary instruments have a considerable influence on their mechanical performance, and thereby have the tendency to fracture.AimTo evaluate the effect of cross-sectional geometry, pitch, taper, and off-center cross-section on the stress distribution in NiTi instruments under bending and torsion conditions using finite element analysis (FEA).Materials and methodsEleven theoretical three-dimensional finite element (FE) models of rotary instruments were constructed and divided according to the geometric design tested into; group 1 (cross-section geometry): four FE models with four different cross-section designs (triangle, convex triangular, parallelogram, and rectangle). Group 2 (pitch): three FE models with different pitches (5, 10, and 15 threads). Group 3 (taper): two FEA models with two different tapers (0.04 and 0.06). Group 4 (centering): two FEA models (off-centered and centered cross section). The behavior of the instrument under bending and torsional conditions was analyzed mathematically in SolidWorks software package.ResultsThe pattern of stress distribution was varied by altering cross-sectional geometry, pitch, taper, and off-center cross section.ConclusionNo single geometrical design could be beneficial for all stress conditions. To decrease the stress accumulation during bending of rotary files in curved root canals, the rotary NiTi instruments should be designed with rectangle cross-section configuration, low pitch, reduced taper, and with centered cross section. This design improved the flexibility of rotary NiTi instruments. However, to improve the torsional resistance during root canal preparation of narrow canals, the file should be designed with parallelogram cross-sectional configuration, low pitch, increased taper, and eccentric cross-section design.

Effects of cross-sectional geometry and force direction on bending strength and modulus of elasticity of some softwood beams

The effects of cross-sectional geometry and force direction on bending strength (MOR) and modulus of elasticity (MOE) were investigated in selected softwoods. The specimens were constructed of Scots pine (Pinus sylvestris), Black pine (Pinus nigra), Siberian pine (Pinus sibirica), Stone pine (Pinus pinea), Nordmann fir (Abies nordmanniana), Oriental spruce (Picea orientalis), and Lebanon cedar (Cedrus libani). A total of 280 specimens were prepared from these seven species in two different cross-sectional geometries (circular and square, equal in area) and tested in two characteristic force directions (tangential and radial) by 10 replications. They were subjected to three-point bending tests according to TS 2474 (2005) and TS 2478 (2005) to obtain the MOR and MOE. The results showed that the type of cross-sectional area and direction of applied force, individually or together, had considerable effects on the MOR and MOE. The MOR values of the circular-sectioned specimens were 5% greater than those of the square-sectioned specimens. The MOE values of the circular-sectioned specimens were on average 19% greater than those of the square-sectioned specimens. The MOR and MOE values were on average 7% and 17% greater, respectively, for the force applied in the tangential direction.

Exactness of measured/predicted temperature distributions for heat generation in arbitrary non-variable cross-section bar using entropy generation method

• A novel application of second law of thermodynamics. • Usable for validation purposes in every study which involves heat transfer. • Presenting a unique value of non-dimensional total entropy generation rate. • Investigating the effect of cross sectional geometry on lost work. The purpose of the present study is to introduce the entropy generation method as a new validation tool of numerical and experimental studies in the heat transfer field where there exist no similar solutions with which to compare results. Analysis of temperature profiles has been conducted in bars with internal thermal energy generation, constant temperature boundary condition and arbitrary non-variable cross section. The bars have steady state Fourier heat conduction and uniform thermal energy generation. The total rate of entropy generation can be calculated using two different methods: The 1st method is based on integrating local entropy generation rate on the solution domain, and the 2nd one is based on the thermodynamic definition of entropy and the Clausius theorem. The equality of these two results depends on the exactness of the applied temperature profile. The closer the entropy generation rates in the control volume (EGRCVs), the more accurate the predicted temperature profile would be and thus, the obtained results are more reliable. Seven different geometries have been examined for the bar cross section and a correlation between error of temperature distribution and error of entropy generation has been obtained. Moreover, the effect of the cross section geometry on entropy generation has been studied and the distribution of local entropy generation rate for the selected geometries was plotted.

10km/h バンパーバリア衝突性能におよぼすバンパービーム断面形状の影響

10km/h バンパーバリア衝突性能におよぼすバンパービーム断面形状の影響

Numerical Investigation on Cold-Formed Steel Lipped Channel Columns with Intermediate Web Stiffeners

This work describes finite element simulation into the ultimate strength and buckling behaviour of cold-formed steel lipped channel columns with intermediate web stiffeners subjected to axial compression. Numerical simulation is performed by using finite element analysis software ANSYS. A reliable finite element model is used for the parametric study of effects of cross section geometries on the ultimate strength and buckling behaviour of cold-formed steel columns are investigated. All the section geometries in this study also satisfied the limitations given for pre-qualified sections in direct strength method. The cross sectional dimensions, section properties and length of the specimen are obtained by using CUFSM software. The ultimate strength predicted by the finite element analysis are compared with the strength calculated using the current direct strength method specifications for cold-formed steel structures, suitable design recommendations are proposed.

Numerical analysis of cold-formed steel welded tube filled with concrete made of crystallized slag aggregate

This paper presents a nonlinear finite element model to investigate the behaviour of cold- formed steel tubes filled with concrete made with crystallized slag aggregate. The columns had different lengths so that the length-to-depth ratio varied from 0.49 to 24. Nonlinear models for confined concrete and steel welded tubes with taking into account the effect of residual stress of steel section were used in the finite element model. The study was conducted over a wide range of concrete cylinder strengths from 20 to 45 MPa. The depth of flat portion-to-plate thickness (d/t) ratio hollow sections steel ranged from 24 to 52, covering compact and slender sections. The main studied parameters were: the section dimension and the effect of the in filled concrete and its age. The results obtained from the finite element analysis were verified against experimental results. An extensive parametric study was conducted to investigate the effects of cross-section geometry and concrete strength on the behaviour and strength of the columns. The column strengths obtained from the finite element analysis were compared with the design strengths calculated using the Eurocode 4.

Restrained distortional buckling capacity of half-through bridge girders

Steel beams with continuous and complete tension flange restraint buckle in a restrained distortional buckling (RDB) mode. Lateral buckling of half-through girders is an important example of this phenomenon because of the restraint offered by the deck, and due to the flexibility of the web in restraining the compressive flange. A numerical study was undertaken to investigate the distortional buckling behaviour of simply supported compact steel I-beams subjected to uniformly distributed load. For this purpose, a finite-element model was developed using ABAQUS. It was then used in a parametric study to simulate the distortional buckling behaviour and capacity of half-through girders, and investigate the effect of cross-section geometry and yield strengths in a RDB mode on the buckling moments of doubly-symmetric steel I-beams. Then a new formula based on the regression analyses has been proposed to predict the member moment capacities of steel I-beams subjected to RDB. The results indicate that the proposed...

Influence of Cross Sectional Geometry on Surface Plasmon Polariton Propagation in Gold Nanowires

We investigated the effects of cross sectional geometry on surface plasmon polariton propagation in gold nanowires (NWs) using bleach-imaged plasmon propagation and electromagnetic simulations. Chemically synthesized NWs have pentagonally twinned crystal structures, but recent advances in synthesis have made it possible to amplify this pentagonal shape to yield NWs with a five-pointed-star cross section and sharp end tips. We found experimentally that NWs with a five-pointed-star cross section, referred to as SNWs, had a shorter propagation length for surface plasmon polaritons at 785 nm, but a higher effective incoupling efficiency compared to smooth NWs with a pentagonal cross section, labeled as PNWs. Electromagnetic simulations revealed that the electric fields were localized at the sharp ridges of the SNWs, leading to higher absorptive losses and hence shorter propagation lengths compared to PNWs. On the other hand, scattering losses were found to be relatively uncorrelated with cross sectional geometry, but were strongly dependent on the plasmon mode excited. Our results provide insight into the shape-dependent waveguiding properties of chemically synthesized metal NWs and the mode-dependent loss mechanisms that govern surface plasmon polariton propagation.

Effect of Cross Sectional Geometry on Band Gap of Silicon Nanowires

Effect of Cross Sectional Geometry on Band Gap of Silicon Nanowires