Circular Cross-sectional Shape Research Articles

Effects of fuselage shape on helicopter aerodynamic performance in case of intermeshing-rotor interference

To study the influence of fuselage shape on the aerodynamic performance of a helicopter under the interference of an intermeshing-rotor, a numerical simulation method of flow field under the forward flight state of Synchropter is established based on the lattice Boltzmann method. Firstly, the Maryland helicopter was calculated to verify the scientific validity of the method. Then, the simplified S-97 fuselage was used as the object of analysis to analyze the aerodynamic data such as surface pressure, friction, and lift resistance of the fuselage with different head curvature, cross-section shapes, and transition segments under Synchropter interference with different attack angles in forward flight. The results show that increasing the radius of curvature of the nose can reduce the total drag of the fuselage; the fuselage with a circular cross-section shape has better aerodynamic characteristics of lift resistance, and the fuselage with rhombic cross-section shape has better transverse stability; the transition section with backward position, smaller upward dihedral angle, and smooth transition can avoid serious airflow separation and achieve the purpose of drag reduction.

Cross-sectional shape effect of stay-in-place formwork column on axial compressive behaviour

Experimental and numerical studies on the behavior of composite columns with prefabricated self-compacting mortar (SCM) stay-in-place (SIP) formwork and post-cast normal-strength core concrete were presented.The axial compression of twenty-eight reinforcement concrete (RC) composite columns having square or circular cross-section shapes, with formwork thicknesses of 10 mm or 15 mm, and confined with one or two layers of Carbon Fibre Reinforced Polymer (CFRP (, were tested. A finite element (FE) model was generated to simulate the stress–strain relationship, and failure mode of the column using ABAQUS software. The results show that square cross-section-shaped columns exhibited lower axial load and displacement capacities than their counterparts of equivalent circular cross-section-shaped columns. This behavior maintained consistent regardless of the use of the SCM-SIP formworks or the wrapping with CFRP fabrics. Among the various confinement systems compared in this study, the efficiency of the CFRP was the greatest. Good bonding with no peeling failure was observed between SCM-SIP formwork and core concrete, indicating the good integrity of the composite columns. Consistency between the FE model and experimental results was observed for both cross-section shapes, indicating the precise and plausible characteristics of the model to sensibly estimate the stress-strain behaviors.

Investigation into the Effects of Cross-Sectional Shape and Size on the Light-Extraction Efficiency of GaN-Based Blue Nanorod Light-Emitting Diode Structures

We investigated the effect of cross-sectional shape and size on the light-extraction efficiency (LEE) of GaN-based blue nanorod light-emitting diode (LED) structures using numerical simulations based on finite-difference time-domain methods. For accurate determination, the LEE and far-field pattern (FFP) were evaluated by averaging them over emission spectra, polarization, and source positions inside the nanorod. The LEE decreased as rod size increased, owing to the nanorods’ increased ratio of cross-sectional area to sidewall area. We compared circular, square, triangular, and hexagonal cross-sectional shapes in this study. To date, nanorod LEDs with circular cross sections have been mainly demonstrated experimentally. However, circular shapes were found to show the lowest LEE, which is attributed to the coupling with whispering-gallery modes. For the total emission of the nanorod, the triangular cross section exhibited the highest LEE. When the angular dependence of the LEE was calculated using the FFP simulation results, the triangular and hexagonal shapes showed relatively high LEEs for direction emission. The simulation results presented in this study are expected to be useful in designing high-efficiency nanorod LED structures with optimum nanorod shape and dimensions.

Shape transformers for crashworthiness of additively manufactured engineering resin lattice structures: Experimental and numerical investigations

Cellular materials have superior specific properties (e.g., specific strength, stiffness, and energy absorption) as compared to their monolithic material counterparts. With rapid advancements in additive manufacturing technology, the uniquely complex geometry of these materials – particularly periodic lattices – can be easily reproduced for additional experimental research, characterization, and potential industrial applications. This work utilizes the idea of shape transformers – previously employed to describe the structural efficiency of beams subjected to bending – to define new strut-based lattices, whose struts do not have the typical solid, circular cross-section shape. Both experimental and numerical model results have shown that this design parameter can be utilized to manipulate the crashworthiness efficiency of lattice materials. It is found that designing with a square or a rectangular cross-section could increase the plateau stress by up to 52% while increasing the mass normalized specific energy absorption by up to 32%.

Multiaxis Hybrid Simulation of Collapse Resistant Buildings with Ductile Soft Story Formed by Concrete-Filled Steel Tube Columns

A widespread problem in regions of low to moderate seismicity is the failure of buildings with soft-story collapse mechanisms. A reliable approach to improve the design of such buildings is to use concrete-filled steel tube (CFT) columns to form a ‘ductile’ soft story to arrest damage at the first level. This can perform as an isolator to limit the damage and prevent it from spreading to the rest of the building. In this paper, the multiaxis hybrid simulation method is used to evaluate the three-dimensional response of CFT columns while they serve as part of a building developing ductile soft first story mechanism. For this purpose, the multiaxis substructure testing (MAST) system at Swinburne University of Technology was utilized to simulate realistically the time-varying multi-directional boundary forces generated by ground motions on the CFT columns. The circular and square cross-section shapes as the most popular type of CFTs were tested and the damage progression, global hysteretic behavior, and deteriorating mechanisms were studied. The obtained data were then used to conduct a fragility analysis to compute the risk of collapse. The results highlight the excellent performance of CFTs and their potential to construct low-damage collapse resistant buildings.

Carbon Rovings as Strain Sensor in TRC Structures: Effect of Roving Cross-Sectional Shape and Coating Material on the Electrical Response under Bending Stress.

This study investigated the ability of electrically conductive carbon rovings to detect cracks in textile-reinforced concrete (TRC) structures. The key innovation lies in the integration of carbon rovings into the reinforcing textile, which not only contributes to the mechanical properties of the concrete structure but also eliminates the need for an additional sensory system, such as strain gauges, to monitor the structural health. Carbon rovings are integrated into a grid-like textile reinforcement that differs in binding type and dispersion concentration of the styrene butadiene rubber (SBR) coating. Ninety final samples were subjected to a four-point bending test in which the electrical changes of the carbon rovings were measured simultaneously to capture the strain. The mechanical results show that the SBR50-coated TRC samples with circular and elliptical cross-sectional shape achieved, with 1.55 kN, the highest bending tensile strength, which is also captured with a value of 0.65 Ω by the electrical impedance monitoring. The elongation and fracture of the rovings have a significant effect on the impedance mainly due to electrical resistance change. A correlation was found between the impedance change, binding type and coating. This suggests that the elongation and fracture mechanisms are affected by the number of outer and inner filaments, as well as the coating.

Experimental study of surface roughness effects on hydrodynamic characteristics of a submerged floating tunnel

Marine biofouling is a major concern in the operational performance of submerged floating tunnels (SFTs). The objective of this research is to investigate the effects of marine fouling (represented by surface roughness) on the hydrodynamic behavior of SFTs, including the hydrodynamic forces on the SFT subject to current-only, wave-only, and combined current-wave flow conditions. The effects of increased surface roughness induced by marine fouling on the dynamic response of an SFT are characterized by hydrodynamic force coefficients, including drag and inertia coefficients. At the Water Lab of Delft University of Technology (TU Delft), experiments have been performed in a wave-current flume to compare the SFTs’ behaviors as affected by different roughness characteristics. In addition, a parametric cross-section for an SFT is presented, and the hydrodynamic performance associated with surface roughness effects on the parametric shape and circular SFT cross-section shape are compared. The results show that the parametric shape can effectively reduce the drag coefficient (Cd) under current-only conditions and lower the inertia coefficient (Cm) when waves are present. As roughness height and coverage ratio increase, Cd generally increases while Cm decreases. However, small differences in Cd and Cm can be observed with regard to roughness parameters for wave-only conditions. The Morison coefficients adapted for a marine-fouled SFT measured in the experiments are compared to predictions from engineering standards and are recommended for engineering practice.

Effects of roughness on hydrodynamic characteristics of a submerged floating tunnel subject to steady currents

The effects of surface roughness as induced by marine fouling on the hydrodynamic forces on a submerged floating tunnel (SFT) are experimentally and numerically investigated in detail at Reynolds numbers Re = 8.125 × 103–5.25 × 104. A sensitivity analysis to different roughness parameters including roughness height, skewness, coverage ratio, and spatial arrangement is performed. In addition, an optimized parametric cross-section for an SFT is proposed, and the hydrodynamic performance of the parametric shape and circular SFT cross-section shape with roughness elements is compared. The pressure distribution along the SFT, flow separation and wake characteristics are analyzed to provide a systematic insight into the fundamental mechanism relating the roughness parameters and flow around an SFT. In order to better understand the nonlinear relationships among structural geometry, roughness parameters, flow states, and structural response, an artificial intelligence method using Random Forest (RF) for feature importance ranking is applied. The results show that with the parametric shape, the hydrodynamic forces on the fouled SFT can be effectively mitigated. The roughness height and coverage ratio affect the equivalent blockage and hence, change flow separation and recirculation length in the wake. Lower skewness of the roughness elements can increase the critical Re by changing the relative roughness parameter. Horizontal arrangement of the roughness elements on an SFT generally results in the largest hydrodynamic forces, compared to staggered and vertical distributions. Throughout the feature importance ranking, the flow regime is found to be the most important feature of the hydrodynamics of the SFT. In addition, the SFT cross-section shape and roughness coverage ratio play a dominant role.

Dynamic Composite Materials Characterisation with Hopkinson Bars: Design and Development of New Dynamic Compression Systems

The split Hopkinson pressure bars (SHPB) system is the most commonly employed machine to study the dynamic characteristics of different materials under high strain rates. In this research, a numerical investigation is carried out to study different bar shapes such as square, hexagonal, and triangular cross-sections and to compare them with the standard cylindrical bars. The 3D finite element model developed for circular cross-sectional shapes was first validated with the experimental results and then compared with the other proposed shapes. In most scientific research, cylindrical cross-section bars with a square cross-section specimen are traditionally used as they have several advantages, such as in situ imaging of the side surfaces of the specimen during stress wave propagation. Moreover, the flat surfaces of the proposed shapes counter the problem of debonding strain gauges, especially at high impact pressures. Comparison of the results showed an excellent confirmation of the sample dynamic behaviour and different geometric shapes of the bar geometries, which validates the choice of the appropriate system.

Crashworthiness comparison of two-dimensional cellular sandwich cores under axial compression load

Structures that absorb energy efficiently have applications in many fields. In this paper, thin-walled structures with hexagonal, circular, X-type, square and octagonal cross-sectional shapes subjected to quasi-static compression are analyzed using FEM simulation. The results showed that the shape of the cross section has a significant effect on the mechanical properties and energy absorption capability. All structures of various cross-sectional shapes show almost the same specific stiffness, but the specific strength varies with the corner numbers. For energy absorption, the hexagonal structure exhibits the best specific energy absorption and crush stress efficiency among all considered structures.

The reliability assessment of the method for calculating the strength of oblique sections in reinforced concrete elements with various cross-sectional shape

Introduction. The current standards for the design of concrete and reinforced concrete structures provide no methods for calculating the strength of the oblique sections in bending elements of various cross-sectional shape under the action of transverse forces. This prompts the designers to use simplifications in calculation of such elements, which, in some cases, may lead to excessive consumption of transverse reinforcement or the strength underestimation.Aim. The performed study was aimed at assessing the reliability of a new method for calculating the strength of oblique sections in bending reinforced concrete structures with a non-rectangular cross-sectional shape.Materials and methods. The reliability assessment of a new procedure for calculating oblique sections of a various cross-sectional shape was performed by the comparison between the calculated and experimental values of the transverse force received by the oblique section of reinforced concrete elements with various cross-sectional shape. The study considers the oblique bending tests of the samples with an annular, circular, and square cross-sectional shape, as well as T-shaped samples with a crossbar both in a stretched and compressed zone. The reliability assessment was performed using generally accepted methods of statistical analysis.Results. The distributions of ratios of the experimental and calculated values of the destructive transverse force for various-section test samples were obtained to be close to normal ones. According to the results of the reliability assessment, the proposed procedure of calculating the strength of oblique sections in elements with various cross-sectional shape was established to be comparable with the procedure accepted in the SP 63.13330.2018 Rules and Regulations for calculating rectangular cross-section elements in terms of the accuracy and reliability indices.Conclusions. The proposed procedure of calculating the strength of oblique sections in elements with various cross-sectional shape was determined to be comparable with the procedure accepted in the SP 63.13330.2018 Rules and Regulations for calculating rectangular cross-section elements in terms of the accuracy and reliability indices.

Compression waves in semi-circular channel

Partially filled pipe flows are commonly observed in urban hydraulics, sewers and road crossings. The occurrence of a compression wave in the confined space may result from flash flooding, transient operation or accidental blockage, inducing explosive conditions. In this study, the propagation of a compression wave was studied in a relatively large laboratory flume of semi-circular cross-section. The unsteady flow properties were recorded to understand how the circular cross-sectional shape impacted the surging water propagation. Both free-surface and velocity data indicated a marked impact of the compression wave passage, with large instantaneous fluctuations comparable to and sometimes larger than observations of compression waves in rectangular channels.

Finite Element Analysis of Metal Thread-Forming Process with Self-Tapping Screw

To clarify the mechanism of differences of forming torque for screws with different cross-sectional shapes, we have compared the forming process of tapping screw type-3, a screw with circular cross-sectional shape, and C-TITE*3, a screw with cross-sectional shape of triangle. At first, we captured cross-section view of thread-formed shape of work piece and measured time history of forming torque by experiment. Next, we created finite element models of screws of each shape and thread-forming process was numerically simulated using Simufact Forming 2021.1 by MSC software. Comparing shape of work piece and curve of forming torque from analysis with that from test, validation was confirmed. In the latter half of this paper, we separately calculated torque for each part of surface of screw, and compared breakdown of the two. It was founded torque at top surface was dominant, and that of C-TITE was remarkably smaller than that of tapping screw type-3 because of difference in contact circumference.

Evaluation of the root canal cross-sectional morphology in maxillary and mandibular premolars in Saudi subpopulation

Introduction: Cone-beam computed tomography (CBCT) is a recent advancement in diagnostic radiology in dentistry which allows the clinician to have a clear 3D view of the root canals before starting the endodontic treatment. The goal of the present research was to assess the root canal cross-sectional shape (RCCSS) in maxillary and mandibular premolars in the Saudi Arabian subpopulation.Materials and Methods: In the present study, radiographs of 330 patients who had teeth with complete root development and closed apices were selected. Root canal shapes were assessed at the coronal and middle thirds, and in the apical third, 1 mm above the apical foramen using CBCT. Categorical variables were explained as frequencies and percentages and evaluated using the Chi-square test.Results: 1666 premolars were evaluated in the study. Maxillary first and second premolars were found to have a maximum circular cross-sectional shape at the coronal, middle, and apical sections in most of them followed by flattened and oval cross-sectional shapes except the maxillary right second premolars where the most frequent RCCSS was flattened in the coronal section (71%), circular in the middle (14%), and apical (10%) section. The most recurring coronal RCCSS in mandibular first and second premolars was oval followed by flattened and circular, while the most frequent cross-sectional shape in the middle and apical sections was found to be circular followed by oval and flattened RCCSS.Conclusion: Marked variations were observed in the coronal and middle RCCSS of maxillary and mandibular premolars though the most prominent RCCSS in the apical section was the circular shape.

OPTIMIZATION OF HEAT CONDUCTION FOR TREELIKE NETWORK WITH ARBITRARY CROSS-SECTIONAL SHAPE

To minimize the thermal resistance of the fractal treelike heat conduction network and develop an optimization principle applicable for the network with an arbitrary cross-sectional shape, this paper first establishes a theoretical model regarding the total thermal resistance of the symmetric treelike network with arbitrary cross-sectional shapes and then studies the effects of the geometric and structural parameters of the network on its total thermal resistance. The numerical simulations are also performed to analyze the influences of the geometric and structural parameters of symmetric treelike networks with circular, rectangular and triangular cross-sectional shapes on the total thermal resistance. Both the theoretical model and the numerical simulation show that the total thermal resistance of the network with an arbitrary cross-sectional shape first decreases and then increases with increasing cross-sectional area ratio but always increases with increasing length ratio of branches at two successive branching levels when the total branch volume is constant. When the cross-sectional area ratio is equal to the reciprocal of the branching number, the treelike network has the minimum total thermal resistance. This scaling law is applicable for the treelike network with an arbitrary cross-sectional shape to achieve the minimum total thermal resistance.

Multi-axis testing of concrete-filled steel tube columns forming ductile soft-story in multi-story buildings

In regions of low-to-moderate seismicity, the design of multi-story buildings with strong-beams weak-columns are quite common, which triggers the formation of a soft-story collapse mechanism during rare ground motions. A design approach to overcome this issue is introducing a ductile soft-story at the first level, such that the damage is controlled, while the above stories remain in the elastic response range. In this approach, the ductile soft-story acts as an isolator and limits the damage at only the first-level, thereby reducing the cost and time of repair and improving the safety and resilience of these buildings. The use of concrete-filled steel tube (CFT) columns can be considered as an attractive solution to construct such ductile soft-stories. To validate this concept, the multi-axis substructure testing (MAST) system at Swinburne University of Technology is used to conduct a set of 3D quasi-static cyclic tests on CFT columns with both circular (CCFT) and square (SCFT) cross-section shapes. A combination of bidirectional horizontal load protocol with vertical load variation is applied to the specimens. The data obtained from these experiments are used to study the physical damage progression and hysteresis response of CCFT and SCFT columns under complex 6-DOF boundary forces. The obtained experimental data are then used to calibrate FE numerical models to conduct performance-based fragility analysis of the soft-story buildings, at the system level, and vulnerability assessment of CFT columns, at the component level. The results show confidence in the superior seismic performance of CFT columns and highlight the advantages of using these elements in the construction of seismic resilience and sustainable buildings.

Prediction of the Incipient Motion of Sediment Entrainment via a Novel Hybrid Geno-Fuzzy Approach with Experimental Investigations

AbstractThe current state of the art on how the circular cross-section shape of a rigid boundary channel affects the incipience of sediment entrainment is not well investigated in the literature. M...

Effect of fibre cross-sectional shape on bending behaviour of yarns and fabrics; part I

To study the effect of fibre cross-sectional shapes on the bending behaviour of continuous multifilament polyethylene terephthalate (PET) yarns and corresponding fabrics, a circular cross-sectional shape has been taken as reference shape. To mimic the natural fibres in different ways, the cross-sectional shape is an important parameter in this regard. Different cross-sectional shapes like circular, trilobal, rectangular, plus, double flange dumble shape, octagonal, hexalobal, square and trilobal plus or Y-shape were selected for the study. The linear density of single filament and yarn were kept constant (i.e. 76/48/0) in all cross-sectional shapes. The area of cross section was approximately constant for all shapes. The theoretical bending rigidity was calculated for all cross-sectional shapes about its neutral axis. The experimental BR ratio concerning reference circular cross section of fibre was compared with the theoretical BR ratio. It is assumed that individual filament is free to bend in fibre assembly having zero twists. All yarns were converted to fabric having constant areal density. The yarn bending behaviour is compared with fabric bending behaviour to study the effect of cross-sectional shapes on bending behaviour.

Prediction of scour around single vertical piers with different cross-section shapes

In the present work, a 3D numerical model is proposed to study local scouring around single vertical piers with different cross-section shapes under steady-current flow. The model solves the flow field and sediment transport processes using a coupled approach. The flow field is obtained by solving the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations in combination with the k-w SST turbulence closure model and the sediment transport is considered using both bedload and suspended load models. The proposed model is validated against the empirical measurements of local scour around single vertical piers with circular, square, and diamond cross-section shapes obtained from the literature. The measurement of scour depth in equilibrium condition for the simulations reveal the differences of 4.6%, 6.7% and 13.1% from the experimental measurements for the circular, square, and diamond pier cases, respectively. The model displayed a remarkable performance in the prediction of scour around circular and square piers where horseshoe vortices (HSVs) have a leading impact on scour progression. On the other hand, the maximum deviation was found in the case of the diamond pier where HSVs are weak and have minimum impact on the formation of local scour. Overall, the results confirm that the prediction capability of the present model is almost independent of the strength of the formed HSVs and pier cross-section shapes.

Size-dependent vibration and dynamic stability of AFG microbeams immersed in fluid

This paper analyzes the size-dependent vibration and dynamic stability for axially functionally graded (AFG) microbeams immersed in fluid. We consider rectangular and circular cross-section shapes of AFG microbeams. The modified couple stress theory (MCST) is employed to characterize the size dependency of microbeams. The Mori-Tanaka method provides the formulations of material properties with axially continuous gradual variation. The fluid effect on the microbeam is simulated as the added mass. According to the variational principle, we can obtain the governing equations and the boundary conditions of the free vibration and dynamic stability problems. The natural frequency and critical excitation frequency are solved by the differential quadrature (DQ) method and iterative method. Numerical examples present the response of the natural frequency, critical buckling load and critical excitation frequency on the fluid depth, size parameter, fluid density and cross-section shape.