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In this paper, a geometrical investigation of the star sensor image is performed under dynamic conditions where the angular velocity effects are non-negligible. It is shown that, when the spacecraft is rotating, the streaks left by the stars’ signal onto the star sensor detector belong to portions of conic sections which features depend on the angles between the instantaneous rotation axis, the sensor line of sight and the stars’ direction. The geometrical properties discussed in the first part of the paper can be used to develop new numerical methods for the evaluation of the angular velocity. Hence, the chord method is proposed and discussed. This approach needs at least two stars in two successive images and, despite its simplicity, is quite effective to get a preliminary estimation of the spacecraft angular velocity in terms of direction and magnitude. Using the stars’ centroids from two successive images, the chord method evaluates the angular velocity direction as the intersection of the normals to the streaks. The proposed method is firstly presented by means of simple examples using some reference geometries, and then it is applied to real scenarios by using a high fidelity star sensor simulator. The pre-processing and processing of simulated images are discussed, presenting the geometrical techniques used to cluster the streaks and compute the centroids. Results are presented and discussed, validating the reported theoretical speculations.

Wind tunnel testing is conducted on a NACA0015 airfoil with a rounded trailing edge, known as a circulation control airfoil, at the chord Reynolds number of 1.10×105 and at the angles of attack of ...

When there is a sudden loss of load carrying element in a structure, the structure will choose alternate load paths until equilibrium is reached. In this process, elements overloaded in the alternate load paths fails, leading to a large damage disproportionate to the initial event which is referred to as Progressive Collapse (PC). Fire, gas explosions, terrorist attacks, car crashes, and improper design and construction are all common causes of progressive collapse. As a result, it is important to research and examine the effects of this phenomena on structures, as well as to reconstruct the structure to be resistant to it. Government buildings, hotels, offices and residential buildings require different spacings and may require large spans. Though lot of research work has done on PC resistance of Reinforced Concrete (RC) structures to explore that research, in this study, RC buildings with 4 m, 6 m and 8 m clear span between columns have taken and linear static analysis (LSA) has done for different column removal conditions. PC resistance is measured in terms of vertical joint displacement (VJD), chord rotation (CR) and demand capacity ratio (DCR). The VJD and CR results are discussed and compared with each other. The calculated CR values and DCR values are compared with the limiting value as mentioned in GSA and DoD. The tendency to PC is more for 8 m span model is more than the other models with 6 m and 4 m.

In high-speed CNC (compute numerical control) machining, the feedrate scheduling has played an important role to ensure machining quality and machining efficiency. In this paper, a novel feedrate scheduling method is proposed for generating smooth feedrate profile conveniently with the consideration of both chord error and kinematic error. First, a relationship between feedrate value and chord error is applied to determine the feedrate curve. Then, breaking points, which can split whole curve into several blocks, can be found out using proposed two step screening method. For every block, the feedrate profile based on Sigmoid function is generated. With the consideration of kinematic limitation and machining efficiency, a time-optimal feedrate adjustment algorithm is proposed to further adjust feedrate value at breaking points. After achieving feedrate profile for each block, all blocks’ feedrate profile will be connected smoothly. The resulting feedrate profile is more concise compared with the polynomial profile and more efficient compared with the trigonometric profile. Finally, simulations with two free-form NURBS curves are conducted and comparison with the sine-curve method is carried out to verify the feasibility and applicability of the proposed method. In order to further validate the feasibility of proposed method, machining simulation experiments are also conducted using Unigraphics NX.

The geometric agreement, commonly hailed as load-transferring paths within bridge structures, is significantly crucial to the bridge structural mechanical performance, such as capacity, deformation, and collapse behavior. This paper presents a methodology dependent on alternative load paths to investigate the collapse behavior of a double-pylon cable-stayed bridge with steel truss girders subjected to excess vehicle loading. The cable-stayed bridge with steel truss girders is simplified using a series-parallel load-bearing system. This research manifests that the enforced vehicle loading can be transferred to alternative paths of cable-stayed bridges in different load-structure scenarios. A 3-D finite element model is established utilizing computer software ANSYS to explore the collapse path of cable-stayed bridge with steel truss girders, taking into account chord failure, loss of cables together with corrosion in steel truss girders. The results show that chord failures in the mid-portion of the mainspan result in brittle damage in truss girders or even sudden bridge collapse. Further,the loss of long cables leads to ductile damage with significant displacement.The corrosion in steel truss girders has a highly slight influence on the collapse behavior of cable-stayed bridge. The proposed methodology can be reliably used to assess and determine the vulnerability of cable-stayed bridge with steel truss girders during their service lifetime, thus preventing structural collapses in this type of bridge.

In the present work, the aerodynamic design of a 10 kW horizontal axis wind turbine rotor is performed using both ideal and actual rotor theories. The obtained nonlinear blade profile is optimized in order to enhance the aerodynamic performance and to ease the fabricating complexity. A unique linearization approach is employed to linearize the chord and twist distribution by dividing the congruent line of both ideal and actual models into equal divisions. The points along the identical tangent line are considered as floating new blade roots, whereas the blade tip was kept fixed based on the primary design. The linear profile based on the new value of blade root is described using algebraic equations. The local element torque, capacity factor, and the annual energy production based on the Weibull distribution are adopted to determine and assess the optimal blade profile. Both CFD investigation and the FEA analysis are performed in order to evaluate both primary and optimized blades. The aerodynamic and aeroelastic comparison in terms of power output, thrust force, blade tip deflection, and the equivalent stress distribution of both blade profiles has been done over a wide range of incoming wind speeds. Results show an enhancement in the aerodynamic performance in terms of power coefficient up to (5.9%) compared to the primary blade design. Moreover, the optimized blade has shown less tip deflection by 27.92% than the primary blade at low wind speed.

Combination-chord model (CCM), specially designed to broaden the range of rail corrugation measurement, still faces two troubles including the measuring point deviation and the inverse filter parameters optimization. In this paper, a triple-line structured-light vision (SLV) based CCM is introduced to address these issues. Two solutions respectively for rectification of the measuring points deviation and optimization of the inverse filter parameters are presented. The former, based on the horizontal spacing constraint, detects the exact measuring point from a true rail profile which is reconstructed and rectified by the triple-line SLV. The latter, based on the minimum cumulative recovery error, defines the optimized numbers of frequency sampling and filter order, together with a splicing wavelength. Employing these optimized parameters, our CCM yields the overall amplitude-frequency response being nearly one whether for longwave corrugation or for shortwave corrugation. Both of the proposed solutions aim at enhancing the ordinary CCM in terms of the validity for rail corrugation measurement. Experimental assessments verify the availability and repeatability of our scheme.

Simulations of gas–liquid turbulent flows in helically coiled tubes are conducted by a two-fluid hydrodynamic model coupled with the population balance equation. A model of bubble breakup in a turbulent flow, recently developed by the authors, is incorporated into the ANSYS Fluent CFD code employed as a computational tool. The population balance equation is solved by a discrete method. A realizable k-epsilon turbulence model is used for all computations. Numerous simulations of gas-liquid flows in vertically oriented coiled tubes are conducted. Three different coil diameters are employed for simulations. Computed bubble chord distributions are close to experimental data. Simulated dependencies of the superficial liquid velocity on the superficial gas velocity, corresponding the bubbly-intermittent flow regime transition, are in excelled agreement with measured ones. On the other hand, dependencies, obtained using standard bubble breakup models, significantly deviate from experimental results. Thus, it is demonstrated that employment of the novel bubble breakup model greatly enhances a computational accuracy of gas-liquid flows in helically coiled tubes.

The kinetic energy loss and the secondary loss downstream of a high turning nozzle cascade were investigated. Influence of the incidence angle (i= −25°, 0° and 25°) and Reynolds number (Re2,is =0.8×105, 1.2×105, 2.5×105 and 4.5×105) were studied on two cascade configurations defined by different pitch to chord ratio (t/c=0.6 and 0.9), respectively. Measurements at the cascade inlet were performed by means of Preston tube, while at the cascade outlet by means of miniature pyramid five-hole pressure probe. An effect of studied parameters on the flow field at the cascade outlet was shown by the distribution of the kinetic energy loss, secondary loss, mix-out loss and streamwise vorticity.

Consider a convex body D in ℝn. We obtain an explicit formula expressing the distribution function of the distance between two random points uniformly and independently chosen in D in terms of the distribution function of the length of a random chord of D. As a corollary, we derive Kingman’s formula which connects the moments of these distributions.

The fan installed in the outdoor unit of air-conditioning (AC) systems is often partially shrouded to increase the inlet area and allow the installation of a larger upstream heat exchanger. However, the effect of radial inflow from the unshrouded part on the aerodynamic performance of the fan is seldom studied. The current paper studies the flow structure in a partially shrouded fan to understand the effects of radial inlet flow on the main flow and the flow in the tip region. The results showed that the flow from the unshrouded region has the same scale as the axial inflow in a partially shrouded fan. The flow field and tip leakage vortex development in the partially shrouded fan are substantially different and the loss corresponding to the TLV is intensified compared to the fully shrouded one. In a partially shrouded fan, the TLV rolls up adjacent to the tip section due to the interaction with radial inflow and follows the tip chord in the unshrouded part. The TLV then moves away from the suction surface in the shrouded part inducing a large blockage and loss at the fan outlet. A vortex street is created outside the fan by the exiting TLV which restricts the main flow from radial expansion and increases the fan backpressure. The reverse flow near the shroud is mainly driven by the TLV and can be controlled by changing the TLV trajectory.

The present work deals with the improvement of the seismic performance of a Single Story-Single Bay Special Truss Moment Frame (STMF) by incorporating Shape Memory Alloys (SMAs) as dissipation devices in the special segment, which can recover their initial geometry after mechanical distortion by unloading through the phase transformation (martensitic-austenitic phase). STMFs were initially designed with a special segment located in the middle of the truss to dissipate the input energy through the formation of plastic hinges at the four corners of the chord members. This mechanism is replaced with the input energy dissipation through the SMA deformation in a pin-ended special segment. In what follows, the frame at hand is examined incorporating SMA bars per diagonal of either 0.025 m or 0.035 m in diameter, restrained against buckling, simulated via a 4-DOF mechanical model consisting of two lumped masses, under selected ground motions. To further evaluate the performance of the frame with SMAs incorporated and at the same time verify the model, a non-linear dynamic time-history analysis is conducted using SeismoStruct Finite Element software. The response of the proposed system is compared with the one of the conventional one. Results show that the proposed system leads to a decrease of the maximum displacement and potentially allows a much lighter construction.

Two types of aluminum alloy mega-latticed structures were generated through ANSYS to investigate the suitable material and form for super-long span spatial structures. The joint stiffness of the structures was first discussed, and a proper simulation method for the joints was proposed. Subsequently, the analysis of these two structures with spans from 800 m to 1200 m was conducted by emphasizing the peculiar differences with steel ones, based on the mechanical performance and economic indices. Also, the reasons for these differences were analyzed in detail. It was found that both structures had good mechanical performance, but the aluminum alloy structures had much better economic indices for spans greater than 1000 m. The material consumptions of the aluminum alloy structures were 1/3–1/7 of those of the steel structures at spans from 800 m to 1200 m. The aluminum alloy structures are more sensitive to wind but less sensitive to node imperfections than the steel structures. To further explore the applicability of aluminum alloy structures, the static and stability performance of structures with spans of 1600 m and 2000 m were analyzed. This showed that these super-long span structures could have excellent mechanical performance. Finally, four key structural parameters, namely support conditions, sections of the 3D trussed beams, sections of the chord members, and rise-span ratios, were examined. The influences of these parameters were thereby identified, and some reasonable values of these parameters were obtained. This work may provide a reference for the design and application of aluminum alloy mega-latticed structures.

This paper presents the results of an original experimental study on the training capacity of a powder metallurgy (PM) FeMnSiCrNi shape memory alloy (SMA). The specimens were sintered under protective atmosphere from blended elemental powders, 50 vol.%. of alloy particles being mechanically alloyed. Lamellar specimens, hot rolled to 1 mm thickness, were bent against cylindrical calibres with five decreasing radii, to induce cold shapes with higher and higher deformation degree, as compared to the straight hot shape. During the training procedure, bent specimens were heated with a hot air gun, and developed free-recovery shape memory effect (SME) and partially deflected, by reducing their curvature. The first set of experiments involved fastening the specimens at one end, heating it and monitoring free end’s displacement by means of cinematographic analysis. Within the second set of experiments, both cold and hot shapes were recorded and digitalized and their chord’s length (b) and circle segment height (a) were measured and the radius was determined as R = a/2 + b2/8a for the cold (Rc) and hot shapes (Rh). Finally, the shape recovery degree was calculated for the nth calibre as Δrecn = (Rhn-Rrn)/(Rhn-1-Rrn) and the variation of Δrecn with calibre’s radius was discussed.

This study tests the respective roles of pitch-class content and bass patterns within harmonic expectation using a mix of behavioral and computational experiments. In our first two experiments, participants heard a paradigmatic chord progression derived from music theory textbooks and were asked to rate how well different target endings completed that progression. The completion included the progression’s paradigmatic target, different inversions of that chord (i.e., different members of the harmony were heard in the lowest voice), and a “mismatched” target, a triad that shared its lowest pitch with the paradigmatic ending but altered other pitch-class content. Participants generally rated the paradigmatic target most highly, followed by other inversions of that chord, with lowest ratings generally elicited by the mismatched target. This suggests that listeners’ harmonic expectations are sensitive to both bass patterns and pitch-class content. However, these results did not hold in all cases. A final computational experiment was run to determine whether variations in behavioral responses could be explained by corpus statistics. To this end, n-gram chord-transition models and frequency measurements were compiled for each progression. Our findings suggest that listeners rate highly and have stronger expectations about chord progressions that occur frequently and behave consistently within tonal corpora.

For lessening the weight and volume of flow control system, enlarging the circulation control applying area of angle of attack (AOA), and achieving nice controlling characteristics, a novel lift enhancement method based on dual synthetic jet actuators (DSJAs) and synthetic jet actuator (SJA), and an adaptive proportional integral and differential (PID) algorithm based on radial basis function neural network are introduced. DSJAs are uniformly located along the chord to suppress the separation and trailing-edge SJA is applied to achieve the high circulation. Velocities of actuators are modulated to realize the real speed profile and on–off controlling laws of DSJAs are designed. Numerical simulations show that DSJAs and SJA could suppress the separation completely and move leading-edge stagnation point and trailing-edge separation point downstream even at AOA of 19°, hence achieve the highest lift and nose-down moment augmentation ( $${\Delta {Cl}}_{\text{max}}$$ = 0.92, $${\Delta {Cm}}_{\text{max}}$$ = 0.02534), and $$\Delta L/D$$ can reach 11.39 at AOA of 18°. Stalling is delayed to more than 19°. Linear lift area and pitch-break angle are both increased to 16°. $$\Delta {Cl}/{C}_{\mu }$$ can reach 76.7, indicating the greatest control efficiency. The results of adaptive PID control, whose controlling effects are proved better than PID, indicate that lift could track the objective with the rise time of 0.0325 s and finally keep steady, suggesting the nice stability and rapidness.

The aim of this study is to reveal the influence mechanism of endwall air injection with distributed holes on the corner separation of a highly loaded compressor cascade, so as to promote the application of injection in aero-engines. Single-hole and double-hole endwall injection schemes featuring different axial locations, pitchwise locations, injection mass rates and injection directions, were designed and investigated. Results showed that the corner separation was eliminated by endwall injection; the optimal single-hole injection scheme achieved an endwall loss coefficient reduction of 29.7%, with injection coefficient as low as 0.48%. The optimal axial location of single-hole endwall injection was at 82% axial chord, being the center of corner separation. However, as injection hole was located at upstream of it, endwall injection resulted in severer corner separation. The mid-span flow field was deteriorated after endwall injection, which was due to 3D flow effects, i.e., AVDR (axial velocity density ratio) effect and low-momentum fluid spanwise migration effect. The optimal injection was achieved at low injection angle and from close to the suction surface on pitchwise. Double-hole injection exhibited inferior performance compared with single-hole, which was due to the interaction of the two injection streams and mixing of injection streams with the bulk stream.

Atrial septal defect (ASD) is a common congenital defect that leads to various hemodynamic complications if untreated. Transcatheter closure (TCC) of isolated secundum ASD is the preferred treatment. Herein we describe a unique malaligned ASD secondary to a membranous chord. With balloon sizing and intracardiac echocardiography (ICE), TCC was successfully pursued. (Level of Difficulty: Beginner.), Central Illustration

The high performance of aero-engines requires light-weight aero-engine blades, so hollow structures have been widely used in aero-engine blades. At present, the measurement of aero-engine blades is mainly carried out with coordinate measuring machines (CMM). This method can measure most of the aero-engine blades through direct contact. However, the complex surface, the chord width, and the large torsion of the profile of a hollow blade lead to measurement difficulties. In addition, the surface contact machining characteristics of belt grinding largely depend on the known data of the detected surface, so the CMM cannot efficiently obtain the belt grinding allowance data of a hollow blade and the application of hollow blades is limited in aviation. In this paper, a new method of obtaining belt grinding allowance data of a hollow blade based on blue light scanning was proposed according to complex surface structural characteristics of a hollow blade and surface contact characteristics of belt grinding. The point cloud information of a hollow blade was obtained through blue light there-dimensional scanning and then matched with an improved ICP algorithm considering the curvature change of the hollow blade, so as to obtain the belt grinding allowance of the hollow blade. Finally, the measurement method was verified by the belt grinding experiment with the hollow blade. The experimental results confirmed that the improved ICP algorithm was more accurate and that the measurement method could obtain the allowance data of the hollow blade.

In trusses, deck type and through type truss systems are generally provided with various member arrangements. To utilize the materials used in the trusses more efficiently, RCC decks are nowadays made composite with the truss members. In this paper, analysis of 72.0 m deck type and through type, non-composite and composite bridges is presented. The bridges are modelled using STAAD. Pro v8i software with truss members as beam element and deck slab modelled as four noded plate element. The loading on the bridge is done as per the provisions of IRC-6 and IRC-24. The composite deck effectively reduces the horizontal deflections due to lateral seismic and wind loads in both the truss systems. Decrement in vertical deflection of the truss system was also observed making the structure mode stiffer. Stresses in the members made composite with the deck slab were also reduced and hence resulted in material saving and decreased steel offtake. In the case of composite deck type bridges due to load sharing by the deck slab, the stresses in the top chord are reduced significantly hence eliminating the chances of buckling. Advantages of composite deck are better utilized in deck type bridge system compared to through type bridge system.

In this paper, a constructive description of Holder classes of functions on certain compact sets in $${{\mathbb{R}}^{m}}$$ (m $$ \geqslant $$ 3) is given in terms of the rate of approximation by harmonic functions in shrinking neighborhoods of these compact sets. The compact sets under consideration are a higher-dimensional generalization of compact subsets of curves in $${{\mathbb{R}}^{3}}$$ whose arc is commensurable with chord. The neighborhood size is directly connected with the rate of approximation: it shrinks when the approximation is getting more accurate. In addition to being harmonic in the neighborhood of the compact, the approximating functions are subject to the condition that looks similar to the Holder condition, but is weaker. Namely, the difference in values at two points is estimated in terms of the size of the neighborhood, if the distance between these points is commensurate with the size of the neighborhood (and thus estimated in terms of the distance between the points).

Centrifugal regulators have become widespread in various fields of mechanical engineering and instrumentation for regulating and measuring the speed of mechanisms and motors. The most fundamental studies in this field are the works of N.E. Zhukovsky, I.O. Vyshegradsky, A. Stodola, and others. In the further development and generalization of the theory of centrifugal regulators acquired in the work of L.M. Tsukernik. For wind turbines, G.H. Sabinin proposed a centrifugal regulator scheme for weather vane control ГС-4 and was implemented in a number of installations, namely BЭ-2, BЭ-3, BЭ-5. A number of studies of such control systems were conducted at the Storm Design Bureau at NTUU KPI, and later at the Institute of Electrodynamics of the National Academy of Sciences of Ukraine. The Institute of Renewable Energy proposed an improved scheme of the ГС-4 regulator and a corresponding mathematical model, namely, a variable angle between the blade chord and the axis of moment of inertia of centrifugal weights was introduced (in the ГС-4 regulator it was constant and was 90°). If at the beginning of the development of wind power, technological capabilities made it possible to obtain a trapezoidal blade shape without geometric twisting of the chord (or with insignificant up to 4°...5°), then in mathematical models it was legitimate to assume that the direction of the moment of inertia of the blade coincides with the chord of the blade. Today, the trend in the manufacture of a blade is aimed at obtaining the maximum utilization of wind energy by the rotor and, accordingly, the maximum approximation of the real blade profile to the calculated one. That is, in modern blades, blade expansion from end to butt is used in the range from 1:2 to 1:4, and the twisting of the chordi of the blade reaches 30°. Considering all this, it can be stated that the deviation of the direction of the moment of inertia of the blade from the chord of the blade can be up to 20°. Therefore, without taking into account this angle, the mathematical models of the centrifugal controller are not perfect enough. In this paper we propose a mathematical model of the centrifugal regulator of the wind turbine rotor taking into account the angle between the vector of the moment of inertia of the blade and its chord, which allowed to obtain a refined expression for the static characteristics of the regulator speed of the wind turbine rotor. Bibl. 11, fig. 1.

Intelligent and accurate determination of the position and orientation, or pose, of a workpiece which is manually placed is essential for automating fabrication tasks such as welding. In this paper, a novel algorithm based on minimizing the area of a boundary enclosing partial scan data points is proposed for detecting both the pose and assembly of tubular joints with the aid of reference ideal models. The proposed algorithm can also be applied to tubular joints with non-cylindrical cross sections. The fit-up information obtained can be used to determine whether realignment is required or combined with the pose information to re-plan paths for subsequent tasks. The focus of existing state-of-the-art is on objects with features, and the localization of featureless objects such as generic tubular joints using partial and sparse scan data remains a challenge. The proposed algorithm is applied to an actual robotic welding system to locate a tubular workpiece. Experiment results using the scan data as ground truth show that root mean square error is less than 1% of the pipe diameters, considering both brace and chord components with diameters greater than 200 mm.

Purpose The main purpose of this paper is to investigate the effects of icing on unmanned aerial vehicles (UAVs) at low Reynolds numbers and to highlight the differences to icing on manned aircraft at high Reynolds numbers. This paper follows existing research on low Reynolds number effects on ice accretion. This study extends the focus to how variations of airspeed and chord length affect the ice accretions, and aerodynamic performance degradation is investigated. Design/methodology/approach A parametric study with independent variations of airspeed and chord lengths was conducted on a typical UAV airfoil (RG-15) using icing computational fluid dynamic methods. FENSAP-ICE was used to simulate ice shapes and aerodynamic performance penalties. Validation was performed with two experimental ice shapes obtained from a low-speed icing wind tunnel. Three meteorological conditions were chosen to represent the icing typologies of rime, glaze and mixed ice. A parameter study with different chord lengths and airspeeds was then conducted for rime, glaze and mixed icing conditions. Findings The simulation results showed that the effect of airspeed variation depended on the ice accretion regime. For rime, it led to a minor increase in ice accretion. For mixed and glaze, the impact on ice geometry and penalties was substantially larger. The variation of chord length had a substantial impact on relative ice thicknesses, ice area, ice limits and performance degradation, independent from the icing regime. Research limitations/implications The implications of this manuscript are relevant for highlighting the differences between icing on manned and unmanned aircraft. Unmanned aircraft are typically smaller and fly slower than manned aircraft. Although previous research has documented the influence of this on the ice accretions, this paper investigates the effect on aerodynamic performance degradation. The findings in this work show that UAVs are more sensitive to icing conditions compared to larger and faster manned aircraft. By consequence, icing conditions are more severe for UAVs. Practical implications Atmospheric in-flight icing is a severe risk for fixed-wing UAVs and significantly limits their operational envelope. As UAVs are typically smaller and operate at lower airspeeds compared to manned aircraft, it is important to understand how the differences in airspeed and size affect ice accretion and aerodynamic performance penalties. Originality/value Earlier work has described the effect of Reynolds number variations on the ice accretion characteristics for UAVs. This work is expanding on those findings by investigating the effect of airspeed and chord length on ice accretion shapes separately. In addition, this study also investigates how these parameters affect aerodynamic performance penalties (lift, drag and stall).

Purpose Aircraft wings, one of the most important parts of an aircraft, have seen changes in its topological and design arrangement of both the internal structures and external shape during the past decades. This study, a numerical, aims to minimize the weight of multilaminate composite aerospace structures using multiobjective optimization. Design/methodology/approach The methodology started with the determination of the requirements, both imposed by the certifying authority and those inherent to the light, aerobatic, simple, economic and robust (LASER) project. After defining the requirements, the loads that the aircraft would be subjected to during its operation were defined from the flight envelope considering finite element analysis. The design vector consists of material choice for each laminate of the structure (20 in total), ply number and lay-up sequence (respecting the manufacturing rules) and main spar position to obtain a lightweight and cheap structure, respecting the restrictions of stress, margins of safety, displacements and buckling. Findings The results obtained indicated a predominance of the use of carbon fiber. The predominant orientation found on the main spar flange was 0° with its location at 28% of the local chord, in the secondary and main web were ±45°, the skins also had the main orientation at ±45°. Originality/value The key innovations in this paper include the evaluation, development and optimization of a laminated composite structure applied to a LASER aircraft wings considering both structural performance and manufacturing costs in multiobjetive optimization. This paper is one of the most advanced investigations performed to composite LASER aircraft.

We present an analytical model for assessing the aerodynamic performance of a wind turbine rotor through a different parametrization of the classical blade element momentum (BEM) model. The model is named the Radially Independent Actuator Disc (RIAD) model, and it establishes an analytical relationship between the local thrust loading and the local power, known as the local-thrust coefficient and the local-power coefficient respectively. The model has a direct physical interpretation, showing the contribution for each of the three losses: wake rotation loss, tip loss and viscous loss. The gradient for RIAD is found through the use of the complex step method, and power optimization is used to show how easily the method can be used for rotor optimization. The main benefit of RIAD is the ease with which it can be applied for rotor optimization and especially load constraint power optimization as described in Loenbaek et al. (2021). The relationship between the RIAD input and the rotor chord and twist is established, and it is validated against a BEM solver.

Understanding the dynamic behavior of tubular members is necessary for ensuring their safety, even when damaged after an impact. A nonlinear finite element analysis (FEA) was performed to evaluate the residual bearing capacity of axially preloaded square hollow section (SHS) T-joints subjected to impact loading. First, the Bao–Wierzbicki fracture criterion was used to simulate the failure modes and behavior of specimens subjected to static axial compression and impacts, and the numerical results were compared with experimental results in the literature. The bearing capacity error between the numerical and experimental results was within 10%, which verified the accuracy of the finite element (FE) model. Then, the local and global displacements of joints were distinguished with the central line displacement method, and 40 FE models were created. The dynamic responses of joints under impact loading were used to study the resistance mechanism. Joint deformation mainly manifested as outward buckling of the chord webs and indentation of the chord upper flange. The in-plane restraint and support by the brace of the chord increased with the brace–chord width ratio. Finally, the ultimate residual bearing capacity coefficient ψ was defined as the ratio of the ultimate bearing capacities of the impacted and reference specimen, and the influence of different parameters, including axial preloading, impact energy, brace–chord width ratio, and chord diameter, was explored. Axial preloading and impact energy showed a negative correlation with ψ, while the brace–chord width ratio and chord diameter showed a significant positive correlation with ψ.

The analysis presented in the paper explains computational issues related to the use of a new method of determining the curvature of the track axis – the so-called moving chord method. It indicates the versatility of this method – it may be used both in a horizontal and vertical plane. It also draws attention to its very high precision, as evidenced by the exemplary geometric cases under consideration. The focus here is on the computational foundations of the discussed method regarding the angles of inclination of the moving chord. It was found that for a circular arc in the horizontal plane, the inclination angles of the moving chord depend on the track turning angle, while the difference in inclination angles depends only on the radius of the arc. In the case of a circular arc in the vertical plane, the moving chord inclination angles are much smaller than in the horizontal plane, which is connected with the range of the applied radii of the arcs. As in the horizontal plane, the radius of the vertical curve is the only factor that determines the discrepancy in the inclination angles of the moving chord.

Grid fins are normally placed at the rear end of cruise missiles, rockets and other ballistic devices to control their trajectory especially at the final stage of flight. These fins provided fine control of the pitch, yaw and other lateral movements, allowing for higher stability and accuracy of the cruise missiles. This project investigates computationally the relation between grid fins inner lattice structures dimensionless parameters and the fins aerodynamics drag coefficient. The project gathered data from 12 different fins by varying the parameters of its internal lattice structure such as thickness, width and chord at various angles of attack (0°, 20° and 40°). The freestream was set at a constant speed of 150 m/s that gives Reynolds number > 1.7 x 106 . The results were experimentally compared by using a re-scaled model of a single fin in a sub-sonic wind tunnel, achieving a difference in results of not exceeding 6%. The results obtained that as the width-chord ratio increases, the aerodynamics drag coefficient increases for fixed thickness-width ratio. The results also demonstrated that as the angle of attack increases, the aerodynamics drag increases. The thickness-width ratio has the larger impact on the aerodynamics drag. The results can be used to improve the design of guided cruise missiles.

In order to study the influence of the axial compression ratio and steel ratio on the shear-carrying capacity of steel-truss-reinforced beam-column joints, five shear failure interior joint specimens were designed. The effect of different coaxial pressure ratios (0.1, 0.2, and 0.3) and steel contents on the strain, ultimate bearing capacity, seismic performance, and failure pattern of cross-inclined ventral and chord bars in the joint core area was investigated. The experimental results show that the load-displacement hysteretic curves of all test specimens exhibit a bond-slip phenomenon. With the increase of the axial compression ratio, the ultimate bearing capacity of the joint core increases by 3.4% and 5.9%, respectively. While the ductility decreases by 10.3% and 13.1%, and the energy consumption capacity decreases by 3.2% and 5.8%, respectively. The shear capacity and ductility of the member with cross diagonal ventral steel angle in the joint core are increased by 12.9% and 13.4%, respectively. The shear capacity and ductility of the joint can be significantly improved by increasing the amount of steel in the core area. The expression of shear capacity suitable for this type of joint is obtained by fitting analysis, which can be used as a reference for engineering design.

Use of composite RCC deck over steel bridges has now significantly increased. The detailed experimental study was conducted to ascertain improvements due to composite RCC deck over non-composite bridge model. Deck type steel bridge models, with and without composite decks were tested in laboratory up to failure. The failure in non-composite model was observed due to buckling of top chord member at a stress of 234.6 N/mm2, whereas for the model with composite deck it changed to rupture of the bottom chord in tension at a stress of 614.8 N/mm2. Failure load and stiffness of the structure also increased significantly due to the composite action. Shear connectors designed as per IRC 22:2008 transferred the shear effectively and deck slab also participated in load sharing. Further, load sharing in the top chord compression member comprising the steel top chord, the concrete in the deck slab, and the reinforcing steel in it, was also explored. It is found that 72.0% of the composite top chord compressive force is taken by the RCC deck, and in the RCC deck 30.7% force is taken by the reinforcement. Strain variation in deck slab was also recorded using strain gauges. Strain in deck slab over top chord members was observed to be 54% more than the strain in the middle of the deck slab.

The present study demonstrates experimental mitigation of Tollmien–Schlichting waves on an unswept natural laminar flow airfoil at a chord-based Reynolds number of 9.90×105. This was facilitated by...

In the literature, provisions for analysis and design of steel-RCC composite deck type truss and cable-stayed bridges do not exist. A composite deck type truss bridge model is analyzed using STAAD Pro V8i software and a model with the same dimensions is tested in the laboratory. The experimental test results are used to validate the STAAD analysis results. Bottom chord strain and mid-span deflection of the composite bridge model as found from the STAAD analysis and the laboratory experiment closely tally with each other. This validates the standard STAAD analysis results. However, in the top chord member, due to shrinkage cracks in the deck slab concrete, the experimentally recorded strain is higher by about 100% than the STAAD analysis result. Shear force in studs is considerably large near supports and joints as compared to the midsection. Therefore, the design of shear studs may be carried out based on the shear forces in the studs found from the STAAD analysis. Thus it is recommended that STAAD or any other standard finite element analysis software can be used for analysis and design of the composite bridges.

With a higher requirement on machining accuracy in electrical discharging machining (EDM), there is a drastically increased number of multi-axis line segments for machining complex workpieces. High speed jumping is needed for a conducive discharge gap status. The increased number of line segments, however, makes the implementation of high-speed jumping difficult. To alleviate the online computational burden for velocity planning, this paper proposes a multi-axis velocity planning based on a coder-player architecture. Under this architecture, a multi-axis feeding trajectory is represented by a series of double non-uniform rational B-spline (NURBS) curves, which are then interpolated by the unit arc length increment interpolation (UALII) method. Based on the interpolation points with a resolution of a basic length unit (BLU), a velocity limit curve is generated by considering simultaneously the constraints on chord error, acceleration and jerk. The velocity planning is implemented under a coder-player architecture. As a trajectory represented by a double-NURBS curve has C 2 continuity, velocity losses can be avoided at junctions between line segments, thus smoothing of line segments at junctions is unnecessary in jumping. Machining tests showed that by the use of the velocity planning based on double-NURBS curves, the machining time for one channel of a shrouded blisk can be decreased by 29.38%.

To improve the aerodynamic performance of tiltrotor aircraft, the flow characteristics of the V-22 airfoil without and with one, two parallel rows of vortex generators (VGs) were investigated using numerical simulation methods. The results were obtained with three-dimensional compressible Reynolds-averaged Navier–Stokes equations, and the turbulence was simulated with the SA-based DES model. The influence of the chordwise installation of VGs was emphatically discussed. First, the single-row VGs are, respectively, mounted at the 10, 20, and 40% chord positions, denoted as VGs1, VGs2, and VGs3. The results indicate that with the addition of the optimal configuration (VGs1), the maximum lift coefficient is extended from 1.43 to 2.44, and the stall angle of attack increases from 10° to 22° with respect to the clean airfoil. The drag coefficient of the airfoil with VGs1 is 60.8% lower than that of the airfoil without VGs at an angle of attack of 24°. On this basis, the double-row VGs’ arrangements are located at the 10 and 30% chord positions (VGs4), the 10 and 50% chord positions (VGs5) and the 10 and 70% chord positions (VGs6). Compared to single-row VGs, double-row VGs have the greater potential to suppress the flow separation. Due to the effect of VGs4, the maximum value of lift coefficient has increased to 2.61. However, the case of VGs6 degrades the overall aerodynamic performance as compared to VGs1. Further research suggest that with the increase in the height of the second row of vortex generators (VGs7), the aerodynamic characteristics of airfoil A821201 can be effectively enhanced at large angles of attack.

This study focused on the computational design and static structural analysis of a small-scale turbojet engine (SSTE) that can power an unmanned aerial vehicle with a thrust of 50 N at a speed of 8000 rpm. SOLIDWORKS 2018 was used to design the CAD geometry of the SSTE, and to carry out a CFD analysis on the compressor to determine the pressure distribution across the compressor and the compressor pressure ratio. The obtained pressure ratio was further used to carry out a structural analysis of the SSTE with emphasis on the turbine component using ANSYS static structural module. This analysis was done to determine the level of deformation of the chosen design material (stainless steel grade 310), the maximum and minimum stresses, factor of safety, and its fatigue life. Design and CFD results obtained shows that the design as well as the pressure distribution in the compressor is reliable. The 50N small scale turbojet engine showed higher optimum performance from structural design and evaluation when compared to that of the 70N thrust jet cat model. Results of the structural analysis shows that the turbine blades will experience minimum and maximum deformation of 0 m and 2.2543×10−5 m at the leading edges and trailing edges of the blade chord respectively. Also, maximum and minimumstresses will occur at 1.0632×105 Pa and 6.7192×107 Pa respectively. Conversely, the factor of safety was within 3.0807 to 15 which show that the design is adequate. Additionally, considering the fatigue life, the SSTE is bound to fail completely at approximately 1.929×107 months. Therefore, the SSTE with the materials suggested above is capable ofpropelling an unmanned aerial vehicle considering the results obtained. Keywords: Computational, static-structural, turbojet, UAV, design

In the code for design of steel structures, the effective length factor of the support and other web members of the steel trusses composed of double angle steel were taken as 1.0 and 0.8, respectively. However, the effective length factor of the support and other web members did not take into account factors such as the stiffness provided by non-adjacent members, the stiffness of the joint itself, and the influence of load changes in the code for design of steel structures. To consider the above influencing factors, a finite element model, based on the steel truss atlas, was established in Abaqus, the elastic restraint stiffness of the web member end was obtained through numerical analysis. The equation was established according to the restraints of the web member end, and the effective length factors of the web member were obtained by solving the equation with Matlab. The analysis found that the elastic restraint stiffness of the web member provided by the bottom chord would not increase by increasing the tension of the bottom chord within the range of elastic deformation. The elastic restraint stiffness of the web member provided by the top chord would not weak by increasing the pressure of the top chord within the range of elastic deformation. It was recommended that the effective length factors of the support and other web members of the steel truss should be 0.8 and 0.7, respectively.

This article presents a Python-based package, ipyChord, to compute the 2D chord distribution function (CDF) from the small-angle X-ray scattering (SAXS) pattern from polymer materials with fiber-symmetrical nanostructure. The program allows construction of a harmonized SAXS pattern from a raw SAXS pattern, by normalization of the incident-beam intensity, absorption correction for sample thickness, masking blind areas on the detector, and filling in the shadow of the beamstop and its holder using symmetry operations. Patterns from modular detectors with inter-module gaps can still be fully constructed satisfactorily after determining the optimized beam position and a radial basis function. A CDF pattern computed from the full SAXS pattern can be used to determine the domain size and its variability using a graphical method. An interface distribution function computed from Bonart's longitudinal projection or sliced from a CDF meridian can quantify differently stacked hard and soft domains. Two cases of the application of ipyChord are presented. The software is open source and available at https://github.com/isaxs/ipyChord.

Placing a diffuser around a wind turbine can increase its power output, but not all mechanisms by which the diffuser alters the aerodynamics have been investigated thoroughly. Here, we concentrate on one such mechanism: the effect of the finite number of blades. In nearly all blade element analyses of wind turbines, finite blade effects are approximated by Prandtl’s “tip loss factor” which goes to zero at the blade tip. We argue that this limiting behaviour cannot be correct for the axial velocity in the presence of a diffuser. We provide alternative “finite blade functions” which preserve the finite limit on the axial velocity, but do not alter the conventional limit of zero for the circumferential velocity. In maximizing the power output of a diffuser-augmented wind turbine, the change in the finite blade function for the axial velocity has a large impact on the power-producing region near the tip: it increases both the chord and the power output of an optimized blade. Further, the change appears to make diffuser-augmented turbine power output less sensitive to tip speed ratio than for a bare turbine.

To reduce the dedusting resistance of wet vibrating string grille precipitators during dedusting in mine ventilation roadways, we investigated the dedusting resistance characteristics of water fog and water film coupling and determined the relationship between dedusting resistance and spray pressure, vibrating grid filling rate, and wind speed. A mathematical resistance coefficient model is established using hydrodynamics theory and capillary mechanics. The theoretical relationship of dedusting resistance is deduced. The results show that when wind speed is constant, the spray pressure and dedusting resistance are higher and the resistance is smaller with a high filling rate compared with a low filling rate. Constant spray pressure allows faster wind speeds and reverse pressure gradient forces to increase when dust flows around the wet vibrating wire, which makes the pressure distribution asymmetrical around the steel wire and increases resistance. Dust removal resistance of the resonance chord with a high filling rate is substantially lower than that with a low filling rate under the same working conditions. On the basis of satisfying the dedusting efficiency, the resonance chord dedusting system does not affect normal production and resistance is low. The spray pressure is controlled at 0.3–0.7 MPa and the optimal wind speed is 3–4 m/s. According to the theoretical calculation and experimental data, the optimal filling rate of a vibrating string grid plate is 77.8%, spray pressure is 0.7 MPa, and wind speed is 3.5 m/s. Dust removal with low resistance and improved economic benefit can thus be obtained.

This paper investigates the in-plane failure mechanisms and strength of circular steel tubular Vierendeel truss arches with a rectangular section by using the finite element models. Firstly, the analytical solution for the in-plane elastic buckling load of pin-ended circular steel tubular Vierendeel truss arches with a rectangular section under a uniform radial load is obtained. Then, limiting conditions of avoiding chord local buckling before the global elastic buckling of the arch are also derived. Lastly, the in-plane instability mechanisms and failure modes of the arch under a uniform radial load, a full-span uniform vertical load (FSUVL) and a half-span uniform vertical load (HSUVL) are investigated. It is found that the arch may undergo a global failure mode or three local failure modes under FSUVL and HSUVL. Based on the theoretical and finite element results, a design equation for the global strength of arches subjected to uniform compression is proposed. Strength design equations for global failure and local failure of arches subjected to FSUVL and HSUVL are also proposed. There is a good agreement between the prediction of the proposed design equations and the FE results.

The reliability of ultrasonic testing (UST) of the quality of welded joints of polyethylene pipelines, made end-to-end with а heated tool, is considered in comparison with mесhапiсаl tests and radiography. The greatest detection of solid defects is provided bу u|trasonic inspection with the use of chord transducers (not less than 90%). When detecting defects translucent for ultrasound (lack of penetration, lack of fusion, etc.), the reliability decreases to 70–80%.

Three-dimensional flow development is experimentally assessed in a convectively unstable laminar separation bubble formed over a NACA 0018 airfoil at a chord Reynolds number of 125,000, an angle of...

Experiments were conducted to evaluate the progressive collapse resistance of a scaled partial double-layer latticed Kiewitt-6 (K6) dome in member-removal scenarios. The test results were compared with results obtained previously for a single-layer latticed dome to demonstrate the advantages of the partial double-layer members for improving the collapse resistance. A finite element (FE) analysis was also executed to confirm the experimental observations and to evaluate that the collapse-resistant behavior of a full-scale partial double-layer latticed dome. The collapse-resistant mechanism of partial double-layer domes was examined via theoretical analysis. On the basis of these results, a novel cable-stiffened partial double-layer latticed dome was proposed. The results indicated that the tested dome did not completely collapse, but some of the upper chord members buckled. For the whole dome, the compression mechanism is regarded as the major load-carrying mechanism to resist progressive collapse. In terms of the local area around the failed members, the adjacent members initially rely on the beam and compression mechanisms to resist progressive collapse. As the number of the failed members increases, the adjacent members completely rely on the beam mechanism to resist progressive collapse. The FE results agree well with the experimental results. The progressive collapse-resistant behavior of partial double-layer domes is far superior to that of single-layer domes because of the better stiffness of the partial double-layer members. The cable-reinforced partial double-layer dome is a novel structural system that has significantly better progressive collapse-resistant behavior than traditional single/double-layer and partial double-layer domes.

Purpose This paper aims to achieve an optimum flow separation control over the airfoil using a passive flow control method by introducing a bio-inspired nose near the leading edge of the National Advisory Committee for Aeronautics (NACA) 4 and 6 series airfoil. In addition, to find the optimised leading edge nose design for NACA 4 and 6 series airfoils for flow separation control. Design/methodology/approach Different bio-inspired noses that are inspired by the cetacean species have been analysed for different NACA 4 and 6 series airfoils. Bio-inspired nose with different nose length, nose depth and nose circle diameter have been analysed on airfoils with different thicknesses, camber and camber locations to understand the aerodynamic flow properties such as vortex formation, flow separation, aerodynamic efficiency and moment. Findings The porpoise nose design that has a leading edge with depth = 2.25% of chord, length = 0.75% of chord and nose diameter = 2% of chord, delays the flow separation and improves the aerodynamic efficiency. Average increments of 5.5% to 6° in the lift values and decrements in parasitic drag (without affecting the pitching moment) for all the NACA 4 and 6 series airfoils were observed irrespective of airfoil geometry such as different thicknesses, camber and camber location. Research limitations/implications The two-dimensional computational analysis is done for different NACA 4 and 6 series airfoils at low subsonic speed. Practical implications This design improves aerodynamic performance and increases the structural strength of the aircraft wing compared to other conventional high lift devices and flow control devices. This universal leading edge flow control device can be adapted to aircraft wings incorporated with any NACA 4 and 6 series airfoil. Social implications The results would be of significant interest in the fields of aircraft design and wind turbine design, lowering the cost of energy and air travel for social benefits. Originality/value Different bio-inspired nose designs that are inspired by the cetacean species have been analysed for NACA 4 and 6 series airfoils and universal optimum nose design (porpoise airfoil) is found for NACA 4 and 6 series airfoils.

This paper describes the combination of a Kriging surrogate model with a micro-genetic algorithm for studying the influence of circumferential perturbations from the stack line on the high-cycle fatigue (HCF) weak link of a fan blade in a high-bypass-ratio turbofan engine. Based on the circumferential perturbations of the fan blade stack line, an automated system is developed for the parameterized modeling and meshing of the blade, and an integral platform is established for parameterized modeling, finite-element simulation, and optimization. The static stress, index of strain energy density, and vibratory stress margin of the 1st flex mode are set as the objective functions for the optimization of a fan blade. The results show that the optimized blade has three areas of low static stress, unlike the single “bull’s eye” distribution of the baseline blade. Optimization reduces the maximum static stress by 5.87% and the strain energy density index by 0.77%, while increasing the vibratory stress margin under the same dynamic load by 9.51%. The natural frequencies, mode shapes, resonance margins, and aerodynamic parameters exhibit no significant changes, which illustrates that the optimization method can improve the static stress and vibratory stress distribution of the fan blade without negatively influencing the other vibration and aerodynamic characteristics. The proposed method is an effective means of fan blade design optimization, and could be applied alongside other design variables and objective functions, such as the swept and skewed configuration of the stack line and twist angle of the blade, to optimize the vibration characteristics and aero-elastic performance.