Strut Location Research Articles

Tomographical study of optic strut location and its significance

To determine the attachment of optic strut relative to anterior clinoid process. To categorize optic strut into the sulcal, pre-sulcal, post-sulcal. To determine the association between laterality and optic strut attachment pattern. The study was conducted on 100 normal CT scans of Head and Para nasal sinus. Optic strut was classified as pre-sulcal, sulcal, post-sulcal, and asymmetric in relation to the prechiasmatic sulcus. Optic strut location was determined as anterior, middle and posterior with respect to anterior clinoid process. The optic strut was found to be anterior in 28% specimen, middle in 57% specimen and posterior in 15% specimen. The optic strut was pre-sulcal in 31% specimens, sulcal in 50%, post-sulcal in 16%. The above were observed bilaterally, and 3% were unilateral. Anatomical variations in the optic strut are significant in planning for anterior clinoidectomy and optic-canal decompression.

A parametric study on deformation behaviour for design of braced excavation in soft clay

ABSTRACT Adequate prediction of surrounding ground movement during braced excavation is critically important as excessive soil movement damages adjacent structures. The magnitudes and patterns of ground movement and wall deflection largely depend on excavation parameters like thickness of diaphragm wall, wall embedment depth, strut locations and soil parameters such as soil strength, compressibility and creep parameter. In the present paper a thorough, parametric study has been conducted using finite element (FE) analysis to address the influence of various parameters on deformation characteristics of braced excavation in soft clayey deposits. The importance of correct estimation of soil parameters for braced excavation design is also documented. The analysis of typical braced excavations in soft clay is carried out using PLAXIS 2D software where soft soil creep constitutive model is used. On the basis of numerical study a handy design guideline is recommended. Further multivariate regression models are developed incorporating various important excavation parameters for the adequate prediction of maximum wall and ground displacement along with wall and ground surface deformation profile. Here large numbers of data reported in case histories and generated artificially from FE analysis are used for formation of regression equations. The proposed model is validated comparing results from literatures not used for the development of the model.

A methodology for estimating hypersonic engine performance by coupling supersonic reactive flow simulations with machine learning techniques

We propose a methodology used to estimate the performance of hypersonic engines by coupling some machine learning methods with a generated CFD database and one-dimensional expansion equations. The present work also investigates the effects of fuel struts geometrical parameters on the supersonic combustion which takes place in a dual-mode ramjet/scramjet engine operating at stratospheric flight conditions with a cruise speed of Mach 8. We solved 2D compressible RANS flow equations coupled with the β-pdf method using Ansys Fluent commercial code, and built a CFD database with varying three design parameters which are strut V-settlement angle, strut location, and wedge angle. The numerical code was verified/validated using the data obtained in the DLR scramjet combustor. Three main objective functions in the combustor (combustion efficiency along 14 stations having 10 cm interval between each other, averaged flow variables at exit of combustor, and total pressure recovery factor in the combustor) were selected to evaluate the struts configuration parameters effects on supersonic combustion flow physics and engine performance. These objective functions, i.e. dependent variables were regressed with independent design parameters by three machine learning techniques which are Kernel regression, Gaussian process regression, and Artificial neural network. The machine learning models of the flow variables at the combustor throat provided initial conditions for a given fuel strut configuration to the expansion solutions for the nozzle component in order to calculate the engine performance. The Artificial neural network was found the most successful technique in overall regression of the objective functions. We also discovered that the most significant design variable is the strut wedge angle for all investigated phenomena in the supersonic reactive flow field.

Выбор геометрии выходного устройства газотурбинной установки с минималь- ными потерями давления

Object and purpose of research. This paper discusses gas turbine exit unit consisting of axial-radial diffusor and pockettype volute. The purpose of the study was to select the exit unit geometry that would offer minimum losses of total pressure. Subject matter and methods. Experimental results obtained for the models of gas turbine exit units. Calculation of total pressure losses in SolidWorks package with Flow simulation extension. Correction coefficients were obtained through regression analysis. The exit unit geometry offering minimum losses of total pressure was obtained using the theory of experiment planning. Main results. The study yielded correction coefficients to the calculation results obtained in SolidWorks package with Flow simulation extension. Exit unit geometry offering minimum losses of total pressure has been successfully found. The effect of strut location in the radial part of diffusor in terms of pressure losses has been quantified. Conclusion. This study enables early identification of exit unit geometry with minimum total pressure losses, so it is valuable for practical gas turbine design.

Morphometric Analysis of Anterior Clinoid Process and Optic Strut: A Cadaveric Study

Introduction: Anterior Clinoid Process (ACP) is a bony projection on the posterior border of lesser wing of sphenoid. It is related to optic nerve, internal carotid and ophthalmic arteries. Optic strut (OS) is a bony formation located between upper side of body and lesser wing of sphenoid bone. Aim: To observe the variations in length, width of ACP and location of optic strut on right and left side in dry skulls among South Indian population. Materials and Methods: An observational study was done in the Department of Anatomy, Adichunchanagiri Institute of Medical Sciences, Mandya, Karnataka, India, from August 2021 to December 2021. Total 37 dry skulls were collected from department and also from bone sets from first year MBBS (Bachelor of Medicine and Bachelor of Surgery) students. Various parameters (length, width of ACP, distance from tip of ACP and OS, distance between tips of ACP) were measured on both sides using digital vernier callipers. Independent t-test was applied to compare the means of different groups. Results: Mean width of ACP was 14.86±4.47 mm on right side and 12.71±3.13 mm on left side (p-value 0.019). Mean length was 12.45±2.85 mm on right side and 12.05±3.11 mm on left side (p>0.05). Mean distance from tip of ACP to optic strut was 9.48±2.86 mm on right side and 9.31±3.03 mm on left side (p>0.05).Distance between the tips of ACP ranged from 27.09±28.89 mm and mean was 26.29±3.77 mm. Optic strut was located at anterior two-fifth of ACP on right side in 17 (45.95%) and on left side in 14 (37.83%) of skulls. Conclusion: There was variation in mean width of ACP on right and left side. The knowledge will help in preoperative planning and preventing unnecessary injury to neurovascular structures present in vicinity of anterior clinoid process and optic strut.

Microstructural heterogeneity of AlSi10Mg alloy lattice structures fabricated by selective laser melting: Phenomena and mechanism

Abstract The mechanical properties of metallic lattice structures fabricated by additive manufacturing depended on the microstructure heterogeneities, geometric defects and spatial location of struts significantly. This work studies the microstructural heterogeneity for inclined struts of body-centered cubic alloy lattice structures systematically. On the one hand, multiple experimental characterization methods for observing the microstructural features are carried out for searching the different phenomena in inclined strut for lattice structure with that in bulk material or vertical strut. On the other hand, a powder-scale Finite Volume Discrete Method (FVM)-Discrete Element Method (DEM) coupled model was built considering the thermal-fluid coupled behavior in inclined strut different with that in previous researches. The experimental results demonstrated that the dendritic structure size and porosity of the angle zone in the inclined struts are larger (about 5 times and 25 times, respectively) compared to those of the horizontal zone. Moreover, the surface roughness of the angle zone is larger than that of the horizontal zone in inclined struts. The powder-scale simulation results revealed the underlying physical mechanisms for the observed phenomena: The difference of the cooling rates in the horizontal and angle zones of the inclined strut leads the difference of grain size. The unstable molten flow by the competitive effects of dynamic forces induces the porosity formation in the angle zone. As a result, the value of roughness in the lower surface of inclined strut is larger than that in the upper surface. This work will facilitate the enhancement of the stability of the SLM manufacturing technique for metallic lattice structures in a robust and practical manner.

Effectiveness of servo struts in controlling excavation-induced wall deflection and ground settlement

Deformations in deep excavations can be controlled by providing adjustable support using servo struts; however, the design of strut positions and applied forces remains to be optimized. In this study, the influences of varied forces applied by servo struts on excavation-induced wall deflection and ground settlement were analyzed through numerical simulations and a field investigation. A reference numerical model and input parameters were validated using a well-documented excavation case study. Using the validated model, three servo struts were installed on a diaphragm wall at the top, middle, and bottom levels of an excavation model, and a constant force was applied on the beam elements. Comprehensive numerical simulations were carried out with various forces applied at the upper-, middle-, and lower-level struts. Both wall deflection and ground settlement were analyzed in relation to the applied force. Additionally, a field investigation was carried out at an excavation site in Hangzhou, China, where comparative analyses of applied forces and servo strut locations were performed. Both the numerical and field results confirm the effectiveness of servo struts in controlling excavation-induced wall deflection and ground surface settlement. Their effectiveness is closely related to their applied force and installation position. Wall deformation and ground settlement decrease with increases in applied force. Middle-level servo struts showed the greatest efficiency in controlling maximum wall displacement and maximum ground surface settlement.

Static and stability analyses of pretensioned latticed arch frame with integrated cable-strut arrangement

Abstract For the latticed arch frame, a new type of integrated cable-strut arrangement is proposed. The comparison analysis on the static property and stability of the new-type pretensioned latticed arch frame with the traditional ones is conducted. The rational values of the arrangement parameters of the integrated cable-strut system, such as the strut location, cable sag, intersection position of the oblique cables, and the cable pretension ratio, are obtained by optimization analysis. Also, the analysis on configuration parameters of the pretensioned latticed arch frame, such as the ratio of rise to span, latticed column height, and the cross-sectional height of the latticed arch, is investigated. Moreover, the stability of the integral structure consisting of multiple parallel pretensioned latticed arch frames with integrated cable-strut system is studied in detail. The results indicate that the vertical and lateral stiffness of the latticed arch frame can be enhanced effectively by adopting the integrated cable-strut arrangement, and thus the static property and stability can be improved significantly. The effect of the pretensioned cable-strut system on improving the structural performance increases with increase of the latticed column height gradually, but it declines with increase of the cross-sectional height of latticed arch. The buckling mode of the integral structure depends on the number of the middle longitudinal latticed 3D beams.

Evaluation of compressive properties of SLM-fabricated multi-layer lattice structures by experimental test and μ-CT-based finite element analysis

The influence of inherent imperfections should be systematically investigated to ensure the safety and utilization of additive manufacturing-fabricated multi-scale parts and structures. Herein, two different types of multi-layer lattice sandwich panels, BCC and BCCZ, are prepared by selective laser melting (SLM) using the AlSi10Mg material. X-ray micro-computed tomography (μ-CT) is employed to capture the realistic geometrical information of lattice struts. Based on the statistical characteristics, a novel finite element model is established, which considers the specific non-uniform distribution of geometrical imperfection. Uniaxial compressive tests are performed to evaluate the influence of defects and number of layers on the overall mechanical performance and energy absorption capability. The results reveal that the diameter deviation of struts is changed with the change of strut location and built angle. In terms of compressive modulus and initial crushing strength, the prediction results of the reconstruction model are consistent with experimental results as compared to the as-designed and statistical average models. The layer-by-layer crushing behavior is the main failure mode for the multi-layer lattice panels. With the increase of layers number, the densification strain and crash load efficiency increased, whereas the specific energy absorption gradually decreased due to the impact of boundary conditions and failure modes.

Does the black hole shadow probe the event horizon geometry?

There is an exciting prospect of obtaining the shadow of astrophysical black holes (BHs) in the near future with the Event Horizon Telescope. As a matter of principle, this justifies asking how much one can learn about the BH horizon itself from such a measurement. Since the shadow is determined by a set of special photon orbits, rather than horizon properties, it is possible that different horizon geometries yield similar shadows. One may then ask how sensitive is the shadow to details of the horizon geometry? As a case study, we consider the double Schwarzschild BH and analyse the impact on the lensing and shadows of the conical singularity that holds the two BHs in equilibrium -- herein taken to be a strut along the symmetry axis in between the two BHs. Whereas the conical singularity induces a discontinuity of the scattering angle of photons, clearly visible in the lensing patterns along the direction of the strut's location, it produces no observable effect on the shadows, whose edges remain everywhere smooth. The latter feature is illustrated by examples including both equal and unequal mass BHs. This smoothness contrasts with the intrinsic geometry of the (spatial sections of the) horizon of these BHs, which is not smooth, and provides a sharp example on how BH shadows are insensitive to some horizon geometry details. This observation, moreover, suggests that for the study of their shadows, this static double BH system may be an informative proxy for a dynamical binary.

Inherent limitations and alternative to conventional equivalent strut models for masonry infill-frames

Past studies have confirmed that the behaviour of an infill-frame can be remarkably different from that of a bare frame. This becomes specifically critical when the structure is under lateral loads such as wind and earthquake. This paper looks into the fundamentals of the most commonly used analytical method for the analysis of such structures, i.e. equivalent strut modelling. It is shown that even though several equivalent strut models have been proposed since the 1950s, none can be considered as a suitable generic tool to represent the behaviour of all infill-frame structures. It is further demonstrated that not only the total width of strut(s), but also the number and location of strut(s) may vary from one infill-frame to the next. It is also shown that even for the same infill-frame the strut properties change at different drift values. A methodology is proposed to develop an appropriate strut model incorporating the material nonlinearities for any given infill-frame. This methodology requires the analytical results of a primary FE model at a micro level to determine the geometric properties of struts.

Investigation on the effect of strut configurations and locations on the combustion performance of a typical scramjet combustor

The Reynolds averaged Navier-Stokes (RANS) equations coupled with the renormalization group (RNG) k-e and the single-step chemical reaction mechanism have been used to evaluate the influence of the radius of the strut tip, the half-angle of the strut and the strut location relative to the combustor entrance on the combustion performance of the combustor has been discussed. At the same time, the numerical method has been validated by the available experimental shadowgraph, velocity measurements and temperature measurements in the open literature. With the increasing of the radius of the strut tip, the separation region generated due to the strong interaction between the shock wave and the boundary layer becomes broader, and accordingly, a bifurcated shock wave appears at the front of the strut, then a shock wave train. The shock waves generated at the intersectional points between the walls of the strut and the sonic lines play an important role in the generation of the separation zone, and they can improve the combustion efficiency to a certain extent. Further, the mixing process is more intensive than the chemical reaction process in the vicinity of the strut base, and the combustion efficiency increases nearly monotonically with the increasing of the horizontal distance in the range considered in the current study. When the intersectional point between the leading shock wave and the upper wall overlaps with the divergence point, the combustion efficiency at the exit of the combustor becomes the largest, and its value is nearly 96.2%.

Investigation on Darrieus type straight blade vertical axis wind turbine with flexible blade

In this study, a three-dimensional VAWT with a spanwise passively deformable flexible blade has been modelled. The study mainly focuses on the analysis of blade structure characteristics associated with the bending and twist deflection. Two types of flexible blade material and two strut locations supporting H-type blades are being investigated. The unsteady external loads and energy efficiency of VAWT with such designed flexible blade are also being analysed. The simulation results show that the bending and twist deflection peak is positively correlated with the turbine tip speed ratio λ. For a flexible blade, an unevenly distributed structural stress along the blade with a high stress regime in the vicinity of strut location has also been observed. Due to the rotational motion of a VAWT, the centrifugal force acting on VAWT blade plays an important role on the blade structure characteristics. Reduction of the blade stiffness results in an increase of the blade stress. Changing the strut location from middle to tip will cause a large area under high stress. The results also indicate that the VAWT with a highly flexible blade is not an efficient energy extraction device when it is compared to a less flexible or a rigid blade.

Validation of Three-Dimensional Simulation of Flow through Hypersonic Air-breathing Engine

<p>The flow path of a conceptual hypersonic air-breathing scramjet engine integrated with the vehicle (without combustion) has been simulated numerically using ANSYS CFX software with the SST turbulence model. The computations were performed for the free stream Mach number of 6 and angle-of-attack of 5°. A strong separation bubble was observed on the bodyside wall in the internal compression region where the reflected cowl shock impinges on body which in turn increases the static pressure substantially. The external-internal flow field of the hypersonic mixed compression intake, shock-boundary layer interactions, and the shock-shock interactions present in the internal compression region have qualitatively been obtained and analysed. The variation of centreline pressure along the bodyside wall close to the symmetry plane obtained from numerical simulation centreline has been compared with the experimentally measured data. It has been observed that the computed wall pressure matches fairly well with the measured values in the external ramp compression region, internal compression region and in the combustion chamber. The flow patterns and the pressure variations near the middle wall and the fuel injecting strut locations have also been analysed.</p><p><strong>Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 272-278, DOI: http://dx.doi.org/10.14429/dsj.65.6979</strong></p>

Three-dimensional numerical simulations of straight-bladed vertical axis tidal turbines investigating power output, torque ripple and mounting forces

Three straight-bladed vertical axis turbine designs were simulated using Three-Dimensional (3D) transient Computational Fluid Dynamics (CFD) models, using a commercial Unsteady Reynolds Averaged Navier–Stokes (URANS) solver. The turbine designs differed in support strut section, blade-strut joint design and strut location to evaluate their effect on power output, torque fluctuation levels and mounting forces. Simulations of power output were performed and validated against Experimental Fluid Dynamics (EFD), with results capturing the impacts of geometrical changes on turbine power output. Strut section and blade-strut joint design were determined to significantly influence total power output between the three turbine designs, with strut location having a smaller but still significant effect. Maximum torque fluctuations were found to occur around the rotation speed corresponding to maximum power output and fluctuation levels increased with overall turbine efficiency. Turbine mounting forces were also simulated and successfully validated against EFD results. Mounting forces aligned with the inflow increased with rotational rates, but plateaued due to reductions in shaft drag caused by rotation and blockage effects. Mounting forces perpendicular to the inflow were found to be 75% less than forces aligned with the inflow. High loading force fluctuations were found, with maximum values 40% greater than average forces.

Optic Strut and Para-clinoid Region - Assessment by Multi-detector Computed Tomography with Multiplanar and 3 Dimensional Reconstructions.

To evaluate thickness, location and orientation of optic strut and anterior clinoid process and variations in paraclinoid region, solely based on multidetector computed tomography (MDCT) images with multiplanar (MPR) and 3 dimensional (3D) reconstructions, among Indian population. Ninety five CT scans of head and paranasal sinuses patients were retrospectively evaluated with MPR and 3D reconstructions to assess optic strut thickness, angle and location, variations like pneumatisation, carotico-clinoid foramen and inter-clinoid osseous ridge. Mean optic strut thickness was 3.64mm (±0.64), optic strut angle was 42.67 (±6.16) degrees. Mean width and length of anterior clinoid process were 10.65mm (±0.79) and 11.20mm (±0.95) respectively. Optic strut attachment to sphenoid body was predominantly sulcal as in 52 cases (54.74%) and was most frequently attached to anterior 2/5(th) of anterior clinoid process, seen in 93 sides (48.95%). Pneumatisation of optic strut occurred in 23 sides. Carotico-clinoid foramen was observed in 42 cases (22.11%), complete foramen in 10 cases (5.26%), incomplete foramen in 24 cases (12.63%) and contact type in 8 cases (4.21%). Inter-clinoid osseous bridge was seen unilaterally in 4 cases. The study assesses morphometric features and anatomical variations of paraclinoid region using MDCT 3D and multiplanar reconstructions in Indian population.

Experimental Research on Downstream Strut and Pressure Tapping Location of Cone DP Flow Meters

Experimental Research on Downstream Strut and Pressure Tapping Location of Cone DP Flow Meters

Anatomic Variation of the Optic Strut: Classification Schema, Radiologic Evaluation, and Surgical Relevance

Objective Anatomic variability of the optic strut in location, orientation, and dimensions is relevant in approaching ophthalmic artery aneurysms and tumors of the anterior cavernous sinus, medial sphenoid wing, and optic canal. Methods In 84 dry human skulls, imaging studies were performed (64-slice computed tomography [CT] scanner, axial view, aligned with the zygomatic arch). Optic strut location related to the prechiasmatic sulcus was classified as presulcal, sulcal, postsulcal, and asymmetric. Morphometric analysis was performed. Results The optic strut was presulcal in 11.9% specimens (posteromedial margin bilaterally anterior to limbus sphenoidale), sulcal in 44% (posteromedial part adjacent to the sulcus's anterior two thirds bilaterally), postsulcal in 29.8% (posteromedial margin posterior to the sulcus's anterior two thirds), and asymmetric (left/right) in 14.3%. Optic strut length, width, and thickness measured 6.54 ± 1.69 mm, 4.23 ± 0.69 mm, and 3.01 ± 0.79 mm, respectively. Optic canal diameter was 5.14 ± 0.47 mm anteriorly and 4.79 ± 0.64 mm posteriorly. Angulation was flat (>45 degrees) in 13% or acute (<45 degrees) in 87% specimens. Conclusions Anatomical variations in the optic strut are significant in planning for anterior clinoidectomy and optic-canal decompression. Our optic strut classification considers these variations relative to the prechiasmatic sulcus on preoperative imaging.

Optimization of a flight-worthy scramjet combustor through CFD

Reacting flow simulations are carried out for different fuel injection schemes and strut arrangements to obtain an optimized performance of a flight sized hydrocarbon fueled scramjet combustor using commercial CFD software. Three-dimensional Reynolds Averaged Navier–Stokes (RANS) equations are solved along with k–ε turbulence model to analyse the flow field. Eddy Dissipation Model (EDM) with fast rate chemical kinetics and Lagrangian Particle Tracking Method (LPTM) are used for modeling combustion and to simulate the trajectory of the kerosene droplets. It was found that at the exit plane, considerable amount of unburnt kerosene vapour in the core regions and unused oxygen in the side wall regions are present in the baseline combustor. Modified fuel injection scheme and modified strut locations are found to improve the thrust and combustion efficiency by 18.3% and 18.6% respectively compared to the baseline configuration.

SU‐FF‐T‐72: Dosimetric Comparison of SAVI, MammoSite, Contura and Clearpath for Accelerated Partial Breast Irradiation

Purpose: The number of intracavitary hdr brachytherapy devices available to treat women with early stage breast cancer has increased significantly in the past several years. Blending the dosimetry of interstitial and the ease of use of MammoSite; SAVI, Contura, and Clearpath have made their way into the arena. One would postulate that the evolution of the devices in the sense of dose modulation, from least to greatest, would be MammoSite, Contura, Clearpath, and finally SAVI. This stems from the location of peripheral struts in relation to the cavity boundary. In this study, we compare the dosimetry between the 4 devices and assess their efficacy through dose volume histograms (DVH) and maximum point doses of critical structures. Comparing these modalities will help determine either the best overall treatment device or the best device for a particular type of patient. Materials and Methods: Nine patients treated with SAVI at UC San Diego were selected for this comparison. CT scans were retrospectively evaluated for delivery of APBI via MammoSite, Contura and Clearpath by simulating them in place of the SAVI in the lumpectomy cavity. The anterior tissue surrounding the balloon devices was linearly expanded to simulate tissue displacement by the balloon. All plans were generated using Brachyvision TPS (Varian Medical Systems, Palo Alto, CA). Results: DVHs of the target volume were evaluated against planning criteria taken from the NSABP B‐39 protocol. All devices met the criteria and had similar target coverage (V90 ∼ 98%). However, there were differences in the dose received by normal tissue with skin dose lowest in SAVI patients (∼71% of prescribed dose). This was followed by Contura, MammoSite and Clearpath, respectively. Conclusions: All devices had similar coverage of the target volume, but SAVI had the most dose flexibility for patients with close skin spacing and chestwall proximity.