Non-standard Configurations Research Articles

2D numerical modeling of crack propagation using SFEMD method of a LEHI material

Numerical methods today play a useful and important role in solving various problems related to fracture mechanics including modeling crack propagation, fretting fatigue and cohesion... Furthermore, these methods have been widely used to solve problems in linear and nonlinear fracture mechanics in cases of elastic, plastic fracture problems. The evaluation of stress intensity factor in 2D and 3D geometries, thus these techniques widely used for non-standard crack configurations. The objective of this work is study the effects of the crack length and the number of structural elements on the two crack parameters such as the stress intensity factor KI and KII and the contour integral (J). As well as presenting a numerical modeling of crack propagation, for a LEHIM (Linear Elastic Homogeneous Isotopic Material) with mechanical characteristics by the method SFEMD (Stretching Finite Element Method Developed), the model chosen with quadratic elements with 4 nodes (CPE4). However, this method is based on the effect of the number of contours and the number of elements around the crack tip on the variation of the stress intensity factors. In addition, the crack propagation criterion (MCSC) was used, a computer program was created in FORTRAN language to develop and evaluate the stress intensity factors and the contour integral (J). Several examples of crack lengths a = 0.7, 1.4, 2.1, 2.8 and 3.5 mm were used. Additionally, the number of items has been changed several times. The stress intensity factors of modes I and II and direction angles (α) are calculated to solve the problem using the ABAQUS finite element code. The results obtained by the SFEMD method and the results of the analytical method are very close.

Recent results on high-β plasma confinement studies in the Gas Dynamic Trap

This paper is devoted to experimental studies of plasma confinement with high relative pressure ( $\beta$ ) in the Gas Dynamic Trap (BINP, Novosibirsk). In previous high- $\beta$ confinement studies a maximum local $\beta = 0.6$ was achieved in the fast-ion turning point, contributed to by a beam-driven population of fast ions with an anisotropic distribution function. In this study the axial magnetic field profile was modified to bring the turning points closer to one another, which effectively increased the energy density of plasma and pushed the $\beta$ value higher. Experiments were performed for two non-standard magnetic configurations, where the axial fast-ion confinement region length was reduced by 1.5 and 2 times compared with the standard configuration. The average values of $\langle \beta _{\perp } \rangle$ over the plasma central cross-section were found to be 0.1 and 0.18, respectively, for the two configurations, with the latter value significantly exceeding the $\langle \beta _{\perp } \rangle =0.08$ of the standard configuration, in which the previous record was set. Moreover, halving the fast ion confinement region almost doubled the D–D fusion proton flux from the trap centre compared with the standard configuration. The electron temperature in both new magnetic configurations was only slightly smaller than in the standard configuration. In addition, an effect of Alfvén ion–cyclotron instability (AICI) development on the pressure in the turning points is discussed. Presumably, with some decrease in magnetic field an evolving AICI does not result in considerable pressure axial redistribution, so the pressure maximum is in the turning points’ vicinity despite the instability.

3D Printing of Flow Profiles for Inspection Chambers and Manholes

For years the way of producing a flow profile for Inspection Chambers and Manholes could be divided into 3 methods: Injection moulding, Roto moulding and Hand assembling. For the standard orientations, for example straight through and cross, the IM profile integrated with a base is by far the best option. But for nonstandard configurations; different orientations, inlet heights and inlet sizes, the only option is to hand weld them together from injection moulded parts, pipes and plates. This is a time- consuming way of producing with high production cost and often aesthetic-wise of a challenging level. This is not necessary anymore after the introduction of 3D printing as a new production method for flow profiles in chambers and manholes. 3D printing is in many industries an accepted production method which can produce parts of high quality and high accuracy. The printing systems have faced a huge development in the last 10 years and prints are often close to perfection. The only disadvantage of these printing systems is the maximum size of the print. But since the introduction of 3D robot printing, products with a diameter of 1 meter can be printed without any problem. 3D robot printers were up to recently, used for prototypes, one- off products and art objects. Now a production area is created on which multiple products can be produced in a row without human interference. The most common materials used for 3D printing are ABS and PLA. These materials have good adhesion, almost no shrinkage and a good appearance. Unfortunately, these materials are not common in our industry. We need PP, PE or PVC. While our manholes and inspection chambers are from PP, we also need PP flow profiles. The advantage of using a 3D robot printer is that it uses granulates instead of filaments or special powder. This makes the material cost part almost equal to injection moulding. Another advantage is also that recycled material can be used. Own scrap can be used but also waste from other markets. The main reason that flows profiles are ideal for 3D printing is that nonstandard flow profiles are very labour-intensive. So, 3D printing really helps out here. Besides that, there is a lot of freedom in design. This helps to design in such a way, that the final profile is hydraulically optimal. This prevents the overflowing of manholes during heavy rain showers. Of course, these products should fulfil all requirements of the EN13598-2. Even though major development steps have been made in 3D printing during the last 5 years, 3D robot printing is still in the exploring phase and we find many hurdles on our way. This paper will show how our industry can use 3D printing and what are the pros and cons.

Magnetostatic Simulation and Design of Novel Radiofrequency Coils Based on Transverse Field Current Elements for Magnetic Resonance Applications.

Radiofrequency (RF) coils are key components in Magnetic Resonance (MR) systems and can be categorized into volume and surface coils according to their shapes. Volume RF coils can generate a uniform field in a large central sample's region, while surface RF coils, usually smaller than volume coils, typically have a higher Signal-to-Noise Ratio (SNR) in a reduced Region Of Interest (ROI) close to the coil plane but a relatively poorer field homogeneity. Circular and square loops are the simplest and most used design for developing axial field surface RF coils. However, for specific MR applications, the use of dedicated transverse field RF coils can be necessary or advantageous. Building on a previously developed and validated RF coil simulator, based on the magnetostatic approach, here we explore the potential applications of novel multiple axial field and transverse field surface RF coils in non-standard configurations. We demonstrate via numerical simulations that simple volume RF coils, matching a Helmholtz-like design, can be built with two identical transverse field RF coils separated by a given distance. Following well-known principles, the SNR of such novel configurations can be improved by a factor of up to √2 by combining two 90° rotated coils, producing, inside a central ROI, a circularly polarized B1 field.

Aerodynamic Characteristics of Circular and Noncircular Cross-Sectional Missile Configurations

This paper summarizes an investigation of the aerodynamic performance of missile configurations with axisymmetric and nonaxisymmetric cross sections. Configurations have either a circular, oval, pentagonal, triangular, or square cross section and were tested at three different flight conditions: Ma=1.17 and Reynolds number per inch of 3.88×105, Ma=2.49 and Reynolds number per inch of 6.88×105, and Ma=4.33 and Reynolds number per inch of 8.74×105. The influence of Mach number, shape, and fin deflection was investigated. A prescribed body motion was used to expedite the prediction of the missile aerodynamic forces and moments at different angles of attack compared to many static computational fluid dynamics simulations. The results show that the oval missile model is the most aerodynamically efficient body at all the tested speeds. At higher speeds, all nonstandard configurations produce more normal force and better aerodynamic efficiency than the circular body. The triangular configuration is much less stable than the other models.

Advanced modelling and iterative approach for high-accuracy PCHE design in SCO2 Brayton cycle

This study addresses the crucial challenge in the design of Plate Heat Exchangers (PCHEs) for SCO2 Brayton cycles, caused by inadequate mathematical models and heat transfer correlations. The paper introduces novel PCHE models that surpass existing approaches in accuracy and versatility. Three approximations (Models 1, 2, and 3) are evaluated and improved upon. Two new models, Basic Heat Transfer Analysis (Model 4) and Modified Heat Transfer Analysis (Model 5), are proposed, validated, and compared in both 2D and 3D scenarios. The innovation lies in the introduction of an Iterative Method to determine wall temperatures and integrating high-precision heat transfer correlations. Results demonstrate Model 5′s superiority over all models, achieving exceptional accuracy for standard and non-standard PCHE configurations. For standard setups, Model 5 exhibits ± 0.50 % RE, RMSE = 0.21 (2D), Error = 0.89 % (3D), outperforming other models. For non-standard configurations, Model 5 maintains superior accuracy (2D: RE = -0.5 %∼2%, RMSE = 0.67, 3D: Error = 1.53 % and 1.98 %).The study validates Model 4 and 5′s heat transfer coefficients through the Jackson correlation against CFD results, surpassing previous models using the Gnielinski correlation. In summary, the study introduces Model 5 as a novel, accurate, and versatile solution for PCHE design. The proposed Iterative Method further enhances accuracy and applicability. The paper's originality lies in the development of Model 5, its verification, and its recommendation as a preferred PCHE design tool, addressing critical industry needs and research gaps.

Electrochemical Model for a Three-Electrode Lead Acid Cell: Boundary Conditions for Asymmetric Configurations

A one-dimensional (1D) electrochemical model is developed for a lead-acid demonstration cell comprising two positive electrodes engaging a single negative electrode. Classical 1D models, which analyze a single repeat unit in a full battery, are extended to this non-standard configuration by considering additional porous electrode and electrolyte reservoir domains. The non-standard model necessitates appropriate boundary conditions to couple electrochemical variables in different domains, since symmetry boundary conditions typically employed at the current collector grids are no longer applicable. The modified model, with new boundary conditions, is simulated using standard techniques. Salient modeling and simulation differences compared to a standard lead-acid model are discussed, as are trends in predicted variables. The non-standard model predicts reduced polarization and more uniform utilization of the non-limiting electrodes, in addition to non-zero reaction currents and active material utilization in the terminal electrode faces, which are typically ignored in “unit-cell” analyses. This model is expected to be of substantial utility in guiding evaluations of new lead-acid battery designs through improved prediction of performance of such test configurations. The boundary conditions introduced herein are also useful for 1D modeling of non-standard configurations characterized by multiple, electrochemically interacting porous domains, particularly where spatial current distributions are initially unknown.

Non-Standard Electrode Placement Strategies for ECG Signal Acquisition

Wearable technologies for monitoring cardiovascular parameters, including electrocardiography (ECG) and impedance cardiography (ICG), propose a challenging research subject. The expectancy for wearable devices to be unobtrusive and miniaturized sets a goal to develop smarter devices and better methods for signal acquisition, processing, and decision-making. In this work, non-standard electrode placement configurations (EPC) on the thoracic area and single arm were experimented for ECG signal acquisition. The locations were selected for joint acquisition of ECG and ICG, targeted to suitability for integrating into wearable devices. The methodology for comparing the detected signals of ECG was developed, presented, and applied to determine the R, S, and T waves and RR interval. An algorithm was proposed to distinguish the R waves in the case of large T waves. Results show the feasibility of using non-standard EPCs, manifesting in recognizable signal waveforms with reasonable quality for post-processing. A considerably lower median sensitivity of R wave was verified (27.3%) compared with T wave (49%) and S wave (44.9%) throughout the used data. The proposed algorithm for distinguishing R wave from large T wave shows satisfactory results. The most suitable non-standard locations for ECG monitoring in conjunction with ICG were determined and proposed.

Virthuman Application: Is an Autonomous Vehicle with Non-standard Seating Safe in a Side Crash?

Highly Automated Vehicles (HAVs) will be more comfortable for their occupants than common cars from different aspects. For instance, their occupants can access extra spaces to adjust their seats as there will be no steering wheel and gearbox transmission handle in the interior. Among a wide range of seating configuration possibilities, the majority of passengers prefer to be in the Face-to-Face or the Living room configurations that are known as non-standard seating configurations. The present survey investigated how safe are these non-standard seating configurations in a side crash in comparison with the standard one in which all seats are facing the front windshield. Four identical 50th percentile Virthuman models were integrated into a schematic of automated vehicle's interior. Standard three-point seatbelts fastened bodies to up-right seats made from Polyurethane foam. A 30 km/h crash acceleration pulse was applied to the model for simulating side crash with a virtual sledge test in the Virtual Performance Solution (VPS) environment, PAMCRASH module. Results revealed that the Living room configuration was safer for the Rear Left occupant in comparison with the Standard one. Also, the Front Left occupant did not experience safer occasions in non-standard configurations from a Head & Neck injury point of view.

Category A + C passage in the light of applicable regulations

Abstract: Modern crossing systems made in computer technology, thanks to their modular structure and configuration flexibility, fully meet the requirements set for them. Their implementation is possible on all categories of railroad crossings with safety devices in typical and non-standard configurations. Computer technology makes their operation easy and ensures the highest security standards Keywords: A category crossing; BUES 2000

Numerical investigation of turbulent features past different mechanical aortic valves

Flow through mechanical aortic valves (MAVs) has been constantly associated to higher haemolysis and platelet activation levels with respect to native valves, due to non-physiologic haemodynamic features. Both computational and experimental investigations have correlated the blood damage to augmented levels of turbulent stress downstream of MAVs. This study provides a computational estimation, drawn from high-resolution direct numerical simulations, of turbulent and fluctuating viscous stresses in three different MAV configurations, at subsequent stages of the cardiac cycle. The configurations comprise a St. Judes Medical Regent valve (SJMV), a Lapeyre-Triflo FURTIVA valve (LTFV) with three leaflets, and a SJMV with vortex generators (VGs). Non-standard configurations are expected to mitigate the mean stress level on blood constituents reducing the turbulent production. Computations are carried out by means of a finite-difference flow solver with a direct-forcing immersed boundary technique to handle fixed and moving bodies. The VGs are found to provide instabilities which corrupt the Kármán-like vortex shedding downstream of the leaflets, reducing the intensity of turbulent kinetic energy at the peak flow rate, thus lowering the local Reynolds shear stress. Conversely, the LTFV configuration provides comparable haemodynamic performance at peak flow rate but further reduced stress level in the deceleration phase. These interpretations are supported by probability density distributions from three-dimensional fields, and further corroborated by a pointwise mapping of the Taylor length scale and local energy spectra. The outcomes of this study might potentially be exploited to improve the design of new-generation MAVs, with the aim of decreasing the risk of thromboembolic complications.

Experimental and numerical characterization of pure copper heat sinks produced by laser powder bed fusion

One of the technological challenges aimed at improving the cyclotron-based radionuclides’(RNs) supply for Nuclear Medicine (NM), is the availability of proper heat sink systems able to remove the large amount of heat deposited during the irradiation stage onto isotope-enriched targets. In this regard, three different non-standard mockup configurations, made of pure copper by means of the Laser Powder Bed Fusion (LBPF) technique, have been tested with an in-house developed experimental apparatus. The experimental characterization has subsequently been compared with numerical results carried out by means of Computational Fluid Dynamics (CFD) simulations. Our numerical model, based on the Re-Normalization Group (RNG) k-epsilon formulation, has shown close agreement (within 1.06 % Mean Absolute Error) with the experimental results, despite the geometrical complexity of the heat sinks prototypes. The combined experimental and numerical approach, together with the flexibility of additive manufacturing production, was proved to be apt for further development of high-efficiency heat exchange applications in this field.

Design, Modelling and Control of an Eight-Rotors UAV with Asymmetric Configuration for Use in Remote Sensing Systems

The use of multirotor unmanned aerial vehicles (UAV), which can take-off and landing vertically, is gradually expanding. Although there are many types of these vehicles with standard configuration, non-standard configurations may be required for special purposes usage. So, an octocopter UAV with asymmetric configuration is proposed in this study. In particular, this asymmetrically configured octocopter is intended to be used for imaging or mapping purposes, and may be a solution to widen the viewing angle of the camera or any sensor placed on the vehicle, especially in the use of multiple cameras and sensors. The mathematical model of this proposed UAV system was obtained and the trajectory tracking was performed using PID control method. The control parameters of the controller were determined using Grey Wolf Optimizer (GWO). Considering the propellers determined in two different sizes due to its asymmetrical structure, it has been observed that the proposed UAV performs a satisfactory trajectory tracking.

A review of one-phase Hele-Shaw flows and a level-set method for nonstandard configurations

The classical model for studying one-phase Hele-Shaw flows is based on a highly nonlinear moving boundary problem with the fluid velocity related to pressure gradients via a Darcy-type law. In a standard configuration with the Hele-Shaw cell made up of two flat stationary plates, the pressure is harmonic. Therefore, conformal mapping techniques and boundary integral methods can be readily applied to study the key interfacial dynamics, including the Saffman–Taylor instability and viscous fingering patterns. As well as providing a brief review of these key issues, we present a flexible numerical scheme for studying both the standard and nonstandard Hele-Shaw flows. Our method consists of using a modified finite-difference stencil in conjunction with the level-set method to solve the governing equation for pressure on complicated domains and track the location of the moving boundary. Simulations show that our method is capable of reproducing the distinctive morphological features of the Saffman–Taylor instability on a uniform computational grid. By making straightforward adjustments, we show how our scheme can easily be adapted to solve for a wide variety of nonstandard configurations, including cases where the gap between the plates is linearly tapered, the plates are separated in time, and the entire Hele-Shaw cell is rotated at a given angular velocity. doi:10.1017/S144618112100033X

A REVIEW OF ONE-PHASE HELE-SHAW FLOWS AND A LEVEL-SET METHOD FOR NONSTANDARD CONFIGURATIONS

AbstractThe classical model for studying one-phase Hele-Shaw flows is based on a highly nonlinear moving boundary problem with the fluid velocity related to pressure gradients via a Darcy-type law. In a standard configuration with the Hele-Shaw cell made up of two flat stationary plates, the pressure is harmonic. Therefore, conformal mapping techniques and boundary integral methods can be readily applied to study the key interfacial dynamics, including the Saffman–Taylor instability and viscous fingering patterns. As well as providing a brief review of these key issues, we present a flexible numerical scheme for studying both the standard and nonstandard Hele-Shaw flows. Our method consists of using a modified finite-difference stencil in conjunction with the level-set method to solve the governing equation for pressure on complicated domains and track the location of the moving boundary. Simulations show that our method is capable of reproducing the distinctive morphological features of the Saffman–Taylor instability on a uniform computational grid. By making straightforward adjustments, we show how our scheme can easily be adapted to solve for a wide variety of nonstandard configurations, including cases where the gap between the plates is linearly tapered, the plates are separated in time, and the entire Hele-Shaw cell is rotated at a given angular velocity.

Usage of natural balance mode in automatic trajectory control of aircraft with non-standard configurations

Currently, especially with the development of unmanned aircraft, a lot of aerial vehicles are being developed, the layout of which differs from traditional ones. These include flying wing aircrafts, multi-rotor vehicles with symmetry breaking, carrying loads, especially on flexible hitch, ekranoplans and ekranolyot, winged missiles with an asymmetric arrangement of bearing and control surfaces, and others. When developing control systems, it is necessary to take into account that atypical schemes introduce effects into the flight dynamics of such aerial vehicles that complicate and even prevent the use of conventional simplifying schemes for them: dividing into control channels, dividing the control system into trajectory control and stabilizing angular motion, using linearized models.The paper proposes to ensure the coarseness of the system by refusing to solve intermediate problems and providing movement to the natural balancing modes. Moreover, in the structures under consideration, for feedbacks, precisely those measurements are used (overloads, angular velocities), which even with the simplest sensors give relatively small or relatively easily eliminated errors. Worse with measurement errors used for constraints (angles, heights). Here you will either have to narrow the boundaries or enter different settings of the control signals depending on the ratio of proximity to the borders and estimates of the measurement error, using, for example, fuzzy logic.

Numerical Study of Frontal Collision Effects on an Occupant’s Safety, in Autonomous Vehicles, with Non-Standard Seating Configurations

Numerical Study of Frontal Collision Effects on an Occupant’s Safety, in Autonomous Vehicles, with Non-Standard Seating Configurations

Non-convex primal-dual algorithm for image reconstruction in spectral CT

The work seeks to develop an algorithm for image reconstruction by directly inverting the non-linear data model in spectral CT. Using the non-linear data model, we formulate the image-reconstruction problem as a non-convex optimization program, and develop a non-convex primal-dual (NCPD) algorithm to solve the program. We devise multiple convergence conditions and perform verification studies numerically to demonstrate that the NCPD algorithm can solve the non-convex optimization program and under appropriate data condition, can invert the non-linear data model. Using the NCPD algorithm, we then reconstruct monochromatic images from simulated and real data of numerical and physical phantoms acquired with a standard, full-scan dual-energy configuration. The result of the reconstruction studies shows that the NCPD algorithm can correct accurately for the non-linear beam-hardening effect. Furthermore, we apply the NCPD algorithm to simulated and real data of the numerical and physical phantoms collected with non-standard, short-scan dual-energy configurations, and obtain monochromatic images comparable to those of the standard, full-scan study, thus revealing the potential of the NCPD algorithm for enabling non-standard scanning configurations in spectral CT, where the existing indirect methods are limited.

A Monte Carlo ray-tracing simulation of coherent X-ray diffractive imaging.

Coherent diffractive imaging (CDI) experiments are adequately simulated assuming the thin sample approximation and using a Fresnel or Fraunhofer wavefront propagator to obtain the diffraction pattern. Although this method is used in wave-based or hybrid X-ray simulators, here the applicability and effectiveness of an alternative approach that is based solely on ray tracing of Huygens wavelets are investigated. It is shown that diffraction fringes of a grating-like source are accurately predicted and that diffraction patterns of a ptychography dataset from an experiment with realistic parameters can be sampled well enough to be retrieved by a standard phase-retrieval algorithm. Potentials and limits of this approach are highlighted. It is suggested that it could be applied to study imperfect or non-standard CDI configurations lacking a satisfactory theoretical formulation. The considerable computational effort required by this method is justified by the great flexibility provided for easy simulation of a large-parameter space.

Non-contact characterization of compound optical elements using reflectance confocal microscopy, low-coherence interferometry, and computational ray-tracing

Advances in microscopy have enabled us to see at unprecedented depths and resolutions, even breaking the diffraction-limit by several fold. These improvements have come at the expense of system complexity with microscopes routinely employing multiple objective lenses and custom optical relays. Optimal system design is paramount for imaging performance, but research systems are limited by the use of commercial components because optical prescriptions are often inaccessible. System performance can be further degraded when these components are implemented in nonstandard configurations outside of manufacturer specifications. Here, we describe a method for characterization of compound optical elements including curvatures, material and air-gap thicknesses, and glass types. We present validation data for doublets and a commercial broadband scan lens. Our method is both non-contact and non-destructive, and we believe it addresses a unique gap in optical design that may be extended to broad applications in both research and industrial manufacturing.