Core Geometry Research Articles

Influence of Coolant Additives and Core Geometry of Fin-Tube Automobile Engine Radiators on the Enhancement of Cooling Process Efficiency

The paper deals with the research on the influence of the shapes of tubes and fins of automobile engine radiators and ethylene glycol coolants of type G12 on the cooling process. This involves cross-flow without mixing of coolant and air. The circular tubes with straight fins are compared with flat tubes with corrugated fins at identical external dimensions of the radiators. The new coolant is compared with the used coolant (10 years of usage) and further with a mixture of the used coolant and the additive (coolant enhancer). The goal is to reduce the heat dissipation time during the cooling process. Forced air convection is generated by three fan variants with diameters ϕ400 mm, ϕ345 mm, and a pair of fans ϕ345 mm and ϕ290 mm. The radiator core with flattened tubes and corrugated fins achieved lower outlet temperatures of 0.35 °C, 1.56 °C, and 2.43 °C compared to circular tubes and straight fins when using the ϕ400 mm diameter fan, the fan pair, and the ϕ345 mm diameter fan, respectively. The addition of the coolant enhancer to the used and new G12 coolant, depending on the fan variant, caused the outlet temperature to decrease in the range of 0.64 °C to 1.47 °C and 0.55 °C to 1.65 °C, respectively. The fan cover is also important for efficient cooling. Refilling of the coolant enhancer in the used coolant ensured that the heat transfer properties were recovered.

Utilization of the Thorium of the Holos-Quad Micro-Reactor Concept

In this study, the criticality and burnup analyses have been performed for Holos-Quad micro nuclear reactor as a thorium burner which has 15 ton reactor mass and 22 MWth full core geometry by using continuous-energy multi-purpose three-dimensional Serpent and OpenMC Monte Carlo particle transport code with ENDF/ B-VII data libraries. As nuclear fuel, reactor grade (RG) and weapon grade (WG) Pu mixed with ThO2 in different proportions have been used. Firstly, effective criticality for RG-Pu and WG-Pu for operation period have been determined. In addition, since each of the 4 subcritical power modules must be subcritical due to the structure of the Holos-Quad reactor, the criticality analysis of the power modules has been performed. The criticality, burnup and fissile fuel production of the Holos-Quad micro nuclear thorium-burner have been calculated with different fuel fraction depending on the fuel type. Finally, thorium mixed fuels with 35% WG-Pu or 75% RG-Pu would allow burn up levels of ~ 25 GWd/ton and ~15 GWd/ton with reactor operation periods ~3.5 years without fuel change, respectively.

Mechanical behavior analysis of sandwich composite structures with different core geometries under three-point bending

This study presents a comprehensive investigation into the mechanical behavior of sandwich composite structures featuring six distinct core geometries under three-point bending conditions. Through detailed finite element analysis (FEA), the research examines the performance characteristics of I-shaped, traditional honeycomb (NIDA), O-shaped, X-shaped, semi-circular, and modified core geometries. The analysis focused on stress distribution patterns, displacement responses, and overall structural integrity. Results demonstrate that the semi-circular core geometry exhibits superior mechanical properties, achieving an 84.66% improvement in positive stress resistance and 74.79% enhancement in negative stress resistance compared to the traditional honeycomb reference model. The study revealed consistent linear elastic behavior across all models within the tested displacement range, with the semi-circular configuration showing optimal stress distribution and minimal core deformation. Using aluminum for facings and core materials, the research evaluated mechanical responses through displacement-controlled loading conditions, measuring stress concentrations at critical points and analyzing deformation patterns. This research provides valuable insights into the relationship between core geometry and mechanical performance, offering practical implications for engineering applications requiring high strength-to-weight ratios and enhanced flexural resistance in modern structural design.

From Fiber Layout to the Sensor: Preparation Methods as Key Factors for High-Quality Coupled-Core-Fiber Sensors.

During recent years, the optical-fiber-based simultaneous sensing of strain and temperature has attracted increased interest for different applications, e.g., in medicine, architecture, and aerospace. Specialized fiber layouts further enlarge the field of applications at much lower costs and with easier handling. Today, the performance of many sensors fabricated from conventional fibers suffers from cross-sensitivity (temperature and strain) and relatively high interrogation costs. In contrast, customized fiber architectures would make it possible to circumvent such sensor drawbacks. Here, we report on the development of a high-quality coupled-core fiber and its performance for sensors-from the initial fiber layout via elaboration of the preform and fiber up to the sensor evaluation. A compact, high-speed, and cost-effective interrogation unit using such a specialized coupled-core fiber has been designed to monitor reflectivity changes while even being able to distinguish the direction of the force or impact. Several fiber core material techniques and approaches were investigated, which made it possible to obtain a sufficient volume of material for the required fiber core number and a specialized fiber core geometry in terms of core distances and radial refractive index profile, whilst handling the non-symmetrical fiber architectures of such modeled, complex structures and balancing resources and efforts.

Thermal Fluid Modeling Approaches in SAM for High Temperature Gas-Cooled Reactor Applications

This paper provides an overview of the unique modeling and simulation challenges and needs in the system and safety analysis of two common types of High Temperature Gas-cooled Reactor (HTGR) designs. The challenges are associated with the complex core geometry configurations and the change of the dominant heat removal mechanisms between normal operating conditions and decay heat removal transients. This requires that simulation tools utilize models with reasonable length scales and capture both the localized heat transfer and the core-scale heat transfer at the same time. To meet such analysis needs, different methodologies were developed. This includes adopting existing methods and further developing/improving them, as well as proposing innovative methods that leverage advanced computational frameworks such as the Multiphysics Object Oriented Simulation Environment (MOOSE).

Design correlations for a novel enhanced compact heat exchanger with offset circular fins

A novel core geometry for compact heat exchangers, termed “circular offset fins (cOF)”, is proposed and experimentally investigated in the present work. This core design resembles the well-known offset strip fins used in efficient compact heat exchangers, with a key difference that instead of having rectangular fluid flow passages between deflections, this design features circular paths, resulting in fins with semicircular profiles. An experimental study examined heat transfer and pressure drop characteristics for five different core geometries. These geometries varied in passage diameters, lengths, and degrees of obstruction. The experiments were carried out over Reynolds numbers ranging from 500 to 3000 at different core wall temperatures. Data was analyzed using Kays and London's steady-state steam-to-air heat transfer technique to determine the empirical Colburn factor. The empirical Fanning friction factors for these geometries were also obtained. The asymptotic behavior of the Colburn and Fanning friction factor data allowed for the development of correlations in the function of Reynolds number and geometry dimensionless parameters. The proposed correlations predict data within ±6 % and ±8 %, respectively. The impact of different geometric parameters on core performance was assessed using the Colburn and Fanning friction factors, as well as area and volume goodness factors, and compared to rectangular offset strip fins. Direct comparisons showed that circular offset fins consistently exhibited a lower friction factor than rectangular fins. Although its Colburn factor was lower than rectangular fins up to a Reynolds number of 2000, circular fins it surpassed that of rectangular fins beyond this point. For the area goodness factor, their performance was comparable at a Reynolds number of 500, with circular fins outperforming after this point, achieving a 1.8-fold advantage at a Reynolds number of 3000. In terms of the volume goodness factor, both types of fins performed similarly up to a Reynolds number of 1000. Beyond this threshold, circular offset fins demonstrated a 1.3-fold improvement at a Reynolds number of 3000, underscoring the potential of the novel core geometry for compact heat exchanger applications.

A subchannel analysis code for advanced liquid metal fast reactor cores and study on heat transfer characteristics of core geometry parameters

The liquid metal fast reactor represents an important reactor type for the future development of nuclear energy. Accurately modeling and predicting the subchannel flow and heat transfer phenomenon in the rod bundles plays a key role in ensuring core safety. Consequently, a subchannel code suitable for the liquid metal fast reactor is analyzed based on the subchannel analysis code of the Pressurized Water Reactor (PWR). The modified code incorporates various types of liquid metals, such as lead, lead-bismuth eutectic (LBE), and sodium, along with their constitutive models, enhancing the applicability of the liquid metal reactor systems. This code has been verified and validated at several levels, including comparing the code simulation results with other similar subchannel codes results, high-dimensional Computational Fluid Dynamics (CFD) simulations, and experiment data. The sensitivity analysis of core geometric parameters and turbulent mixing coefficients is performed based on the modified version code. The influence of the core geometry, including the rod Pitch to Diameter ratio (P/D), Rod to Wall gap (RTW) and the wire wrap pitch (H) on the sensitivity of outlet temperature has been investigated. The results show that the new subchannel analysis code suitable for liquid metal cooled reactor shows reasonable agreement with the verified and validated results. The geometric parameters, such as P/D, RTW and H have noticeable effects on the outlet temperature difference of the subchannels. Additionally, the outlet temperature distribution in the subchannel is significantly affected by different turbulent mixing coefficients and the distribution of the turbulent mixing coefficient also influenced by the reactor core sizes. Overall, this study could support the rod bundles design and safety analysis in the liquid metal reactors.

Analysis of Tetrachiral Sandwich Structures at High-Velocity Impact: Influence of the Applied Material and Projectile Core Geometry

This research involved ballistic impact analysis on a tetrachiral sandwich structure in which the shapes of the circular nodes in the tetrachiral core are modified into polygonal shapes, namely a square, hexagon, and octagon. The objectives of this study were to observe the effect of a modified sandwich tetrachiral structure core, investigate the effect of the projectile geometry, and calculate the material performance of the structure. This research was conducted using numerical analysis utilizing the finite element method. The simulation methodology was validated through a benchmarking study, the results of which showed an error below 6%. The findings show that the material with the best performance was Armox 500T, at 5033 J. The most difficult projectile to withstand was conical, followed by ogive, hemispherical, and blunt. The results of the core modification on the tetrachiral sandwich structure show that the octagonal core had better energy absorption, by 2.8%, compared to the circular core. Modifying the node geometry in the tetrachiral core and then analyzing it with stress and strain contours are the novel aspects of this research. Doi: 10.28991/CEJ-2024-010-10-017 Full Text: PDF

Experimental analysis of quasi‐static indentation in composite sandwich multilayers with corrugated core

AbstractThis study examines the effects of multilayering in sandwich panel composite structures with different corrugated core configurations under quasi‐static indentation loading. The panels were fabricated using woven glass fibers and epoxy resin via the Vacuum Infusion Process. Experiments were conducted using two hemispherical cylindrical indenters with a diameter of 20 mm (ID = 20 mm) and 10 mm (ID = 10 mm) and the behavior of the composite structure in terms of contact force and fracture mechanisms for different core corrugations (square and butterfly) were investigated in two ways with foam and without foam. The experimental results demonstrate that, among corrugated core geometries without foam, butterfly cores outperform square cores in terms of structural strength, maximum force, moment force, energy absorption, specific energy absorption, and displacement until full indentation. Moreover, the butterfly core shows a higher peak load and different failure mechanisms compared to the square core. Under loading with a 10 mm indenter, the butterfly core without foam only experienced perforation in the loading area, without fracture completely. Also, adding foam did not change failure mechanisms and mechanical behavior in the butterfly geometry. However, in the square geometry, foam filled gaps between the core, preventing fracture completely and leading to only perforation in the loading area, unlike the specimen without foam. The visual analysis during the quasi‐static indentation process revealed several significant damage mechanisms, including matrix cracking, fiber breakage, delamination, buckling and crushing of cell walls, damage to top sheets, core separation, and complete indentation of the samples.Highlights Delamination and indentation failure mechanisms were seen on the butterfly core. Skin indentation and rib fracture failure mechanisms were seen on the square core. Butterfly corrugated cores revealed the best performance without/with foam. The core shape was more effective on the strength than the foam addition.

Development of a liquid metal subchannel code applied to ocean conditions and study on the effect of core geometry parameters and ocean motions on flow and heat transfer characteristics

The Generation IV International Forum (GIF) proposes a type of liquid metal reactor, due to its thermal properties and efficient heat transfer in a relatively small system. This special heat transfer characteristic allows the liquid metal reactor to be modular in design and flexible in installation on a nuclear-powered ship. Accurate prediction of the coolant temperature and flow distribution between subchannels is important to ensure nuclear safety in the complex ocean environment. In this study, an ocean version of subchannel code is developed by adding the motion terms in the momentum equations for the liquid metal reactor core based on the previously land-based subchannel code. Since the research on the characteristics of flow resistance and heat transfer mechanism under ocean conditions is not mature, the original empirical model is still used in the ocean version code. The constitutive models of the liquid metal are analyzed and incorporated into the ocean code. The code has been verified and validated by comparing with Computational Fluid Dynamics (CFD) simulation results, and experimental data. The effect of geometric parameters such as rod Pitch to Diameter ratio (P/D), Rod to Wall gap (RTW) is studied in the liquid metal lead 7 rod bundles. In addition, the effect of heaving start-up and shutdown motions between liquid metal lead and water is discussed in the 5 × 5 bare rod bundles. In general, the modified subchannel analysis code can well complete the calculation of liquid metal reactor under ocean conditions, as well as provide support for the design and safety analysis of a liquid metal cooled fast reactor.

Development of Multigroup Monte Carlo Neutron Transport Method with Regionwise Even-Parity Discontinuity Factor

The multigroup Monte Carlo (MC) neutron transport method with a regionwise even-parity discontinuity factor (REPDF), i.e. the discontinuity factor (DF)–MC method, is developed with the aim to provide a reference solution for deterministic transport calculations with DF. Applying the analogy with optics, neutrons are transmitted or reflected at a region surface during random walks. The probability of transmission or reflection is determined by REPDFs in adjacent regions. The DF is traditionally used in deterministic neutron transport methods to reduce the discretization error due to spatial homogenization and energy condensation. The DF-MC method can treat DF in the framework of the multigroup MC method. In this paper, the weight cancellation technique based on the closest pair of points using the divide-and-conquer algorithm is used because negative weights appear due to the neutron reflection. The REPDF is calculated by the method of characteristics (MOC). The verification calculations are carried out in the pin-by-pin homogenized and assembly homogenized KAIST-2A core geometry. The DF-MC calculation can reproduce the results of the MOC with the REPDF. These results demonstrate the principle of the DF-MC method and extend the application of the DF to the probabilistic neutron transport method.

Low-velocity impact response of hybrid core sandwich panels with spring and strut cores filled with resin, silicone, and foam

Advancements in the load-bearing capacity of composite panels open doors to high-performance applications. The integration of additive manufacturing allows for the creation of intricate core designs effortlessly. Hybrid cores, combining structural elements with infill materials, play a crucial role in enhancing panel impact resistance while maintaining its low weight. This study compares sandwich panels incorporating spring and octet strut structural elements infused with different materials—silicon, foam, and epoxy resin—evaluating their energy absorption capabilities. Additive manufacturing is employed to produce these panels with structural elements then subsequently filled with infills. The drop tower test is utilized to experimentally assess panel behavior under low-velocity impact. Design of experiments and statistical analysis are used to examine the influence of core height, impact height, core geometry, and filling type on the damaged area and impactor penetration. Results showed that the strut-based structure performed better than other structures in preventing penetration, with a damaged area reduction from 501.45 to 301.58 m2 compared to the spring core. The addition of foam or silicon reduced the impact damage to the front and the back sheets, with silicon infills proving to be the most effective, reducing penetration by reducing penetration by about 60%. The depth of impact was measured, with results indicating that the truss core displayed the smallest specific depth of penetration. A decision tree model predicted that a sandwich panel with a spring core would have a 100% chance of perforation while a filled core showed a significantly reduced penetration risk.

Fault characteristics in exhumed basement rocks; implications for understanding subsurface basement faults

We studied fault core geometry and mechanical properties of exhumed basement rocks at two localities (Storskora and Lislaskora) in Sotra Island, western Norway. We combine outcrop studies with in-situ measurements of the rock stiffness (Young's modulus) to characterize the faults. Faults were investigated both along and across strike using multiple 1D scanlines on the outcrop. Our results show that both fault core thickness and stiffness values vary along the faults. Thicker fault cores (up to 0.8 m and 1.9 m in Storskora and Lislaskora loaclities, respectively) show higher values of stiffness (Young's modulus) up to 70 GPa. The stiffness values of the fault core are generally higher than those measured on the damage zone of the faults in this area. The presence of epidote and compacted fault gouge in the fault core can cause the increase in estimated fault core stiffness. In contrast, fractures are dominant in the damage zones causing local reductions in the stiffness. A map of recent seismic events in this area shows potential seismic activities along some of the major exposed faults in the Sotra Island (e.g. Rustefjorden Fault). Based on the evidence from outcrop, inferred displacements, and interpretation of an available reflection seismic section, we found that the exposed faults could be secondary and part of the damage zone of the Øygarden Fault Complex in the east margin of the rift system in the North Sea. The results of this study could be utilized to predict the architecture and changes in rock stiffness of basement-involved faults in the subsurface.

Experimental and numerical investigation of damage in multilayer sandwich panels with square and trapezoidal corrugated cores under quasi-static three-point bending

Multilayer composite sandwich panels with corrugated cores have the potential for structural applications requiring high stiffness and strength-to-weight ratios. This study aims to experimentally and numerically investigate the bending response of sandwich panels with novel square and trapezoidal corrugated core configurations fabricated from E-glass fiber-reinforced epoxy composites, both with and without polyurethane foam filling. Quasi-static three-point bending tests were conducted to evaluate and compare the flexural stiffness and maximum load capacity of the panel designs. The cores were manufactured using vacuum-assisted resin transfer molding. Key results showed that changing the core geometry from square to trapezoidal improved the bending stiffness by up to 26 %. Incorporating polyurethane foam further increased the bending stiffness by up to 41 % and maximum load by up to 47 % compared to solid cores. Failure initiation and progression were governed by matrix cracking in the face sheets and cores, followed by core cell wall buckling and delamination. Finite element modeling using ABAQUS captured the progressive damage behavior, exhibiting good agreement with experimental force-displacement responses. Failure modes included matrix cracks, fiber fractures, core buckling and delamination. This study provides valuable insights into the mechanical performance of innovative corrugated core sandwich panel designs under quasi-static bending loads. The validated FE approach also enables virtual testing and optimization of composite sandwich structures.

Chirally-coupled-ring fibers for arbitrary-order orbital angular momentum mode generation and detection.

A novel chirally-coupled-ring fiber (CCRF) is proposed for efficiently generating and detecting arbitrary-order orbital angular momentum (OAM) modes in ring-core fibers (RCFs). The CCRF comprises inner and outer cores, N angularly uniformly distributed dielectric rods, and a cladding layer. These rods, twisted along the fiber axis between the cores, introduce angular geometry perturbations to manipulate the core modes. Through meticulous theoretical modeling and systematic analysis grounded in coupled-mode theory, we reveal CCRF eigenmodes carrying spin-entangled OAM, elucidate the mode coupling and power transfer in CCRFs, and present the CCRF design principle. Utilizing the full-vector beam propagation method, we carry out a proof-of-principle experimental system to demonstrate the capability of CCRFs in OAM mode manipulation and their feasibility and superiority in system-level applications. Additionally, we generate OAM modes across a wide range of topological charges from ℓ = -8 to ℓ = 8 using CCRFs, with conversion efficiencies from 92.10% to 99.63% and mode purities from 90.28% to 99.48%. Attributed to a coaxial dual-core structure with core-separated geometry perturbations, CCRFs enable flexible manipulation of arbitrary-order OAM modes without altering core geometry parameters, effectively solving design flexibility and compatibility problems in conventional single-core fiber devices. The proposed CCRF holds great promise for fiber-based OAM applications, especially for RCF-based OAM multiplexing communications.

Probing the geometric and electronic structure of rhodium oxide clusters (RhO)n− (n = 2–4) by anion photoelectron spectroscopy and theoretical calculations

The cluster configurations of (RhO)n− (n = 2–4) have been examined using photoelectron (PE) velocity-map imaging combined with density functional theory calculations. The PE spectra have provided the anion detachment energies (ADEs) information of three ground states, determined to be 2.40, 2.86, and 2.94 eV for n = 2–4, respectively. The geometric structures have been identified by comparing the density of states (DOS) spectra of several low-lying isomers with the PE spectra. The three cluster configurations consist of a Rhn (n = 2–4) core with isolated O atoms bonded to the core, exhibiting planar or quasi-planar geometries. The analysis of magnetic moments and spin densities indicated that the most stable three anions have high spin multiplicities of 4, 5, and 4 for n = 2–4, respectively, with the unpaired electrons delocalized on each of the Rh and O atoms.

Modal response of sandwich plate having carbon-epoxy faceplate with different honeycomb core material and geometry considerations

Modal response of sandwich plate having carbon-epoxy faceplate with different honeycomb core material and geometry considerations

Flux distribution tallies using proper orthogonal decomposition in Monte Carlo calculations

ABSTRACT In this paper, a new tallying method for a neutron flux distribution using the proper orthogonal decomposition is proposed for dimensionality reduction. The target spatial flux distribution is expanded by orthogonal basis vectors. Expansion coefficients are tallied during the random walk of the Monte Carlo calculation. The orthogonal basis vectors are extracted from the pre-calculated snapshots by the singular value decomposition. The proposed method is verified in the multi-group Monte Carlo calculation with the one-dimensional heterogeneous whole core geometry as a feasibility study. The flux distribution for each of the assemblies and energy groups is expanded by the basis vectors. The fewer basis vectors obtained from snapshots can reconstruct the target distribution well compared with the conventional Legendre polynomials used in the functional expansion tallies. The dimension of the solution in the proposed method is reduced by a factor of twenty compared with the conventional cell tally. In addition, the statistical error is reduced through dimensionality reduction thanks to the methodological feature of the proposed method. The results indicate that the proposed method has the capability of dimensionality reduction to tally the finely discretized flux distribution.

Divisive language.

What language devises, it might divide. By exploring the relations among the core geometries of the physical world, the abstract geometry of Euclid, and language, I give new insight into both the persistence of core knowledge into adulthood and our access to it through language. My extension of Spelke's language argument has implications for pedagogy, philosophy, and artificial intelligence.

Epifluorescence microscopy study of a quadruple node of triple junctions of grain boundaries in a Eu2+-decorated highly textured composite of (Cl, Br)(K, Rb) and I(K, Rb) solid solutions.

The structural nature and geometry, as well as the lattice-relative orientation, of an arrangement of crystal defects in a highly textured Eu2+-doped composite of two alkali-halide solid solutions was studied by epifluorescence microscopy (EFM) using the doping ion as a fluorochrome. A three-dimensional reconstruction and a skeleton type model, as built from a sequence of EFM images of different optical cross-sections of this arrangement, are presented. Structurally, this arrangement is a quadruple node (QN) of triple junctions of grain boundaries. The QN core geometry is that of a tetragonal tristetrahedron (TTTH), centred at the QN site, whose tetrahedron vertices and edges are on the QN triple junctions and grain boundaries, respectively, whereas the tristetrahedron tetragonal axis is nearly parallel to the lattice [001]-axis. The measured values of the angles between triple junctions and between the grain boundaries forming them are reported. The distinct chemical compositions of the composite solid solutions are discussed to be responsible, in last instance, for the tristetrahedron departure from a cubic configuration. Collaterally, certain families of translationally periodic almost-parallel (TPAP)-wall-like regions which consist of TPAP-columns of TPAP-spindle-like singularities, as well as certain zigzag arrays of columns of this like, existing into the QN grains, are reported to be observed. Three-dimensional reconstructions of typical individuals of these families and arrays as well as of their constituent parts are presented and geometrically analysed. These families and arrays are discussed to be families of tilt subboundaries, whose constituent dislocations are decorated by cylindrical second-phase europium di-halide precipitates, and regularly faceted tilt subboundaries, respectively. Crystal growing and sample preparation, composite structural characterisation by powder and single-slab X-ray diffraction (PXRD and SSXRD, respectively), microscopy and fluorescence-cube unit optics, image processing, electronic three-dimensional reconstruction and measuring methodologies, are all described in detail.