Reference Geometry Research Articles

Dimensional reliability in CAD/CAM production of complete denture bases: A comparative study of milling and various 3D printing technologies.

This study aims to assess the dimensional accuracy of complete denture bases fabricated from different CAD/CAM technologies and a conventional method, including milling (CNC), PolyJet (PJ), laser sintering (SLS), digital light processing (DLP), and injection molding (IM). It also examines the influence of the removal of technology-specific connectors or support structures when present. Denture base surfaces were digitized using a laboratory scanner, and virtual measurement points were calculated with tetrahedral reference geometries. Defined distances were measured in all spatial directions and compared to design data (p<0.05), revealing significant differences in sagittal (p=0.004), transversal (p<0.001), and vertical (p<0.001) dimensions. Connector removal had no significant impact for CNC but significantly affected DLP. All technologies yielded clinically acceptable results, with CNC milling demonstrating the best overall outcome.

Finite element and experimental modeling of jaw movement-induced deformations in the human earcanal

As ear-related technologies proliferate, optimizing comfort, retention, and battery life is crucial for enhancing user experience. A thorough understanding of the anatomical interaction between the temporomandibular joint (TMJ) and the earcanal during mouth-opening is essential. This study develops a finite element model and an experimental setup to investigate the biomechanical coupling between the TMJ and the earcanal. We analyze reverse-static deformations, focusing on cartilage-bone junction geometry, mandibular condyle location, and concha mobility. The earcanal geometry is assessed across five cross-sections with seven key dimensions measured. The results indicate that the deformations in cantilever-beam-like models closely match the reference geometry in both approaches, particularly in the lateral region. These findings suggest that a dynamic motion model of the earcanal, accurately simulating its behavior, is feasible.

Computational fluid dynamics; a new diagnostic tool in giant intracerebral aneurysm treatment

Giant intracerebral aneurysms (GIA) comprise up to 5 % of all intracranial aneurysms. The indirect surgical strategy, which leaves the GIA untouched but reverses the blood flow by performing a bypass in combination with proximal parent artery occlusion is a useful method to achieve spontaneous aneurysm occlusion. The goal of this study was to assess the utility of computational fluid dynamics (CFD) in preoperative GIA treatment planning. We hypothesise that CFD simulations will predict treatment results.A fluid-structure interaction (FSI) CFD investigation was performed for the entire arterial brain circulation. The analyses were performed in three patient-specific CT angiogram models. The first served as the reference geometry with a C6 internal carotid artery (ICA) GIA, the second a proximal parent artery occlusion (PAO) and virtual bypass to the frontal M2 branch of the middle cerebral artery (MCA), and the third a proximal PAO in combination with a temporal M2 branch bypass. The volume of “old blood”, flow residence time (FRT), dynamic viscosity and haemodynamic changes were also analysed.The “old blood” within the aneurysm in the bypass models reached 41 % after 20 cardiac cycles while in the reference model it was fully washed out. In Bypass 2 “old blood” was also observed in the main trunk of the MCA after 20 cardiac cycles. Extrapolation of the results yielded a duration of 4 years required to replace the “old blood” inside the aneurysm after bypass revascularization. In both bypass models a 7-fold increase in mean blood viscosity in the aneurysm region was noted.Bypass revascularization combined with proximal PAO favours thrombosis. Areas prone to thrombus formation, and subsequently the treatment outcomes, were accurately identified in the preoperative model. Virtual surgical operations can give a remarkable insight into haemodynamics that could support operative decision-making.

A case study of preliminary damage detection of two heritage vaults through geometric deformation analysis on 3D point clouds

Masonry vaults are common structural elements in heritage buildings that, given their long lifespan, are susceptible to the accumulation of damages and deformations from diverse actions such as overloads, support movements, seismic action, etc. The use of 3D point clouds from terrestrial laser scanners and structure from motion photogrammetry survey to investigate these deformations can offer valuable information for structural assessment and conservation, particularly when historical information is limited. The analysis of the deviation measured between the surveyed as-built point cloud of a vault and a reference geometry could reveal deformation patterns. Those, compared with recurring damage mechanisms discussed in literature, can provide a preliminary identification of the damage mechanisms affecting a structure, and the evaluation guide the recognition of the underlying action. The aim of this paper is to investigate how to generate different reference geometries and the impacts of their choice as reference geometry for the identification and quantification of different deformations. Deviation analyses were performed on the main vaults of two different churches with different reference geometries (i.e., geometries derived from the survey and geometrical primitives fitted on point-cloud), and the results were discussed by comparing the deviation maps obtained with the crack pattern and the already known deformations of the buildings.

Effect of geometric parameters on the heat transfer performance of a submerged coil condenser for heat-pump water heating

Water heating with heat pumps can contribute to reduce carbon dioxide emissions and meet sustainability goals due to its high thermal efficiency, versatility in terms of alternative energy sources and thermal energy storage capability. In this study, the heat transfer of the condenser subsystem of an accumulation heat-pump water heater is analyzed by means of 2D CFD simulations. After validating the simulation methodology with benchmark natural convection problems, the influence of different geometric parameters of the condenser coil on the heat transfer is studied, which include the distance between turns and the distance from the tank wall. For each case, Nusselt number correlations in terms of Rayleigh number are found via power-law fitting. According to the CFD results, a greater coil pitch improves the average heat transfer. Moreover, a shorter distance from the tank wall generates a velocity field that laterally diverts the plume that forms around each turn. Hence, the heat transfer is enhanced because the preheating effect from downstream turns is mitigated, while the velocity gradients are strengthened. Additionally, a condenser design is proposed with geometric parameters that promote effective heat transfer, and the performance is compared against a reference design with geometric parameters that limit the heat transfer but are common in commercial solutions. The proposed geometry has a 43% increase in the Nusselt number, with respect to the reference geometry. Also, based on a dynamic simulation model of heat pump performance, it is determined that, for the same operating conditions, the proposed geometry improves the overall coefficient of performance (COP) of the system by up to 7%. These results highlight the importance of the geometric design of the condenser in heat-pump water heating systems, since they can contribute to a better overall performance and a more efficient thermal storage.

Variable Layer Heights in Wire Arc Additive Manufacturing and WAAM Information Models

In Wire Arc Additive Manufacturing (WAAM), variable layer heights enable the non-parallel or non-planar slicing of parts. In researching variable layer heights, this paper documents printing strategies for a reference geometry whose key features are non-orthogonal growth and unsupported overhangs. The complexity of 3D printing with welding requires parameter optimization to control the deposition of molten material. Thus, 3D printing with welding requires the precise deposition of molten material. Currently, there is no standard solution for the customization of process parameters and intelligent collection of data from sensors. To address this gap in technology, this research develops an Internet of Things (IoT)-enabled, distributed communication protocol to control process parameters, synchronize commands, and integrate device data. To intelligently collect sensor information, this research creates a query-able database during pre-planning and production. This contributes to fundamental research in WAAM by documenting strategies for printing variable layer heights, the customization of control parameters, and the collection of data through a WAAM Information Model (WIM).

Neutronic analysis of a tokamak hybrid blanket cooled by thorium-molten salt fuel mixture

In this study, a novel approach has been investigated by using a mixture of thorium and molten salts as a dual-purpose coolant and medium for the production of fissile fuel in a Fusion Fission Hybrid Reactor (FFHR) for the reference geometry of ITER. The study highlighted the broader benefits of thorium fuel cycling, safety features, and reduced radioactive minor actinides generation. The use of a thorium-melted salt coolant for fissile fuel production in a fusion-fission hybrid reactor represented a promising path towards efficient and sustainable nuclear energy, with potential benefits in terms of safety features and reduced generation of radioactive minor actinides. In this study, SS 316 LN-IG was selected as the first wall material for the reactor, and a molten salt fuel mixture of LiF–ThF4 was used as the coolant, taking into account the eutectic points of the material, the nominal fusion power in the FFHR for the Tokamak design concept is considered to be 500 MW. The nuclear code MCNP6 was used with the nuclear data libraries ENDF/B-VIII and CLAW-IV for the neutron calculations. The time evolution of the isotopes in the reactor was calculated with the interface code MCNPAS. The study results are evaluated in terms of tritium breeding ratio, energy multiplication factor, radiation damage, fissile fuel production and fuel burn-up value.The 4-year operation history of total TBR value is calculated and always above 1.05 and increases with time.Th initially decreased from 631.3 tonnes to 587.2 tonnes, while 233U production during this period was 9.1 tonnes. According to these results, the first wall replacement period was calculated as 3.9 years.

The nucleosome reference frame and standard geometries for octasomes.

There are over 533 nucleosome structures in the Research Collaboratory for Structural Bioinformatics (RCSB). Collectively, numerous variants and species are present, as are sub-nucleosomal and super-nucleosomal assemblies within the nucleosome family. The organization of the histones and DNA is highly conserved in all standard octasomes containing 145, 146, or 147 base pairs. This observation is used to establish a nucleosome reference frame that enables us to describe and compare the gross structure and organization of all nucleosomes. We observe that cumulative sums of Rise, Twist, and DNA arc length are linear functions of the base pair index with values exceeding 0.999 for almost all octasome structures. These relationships enable us to readily compare the location and orientation of DNA director frames extracted from the crystal structures to ideal superhelix values. Such comparisons reveal that the DNA superhelix extracted from X-ray structures exhibits a sinusoidal variation with an amplitude of approximately 5Å about a constant superhelix radius of Å, in agreement with early descriptions of nucleosome organization as tripartite. There is also a distinct straightening of the nucleosomal DNA over the outermost turn of DNA's double helix. The straightening of the DNA superhelix marks the transition to linker DNA and is easily recognized as a rapid increase in superhelix radius and is concomitant with a change in pitch. This provides a rigorous means of separating nucleosomal DNA from linker DNA. For all X-ray structures, we find that near the dyad, there exists a set of DNA director frames for which the spatial location and orientation are highly conserved. Away from the dyad, the DNA superhelix exhibits "singletrack" and "multipath" regions. In the singletrack region, all structures exhibit a single highly conserved pathway along which all base pairs must track, but at varying rates. In the multipath regions, the base pairs are allowed to map out a limited number of different pathways along the surface of the histone octamer. To demonstrate the utility of the proposed reference geometries, standard and distorted octasome structures, super-nucleosomal structures, nucleosomes with linker DNA, and nucleosomes in closed circular DNA are analyzed. The online version contains supplementary material available at 10.1007/s12551-024-01206-5.

Towards a machine-learned Poisson solver for low-temperature plasma simulations in complex geometries

Poisson’s equation plays an important role in modeling many physical systems. In electrostatic self-consistent low-temperature plasma (LTP) simulations, Poisson’s equation is solved at each simulation time step, which can amount to a significant computational cost for the entire simulation. In this paper, we describe the development of a generic machine-learned Poisson solver specifically designed for the requirements of LTP simulations in complex 2D reactor geometries on structured Cartesian grids. Here, the reactor geometries can consist of inner electrodes and dielectric materials as often found in LTP simulations. The approach leverages a hybrid CNN-transformer network architecture in combination with a weighted multiterm loss function. We train the network using highly randomized synthetic data to ensure the generalizability of the learned solver to unseen reactor geometries. The results demonstrate that the learned solver is able to produce quantitatively and qualitatively accurate solutions. Furthermore, it generalizes well on new reactor geometries such as reference geometries found in the literature. To increase the numerical accuracy of the solutions required in LTP simulations, we employ a conventional iterative solver to refine the raw predictions, especially to recover the high-frequency features not resolved by the initial prediction. With this, the proposed learned Poisson solver provides the required accuracy and is potentially faster than a pure GPU-based conventional iterative solver. This opens up new possibilities for developing a generic and high-performing learned Poisson solver for LTP systems in complex geometries.

Life cycle assessment of lead‐free potassium sodium niobate versus lead zirconate titanate: Energy and environmental impacts

AbstractOver the years, lead‐based piezoelectric ceramics found extensive use in vital fields such as sensors and actuators. Despite their exceptional electromechanical properties, lead‐containing materials pose severe environmental risks and foster a new era of lead‐free piezoelectric materials after decades of research. However, recent comparative assessments of potassium sodium niobate (KNN) versus lead zirconate titanate (PZT) piezoelectric materials proposed that the environmental damage already presented before use due to raw material extraction and processing, invoking concerns on the true greenness of the lead‐free alternatives. Nevertheless, many other factors deserve further consideration, for example, reference geometry and life cycle stage. Herein, the comprehensive life cycle assessment is undertaken on PZT and KNN‐based ceramics with a unit volume of 0.001 m3 from cradle to gate. Results show that PZT exhibits higher negative impacts than KNN‐based counterparts, attributed to lead extraction, processing, and associated environmental emissions. Across primary quantitative impact indicators from toxicity, environmental, and resource aspects, KNN‐based ceramics impose fewer risks on the environment and human health, with the overall impact being only 28% of PZT ceramics. Still, more efficient methods are required for KNN‐based ceramics to reduce the high energy consumption and emission during extraction and purification of raw material Nb2O5. This work not only offers critical insights for material development but also serves as a multifaceted reference for advanced fabrication technologies.image

Computational Evaluation of Turbo- and Electric-Powered Simulators for Turbofan Wind Tunnel Test

Experimental testing of aircraft configurations requires the use of representative engine units to simulate powered-on conditions. For ultra-high-bypass-ratio engines featuring tighter aircraft integration, the installation effects need to be carefully assessed. This paper presents a computational evaluation of two powered simulator models for wind tunnel tests of an ultra-high-bypass-ratio turbofan, based on a traditional air-driven turbo-powered simulator (TPS) and an electric-powered simulator (EPS). Starting from two-dimensional axisymmetric analyses, the design of the baseline turbofan engine and the choice of the duplication parameters of the simulators are described. Several aspects related to the nonreproducibility of the core flow at wind tunnel level are discussed, in terms of mass flow matching, TPS core nozzle pressure ratio, and plug shape of the EPS. The EPS can provide a more faithful reproduction of the flowfield under installation, with an estimated installation drag from 4 to 2 drag counts lower than the reference geometry, compared to the 6 drag counts higher prediction of the TPS.

HORIZONTAL SINUSOIDAL WAVY FORM PLATE-FIN HEAT SINKS FOR NATURAL CONVECTION HEAT DISSIPATION

The plate-fin heat sink geometry was modified to have the fin form sinusoidal wave shape in the horizontal direction with twelve variations by amplitude and period changes. Three different wave periods and four different wave amplitudes were used. The purpose was to alter natural convection motion in favor of heat transfer effectiveness. The main performance indicator was the base-plate average temperature. The independent geometric parameters were experimentally examined in terms of the effectiveness of natural convection heat transfer by the measured average temperature values. Heat transfer by radiation was calculated by an analytical algebraic approach in order to obtain the Nusselt number solely based on convective heat transfer. Eight different heat inputs were used for each tested geometry to change the Grashof and Rayleigh numbers in a laminar flow interval. As reference geometries, a flat plate and a heat sink with straight/flat-plate fins were utilized. The heat sinks were also oriented to three different angles by a test stand. Accordingly, thirty six unique experimental cases were examined as a result of 327 trials and 1100 hours of testing. It was realized that the wavy fin geometry enhances natural convection heat transfer compared to the base-plate and flat-plate-fin heat sinks. However, increasing period and amplitude of the wave form more than initial values deteriorated the gains by the modifications on the fins. Since a single-period, 2-mm-amplitude heat sink resulted in the highest Nusselt number for all orientations, an optimum may be sought about this setting. As a general evaluation, computational simulations for spatial resolution of the event physics and dimensional optimization are standing as future study targets.

Kiosk 6R-TA-12 - The Analytical Aortic Valve (AAV): A Novel Aortic Sinus 3D Reference Geometry Correlates with NYHA Functional Class and Other Clinical Features of Patients with Bicuspid Aortic Valve

Kiosk 6R-TA-12 - The Analytical Aortic Valve (AAV): A Novel Aortic Sinus 3D Reference Geometry Correlates with NYHA Functional Class and Other Clinical Features of Patients with Bicuspid Aortic Valve

ANALISIS CFD PADA SAYAP MINI GLIDER DENGAN PENAMPANG LOW REYNOLD NUMBER AIRFOIL DAN FOLDED FLAT PLATE AIRFOIL

The purpose of this research is to make a very small unmanned aircraft as a teaching aid in aerospace engineering workshops, because of its very small size, this type of unmanned aircraft is abbreviated as Micro Air Vehicle, this MAV is only operated at low Reynolds numbers. MAV development research for smaller sizes continues to be carried out such as the Micro Glider. In this study, the author uses the Computational Fluid Dynamic method and the software used ANSYS Fluent and compares the existing DATCOM data, the author simulates the 4 types of airfoils into a wing object. The results of this study can be seen that based on the average deviation diff value that has been obtained in a population to determine the error from the comparison of the reference airfoil lift coefficient and its FFP by comparing the two methods, namely the IISHI airfoil reference geometry is 6.22% while the FFP is is 11.25% and the SD 7037 airfoil reference geometry is 3.71% while the FFP is 2.11%. Then for the comparison of the maximum lift to drag ratio values, it is obtained that the airfoil reference geometry (SD 7037) has a value of = 9.96 while the airfoil reference geometry (IISHI) has a value of = 8.81. In the Folded Flat Plate airfoil geometry (SD 7037) it has a value of = 7.61 while the Folded Flat Plate airfoil (IISHI) has a value of = 7.37. Then for the visualization of fluid flow can be obtained, namely the results of visualization of fluid flow in several parts of the angle of view / plane of the wing geometry when the AoA is high, namely the root plane to the half wing plane. early, while the geometry of SD 7037 (airfoil reference) is not easy to occur early turbulence flow. Second, that in general the fluid flow pattern seen in the FFP airfoil geometry (FFP IISHI) has the most dominant turbulence flow pattern (very much/large) while the FFP airfoil geometry (FFP SD 7037) has very little/small turbulence flow pattern..

Analysis Options for Urban Green Spaces Based on Unified Urban Masks: Selected Results for European Cities

At a time of rising urbanisation and climate change, urban green spaces (UGSs) are an essential element to help adapt to extreme weather events. Especially in urban core areas, heat and drought are regarded as human stress factors. The delineation of such areas constitutes an important reference geometry in topographic geodata (urban mask). This article deals with possibilities for investigating UGSs in European cities—based on unified urban masks—by applying city-wide metrics to Copernicus data (Urban Atlas including the Street Tree Layer). Both public and tree-covered urban green spaces are examined in detail. Selected results are presented for 30 European cities that display a wide range of urban structures. The spatial reference to uniformly delineated urban masks places the analytical focus of city-wide metrics onto corresponding core areas. In general, the values of UGS metrics vary considerably between cities, indicating the strong influence of city-specific factors on urban structures in Europe. For the comparative analysis of tree-covered urban areas, the Urban Green Raster Germany and a municipal tree register are used to provide additional data sources. The regular updating of the Copernicus dataset means that green spaces in European cities can be monitored, also using urban masks.

A Comparison of Steam Turbine Control Valve Geometries and Their Dynamic Behavior at Part Load

A growing significance of flexible steam turbine operation challenges the control of turbines, as part load operation using control valves can be accompanied by highly unsteady flow conditions. The increased dynamic load induced by pressure forces can reduce the reliable operating range, weaken the valve, and lead to mechanical failures. The geometry of the valve plays a major role in the reduction of dynamic forces. Using a scaled control valve, experiments were conducted with a focus on the dynamic behavior of the valve head. A spherical valve shape favoring unstable operation was used as a reference case, and the desired instability was proven by measurements. Different modified valve geometries based on literature featuring separation edges were then tested against the spherical shape. Results indicate the improved stability of the modified geometries over the reference geometry. For most of the operating range, vibrations were drastically reduced, and the overall flow stabilized.

Investigation of the Influence of Inner Geometries of the Receiver Tube of a Parabolic Trough Collector System Used for Water Heating

Solar collectors are devices that help to harvest solar thermal radiation and convert into other forms of energy. Because of its low fabrication cost and simple design, the Parabolic Trough Collector (PTC) is one of the finest alternatives for medium-temperature (i.e., in 80°𝐶𝐶-250°𝐶𝐶 range) needs among all types of concentrated solar collectors. The absorber tube or the receiver tube is one of the main critical components of a PTC. Thermal radiation of the sun falling onto a parabolic reflector is reflected to its focal line where the receiver tube is placed. Therefore, the performance of a PTC system significantly depends on Receiver Geometries (RGs). A locally developed PTC system with a new and accurate tracking system was designed and fabricated in the current study and steam generation inside the receiver was considered in the performance analysis. The experimental analysis was performed using seven different RGs. The experiments were carried out by measuring generated steam every 10 minutes for all the RGs, and simultaneously, solar insolation data was taken by a domestic solar Photovoltaic (PV) system with a capacity of 5 kW. The steam generation data was taken only when the power output of the reference solar PV system was ≥ 4kW. Having tested seven different RGs, the researchers were able to improve the steam generation to a maximum of 10.0% compared to the reference geometry using direct experimental data. This was 8.1% in accordance with the statistical approach via multiple linear regression model. A three-dimensional mathematical model for two-phase flow was formulated for a closed domain. Restricting this model into twodimensional geometry, the steam generation process was simulated as a TPF problem using ANSYS Fluent software. The volume fraction profiles clearly show the phase transition, which leads to evaporation and condensation inside the tube.

Efficiency Enhancement of Marine Propellers via Reformation of Blade Tip-Rake Distribution

This work addresses the effects of blade tip-rake reformation on the performance of marine propellers using a low-cost potential-based vortex-lattice method (VLM) and the high fidelity artificial compressibility CFD-RANS solver MaPFlow. The primary focus lies on determining whether the low-cost VLM, in conjunction with a multidimensional parametric model for the tip-rake and pitch/camber distributions, can produce a propeller geometry with improved efficiency. Due to the availability of experimental and numerical data, the NSRDC 4381-82 propellers were selected as reference geometries. Torque minimization serves as the objective function in the gradient-based optimization procedure under a thrust constraint, which translates into efficiency enhancement at the selected design advance ratio. The optimized 4381 propeller yields a +1.1% improvement in efficiency based on CFD-RANS, whereas for the modified skewed 4382 propeller, the efficiency gain is +0.5%. The performance enhancement is also evident at a region near the design advance ratio. The results suggest that the exploitation of low-cost VLM solvers can significantly reduce the CFD simulations required in the optimization process and thus can be effectively used for the design of propellers with tip-rake reformation.

Optimization of rifled tube by parametric changes using CFD for goodness factor enhancement

AbstractIn this study, extensive research was conducted using computational fluid dynamics (CFD) ANSYS®–FLUENT, with the k–ε turbulence heat transfer module to optimize the rifled‐tube heat exchanger through parametric modifications for heat transfer and Goodness factor enhancement. This is based on predicting the performance of various heat transfer surfaces such as rectangular and two opposite right‐angled triangular ribs. The objective of this research was to enhance the heat transfer efficiency of a rifled tube with rectangular ribs, a height of 0.775 mm, and helix angles of 30° and 58°. The research findings demonstrated that the heat transfer rate improved owing to the establishment of a secondary helical or swirl flow near the wall region, leading to an enhanced heat transfer. The modification of the rib geometry from rectangular to two opposite right‐angled triangles increased the heat transfer by 17%, whereas the pressure drop remained relatively constant at 0.62 mm of rib height. This benefit is directly translated into heat transfer without any change in pressure drop. The values of the friction factor (f), Nusselt number (Nu), and goodness factor are appropriate for the new geometry in relation to the reference geometry. Rifled‐tube designers can use CFD heat transfer analysis to optimize the design, reduce the need for physical prototypes, and test similar applications and rib configurations.

Numerical investigation on the high-velocity impact resistance of textile reinforced composite mesh designs inspired by spider web

The need for thin and highly deformable textile reinforcements is constant in sectors like thin composites, catching nets, and complex construction designs (like dome-shape). The conventional rectangular-patterned meshed wovens are used in thin composite structures as reinforcement at the commercial level. These woven textiles are bidirectional and exhibit approximately the same strength along both axes. However, these conventional rectangular-patterned mesh designs show poor impact stress distribution capacity. Interestingly, very thin and fine mesh designs are available in nature. One such example is the spider web structure. These structures have evolved with time and optimised their mesh pattern design for better impact damage resistance and load transfer. In this study, the basalt fibre reinforced mortar textile composites are considered for the investigation due to their growing interest in civil and construction applications. To demonstrate how the mesh geometry in textiles significantly influences the stress transfer, energy absorption, and deformation of reinforcements under various impact situations, three different geometries, (a) square shape mesh, (b) diamond-shaped mesh, and (c) bio-inspired spider web mesh, are modelled and meshed based on the reference geometry’s meshing pattern and dimensions. The results of numerical simulations show that a meshed reinforcement design inspired by spider-orb-web has improved mechanical features compared to conventional square and diamond shape mesh designs under high velocity impact loading.