Shape Configuration Research Articles

Approximation of blades of radial machines with multiparameter family of smooth surfaces

Purpose. Development of a mathematical model for creating the spatial forms of blade devices of rotating radial dynamic blade machines. Methodology. An approach to the development of a mathematical model of blade profiling of radial dynamic blade machines, as parts of power plants, air-jet engines and fuel component supply systems of rocket engines, has been suggested. The approach is based on a physical model of the working body flow over helical surfaces. Findings. A system of equations for describing the blade of a radial dynamic blade machine of any purpose as a family of smooth surfaces has been obtained. A multi-parameter correction of the shape of the smooth surface of the blade, accounting for the change in geometric data, based on input and output parameters of the blade, has been developed. Based on a review of modern technology samples, possible configurations of the spatial shape of the blade of the radial and radial-axial type, geometric factors affecting the surface of the blade being created are taken into account. The possibility of obtaining a multi-level blade apparatus by changing the conditions of the geometric parameters at the entrance is shown. Originality. As part of the developed approach, in relation to the conditions for ensuring the calculated geometric parameters and the working process conditions of the blade machine, blade machines operating on compressible and non-compressible working bodies are considered. In particular, the possibility is shown of ensuring the construction of the spatial surface of the blade of the impellers of radial blade machines with a wide range of angles of the blades at the entrance and exit using smooth surfaces. Practical value. The use of a developed mathematical method allows you to perform the profile of rotating vane devices for radial vane dynamic machines of various purposes, such as centrifugal pumps and compressors, centrifugal radial turbines, as well as diagonal type vane machines. The practical significance of the obtained results is determined by the use of dynamic radial vane machines in aviation and rocket technology, aggregates of the mining industry, and technological devices of chemical industry enterprises.

Stability Analysis of Thin-Walled Perforated Composite Columns Using Finite Element Method.

Open holes or cut-outs have been commonly used in composite structures for various engineering purposes. Those elements often demand perforation especially for weight reduction and to ease maintenance and servicing operations, for example, in aircraft wing ribs. This work presents a numerical study of the stability behavior of composite perforated columns subjected to a compressive load. Profiles were made of CFRP laminate and weakened by three types of cut-out. Four parameters, spacing ratio S/D0, opening ratio D/D0, hole shape and arrangement of layers, were selected to check their effect on the buckling load and postbuckling behavior of the tested channel profiles. To carry out the numerical analysis, the Abaqus software was used. The results obtained during the analysis helped to identify the best combination of tested parameters to obtain the highest critical load. The performed analysis show that the columns' behavior is sensitive to configuration of composite, opening ratio and hole shape.

Acoustic modes of a spherical thin-walled tank for liquid propellant mass gauging: Theory and experiment.

Acoustic response of a thin-walled spherical flight tank filled with water is explored theoretically and experimentally as a testbed for an application of Weyl's law to the problem of mass-gauging propellants in zero-gravity in space. Weyl's law relates the mode counting function of a resonator to its volume and can be used to infer the volume of liquid in a tank from the tank's acoustic response. One of the challenges of applying Weyl's law to real tanks is to account for the boundary conditions which are neither Neumann nor Dirichlet. We show that the liquid modes in a thin-walled spherical tank correspond to the spectrum of a slightly larger spherical tank with infinitely compliant wall (Dirichlet boundary condition), where Weyl's law can be applied directly. The mass of the liquid enclosed by this "effective" tank's wall is found to equal the actual mass of the liquid plus the mass of the wall. This finding is generalized to thin-walled tanks and liquid configurations of arbitrary shapes and thus provides a calculable correction factor for the propellant mass inferred using Weyl's law with Dirichlet boundary conditions.

Dual-Segment Continuum Robot With Continuous Rotational Motion Along the Deformable Backbone

The hyper redundancy and flexibility of continuum robots have made them attractive to replace conventional rigid-link robots in many applications. Although the robot body can be bent to different directions as needed, rotation along the backbone is not a feature available in many continuum robot designs. In this article, we propose a pneumatic-driven, dual-segment continuum robot with the capability of providing continuous rotation along the deformed backbone (CRADB) at a particular point. A slip ring was employed to enable rapid coupling/decoupling between the air supply and different chambers of the robot, while a stepper motor with adjustable speed was adopted to provide the additional rotational motion. A novel control scheme based on optimization was developed to compute the required shape configuration under different modes. Control schemes toward fast deformation motion and CRADB motion have been, respectively, built. Experiments were conducted to compare the performance in positioning the robot’s tip with and without the additional degree of freedom. The ability to enable continuous rotation after positioning at different points was also tested to demonstrate its performance in various potential applications.

Effect of modifications to island shape and geometrical configuration on the external aerodynamics of a generic aircraft carrier

The external aerodynamics of an aircraft carrier plays a vital role in the safe landing of aircraft during take-off and recovery. The hull, flight deck, and the island create a turbulent disturbance behind the aircraft carrier, leading to a simultaneous reduction in forward velocity and a downwash, which together create a sinking effect on the aircraft along its glideslope path. This phenomenon is known as the burble effect. It could potentially increase the pilot’s workload and strain their mental and physical faculties. Any design change that obviates or reduces the burble effect would potentially increase the probability of safely landing the aircraft on an aircraft carrier. There are only a few studies on the external aerodynamics of an aircraft carrier. The primary motivation of this study is to evaluate the effect of modifications to the island structure on the external aerodynamics of a generic aircraft carrier, especially the burble behind the carrier. The first part of the study pertains to the parametric changes to the aspect ratio of the island, that is, its length to width ratio and the consequent impact on the aerodynamics behind the carrier along the flight glide path. The second part of the study focuses on changing the geometry of the island by rounding the assumed cuboid island’s sharp corners, and evaluating its effect on the burble along the glideslope path of the aircraft. For the study, computational fluid dynamics (CFD) analysis on a generic aircraft carrier model has been carried out using the commercially available CFD solver Ansys FLUENT. The CFD studies have been validated by results of experiments conducted in a wind tunnel on the same generic aircraft carrier model. From the studies, it is seen that the aspect ratio of the island greater than one and rounding the sharp edges of the island have beneficial effects in reducing the impact of the burble behind the carrier.

Investigation of octupole collectivity near the A=72 shape-transitional point

Enhanced octupole collectivity is expected in the neutron-deficient Ge, Se and Kr isotopes with neutron number $N \approx 40$ and has indeed been observed for $^{70,72}$Ge. Shape coexistence and configuration mixing are, however, a notorious challenge for theoretical models trying to reliably predict octupole collectivity in this mass region, which is known to feature rapid shape changes with changing nucleon number and spin of the system. To further investigate the microscopic configurations causing the prolate-oblate-triaxial shape transition at $A \approx 72$ and their influence on octupole collectivity, the rare isotopes $^{72}$Se and $^{74,76}$Kr were studied via inelastic proton scattering in inverse kinematics. While significantly enhanced octupole strength of $\sim 32$ Weisskopf units (W.u.) was observed for $^{72}$Se, only strengths of $\sim 15$ W.u. were observed for $^{74,76}$Kr. In combination with existing data, the new data clearly question a simple origin of enhanced octupole strengths around $N = 40$. The present work establishes two regions of distinct octupole strengths with a sudden strength increase around the $A=72$ shape transitional point.

Scaling of Anisotropic Wetting Behavior of Water Drop Configuration Arising from Parallel Groove-Textured Stainless Steel Surfaces

Understanding the wetting behavior of stainless steel surfaces can help in resolving many socio-economic challenges faced by modern day engineering developments. In this research paper, investigations have been carried out to understand the role of surface unidirectional microgrooves on the wetting behavior by the water drop liquid using the liquid drop shape configuration, captured in the view direction parallel and orthogonal to surface microgrooves. Because of the variation in wetting characteristics between these two directions, i.e., anisotropic wetting behavior, the liquid drop has attained ellipsoidal shape configuration in the microgroove-textured stainless steel surfaces. Detailed investigation has been carried out in understanding the role of microgroove geometrical sizes, i.e., width and depth and the spacing between the grooves on the wetting behavior in terms of contact diameter (D) and contact angle (θ). Overall, the wetting dynamics has been characterized by looking at the variation of eccentricity (ε, as a ratio between D in the direction parallel to microgroove and the spreading diameter in the direction orthogonal to microgroove) and wetting anisotropy (Δθ, as a difference in θ between the direction orthogonal and parallel to microgroove) with the microgroove depth parameter (ϕ as a ratio between the microgroove depth and width) and the groove spacing parameter (ξ as a ratio of the spacing between the grooves and the groove width). By and large, with increase in surface non-dimensional geometrical parameters, ϕ and ξ, the parameters quantifying eccentricity, ε and Δθ decrease, so the liquid drop shape configuration shifts towards spherical cap from ellipsoidal cap.

Numerical simulation of anti-sloshing performance in a 2D rectangular tank with random porous layer

The porous media theory is extensively used to simulate the porous structures due to the complexity of the shape and grain configuration. In this study, The open-source code OpenFOAM was firstly extended to solve the interaction between the sloshing flow and the random porous structure, and the accuracy of the extension was validated by comparing the numerical results with experimental data. In addition, the effect of porosity, average diameter of the porous structure was analyzed, and then the anti-sloshing performance of rectangular tank for different excitation frequencies and distances between the random porous structure and the nodal line of eigenmode (m = 1) was also discussed. After that, a comparison of the wave-damping performance between the random porous layer and the traditional perforated baffle was conducted. Results indicated that the random porous structure with porosity (n) of 0.2 and average diameter (d50/b) of 0.85 has the best anti-sloshing performance, and the anti-sloshing performance of random porous layer is generally decreased when the excitation frequency moves close to the first-order natural frequency, and it is decreased with the increasing distance. A better wave-damping performance of the present random porous structure can be observed when compared with traditional perforated baffle.

Flow and baffle configurations of settling pond and low-flow reactor for water treatment

Substrate reactors used to treat water have generally been vertical, and many settling ponds have zigzag baffles to increase the actual residence time. To improve the shape and flow configurations, baffle-type, weir-type, column-type, and SAPS-type reactors and settling ponds with zigzag and hanging baffles were studied by bench-scale and pilot-scale experiments and theoretical considerations. Tracer tests indicated that the extension of the flow line by zigzag baffles could prevent the short-circuiting of the SAPS-type reactor. The pilot-scale reactor with baffles in the longitudinal direction exhibited the highest treatment efficiencies among the baffle-type, weir-type, and column-type reactors. Nevertheless, the required hydraulic head is a critical constraint in the application of various types of reactors. The relationship between the maximum flow rate and the difference in hydraulic head or hydraulic conductivity indicated applicable flow rates for the baffle-type and weir-type reactors. If the hydraulic head difference is sufficiently high by pumping or the flow rate is sufficiently low, application of zigzag baffles in the longitudinal direction is highly encouraged in substrate reactors. Furthermore, pilot-scale experiments with a settling pond with zigzag baffles and hanging baffles indicated that the prevention of surface flow by using the hanging baffles reduced the required residence times to 51 %–69 % of those of zigzag baffles. The increased efficiency of the suggested reactors and settling ponds will decrease the required area and cost of construction.

Experimental investigation of the film cooling performance by triangular-shaped thin plates on inclined cylindrical holes

Experimental investigations have been conducted to improve the cooling effectiveness of film-cooling technology. A multiple row of cylindrical holes at the flat surface was considered by inclining the holes at 35° along the streamwise direction. A low-speed wind tunnel with the main flow speed of 10 m/s was devised to create a cross flow at a Reynolds number of 196,167 and five blowing ratios of 0.3, 0.5, 0.7, 1, and 2. The proposed triangular-shaped thin plate and flop at the cylindrical film cooling hole were investigated using flow visualization and thermographic techniques. The resulting cooling performances were also experimentally evaluated and compared with respect to the different film-cooling hole configurations. The typical film cooling hole configuration of cylindrical hole shape shows the cooling effectiveness of 0.1 at blowing ration of 1.0. It should be denoted that this cooling effectiveness is exemplary value of wide range of gas turbine applications. We also experimentally evaluates the cooling effectiveness in order to valid our experimental method. Meanwhile, with triangular-shaped thin plate-flop, the flow detachment is successfully prevented with requiring 8% increase of discharge coefficient. In addition, the film flow is stable even at the distant downstream, resulting in enhanced cooling performance compared to the cylindrical and triangular-shaped thin plate. Consequently, a 242.7% improvement in film cooling effectiveness can be achieved with a triangular-shaped thin plate-flop than with a cylindrical hole owing to its enhanced film coverage.

SPILLMOD – МОДЕЛЬ ГИДРОДИНАМИЧЕСКОГО ТИПА ДЛЯ ИНФОРМАЦИОННОЙ ПОДДЕРЖКИ РЕАГИРОВАНИЯ НА РАЗЛИВЫ НЕФТИ В МОРЕ

A mathematical model of the evolution of marine oil spills with taking into account the processes of spreading and weathering, has been implemented as a software package called SPILLMOD. In doing so, a new Eulerian-Lagrangian method for Computational Fluid Dynamics (CFD) has been developed in the context of solving shallow-water-type equations with the capability to handle the situation where advancing/vanishing layer of the light fluid (oil) only partially covers the heavy (water) in a domain with an arbitrary configuration of the coastline shape. When calculating the evaporation of high-viscosity oil types, the effect of reduction the evaporation rate due to molecular diffusion of lighter oil fractions within the oil layer is taken into account. Simulation of the natural dispersion of oil layer is carried out considering multiple factors, such as: sea surface conditions, experimental data on oil film crushing in the wave mixing layer, turbulent diffusion in the upper layer, as well as changes of physical and chemical properties of oil over time. An additional module in the model is designed to estimate domain boundaries of possible spill detection for different sources of uncertainties during oil spill modeling. Modeling examples of application in realistic configuration of port-water areas for an actually occurred emergency situation of oil spill demonstrate the declared qualities of the model as a tool for supporting emergency response operations.

Effect of Indenter Nose Shape and Layer Configuration on the Quasi-Static Perforation Behaviour of Metal-Plastic Laminates.

This study investigated the perforation resistance behaviour of metal–plastic laminates (MPLs) when they are indented by different nose shapes. Aluminium (Al) and HDPE (high-density polyethylene) layers were bonded with a suitable adhesive in an alternative manner to prepare bilayer and trilayer MPL configurations. Quasi-static perforation experiments were performed with hemispherical, conical and blunt indenters. The effects of nose shape, layer configuration and adhesive on the force–deformation profile, perforation resistance capacity and failure mechanisms were evaluated. The results indicate that for a monolithic layer, the blunt indenter showed the highest perforation energy capacity. The conical and blunt indenters facing Al backed by HDPE gave higher perforation energy. The hemispherical indenter facing HDPE backed by Al was found to be more effective in perforation resistance. Trilayer Al–HDPE–Al showed higher perforation resistance than HDPE–Al–HDPE. Circumferential cracking, radial symmetric cracking and shear plugging were the main failure modes for Al under hemispherical, conical and blunt indenters, respectively. The adhesive contributed to an increase in the perforation energy and peak force to failure in laminates. The adhesive was shown to detach from the Al surface after Al fracturing through crack propagation, and this effect was more pronounced when the indenter faced HDPE at the front of the laminate.

Anatomic considerations for immediate implant placement in the mandibular molar region: a cross-sectional study using cone-beam computed tomography

There is concern regarding immediate implantation in the molar region because of discrepancy between socket size and inserted implant diameter. The purpose of this study was to assess the local anatomy of the posterior mandibular region in relation to immediate implant placement using cone-beam computed tomography (CBCT). Using CBCT imaging data, 204 mandibular first molars and 201 mandibular second molars were assessed for the interradicular and alveolar bone dimensions, tooth sizes and proximity to vital structures. The cross-sectional mandibular shape and root configuration of these molars were determined. Distances to the inferior alveolar canal (IAC) from the root apices of the first molar were significantly greater than the second molar. Up to 14.5% of second molars had less than 10 mm of vertical bone height between the IAC and furcation bone crest. Interradicular bone width of < 3 mm was found in 57% of second molars. All first molars in this study had two to three roots while 16% of second molars presented with a single root. The prevalent mandible shape at the first and second molars was the parallel and undercut ridges, respectively. The mandibular second molars from samples of a Southeast Asian population presented with greater anatomical difficulties for immediate implant placement which include absent or inadequate interradicular bone thickness, higher incidence of unfavourable mandible shape and increased proximity to vital structures.

Wpływ kształtu wzmacniających profili okiennych na wytrzymałość i sztywność skrętną okien

Leading European manufacturers of profiles intended for the production of construction joinery currently use mainly PVC profiles with various configurations of external and internal shapes, allowing the production of functional products due to their intended use, shape, possibility of building them, maintaining color and maintaining low thermal transmittance coefficients of profiles. It is important to obtain high cross-sectional strengths, especially for torsion and bending. It is related to high wind loads of structures. A profile is made of a PVC with a low Young’s modulus compared to other materials, and thus it has low stiffness and strength indicators. This leads to relatively easy deformation of the joinery profiles during assembly. To avoid this unfavorable effect, the PVC profiles are reinforced with steel sections. Currently, in the industry producing PVC profiles, open steel reinforcement profiles are almost exclusively used. This solution is very disadvantageous for reasons of stiffness. However, manufacturers use such profiles primarily for technological and price reasons. Closed profiles pose many technological problems in their production and are approx. 30% more expensive compared to the corresponding open profiles. This paper presents research on the use of closed steel stiffening sections in place of open profiles. The main advantage of stiffening closed profiles is many times greater bending and torsional stiffness compared to open profiles. The theoretical and experimental studies carried out for selected cross-sections have shown that the stresses in a closed profile are several times lower than in an identical open profile, and the torsional stiffness of a closed profile is even several dozen times higher than that of an identical open profile.

Optical Bistability in a Tunable Gourd-Shaped Silicon Ring Resonator.

In this study, a tunable gourd-shaped ring resonator is demonstrated to generate optical bistability. The system consists of two sub-rings for a gourd shape configuration with a U-shaped wave guiding pathway. The transfer matrix method and FDTD simulation are used to acquire the spectral characteristics of the system. For the fabricated device, the spectra profile and extinction ratio can be effectively tuned by the microheater above the U-shaped waveguide, which matches with the theoretical results. Due to the gourd structure of the resonator, the light waves in two rings can be cross-coupled with each other, and the optical bistability could come out effectively with the change in the input optical power around 6 mW. The presented optical bistability devices have great application potential in optical information processing such as optical storage, switch and logic operation.

Deep Learning-Accelerated Designs of Tunable Magneto-Mechanical Metamaterials.

Metamaterials are artificially structured materials with unusual properties, such as negative Poisson's ratio, acoustic band gap, and energy absorption. However, metamaterials made of conventional materials lack tunability after fabrication. Thus, active metamaterials using magneto-mechanical actuation for untethered, fast, and reversible shape configurations are developed to tune the mechanical response and property of metamaterials. Although the magneto-mechanical metamaterials have shown promising capabilities in tunable mechanical stiffness, acoustic band gaps, and electromagnetic behaviors, the existing demonstrations rely on the forward design methods based on experience or simulations, by which the metamaterial properties are revealed only after the design. Considering the massive design space due to the material and structural programmability, a robust inverse design strategy is desired to create the magneto-mechanical metamaterials with preferred tunable properties. In this work, we develop an inverse design framework where a deep residual network replaces the conventional finite-element analysis for acceleration, realizing metamaterials with predetermined global strains under magnetic actuations. For validation, a direct-ink-writing printing method of the magnetic soft materials is adopted to fabricate the designed complex metamaterials. The deep learning-accelerated design framework opens avenues for the designs of magneto-mechanical metamaterials and other active metamaterials with target mechanical, acoustic, thermal, and electromagnetic properties.

Shape-based approach to attitude motion planning of reconfigurable spacecraft

Internal torques generated from shape reconfiguration can be helpful in Micro-Satellite attitude control. The configuration-attitude-coupled non-holonomic dynamics of a multi-body spacecraft is investigated. A shape-based motion trajectory in the form of water drop curve is proposed to synchronously reach target attitude and target shape configuration. With the shape-based approach, the motion planning problem is converted into a system of non-linear equations in three unknowns. The advantages of this approach is demonstrated from the views of simplicity, reachability, and efficiency. Simulations are conducted to test the planning function, and the results are compared with those obtained from the optimal control method.

Recent Advances on Synthesis of CoCO3 with Controlled Morphologies.

Cobalt carbonates and derivatives represent most promising cost-effective materials for energy storage, conversion and upgrading. Morphology determines the performances, as size, shape and electronic configuration are key factors for tunable properties in the area of batteries, catalysis, magnetics and plasmonics. However, there is lack of insights in literature on morphological control of cobalt carbonates during hydrothermal and solvothermal conditions. Therefore, this review provides detailed discussion on synthesis, formation mechanism and morphological control of nanosheets, wires, spheres and cubes of cobalt carbonates. Furthermore, the influence of experimental conditions and plausible mechanism which govern the growing processes were further discussed in details. The outcome of this short review will offer insights into rational design of inexpensive metal carbonates for numerous other energy and environment applications.

Optimizing within-distance queries by approximating shapes with maximal bounded boxes

Background: In geospatial query processing, spatial containment and intersection queries can be efficiently answered from the index. There is, however, a class of queries (such as within-distance) with a semantics that implies that every shape in the database is a potential match and should, in principle, be compared with the threshold. Naturally, this is impractical and optimizations have been developed that efficiently refine the set of candidate shapes before starting to actually compute distances and apply the threshold. In the case of the within-distance queries, many instances can be discarded in advance as too distant. Since geospatial databases organize data as a hierarchy of bounding boxes, this already provided the first direct optimization as the actual distance cannot be smaller than the distance between the bounding boxes. One can easily understand that there are shape configurations that give bounding boxes that are not very selective for near-by shapes. That is, configurations where there are shapes outside the requested distance but within the request distance from the bounding box. Methods: In this article, we investigate a further optimization in addition to and after comparing the bounding boxes, but before computing precise distances. We describe the distance optimizer operation currently used by PostGIS and show how the existing implementation prevails over approaches that use additional approximations. We implement a recursive algorithm to calculate the minimal possible largest inner rectangles of geometries. Results: We observe that the performance of the distance operation cannot be improved by using the inner approximations instead of the actual shapes. The overheads of the inner rectangles would not be recovered from calculating the distance between simpler geometries. Conclusions: The execution time of the distance operator has a small dependence on polygon complexity. Conclusively, an inner approximation for complex polygons cannot out-perform the standard PostGIS implementation.

The Role of Crystal Fraction to Relative Magma Viscosity: An Approach to Understand the Explosive Caldera-Forming Volcanism of Raung Volcano

Explosive volcanism is one of the deadliest volcanic hazards. The characteristics of the magma chamber that cause explosive eruptions need to be studied more deeply. Raung Volcano in East Java is an example of volcano that has a history of explosive eruptions that marked by a 2 km wide caldera. Petrographic analysis was carried out on selected 4 basaltic lava samples to determine the composition and proportion of minerals. Then, an analysis of the viscosity of the magma was carried out in relative terms using the shape and size configuration of the crystals. The comparison between the percentage of crystals and the relative viscosity value shows a positive correlation which indicates that there is an effect of the number of crystals on the viscosity of the magma. The increase in the viscosity of magma that occurred in the pre-caldera lava eruption of Raung Volcano indicates an intensive crystallization. This is supported by petrographic data which shows a porphyritic texture with a phenocryst of more than 40%. Plagioclase crystals become quite dominant crystals (> 30%). Based on this, it can be interpreted that the crystallization process occurred intensively in the shallow magma pocket of Raung Volcano.