Hole Shape Research Articles

Using a Bed Sill as a Countermeasure for Clear-Water Scour at a Complex Pier with Inclined Columns Footed on Capped Piles

River bridge piers may collapse due to the local scour around their foundations. It is known that local scour is an effect of the three-dimensional flow field that develops near the pier and that the geometric complexity of a non-cylindrical pier may, correspondingly, increase the complexity of the process. It is also known that various devices may be used as scour countermeasures. This manuscript explores the use of a bed sill as a countermeasure for local scour at a complex bridge pier compound of an array of piles, a pile cap, and two inclined columns with the rectangular sections above the cap. This pier geometry, never studied before in combination with a scour countermeasure, was stimulated by an existing bridge. Different sill placements were tested (at the upstream or downstream edges of the pier, or in an intermediate position) for various values of the pile diameter and number, cap thickness and cap elevation. The results of a wide experimental campaign consistently showed that the most effective placement of the transverse sill was at the upstream edge of the pier, for which scour reductions of up to 30–40% could be obtained for the long-term scour depth. The countermeasure performance decreased to about 10% when the sill was placed at the downstream edge of the pier. Furthermore, the installation of a transverse sill upstream of the pier also changed the shape of the scour hole because the pier was then located in an area prone to sill scour; however, for the present experiments, the combination of the effects was beneficial in terms of the resulting scour depth. Although the investigation of a single hydro-dynamic condition prevents the experimental findings from being generalized, the promising results stimulate further consideration of a transverse sill as a countermeasure for local scour at a complex pier.

К вопросу профилактики капсульного блока после факоэмульсификации катаракты с имплантацией заднекамерной интраокулярной линзы

Purpose. Method for the formation of anterior capsulorhexis for the prevention of capsular block in cataract phacoemulsification with implantation of a posterior chamber IOL was suggested. Material and methods. 67 patients (67 eyes) were operated on, for whom capsulorhexis was performed according to the method proposed by the authors in the form of an ellipse with a large axis of 7.0–7.5 mm along the tunnel incision and a small axis of 4.0–5.0 mm. Results. We did not observe any complications during the operation, as well as in the early and late postoperative period (damage to the anterior capsulorhexis, capsule block, bullous keratopathy, etc.). Only 2 patients (3%) were diagnosed intraoperatively with posterior capsule fibrosis, which required posterior capsulorhexis, which was performed after IOL implantation. At the same time, it should be noted that capsulorhexis was technically easier to carry out, since access to the posterior capsule was increased due to the previously performed oval anterior capsulorhexis. It was noted that the proposed method of forming the anterior capsulorhexis facilitates the insertion of the working part of the chopper over the edge of the lens when using the core fracture technique, reduces the risk of damage to the lens capsules, ensures reliable fixation of the IOL in the capsule bag and increases access for carrying out the posterior capsulorhexis, if necessary. After the operation UCVA and BCVA showed statistically significant increase, as much as possible after a month, but the difference with the data at the hospital discharge is statistically unreliable. After 1 year, visual functions remained stable, IOP was normalized. Conclusion. The proposed method for the formation of anterior capsulorhexis in cataract phacoemulsification with implantation of a posterior chamber IOL reliably eliminates the possibility of a capsule block due to the formation of an oval shape of the capsule hole. In addition, during the operation, it facilitates the insertion of the working part of the chopper over the edge of the lens when using the core fracture technique, reduces the risk of damage to the lens capsules, ensures reliable fixation of the IOL in the capsule bag by preserving sufficient peripheral flaps of the anterior capsule, and also increases access for posterior capsulorhexis under the IOL, if necessary. Keywords: cataract phacoemulsification, posterior chamber IOL, capsule block, oval capsulorhexis.

Strength and fatigue analysis of periodic perforated materials using the computational homogenization and ES-FEM approaches

This paper presents a computational homogenization shakedown analysis of periodic perforated materials with von Mises matrices. The plastic behaviors of the perforated materials under cyclic macroscopic loads are studied by means of kinematic shakedown theorem and computational homogenization method. The kinematic micro-fields are approximated by the edge-based smoothed finite element method. The resulting large-scale optimization problem is efficiently solved by using conic solver, enabling a large number of points on the macroscopic strength and fatigue surface to be calculated rapidly. The effects of the hole's shape and size on the overall strength and fatigue domains are also investigated.

Hydrothermal characteristics of turbulent flow in a tube with solid and perforated conical rings

Metallic inserts are well-recognized in modern research as efficient passive thermal performance enhancement methods. However, only scarce studies examined conical rings mainly due to the high corresponding pressure drop. This study aims to achieve a balanced hydrothermal performance using solid and perforated conical rings by focusing -for the first time- on the number and shape of holes in both convergent and divergent rings. The results show that larger Nusselt numbers (up to 360.2 at Reynolds number of 26,000) can be achieved using solid divergent rings due to thermal boundary layer disruption and near-wall flow acceleration, but this configuration also shows the highest friction factors (5.04 at Reynolds number of 6000). Perforating the rings reduces both Nusselt number and friction factor for more balanced performances, especially for higher numbers of holes. Circular and triangular holes result in the highest and lowest values of both parameters, respectively. A maximum thermal enhancement factor of 1.1 is obtained when using solid divergent rings at Reynolds number of 6000. However, a thermal enhancement factor of 1.06 can be achieved using circularly perforated rings with significantly lower pumping power requirements. When referencing solid rings instead of the plain tube, thermal enhancement factors can reach 1.2.

The Famenin fall and other ordinary chondrites intermediate between H and L groups

AbstractThe Famenin meteorite fell around 08:30 a.m. local time (GMT+4.5) on June 27, 2015 on the roof of a house in Famenin, a town in NW Iran. A single 640 g stone was recovered, shattered into several pieces upon impact. The shape of the impact hole and the relative position of the recovered meteorites indicate a N‐NW fall direction. Famenin is an ordinary chondrite (OC) with well‐preserved chondrules of various types, (Fe,Ni) metal, troilite, phosphate, and chromite. The organic matter systematics and the olivine and low‐Ca compositional distributions (percent mean deviations 18% and 31%, respectively) indicate it is a type 3.4/3.8 chondrite. Considering the average chemical compositions of olivine (Fa17.5±4.7) and low‐Ca pyroxene (Fs16.8±7.5), average Co content of the kamacite (5.6 mg g−1), and Cu/Ni and Ga/Ni ratios, Famenin should be classified as an H chondrite. However, saturation magnetization is 26.0 Am2 kg−1, indicating a bulk metal content similar to L chondrites. Similarly, the whole‐rock Ni and Co contents (13073 and 540 µg g−1, respectively), and average chondrule diameter (550 µm) are closer to typical values for L chondrites than H chondrites. The (Fe,Ni) metal modal abundance (5 vol%), magnetic susceptibility, and possibly whole‐rock oxygen isotopic composition indicate intermediate properties between H and L chondrites. Noble gas composition and cosmic‐ray exposure ages of Famenin and El Médano 195 (another intermediate OC) shows their gas‐rich character and an older ejection age from their parent body than those for the majority of H and L chondrites. Famenin, together with similar intermediate OCs, increases the diversity of this meteorite clan and suggests the existence of a separate OC group with a composition broadly intermediate between H and L groups for which a different designation (HL) is proposed. OCs likely originate from more than three parent bodies (H, L, and LL) as traditionally proposed.

A general solution for leakage through geomembrane defects overlain by saturated tailings and underlain by highly permeable subgrade

Experimental data is presented for leakage through slits, square, and rectangular geomembrane defects overlain by silty sand tailings and underlain by a well-graded gravel. The rectangular GMB defects have a range of widths, B, lengths, L, and aspect ratios (L/B), and ratios of defect length to thickness of tailings above the geomembrane (L/T). A blade cut slit (or simulated stress crack) widens to an extent dependant on the subgrade and stress level. For L= 100 mm, increasing B (0.15 < B/L ≤ 1) from 1.6 (slit) to 100 mm (square), decreases the leakage from about twice to essentially the same as that for a circular hole of equal area. The ratio (h1/H) of head loss within the hole, h1, relative to the total head loss, H, is independent of loading conditions and constant for any particular hole shape (B/L), area (B∙L), and relative depth (L/T). A semi-empirical general solution is developed for a rectangle within the range of 0 ≤ B/L ≤ 1 with the solution converging to that for a strip for B/L→ 0 and to a circle for B/L→ 1. The solution gives calculated leakage in encouraging agreement with the experimental data.

Predictive modeling of microhole profile drilled using a focused electron beam with backing materials

This study establishes a simple and rapid predictive model for a microhole profile drilled using a focused electron beam based on the finite difference method. Vertical irradiation and full penetration using a focused beam with a Gaussian distribution were reflected onto the three-dimensional mesh of metallic substrates. The predictive hole profiles on the substrate were estimated by analyzing the phase transition using predictive temperature distributions. To validate the predictive accuracy of model, experimental drilling processes on AISI 304 stainless steel substrates were conducted, and the experimental hole qualities were measured using microcomputed tomography. Comparisons between predictive and experimental results represented high predictive accuracy in three criteria: hole diameters, straightness, and geometrical hole shape. Applying the fractional energy absorptance dependent on the substrate depth significantly improved the prediction accuracy of model. The predictive results demonstrated that the thermal analysis with temperature distributions could predict the drilled hole qualities rapidly and accurately, avoiding the high computational loads from considerations for velocity fields or pressure distributions around the substrate.

Abrasive water jet piercing of straight and inclined holes on Yttria-Stabilized Zirconia coated Ni-based superalloy

ABSTRACT The present work investigates the Abrasive Water Jet (AWJ) drilled holes with different hole angles such as 0°, 15°, 30°, and 45° on Yttria-Stabilized Zirconia (YSZ)-coated nickel-based superalloy using a piercing mode of operation. These types of holes were used as film cooling holes for the aero engine modules. The water jet pressure, hole piercing angle, and garnet flow rate were taken as variable operational parameters. The effect of these factors on hole features, such as entry and exit hole diameters, taper angle and coating removal rate, was analyzed. The machining time and surface roughness were also investigated. The results indicated the water jet pressure and hole piercing angle having significant effects on the hole geometrical features. Lower water jet pressure produced the exit hole cap, hairline burrs on the exit hole, and surface chipping. However, these defects were not found with an increment in the water jet pressure. Besides, circular and oval shape hole profiles were observed at different hole angles for film cooling applications. The AWJ pierced hole was seen having free of cracks, delamination, and other material defects. However, removal of excess YSZ coating was noticed near the hole by lateral erosion. This could be significantly reduced by optimizing the operational parameters for making quality holes on the ceramic-coated nickel-based superalloys.

Seismic behavior of steel space truss connections to reinforced concrete supporting columns

Roof joint is a critical connection in space truss structures, which connects the upper steel space truss roofs and reinforced concrete structures. Because of its simple structural detailing and easy construction, a typical kind of roof joint is comprised of four embedded anchor rods, a mortar layer, a base plate, and stiffeners are popular in small- to medium-span space truss structures. Among them, base plates with slotted bolt holes are commonly used to release the deformation caused by temperature change or earthquake input. The roof joints were considered either as pinned or rigid connections in the design. In this paper, quasi-static tests investigating the influence of the applied axial force and the shape of bolt holes on the shear resistance and seismic behavior of roof joints were performed. The roof joints exhibited semi-rigid connection behavior and two types of initial resistance mechanisms, sliding and overturning, were observed. With the increase of applied axial force, the behavior of roof joint changes from sliding to overturning. Finally, effective methods to determine the initial resistance mechanism and calculate the ultimate shear strength of roof joints are proposed. These findings and analyses may provide guidelines for roof joint design practice for space truss structures.

Effects on Film Cooling Performance in the Showerhead From Geometric Parameterization of Shaped Hole Designs

Abstract The high heat loads at the leading-edge regions of turbine vanes and blades necessitate the most robust thermal protection, typically accomplished via a dense array of film cooling holes, nicknamed the “showerhead.” Although research has shown that film cooling using shaped holes provides more reliable thermal protection than that using cylindrical holes, the effects on cooling performance from varying the geometric details of the shaped hole design are not well characterized. In this study, adiabatic effectiveness and off-the-wall thermal field measurements were conducted for two shaped hole geometries designed as successors to a baseline hole geometry presented in a previous study. One geometry with a 40% increase in area ratio exhibited only a marginal improvement in adiabatic effectiveness (∼10%). A second design with a 12 deg forward and lateral expansion angle with a breakout area 40% larger performed marginally worse than its matched area ratio counterpart (∼15% lower), suggesting a negative sensitivity to breakout area. Such changes in performance for different shaped hole designs were small compared to the boost in performance gained by switching from a cylindrical hole to a shaped hole, which suggests cooling performance is insensitive to specific shaped hole details provided the exterior coolant flow is well-attached.

Intake grille design for an embedded ventilation-and-cooling system in an aircraft

An inlet grille typically needs to be installed at the inlet of the air intake of the ventilation-and-cooling system embedded in airborne electronic equipment to improve pneumatic stealth performance. Here, a typical flying wing model is used as a case study, and a computational fluid dynamics (CFD) simulation is performed. The flow resistance characteristics of the air intake of the opening of the ventilation-and-cooling system on a flat fuselage surface with and without an inlet grille are analyzed at different flow rates and Mach 0.25. The effects of the grille opening shape, diversion angle, thickness, aperture size, and hole shape on the flow resistance characteristics are investigated in detail. The grille is found to effectively guide airflow entry: although the flow resistance at the inlet is increased, the flow resistance at the inlet and outlet of the air intake is significantly reduced. The optimal developments of the outflow and flow resistance characteristics are obtained for a quadrilateral opening. The smaller the diversion angle is, the smoother the airflow entry, and the higher the quality of the internal airflow. The rectification, viscous resistance, and weight exhibit opposing trends with increasing thickness and must be comprehensively considered in designing an optimal scheme. A large-aperture grille ensures good flow patency at low flow rates, whereas a small-aperture grille can reduce flow perturbations and separation at high flow rates by smoothly guiding air into the intake. A grille with round holes has a better spanwise and chordwise balancing effect on the airflow and better flow resistance characteristics than a grille with diamond-shaped holes.

Optimization of the outlet unloading structure to prevent gaseous cavitation in a high-pressure axial piston pump

Raising the pressure rank of axial piston pumps is an effective way to enhance the power density. However, when hydraulic fluid switches between the suction and discharge areas in the valve plate at a high level of pressure, the effective delivery flow rates of pumps decrease and may cause vibrations, noise and gaseous cavitation. Increasing the inlet pressure is a common method used to reduce gaseous cavitation; however, this requires additional equipment to pressurize the inlet line, which reduces the power density of the pump. This study proposed a new approach to reduce gaseous cavitation by modifying the shape of the unloading holes for pumps. A computational fluid dynamics (CFD) model was established to examine the influences of the unloading holes of the valve plate on gaseous cavitation. The simulation results revealed that a crescent-shaped unloading hole in the valve plate can effectively decrease the gaseous cavitation by redistributing the damage power of cavitation. Moreover, the crescent-shaped design of the unloading hole can increase the unloading rate by 64.39% at an inlet pressure of 1.1 MPa and rotational speed of 1600 r/min compared to that of traditional unloading holes. As a result, cavitation in the pump can be reduced effectively by an improved unloading rate, which has great practical significance for suppressing the cavitation phenomenon and decreasing vibration and noise in the pump.

SCHWARZSCHILD SPHERE AND NASTASENKO SPINNERET

The study of black holes deepens the understanding of the structure of the foundations of the material world and the Universe, which is an urgent and important task that has not yet been fully resolved. Its solution is the main goal of this work, and the substantiation of the shape and structure of black holes on the basis of strict laws of nature is its scientific novelty. The research methods used in the work are based on deduction and induction, on the application of reliable laws of physics and the general principles of the theory of knowledge. Other methods are partially taken into account, because this work is related to scientific discoveries, the search for which is difficult to formalize. Results and its discussion. The paper puts forward a hypothesis that at the quantum level of the material world, the Schwarzschild sphere should be replaced by a spinneret of two layers of hexagonal prisms of circular space quanta, which are formed by six regular trihedral prisms of elementary space quanta with face length λG = 4.05126×10-35 m, of equal to the length waves of the gravitational field that forms them. Conclusions. It is shown that the spinnerets radius R = λG and its mass change by quantum jumps, and its internal structure consists of cylindrical layers, the radius of which increases from the first axial cylinder to the peripheral one by the quantum value λG. The spinnerets can have the properties of a black and white hole, which corresponds to the principles of Einstein's GR.

Evolution of mesh-like liquid films in multi-port lifted Hele Shaw cells

Multi-port Lifted Hele-Shaw Cells (MLHSCs) can be used to efficiently generate liquid films with regular mesh-like patterns, which in turn may be used as templates for micro-fabrication of mesh-like structures. This work systematically characterizes the spatio-temporal evolution of Newtonian liquid films in MLHSCs using experiments and numerical simulations. The interior holes of the mesh tend to assume circular shapes for low Capillary number, while they approach a square-like shape at high Capillary number. Fingering instability is observed at high Capillary numbers and higher inter-hole spacing. Capillary number can also significantly affect the shape of peripheral and corner holes in the mesh. Numerical simulations, based on front tracking method, are used to characterize the stability of interfaces in a periodic hole array. Data from numerical simulations is used to construct and validate a computationally efficient low-order model for predicting the evolution of mesh-like patterns formed in the film.

3D Interdigital Electrodes Dielectric Capacitor Array for Energy Storage Based on Through Glass Vias

AbstractDielectric capacitors are ideal for high power pulse system due to their high‐power density. However, the traditional dielectric capacitor cannot achieve large capacitance density and combine with the high breakdown voltage. Through this research, the internal structure of photosensitive glass can be transformed into multilayer interdigital electrodes structure through photolithography and laser induced processes. It is realized through the transition from the 2D structure to the 3D interdigital electrodes dielectric capacitor. In this case, the specific surface area electrode structure presents exponential increase and dielectric layers thickness decrease, which provide a large capacitance density. The new 3D capacitors, via reducing the roughness of the electrode surface, a uniform porous inner wall improves the breakdown strength (8.15 MV cm−1, which is 2 times to photolithographic). As a result, these highly‐density regular electrodes array effectively improve the capacitance density to 48.5 nF cm−2, which is 422 times larger than that of planar structure. Moreover, the new 3D capacitors fabricated by laser‐induce exhibit smoother inner wall surface and more rounded shape of electrode holes, achieving very large energy storage density of ≈3.4 Wh kg−1 (14.688 J cm−3) and power density of ≈6.48 × 1011 W kg−1.

Experimental Research and Multi-Physical Field Coupling Simulation of Electrochemical Machining Based on Gas-Liquid Two-Phase Flow.

In this paper, the forming mechanism of cooling hole electrolytic machining is studied using multi-physical field coupled simulation and experimental observation. A multi-physical field coupled simulation model was established to obtain the gas–liquid two-phase distribution law inside the machining gap, and a mathematical model of gas–liquid two-phase flow was established to analyze the change law of the size and morphology of cooling hole electrolytic machining under different process parameter conditions. The simulation and experimental results show that the size of the inlet of the cooling hole is larger, the size of the outlet is smaller, and the middle section is more stable; machining voltage and electrode feed speed have a significant influence on the size and shape of heat dissipation holes. Compared with the experimental data, simulation accuracy is good.

Brake-Disc Holes and Slit Shape Design to Improve Heat Dissipation Performance and Structural Stability

A brake disc decelerates the vehicle through friction with the brake pads. When the brake system is overheated, brake fade can occur, in which the friction coefficient drops significantly. Additionally, an over-heated brake system may cause vapor lock, in which the brake hydraulic fluid is vaporized. These phenomena can lead to the loss of braking power and cause a fatal accident. Therefore, brake systems must have stable braking and heat dissipation performance. Having through-holes and slits on the friction surface of the rotor has been adopted to improve the heat dissipation performance, but the holes become stress points and potentially cause cracks. Therefore, brake systems should be designed to have structural stability as well as good heat dissipation. In this study, finite element (FE) modeling was developed to analyze the structural stability and heat dissipation performance of a brake system, and structural and thermal simulations were performed in ANSYS, a CAE software package. In addition, to minimize concentrated stress and temperature, optimal design of the shape and pattern of holes and slits was carried out using PIAnO, an integrated optimal design software package. The first step of design optimization was performed while considering the shape and pattern of the disc holes and slits as design factors. Among the design factors, those with the largest effects on the objective functions were found and set as new design factors to perform the second step. The designs were compared to existing discs. Through the optimization presented in this paper, it is expected that the performance of the braking system will improve and the life of the brake parts will be increased.

Different micro/nano-scale patterns of surface materials influence osteoclastogenesis and actin structure

The surface topography of a material can influence osteoclast activity. However, the surface structural factors that promote osteoclast activity have not yet been investigated in detail. Therefore, we investigated osteoclastogenesis by testing various defined patterns with different dimensions and shapes. The systematic patterns, made of a cyclo-olefin polymer, were prepared at a micron-, submicron-, and nano-scale with a groove, hole, or pillar shape with a 1:1 pitch ratio. RAW264.7 cells were cultured on these patterns in the presence of the receptor activator of NF-κB ligand (RANKL). Osteoclast formation was induced in the order: pillar > groove ≥ hole. The two-dimensional factors also indicated that submicron-sized patterns strongly induced osteoclast formation. The optimal pillar dimension for osteoclast formation was 500 nm in diameter and 2 µm in height. Furthermore, we observed two types of characteristic actin structure, i.e., belt-like structures with small hollow circles and isolated ring-like structures, which formed on or around the pillars depending on size and height. Furthermore, resorption pits were observed mainly on the top of calcium phosphate-coated pillars. Thus, osteoclasts prefer convex shapes, such as pillars for differentiation and resorption. Our results indicate that osteoclastogenesis can be controlled by designing surfaces with specific morphologies.

Experimental studies of bubble dynamics under a broken horizontal plate

This paper presents an experimental study on the pulsation characteristics of bubbles under a damaged boundary. Bubble phenomena in the fluid domain, such as bubble shape, pulsation period, water jet, and motion, are observed, and the influence of distance parameters on these phenomena is analyzed in detail with the help of high-speed photography technology. We also discuss the relationship between bubble pulsation, the water spike form, and characteristic parameters under different boundary conditions, such as different hole shapes. It is found that the broken boundary weakens the effect of the wall on bubble motion, while the shape and area of the hole exert noticeable effects on the water spike. In addition, the rising part of the free surface consisting of three parts, the water spike, water skirt I, and water skirt II, along with their evolutionary forms at the gas–liquid interface, are experimentally studied.

Effect of laser plasma on Nd:YAG laser drilling of acrylic plate with high optical density

Laser material processing (LMP) is used to replace traditional material processing techniques, such as material cutting, thin plate drilling, and surface processing. When a high-energy laser is projected onto a material, the temperature of the material increases rapidly, changing the characteristics of the material and making the material on the surface vaporize and peel off instantly. In this study, we developed a laser system using a Quantel Brilliant neodymium-doped yttrium aluminum garnet (Nd:YAG) with a wavelength of 1064 nm laser a pulse width of 5–6 ns, a beam diameter of the 6 mm, and 10 repetition rate (Hz) on the energy stability is within 5.60%, an F-theta lens is used to obtain a focused laser beam with a diameter of 0.2 mm. The developed system was employed to drill holes in a 3-mm-thick optical-grade acrylic polymethyl methacrylate (PMMA) plate with high optical density and 7 + safe windows. A laser-safe, flat-window, visible-light-transmitting (VLT) sample was used, and the material to be drilled was a PMMA plate. The laser beam must be focused on the center of the F-theta lens and must be aligned with the distance between the F-theta lens and the linear stage. The working distance was set to 300 mm. Furthermore, the diameter was adjusted to obtain the laser plasma effect; that is, the working distance was fixed. First, the characteristics of the laser plasma and the ability of the laser to penetrate optical-grade acrylic (PMMA) plates samples were studied. By changing the lifting position of the vertical axis and varying the working distance of the acrylic (PMMA) plates, the laser beam was targeted at different positions on the acrylic (PMMA) plates. To determine the optimal parameters for the drilling process, a pulsed laser output of 174.7 mJ/pulse (3000 pulses in 5 min) was focused on the hole. Results showed that the energy was 522.98 J/cm2; a laser energy density of 141.26–275.93 J/cm2 resulted in an acceptable heat-affected zone. The Nd:YAG pulsed laser can produce laser plasma that can increase the hole diameter by up to 50% because of the produced cavity gap. Various exit and entrance hole shapes can be achieved and thus employed for different applications, such as laser beam cutting.