Trapezoidal Cross-section Research Articles

Steady RANS of Flow and Heat Transfer in a Smooth and Pin-Finned U-Duct With a Trapezoidal Cross Section

Steady Reynolds-averaged Navier--Stokes (RANS) simulations were performed to examine the ability of four turbulence models—realizable k–ε (k–ε), shear-stress transport (SST), Reynolds stress model with linear pressure strain (RSM-LPS), and stress-omega RSM (RSM-τω)—to predict the turbulent flow and heat transfer in a trapezoidal U-duct with and without a staggered array of pin fins. Results generated for the heat-transfer coefficient (HTC) were compared with experimental measurements. For the smooth U-duct, the maximum relative error in the averaged HTC in the up-leg is 2.5% for k–ε, SST, and RSM-τω and 9% for RSM-LPS. In the turn region, the maximum is 50% for k–ε and RSM-LPS, 14.5% for RSM-τω, and 29% for SST. In the down-leg, SST gave the best predictions and RSM-τω being a close second with maximum relative error less than 10%. The ability to predict the separated flow downstream of the turn dominated the performance of the models. For the U-duct with pin fins, SST and RSM-τω predicted the best, and k–ε predicted the least accurate HTCs. For k–ε, the maximum relative error is about 25%, whereas it is 15% for the SST and RSM-τω, and they occur in the turn. In the turn region, the staggered array of pin fins was found to behave like guide vanes in turning the flow. The pin fins also reduced the size of the separated region just after the turn.

Airside Performance of H-Type Finned Tube Banks with Surface Modifications

The present study numerically investigates some novel modifications to augment the performance of the H-type finned tube banks, which are widely used in waste heat recovery in industries. The imposed modifications upon the original H-type finned tube banks include the following: (1) Design 1 contains some triangular cuts at the edge of the original rectangular fin; (2) Design 2 modifies the original rectangular geometry into a trapezoid shape; (3) Design 3 renders the original rectangular cross-section fin thickness into trapezoid cross-section; and (4) Design 4 changes the original rectangular shape into a circular shape. Based on the simulations, it is found that Design 1 shows barely any improvements in the heat transfer performance and surface area reduction. Design 2 can provide some weight saving and surface area reduction at a slightly inferior heat transfer performance. Design 3 can offer up to 14% improvements in the overall heat transfer performance without any pumping power penalty. Yet, Design 4 provides the maximum weight saving as compared to the original reference case. With 3–9% lesser surface area than the reference case, Design 4 still offers marginally higher heat transfer performance.

Application of SMA spring tendons for improved grasping performance

Shape memory alloy (SMA)-based soft actuators and grippers have generally used SMA wires due to design restrictions, limited actuation force and poor cooling performance of SMA springs. This work demonstrates that SMA springs can be used for high performance soft actuation by positioning them externally as a tendon with the force transmitted to the polymeric matrix using a tendon. Through improvements by using active cooling through fans, a spring longer than the matrix and a matrix with a trapezoidal cross-section, the actuator was capable of cyclic actuation at 0.25 Hz, a bending angle of 270° and a tip force of 0.21 N. The same actuator design was used to build a soft robotic gripper capable of grasping objects with a wide range of shapes and weights, and its maximum pull-off force was measured to be 30 N. The gripper was also capable of holding a weight of 2 kg. The increased design freedom of the proposed design would also enable further improvements to the bending and grasping performance of the actuator, and the use of SMA-based soft actuation to more complex designs and a wider range of robotic applications.

Time-dependent creep analysis of a functionally graded beam with trapezoidal cross section using first-order shear deformation theory

Time-dependent creep analysis of a rotating functionally graded cantilever beam with trapezoidal longitudinal cross section subjected to thermal and inertia loading is investigated using first-order shear deformation theory (FSDT). The model described in this paper is a simple simulation of a turbine blade working under creep condition. The material is a metal based composite reinforced by a ceramic where the creep properties of which has been described by the Sherby\' s constitutive model. All mechanical and thermal properties except Poisson\'s ratio are assumed to be variable longitudinally based on the volume fraction of constituent. The principle of virtual work as well as first order shear deformation theory is used to derive governing equations. Longitudinal distribution of displacements and stresses are investigated for various volume fractions of reinforcement. Method of successive elastic solution is employed to obtain history of stresses and creep deformations. It is found that stresses and displacements approach their steady state values after 40000 hours. The results presented in this paper can be used for selection of appropriate longitudinal distribution of reinforcement to achieve the desired stresses and displacements.

A Trapezoidal Cross-Section Stacked Gate FinFET with Gate Extension for Improved Gate Control

An improved trapezoidal pile gate bulk FinFET device is implemented with an extension in the gate for enhancing the performance. The novelty in the design is trapezoidal cross-section FinFET with stacked metal gate along with extension on both sides. Such improved device structure with additional process cost exhibits significant enhancement in the performance metrics specially in terms of leakage current behavior. The simulation study proves the suitability of the device for low power applications with improved on/off current ratio, subthreshold swing (SS), drain induced barrier lowering (DIBL), Gate Induced Drain Leakage (GIDL) uniform distribution of electron charge density along the channel and effects of Augur recombination within the channel.

Sheath-less high throughput inertial separation of small microparticles in spiral microchannels with trapezoidal cross-section.

Various mechanisms of different designs have emerged for the purpose of microparticle separation and cell sorting. The main goals behind such designs are to create high throughput and high purity sample isolation. In this study, high efficiency, high throughput and precise separation of microparticles under inertial lift and drag forces induced by trapezoidal curvilinear channels are reported. This work is the first to focus and recover 2 from 5 μm and 2 from 10 μm particles in spiral channels in a sheath-less flow device, which reduces the overall complexity of the system and allows for higher throughput. The new microfluidic chip design is fabricated in glass using femtosecond laser ablation. In addition, mathematical force calculations were conducted during the design phase of the microfluidic channels and compared with experiments. The results show a close prediction of the equilibrium position of the tested microparticles.

TEMUAN TERAKOTA DARI SITUS BOJONG GANDU, KERTABUMI, CIAMIS: SEBUAH TELAAH BENTUK DAN RAGAM HIAS 1

In a study that conducted in the Kertabumi area, terracotta artifacts were found with unique shapes and decorations. The terracottas were found in a considerable amount. There are numerous variations in the shape and decoration of these findings. Locals refer to these artifacts as “kue”. The purpose of this paper is to classify these findings based on the shapes and decorative motifs. According to the grouping that has been done it is known that there are 4 groups based on the cross section; there are rectangular, semicircular, elliptical and trapezoidal cross sections. Meanwhile the decoration on terracotta is in the form of lines, woven bamboo patterns, and circles. These decorations can appear together in one terracotta, while another terracotta only have one decoration.

Numerical Analysis on Hydraulic Characteristics of U-shaped Channel of Various Trapezoidal Cross-Sections

Curved channel with trapezoidal cross-section is approximate to the common form in nature fluvial networks and its hydraulic characteristics are considerably complex and variable. Combined with volume of fluid (VOF) method, renormalization group (RNG) k-ε turbulence model was employed to numerically investigate the flow properties in the U-shaped channel with various trapezoidal cross-sections. Analyses were performed from the aspects of the water surface transverse slope in bend apex (WTS-BA), longitudinal velocity, secondary flow, shear stress and turbulent kinetic energy (TKE) under several scenarios, specifically, four types of radius-to-width ratio and seven types of slope coefficient with a constant aspect ratio. The calculated results suggested that the maximums of shear stress and TKE in the bend were observed in the convex bank and the maximal intensities of secondary flow were observed within the range of 60 to 75 degrees for various varieties. As the radius-to-width ratio increased, the maximums of shear stress, TKE and WTS-BA decreased; but increased with increasing slope coefficients. The intensity of secondary flow decreased as slope coefficients increased and the angle of maximum intensity of secondary flow moved to the upstream for the increasing radius-to-width ratios. In addition, a new equation concerning the vertical distribution of longitudinal velocity in trapezoidal cross-sectioned channel was presented.

Cladding stress induced performance variation of silicon MMI coupler

In this paper, we have shown the effect of stress induced by cladding layer on the performance of silicon MMI coupler. The cladding material is assumed to be SiO2. From the numerical analysis using finite element method (FEM), we have demonstrated that the length of the MMI coupler for a given power splitting ratio is a strong function of stress. Moreover, with temperature the power splitting ratio changes as high as 50% for a MMI coupler having cladding induced stress, compared to a MMI coupler without having cladding induced stress. In this study, two cross-sectional geometries, namely rectangular and trapezoidal are considered to investigate the effect of waveguide cross section on the cladding induced stress. Here, the SiO2 cladding thickness is also varied from 400 nm to 800 nm for both types of geometries. It is found that out-of-plane stress increases with cladding thickness for both waveguide cross-sections and the opposite nature of variation is found for in-plane stress. Trapezoidal waveguide introduces higher in-plane as well as out-of-plane stress compared to rectangular waveguide for any given cladding thickness. Further, the temperature sensitivity of MMI coupler without and with stress having two different power splitting ratios and waveguide cross-sections are studied. The stress induced birefringence is also calculated for the fundamental mode (MMI under consideration supports 16 modes in total) as a function of cladding thickness and operating temperature. The results show that like previously studied waveguide structure, in MMI coupler also the birefringence increases with increased cladding thickness, whereas it decreases with the operating temperature. It is also observed that the stress induced birefringence is more for trapezoidal waveguide cross-section compared to rectangular cross-section. Simulation results reveal that the effective thermo-optic coefficient for a given mode supported by the MMI coupler is independent of cladding thickness, waveguide geometry and stress.

Effects of trapezoidal cross-section dimensions on the behaviours of CFRP SCC beams

This study investigates the behaviour of trapezoidal cross-sections self-compacting reinforced concrete beams under flexural failure, with and without strengthening with carbon fibre reinforced polymer CFRP. The studied beams were divided into two groups according to their cross-sections; each group included five beams, and the first group (T20) were those with trapezoidal cross-sections with dimensions length 1,600 × height 260 × width of 160 mm at the bottom and 200 mm at the top, while second group (T24) consisted of those with trapezoidal cross-sections with dimensions length 1,600 × height 260 × width of 160 mm at the bottom and 240 mm at the top. The experimental programme included studying the effects of top width on the flexural behaviour of beams with trapezoidal cross-sections, in addition to studying the effect of reinforcing those beams with varying numbers, locations, and methods of placement of CFRP strips. The experimental results showed that trapezoidal cross-sections with 240 mm top width gave higher ultimate load capacity by 4 to 11.54%, as well as offering lower deflection, compared to trapezoidal cross-sections with 200 mm top width. In addition, strengthening beams with CFRP strips leads to an increase in the ultimate load capacity by 4 to 24% in trapezoidal cross-section beams, reducing their deflection and delaying the appearance of the first crack in the concrete. It was found that applying CFRP strips to the maximum moment region increased the ultimate load capacity by an average of 4.17 to 7.7 % in comparison to beams strengthened with strips applied along the beam

DESIGN OF STILLING BASIN FOR DECREASING BACK WATER IN THE DAM FOOT

This research studies the hydraulic behavior and the problem solving alternatives of original until final design, and the most effective stilling basin and downstream regulator channel for decreasing back water from the upstream water level in the dam foot. The methodology consists of physical modeling in theLaboratory of River and Swamp, Department of Water Resources, Faculty of Engineering, University of Brawijaya. The methods include the USBR for the hydraulic analysis, the Hind’s formulation for the side channel analysis, the energy equation by analyzing the standard step for the transition and the chute way analysis, and the USBR type III for designing the stilling basin. A square cross-section with the Manning coefficient of 0.40 is used for determining the control of the Tail Water Level (TWL) and a trapezoidal crosssection with the Manning coefficient of 0.39 is used for the final design. However, the equation of Schotlischand Veronise is used for the local scouring analysis. The result of Model Test and analysis indicates that there are some differences among the analysis in every point of the building. Therefore, the relative error is needed to know how big the error in the comparison result.This research studies the hydraulic behavior and the problem solving alternatives of original until final design, and the most effective stilling basin and downstream regulator channel for decreasing back water from the upstream water level in the dam foot. The methodology consists of physical modeling in theLaboratory of River and Swamp, Department of Water Resources, Faculty of Engineering, University of Brawijaya. The methods include the USBR for the hydraulic analysis, the Hind’s formulation for the side channel analysis, the energy equation by analyzing the standard step for the transition and the chute way analysis, and the USBR type III for designing the stilling basin. A square cross-section with the Manning coefficient of 0.40 is used for determining the control of the Tail Water Level (TWL) and a trapezoidal crosssection with the Manning coefficient of 0.39 is used for the final design. However, the equation of Schotlischand Veronise is used for the local scouring analysis. The result of Model Test and analysis indicates that there are some differences among the analysis in every point of the building. Therefore, the relative error is needed to know how big the error in the comparison result.

Stacked Gate FinFET with Gate Extension for Improved Gate Control

Referring to the experimental data available, a modified pile gate bulk FinFET device with trapezoidal cross-section is analyzed through this paper. Two special features of Pile gate FinFET are trapezoidal cross-section and extended gate. The comprehensive performance metrics analysis justifies its improved performanceas compared to normal bulk FinFET. The device design analysis is also carried out for varying fin height, length of extension of the gate structure and bottom gate material work function. Thermal reliability is justified through analyzing electrical propertied for varying temperatures. The performance metrics considered for the analysis include threshold voltage, transconductance Subthreshold Slope, Drain Induced Barrier Lowering and Gate Induced Drain Leakage current.

The Effect of the Fin Shape and Thickness of the Buried Oxide on the DIBL Effect in an SOI FinFET

In this paper, we simulated the dependence of the effect of reducing the drain-induced barrier lowering on the thickness of a buried oxide layer in a finned (vertical) metal-oxide-semiconductor field effect transistor (FinFET) based on silicon-on-insulator technology. Three shapes of the fin with the rectangle, trapezoid, and triangle cross sections were considered. The drain-induced barrier lowering effect significantly depends on both the fin shape and the thickness of the buried oxide layer. The smallest drain-induced barrier lowering effect occurs when the thickness of the buried oxide layer is small for the fin of a triangular shape. This behavior of the drain-induced barrier lowering effect is strongly correlated with the behavior of the parasitic capacitance between a gate and a source.

Relative study of steel solar pond with sodium chloride and pebbles

The salt-gradient solar pond is the pre-eminent solar desalination process for storing thermal energy. Due to the high concentration of salt content present in the lower convective zone heat will be stored for a longer period and will supply thermal energy at whatever time is required to have a temperature varying from 50 °C to 90 °C. This paper proposes an experimental and theoretical analysis of the convective type solar pond with trapezoid cross sections with the surface area of 1.7 m2 and depth of 0.5 m made-up of 2 mm thickness mild steel sheet-metal lined by 20 mm and 2 mm thickness of thermo styrene, high density polyethylene sheet. The salinity-gradient is having three zones and these zones are separated due to salt concentration, each zone is having a varying thickness of 1.5 m (upper zone), 2 m (middle zone) and 1 m (lower zone). K-type thermocouple and solar power meter is used to measure the variation of temperature and solar radiation of the pond, thermocouples were space equally of 5 cm at six intervals and the readings were taken for eight hours per day and it is recorded during the months of December and January for further analysis. Experiments are conducted to find efficiency with NaCl and Pebbles. The experimental result reveals that efficiency is higher in NaCl (7%) compared with Pebbles (4%).

Polarization independent metallic-dielectric trapezoidal grating for multiband absorption in the visible

We propose and analyze in details a selective multiband absorber with polarization-independent behavior based on a metal/dielectric periodic grating with trapezoidal cross section operating for visible light frequencies. The absorption near unity for independently polarized waves is observed for a normal incidence in all absorption peaks. The physical mechanisms of the narrowband selective absorber are investigated and explained by the spatial distribution of the electromagnetic fields of the structure for each resonant peak. The behavior of the structure for obliquous incidence is also analyzed and the structure maintained high absorption for both modes of polarization for incident angles of up to 10°. The dependence of the absorber is also analyzed by sweeping the optical and geometrical parameters of the grating.

Graphical-and-Analytical Method for Designing Reinforced-Concrete Scroll Casings of Water Turbines Based on Laws of Variation in Cross-Section Average Tangential Velocities

A new graphical-and-analytical method for design of reinforced-concrete scroll casings with trapezoidal cross-sections of water turbines is proposed. This method generalizes the methods currently used to determine the trapezoidal cross-section dimensions of scroll casings, given the dimensions of their inlet cross-section. This method allows considering different laws of variation in the cross-section average tangential velocity along the scroll length: the velocity can increase, be constant, decrease, or vary differently within different sections of the scroll. The necessary formulas are derived by an analytical method. The design procedure is described by way of examples.

Inertial-Based Filtration Method for Removal of Microcarriers from Mesenchymal Stem Cell Suspensions

Rapidly evolving cell-based therapies towards clinical trials demand alternative approaches for efficient expansion of adherent cell types such as human mesenchymal stem cells (hMSCs). Using microcarriers (100–300 µm) in a stirred tank bioreactor offers considerably enhanced surface to volume ratio of culture environment. However, downstream purification of the harvested cell product needs to be addressed carefully due to distinctive features and fragility of these cell products. This work demonstrates a novel alternative approach which utilizes inertial focusing to separate microcarriers (MCs) from the final cell suspension. First, we systematically investigated MC focusing dynamics inside scaled-up curved channels with trapezoidal and rectangular cross-sections. A trapezoidal spiral channel with ultra-low-slope (Tan(α) = 0.0375) was found to contribute to strong MC focusing (~300 < Re < ~400) while managing high MC volume fractions up to ~1.68%. Accordingly, the high-throughput trapezoidal spiral channel successfully separated MCs from hMSC suspension with total cell yield~94% (after two passes) at a high volumetric flow rate of ~30 mL/min (Re~326.5).

Performance investigation of micro-pocketed textured pad thrust bearing

PurposeThe purpose of this paper is to conceive a new surface texture incorporating a tiny shape among the micro-pockets (with circular, rectangular, trapezoidal and triangular cross-sections) and dimples (cylindrical, hemispherical and ellipsoidal) for exploring to enhance the maximum possible performance behaviors of sector shape pad thrust bearing.Design/methodology/approachNumerical simulation of hydrodynamically lubricated sector shape textured pad thrust bearing has been presented incorporating thermal and cavitation effects. The coupled solution of governing equations (Reynolds equation, film thickness expression, viscosity–temperature relation, energy equation and Laplace equation) has been achieved using finite difference method and Gauss–Seidel iterative scheme.FindingsWith new textured pads, higher load-carrying capacity and lower coefficient of friction are obtained in comparison to plain sector shape pad. Texture pattern comprising square cross-sectional pockets yields higher load-carrying capacity and lower coefficient of friction in comparison to other cross-sectional shapes (circular, trapezoidal and triangular) of pockets considered herein.Originality/valueThis study reports a new texture, which involves micro-pockets of square cross-sectional shapes to improve the performance behavior of sector shape pad thrust bearing. About 75 per cent increase in load carrying capacity and 42 per cent reduction in coefficient of friction have been achieved with pad having new texture in comparison to conventional pad.

Effects of surface migration on InGaN/GaN multiple quantum wells selectively grown on periodic stripe openings separated by large SiO2 covered spacing on Si (111) substrates

InGaN/GaN multiple quantum wells (MQWs) were selectively grown on patterned GaN/AlN/Si (111) templates with periodic stripe openings separated by large SiO2 covered spacing. In comparison with the conventional epitaxial lateral overgrowth, the migration behaviours of group-III adatoms on the large mask region has a distinct effect on the structural and optical properties of InGaN/GaN MQWs selectively grown on the narrow stripe openings. In order to control them, a wide stripe window nearby the narrow one was adopted to modulate the local growth environments in our experiment. Flat and faceted InGaN/GaN MQWs stripes with trapezoidal cross section composed of basal (0001) plane and two semipolar {112̅2} facets were obtained. The optical properties were investigated by the microscopic photoluminescence (micro-PL) measurement. The difference in emission peak positions observed by scanning the excitation laser across the stripes is related to the surface migration behaviour of the group-III adatoms on the SiO2 masks.

Analytical Dispersion Theory for Optical Waves in Regular Microwaveguides

A method for analysis of dispersion characteristics of guided optical modes propagating in the optical waveguides with small cross-sections is proposed. The method is based on introduction of a correction factor for a longitudinal wavenumber of propagating modes. The correction factor arises when a cross-section of the basic rectangular waveguide is subjected to perturbation. The electromagnetic field distributions along with the mode longitudinal wavenumber are found by means of variable separation method. The longitudinal wavenumber correction factor is analytically calculated in terms of coupled mode theory. The combined use of the complete set of equations of electrodynamics together with the concept of effective sources gives rise to the correction factor in the form of an intermodal coupling coefficient. It is pointed out that the coupling coefficient consists of two components, namely bulk and surface, owing to accurate account of the electrodynamics boundary conditions. Using the method proposed, the dispersion characteristics of the fundamental modes propagating in the practically employed optical waveguides having a trapezoidal cross-section are calculated. An impact of the waveguide cross-section shape to cladding dielectric constant ratio on the mode dispersion characteristics is analyzed. The necessity to take into consideration an imperfection of the waveguide cross-section in a wide range of operating wavelengths is demonstrated.