Trapezoidal Angle Research Articles

A rapid time-coordinated longitudinal guidance method for high-speed vehicle

Compared to the traditional method of adjusting flight time by increasing lateral maneuverability [1-2], a faster time-coordinated longitudinal guidance method for unpowered high-speed vehicles has been proposed in this paper. Firstly, the centroid dynamics model and flight constraint model of unpowered high-speed vehicles were established, and the angle of attack corridor was derived based on quasi-equilibrium gliding conditions (QEGC). Then, to plan a reasonable angle of attack profile, the flight capability of a single vehicle under different constant angles of attack is analyzed, including terminal altitude, terminal velocity, and terminal arrival time. Furthermore, to achieve a long-term high angle of attack flight, a rapid time-coordinated longitudinal guidance method based on a trapezoidal angle of attack profile was proposed. Finally, using the vehicle and its performance parameters from Chapter 3 [3], numerical simulations were conducted under nominal tasks and multi-vehicle collaborative tasks. The simulation results show that under different expected arrival times, this method can quickly plan the angle of attack profile that satisfies time constraints, with high computational efficiency. Moreover, the arrival time adjustment ability of this method is large, which can fully utilize the arrival time capability of the high-speed vehicle. The above research provides more convenient conditions for a collaborative flight of multiple vehicles.

Melting process investigation of a non-Newtonian phase change material containing multiwalled carbon nanotubes in a trapezoidal enclosure

This research examines the melting characteristics of nano-enhanced, non-Newtonian PCMs-multi-walled carbon nanotube (MWCNT). The process includes analyzing the impacts of various nanoparticle concentrations and trapezoidal angles by conducting simulations with these nanocomposites filled within the enclosure. The power-law shear-thinning effects are incorporated into the governing equations, which are then converted into a generalized dimensionless form using scaled parameters and solved using the finite element method. The findings underscore the significant role of enclosure geometry in influencing the melting dynamics and heat transfer process. Critical outcomes include the effect of nanoparticle concentration on the initiation of natural convection and the overall melting process, the influence of trapezoidal angle on the distribution of the molten liquid and melting dynamics, and the alteration of the melting interface shape due to nanoparticle concentration. The Nusselt number displayed intricate behavior during the melting process, changing with nanoparticle concentration. The study found that altering trapezoidal angles and nanoparticle concentrations could significantly affect melting time, with changes up to 62.5% observed. It was concluded that a trapezoidal enclosure with a slight outward angle (γ = 10°) was most effective in reducing interference and shortening melting time, offering valuable insights for optimizing PCM design for diverse applications.

Utilization of ANN technique to estimate the discharge coefficient for trapezoidal weir-gate

Abstract Developing and assessing the performance of water projects and irrigation networks is based on many factors, such as flow measurement. Weir and gate structures have been extensively utilized for flow measurement and to get rid of sediments. The process of modeling and estimating the coefficient of discharge in the weir is an essential part of hydraulic engineering. Recently the application of computer skills was adopted instead of traditional methods. In the present study, the artificial neural network (ANN) was adopted to estimate the coefficient of discharge for a combined weir that consisted of the trapezoidal weir and rectangular gate. For this purpose, the experimental data were collected and analyzed. The dimensional analysis was used to identify the effective dimensionless parameters related to the discharge coefficient. The developed ANN network structure was designed as 6-10-1 and adopted the default scaled conjugate gradient algorithm for training using SPSS V24 software. It was found that the proposed model with ten neurons was highly accurate in predicting the discharge coefficient. The sensitivity analysis was adopted to assess the performance of the ANN using different numbers of effective input parameters. Assessing five models, the ratio of upstream head to gate height (H/d), slope of trapezoidal angle (tan θ), and the ratio of distance between weir and gate and gate height (y/d) parameters are adequate for estimating the discharge coefficient compared to other parameters. ANN model with input parameters of H/d, h/d (h is the flow depth over the trapezoidal weir), b g/d (b g is the gate width), tan θ, b g/b (b is the total width of flume), and y/d shows reasonable accuracy with acceptable statistical indicators, coefficient of determination (R 2 = 0.87), relative error (RE = 0.096), and mean squared error (MSE = 1.86) for the discharge coefficient. The ANN model gave a good idea about which factors are more effective on the discharge coefficient, and the process of training the network is more accessible than the traditional method which represent the discharge coefficient by equation.

Role of surface microstructure and shape on light extraction efficiency enhancement of GaN micro-LEDs: A numerical simulation study

One of the bottlenecks for today’s micro-light-emitting-diodes (micro-LEDs) is the low light extraction efficiency. How to effectively boost this efficiency is especially important for micro-LEDs because their surface-to-volume ratio is much larger than normal LEDs. The trapezoidal chip structure, surface grating, and surface coarsening are simulated in this paper, with the aim to obtain their contributions to enhance the light extraction efficiency. Through the simulation, we have found that all of the three methods can increase the light extraction, but with different extents. When the trapezoidal angle of the mesa is 12°, the extraction efficiency reaches its maximum (by this method) of 64.5%. If the surface grating on n-GaN (the light output surface) has a period of 300 nm, a height of 147 nm and width of 243 nm, the light extraction efficiency can be as high as 72%, which is much higher than that of the micro-LED without any grating. For the random roughening of n-GaN, a maximum value of 56% can be obtained if the roughness extent is optimized. Our results are of reference value for scientists and engineers working in micro-LEDs and can serve as guidelines for GaN based high efficiency micro-LED design for future displays.

Comprehensive analysis of the variables influencing the techno-economic optimization of medium temperature linear Fresnel collectors

A Linear Fresnel Collector (LFC) is a solar concentrating technology with high potential for improvements and therefore significant cost reduction. However, LFC optimization studies found in literature show little agreement regarding optimal geometry. In this article, a study is presented to evaluate the trends of the main geometrical parameters in an optimization process of medium temperature linear Fresnel collectors (LFCs) with trapezoidal receiver. For this, a comprehensive LFC design model was developed. It includes an optical, a thermal, an annual integration of the collected energy and an economic sub-models coded in a hard-link way. This model was used to investigate the influence of the main LFC geometrical parameters and inputs on the levelized cost of heat (LCOH) produced. The geometrical parameters investigated were the number of mirrors, the width of mirrors, the gap between mirrors, the trapezoidal angle and the trapezoidal height of the receiver, while the inputs investigated were the location (Quito-Ecuador and Targassone-France), DNI data (TMY data and clear sky model) and the time frame of simulation (representative days or the whole year). Results show that the optimal LFC geometry depends mainly on the azimuthal movement of the Sun. Consequently, the trends of the energetic behavior of an LFC, when the geometrical parameters vary, are similar without regard of the latitude, DNI data or the time frame used for simulations. Reductions until 20% on the LCOH may be achieved by optimizing the geometry of such LFC.

Transverse Vibration Analysis of Axially Moving Trapezoidal Plates

Transverse vibration of axially moving trapezoidal plates is investigated. The differential equation of transverse vibration for a axially moving trapezoidal plate is established by D'Alembert principle. The original trapezoid region can be replaced by regular square region by the medium parameter method for the convenience of calculation. A generalized complex eigenvalue equation is derived by a discrete method (the differential quadrature method). The complex frequency curve of trapezoidal plate is obtained by calculating the eigenvalue equation. The change of the complex frequencies of the axially moving trapezoidal plates with the dimensionless axially moving speed is analyzed. The effects of the aspect ratio and the trapezoidal angle on instability type of the trapezoidal plate are discussed under different boundary conditions. The results of numerical analysis show that there are two main instability types of axially moving trapezoidal plate: divergence and flutter. The modal orders of the two types of instability are also different, which is related to the trapezoidal angle, aspect ratio and boundary condition of the trapezoidal plate.

A UWB Antenna Array Integrated with Multimode Resonator Bandpass Filter

This paper presents a novel design of a modified ultrawideband (UWB) antenna array integrated with a multimode resonator bandpass filter. First, a single UWB antenna is modified and studied, using a P-shape radiated patch instead of a full elliptical patch, for wide impedance bandwidth and high realized gain. Then, a two-element UWB antenna array is developed based on this modified UWB antenna with an inter-element spacing of 0.35 λL, in which λL is the free space wavelength at the lower UWB band edge of 3.1 GHz, compared to 0.27 λL of a reference UWB antenna array designed using a traditional elliptical patch shape. The partial ground plane is designed with a trapezoidal angle to enhance matching throughout the UWB frequency range. The mutual coupling reduction of a modified UWB antenna array enhances the reflection coefficient, bandwidth, and realized gain, maintaining the same size of 1.08 λ0 × 1.08 λ0 × 0.035 λ0 at 6.5 GHz center frequency as that of the reference UWB antenna array. The UWB antenna array performance is investigated at different inter-element spacing distances between the radiated elements. To add filtering capability to the UWB antenna array and eliminate interference from the out-of-band frequencies, a multimode resonator (MMR) bandpass filter (BPF) is incorporated in the feedline while maintaining a compact size. The measurement results showed a close agreement with simulated results. The proposed UWB filtering antenna array design achieved a wide fractional bandwidth of more than 109.87%, a high realized gain of more than 7.4 dBi, and a compact size of 1.08 λ0 × 1.08 λ0 × 0.035 λ0 at 6.5 GHz center frequency. These advantages make the proposed antenna suitable for UWB applications such as indoor tracking, radar systems and positioning applications.

Non-Darcian natural convection of a nanofluid due to triangular fins within trapezoidal enclosures partially filled with a thermal non-equilibrium porous layer

Numerical simulations for the convective transport due to triangular fins within an inclined trapezoidal enclosure that is filled by a nanofluid layer and a non-Darcy pours layer are conducted. The local thermal non-equilibrium model between the nanofluid and porous phases in the porous layer is applied. Various cases based on the perimeter of the triangular fin are considered. Suitable grid transformations are introduced to map the non-uniform physical domain to a rectangular domain. The transformed governing equations are solved using a non-orthogonal finite volume method with SIMPLE algorithm. The given results revealed that the average Nusselt number is enhanced by 95.60% at the thermal conductivity ratio (Kr) = 0.1 and 68.46% at Kr = 1 and 11.23% at Kr = 10 when the Nield parameter is varied from 1 to 1000. Also, the nanofluid activity is supported in cases of higher values of the aspect ratio A and the trapezoidal angle $$\varPhi$$ .

A Spectral Finite Difference Method for Analysis of a Fluid-Lubricated Herringbone Grooves Journal Bearing under a Special Case at Rectangle Groove

A spectral difference method is applied to get numerical solutions for a fluid-lubricated herringbone grooved journal bearing with trapezoidal grooves by previous work of the authors. However, an inexpedience in which Fourier series of the film profile does not converge at jump points of groove start or groove end in the case of rectangle groove was still remained. In the paper, an inexpedience of numerical analysis under a special case at rectangle groove is challenged to solve. As a result, for compensation of which Fourier series does not converge at jump points in a special case of rectangle groove, Fourier coefficient of fluid film thickness is proposed as taking the limit of which in a case trapezoidal groove at trapezoidal angle approaches 0.

Effect of column angles to rise velocity of a single bubble: a CFD study

The present study investigates the effect of trapezoidal type columns to rise velocity of a single bubble in quiescent water using a couple level set volume of fluid (CLSVOF) methods. The bubble rising characteristics such as spatial distribution and shape deformation in different types of trapezoidal columns with inclination angles of 3°, 6°, 9° from vertical wall will be presented. The results from these cases will be compared with a benchmark case which is based on a rectangular domain (0°). The bubble rising velocity reduces with the increase of trapezoidal angle. Subsequently, the bubble rising distance for a given particular total time reduces with the increase of the trapezoidal angle, which enhances the lateral distribution of a bubble from left to right and vice versa of the column with the increase of the time, may enhance the gas hold up, the heat and mass transfer between gas and liquid.

Impacts of Trapezoidal Fin of 20-nm Double-Gate FinFET on the Electrical Characteristics of Circuits

In this study, we analyze the impacts of the trapezoidal fin shape of a double-gate FinFET on the electrical characteristics of circuits. The trapezoidal nature of a fin body is generated by varying the angle of the sidewall of the FinFET. A technology computeraided-design (TCAD) simulation shows that the onstate current increases, and the capacitance becomes larger, as the bottom fin width increases. Several circuit performance metrics for both digital and analog circuits, such as the fan-out 4 (FO4) delay, ring oscillator (RO) frequency, and cut-off frequency, are evaluated with mixed-mode simulations using the 3D TCAD tool. The trapezoidal nature of the FinFET results in different effects on the driving current and gate capacitance. As a result, the propagation delay of an inverter decreases as the angle increases because of the higher on-current, and the FO4 speed and RO frequency increase as the angle increases but decrease for wider angles because of the higher impact on the capacitance rather than the driving strength. Finally, the simulation reveals that the trapezoidal angle range from 10° to 20° is a good tradeoff between larger on-current and higher capacitance for an optimum trapezoidal FinFET shape.

Wing performance and 3-D vortical structure formation in flapping flight

Numerical simulations of the three-dimensional flow around a modelled insect wing were performed to investigate the performance in flapping flight and to provide insight into the vortex dynamics and associated force generation. Different parameters relevant for three-dimensional flapping wing aerodynamics have been studied, notably the angle of attack in mid-stroke, the Rossby number, the Reynolds number and the stroke kinematic pattern. A parametric study has been made for these parameters, notably for the hovering flight regime. The leading-edge vortex is confirmed to be important for the gain in lift, it being larger and more stable at angles of attack larger than about 30°. At smaller angles of attack, the leading-edge vortex development is insufficient to increase the lift, instead the lift decreases. It is observed that the trend of the force development over the cycle and the effect of the angle of attack is similar for revolving and translating wings. However, a flapping wing motion with a revolving character has an important lift-enhancing effect, at a small penalty of drag. Although the variations in lift and drag with Reynolds number are found to be larger at lower Rossby numbers, the lift-enhancing effect of the revolving wing appears not strongly dependent on Reynolds number. Application of a ‘trapezoidal angle of attack’ pattern with increased angular rotation at stroke reversal showed a significant performance increase. It was further shown how the variation in lift and drag can be significantly influenced by introducing deviation in the stroke pattern. A comparison between the three-dimensional simulations and two-dimensional simulations (for forward flight conditions) displayed similar trends with respect to the influence of the angle of attack. However, the latter do not account for finite wing and tip vortex effects which were found to have an important impact on the LEV development.

Flow and heat transfer investigation behind trapezoidal rib using PIV and LCT measurements

The present work is an experimental investigation inside a rectangular duct for flow behind a trapezoidal type of rib with chamfering angle α (toward the direction of flow) at different Reynolds numbers. Chamfering angle α has been varied in between 0° and 20° with an increment of 5° and subsequently detailed fluid flow and heat transfer experiments have been performed at four different Reynolds numbers, that is, 9,400, 27,120, 44,600, and 61,480 (based on hydraulic diameter of the duct). In order to investigate the detailed fluid flow and heat transfer characteristics together, a distinct experimental setup has been designed while using 2-D particle image velocimetry and liquid crystal thermography, respectively. Flow investigations have been restricted within the streamwise location of x/e ≤ 11, while the region of interest for heat transfer measurement goes up to x/e ≤ 50. The emphasis is toward assessing and analyzing the potential impact of varying chamfering angle over the flow structures, and its subsequent effect on far downstream heat transfer enhancement, as well as its role in obviating the hot spots in the adjacent vicinity behind the chamfered rib turbulators. Transient heat transfer investigation has been performed for evaluating the surface heat transfer enhancement. Results are documented in terms of stream traces, mean and rms velocity fields, streamwise Reynolds stresses and vorticity distribution, and surface and spanwise averaged augmentation Nusselt numbers. The reattachment length has been identified for all of the configurations, and the turbulent characteristics have been discussed in reference to the reattaching shearing layer and its potential impact on the size of the recirculation bubble for different configurations and conditions. The result showed the successful impact of changing the trapezoidal angle α by manipulating the small-scale vortices at the leeward corner of the rib which helps in obviating the hot spots. Furthermore, the presence of large scale unsteady vortical structure within the shear layer has been confirmed, and it has been subsequently associated with heat transfer enhancement in the far downstream region.

The Effects of Trapezoidal Groove on a Self-Acting Fluid-Lubricated Herringbone Grooves Journal Bearing

As a self-acting fluid-lubricated herringbone grooves journal bearing, a trapezoidal cross-sectional shape of grooves is considered. Trapezoidal groove shape effects on its bearing characteristics such as variations of load capacity, attitude, and friction torque for various trapezoidal angle of groove are determined.

New design of a gamma camera detector with reduced edge effect for breast imaging

In recent years, there has been a growing interest in developing small gamma cameras dedicated to breast imaging. We designed a new detector with trapezoidal shape to expand the field of view (FOV) of camera without increasing its dimensions. To find optimal parameters, images of point sources at the edge area as functions of the angle and optical treatment of crystal side surface were simulated by using a DETECT2000. Our detector employs monolithic CsI(Tl) with dimensions of 48.0×48.0×6.0 mm coupled to an array of photo-sensors. Side surfaces of crystal were treated with three different surface finishes: black absorber, metal reflector and white reflector. The trapezoidal angle varied from 45° to 90° in steps of 15°. Gamma events were generated on 15 evenly spaced points with 1.0 mm spacing in the X-axis starting 1.0 mm away from the side surface. Ten thousand gamma events were simulated at each location and images were formed by calculating the Anger-logic. The results demonstrated that all the 15 points could be identified only for the crystal with trapezoidal shape having 45° angle and white reflector on the side surface. In conclusion, our new detector proved to be a reliable design to expand the FOV of small gamma camera for breast imaging.

Fully developed forced convection through trapezoidal and hexagonal ducts

Laminar, fully developed flow through single- and double-trapezoidal (or hexagonal) ducts is modeled using a finite-difference method. A coordinate transformation is employed to map the irregular flow cross-section onto a rectangular computational domain. Both H1 and T thermal boundary conditions are considered as they represent the fundamental limiting conditions in most practical applications. Solutions for velocity and temperature variations are obtained for a wide range of duct aspect ratios and with four different trapezoidal angles. The friction factor and Nusselt number results show a strong dependence on duct geometry (aspect ratio γ and trapezoidal angle θ). The variations of f Re, Nu H1 , and Nu T with duct aspect ratio for each θ-valued duct are presented in the form of polynomials in γ. These equations describe the computed numerical values within ±2% for single-trapezoidal and within ±1.5% for hexagonal ducts and are of much importance to the design of compact heat exchangers.