New and improved channel cross section with piecewise linear or smooth sides

This paper presents a new and improved channel cross section with m-segment linear sides and horizontal bottom (MSLS). For large m, the section sides become smooth curves, thus providing the designer with flexibility in using either piecewise linear or smooth channel sides with the same formulation. General simple formulas for the area and perimeter are presented for section sides with m linear segments. An optimization model, which implements the general formulas and minimizes the construction cost, is presented and applied using an example. For sections with piecewise linear sides, where the surface lining unit cost increases as the number of sides increases, the MSLS section was found to be more economical than a section with two-segment linear sides when the rate of increase in cost is not large. The smooth MSLS was found to be always more economical than the two-segment parabolic side section and the parabolic side section. The MSLS, which is more economical, yet simpler, than other section types is useful for a wide range of applications involving small and large channels.

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Coriolis Effects on the Flow Field Inside a Rotating Triangular Channel for Leading Edge Cooling

Journal of Turbomachinery ◽

10.1115/1.4025570 ◽

2013 ◽

Vol 136 (3) ◽

Cited By ~ 4

Author(s):

Matteo Pascotto ◽

Alessandro Armellini ◽

Claudio Mucignat ◽

Luca Casarsa

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Flow Structure ◽

Cross Section ◽

Working Conditions ◽

Rotation Axis ◽

Leading Edge ◽

Channel Cross Section ◽

Smooth Channel ◽

Static Conditions

The flow field inside a rotating smooth radial channel with a triangular shaped cross section is investigated. Test conditions resemble those pertaining to the passages used for the internal cooling of the gas turbine blade's leading edge. Heat transfer data are also available from the literature on the same geometry and at comparable working conditions and have been profitably used for a combined aerothermal analysis. The model consists of a straight smooth channel with an equilateral triangle cross section. The rotation axis is aligned with one of the triangle bisectors. Two dimensional particle image velocimetry (PIV) and stereo-PIV were used in order to characterize the inlet flow (in static conditions) and the rotation-induced secondary flow in the channel cross section at Re = 20,000, Ro = 0.2 and Re = 10,000, Ro = 0.4. A wider range of working conditions (Re = 10,000–40,000, Ro = 0.2–0.6) was explored by means of Reynolds averaged Navier–Stokes (RANS) simulations carefully validated by the available PIV data. The turbulence was modeled by means of the shear stress transport (SST) model with a hybrid near-wall treatment. The results show that the rotation-induced flow structure is rather complicated and show relevant differences compared to the flow models that have been considered thus far. Indeed, the secondary flow turned out to be characterized by the presence of two or more vortex cells, depending on channel location and Ro number. No separation or reattachment of these structures is found on the channel walls but they have been observed at the channel apexes. The stream-wise velocity distribution shows a velocity peak close to the lower apex and the overall flow structure does not reach a steady configuration along the channel length. This evolution is fastened (in space) if the rotation number is increased while changes of the Re number have no effect. Finally, due to the understanding of the flow mechanisms associated with rotation, it was possible to provide a precise justification of the channel thermal behavior.

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Numerical and Theoretical Study of Performance and Mechanical Behavior of PEM-FC Using Innovative Channel Geometrical Configurations

Applied Sciences ◽

10.3390/app11125597 ◽

2021 ◽

Vol 11 (12) ◽

pp. 5597

Author(s):

Hussein A. Z. AL-bonsrulah ◽

Mohammed J. Alshukri ◽

Ammar I. Alsabery ◽

Ishak Hashim

Keyword(s):

Fuel Cell ◽

Cross Section ◽

Rectangular Channel ◽

Compressive Load ◽

Proton Exchange ◽

Channel Cross Section ◽

Channel Height ◽

Cross Sectional ◽

Triangular Channel ◽

Higher Power

Proton exchange membrane fuel cell (PEM-FC) aggregation pressure causes extensive strains in cell segments. The compression of each segment takes place through the cell modeling method. In addition, a very heterogeneous compressive load is produced because of the recurrent channel rib design of the dipole plates, so that while high strains are provided below the rib, the domain continues in its initial uncompressed case under the ducts approximate to it. This leads to significant spatial variations in thermal and electrical connections and contact resistances (both in rib–GDL and membrane–GDL interfaces). Variations in heat, charge, and mass transfer rates within the GDL can affect the performance of the fuel cell (FC) and its lifetime. In this paper, two scenarios are considered to verify the performance and lifetime of the PEM-FC using different innovative channel geometries. The first scenario is conducted by adopting a constant channel height (H = 1 mm) for all the differently shaped channels studied. In contrast, the second scenario is conducted by taking a constant channel cross-sectional area (A = 1 mm2) for all the studied channels. Therefore, a computational fluid dynamics model (CFD) for a PEM fuel cell is formed through the assembly of FC to simulate the pressure variations inside it. The simulation results showed that a triangular cross-section channel provided the uniformity of the pressure distribution, with lower deformations and lower mechanical stresses. The analysis helped gain insights into the physical mechanisms that lead to the FC’s durability and identify important parameters under different conditions. The model shows that it can assume the intracellular pressure configuration toward durability and appearance containing limited experimental data. The results also proved that the better cell voltage occurs in the case of the rectangular channel cross-section, and therefore, higher power from the FC, although its durability is much lower compared to the durability of the triangular channel. The results also showed that the rectangular channel cross-section gave higher cell voltages, and therefore, higher power (0.63 W) from the fuel cell, although its durability is much lower compared to the durability of the triangular channel. Therefore, the triangular channel gives better performance compared to other innovative channels.

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Flexural bearing capacity and failure mechanism of CFRP-aluminum laminate beam with double-channel cross-section

Science and Engineering of Composite Materials ◽

10.1515/secm-2021-0012 ◽

2021 ◽

Vol 28 (1) ◽

pp. 139-152

Author(s):

Teng Huang ◽

Dongdong Zhang ◽

Yaxin Huang ◽

Chengfei Fan ◽

Yuan Lin ◽

...

Keyword(s):

Carbon Fiber ◽

Bearing Capacity ◽

Failure Mechanism ◽

Cross Section ◽

Failure Criterion ◽

Failure Modes ◽

Channel Cross Section ◽

Fiber Layer ◽

Flexural Bearing Capacity ◽

Double Channel

Abstract In this study, the flexural bearing capacity and failure mechanism of carbon fiber-reinforced aluminum laminate (CARALL) beams with a double-channel cross-section and a 3/2 laminated configuration were experimentally and numerically studied. Two types of specimens using different carbon fiber layup configurations ([0°/90°/0°]3 and [45°/0°/−45°]3) were fabricated using the pressure molding thermal curing forming process. The double-channel CARALL beams were subjected to static three-point bending tests to determine their failure behaviors in terms of ultimate bearing capacity and failure modes. Owing to the shortcomings of the two-dimensional Hashin failure criterion, the user-defined FORTRAN subroutine VUMAT suitable for the ABAQUS/Explicit solver and an analysis algorithm were established to obtain a progressive damage prediction of the CFRP layer using the three-dimensional Hashin failure criterion. Various failure behaviors and mechanisms of the CARALL beams were numerically analyzed. The results indicated that the numerical simulation was consistent with the experimental results for the ultimate bearing capacity and final failure modes, and the failure process of the double-channel CARALL beams could be revealed. The ultimate failure modes of both types of double-channel CARALL beams were local buckling deformation at the intersection of the upper flange and web near the concentrated loading position, which was mainly caused by the delamination failure among different unidirectional plates, tension and compression failure of the matrix, and shear failure of the fiber layers. The ability of each fiber layer to resist damage decreased in the order of 90° fiber layer > 0° fiber layer > 45° fiber layer. Thus, it is suggested that 90°, 0°, and 45° fiber layers should be stacked for double-channel CARALL beams.

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Fractal-induced 2D flexible net undulation

Scientific Reports ◽

10.1038/s41598-021-86418-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Michael Joon Seng Goh ◽

Yeong Shiong Chiew ◽

Ji Jinn Foo

Keyword(s):

3D Reconstruction ◽

Cross Section ◽

Channel Cross Section ◽

Time Varying ◽

Blockage Ratio ◽

Transient Time ◽

Cross Sectional ◽

Velocity Fluctuations ◽

Square Grid ◽

Multilength Scale

AbstractA net immersed in fractal-induced turbulence exhibit a transient time-varying deformation. The anisotropic, inhomogeneous square fractal grid (SFG) generated flow interacts with the flexible net to manifest as visible cross-sectional undulations. We hypothesize that the net’s response may provide a surrogate in expressing local turbulent strength. This is analysed as root-mean-squared velocity fluctuations in the net, displaying intensity patterns dependent on the grid conformation and grid-net separation. The net’s fluctuation strength is found to increase closer to the turbulator with higher thickness ratio while presenting stronger fluctuations compared to regular-square-grid (RSG) of equivalent blockage-ratio, σ. Our findings demonstrate a novel application where 3D-reconstruction of submerged nets is used to experimentally contrast the turbulence generated by RSG and multilength scale SFGs across the channel cross-section. The net’s response shows the unique turbulence developed from SFGs can induce 9 × higher average excitation to a net when compared against RSG of similar σ.

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PIECEWISE AFFINE SYSTEM MODELING AND CONTROL OF PWM CONVERTERS

Journal of Circuits System and Computers ◽

10.1142/s0218126607003526 ◽

2007 ◽

Vol 16 (01) ◽

pp. 113-128 ◽

Cited By ~ 7

Author(s):

FARZAD TAHAMI ◽

BEHROOZ MOLAEI

Keyword(s):

High Performance ◽

Piecewise Linear ◽

System Modeling ◽

Synthesis Method ◽

Operating Point ◽

Approximation Technique ◽

Piecewise Affine ◽

Pwm Converters ◽

Linear Controller ◽

Wide Range

The averaged switch modeling approach is a powerful method for representing the behavior of a wide variety of converters through equivalent circuits. The model is not linear and it is common to perform a small signal linearization about an operating point and design a linear controller. Models obtained with such method involve considerable approximation and produce results that are limited for high performance controller designs. In this paper a piecewise affine approximation technique is introduced for modeling PWM converters. This model is much more precise in predicting the dynamic response of averaged nonlinear model comparing the linear model. This paper also presents a piecewise linear controller synthesis method for PWM converters described by the proposed PWA model. The proposed controller is very efficient and effective. The design method is well suited for converters having a wide range of variation about their operating point. A simulation example on buck-boost converter is presented to demonstrate the performance of the proposed method for modeling the dynamics of the converter and designing the appropriate controller.

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Closure to “Improved Channel Cross Section with Two-Segment Parabolic Sides and Horizontal Bottom” by Said M. Easa

Journal of Irrigation and Drainage Engineering ◽

10.1061/(asce)ir.1943-4774.0000246 ◽

2010 ◽

Vol 136 (9) ◽

pp. 667-670 ◽

Cited By ~ 2

Author(s):

Said M. Easa

Keyword(s):

Cross Section ◽

Channel Cross Section ◽

Horizontal Bottom

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Long waves in a straight channel with non-uniform cross-section

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.147 ◽

2015 ◽

Vol 770 ◽

pp. 156-188 ◽

Cited By ~ 5

Author(s):

Patricio Winckler ◽

Philip L.-F. Liu

Keyword(s):

Boundary Layer ◽

Wave Propagation ◽

Cross Section ◽

Three Dimensional ◽

Channel Cross Section ◽

Cross Sectional ◽

New Model ◽

One Dimensional ◽

Uniform Channel ◽

The Cross

A cross-sectionally averaged one-dimensional long-wave model is developed. Three-dimensional equations of motion for inviscid and incompressible fluid are first integrated over a channel cross-section. To express the resulting one-dimensional equations in terms of the cross-sectional-averaged longitudinal velocity and spanwise-averaged free-surface elevation, the characteristic depth and width of the channel cross-section are assumed to be smaller than the typical wavelength, resulting in Boussinesq-type equations. Viscous effects are also considered. The new model is, therefore, adequate for describing weakly nonlinear and weakly dispersive wave propagation along a non-uniform channel with arbitrary cross-section. More specifically, the new model has the following new properties: (i) the arbitrary channel cross-section can be asymmetric with respect to the direction of wave propagation, (ii) the channel cross-section can change appreciably within a wavelength, (iii) the effects of viscosity inside the bottom boundary layer can be considered, and (iv) the three-dimensional flow features can be recovered from the perturbation solutions. Analytical and numerical examples for uniform channels, channels where the cross-sectional geometry changes slowly and channels where the depth and width variation is appreciable within the wavelength scale are discussed to illustrate the validity and capability of the present model. With the consideration of viscous boundary layer effects, the present theory agrees reasonably well with experimental results presented by Chang et al. (J. Fluid Mech., vol. 95, 1979, pp. 401–414) for converging/diverging channels and those of Liu et al. (Coast. Engng, vol. 53, 2006, pp. 181–190) for a uniform channel with a sloping beach. The numerical results for a solitary wave propagating in a channel where the width variation is appreciable within a wavelength are discussed.

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Host-Plant Variations Affect the Biotic Potential, Survival, and Population Projection of Myzus persicae (Hemiptera: Aphididae)

Insects ◽

10.3390/insects12050375 ◽

2021 ◽

Vol 12 (5) ◽

pp. 375

Author(s):

Muhammad Yasir Ali ◽

Tayyaba Naseem ◽

Muhammad Arshad ◽

Ijaz Ashraf ◽

Muhammad Rizwan ◽

...

Keyword(s):

Myzus Persicae ◽

Growth Parameters ◽

Population Projection ◽

Chili Pepper ◽

Intrinsic Rate Of Increase ◽

Economic Damage ◽

Pepper Plant ◽

Net Reproductive Rate ◽

Rate Of Increase ◽

Wide Range

The green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae), a polyphagous insect pest is a major threat to a wide range of crops worldwide. Aiming to evaluate the life history traits of M. persicae, feeding on different host plants, we used five vegetables: cabbage, Brassica oleracea (Brassicaceae); chinese cabbage, B. rapa (Brassicaceae); chili pepper, Capsicum annum (Solanaceae); crown daisy, Chrysanthemum coronarium (Asteraceae); and eggplant, Solanum melongena (Solanaceae). TWOSEX-MSchart software was used for the statistical analysis about the age-stage, two-sex life table theory. The highest fecundity (69.65 individuals) rate of M. persicae, intrinsic rate of increase (r = 0.425 d−1), finite rate of increase (λ = 1.531 d−1), net reproductive rate (R0 = 69.65 offspring), and shortest mean generation time (T = 9.964 d) were recorded on the chili pepper plant. Whereas, lower fitness occurred on cabbage. The findings attained from population growth parameters indicate that chili pepper is the most susceptible plant, while cabbage is resistant to aphids. Population projection results also supported this statement, as the final total population size on cabbage was significantly lower than other plants. The reported information would be useful for devising integrated pest management programs, particularly those involving M. persicae. This information also suggests the adaptability of M. persicae causing economic damage to these vegetable cultivars.

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