scholarly journals A Numerical Swallowing-Capacity Analysis of a Vacant, Cylindrical, Bi-Directional Tidal Turbine Duct in Aligned & Yawed Flow Conditions

2021 ◽  
Vol 9 (2) ◽  
pp. 182
Author(s):  
Mitchell G. Borg ◽  
Qing Xiao ◽  
Steven Allsop ◽  
Atilla Incecik ◽  
Christophe Peyrard
Keyword(s):  
Free Stream ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Flow Conditions ◽  
Cross Sectional ◽  
Pressure Drag ◽  
Tidal Turbine ◽  
Cross Sectional Profile ◽  
Sectional Profile ◽  
Swallowing Capacity

Introducing a duct along the perimeter of a rotor has been acknowledged to augment turbine performance. The outcome causation due to a bi-directional, cylindrical shroud, however, is uncertain. This study analyses the hydrodynamic swallowing capacity of a true-scale, vacant duct for tidal turbine applications in aligned and yawed inlet flow conditions by utilising three-dimensional unsteady computational fluid dynamics. The performance is investigated within free-stream magnitudes of 1 to 7 m.s−1, and a bearing angular range of 0° to 45° with the duct axis. In proportion to the free-stream magnitude, the normalised axial velocity through the duct increases as a result of a diminishment in pressure drag. Within yawed flow, the maximum capacity falls at a bearing of 23.2°, resulting in a performance increase of 4.13% above that at aligned flow conditions. The analysis concludes that the augmentation at yawed flow occurs due to the duct cross-sectional profile lift variation with angle-of-attack. Towards nominal yaw angle, the internal static pressure reduces, permitting a higher mass-flow rate. Beyond the nominal angle-of-attack, flow separation occurs within the duct, increasing pressure drag, thereby reducing the swallowing capacity.

Topology Synthesis of Extrusion-Based Nonlinear Transient Designs

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Neal M. Patel ◽  
Charles L. Penninger ◽  
John E. Renaud
Keyword(s):  
Cross Section ◽  
Three Dimensional ◽  
Optimization Methods ◽  
Constant Cross Section ◽  
Cross Sectional ◽  
Design Concepts ◽  
Nonlinear Transient ◽  
Cross Sectional Profile ◽  
Sectional Profile ◽  
Finishing Processes

Many practical structural designs require that the structure is easily manufactured. Design concepts synthesized using conventional topology optimization methods are typically not easily manufactured, in that multiple finishing processes are required to construct the component. A manufacturing technique that requires only minimal effort is extrusion. Extrusion is a manufacturing process used to create objects of a fixed cross-sectional profile. The result of using this process is lower costs for the manufacture of the final product. In this paper, a hybrid cellular automaton algorithm is developed to synthesize constant cross section structures that are subjected to nonlinear transient loading. The novelty of the proposed method is the ability to generate constant cross section topologies for plastic-dynamic problems since the issue of complex gradients can be avoided. This methodology is applied to extrusions with a curved sweep along the direction of extrusion as well. Three-dimensional examples are presented to demonstrate the efficiency of the proposed methodology in synthesizing these structures. Both static and dynamic loading cases are studied.

Nanometer-Scale Dimensional Metrology With the Nist Calibrated Atomic Force Microscope

1999 ◽  
Vol 5 (S2) ◽  
pp. 958-959
Author(s):  
R. Dixson ◽  
R. Köning ◽  
V. W. Tsai ◽  
J. Fu ◽  
T. V. Vorburger
Keyword(s):  
Three Dimensional ◽  
Critical Dimension ◽  
Dimensional Metrology ◽  
Cross Sectional ◽  
Atomic Force ◽  
Reflected Light ◽  
Wide Range ◽  
Cross Sectional Profile ◽  
Sectional Profile ◽  
Depth Feature

Atomic force microscopes (AFMs), which generate three dimensional images with nanometer level resolution, are increasingly being used as tools for sub-micrometer dimensional metrology in a wide range of applications. Measurements commonly performed with AFMs are feature spacing (pitch), feature height (or depth), feature width (critical dimension), and surface roughness. To perform accurate measurements, the scales of an AFM must be calibrated regularly. Presently available standards for this purpose are calibrated using stylus instruments and optical techniques. The effectiveness of this approach, however, is limited by the differences in the working ranges of the various techniques and by questions of methods divergence. Such divergence may occur between measurements made by instruments using different techniques to measure the same feature. A reflected light microscope and an AFM, for example, may have differing sensitivity to the cross-sectional profile of measured lines. For sufficiently steep lines, an AFM tip will only contact the features near the tops.

X-Ray Replication of Submicrometer Linewidth Patterns

1977 ◽  
Vol 35 ◽  
pp. 136-137
Author(s):  
Henry I. Smith ◽  
D.C. Flanders
Keyword(s):  
Electron Beam Lithography ◽  
Cross Sectional ◽  
X Ray ◽  
Electron Backscattering ◽  
Spatial Frequencies ◽  
Cross Sectional Profile ◽  
Carbon Foils ◽  
Sectional Profile ◽  
And Control ◽  
Soft Radiation

Scanning electron beam lithography has been used for a number of years to write submicrometer linewidth patterns in radiation sensitive films (resist films) on substrates. On semi-infinite substrates, electron backscattering severely limits the exposure latitude and control of cross-sectional profile for patterns having fundamental spatial frequencies below about 4000 Å(l),Recently, STEM'S have been used to write patterns with linewidths below 100 Å. To avoid the detrimental effects of electron backscattering however, the substrates had to be carbon foils about 100 Å thick (2,3). X-ray lithography using the very soft radiation in the range 10 - 50 Å avoids the problem of backscattering and thus permits one to replicate on semi-infinite substrates patterns with linewidths of the order of 1000 Å and less, and in addition provides means for controlling cross-sectional profiles. X-radiation in the range 4-10 Å on the other hand is appropriate for replicating patterns in the linewidth range above about 3000 Å, and thus is most appropriate for microelectronic applications (4 - 6).

scholarly journals Bonding widths of Deposited Polymer Strands in Additive Manufacturing

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 871
Author(s):  
Cheng Luo ◽  
Manjarik Mrinal ◽  
Xiang Wang ◽  
Ye Hong
Keyword(s):  
Polymer Melt ◽  
Acrylonitrile Butadiene Styrene ◽  
High Viscosity ◽  
Numerical Results ◽  
Fused Filament Fabrication ◽  
Cross Sectional ◽  
Nozzle Height ◽  
Special Cases ◽  
Cross Sectional Profile ◽  
Sectional Profile

In this study, we explore the deformation of a polymer extrudate upon the deposition on a build platform, to determine the bonding widths between stacked strands in fused-filament fabrication. The considered polymer melt has an extremely high viscosity, which dominates in its deformation. Mainly considering the viscous effect, we derive analytical expressions of the flat width, compressed depth, bonding width and cross-sectional profile of the filament in four special cases, which have different combinations of extrusion speed, print speed and nozzle height. We further validate the derived relations, using our experimental results on acrylonitrile butadiene styrene (ABS), as well as existing experimental and numerical results on ABS and polylactic acid (PLA). Compared with existing theoretical and numerical results, our derived analytic relations are simple, which need less calculations. They can be used to quickly predict the geometries of the deposited strands, including the bonding widths.

Aspects of Shear Layer Unsteadiness in a Three-Dimensional Supersonic Wake

2005 ◽  
Vol 127 (6) ◽  
pp. 1085-1094 ◽  
Author(s):  
Alan L. Kastengren ◽  
J. Craig Dutton
Keyword(s):  
Shear Layer ◽  
Stream Flow ◽  
Free Stream ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Base Flow ◽  
Recirculation Region ◽  
Side View ◽  
Near Wake ◽  
Supersonic Wake

The near wake of a blunt-base cylinder at 10° angle-of-attack to a Mach 2.46 free-stream flow is visualized at several locations to study unsteady aspects of its structure. In both side-view and end-view images, the shear layer flapping grows monotonically as the shear layer develops, similar to the trends seen in a corresponding axisymmetric supersonic base flow. The interface convolution, a measure of the tortuousness of the shear layer, peaks for side-view and end-view images during recompression. The high convolution for a septum of fluid seen in the middle of the wake indicates that the septum actively entrains fluid from the recirculation region, which helps to explain the low base pressure for this wake compared to that for a corresponding axisymmetric wake.

Measurement of cross-sectional profile for sub-15nm hp LS patterns in nanoimprint templates using small-angle x-ray scattering

2020 ◽  
Author(s):  
Kazuki Hagihara ◽  
Eiji Yamanaka ◽  
Yoshiyasu Ito ◽  
Kiyoshi Ogata ◽  
Kazuhiko Omote ◽  
...  
Keyword(s):  
Small Angle ◽  
Cross Sectional ◽  
X Ray ◽  
X Ray Scattering ◽  
Cross Sectional Profile ◽  
Sectional Profile ◽  
Ray Scattering

Torsional Stiffness of a Thin-Walled Beam Braced by Pinned or Rigidly Fixed Transverse Diaphragms

1973 ◽  
Vol 15 (5) ◽  
pp. 351-356
Author(s):  
T. Harrison ◽  
J. M. Siddall
Keyword(s):  
Experimental Evidence ◽  
Theoretical Work ◽  
Torsional Stiffness ◽  
Cross Sectional ◽  
Cross Sectional Profile ◽  
Thin Walled ◽  
Sectional Profile ◽  
Good Agreement

The torsional stiffness of a thin-walled beam of open cross-sectional profile braced by evenly spaced transverse diaphragms is studied. Diaphragms rigidly fixed or attached by frictionless pins are treated and it is seen that, in either case, the only effect is to modify the St Venant torsional constant for the thin-walled beam. The theoretical work is supported by experimental evidence from two braced perspex channels which simulate the two assumed methods of attaching the diaphragms. Good agreement is demonstrated.

scholarly journals Influence of Geometric Parameters on Aerodynamic and Acoustic Performances of Bladeless Fans

2019 ◽  
Author(s):  
Ang Li ◽  
Jun Chen ◽  
Yangfan Liu ◽  
Stuart Bolton ◽  
Patricia Davies
Keyword(s):  
Cross Section ◽  
Fluid Dynamic ◽  
Geometric Parameters ◽  
Design Stage ◽  
Air Velocity ◽  
Cross Sectional ◽  
Future Design ◽  
Cross Sectional Profile ◽  
The Cross ◽  
Sectional Profile

Abstract In recent years, the bladeless fan that does not have visible impellers have been widely applied in household appliances. Since the customers are particularly sensitive to noise and the strength of wind generated by the fan, the aerodynamic and acoustic performances of the fan need to be accurately characterized in the design stage. In this study, computational fluid dynamic (CFD) and computational aeroacoustics (CAA) are applied to investigate the performances of different designs of a bladeless fan model. The influence of four parameters, namely the airfoil selection for cross-section of the wind channel, the slit width, the height of cross-section and the location of the slit, is investigated. The results indicate the streamwise air velocity increases significantly by narrowing the outlet, but the noise level increases simultaneously. In addition, the generated noise increases while the height of fan cross-section increases, and a 4mm height of the cross section is optimal for aerodynamic performance. When the slit is closer to the location of maximum thickness, the performances of the bladeless fan increases. Moreover, the performance is not changed significantly by changing the cross-sectional profile. Finally, the optimal geometric parameters are identified to guide the future design of the bladeless fan.

Twisting and Bending of Thin-Walled Prismatic Beams of Open Cross-Sectional Profile

1970 ◽  
Vol 12 (2) ◽  
pp. 130-134 ◽  
Author(s):  
T. Harrison
Keyword(s):  
Cross Sections ◽  
Virtual Work ◽  
Cross Sectional ◽  
Transverse Bending ◽  
Prismatic Beam ◽  
Loading System ◽  
Cross Sectional Profile ◽  
Thin Walled ◽  
Sectional Profile ◽  
Principle Of Virtual Displacements

Previous studies of the behaviour, in generalized co-ordinates, of thin-walled, prismatic beams of open cross-sectional profile have included, explicitly, only the effects of distributed transverse forces, q x and q y, distributed longitudinal forces, q z, and distributed torsional couples, m z. Using the principle of virtual displacements, the work of previous investigators is extended to include, quite generally, the effects of the hitherto neglected distributed couples, m x and m y. The derivation of the differential equation relating to the twisting of an open-section prismatic beam is presented fully whilst those relating to transverse and axial displacements of cross-sections are merely stated. The kinematic and static boundary conditions for a cantilever are also established from the virtual work equations. These show that the free-end shear boundary condition associated with transverse bending which is usually adopted in engineering calculations is inadequate for such a generalized loading system.

scholarly journals CORRELATION BETWEEN FIBER LENGTH, ULTRASTRUCTURE, AND THE LENGTH-TENSION RELATIONSHIP OF MAMMALIAN SMOOTH MUSCLE

1972 ◽  
Vol 52 (1) ◽  
pp. 105-116 ◽  
Author(s):  
Peter H. Cooke ◽  
Fredric S. Fay
Keyword(s):  
Fiber Length ◽  
Ultrastructural Organization ◽  
Cross Sectional ◽  
Dense Bodies ◽  
Tentative Model ◽  
Functional Consequences ◽  
Cross Sectional Profile ◽  
Sectional Profile ◽  
Basic Features ◽  
Relationship Of

The length-tension relationship was determined for strips of guinea pig taenia coli and correlated with the length and ultrastructural organization of the component fibers. The mean fiber length in "stretched" strips (passive ≥ active tension) was 30% greater than that for fibers in "unstretched" strips (active >> passive tension). In stretched fibers the dense bodies and 100 A diameter myofilaments were consolidated into a mass near the center of fibers in cross-sectional profile. The thick myofilaments were segregated into the periphery of the fiber profiles. In unstretched fibers the dense bodies-100 A diameter filaments and the thick myofilaments were uniformly distributed throughout cross-sectional profiles. A tentative model is proposed to account for the change in fiber length and ultrastructural organization that accompanies stretch. The basic features of the model require the dense bodies to be linked together into a network by the 100 A diameter filaments. The functional consequences of stretching the fibers are discussed in relation to the model proposed for this network.

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