Wake Flow of Single and Multiple Yawed Cylinders

2004 ◽  
Vol 126 (5) ◽  
pp. 861-870 ◽  
Author(s):  
A. Thakur ◽  
X. Liu ◽  
J. S. Marshall
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Wake Flow ◽  
Upstream Region ◽  
Two Dimensional ◽  
Cylinder Wake ◽  
Dimensional Approximation ◽  
The Face ◽  
Drag And Lift

An experimental and computational study is performed of the wake flow behind a single yawed cylinder and a pair of parallel yawed cylinders placed in tandem. The experiments are performed for a yawed cylinder and a pair of yawed cylinders towed in a tank. Laser-induced fluorescence is used for flow visualization and particle-image velocimetry is used for quantitative velocity and vorticity measurement. Computations are performed using a second-order accurate block-structured finite-volume method with periodic boundary conditions along the cylinder axis. Results are applied to assess the applicability of a quasi-two-dimensional approximation, which assumes that the flow field is the same for any slice of the flow over the cylinder cross section. For a single cylinder, it is found that the cylinder wake vortices approach a quasi-two-dimensional state away from the cylinder upstream end for all cases examined (in which the cylinder yaw angle covers the range 0⩽ϕ⩽60°). Within the upstream region, the vortex orientation is found to be influenced by the tank side-wall boundary condition relative to the cylinder. For the case of two parallel yawed cylinders, vortices shed from the upstream cylinder are found to remain nearly quasi-two-dimensional as they are advected back and reach within about a cylinder diameter from the face of the downstream cylinder. As the vortices advect closer to the cylinder, the vortex cores become highly deformed and wrap around the downstream cylinder face. Three-dimensional perturbations of the upstream vortices are amplified as the vortices impact upon the downstream cylinder, such that during the final stages of vortex impact the quasi-two-dimensional nature of the flow breaks down and the vorticity field for the impacting vortices acquire significant three-dimensional perturbations. Quasi-two-dimensional and fully three-dimensional computational results are compared to assess the accuracy of the quasi-two-dimensional approximation in prediction of drag and lift coefficients of the cylinders.

scholarly journals Quasi-two-dimensional approximation for numerical simulation of flows in engine ducts

2019 ◽  
Author(s):  
V. Vlasenko ◽  
A. Shiryaeva
Keyword(s):  
High Speed ◽  
Fuel Injection ◽  
Three Dimensional ◽  
Preliminary Design ◽  
Two Dimensional ◽  
Combustion Chambers ◽  
New Approach ◽  
One Dimensional ◽  
Dimensional Approximation ◽  
3D Flows

New quasi-two-dimensional (2.5D) approach to description of three-dimensional (3D) flows in ducts is proposed. It generalizes quasi-one-dimensional (quasi-1D, 1.5D) theories. Calculations are performed in the (x; y) plane, but variable width of duct in the z direction is taken into account. Derivation of 2.5D approximation equations is given. Tests for verification of 2.5D calculations are proposed. Parametrical 2.5D calculations of flow with hydrogen combustion in an elliptical combustor of a high-speed aircraft, investigated within HEXAFLY-INT international project, are described. Optimal scheme of fuel injection is found and explained. For one regime, 2.5D and 3D calculations are compared. The new approach is recommended for use during preliminary design of combustion chambers.

Corrugated SNOM probe with enhanced energy throughput

2008 ◽  
Vol 16 (4) ◽  
Author(s):  
T. Antosiewicz ◽  
T. Szoplik
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Energy Output ◽  
Dipolar Field ◽  
Two Dimensional ◽  
The Core ◽  
Dimensional Approximation ◽  
New Type ◽  
Difference Time ◽  
Main Factor

AbstractIn a previous paper we proposed a modification of metal-coated tapered-fibre aperture probes for scanning near-field optical microscopes (SNOMs). The modification consists in radial corrugations of the metal-dielectric interface oriented inward the core. Their purpose is to facilitate the excitation of surface plasmons, which increase the transport of energy beyond the cut-off diameter and radiate a quasi-dipolar field from the probe output rim. An increase in energy output allows for reduction of the apex diameter, which is the main factor determining the resolution of the microscope. In two-dimensional finite-difference time-domain (FDTD) simulations we analyse the performance of the new type of SNOM probe. We admit, however, that the two-dimensional approximation gives better results than expected from exact three-dimensional ones. Nevertheless, optimisation of enhanced energy throughput in corrugated probes should lead to at least twice better resolution with the same sensitivity of detectors available nowadays.

Two-Dimensional Oxides: Recent Progress in Nanosheets

2018 ◽  
Vol 233 (1) ◽  
pp. 117-165 ◽  
Author(s):  
Richard Hinterding ◽  
Armin Feldhoff
Keyword(s):  
Recent Progress ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Research Fields ◽  
Promising Application ◽  
Optical And Mechanical Properties ◽  
Application Fields ◽  
New Research ◽  
Novel Applications

Abstract Two-dimensional (2D) materials have been widely investigated for the last few years, introducing nanosheets and ultrathin films. The often superior electrical, optical and mechanical properties in contrast to their three-dimensional (3D) bulk counterparts offer a promising field of opportunities. Especially new research fields for already existing and novel applications are opened by downsizing and improving the materials at the same time. Some of the most promising application fields are namely supercapacitors, electrochromic devices, (bio-) chemical sensors, photovoltaic devices, thermoelectrics, (photo-) catalysts and membranes. The role of oxides in this field of materials deserves a closer look due to their availability, durability and further advantages. Here, recent progress in oxidic nanosheets is highlighted and the benefit of 2D oxides for applications discussed in-depth. Therefore, different synthesis techniques and microstructures are compared more closely.

scholarly journals A hierarchy of multilayered plate models

2020 ◽  
Author(s):  
Miguel de Benito Delgado ◽  
Bernd Schmidt
Keyword(s):  
Nonlinear Elasticity ◽  
Curvature Tensor ◽  
Elastic Constants ◽  
Three Dimensional ◽  
Spontaneous Curvature ◽  
Multilayered Plate ◽  
Von Karman ◽  
Plate Models ◽  
Γ Convergence ◽  
Von Kármán

We derive a hierarchy of plate theories for heterogeneous multilayers from three dimensional nonlinear elasticity by means of Γ-convergence. We allow for layers composed of different materials whose constitutive assumptions may vary significantly in the small film direction and which also may have a (small) pre-stress. By computing the Γ-limits in the energy regimes in which the scaling of the pre-stress is non-trivial, we arrive at linearised Kirchhoff, von Kármán, and fully linear plate theories, respectively, which contain an additional spontaneous curvature tensor. The effective (homogenised) elastic constants of the plates will turn out to be given in terms of the moments of the pointwise elastic constants of the materials.

scholarly journals Ion diffusion and acceleration in plasma turbulence

2018 ◽  
Vol 84 (6) ◽  
Author(s):  
F. Pecora ◽  
S. Servidio ◽  
A. Greco ◽  
W. H. Matthaeus ◽  
D. Burgess ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Three Dimensional ◽  
Theoretical Description ◽  
Two Dimensional ◽  
Ion Diffusion ◽  
Plasma Parameters ◽  
Laboratory Plasmas ◽  
Dimensional Approximation ◽  
Self Consistent ◽  
Particle Energization

Particle transport, acceleration and energization are phenomena of major importance for both space and laboratory plasmas. Despite years of study, an accurate theoretical description of these effects is still lacking. Validating models with self-consistent, kinetic simulations represents today a new challenge for the description of weakly collisional, turbulent plasmas. We perform simulations of steady state turbulence in the 2.5-dimensional approximation (three-dimensional fields that depend only on two-dimensional spatial directions). The chosen plasma parameters allow to span different systems, going from the solar corona to the solar wind, from the Earth’s magnetosheath to confinement devices. To describe the ion diffusion we adapted the nonlinear guiding centre (NLGC) theory to the two-dimensional case. Finally, we investigated the local influence of coherent structures on particle energization and acceleration: current sheets play an important role if the ions’ Larmor radii are of the order of the current sheet’s size. This resonance-like process leads to the violation of the magnetic moment conservation, eventually enhancing the velocity-space diffusion.

The Influence of a Free Surface on the Hydroelastic Stability of a Flat Panel

1972 ◽  
Vol 39 (1) ◽  
pp. 53-58 ◽  
Author(s):  
D. S. Weaver ◽  
T. E. Unny
Keyword(s):  
Free Surface ◽  
Three Dimensional ◽  
Surface Displacement ◽  
Two Dimensional ◽  
Flat Panel ◽  
Dimensional Solution ◽  
Dimensional Approximation ◽  
Free Surface Displacement

This paper examines the influence of a parallel free surface on the hydroelastic stability of a flat panel. A quasi-two-dimensional approximation is made for the free surface displacement and the results compared with the more general but cumbersome three-dimensional solution. This comparison shows that the former approach is quite reasonable as well as being considerably simpler and more instructive. It is found that the free surface has no effect for depth ratios greater than about one half and is stabilizing for smaller depth ratios.

Three-dimensional macro-structures of two-dimensional nanomaterials

2016 ◽  
Vol 45 (20) ◽  
pp. 5541-5588 ◽  
Author(s):  
Khurram Shehzad ◽  
Yang Xu ◽  
Chao Gao ◽  
Xiangfeng Duan
Keyword(s):  
Recent Progress ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Structure Properties

This review summarizes the recent progress and efforts in the synthesis, structure, properties, and applications of three-dimensional macro-structures of two-dimensional nanomaterials.

scholarly journals Mechanical Engineering in Ancient Egypt, Part 92: Tomb Inscription During the Old Kingdom

2020 ◽  
pp. 79-93
Author(s):  
Galal Ali Hassaan
Keyword(s):  
Atomic Orbital ◽  
Three Dimensional ◽  
Ancient Egypt ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Solid Matter ◽  
Old Kingdom ◽  
Dimensional Approximation ◽  
The Matrix ◽  
The Universe

This work is based on a previously published hypothesis which proposed that the solid matter of the universe can be represented as a vibrational wave of energy propagating over an ether or matrix through a mechanism that scrambles the degree of duality in matter: x% localized (solid), y% delocalized (wave). The main purpose of this paper is to present a two-dimensional approximation of the three-dimensional structure of the shape of the energy distribution of an atomic orbital to propose a mechanism through which the orbital can be transported as a vibration from a point A to point B in the matrix. This process requires cycles or oscillations of mounting-dismounting-remounting in which what travels from point A to point B is the energy forming the orbital and not the solid matter that it can form. The atomic seven-dimensional f orbital of hydrogen-like atoms is used as a model to show an analogy to the transformations that it can be submitted to when transported over the matrix.

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