Double shear layer evolution on the non-uniform computational mesh

2021 ◽  
Author(s):  
Yu M. Kulikov ◽  
E. E. Son
Keyword(s):  
Shear Layer ◽  
Iterative Refinement ◽  
The Novel ◽  
Original Sequence ◽  
Double Shear ◽  
Computational Mesh ◽  
Mesh Resolution ◽  
Initial Vorticity ◽  
High Resolution Technique ◽  
Refinement Algorithm

Abstract This paper considers the canonical problem of a thin shear layer evolution at Reynolds number Re = 400000 using the novel Compact Accurately Boundary Adjusting high-Resolution Technique (CABARET). The study is focused on the effect of the specific mesh refinement in the high shear rate areas on the flow properties under the influence of the developing instability. The original sequence of computational meshes (256^2, 512^2, 1024^2, 2048^2 cells) is modified using an iterative refinement algorithm based on the hyperbolic tangent. The properties of the solutions obtained are discussed in terms of the initial momentum thickness and the initial vorticity thickness, viscous and dilatational dissipation rates and also integral enstrophy. The growth rate for the most unstable mode depending on the mesh resolution is considered. In conclusion the accuracy of calculated mesh functions is estimated via L1, L2, L∞ norms.

scholarly journals Effects of a Curved Trailing Edge on Growth of a Compressible Shear Layer-Comparison between Single and Double Shear Layers-

2005 ◽  
Vol 53 (620) ◽  
pp. 408-413
Author(s):  
Mikiya Araki ◽  
Jun Osaka ◽  
Osamu Imamura ◽  
Mitsuhiro Tsue ◽  
Michikata Kono
Keyword(s):  
Shear Layer ◽  
Shear Layers ◽  
Trailing Edge ◽  
Double Shear

scholarly journals Effects of Streamwise Vortex Inducement on Growth of a Compressible Double Shear Layer

2005 ◽  
Vol 53 (615) ◽  
pp. 174-181 ◽  
Author(s):  
Mikiya Araki ◽  
Jun Osaka ◽  
Osamu Imamura ◽  
Mitsuhiro Tsue ◽  
Michikata Kono
Keyword(s):  
Shear Layer ◽  
Streamwise Vortex ◽  
Double Shear

An Iterative Refinement Algorithm for the Minimum Branch Vertices Problem

2011 ◽  
pp. 421-433 ◽  
Author(s):  
Diego M. Silva ◽  
Ricardo M. A. Silva ◽  
Geraldo R. Mateus ◽  
José F. Gonçalves ◽  
Mauricio G. C. Resende ◽  
...  
Keyword(s):  
Iterative Refinement ◽  
Refinement Algorithm

Research on the Repeater Optimization Based on Voronoi Model

2012 ◽  
Vol 588-589 ◽  
pp. 802-805
Author(s):  
Ban Teng Liu ◽  
Xi Lin Hu ◽  
Zheng Yu Xu ◽  
Yao Lin Liu ◽  
You Rong Chen
Keyword(s):  
Cellular Networks ◽  
Voronoi Diagram ◽  
Iterative Refinement ◽  
Local Optimum ◽  
Limited Capacity ◽  
Circular Area ◽  
Absolute Minimum ◽  
Voronoi Regions ◽  
Refinement Algorithm ◽  
Better Than

This paper propose a two-tiered network in which lower-power users communicate with one another through repeaters, which amplify signals and retransmit them, have limited capacity, and may interfere with one another if their transmitter frequencies are close and they share the same private-line tone. Motivated by cellular networks, this paper gives a naive solution where the number of repeaters and their positions can be obtained analytically. In a circular area with radius 40 miles, 12 repeaters can accommodate 1,000 simultaneous users. This paper further propose an iterative refinement algorithm consisting of three fundamental modules that draw the Voronoi diagram, determine the centers of the circumscribed circles of the Voronoi regions, and escape the local optimum by using external optimization. The algorithm obtains a solution with 11 repeaters, which we prove to be the absolute minimum. For 10,000 users, it uses 104 repeaters, better than the naive solution's 108.

Final equilibrium state of a two-dimensional shear layer

1991 ◽  
Vol 233 ◽  
pp. 661-689 ◽  
Author(s):  
J. Sommeria ◽  
C. Staquet ◽  
R. Robert
Keyword(s):  
Equilibrium State ◽  
Shear Layer ◽  
Stream Function ◽  
Stokes Equations ◽  
Local Equilibrium ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Final Equilibrium State ◽  
Initial Vorticity ◽  
Pseudo Spectral Method

We test a new statistical theory of organized structures in two-dimensional turbulence by direct numerical stimulations of the Navier–Stokes equations, using a pseudo-spectral method. We apply the theory to the final equilibrium state of a shear layer evolving from a band of uniform vorticity: a relationship between vorticity and stream function is predicted by maximizing an entropy with the constraints due the constants of the motion. A partial differential equation for the stream function is then obtained. In the particular case of a very thin initial vorticity band, the Stuart's vortices appear to be a family of solutions for this equation. In more general cases we do not solve the equation, but we test the theory by inspecting the relationship between stream function and vorticity in the final equilibrium state of the numerical computation. An excellent agreement is obtained in regions with strong vorticity mixing. However, local equilibrium is obtained before a complete mixing can occur in the whole fluid domain.

scholarly journals ACCURATE OPTICAL TARGET POSE DETERMINATION FOR APPLICATIONS IN AERIAL PHOTOGRAMMETRY

2016 ◽  
Vol III-3 ◽  
pp. 257-262 ◽  
Author(s):  
D. A. Cucci
Keyword(s):  
Target Position ◽  
Iterative Refinement ◽  
Target Size ◽  
Geometric Invariant ◽  
Pose Determination ◽  
Aerial Photogrammetry ◽  
Circle Center ◽  
Position And Orientation ◽  
Orientation Determination ◽  
Refinement Algorithm

We propose a new design for an optical coded target based on concentric circles and a position and orientation determination algorithm optimized for high distances compared to the target size. If two ellipses are fitted on the edge pixels corresponding to the outer and inner circles, quasi-analytical methods are known to obtain the coordinates of the projection of the circles center. We show the limits of these methods for quasi-frontal target orientations and in presence of noise and we propose an iterative refinement algorithm based on a geometric invariant. Next, we introduce a closed form, computationally inexpensive, solution to obtain the target position and orientation given the projected circle center and the parameters of the outer circle projection. The viability of the approach is demonstrated based on aerial pictures taken by an UAV from elevations between 10 to 100 m. We obtain a distance RMS below 0.25 % under 50 m and below 1 % under 100 m with a target size of 90 cm, part of which is a deterministic bias introduced by image exposure.

scholarly journals ACCURATE OPTICAL TARGET POSE DETERMINATION FOR APPLICATIONS IN AERIAL PHOTOGRAMMETRY

2016 ◽  
Vol III-3 ◽  
pp. 257-262 ◽  
Author(s):  
D. A. Cucci
Keyword(s):  
Target Position ◽  
Iterative Refinement ◽  
Target Size ◽  
Geometric Invariant ◽  
Pose Determination ◽  
Aerial Photogrammetry ◽  
Circle Center ◽  
Position And Orientation ◽  
Orientation Determination ◽  
Refinement Algorithm

We propose a new design for an optical coded target based on concentric circles and a position and orientation determination algorithm optimized for high distances compared to the target size. If two ellipses are fitted on the edge pixels corresponding to the outer and inner circles, quasi-analytical methods are known to obtain the coordinates of the projection of the circles center. We show the limits of these methods for quasi-frontal target orientations and in presence of noise and we propose an iterative refinement algorithm based on a geometric invariant. Next, we introduce a closed form, computationally inexpensive, solution to obtain the target position and orientation given the projected circle center and the parameters of the outer circle projection. The viability of the approach is demonstrated based on aerial pictures taken by an UAV from elevations between 10 to 100 m. We obtain a distance RMS below 0.25 % under 50 m and below 1 % under 100 m with a target size of 90 cm, part of which is a deterministic bias introduced by image exposure.

scholarly journals Effects of Spanwise Vortex Contortion on the Growth of Supersonic Double Shear Layer.

2000 ◽  
Vol 48 (556) ◽  
pp. 148-154 ◽  
Author(s):  
Mikiya ARAKI ◽  
Motoki HARADA ◽  
Yuichi OGURA ◽  
Seiji SHIBA ◽  
Keiichi OKAI ◽  
...  
Keyword(s):  
Shear Layer ◽  
Double Shear ◽  
Spanwise Vortex

Modelling Impingement-Effusion Flow Inside Double-Walled Combustor Tile

2017 ◽  
Author(s):  
Dalila Ammour ◽  
Gary J. Page
Keyword(s):  
Heat Transfer ◽  
Solid Material ◽  
Cfd Modelling ◽  
Eddy Simulation ◽  
Computational Mesh ◽  
Mesh Resolution ◽  
Flow Curvature ◽  
The Difference ◽  
Sas Model ◽  
Good Agreement

The prediction of temperature and heat transfer throughout the solid material of a gas-turbine combustor has driven interest in cooling technology which uses impingement/effusion (IE) cooling tiles on double-skinned combustor liners. The design of the IE tile system is simple but the aerodynamics are complex. The complexity of flow curvature, combined impingement and effusion cooling and heat transfer, poses a challenge to standard RANS CFD modelling. The IE combustor tile is numerically investigated using both URANS model with the SST-SAS model and Large Eddy Simulation (LES) in the Rolls-Royce in-house CFD code. The aim is to provide accurate CFD data and to test the viability of URANS approach to predict the impingement/effusion flow. Results of pressure, velocity and turbulence quantities are presented. It is found that the SST-SAS model, with high grid resolution, shows good agreement with LES. The current CFD results are used to resolve a substantial amount of very small impingement and effusion holes. The CFD results showed that every feature of the geometry has to be resolved by the numerical mesh, which makes the simulation impractical due to time consuming and high mesh resolution. These cooling holes can be omitted from the computational mesh and their effects captured on the flow via an impingement-effusion (IE) model which is based on defining the correct mass flow inside the holes as a function of the difference of pressure in the upstream and downstream regions of both impingement and effusion regions. The latter model takes the effect of pressure and velocity and it will be extended in future to take into account the heat transfer effects. The IE model is tested and validated for the 3-D combusor tile and results of pressure showed good agreement with the LES data.

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