scholarly journals Vortical flow calculations using a high-order Vorticity Confinement method

2017 ◽  
Author(s):  
Ilias Petropoulos ◽  
Michel Costes ◽  
Paola Cinnella
Keyword(s):  
High Order ◽  
Vortical Flow ◽  
Vorticity Confinement

On Coarse Grids Simulation of Compressible Mixing Layer Flows Using Vorticity Confinement

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
K. Hejranfar ◽  
M. Ebrahimi ◽  
M. Sadri
Keyword(s):  
Reynolds Number ◽  
Mixing Layer ◽  
Viscosity Coefficient ◽  
Sensitivity Study ◽  
High Order ◽  
Vortex Identification ◽  
Compressible Mixing Layer ◽  
Vorticity Confinement ◽  
Mixing Layer Flows ◽  
Coarse Grids

In this work, the capability and performance of the vorticity confinement (VC) implemented in a high-order accurate flow solver in predicting two-dimensional (2D) compressible mixing layer flows on coarse grids are investigated. Here, the system of governing equations with incorporation of the VC in the formulation is numerically solved by the fourth-order compact finite difference scheme. To stabilize the numerical solution, a low-pass high-order filter is applied, and the nonreflective boundary conditions are used at the farfield and outflow boundaries to minimize the reflections. At first, the numerical results without applying the VC are validated by available direct numerical simulations (DNSs) for a low Reynolds number mixing layer. Then, the calculations using a range of VC levels are performed for a high Reynolds number mixing layer and the results are thoroughly compared with those of available large eddy simulations (LESs). The study shows that, with applying the vortex identification method, more accurate results are obtained in the slow laminar region of the mixing layer. A sensitivity study is also performed to examine the effect of different numerical parameters to reasonably provide more accurate results. It is shown that the local VC introduced based on the artificial viscosity coefficient and the vorticity thickness can improve the accuracy of the results in the turbulent region of the mixing layer compared with those of LESs. It is found that the solution methodology proposed can reasonably preserve the vortices in the flowfield and the results are comparable with those of LESs on fairly coarser grids and thus the computational costs can be considerably decreased.

A Numerical Study on Fluid Flow and Acoustic Characteristics of a Supersonic Impinging Jet Using Vorticity Confinement

2019 ◽  
Vol 105 (6) ◽  
pp. 1127-1136
Author(s):  
M. Sadri ◽  
K. Hejranfar ◽  
M. Ebrahimi
Keyword(s):  
Fluid Flow ◽  
Finite Difference ◽  
Difference Scheme ◽  
Acoustic Field ◽  
Finite Difference Scheme ◽  
High Order ◽  
Compact Finite Difference Scheme ◽  
Compact Finite Difference ◽  
Vorticity Confinement ◽  
Supersonic Impinging Jet

The objective of this work is to numerically study the fluid flow and acoustic field of a supersonic impinging jet by applying the vorticity confinement (VC) method. For this aim, the three-dimensional compressible Navier-Stokes equations with the incorporation of the VC method are considered and the resulting system of equations is solved by using the sixth-order compact finite-difference scheme. To eliminate the numerical instability, a low-pass high-order filter is used. The nonreflective boundary conditions are applied for all the free boundaries and the radiated sound field is obtained by the Kirchhoff surface integration. Comparisons of the present results with the experimental data and other numerical simulations show that the solution methodology adopted based on the application of the VC method with the high-order compact finite-difference scheme provides a good prediction of the fluid flow and the acoustic field of the impingement region on coarser grids than that usually required in the LESs, and thus, the calculations of coarse grid LESs are improved.

scholarly journals Development and analysis of high-order vorticity confinement schemes

2017 ◽  
Vol 156 ◽  
pp. 602-620 ◽  
Author(s):  
I. Petropoulos ◽  
M. Costes ◽  
P. Cinnella
Keyword(s):  
High Order ◽  
Vorticity Confinement

On the Accurate Prediction of Tip Vortex: Effect of Numerical Schemes

2013 ◽  
Author(s):  
Xinrong Su ◽  
Satoru Yamamoto ◽  
Xin Yuan
Keyword(s):  
Numerical Methods ◽  
Numerical Scheme ◽  
High Order ◽  
Accurate Prediction ◽  
Upwind Scheme ◽  
Tip Vortex ◽  
Vortical Flow ◽  
Order Scheme ◽  
Central Scheme ◽  
Low Order

This work is conducted towards the accurate prediction of compressor tip vortex. Accurate computation of highly vortical flow is affected by many parameters, such as numerical scheme and turbulence model. In this work the effect of numerical scheme is studied using mesh refinement study and comparison of numerical results from central scheme and a newly developed high order upwind scheme. Behaviors of numerical methods in the tip vortex region are also theoretically and numerically analyzed. It is found the computed tip vortex is significantly affected by mesh resolution and numerical dissipation. Currently widely numerical strategy, i.e., mesh with moderate resolution and low order scheme would yield quite inaccurate result. Predicted tip vortex is always dissipated earlier and this highlights the advantage of high order scheme in predicting detailed flow features. Besides coarser mesh and low order method, analysis of numerical methods reveals a new finding, in that the designed order of accuracy is not guaranteed in the tip vortex region. For central scheme pressure based shock sensor is unnecessarily activated and excessive artificial dissipation is added. For high order upwind scheme it tends to use low order reconstruction and new method considering flow physics shows its improved vortex prediction capability. Conclusions from this work can be used in future numerical studies about tip vortex to improve the numerical accuracy.

High-Order Computational Techniques for Unsteady Vortical Flows Over Delta Wings

2006 ◽  
Author(s):  
Raymond E. Gordnier ◽  
Miguel R. Visbal
Keyword(s):  
Difference Scheme ◽  
Delta Wing ◽  
High Order ◽  
Vortical Flow ◽  
Compact Difference Scheme ◽  
Delta Wings ◽  
Vortical Flows ◽  
Compact Difference ◽  
Moderate Reynolds Number ◽  
The Impact

A high-order computational method for the highly unsteady, complex vortical flows over delta wings is presented. A sixth-order compact difference scheme with an eighth-order low pass filter is used to solve the Navier-Stokes equations. Two approaches to turbulence modeling are investigated. The first scheme is an implicit LES (ILES) method which exploits the high-order accuracy of the compact difference scheme and uses the discriminating higher-order filter to regularize the flow. The second approach is a new hybrid RANS/ILES method which employs a standard k–ε model in regions where the grid resolution is unable to capture the turbulent behavior, and transitions to the ILES method in the vortical flow region where large scale turbulent structures are resolved. Computational simulations have been performed for a 50° sweep delta wing at 15° angle of attack and a moderate Reynolds number, Re = 2 × 106. Solutions employing the two turbulence models are evaluated on a baseline grid. A fine mesh computation has been performed for the ILES approach to investigate the impact of mesh resolution on this scheme. Computed results are also compared with the limited experimental measurements available. Computations exploring the control of the vortical flows above a swept delta wing by use of a dialectric-barrier-discharge actuator are also presented. With the actuator located near the apex, significant movement of the vortex breakdown location and a dramatic transformation of the shear-layer sub-structures are demonstrated.

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