Scientific Visualization, 2018, volume 10, number 2, pages 1 - 14, DOI: 10.26583/sv.10.2.01
Visualization tools for the numerical modeling in the reference experiment on the flow over a rectangular obstacle
Authors: D.A. Sergeev1, O.S. Ermakova2, A.S. Suvorov3, Y.I. Troitskaya4, A.A. Kandaurov5, A.I. Konkov6
Institute of Applied Physics RAS, Nizhny Novgorod
1 ORCID: 0000-0003-4910-3935
2 ORCID: 0000-0003-0687-4000, ermakova@hydro.appl.sci-nnov.ru
3 ORCID: 0000-0003-2277-7497
4 ORCID: 0000-0002-3818-9211
5 ORCID: 0000-0002-0014-8887
6 ORCID: 0000-0001-8822-8277
Abstract
A number of demonstration experiments on the study of the structure of the air flow over a rectangular obstacle, based on a combined approach using PIV method to restore the overall picture of an air flow over an obstacle, and its verification on the basis of numerical calculations. As a result of research carried out on the basis of PIV method, it was found that the air flow can be conditionally divided into regions, reflecting qualitatively its typical features: the origin of the formation of the separation, the separation region of maximum vertical scale and flow joining region. A step by step verification of the results of numerical simulations with the ANSYS FLUENT application based on the results of experimental measurements of the spectral characteristics of turbulent fluctuations were carried out. A selection of the optimal numerical scheme for reproducing the experimentally observed flow patterns included calculations based on SAS (Scale Adaptive Simulation) turbulence model and DES turbulence model, with the central scheme of numerical differentiation. Using SAS turbulence model has led to a distortion of the qualitative picture of flow, namely to the emergence of a false separation of the boundary layer, the characteristic frequencies in the spectrum of velocity fluctuations were much too high. Presumably the correct calculations made in the framework of SAS turbulence model are impossible due to the use of a highly anisotropic (elongated in the direction perpendicular to the main flow) computational grid. Comparison of numerical calculations with experimental results have shown that the physical process of the flow over an obstacle can be optimally modeled in a three-dimensional formulation using DES turbulence model with the scheme of central numerical differentiation.
Keywords: turbulence, air boundary layer, flow separation, turbulent flow, numerical simulation of turbulence.
