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This paper presents the results of a study of self-sustained processes excited in a Helmholtz resonator after a flow over its orifice. A comparative analysis of various approaches to the numerical modeling of this problem was carried out, taking into account both the requirements for achieving the required accuracy and taking into account the resource greediness of calculations, the results of which were verified by comparison with data obtained during a special experiment. The configuration with a spherical resonator with a natural frequency of 260 Hz and an orifice diameter (about 5 cm) in an air flow with a speed of 6 to 14 m/s was considered. A comparison of the calculation results with data obtained in experiments carried out in the wind tunnel demonstrated that the accuracy of calculations of the characteristics of the self-sustained mode using the simplest URANS class model tends to the accuracy of calculations within the large eddy simulation approach formulated in the WMLES model. At the same time, when using WMLES, it is possible to better reproduce the background level of pulsations. From the point of view of resource greediness, expressed in the number of core hours spent obtaining a solution, both models of the turbulence turned out to be almost equivalent when using the same grid models. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of self-sustained processes excited in a Helmholtz resonator after a flow over its orifice. A comparative analysis of various approaches to the numerical modeling of this problem was carried out, taking into account both the requirements for achieving the required accuracy and taking into account the resource greediness of calculations, the results of which were verified by comparison with data obtained during a special experiment. The configuration with a spherical resonator with a natural frequency of 260 Hz and an orifice diameter (about 5 cm) in an air flow with a speed of 6 to 14 m/s was considered. A comparison of the calculation results with data obtained in experiments carried out in the wind tunnel demonstrated that the accuracy of calculations of the characteristics of the self-sustained mode using the simplest URANS class model tends to the accuracy of calculations within the large eddy simulation approach formulated in the WMLES model. At the same time, when using WMLES, it is possible to better reproduce the background level of pulsations. From the point of view of resource greediness, expressed in the number of core hours spent obtaining a solution, both models of the turbulence turned out to be almost equivalent when using the same grid models.

Abstract Turbulence modelling development has received a boost in recent years through assimilation of machine learning methods and increasing availability of high-fidelity datasets. This paper presents an approach that develops turbulence models for flows exhibiting organised unsteadiness. The novel framework consists of three parts. First, using triple decomposition, the high-fidelity data is split into organised motion and stochastic turbulence. A data-driven approach is then used to develop a closure only for the stochastic part of turbulence. Finally, unsteady calculations are conducted, which resolve the organised structures and model the unresolved turbulence using the developed bespoke turbulence closure. A case study of a wake with vortex shedding behind a normal flat plate, at a Reynolds number of 2,000, based on plate height and freestream velocity, is considered to demonstrate the method. The approach shows significant improvement in mean velocity and Reynold stress profiles compared with standard turbulence models. Highlights • A novel machine-learnt framework for flows with organised unsteadiness. • Turbulence closure developed from DNS data for the stochastic part of the anisotropy. • Gene-Expression Programming used to develop mathematical expression for anisotropy. • Developed model reveals turbulence diffusion needs to be significantly reduced. • Closures used in URANS and PANS show significant improvement of results for a wake. [ABSTRACT FROM AUTHOR]

The accuracy of a recently developed one-equation turbulence model in predicting complex flows with massive separation is assessed against the well-known Spalart Allmaras (SA) and the k-ω-SST-Scale Adaptive Simulation (SAS) models. The unsteady 3-D flow past a square cylinder at Re =2.2×10 4 , as well as a 3-D flow over a wall-mounted cube at Re =4.0×10 4 are computed and compared to available experimental data. The recently developed model is capable of resolving turbulent flow structures, thereby predicting all major unsteady phenomena with a marked improvement over other Reynolds average Navier–Stokes (RANS) models. The computational time required by the model in comparison to that required by Large Eddy Simulation (LES) renders it a suitable candidate for simulating 3D unsteady complex engineering flows such as building aerodynamics with reasonable accuracy. [ABSTRACT FROM AUTHOR]