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4 results on '"scale resolving simulation"'

1. Investigations into the Approaches of Computational Fluid Dynamics for Flow-Excited Resonator Helmholtz Modeling within Verification on a Laboratory Benchmark.

Author

Sergeev, Daniil, V'yushkina, Irina, Eremeev, Vladimir, Stulenkov, Andrei, and Pyalov, Kirill

Subjects
COMPUTATIONAL fluid dynamics, LARGE eddy simulation models, ORIFICE plates (Fluid dynamics), HELMHOLTZ resonators, AIR speed, WIND tunnels, AIR flow, FLUID mechanics
Abstract

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]

Published
2024
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2. Investigations into the Approaches of Computational Fluid Dynamics for Flow-Excited Resonator Helmholtz Modeling within Verification on a Laboratory Benchmark

Author

Daniil Sergeev, Irina V’yushkina, Vladimir Eremeev, Andrei Stulenkov, and Kirill Pyalov

Subjects
Helmholtz resonator, self-sustained oscillations, computational fluid mechanics, URANS, scale resolving simulation, resource greediness, Physics, QC1-999
Abstract

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.

Published
2023
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3. Entwicklung eines Modells zur Vorhersage stationärer Transitionsmechanismen in Niederdruckturbinen unter dem Einsatz von skalenauflösenden Simulationen

Author

Müller-Schindewolffs, Christoph

Subjects
Skalenauflösende Simulation, Scale Resolving Simulation, Reynolds-Averaged Navier-Stokes, Transition, Modeling, Modellierung, Dewey Decimal Classification::600 | Technik, ddc:600, Turbine
Abstract

Steady RANS simulations form the backbone of the aerodynamic turbomachinery design tool chain. They combine a fast response with the ability to describe three-dimensional geometries. However, they are based on approximations through modeling approaches. This is especially relevant for predicting boundary layer transition correctly which has a high impact on low-pressure turbine efficiency. Due to the high standard of modern low-pressure turbine efficiency, it is important to resolve complex three-dimensional geometries including small features accurately. This includes the appropriate transition prediction on airfoils and becomes increasingly relevant for endwalls as well. The transition prediction on these three-dimensional geometries requires locally formulated transition models, such as the γ-Reθ model. These models are required to be robust but also sensitive to environmental impacts, particularly in the two-dimensional mean flow. Within the present work, potentials of the established γ-Reθ model are presented and transferred to a reformulation of the model. This includes the consideration of further influencing parameters on the transition process and a more detailed modeling of transition phases. However, the essential improvement of the new model variant, called MSC2020, is a more precise determination of the pressure gradient parameter. This requires fundamental reformulation of model equations on the one hand, but it allows acquiring a more sensitively calibrated model that shows dynamic behavior with increased accuracy on the other hand. The model development is accompanied by an iLES study of the MTU-T161 low-pressure turbine cascade. Characteristic transitional structures are analyzed and brought into relation to the transition modeling by the MSC2020 model. As it turns out, the large amounts of turbulent kinetic energy predicted by the iLES do not agree with the modeled turbulence predicted by two-equation models. Only the turlulent energy resulting from the three-dimensional breakdown of the Kelvin-Helmholtz Instability can be related to modeled turbulence. The elaborated and calibrated model predicts transition on a variety of turbine and compressor cascades precisely which results in a significant improvement in comparison to the γ-Reθ reference model. This is also valid for turbine cascades that are operated far-off design point, where the model is robust and reliable. Besides the intention to improve the transition prediction within the two-dimensional flow regions, the loss prediction driven by secondary flows close to the endwalls of the MTU-T161 cascade is improved as well.

Published
2022

4. A contribution to turbulence modelling in bubbly flows

Author

Ma, T. and Ma, T.

Abstract

Modelling turbulence in bubbly flows that arise in the engineering and environment is of great challenges for multiphase Computational Fluid Dynamics. In the present book various turbulence modelling approaches are investigated in bubble columns and bubbly channel flows. The considered approaches contain Scale Resolving Simulations and the traditional Reynolds-averaged Navier-Stokes closure. The focus is set on the representation of the so-called bubble-induced turbulence in the modelling framework. A major chapter addresses a complete route to construct such a model embedded in Euler-Euler approach with the aid of Direct Numerical Simulation data. This procedure is employed to propose an improved model for bubble-induced turbulence.

Published
2017

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