Spectral proper orthogonal decomposition of compressor tip leakage flow

He, Xiao; Zhou, Fang; Rigas, Georgios; Vahdati, Mehdi

doi:10.1063/5.0065929

Cited by 59 publications

(10 citation statements)

References 40 publications

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“…In extracting the main flow field fluctuations and understanding the flow mechanism, the data-driven mode decomposition method performs well, with visual mode structure inspections often directly revealing the underlying flow physics; for example, vortex interactions, vortex shedding, flow instabilities, and so on [39]. The core part of the SPOD program refers to the literature [40]. Compared with the traditional proper orthogonal decomposition (POD) method, SPOD can extract the physical modes of a specific frequency band in an energy mode while obtaining all the modes arranged in descending order of energy, taking into account the frequency domain information of the flow field.…”

Section: Spectral Proper Orthogonal Decomposition (Spod)mentioning

confidence: 99%

Accuracy Investigations of Dynamic Characteristic Predictions of Tip Leakage Flow Using Detached Eddy Simulation

Lin,

Li,

Gao

et al. 2023

Aerospace

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The accurate prediction of tip leakage flow is the premise for flow mechanism analysis and compressor performance optimization. The detached eddy simulation (DES) method, which compromises cost and accuracy, has excellent potential for a high Reynolds flow, like a compressor.However, in the case of tip leakage flow, especially when there are multiple wall boundary layers and strong shear between the mainstream and leakage flow, the DES method exhibits accuracy deficiencies. This paper explores the resolution of the critical detailed structures using the DES method and its correlation with the accuracy of time-averaged aerodynamic parameter predictions. Based on this, we propose the necessary conditions for the DES method to accurately predict the leakage flow from the perspective of the detailed structure of the flow field. A simplified model is proposed to emphasize the characteristics of tip leakage flow with “multiple walls + narrow tip gap”, and the high-fidelity flow field of the WALE LES method is used as a benchmark. With the main fluctuation structures obtained by the SPOD method, it is concluded that the DES method is unable to resolve the Kelvin–Helmholtz instability at the initial position of the leakage, which leads to the generation of the secondary leakage vortex upstream of the leakage and the breakdown of the induced vortex, two critical flow structures, being incorrectly estimated. This can lead to misestimationsof the force direction on the tip leakage vortex and the main fluctuation on the flow field. As a result, the tip leakage vortex trajectory evolves toward the middle of the passage along the tangential direction and away from the upper wall downstream of the leakage compared with the LES results. Predictions of losses in the upstream and midstream regions are underestimated, whereas they are overestimated downstream of the leakage and outside the passage.Therefore, the accurate resolution of these two critical detailed structures is an essential prerequisite for the precise prediction of tip leakage flow using DES series methods.

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Section: Spectral Proper Orthogonal Decomposition (Spod)mentioning

confidence: 99%

Accuracy Investigations of Dynamic Characteristic Predictions of Tip Leakage Flow Using Detached Eddy Simulation

Lin,

Li,

Gao

et al. 2023

Aerospace

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“…The detached eddy simulation (DES) method [ 18 ] in scale-resolving simulations, which combines the advantages of the RANS and LES methods, can help reduce the consumption of computing resources. While this method has been successfully used to locate aerodynamic loss in blades [ 19 , 20 , 21 ], it has rarely been applied to the study of aerodynamic loss in CRF blade passages.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study on Local Entropy Production Mechanism of a Contra-Rotating Fan

Jia,

Zhang

2023

Entropy

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Contra-rotating fans (CRFs) have garnered significant attention due to their higher power-to-weight ratio compared to traditional fans; however, limited focus has been given to the localization and development of local aerodynamic losses. Furthermore, there is a need for further research on the impact of load distribution along the radius on local entropy production. Therefore, this study aims to investigate a contra-rotating fan as the research subject. An optimal design for load distribution along the radius is achieved by constructing a surrogate model in combination with a genetic algorithm. The effectiveness of this design has been verified through experimentation using a specific test device. In this study, a local entropy production rate (EPR) model adapted to the shear stress transport-detached eddy simulation (SST-DES) technique is constructed to evaluate the loss distribution of the contra-rotating fan. This paper primarily focuses on comparing and analyzing the blade profile and overall performance of the CRFs before and after optimization. The EPR contribution of each interval along the radius is compared to the corresponding blade channel to identify the approximate range of high-EPR regions. Furthermore, an investigation is conducted to examine the distribution of EPR along the streamwise direction in these high-EPR regions. After that, by comparing the development of the flow structure near a stall before and after optimization, combined with the analysis of the EPR contours, the EPR mechanism of this CRF is revealed.

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“…Later works employing SPOD include: the development of data-driven ROMs for boundary layer transition control (Sasaki et al 2020), characterisation of noise generated over airfoils (Sano et al 2019;Abreu et al 2021) and the identification of coherent structures in channels (Abreu et al 2020a), wakes (Nidhan et al 2020;Li et al 2021), separated high-speed flows (Lugrin et al 2021) and complex geometries (Zhang, Ooka & Kikumoto 2021;He et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Improved convergence of the spectral proper orthogonal decomposition through time shifting

Blanco

Martini²,

Sasaki³

et al. 2022

J. Fluid Mech.

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Spectral proper orthogonal decomposition (SPOD) is an increasingly popular modal analysis method in the field of fluid dynamics due to its specific properties: a linear system forced with white noise should have SPOD modes identical to response modes from resolvent analysis. The SPOD, coupled with the Welch method for spectral estimation, may require long time-resolved datasets. In this work, a linearised Ginzburg–Landau model is considered in order to study the method's convergence. Spectral proper orthogonal decomposition modes of the white-noise forced equation are computed and compared with corresponding response resolvent modes. The quantified error is shown to be related to the time length of Welch blocks (spectral window size) normalised by a convective time. Subsequently, an algorithm based on a temporal data shift is devised to further improve SPOD convergence and is applied to the Ginzburg–Landau system. Next, its efficacy is demonstrated in a numerical database of a boundary layer subject to bypass transition. The proposed approach achieves substantial improvement in mode convergence with smaller spectral window sizes with respect to the standard method. Furthermore, SPOD modes display growing wall-normal and spanwise velocity components along the streamwise direction, a feature which had not yet been observed and is also predicted by a global resolvent calculation. The shifting algorithm for the SPOD opens the possibility for using the method on datasets with time series of moderate duration, often produced by large simulations.

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Spectral proper orthogonal decomposition of compressor tip leakage flow

Cited by 59 publications

References 40 publications

Accuracy Investigations of Dynamic Characteristic Predictions of Tip Leakage Flow Using Detached Eddy Simulation

Accuracy Investigations of Dynamic Characteristic Predictions of Tip Leakage Flow Using Detached Eddy Simulation

Numerical Study on Local Entropy Production Mechanism of a Contra-Rotating Fan

Improved convergence of the spectral proper orthogonal decomposition through time shifting

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