TY - JOUR

T1 - Experimental Analysis of Multiscale Vortex Shedding in Turbulent Turbomachine Blade Wakes

AU - Gilge, P.

AU - Seume, J. R.

AU - Mulleners, K.

N1 - Funding Information: This work has been conducted within the framework of subproject B3 entitled “Influence of Complex Surface Structures on the Aerodynamic Loss Behavior of Blades” of Collaborative Research Center 871 titled “Regeneration of Complex Capital Goods,” which is funded by the DFG, German Research Foundation (SFB 871/3–119193472). The authors thank the IP@Leibniz-Program, funded by the German Academic Exchange Service and the Federal Ministry of Education and Research, for supporting the research stay of Philipp Gilge at the Federal Institute of Technology Lausanne, during which the presented work was shaped.

PY - 2020/12

Y1 - 2020/12

N2 - Wakes behind turbomachine blades are generally highly turbulent and seemingly chaotic. Within the apparent chaos, coherent structures of various strength and length scales are present that are challenging to identify within individual snapshots of the wake flowfield. We propose a strategy to identify and separate multiscale vortices in the turbulent wake of a turbomachine blade from experimental data. Uncorrelated velocity field snapshots were obtained in the wake of a compressor blade in a linear cascade wind tunnel at Reynolds number 7 × 105 using particle image velocimetry. The snapshots were analyzed using proper orthogonal decomposition to identify the most energetic mode pairs representing vortex shedding patterns of different length scales with their own shedding frequency. The phase angles associated with the individual shedding patterns are extracted for each snapshot based on the time coefficients of the mode pairs. By averaging snapshots with the same phase angle for selected mode pairs, we were able to calculate mode-or scale-dependent phase average flowfields. These scale-dependent phase averages visually highlight the multiscale vortex character of the turbulent wake and allow for a quantitative analysis of the size, emerging location, and shedding frequency of the different structures.

AB - Wakes behind turbomachine blades are generally highly turbulent and seemingly chaotic. Within the apparent chaos, coherent structures of various strength and length scales are present that are challenging to identify within individual snapshots of the wake flowfield. We propose a strategy to identify and separate multiscale vortices in the turbulent wake of a turbomachine blade from experimental data. Uncorrelated velocity field snapshots were obtained in the wake of a compressor blade in a linear cascade wind tunnel at Reynolds number 7 × 105 using particle image velocimetry. The snapshots were analyzed using proper orthogonal decomposition to identify the most energetic mode pairs representing vortex shedding patterns of different length scales with their own shedding frequency. The phase angles associated with the individual shedding patterns are extracted for each snapshot based on the time coefficients of the mode pairs. By averaging snapshots with the same phase angle for selected mode pairs, we were able to calculate mode-or scale-dependent phase average flowfields. These scale-dependent phase averages visually highlight the multiscale vortex character of the turbulent wake and allow for a quantitative analysis of the size, emerging location, and shedding frequency of the different structures.

UR - http://www.scopus.com/inward/record.url?scp=85097649854&partnerID=8YFLogxK

U2 - 10.2514/1.J059476

DO - 10.2514/1.J059476

M3 - Article

AN - SCOPUS:85097649854

VL - 58

SP - 5183

EP - 5190

JO - AIAA journal

JF - AIAA journal

SN - 0001-1452

IS - 12

ER -