On the Application of Background Oriented Schlieren to a Transonic Low-Reynolds Turbine Cascade
Halby, Alexandre ; Çakir, Bora Orçun LU
; Da Valle, Lorenzo
; Lopes, Gustavo
; Okada, Mizuki
and Lavagnoli, Sergio
(2024)
ASME Turbo Expo 2024: Power for Land, Sea and Air
4.
- Abstract
- Qualitative and quantitative visualizations of transonic turbomachinery flows provide essential information on compressibility and Mach number effects on boundary layer development, shock-boundary layer interactions (SBLI) and trailing edge flows. Background Oriented Schlieren (BOS) is a relatively new optical technique that allows capturing unsteady density gradient fields through turbomachinery cascades and thus, quantitative experimental data to validate transonic and supersonic blade designs. However, only very few experimental works in the open literature have successfully applied Background Oriented Schlieren (BOS) to transonic turbine or compressor flows. The current study presents the application of BOS to a transonic low pressure... (More)
- Qualitative and quantitative visualizations of transonic turbomachinery flows provide essential information on compressibility and Mach number effects on boundary layer development, shock-boundary layer interactions (SBLI) and trailing edge flows. Background Oriented Schlieren (BOS) is a relatively new optical technique that allows capturing unsteady density gradient fields through turbomachinery cascades and thus, quantitative experimental data to validate transonic and supersonic blade designs. However, only very few experimental works in the open literature have successfully applied Background Oriented Schlieren (BOS) to transonic turbine or compressor flows. The current study presents the application of BOS to a transonic low pressure turbine cascade, the VKI SPLEEN C1 cascade for a range of Reynolds numbers (70,000 to 140,000) and transonic Mach numbers (0.90 to 1.00). The linear turbine cascade is tested at the von Karman Institute in the S-1/C high-speed wind tunnel. The test section is instrumented with different BOS optical setups to visualize the time-resolved density gradients through the turbine passage and at the trailing edge plane with dedicated field of views. The BOS images are processed using the classical cross-correlation algorithm, and the optical flow approach, recently introduced in BOS applications to gain spatial resolution and increased sensitivity. Steady-state density gradients of the cascade flow characterize the airfoil boundary layers, wakes and shock waves. The results from the two data reduction methods are assessed and compared against available RANS CFD predictions. Time-resolved measurements reveals the low-frequency motion of weak shock waves generated in the blade passage using POD and spectra analysis. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/12fd1070-5afa-4e2e-86c4-d434f2744e95
- author
- Halby, Alexandre
; Çakir, Bora Orçun
LU
; Da Valle, Lorenzo
; Lopes, Gustavo
; Okada, Mizuki
and Lavagnoli, Sergio
- publishing date
- 2024-08-28
- type
- Chapter in Book/Report/Conference proceeding
- publication status
- published
- subject
- host publication
- ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition : June 24–28, 2024 London, United Kingdom - June 24–28, 2024 London, United Kingdom
- volume
- 4
- pages
- 12 pages
- conference name
- ASME Turbo Expo 2024: Power for Land, Sea and Air
- conference location
- London, United Kingdom
- conference dates
- 2024-06-24 - 2024-06-28
- external identifiers
-
- scopus:85204304518
- ISBN
- 978-0-7918-8796-7
- DOI
- 10.1115/GT2024-127971
- language
- English
- LU publication?
- no
- id
- 12fd1070-5afa-4e2e-86c4-d434f2744e95
- date added to LUP
- 2024-09-23 09:38:46
- date last changed
- 2025-04-04 15:00:54
@inproceedings{12fd1070-5afa-4e2e-86c4-d434f2744e95,
abstract = {{Qualitative and quantitative visualizations of transonic turbomachinery flows provide essential information on compressibility and Mach number effects on boundary layer development, shock-boundary layer interactions (SBLI) and trailing edge flows. Background Oriented Schlieren (BOS) is a relatively new optical technique that allows capturing unsteady density gradient fields through turbomachinery cascades and thus, quantitative experimental data to validate transonic and supersonic blade designs. However, only very few experimental works in the open literature have successfully applied Background Oriented Schlieren (BOS) to transonic turbine or compressor flows. The current study presents the application of BOS to a transonic low pressure turbine cascade, the VKI SPLEEN C1 cascade for a range of Reynolds numbers (70,000 to 140,000) and transonic Mach numbers (0.90 to 1.00). The linear turbine cascade is tested at the von Karman Institute in the S-1/C high-speed wind tunnel. The test section is instrumented with different BOS optical setups to visualize the time-resolved density gradients through the turbine passage and at the trailing edge plane with dedicated field of views. The BOS images are processed using the classical cross-correlation algorithm, and the optical flow approach, recently introduced in BOS applications to gain spatial resolution and increased sensitivity. Steady-state density gradients of the cascade flow characterize the airfoil boundary layers, wakes and shock waves. The results from the two data reduction methods are assessed and compared against available RANS CFD predictions. Time-resolved measurements reveals the low-frequency motion of weak shock waves generated in the blade passage using POD and spectra analysis.}},
author = {{Halby, Alexandre and Çakir, Bora Orçun and Da Valle, Lorenzo and Lopes, Gustavo and Okada, Mizuki and Lavagnoli, Sergio}},
booktitle = {{ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition : June 24–28, 2024 London, United Kingdom}},
isbn = {{978-0-7918-8796-7}},
language = {{eng}},
month = {{08}},
title = {{On the Application of Background Oriented Schlieren to a Transonic Low-Reynolds Turbine Cascade}},
url = {{http://dx.doi.org/10.1115/GT2024-127971}},
doi = {{10.1115/GT2024-127971}},
volume = {{4}},
year = {{2024}},
}