Rotating coherent flow structures as a source for narrowband tip clearance noise from axial fans

2018 ◽  
Vol 417 ◽  
pp. 198-215 ◽  
Author(s):  
Tao Zhu ◽  
Dominic Lallier-Daniels ◽  
Marlène Sanjosé ◽  
Stéphane Moreau ◽  
Thomas Carolus
Keyword(s):  
Tip Clearance ◽  
Flow Structures ◽  
Axial Fans ◽  
Coherent Flow Structures

Rotating Coherent Flow Structures as a Source for Narrowband Tip Clearance Noise from Axial Fan

2016 ◽  
Author(s):  
Tao Zhu ◽  
Dominic Lallier-Daniels ◽  
Marlene Sanjose ◽  
Stephane Moreau ◽  
Thomas H. Carolus
Keyword(s):  
Tip Clearance ◽  
Flow Structures ◽  
Axial Fan ◽  
Coherent Flow Structures

Characterization of Coherent Flow Structures in a Swirl-Stabilized Spray Combustor

2021 ◽  
Author(s):  
Nicholas Rock ◽  
Scott D. Stouffer ◽  
Tyler H. Hendershott ◽  
Edwin Corporan ◽  
Paul Wrzesinski
Keyword(s):  
Flow Structures ◽  
Coherent Flow Structures

scholarly journals Design-Assisted of Pitching Aerofoils through Enhanced Identification of Coherent Flow Structures

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 11 ◽  
Author(s):  
Filippo Avanzi ◽  
Francesco De Vanna ◽  
Yin Ruan ◽  
Ernesto Benini
Keyword(s):  
Pressure Field ◽  
Navier Stokes ◽  
Flow Structures ◽  
Coupled Modes ◽  
Spectral Reconstruction ◽  
Sst Turbulence Model ◽  
Coherent Flow Structures ◽  
Highly Correlated ◽  
Naca 0012 ◽  
Proper Orthogonal

This study discusses a general framework to identify the unsteady features of a flow past an oscillating aerofoil in deep dynamic stall conditions. In particular, the work aims at demonstrating the advantages for the design process of the Spectral Proper Orthogonal Decomposition in accurately producing reliable reduced models of CFD systems and comparing this technique with standard snapshot-based models. Reynolds-Averaged Navier-Stokes system of equations, coupled with k−ω SST turbulence model, is used to produce the dataset, the latter consisting of a two-dimensional NACA 0012 aerofoil in the pitching motion. Modal analysis is performed on both velocity and pressure fields showing that, for vectored values, a proper tuning of the filtering process allows for better results compared to snapshot formulations and extract highly correlated coherent flow structures otherwise undetected. Wider filters, in particular, produce enhanced coherence without affecting the typical frequency response of the coupled modes. Conversely, the pressure field decomposition is drastically affected by the windowing properties. In conclusion, the low-order spectral reconstruction of the pressure field allows for an excellent prediction of aerodynamic loads. Moreover, the analysis shows that snapshot-based models better perform on the CFD values during the pitching cycle, while spectral-based methods better fit the loads’ fluctuations.

scholarly journals Entropy Analysis of the Flat Tip Leakage Flow with Delayed Detached Eddy Simulation

Entropy ◽  
2018 ◽  
Vol 21 (1) ◽  
pp. 21 ◽  
Author(s):  
Hui Li ◽  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
Tip Clearance ◽  
Flow Structures ◽  
Leakage Flow ◽  
Detached Eddy Simulation ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Passage Vortex ◽  
Unsteady Effects

In unshrouded turbine rotors, the tip leakage vortices develop and interact with the passage vortices. Such complex leakage flow causes the major loss in the turbine stage. Due to the complex turbulence characteristics of the tip leakage flow, the widely used Reynolds Averaged Navier–Stokes (RANS) approach may fail to accurately predict the multi-scale turbulent flow and the related loss. In order to effectively improve the turbine efficiency, more insights into the loss mechanism are required. In this work, a Delayed Detached Eddy Simulation (DDES) study is conducted to simulate the flow inside a high pressure turbine blade, with emphasis on the tip region. DDES results are in good agreement with the experiment, and the comparison with RANS results verifies the advantages of DDES in resolving detailed flow structures of leakage flow, and also in capturing the complex turbulence characteristics. The snapshot Proper Orthogonal Decomposition (POD) method is used to extract the dominant flow features. The flow structures and the distribution of turbulent kinetic energy reveal the development of leakage flow and its interaction with the secondary flow. Meanwhile, it is found that the separation bubble (SB) is formed in tip clearance. The strong interactions between tip leakage vortex (TLV) and the up passage vortex (UPV) are the main source of unsteady effects which significantly enhance the turbulence intensity. Based on the DDES results, loss analysis of tip leakage flow is conducted based on entropy generation rates. It is found that the viscous dissipation loss is much stronger than heat transfer loss. The largest local loss occurs in the tip clearance, and the interaction between the leakage vortex and up passage vortex promotes the loss generation. The tip leakage flow vortex weakens the strength of up passage vortex, and loss of up passage flow is reduced. Comparing steady and unsteady effects to flow field, we found that unsteady effects of tip leakage flow have a large influence on flow loss distribution which cannot be ignored. To sum up, the current DDES study about the tip leakage flow provides helpful information about the loss generation mechanism and may guide the design of low-loss blade tip.

scholarly journals Experimental study of coherent flow structures past a wall-mounted square cylinder

2019 ◽  
Vol 182 ◽  
pp. 137-146 ◽  
Author(s):  
Maria Ikhennicheu ◽  
Grégory Germain ◽  
Philippe Druault ◽  
Benoît Gaurier
Keyword(s):  
Experimental Study ◽  
Flow Structures ◽  
Square Cylinder ◽  
Coherent Flow Structures

scholarly journals A new methodology for the quantitative visualization of coherent flow structures in alluvial channels using multibeam echo-sounding (MBES)

2010 ◽  
Vol 37 (6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jim Best ◽  
Stephen Simmons ◽  
Daniel Parsons ◽  
Kevin Oberg ◽  
Jonathan Czuba ◽  
...  
Keyword(s):  
Flow Structures ◽  
Alluvial Channels ◽  
Quantitative Visualization ◽  
Coherent Flow Structures ◽  
Echo Sounding
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