Vortex dynamics and entropy generation in separated transitional flow over a compressor blade at various incidence angles

Measurements of transitional flow in regions of strong adverse pressure gradient on an axial compressor stator are reported. The range of observations covers separating laminar flow at transition onset, and reattachment of intermittently turbulent periodically separated shear layers. Transition was characterised by the regular appearance of turbulent spots in association with the rotor blade wake disturbances. However, the initial breakdown did not coincide with the wake passage as has usually been observed by other workers. The spots rather evolved from the growth of instability wave packets which lagged the wake passage. Data presented from the compressor blade measurements include: mean and ensemble-average velocities and associated integral parameters; distributions of total, periodic and random disturbance components; typical individual velocity fluctuation records; contours of ensemble-average random disturbance level; and boundary layer intermittency distributions. Measurements of turbulent intermittency showed a significant fall in this quantity near the wall in the reattaching flow. This has significant implications for the interpretation of transition data from surface film gage observations.

Download Full-text

Entropy Generation and Heat Transfer Performances of Al2O3-Water Nanofluid Transitional Flow in Rectangular Channels with Dimples and Protrusions

Entropy ◽

10.3390/e18040148 ◽

2016 ◽

Vol 18 (4) ◽

pp. 148 ◽

Cited By ~ 8

Author(s):

Yonghui Xie ◽

Lu Zheng ◽

Di Zhang ◽

Gongnan Xie

Keyword(s):

Heat Transfer ◽

Entropy Generation ◽

Transitional Flow ◽

Rectangular Channels

Download Full-text

Observations of Wake-Induced Transition on an Axial Compressor Blade

Volume 1: Turbomachinery ◽

10.1115/95-gt-381 ◽

1995 ◽

Cited By ~ 4

Author(s):

W. J. Solomon ◽

G. J. Walker

Keyword(s):

Reynolds Number ◽

Axial Compressor ◽

Reynolds Numbers ◽

Compressor Blade ◽

Transitional Flow ◽

Suction Surface ◽

Time Space ◽

Contour Plots ◽

Turbine Airfoils ◽

Hot Film

A closely-spaced array of hot-film gages fully covering both suction and pressure surfaces on the outlet stator of a 1.5-stage axial compressor was used to obtain dynamic measurements of wall shear stress. Observations were made over a range of Reynolds numbers at an incidence close to the design value. Various methods of presnting the data, including time-space contour plots of ensemble-average intermittency from the film gages are analyzed: related problems of interpretation are discussed. Extensive regions of laminar flow were identified on the suction surface: at the highest Reynolds number, small laminar patches were still evident at 85% chord and transitional flow covered up to 70% of suction surface length. The influence of passing rotor wakes on transition varied markedly with Reynolds number. The behavior of wake-induced transitional strips on the suction and pressure surfaces of the compressor blade differed significantly; their propagation characteristics also varied in some respects from those observed on turbine airfoils.

Download Full-text

Performance Assessment of Reynolds Stress and Eddy Viscosity Models on a Transitional DCA Compressor Blade

Aerospace ◽

10.3390/aerospace5040102 ◽

2018 ◽

Vol 5 (4) ◽

pp. 102

Author(s):

Zinon Vlahostergios

Keyword(s):

Experimental Data ◽

Flow Field ◽

Performance Assessment ◽

Reynolds Stress ◽

Eddy Viscosity ◽

Stokes Equations ◽

Turbulence Models ◽

Compressor Blade ◽

Boundary Layer Transition ◽

Transitional Flow

In the current work a detailed investigation and a performance assessment of two eddy viscosity and two Reynolds stress turbulence models for modelling the transitional flow on a double circular arc (DCA) compressor blade is presented. The investigation is focused on the comparison of the obtained computational results with available experimental data for a specific DCA compressor blade cascade which can be found in the European Research Community on Flow, Turbulence and Combustion (ERCOFTAC) experimental database. The examined flow field is very challenging for the performance assessment of the turbulence models. The blade inlet angle departs +5° from the compressor blade design conditions resulting in a complex flow field having large regions of boundary layer transition both on the suction and pressure sides of the blade with the presence of an unsteady wake. The presented results include velocity and turbulence intensity distributions along the pressure, the suction sides, and the wake region of the blade. From the comparison with the available experimental data, it is evident that in order to accurately compute such complex velocity and turbulence fields that are met in aero engine components (compressors and turbines), it is obligatory to use more advanced turbulence models with the Unsteady Reynolds Averaged Navier Stokes Equations (URANS) adoption, or other simulation and hybrid methodologies which require unsteady calculations.

Download Full-text