Effects of Surface Waviness on Fan Blade Boundary Layer Transition and Profile Loss—Part I: Methodology and Computational Results

2021 ◽  
Vol 144 (2) ◽  
Author(s):  
Jinwook Lee ◽  
Zoltán S. Spakovszky ◽  
Edward M. Greitzer ◽  
Mark Drela ◽  
Jérôme Talbotec
Keyword(s):  
Boundary Layer ◽  
Acoustic Noise ◽  
Transition Process ◽  
Boundary Layer Transition ◽  
Wavy Surface ◽  
Computational Results ◽  
Surface Waviness ◽  
Layer Transition ◽  
Fan Blade ◽  
Onset Location

Abstract This two-part paper describes a new approach to determine the effect of surface waviness, arising from manufacture of composite fan blades, on transition onset location movement and hence fan profile losses. The approach includes analysis and computations of unsteady disturbances in boundary layers over a wavy surface, assessed and supported by wind tunnel measurements of these disturbances and the transition location. An integrated framework is developed for analysis of surface waviness effects on natural transition. The framework, referred to as the extended eN method, traces the evolution of disturbance energy transfer in flow over a wavy surface, from external acoustic noise through exponential growth of Tollmien–Schlichting (TS) waves, to the start and end of the transition process. The computational results show that surface waviness affects the transition onset location due to the interaction between the surface waviness and the TS boundary layer instability and that the interaction is strongest when the geometric and TS wavelengths match. The condition at which this occurs, and the initial amplitude of the boundary layer disturbances that grow to create the transition onset is maximized, is called receptivity amplification. The results provide first-of-a-kind descriptions of the mechanism for the changes in transition onset location as well as quantitative calculations for the effects of surface waviness on fan performance due to changes in surface wavelength, surface wave amplitude, and the location at which the waviness is initiated on the fan blade.

Effects of Surface Waviness on Fan Blade Boundary Layer Transition and Profile Loss — Part I: Methodology and Computational Results

2021 ◽  
Author(s):  
Jinwook Lee ◽  
Zoltán S. Spakovszky ◽  
Edward M. Greitzer ◽  
Mark Drela ◽  
Jérôme Talbotec
Keyword(s):  
Boundary Layer ◽  
Acoustic Noise ◽  
Transition Process ◽  
Boundary Layer Transition ◽  
Wavy Surface ◽  
Computational Results ◽  
Surface Waviness ◽  
Layer Transition ◽  
Fan Blade ◽  
Onset Location

Abstract This two-part paper describes a new approach to determine the effect of surface waviness, arising from manufacture of composite fan blades, on transition onset location movement and hence fan profile losses. The approach includes analysis and computations of unsteady disturbances in boundary layers over a wavy surface, assessed and supported by wind tunnel measurements of these disturbances and the transition location. An integrated framework is developed for analysis of surface waviness effects on natural transition. The framework, referred to as the extended eN method, traces the evolution of disturbance energy transfer in flow over a wavy surface, from external acoustic noise through exponential growth of Tollmien-Schlichting (TS) waves, to the start and end of the transition process. The computational results show that surface waviness affects the transition onset location due to the interaction between the surface waviness and the TS boundary layer instability, and that the interaction is strongest when the geometric and TS wavelengths match. The condition at which this occurs, and the initial amplitude of the boundary layer disturbances that grow to create the transition onset is maximized, is called receptivity amplification. The results provide first-of-a-kind descriptions of the mechanism for the changes in transition onset location as well as quantitative calculations for the effects of surface waviness on fan performance due to changes in surface wavelength, surface wave amplitude, and the location at which the waviness is initiated on the fan blade.

Effects of Surface Waviness on Fan Blade Boundary Layer Transition and Profile Loss—Part II: Experimental Assessments and Applications

2021 ◽  
Vol 144 (2) ◽  
Author(s):  
Jinwook Lee ◽  
Vaishnavi Ramaswamy ◽  
Zoltán S. Spakovszky ◽  
Edward M. Greitzer ◽  
Mark Drela ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Wave ◽  
Boundary Layer Transition ◽  
Blade Surface ◽  
Surface Waviness ◽  
Layer Transition ◽  
Fan Performance ◽  
Fan Blade ◽  
The Impact ◽  
Onset Location

Abstract Part II describes the experimental assessment and the application of the ideas in Part I concerning the mechanisms that determine the role of blade surface waviness on laminar-turbulent transition and their consequent effect on civil aircraft fan performance. A natural transition wind tunnel was designed and constructed to characterize the impact of surface waviness on transition, using both hotwire anemometry and infrared thermography. The experimental results support the new hypothesis presented in Part I, concerning the way in which blade surface waviness affects fan performance through motion of the transition onset location due to interaction between surface waviness and Tollmien–Schlichting (TS) boundary layer instability. In particular, the theoretical amplification of the TS waves, and the corresponding transition onset location movement due to surface waviness, was borne out over a range of variations in Reynolds number, nondimensional surface wavelength, nondimensional surface wave height, and location of surface wave initiation, relevant to composite fan blade parameters. Further, the increase of receptivity coefficient, and thus, the initial amplitude of disturbances due to geometric resonance between surface wavelength and TS wavelength was also confirmed by the experiments. Surface waviness was estimated, in some cases, to result in a nearly 1% decrease in fan efficiency compared to a nonwavy blade. Suggestions are given for mitigation of the effects of waviness, including the idea of blade curvature rescheduling as a method to delay transition and thus decrease loss.

Effects of Surface Waviness on Fan Blade Boundary Layer Transition and Profile Loss — Part II: Experimental Assessments and Applications

2021 ◽  
Author(s):  
Jinwook Lee ◽  
Vaishnavi Ramaswamy ◽  
Zoltán S. Spakovszky ◽  
Edward M. Greitzer ◽  
Mark Drela ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Wave ◽  
Boundary Layer Transition ◽  
Blade Surface ◽  
Surface Waviness ◽  
Fan Performance ◽  
Fan Blade ◽  
The Impact ◽  
Onset Location ◽  
Dimensional Surface

Abstract Part II describes the experimental assessment and the application of the ideas in Part I concerning the mechanisms that determine the role of blade surface waviness on laminar-turbulent transition and their consequent effect on civil aircraft fan performance. A natural transition wind tunnel was designed and constructed to characterize the impact of surface waviness on transition, using both hotwire anemometry and infrared thermography. The experimental results support the new hypothesis presented in Part I, concerning the way in which blade surface waviness affects fan performance through motion of the transition onset location due to interaction between surface waviness and Tollmien-Schlichting (TS) boundary layer instability. In particular, the theoretical amplification of the TS waves, and the corresponding transition onset location movement due to surface waviness, was borne out over a range of variations in Reynolds number, non-dimensional surface wavelength, non-dimensional surface wave height, and location of surface wave initiation, relevant to composite fan blade parameters. Further, the increase of receptivity coefficient, and thus the initial amplitude of disturbances due to geometric resonance between surface wavelength and TS wavelength, was also confirmed by the experiments. Surface waviness was estimated, in some cases, to result in a nearly 1% decrease in fan efficiency compared to a non-wavy blade. Suggestions are given for mitigation of the effects of waviness, including the idea of blade curvature rescheduling as a method to delay transition and thus decrease loss.

Modelling Vortex Generating Jet-Induced Transition in Low-Pressure Turbines

2013 ◽  
Author(s):  
Florian Herbst ◽  
Andreas Fiala ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
Cross Flow ◽  
Transition Process ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Layer Transition ◽  
Wall Flows

The current design of low-pressure turbines (LPTs) with steady-blowing vortex generating jets (VGJ) uses steady computational fluid dynamics (CFD). The present work aims to support this design approach by proposing a new semi-empirical transition model for injection-induced laminar-turbulent boundary layer transition. It is based on the detection of cross-flow vortices in the boundary layer which cause inflectional cross-flow velocity profiles. The model is implemented in the CFD code TRACE within the framework of the γ-Reθ transition model and is a reformulated, re-calibrated, and extended version of a previously presented model. It is extensively validated by means of VGJ as well as non-VGJ test cases capturing the local transition process in a physically reasonable way. Quantitative aerodynamic design parameters of several VGJ configurations including steady and periodic-unsteady inflow conditions are predicted in good accordance with experimental values. Furthermore, the quantitative prediction of end-wall flows of LPTs is improved by detecting typical secondary flow structures. For the first time, the newly derived model allows the quantitative design and optimization of LPTs with VGJs.

Numerical simulation of boundary-layer transition and transition control

1989 ◽  
Vol 199 ◽  
pp. 403-440 ◽  
Author(s):  
E. Laurien ◽  
L. Kleiser
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Transition Process ◽  
Numerical Results ◽  
Boundary Layer Transition ◽  
Two Dimensional ◽  
Layer Transition ◽  
Longitudinal Vortices ◽  
Tollmien Schlichting

The laminar-turbulent transition process in a parallel boundary-layer with Blasius profile is simulated by numerical integration of the three-dimensional incompressible Navier-Stokes equations using a spectral method. The model of spatially periodic disturbances developing in time is used. Both the classical Klebanoff-type and the subharmonic type of transition are simulated. Maps of the three-dimensional velocity and vorticity fields and visualizations by integrated fluid markers are obtained. The numerical results are compared with experimental measurements and flow visualizations by other authors. Good qualitative and quantitative agreement is found at corresponding stages of development up to the one-spike stage. After the appearance of two-dimensional Tollmien-Schlichting waves of sufficiently large amplitude an increasing three-dimensionality is observed. In particular, a peak-valley structure of the velocity fluctuations, mean longitudinal vortices and sharp spike-like instantaneous velocity signals are formed. The flow field is dominated by a three-dimensional horseshoe vortex system connected with free high-shear layers. Visualizations by time-lines show the formation of A-structures. Our numerical results connect various observations obtained with different experimental techniques. The initial three-dimensional steps of the transition process are consistent with the linear theory of secondary instability. In the later stages nonlinear interactions of the disturbance modes and the production of higher harmonics are essential.We also study the control of transition by local two-dimensional suction and blowing at the wall. It is shown that transition can be delayed or accelerated by superposing disturbances which are out of phase or in phase with oncoming Tollmien-Schlichting instability waves, respectively. Control is only effective if applied at an early, two-dimensional stage of transition. Mean longitudinal vortices remain even after successful control of the fluctuations.

Infrared thermography of hypersonic boundary layer transition induced by isolated roughness elements

2021 ◽  
Author(s):  
Shicheng Liu ◽  
Meng Wang ◽  
Hao Dong ◽  
Tianyu Xia ◽  
Lin Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Infrared Thermography ◽  
Roughness Element ◽  
Transition Process ◽  
Boundary Layer Transition ◽  
Hypersonic Boundary Layer ◽  
Layer Transition ◽  
Leading Role ◽  
Roughness Elements ◽  
Element Shape

Roughness element induced hypersonic boundary layer transition on a flat plate is investigated using infrared thermography at Ma = 5 and 6 flow condition. Surface Stanton number is acquired to analyze the effect of roughness element shape and height on the transition process. The correlation between the vortex structure induced by roughness element and the wall heat streaks is established. The results indicate that higher roughness element would induce stronger streamwise heat flux streaks, lead to transition advance in streamwise centerline and increase the width of spanwise wake. Moreover, for low roughness element, the effect of the shape is not obvious, and the height plays a leading role in the transition; for tall roughness element, the effect on accelerating transition for the diamond roughness element is the best, the square is the worst, and the shape plays a leading role in the transition.

Unsteady Transition in an Axial-Flow Turbine: Part 1—Measurements on the Turbine Rotor

1990 ◽  
Vol 112 (2) ◽  
pp. 206-214 ◽  
Author(s):  
J. S. Addison ◽  
H. P. Hodson
Keyword(s):  
Boundary Layer ◽  
Cross Sections ◽  
Axial Flow ◽  
Transition Process ◽  
Turbine Rotor ◽  
Boundary Layer Transition ◽  
Surface Boundary ◽  
Suction Surface ◽  
Layer Transition ◽  
Time Resolved

Previously published measurements in a low-speed, single-stage, axial-flow turbine have been reanalyzed in the light of more recent understanding. The measurements include time-resolved hot-wire traverses and surface hot film gage measurements at the midspan of the rotor suction surface with three different rotor-stator spacings. Part 1 investigates the suction surface boundary layer transition process, using surface-distance time plots and boundary layer cross sections to demonstrate the unsteady and two-dimensional nature of the process. Part 2 of the paper will describe the results of supporting experiments carried out in a linear cascade together with a simple transition model, which explains the features seen in the turbine.

Effect of Surface Roughness on Conjugate Heat Transfer of a Turbine Vane

2016 ◽  
Author(s):  
Hongyang Li ◽  
Yun Zheng
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Suction Side ◽  
Transition Process ◽  
Considerable Effect ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Turbine Vane ◽  
Effect Of Surface

For the purpose of researching the effect of surface roughness on boundary layer transition and heat transfer of turbine blade, a roughness modification approach for γ-Reθ transition model was proposed based on an in-house CFD code. Taking surface roughness effect into consideration, No. 5411 working condition of Mark II turbine vane was simulated and the results were analyzed in detail. Main conclusions are as follows: Surface roughness has little effect on heat transfer of laminar boundary layer, while has considerable effect on turbulent boundary layer. Compared with smooth surface, equivalent sand roughness of 100μm increases the temperature for about 28.4K on suction side, reaching an increase of 5%. Under low roughness degree, effect of shock wave dominants on boundary layer transition process on suction side, while above the critical degree, effect of surface roughness could abruptly change the transition point.

Investigation of the Laminar-Turbulent Transition of Boundary Layers Disturbed by Wakes

1982 ◽  
Author(s):  
H. Pfeil ◽  
R. Herbst ◽  
T. Schröder
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Boundary Layers ◽  
Transition Process ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Turbulent Spots ◽  
Turbulent Transition ◽  
Time Space ◽  
Favorable Pressure Gradient

The boundary layer transition under instationary afflux conditions as present in the stages of turbomachines is investigated. A model for the transition process is introduced by means of time-space distributions of the turbulent spots during transition and schematic drawings of the instantaneous boundary layer thicknesses. To confirm this model, measurements of the transition with zero and favorable pressure gradient are performed.

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