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.

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 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.

Aerodynamics of leading-edge protection tapes for wind turbine blades

2020 ◽  
pp. 0309524X2097544
Author(s):  
Desirae Major ◽  
Jose Palacios ◽  
Mark Maughmer ◽  
Sven Schmitz
Keyword(s):  
Boundary Layer ◽  
Wind Turbine ◽  
Numerical Models ◽  
Turbine Blades ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Wind Turbine Blades ◽  
Layer Transition ◽  
Tape Edge ◽  
The Impact

This paper presents results of a comparative study on the effect of standard and tapered leading-edge protection (LEP) tapes on the annual energy production (AEP) of a utility-scale 1.5 MW wind turbine. Numerical models are developed in STAR-CCM+ to estimate the impact of LEP tapes on lift and drag coefficients of an NACA 64-618 airfoil operating at Re = 3 × 106. Experimental drag coefficient data are collected for LEP tapes applied to the tip-section of a de-commissioned wind turbine blade for numerical validation. The objective is to determine the physical mechanisms responsible for the aerodynamic degradation observed with standard LEP tapes, and to design a tapered LEP tape that reduces the associated adverse impact on AEP. An in-house wind turbine design and analysis code, XTurb-PSU, is used to estimate AEP using airfoil data obtained by STAR-CCM+. For standard LEP tapes, laminar-to-turbulent boundary-layer transition occurs at the LEP tape edge, resulting in AEP losses of 2%–3%. Comparable tapered LEP tapes can be designed to suppress boundary-layer transition for backward-facing step heights below a critical value such that associated impact on AEP is negligible.

scholarly journals Vane Clocking Effects on Stator Suction Side Boundary Layers in a Multistage Compressor

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Natalie R. Smith ◽  
Nicole L. Key
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Suction Side ◽  
Secondary Flows ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Boundary Layer Development ◽  
Multistage Compressor ◽  
Vane Clocking ◽  
The Impact

The stator inlet flow field in a multistage compressor varies in the pitchwise direction due to upstream vane wakes and how those wakes interact with the upstream rotor tip leakage flows. If successive vane rows have the same count, then vane clocking can be used to position the downstream vane in the optimum circumferential position for minimum vane loss. This paper explores vane clocking effects on the suction side vane boundary layer development by measuring the quasi-wall shear stress on the downstream vane at three spanwise locations. Comparisons between the boundary layer transition on Stator 1 and Stator 2 are made to emphasize the impact of rotor-rotor interactions which are not present for Stator 1 and yet contribute significantly to transition on Stator 2. Vane clocking can move the boundary layer transition in the path between the wakes by up to 24% of the suction side length at midspan by altering the influence of the Rotor 1 wakes in the 3/rev modulation from rotor-rotor interactions. The boundary layer near the vane hub and tip experiences earlier transition and separation due to interactions with the secondary flows along the shrouded endwalls. Flow visualization and Stator 2 wakes support the shear stress results.

Effects of Unforced Bounday Layer Transition on the Performance of a Two-Dimensional Hypersonic Inlet

2013 ◽  
Vol 275-277 ◽  
pp. 466-471
Author(s):  
Hai Feng Miao ◽  
Lv Rong Xie ◽  
Weng Xiao Chai
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Transition ◽  
Two Dimensional ◽  
Layer Transition ◽  
Recovery Coefficient ◽  
Static Pressure Distribution ◽  
Hypersonic Inlet ◽  
Flow Rate Increase ◽  
Compression Ramp ◽  
Onset Location

Numerical investigation was conducted on a typical two-dimensional hypersonic inlet to study the influence of unforced boundary layer transition affected by compression ramp geometric parameters on the inlet performance. The numerical results show that the transition onset location on the compression ramp can be delayed by filleting the ramp intersection, and also the inlet's performance obviously improves when the transition onset location is delayed. Compared with full turbulent situation, when the boundary layer transition occurs, the unstart of the inlet is significantly mitigated, the heat transfer rate on the compression ramp decreases, both the total pressure recovery coefficient and mass flow rate increase at both design and off-design points. But the static pressure distribution along the ramp is fairly independent of the varieties of boundary layer.

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