Drag reduction of a wing-body configuration via spanwise forcing - - PowerPoint PPT Presentation

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Nov 17, 2022 188 likes •536 views

Drag reduction of a wing-body configuration via spanwise forcing Andrea Gadda, Jacopo Banchetti, Giulio Romanelli, Maurizio Quadrio Dipartimento di Scienze e Tecnologie Aerospaziali Politecnico di Milano / Jacopo Banchetti Drag reduction of

SLIDE 1

Drag reduction

f a wing-body configuration

via spanwise forcing

Andrea Gadda, Jacopo Banchetti, Giulio Romanelli, Maurizio Quadrio

Dipartimento di Scienze e Tecnologie Aerospaziali Politecnico di Milano

Jacopo Banchetti Drag reduction of a wing-body configuration via spanwise forcing / 25

SLIDE 2

Motivation

Effectiveness of skin-friction drag reduction techniques in aeronautical applications

Drag components of Transport Aircraft in Cruise: Mele et al., J. of Aircraft, 2016

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SLIDE 3

Quadrio, Ricco & Viotti, JFM09

Potential for large energy savings

Low-Re, incompressible flows in simple geometry.

[QRV09]

What about an airplane?

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SLIDE 4

Background (Gatti & Quadrio, JFM16)

Waves can be assimilated to drag-reducing roughness

Streamwise travelling waves produce a vertical shift ∆B of the logarithmic portion of the mean velocity profile Drag reduction rate R is linked to ∆B ∆B+ at non-low Re becomes Reynolds independent U+ = 1 κ log(y+) + B + ∆B+

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SLIDE 5

Case of study

AIAA Second Drag Prediction Workshop (DLR-F6)

DLR-F6 is a modern transport aircraft, with a transonic design Wing-body configuration RANS Spalart-Allmaras Turbulence model Fully turbulent boundary layer Re = 3 · 106 based on reference chord M = 0.75 Flight lift coefficient 0.5

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SLIDE 6

Present work

Forcing is introduced by a modified wall function U+ = 1 κlog(y+) + B + ∆B+ Coarse mesh available in Drag Prediction Workshop website Forcing applied over the entire aircraft

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SLIDE 7

AeroX

A GPU-CPU compressible RANS solver

Finite volumes Compressible (transonic) Speedup by GPU: AMD 380X FURY X (2015) ∼ 230USD ∼ 650USD i7 5930k-6 4.3x 8.7x ∼ 600USD In the present work: GPU: AMD 380X 2 · 106 elements: convergence in ∼ 45 min

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SLIDE 8

Validation

DLR-F6 Polar curve

0.2 0.4 0.6 0.8 0.01 0.02 0.03 0.04 0.05 CL CD Experimental Cessna NSU3D AeroX

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SLIDE 9

Drag Reduction

Friction and Pressure drag decomposition

Jacopo Banchetti Drag reduction of a wing-body configuration via spanwise forcing / 25

SLIDE 10

Drag Reduction

Friction and Pressure drag decomposition

Expected Friction drag reduces by 23% Pressure drag is unchanged Total drag reduces by at most 14%

−10 10 20 30 −4 −2 2 DR% α[deg] Expected

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SLIDE 11

Drag Reduction

Friction and Pressure drag decomposition

Expected Actual Friction drag reduces by 23% Pressure drag is unchanged Total drag reduces by at most 14% 22%

−10 10 20 30 −4 −2 2 DR% α[deg] Expected Actual

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SLIDE 12

Drag Reduction

Friction and Pressure drag decomposition

Expected Actual Friction drag reduces by 23% Pressure drag is unchanged Total drag reduces by at most 14% ∼ 23% changed 22%

−10 10 20 30 −4 −2 2 DR% α[deg] Friction Pressure

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SLIDE 13

Local Friction Reduction

Upper view

Local Friction Reduction close to 23% where the configuration is clean Strong variations on the upper wing surface

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Local Friction Reduction

Frontal view

Local Friction Reduction unexpectedly high in the front fuselage

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SLIDE 15

Local Pressure

Upper view

Fuselage and lower wing surface unchanged Changes on upper wing surface

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SLIDE 16

Local Pressure

Pressure coefficient distribution

Secondary effect: Shock delay

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−0.4 −0.2 0.2 0.4 0.6 0.2 0.4 0.6 0.8 1 −CP x/c Reference Controlled

SLIDE 17

Lift Coefficient

CL − α curve

Secondary effect: Lift increase

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−0.4 −0.2 0.2 0.4 0.6 0.8 1 −4 −2 2 CL α[deg] Reference Controlled

SLIDE 18

Drag reduction at constant lift

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10 20 30 0.2 0.4 0.6 0.8 DR% CL Expected

SLIDE 19

Drag reduction at constant lift

Drag reduction is always higher than expected Lift increase - Stall begins at higher CL

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10 20 30 0.2 0.4 0.6 0.8 DR% CL Expected Actual

SLIDE 20

Net power saving at constant lift

Active techniques require input power Input power is estimated via known trends in channel flow

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SLIDE 21

Net power saving at constant lift

Active techniques require input power Input power is estimated via known trends in channel flow

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10 20 30 0.2 0.4 0.6 0.8 S% CL Expected

SLIDE 22

Net power saving at constant lift

Net power saving S higher than 10%

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10 20 30 0.2 0.4 0.6 0.8 S% CL Expected Actual

SLIDE 23

Comparison with MTC 2016

Despite the differences

MTC16 Actual Solver UZEN / FLOWer AeroX Aircraft CRM DLR-F6 Re 5 · 106 3 · 106 M 0.85 0.75 Turbulence model SST Spalart-Allmaras DR technique Riblets Spanwise forcing Forcing formulation ω at wall Wall function Same qualitative results: Direct effects: R close to the expected value Indirect effects: Shock delay - Lift increase

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SLIDE 24

Doubts?

Do we trust these results?

Further investigations needed: Transition? Log Law?

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SLIDE 25

Doubts?

Do we trust these results?

Further investigations needed: Transition? Log Law? "One coincidence is just a coincidence. Two coincidences are a clue. Three coincidences are a proof." (A. Christie)

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SLIDE 26

Thank you for your attention Questions?

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SLIDE 27

Jacopo Banchetti Drag reduction of a wing-body configuration via spanwise forcing / 25

SLIDE 28

S(A+)

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SLIDE 29

How does S changes with forcing amplitude?

S at low-Re incompressible channel flow rapidly decreases after ∼ A+ = 7

−15 −5 5 15 25 5 10 15 20 S A+

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SLIDE 30

How does S changes with forcing amplitude?

Shock delay increase with A+

0.2 0.4 0.6 0.2 A+ −CP x/c

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SLIDE 31

How does S changes with forcing amplitude?

S at low-Re incompressible channel flow rapidly decreases after ∼ A+ = 7

5 15 5 10 15 20 S A+

Actual S slightly increases until A+ = 12

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SLIDE 32

∆LFR & −∇p?

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SLIDE 33

Local Friction Reduction

Frontal view

Local Friction Reduction unexpectedly high in the front fuselage

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SLIDE 34

Local Friction Reduction

Pressure gradient and Local Friction Reduction

(LFR − LFRexpected) ∝ −∇p?

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