DLR de Chart 1 AHS 74 Dirk Rabe

DLR. de • Chart 1 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 Parametric Design Studies of the Helicopter Rotor Noise using Variable. Fidelity Methods Dirk Rabe, Gunther Wilke DLR Institute of Aerodynamics and Flow Technology May 17 th, 2018 74 th AHS Phoenix, Arizona

DLR. de • Chart 2 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 Content 1. Motivation 2. Methodology 3. Comparison of Various Methods for selected Rotor Blades 4. Results of the Parametric Design Study 5. Conclusion and Outlook

DLR. de • Chart 3 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 1. Motivation 2. Methodology 3. Comparison of Various Methods for selected Rotor Blades 4. Results of the Parametric Design Study 5. Conclusion and Outlook

DLR. de • Chart 4 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 1. Motivation • Multidisciplinary development of rotor blades takes time ERATO blade design • ERATO (DLR/ONERA) design process – 8 years • ERATO Blue Edge® – 17 years • 25 years of design and development for quiet rotor blade • Development tools range from BET+wake models to higher order CFD Goal: Find fast and accurate methods for aeroacoustic design studies Source: www. Airbushelicopters. asia H 160 with Blue Edge® blade

DLR. de • Chart 5 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 1. Motivation 2. Methodology 3. Comparison of Various Methods for selected Rotor Blades 4. Results of the Parametric Study 5. Conclusion and Outlook

DLR. de • Chart 6 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 2. Methodology Comprehensive Code HOST Flow/Vortex solution HOST, UPM, FLOWer FW-H-Aeroacoustic Code APSIM Sound Pressure Propagation Fluid-Structural-Numerical process chain

DLR. de • Chart 7 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 2. Methodology • BET + wake models: - airfoil tables - prescribed/free wake • Panel method: - incompressible (correction factor) - inviscid • CFD: - higher order schemes - 40 Mio. grid cells HOST P. WAKE F. WAKE UPM Oneshot UPM Coupled UPM FLOWer 4 Euler RANS Radial 39 17 80 Chord 1 49 144 Azimuth [°] 2 2 0. 1

DLR. de • Chart 8 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 2. Methodology • BET + wake models: - airfoil tables - prescribed/free wake • Panel method: - incompressible (correction factor) - inviscid • CFD: - higher order schemes - 40 Mio. grid cells HOST UPM P. WAKE FLOWer 4 Coupled UPM RANS Radial 39 17 80 Chord 1 49 144 Azimuth [°] 2 2 0. 1

DLR. de • Chart 9 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 1. Motivation 2. Methodology 3. Comparison of Various Methods for selected Rotor Blades 4. Results of the Parametric Design Study 5. Conclusion and Outlook

DLR. de • Chart 10 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 3. Comparison of Various Methods for selected Rotor Blades • Wind tunnel tested rotor blades • Different blade tip shapes by aeroacoustic means • Investigation of 6° descent flight Wind tunnel blade: HARTII 7 AD ERATO 4 4 4 R [m/ft] 2. 0/6. 56 2. 1/6. 89 Mtip [-] 0. 638 0. 660 0. 616 μ [-] 0. 150 0. 154 0. 165 Ct/σ [-] 0. 594 0. 533 0. 631 NB [-] 7 AD ERATO

DLR. de • Chart 11 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 3. Comparison of Various Methods for selected Rotor Blades – HARTII Experiment P. WAKE Assessment: fair(o) Coupled UPM good(+) HARTII – noise carpets – 8– 40 BPF – SPL [d. B] RANS good(+)

DLR. de • Chart 12 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 3. Comparison of Various Methods for selected Rotor Blades – 7 AD Experiment P. WAKE Assessment: bad(-) Coupled UPM RANS good(+) fair(o) 7 AD – noise carpets – 8– 40 BPF – SPL [d. B]

DLR. de • Chart 13 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 3. Comparison of Various Methods for selected Rotor Blades – ERATO Experiment P. WAKE Assessment: fair(o) Coupled UPM RANS good(+) fair(o) ERATO – noise carpets – 8– 40 BPF – SPL [d. B]

DLR. de • Chart 14 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 3. Comparison of Various Methods for selected Rotor Blades – Review Methods HARTII 7 AD ERATO P. WAKE o - o F. WAKE o - - Oneshot UPM ++ o + Coupled UPM + + + Euler + o o RANS + o o Assessment of noise carpets Average simulation resources [cpuh]

DLR. de • Chart 15 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 1. Motivation 2. Methodology 3. Comparison of Various Methods for selected Rotor Blades 4. Results of the Parametric Design Study 5. Conclusion and Outlook

DLR. de • Chart 16 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Baseline • 7 AD baseline: • ERATO flight state • lower Mtip • 2 d. B noise reduction • Use of validated methods: • P. WAKE • Coupled UPM • Investigated parameters: • an/dihedral • twist Rotor blade definition of the 7 AD baseline

DLR. de • Chart 17 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Anhedral Samples Best sample P. WAKE Coupled UPM

DLR. de • Chart 18 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Anhedral – P. WAKE Baseline Best Design P. WAKE – anhedral – noise carpets – 8– 40 BPF – SPL [d. B] Difference

DLR. de • Chart 19 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Anhedral – Coupled UPM Baseline Best Design Difference Coupled UPM – anhedral – noise carpets – 8– 40 BPF – SPL [d. B]

DLR. de • Chart 20 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Anhedral – Coupled UPM – anhedral – comparison of vortex fields

DLR. de • Chart 21 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Twist P. WAKE Coupled UPM Samples Best sample Twist distribution

DLR. de • Chart 22 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Twist – P. WAKE Baseline Best Design P. WAKE – twist – noise carpets – 8– 40 BPF – SPL [d. B] Difference

DLR. de • Chart 23 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Twist – Coupled UPM Baseline Best Design Coupled UPM – twist – noise carpets – 8– 40 BPF – SPL [d. B] Difference

DLR. de • Chart 24 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 4. Results of the Parametric Design Study – Review of noise reduction An/Dihedral Twist P. WAKE (max. SPL / largest reduction) -1 / -10 -3 / -3 Coupled UPM (max. SPL / largest reduction) -6 / -7 -1 / -7

DLR. de • Chart 25 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 1. Motivation 2. Methodology 3. Comparison of Various Methods for selected Rotor Blades 4. Results of the Parametric Design Study 5. Conclusion and Outlook

DLR. de • Chart 26 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 5. Conclusion and Outlook Conclusion: • Investigation of wind tunnel tested rotor blades: • best results were found using free-wake coupled panel method • CFD results roughly 4 d. B under estimated for all test cases, higher grid resolution necessary • Performed parametric design study with anhdral and twist: • design trends of wake model and panel method align, prediction discrepancies exist • dihedral showed most promising results Outlook: double check parametric design study results with CFD optimization study, combination of design parameters multi-objective investigation (aerodynamics + aeroacoustics)

DLR. de • Chart 27 > AHS 74 > Dirk Rabe • Parametric Design Studies of Helicopter Rotor Noise > 17. 5. 2018 Thank you for your attention. Are there any questions?