Exploration of the Physics of Hub Drag

Transcription

1 Exploration of the Physics of Hub Drag Felipe Ortega, Rajiv Shenoy, Vrishank Raghav Marilyn Smith and Narayanan Komerath Daniel Guggenheim Georgia Institute of Technology AIAA ASM Conference, Nashville - TN Jan 9 th -12 th 2012

2 Acknowledgements The authors gratefully acknowledge the support of the Office of Naval Research and the associated technical monitor, Dr. Judah Milgram. Assistance from Alex Forbes, Ryan McGowan and Rafael Lozano for the experimental data acquisition and reduction and from Marlin Holmes for the CFD data reduction is acknowledged and greatly appreciated by the authors.

3 Introduction Motivation Major Challenges Objective Approach Experimental Computational Results Force Measurements Flow Field Analysis Frequency Spectra Conclusions Outline

4 Introduction

5 Significance of Hub Drag Parasite Drag Limits Range, Speed and Payload fraction Improvement in blade life, reduction in blade weight Hub ~ 30% Parasite Drag ~ 10% of total power Huge uncertainty (~80%) at design stage Requires Further Investigation

6 Major Challenges Complex Geometry Complex Flow interactions Tubes, Wires, Linkages, Fasteners! Interference Drag Effect of Rotation Large Range of Reynolds Numbers Drag of Rotating Components Compressibility Effects

7 Objectives Isolate and quantify different sources Tighten tolerances for empirical prediction Experiment + CFD Force, Velocity and Frequency Measurements

8 Approach Experimental Approach Computational Approach

9 Experimental Setup Generic Model 1/4 th scale Easy Deconstruction Hub plates, Swash-plate, shanks, pitch links, drive shaft Three Configurations a) HubCapped b) Plugged Shank c) UnPlugged

10 Experimental Setup Schematic of the Hub Model mounted in the Wind Tunnel

11 Experimental Methodology Force Measurements Load cell measurements 6 Axis load cells Z = 0 Wake Velocity Measurements Particle Image Velocimetry (PIV) Measurements location z = 0 and x = 1D Frequency Spectra Hot film measurements Measurements at 4 locations x = 0.5D

12 Computational Setup and Methodology FUN3D Unstructured and Overset Methods Advanced Turbulence Models a) Unadapted Anisotropic grid adaptation Minimize Numerical Dissipation Reduce Computational Costs b) Adapted

13 Results Force Measurement Quasi Steady and Rotating Correlation between CFD and experiment Effect of Rotation

14 Quasi Steady Hub Drag

15 Quasi Steady Hub Drag Correlation Good Correlation No Reynolds Number effects

16 Effect of Rotation on Drag The effect of rotation is negligible Deconstructed Drag Reynolds Number effects D/q 0 static

17 Results Flowfield Analysis Static and Rotating Correlation between CFD and experiment Momentum deficit in wake

18 Measured U velocity Deficit U = 20mph

19 CFD correlations z = 0 and x = 1D Momentum Integral Drag 0 degrees hub position 240 RPM

20 Wake Vorticity Contours from CFD

21 Frequency Spectra Results Static and Rotating 4 1

22 Static Spectra 30mph

23 Rotating Spectra 30mph 240 RPM

24 Rotating Spectra 50mph 240 RPM

25 Conclusions Force Measurements Typical behavior No effect of rotation Wake Momentum deficit Asymmetric wake Good CFD correlations Frequency Spectra Good CFD correlations at certain locations Bringing CFD up to speed with Experiments

26 THANK YOU