1. PIV Measurements and Computational Study around a 5-Inch Ducted Fan for VTOL UAV Ali Akturk, Akamol Shavalikul & Cengiz Camci 01.05.2009 VLRCOE (Vertical Research Lift Center of Excellence) Turbomachinery Aero-Heat Transfer Laboratory Department of Aerospace Engineering The Pennsylvania State University Presented at the 2009 47th AIAA Aerospace Sciences Meeting

2. Overview Turbomachinery Aero-Heat Transfer Laboratory INTRODUCTION OBJECTIVES DUCTED FAN MODEL EXPERIMENTAL SETUP PARTICLE IMAGE VELOCIMETER (PIV)‏ EXPERIMENTAL RESULTS AND DISCUSSION THE SPECIFIC ACTUATOR DISK BASED FAN MODEL SUMMARY AND CONCLUSIONS

3. Introduction Turbomachinery Aero-Heat Transfer Laboratory NAME OF THE VEHICLEDiameter (inch)Height (inch)Weight (lbs)E. Power (hp) Hiller flying platform9684180 AROD52 Skorsky Cypher74.42424050 Mass Helispy11276 Istar91241.2 Dragon-Stalker20017 BAE IAV2226025 Golden Eye- 5027.522.04 Honeywell MAV13164.2 Univ. of Rome UAV39.3 200.642 DUCTED FAN VTOL VEHICLES

4. Introduction Turbomachinery Aero-Heat Transfer Laboratory There has been many studies to quantify the flow field properties around ducted fans. Martin and Tung tested a ducted fan in hover condition and in forward flight with different crosswind velocities. They have measured aerodynamic loads and performed hot-wire velocity surveys at inner and outer surface of the duct and across the downstream wake. Fleming, Jones and Lusardi conduct wind tunnel experiments and computational studies on 12” ducted fan. They have concentrated on ducted fan performance in forward flight.

5. Introduction Turbomachinery Aero-Heat Transfer Laboratory Graf, Fleming and Wings improved ducted fan forward flight performance with new design leading edge geometry which has been determined to be the significant factor in offsetting the effects of the adverse aerodynamic characteristics. Lind, Nathman and Gilchrist carried out a computational study using panel method.

6. Introduction Turbomachinery Aero-Heat Transfer Laboratory He and Xin developed the ducted fan models based on a nonuniform and unsteady ring vortex formulation for duct and lade element model for fan. Zhao and Bil proposed CFD simulation to design and analyze an aerodynamic model of a ducted fan UAV in preliminary design phase with different speeds and angles of attack.

7. Objectives Turbomachinery Aero-Heat Transfer Laboratory The main aim is to analyze complicated flow field around the ducted fan in hover and horizontal flight conditions is investigated. A ducted fan that has a 5” diameter is used for analysis. Quantification of velocity field at the inlet and exit of the ducted fan by Planar PIV measurements. To generate an efficient definition of fan boundary condition using for actuator disk model.

8. Ducted Fan Model Turbomachinery Aero-Heat Transfer Laboratory Rotor hub diameter52 mm Rotor tip diameter120 Duct inner diameter126 Blade height h34 Tip clearance t/h8.7 % Max. blade thickness @ tip1.5 Tailcone diameter52 Tailcone length105 HUBMID SPAN TIP Blade inlet angle  1 60 o 40 o 30 o Blade exit angle  2 30 o 45 o 60 o Blade chord mm 32 30 28 Design rpm N13000 Tip Mach number0.28 Reynolds number (mid-span) 7x10 4

9. Experimental Setup Turbomachinery Aero-Heat Transfer Laboratory Cross Wind Blower NOT TO SCALE

10. Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Laser Beam Source PIV Camera Calibration plate Fan Blades Basic steps of PIV experimental procedure : Flow is seeded. The flow region of interest is illuminated. Scattering light from the particles forming the speckle images is recorded by cameras. Recordings are analyzed by means of correlation software.

11. In our experiments: 80C60 HiSense PIV/PLIF camera Nikon Micro-Nikkor 60/2.8 objective Double cavity frequency doubled pulsating Nd:YAG laser Seeding particles has diameter of 0.25-60  m. Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory Fan Blades CCD Camera Laser Head Laser Sheet

12. Procedure used in our system : Aligning camera and laser sheet. The image pairs of PIV domains are recorded. The image maps are divided into 32 x 32 pixel interrogation areas and 25% overlapping is used which generated 1748 vectors. All the image pairs are adaptive correlated, moving average validated and then ensemble averaged to obtain true mean flow. Measurement domains size : [156 mm x 96 mm] Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Fan Blades

13. The ensemble size is of critical importance in achieving statistically stable mean velocity distributions in SPIV data reduction process. Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory PIV Camera

14. Particle Image Velocimeter (PIV) Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Fan Blades Ensemble size of 400 is optimal in achieving a statistically stable average in the current set of experiments.

15. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades AXIAL VELOCITY CONTOURS 9000 Rpm & 15000 Rpm @ Hover Condition

16. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades 9000 Rpm 15000 Rpm

17. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades RADIAL VELOCITY CONTOURS 9000 Rpm & 15000 Rpm @ Forward Flight LEADING SIDE TRAILING SIDE

18. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory 9000 Rpm 15000 Rpm LEADING SIDE TRAILING SIDE LEADING SIDE TRAILING SIDE 6.05 m/s

19. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades VELOCITY MAGNITUDE CONTOURS & STREAMLINES 9000 Rpm @ Hover and Forward Flight

20. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades 9000 Rpm LEADING SIDE TRAILING SIDE 6.05 m/s Hover Forward Flight

21. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades 9000 Rpm Duct Boundary Drop in axial velocity due to lip separation

22. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory Fan Blades VELOCITY MAGNITUDE CONTOURS & STREAMLINES 15000 Rpm @ Hover and Forward Flight

23. Experimental Results Turbomachinery Aero-Heat Transfer Laboratory LEADING SIDE TRAILING SIDE 6.05 m/s

24. Specific actuator disk based fan model Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Fan Blades Incompressible Navier Stokes equations are solved. Unstructured computational mesh. 700000 tetrahedral cells. Symmetry boundary condition is applied at the side surfaces. Pressure inlet and outlet boundary conditions are applied at top and bottom. Pressure jump boundary condition is applied at the fan surface. Fan Surface PRESSURE OUTLET (atmospheric static pressure specified) PRESSURE INLET (atmospheric static pressure specified)

25. Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Specific actuator disk based fan model

26. Turbomachinery Aero-Heat Transfer Laboratory PIV Camera Specific actuator disk based fan model

27. Turbomachinery Aero-Heat Transfer Laboratory Measured and computed axial velocity component @ the inlet of the ducted fan for 9000Rpm Hover condition Specific actuator disk based fan model

28. Summary Turbomachinery Aero-Heat Transfer Laboratory Experimental and computational investigation around 5 inch diameter ducted fan for V/STOL UAV. Planar PIV system used to measure velocity field around the ducted fan. Axial and radial velocity components at the inlet/exit region of the ducted fan were measured in hover and horizontal flight at 6m/s. Computational study based on solving incompressible Navier-Stokes equations was carried out. The specific actuator disk based fan-model used for pressure jump across the fan rotor.

29. Conclusions Turbomachinery Aero-Heat Transfer Laboratory The performance of the ducted fan was highly affected from the crosswind velocity. That separation bubble has proven to affect the exit flow of the fan rotor. Non-uniformities introduced to the inlet and exit flow by the effect of crosswind.

30. Conclusions Turbomachinery Aero-Heat Transfer Laboratory Increase in rotational speed enhances the performance at 9000 Rpm and15000 Rpm in hover condition. Increase of rotational speed reduced effect of separation bubble. The specific actuator disk based fan model was able to predict inlet flow velocity distribution well at 9000 Rpm.

32. BACK –UP SLIDES

33. Computational Results Turbomachinery Aero-Heat Transfer Laboratory Phase Locked Approached of PIV Measurements (Image recorded with digital camera on full laser power) r>0r<0

34. PIV to Pitot Probe Comparison Turbomachinery Aero-Heat Transfer Laboratory “Vertical” test arrangement

35. Comparison between PIV and Pitot probe results W/o cylinderw/ cylinder PIV Validation with Pitot probe results

36. Ensemble effect (2) W/o cylinderw/ cylinder Definition:

37. Figure 24: Comparison of velocity profiles Out-of –plane componentin-plane component axial(z-direction)