PIV Measurements and Computational Study

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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
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Overview

• 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

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Introduction
DUCTED FAN VTOL VEHICLES
NAME OF THE VEHICLE Diameter (inch) Height (inch) Weight (lbs) E. Power (hp)
Hiller flying platform 96 84 180  
AROD 52
Skorsky Cypher 74.4 24 240 50
Mass Helispy 11 27 6  
Istar 9 12 4 1.2
Dragon-Stalker 200 17
BAE IAV2 22 60 25  
Golden Eye- 50 27.5 22.04  
Honeywell MAV 13 16 4.2
Univ. of Rome UAV 39.3   200.6 42
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Introduction

• 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.

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Introduction

• 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.

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Introduction

• 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.

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Objectives

• 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.

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Ducted Fan Model
Rotor hub diameter 52 mm
Rotor tip diameter 120
Duct inner diameter 126
Blade height h 34
Tip clearance t/h 8.7
Max. blade thickness _at_ tip 1.5
Tailcone diameter 52
Tailcone length 105
HUB MID 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 N 13000
Tip Mach number 0.28
Reynolds number (mid-span) 7x104
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Experimental Setup
Cross Wind Blower
NOT TO SCALE
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Particle Image Velocimeter (PIV)

• 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.

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Particle Image Velocimeter (PIV)

• In our experiments
• 80C60 HiSense PIV/PLIF camera
• Nikon Micro-Nikkor 60/2.8 objective
• Double cavity frequency doubled pulsating NdYAG
  laser
• Seeding particles has diameter of 0.25-60 ?m.

Laser Sheet
CCD Camera
Laser Head
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Particle Image Velocimeter (PIV)

• 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

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Particle Image Velocimeter (PIV)

• The ensemble size is of critical importance in
  achieving statistically stable mean velocity
  distributions in SPIV data reduction process.

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Particle Image Velocimeter (PIV)
Ensemble size of 400 is optimal in achieving a
statistically stable average in the current set
of experiments.
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Experimental Results
AXIAL VELOCITY CONTOURS 9000 Rpm 15000
Rpm _at_ Hover Condition
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Experimental Results
9000 Rpm
9000 Rpm
15000 Rpm
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Experimental Results
RADIAL VELOCITY CONTOURS 9000 Rpm 15000
Rpm _at_ Forward Flight
LEADING SIDE
TRAILING SIDE
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Experimental Results
6.05 m/s
9000 Rpm
LEADING SIDE
LEADING SIDE
TRAILING SIDE
TRAILING SIDE
9000 Rpm
15000 Rpm
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Experimental Results
VELOCITY MAGNITUDE CONTOURS STREAMLINES 9000
Rpm _at_ Hover and Forward Flight
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Experimental Results
6.05 m/s
9000 Rpm
LEADING SIDE
TRAILING SIDE
Hover
Forward Flight
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Experimental Results
Duct Boundary
9000 Rpm
Drop in axial velocity due to lip separation
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Experimental Results
VELOCITY MAGNITUDE CONTOURS STREAMLINES 15000
Rpm _at_ Hover and Forward Flight
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Experimental Results
6.05 m/s
LEADING SIDE
TRAILING SIDE
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Specific actuator disk based fan model

• 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.

PRESSURE INLET (atmospheric static pressure
specified)
Fan Surface
PRESSURE OUTLET (atmospheric static pressure
specified)
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Specific actuator disk based fan model
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Specific actuator disk based fan model
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Specific actuator disk based fan model
Measured and computed axial velocity component _at_
the inlet of the ducted fan for 9000Rpm Hover
condition
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Summary

• 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.

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Conclusions

• 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.

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Conclusions

• 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.

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BACK UP SLIDES
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Computational Results
rgt0
rlt0
Phase Locked Approached of PIV Measurements (Image
recorded with digital camera on full laser power)
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PIV to Pitot Probe Comparison
Vertical test arrangement
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Comparison between PIV and Pitot probe results
PIV Validation with Pitot probe results
W/o cylinder w/ cylinder
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Ensemble effect (2)
Definition
W/o cylinder w/ cylinder
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Figure 24 Comparison of velocity profiles
Out-of plane component in-plane component
axial (z-direction)