ben falconer b.p.falconer@warwick.ac.uk supervisors: peter bryanston -cross, brenda timmerman

Systems for

High VelocityParticle Image Velocimetry

Ben Falconerb.p.falconer@warwick.ac.uk

Supervisors: Peter Bryanston-Cross, Brenda Timmerman

Credit: AEF

• Quieter Aircraft– 96EPNdB for night takeoff/landing– Noise produced by turbulence close to engine

Why?

Credit: Steve Allen

• Turbulence produces noise– Far field noise produced close to engine– Affected by area under wing– Dependent on velocities

Far Field Noise

𝑢𝑟𝑚𝑠=√ 1𝑁 ∑𝑖=1

𝑁

(𝑢𝑖❑−𝑢)2

Turbulence strength

Number of readings

Velocity fluctuation

Particle Image Velocimetry?

Velocimetry (ˌvɛləˈsɪmɪtrɪ) n.The measurement of the velocity of fluids

Abbreviated to PIV

• Seed flow• Illuminate• Take images• Cross correlate

How PIV Works

Credit: LaVision

• 2 Cameras• Resolves 3

components• Angle to focal

plane– Optimum θ=45°

Stereo PIV

• Focus on non-perpendicular planes• Lens held at angle

Scheimpflug Principle

• One of the largest anechoic chambers in The World– 27m x 26m

x 16m– Large scale

tests• 1:10

Noise Test Facility

Credit: QinetiQ

• No one enters during tests– Control centre 200m away

• Expensive– £10,000/hour

• Compressor– 400m/s

Noise Test Facility

Credit: QinetiQ

• Flow moving 400m/s• Can’t get close

– But particles only 0.3µm

• Remote operation• Must be fast• Full range of

distances

In Practice

• 4m x 2.6m x 4.7m• Around flightstream• 2.7m optical standoff• Mounted on 2D

traverse• Bi-directional

Full Range Rig

• Enables viewing 2 targets– For parallel planes– Preserves stereo

Mirrored Scheimpflug

• 4m x 2.6m x 4.7m• Around flightstream• 2.7m optical standoff• Mounted on 2D

traverse• Bi-directional

Full Range Rig

• Cameras moved– View under wing

• Lasers moved– Avoids wing

• Upstream• Stereo view

Wing Rig

• Hostile conditions– Vibrations kill hard drives

• Remote access• Data throughput

– Images are acquired at 60MB/s per camera– Theoretical max 125MB/s on gigabit Ethernet– 80MB/s with overheads

Computer System

• Control computer– Synchronises cameras and lasers– Accurate to nanosecond scale

• Solid statecomputers– Close to cameras– Not affected by

vibrations– Low storage capacity

Rig Computers

• Storage servers– Dedicated gigabit Ethernet each– ~3.5TB per server– Away from vibrations

Control Room

• 2 Control computers– 1 or 2 person operation– Calculate 880,000 run parameters– Organise 40TB of resulting data

Control Room

• Velocity maps–Time averaged

Results

• Turbulent kinetic energy– Indicates variation in velocity

• Closest measurement to actual acoustics

Results

𝐸𝑘=12 ((𝑢1′ )2+(𝑢2′ )

2+(𝑢3′ )

2)

Velocity fluctuation

Questions?

• Correlation between axes

• Can be extended to rotation

What’s Next?

• Out of plane rotation

What’s Next?

Computer System

Computer System• Additions to

base system– Mirrors– Focusing– CCTV– Remote

power

• 880,000 measurements– 1100 measurements per position– 20 positions per condition– 40 conditions

• 40TB of data– 3 Cameras– 16MB per image– 880,000 measurements

Configurations