Ben Falconer 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 Turbulence strength Number of readings Velocity fluctuation

Particle Image Velocimetry? Velocimetry ( ˌ v ɛ lə ˈ s ɪ m ɪ tr ɪ ) 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 state computers –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 Velocity fluctuation

Questions?

Correlation between axes Can be extended to rotation What’s Next?

Out of plane rotation What’s Next?

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