flowpac acoustics research scott c. morris thomas j. mueller

FlowPAC Acoustics ResearchFlowPAC Acoustics Research

Scott C. MorrisThomas J. Mueller

Overview

• Basic and applied research• Mix of theoretical, computational, and

experimental capabilities• Experimental tools include:

– Anechoic Wind Tunnel (AWT)– Phased Microphone Array– Laser vibrometry– Particle Image Velocimetry

Schematic of Rotor Wake Phenomena

Swirling Flow Phenomena

Wake Distortion by Swirl

Top View of the Acoustic Pressure of a 3D Cascade with 30o Stagger

NDTE Dual Array Cross-spectra (Scaled)

St = fyf/U

ref

10-2 10-1 100 101

Adj

uste

d S

PL

(dB

): S

PL 0

+ 5

0log

10(U

ref 0

/Ure

f)

-60

-40

-20

0

20

40

60

80

Uref = 69ft/s Uref = 75ft/s Uref = 80ft/s Uref = 85ft/s Uref = 90ft/s Uref = 100ft/s

Experimental Approach:

Acoustic TheoryLES calculations

Hot-wire & PIV measurements

Far field signature

Boundary Conditions

Unsteady wall pressure

ijijijijs SSP 2

Acoustic Arrays

Array Panel #1

Flow

Model

Beamforming Results(Example SPL map)

Uref = 69 ft/s

Array #1z = 42 in.

Test section boundary

Model trailing edge location

Flow: L to R

Inlet noise

Trailing edge noise

Collector noise

How well does the array work? LOW Frequency

example

Combined sound

BF-Left BF-Right

Acoustic spectra: 3 regions

101

102

103

104

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

Frequency (Hz)

Gp 1p 1

Pressure Auto-Spectral Density for Array #1

69 ft/s75 ft/s80 ft/s85 ft/s90 ft/s95 ft/s100 ft/s

Low frequency

Vortex shedding

Broadband

PIV Experimental Setup

Trailing Edge12-bit CCD Cameras

Nd YAG Lasers

Lasers Sheet

Camera view areas

Flow

Instantaneous Flow Field Resutls

shadow area

Instantaneous vorticity contours

Phase averaged vorticity

Prediction of broadband sound

Current Projects Include:

• Trailing Edge Sound• Ducted Propulsion• Acoustics of very light fluid-structure

interactions• Window buffeting • Effect of structural acoustics on dipole

source strength