Transition Flow and Aero- acoustic Analysis of...
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Transition Flow and Aero-
acoustic Analysis of NACA0018
Satish Kumar B, Fred Mendonça,
Ghuiyeon Kim, Hogeon Kim
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Transition Flow and Aero-
acoustic Analysis of NACA0018
Satish Kumar B, Fred Mendonça,
Ghuiyeon Kim, Hogeon Kim
![Page 3: Transition Flow and Aero- acoustic Analysis of NACA0018mdx2.plm.automation.siemens.com/sites/default/files/Presentation/19... · Transition Flow and Aero- acoustic Analysis of ...](https://reader031.fdocuments.us/reader031/viewer/2022022003/5a9d59bf7f8b9abd058c2846/html5/thumbnails/3.jpg)
Transition Flow and Aero-
acoustic Analysis of NACA0018
Satish Kumar B, Fred Mendonça,
Ghuiyeon Kim, Hogeon Kim
![Page 4: Transition Flow and Aero- acoustic Analysis of NACA0018mdx2.plm.automation.siemens.com/sites/default/files/Presentation/19... · Transition Flow and Aero- acoustic Analysis of ...](https://reader031.fdocuments.us/reader031/viewer/2022022003/5a9d59bf7f8b9abd058c2846/html5/thumbnails/4.jpg)
Introduction
Geometry & Computational Domain
Meshing Details
Boundary Conditions
Steady State Analysis – Preliminary Study
Unsteady LES
Acoustic & Spectral Analysis
Comparison with Experiments
References
Contents
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Introduction
• Whistling noise from the side mirror at high speed is an ongoing
serious issue for both design and aero-acoustic performance of a
vehicle.
• Design changes in the side mirror for reducing its contribution to
the total drag of vehicle and also to improve the fuel economy
potentially cause a discrete noise by flow transition from Laminar to
Turbulent via the growth of Tollmein - Schlichting (T-S) instability
waves.
• Simple case of flow over NACA0018 aerofoil at Re=1.6e5 is
considered to analyze the complex features of flow transition and
its associated noise at fundamental level.
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Aerofoil and Computational Domain
Aerofoil: NACA0018
Aerofoil Angle of Attack (AOA): 6 Degrees
Aerofoil Chord Length(CL):0.08 m
Aerofoil Span:0.16 m (2CL)
Free stream Diameter: 2 m (25CL)
Trailing Edge Thickness:8e-5 m (0.002CL)
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Mesh Modeling
Mesh Models
Surface Remesher
Trimmer
Prism Layer Mesher
Reference Values:
Prism Layer Stretching: 1.1
Base Size: 4 mm
Maximum cell size: 1600 %
Number of prism layers: 15
Prism layer thickness: 1 mm
Surface size:
Relative min. size: 0.5 mm
Relative target size: 64 mm
Template Growth Rate:
Default growth rate: Slow
Boundary growth rate: Medium
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Mesh Volumetric Controls
2 mm
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Mesh Volume
• Number of cells: 11 Million
• Y+ approximately 1 on complete airfoil surface • Prism Layers: 15
• Prism Layer Thickness: 1 mm
• Prism Layer Stretching: 1.1
• Predominantly Hexahedral in the free stream domain
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Steady State Physics – Preliminary analysis Physics Models:
Air
Three Dimensional
Steady State
Ideal Gas
Segregated Flow Solver
Segregated Energy Solver
K-Omega SST Turbulence
All Y + wall Treatment
Reference Values:
Reference Pressure:101325 Pa
Initial Conditions:
Static Pressure:0.0 Pa (Gauge)
Static Temperature:300 k
Turbulent Intensity:0.01
Turbulent Viscosity Ratio:10
Velocity:[30,0,0] m/s
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Boundary Conditions
Boundary Conditions:
Free Stream
Mach Number:0.0875
Static Temperature: 300 K
Pressure: 0 Pa
Turbulence Intensity: 0.01
Turbulent Viscosity Ratio: 10
Free Stream Non Reflecting B.C
Advantageous than Reflecting
B.C such as
Velocity Inlet
Pressure Inlet or Outlet
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Steady State Mesh Frequency Cut Off
• Measure of mesh ability in terms of resolution to capture the turbulent flow
structures in the frequency of interest.
• Demonstrates ability of mesh to predict well beyond 1kHz in the boundary
layer
• Defined in terms of Isotropic Fluctuating component of Velocity and the Cell
Dimension in direction of interest.
2 / 3( )
2MC
kf Hz
D
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Steady State Scalar Contours (Z=0.08 m)
Turbulent Viscosity Ratio
Velocity Magnitude
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Steady State Pressure Coefficients
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Unsteady LES Physics
Physics Models:
Air
Three Dimensional
Implicit Unsteady
Ideal Gas
Segregated Flow Solver
Segregated Energy Solver
LES Turbulence
WALE (Wall Adapting Local Eddy) Sub grid
Scale
All Y + wall Treatment
Aero acoustics
Ffwocs Williams-Hawkings
Reference Values:
Reference Pressure:101325 Pa
Initial Conditions:
Started from Steady RANS Calculation
1Time Step[s]=
10*Maximum Frequency Resolution [Hz]
Highest Frequency to be resolved: 10,000 Hz
Time Step: 1e-5 s
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Unsteady Pressure Coefficients : Instantaneous
Indicates suction-side inception and
growth of T-S instabilities
Suction side: Breakdown to
turbulence
No instabilities indicate laminar
flow on pressure side and leading
edge suction side
Pressure side : Breakdown
to turbulence
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Pressure Coefficients: Unsteady Mean Vs Steady
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Scalar Contours: Wall Shear Stress (suction side)
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Scalar Contours: Suction Side Q-Criterion (3D
Vorticity)
Velocity contours on Iso-surface of Q= +10
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Computed Instantaneous vorticity field at TE
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Acoustic Analysis
• Free- space Green’s function based FW-H solver used in STAR-
CCM+ environment for the computation of sound propagation.
• Aerofoil surface is considered as the impermeable dipolar
source.
• Receiver location is chosen as the same point considered in
previous computations and experiments to compare and validate
the SPL at tonal frequency.
• The acoustic pressure signal build at the receiver location is
generated from the integration of signals from the all the source
elements of aerofoil surface.
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Fast Fourier Transform of Radiated Pressure at
FW-H Receiver ( L: STAR-CCM+ , R: CFD Reference)
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Spectral Analysis
Point Spectra:
• Point located above Suction side near the trailing edge at approx.
0.8*chord
• Shows peak at 2358 Hz
Surface Spectra:
• Pressure and Suction sides
• Shows localized excitations at various selected frequencies
Symmetry Plane Spectra
• Shows localized excitations at various selected frequencies
• Shows localized and near-field radiation (directivity) patterns
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Suction Side Pressure Spectra
1000Hz 1500Hz 2000Hz
3000Hz 2500Hz 2358 Hz
2358 Hz
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Pressure Side Pressure Spectra
1000Hz 1500Hz 2000Hz
3000Hz 2500Hz 2358 Hz
2358 Hz
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Symmetry Plane Pressure Spectra & Near-field
radiation
2358 Hz
8mm
4mm
1mm
2mm
1000Hz 1500Hz 2000Hz
3000Hz 2500Hz 2358 Hz
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Direct Propagation
2000Hz
2500Hz
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Comparison with Experimental Data
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Highlights of Experimental Work
Author/Journal,Year Flow Measurement Flow Visualization Aero-acoustics
/Noise
T. Nakano et al.
/JWE,2007 PIV Liquid Crystal Coating
Condenser Microphone
(20-8000 Hz)
@ Bottom wall of AWT
Y. Takagi et al.
/ JSV,2006 PIV Liquid Crystal Coating
Condenser Microphone
(20-8000 Hz)
@Bottom wall of AWT
Fujisawa et al.
/TVSJ,2002 PIV Smoke
Sound Level Meter
10 mm underneath of
Top wall of AWT
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Spectrum of Aerodynamic Noise CFD Vs Expt.
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Turbulent Stress (urms / Uo)
CFD Vs PIV (Nakano et al.)
PIV
STAR-CCM+
Kim & Lee
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Turbulent Stress (vrms / Uo)
CFD Vs PIV (Nakano et al.)
PIV
STAR-CCM+
Kim & Lee
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Turbulent Stress (u’v’ / Uo2)
CFD Vs PIV (Nakano et al.)
PIV
STAR-CCM+
Kim & Lee
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References
H-J Kim , S. Lee , N. Fujisawa., 2006. Computation of unsteady flow and
aerodynamic noise of NACA0018 airfoil using large-eddy simulation.
International Journal of Heat and Fluid Flow 27, pp229-242.
T. Nakano , N. Fujisawa , Y. Oguma , Y. Takagi , S. Lee., 2007. Experimental
study on flow and noise Characteristics of NACA0018 airfoil.
Journal of Wind Engineering and Industrial Aerodynamics 95, pp511-531.
Y. Takagi , N. Fujisawa , T. Nakano , A.Nashimoto., 2006. Cylinder wake
influence on the tonal noise and Aerodynamic characteristics of a NACA0018
airfoil. Journal of Sound and Vibration 297, pp563-577.
Tomimatsu S , Fujisawa N., 2002. Measurement of Aerodynamic Noise and
Unsteady Flow Field around a Symmetric Airfoil.
Journal of Visualization Vol.5, No.4 ,pp381-388.
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References
Mendonca, F., Read, A., Caro, S., Debatin, K. and Caruelle, B.2005.
Aeroacoustic Simulation of Double Diaphragm Orifices in an Aircraft Climate
Cooling System.
AIAA-2005-2976.
STAR-CCM+ Version 6.06.015 User Guide and Methodology Manuals, CD-
adapco, London, UK, 2011.
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