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This presentation is made to explain the best port locations on various 2D geometries to measure Angle of Attack as a function of Pressure Differential
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A Step Forward In Stealth Technology– Pressure Differential Angle of Attack Measuring System
U. N. Mughal*1
Assistant Professor,
Mechanical Engineering Department, NED University of Engineering & Technology, Karachi, Pakistan
Email : [email protected], [email protected]
J. Masud*2
Associate Professor,
Institute of Avionics and Aeronautics Engineering, Air University, Islamabad, Pakistan
Email : [email protected], [email protected]
Outline
Flush Port Air Data System (FADS), Theme/Scope of this Research Exercise, Analysis Approach, Analysis of Potential Flow Over Rotating and Non Rotating
Cylinders, Analysis of Flow Over Sphere, Analysis of Flow Over Wedges of Different Half Wedge Angles, Analysis of Flow Over Cones of Different Half Cone Angles, Analysis of Potential Flow Over Low Speed and High Speed Airfoils Comparison of Pressure Differential w.r.t Angle of Attack Between
High Speed Airfoil and Wedge of Comparative Half Wedge Angle Comparison of Pressure Differential w.r.t Angle of Attack Between
Low Speed Airfoil and Cylinder Conclusions
Flush Air Data System
Need of Flush Airdata System:• Pitot Tube.
• Critical Parameters (Dynamic Pressure, Angle of Attack).
• Development of Flush Airdata System (FADS) Function of FADS
• Matrix of Flush Ports
• Pressure Differential
• Online computation
• Potential flow. Advantages:
• Over determined system
• Robustness.
• Error Minimization
• Accuracy
Contd. Flush Air Data System
Port Location depends upon • Large angle of attack sensitivity
• Good linearity with angle of attack,
• Minimum variation of the parameter with Mach number
Used• Hypersonic (X-15)
• Stealth, (B-2, A-12)
• Research aircrafts
• Hybrid System on F-22
Complications• High-fidelity vehicle simulations,
• Pressure ports locations
Theme/Scope of this Research Exercise,
To theoretically analyze the effects of Angle of Attack on Pressure Difference on general aerodynamic bodies like
• Rankine Half Body
• Cylinder
• Sphere
• Wedge
• Cone
• Airfoil
To suggest the best port location on the profiles of the above bodies, in order to install Pressure Differential Angle of Attack measuring instrument on them.
Analysis Approach
Potential Flow Theory for Rankine Half Body, Cylinder & Sphere
Falkan Skan Wedge Flow and Oblique & Expansion wave theory for Wedge
Similarity Solution for 3D Axisymmetric Flow and Conical Shock Wave Theory for Cone
Conformal Mapping for Airfoil Initial Conditions at Sea Level Karman-Tsien Rule for Compressibility Corrections Flow Assumption are
• Steady Flow
• Incompressible Flow
• Irrotational Flow
1. Rankine Half Body
P on Rankine Half Body
Source Strength = 2513ft2/s, Uniform stream at an angle of U=100ft/s
Different values of Stream Function.
Radial and Tangential components of velocities.
Co-efficient of Pressure CP = 1 – (V/U)2
Compressibility Correction of CP
P at corresponding ports.
Difference in Non Compressibility Corrected and Compressibility Corrected Parameters
Streamlines Flow Pattern on Rankine Half Body At Different AOA
Cp Upstream and Cp Downstream
P at Free-stream Velocity
2. Non Lifting Cylinder
P on Non Lifting Cylinder
Doublet Strength = 2513ft2/s, Uniform stream at an angle of U=100ft/s
Different values of Stream Function.
Radial and tangential components of velocities.
Co-efficient of Pressure CP = 1 – (V/U)2
Compressibility Correction of CP
P at corresponding ports.
Difference in Non Compressibility Corrected and Compressibility Corrected Parameters
Streamlines Flow Pattern on Non LiftingCylinder At Different AOA
Cp Upstream and Cp Downstream
Cp Upstream and Cp Downstream
P at Free-stream Velocity
3. Lifting Cylinder
Steps involved to Calculate P on Lifting Cylinder
Doublet Strength = 2513ft2/s, Vortex Strength = vortex of strength 1000ft2/s, Uniform stream at an angle of U=100ft/s
Different values of Stream Function.
Radial and tangential components of velocities.
Co-efficient of Pressure CP = 1 – (V/U)2
Compressibility Correction of CP
P at corresponding ports.
Difference in Non Compressibility Corrected and Compressibility Corrected Parameters
Streamlines Flow Pattern on Lifting Cylinder At Different AOA
Cp Upstream and Cp Downstream
P at Free-stream Velocity
4. Sphere
Steps involved to Calculate P on Sphere
3D Doublet Strength = 2513ft3/s, Vortex Strength = vortex of strength 1000ft2/s, Uniform stream at an angle of U=100ft/s
Different values of Stream Function.
Radial and tangential components of velocities.
Co-efficient of Pressure CP = 1 – (V/U)2
Compressibility Correction of CP
P at corresponding ports.
Difference in Non Compressibility Corrected and Compressibility Corrected Parameters
Cp Upstream and Cp Downstream
P at Free-stream Velocity
5. Wedge
Steps involved to Calculate P on Wedge
Falkan Skan Wedge Flow Theory, Subsonic Airflow,
Cp calculated using relation,
Cp = 1 – x2/(2-)
Compressibility Correction of CP
P at corresponding ports. Difference in Non Compressibility
Corrected and Compressibility Corrected Parameters
Oblique Shocks and Expansion Wave Theory, Supersonic Airflow on Wedge
Cp Upstream and Cp Downstream
P at Free-stream Velocity
Comparision Between Wedge in Subsonic and Supersonic Flow Regimes
6. Cone
Steps involved to Calculate P on Cone
Similarity Solution for 3D Axisymmetric Flow for Subsonic Airflow
Cp calculated using relation, Cp = 1 – x6/(2-)
Compressibility Correction of CP
P at corresponding ports. Difference in Non Compressibility
Corrected and Compressibility Corrected Parameters
Numerical procedure for Supersonic Airflow.
Cp Upstream and Cp Downstream
P at Free-stream Velocity
Comparision Between Cone in Subsonic and Supersonic Flow Regimes
7. Airfoil
Generated from Cylinder Using Conformal Transformation
P at Free-stream Velocity on 20% Thick Cambered Airfoil
P at Free-stream Velocity on 6% Thick Cambered Airfoil
Conclusions
Rankine Half Body Best Port Location 600-800
Non Lifting Cylinder Best Port Location 450-600
Lifting Cylinder Best Port Location 600
Sphere Best Port Location 450-600
Wedge Best Port Location SS≈SS Flow
Cone Best Port Location SS≈SS Flow
Airfoil Best Port Location 0.3 to 0.5 x/c
P Varies Linearly With Angle of Attack and Mach Number on all general Aerodynamic Bodies Analyzed
Room for Further Research
Wind Tunnel Testing of all Aerodynamic Bodies which I have used in this Exercise will support in verifying the results.
I have used Conformal Mapping to analyze flow on Airfoil, but Surface Panel Method can also be used in show results in the same direction.
QUESTIONS???