Numerical Simulations of the Steady and Unsteady Aerodynamic Characteristics of a Circulation Control Wing Airfoil

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Numerical Simulations of the Steady and Unsteady
Aerodynamic Characteristics of a Circulation
Control Wing Airfoil
Yi Liu, Lakshmi N. SankarSchool of Aerospace
EngineeringGeorgia Institute of Technology,
Atlanta GA 30332-0150 Robert J. Englar, Krishan
K. Ahuja Georgia Tech Research Institute Georgia
Institute of Technology, Atlanta, GA 30332-0844
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OVERVIEW

• Motivation and Objectives
• Related Research Work
• Mathematical and Numerical Formulation
• Results and Discussion
• Circulation Control Wing Airfoil Shape and the
  Body-Fitted C-H Grid
• Steady Jet Results
• Pulsed Jet Results
• Conclusions

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MOTIVATION and OBJECTIVES

• Noise pollution from the large aircraft has
  become a major problem that needs to be solved.
• A major source of large aircraft airframe noise
  during take-off and landing is expected to be the
  high-lift systems - namely flaps, slat, and the
  flap-edges and gaps.
• An alternative to conventional high-lift systems
  is Circulation Control Wing (CCW) technology.

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RELATED RESEARCH WORK

• Experimental studies show that very high lift
  coefficient values (as high as 8.5 at a0) can be
  achieved by CCW technology (Englar).
• Numerical studies of the dynamic stall
  characteristics of Circulation Control Wing
  airfoil have also been done (Shrewsbury).
• Aeroacoustic characteristics of CCW
  configurations are being studied at GTRI (Ahuja).
• Several synthetic and pulsed jet studies have
  also been reported (Wygnansky, Lorber, Wake,
  Hassan and Oyler). These studies do not address
  CCW concept, however.

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MATHEMATICAL and NUMERICAL FORMULATION

• Three-dimensional compressible unsteady Reynolds
  Averaged Navier-Stokes equations are solved in a
  strong conservation form on curvilinear
  coordinates.
• This 3-D code was used in a 2-D mode in this
  study.
• The scheme is second or fourth order accurate in
  space and first order accurate in time.
• Baldwin-Lomax and Spalart-Allmaras one-equation
  turbulence models have been used.
• The jet slot location, slot size, blowing
  velocity and direction of blowing can easily be
  varied in the analysis.

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JET BOUNDARY CONDITIONS

• The driving parameter for jet blowing is the
  momentum coefficient, Cm, defined as follows

Where
is mass flow rate of jet flow

• We specify Cm, orientation of the jet and the
  total temperature of jet.
• Other quantities such as pressure and density
  are found by extrapolation and /or Ideal Gas Law.

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The CCW Airfoil Shape
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The C-H GRID for the CCW Airfoil
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FLOW CONDITIONS

• P? 14.2 psia 0.9324 atm
• ?? 0.00225 slugs/ft3 1.1596 kg/m3
• V? 94.3 ft/sec 28.743 m/s
• M? 0.0836, Re 0.395 106
• Chord of the Airfoil C 8 0.20 m
• Jet Slot Height h 0.015 0.0004 m
• Jet slot located at x/c 88.75 on the upper
  side of the airfoil.
• These values are matched with the experimental
  set-up.

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STEADY JET RESULTS
Angle of Attack 0 degree, Integral Flap 30 degrees
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The Variation of Lift Coefficient with the Angle
of Attack
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Lift Coefficient Variation with Time for the
No-Blowing Case

• The Vortex Shedding Frequency is about 400 Hz at
  this case

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The Stream Function Contours for the No-Blowing
Case
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The Stream Function Contours for the Blowing
Case, Cm0.1657
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The Lift Coefficient for CCW Airfoil for
No-Blowing Case Comparisons between Different
Turbulence Models
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The Lift Coefficient for CCW Airfoil for Blowing
Case Comparisons between Different Turbulence
Models
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PULSED JET STUDIES

• Pulsed jet studies were done to answer
• ---- Can pulsed jets be used to achieve
  desired increases
• in the lift coefficient at lower mass flow
  rates relative
• to a steady jet?
• ----What is the optimum wave shape for the
  pulsed jet,
• ie, how should it vary with time?
• ---- What are the effects of the pulsed jet
  frequency
• on the lift coefficient?

• Sinusoidal and Square wave form variations were
  considered. Sinusoidal forms were found
  ineffective.

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Pulsed Jet Effects on Lift Coefficient with
Time Comparisons between Different Frequencies
Pulsed Jet
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CONCLUSIONS

• CCW concept is an extremely effective way of
  achieving high CLmax, without the drawbacks of
  conventional high-lift systems.
• The steady jet calculations are in good agreement
  with the measurements. It is seen that the jet
  blowing can successfully eliminate the vortex
  shedding, a potential noise source.
• The pulsed jet configuration can give larger
  increments in lift coefficient compared to the
  steady jet at the same mass flow rate.
• The pulsed jet performance improved at higher
  pulse frequencies.