This document summarizes a seminar presentation on investigating turbulent flow over stepped airfoils through computational fluid dynamics. It discusses the objectives to study the effects of step location, depth, and configuration on lift, drag, and lift-to-drag ratio. Results are presented for various step parameters showing pressure distributions, velocity profiles, and coefficient comparisons. It is concluded that a lower stepped airfoil produces higher lift but higher drag compared to an unmodified airfoil, while an upper step reduces lift but can delay stall at high angles of attack. The optimal design depends on the flight conditions.

1. Seminar-2
ROSHAN SAH
USN :- 17AE60R01
M.Tech (1st Year)
Dept. of AerospaceEngineering,
Indian Instituteof Technology
Kharagpur(IIT KGP)

2. Topic covered :-
• NOMENCLATURE
• LITERATURE REVIEW
• THEORY
• DESIGN OF THE STEPPED AIRFOIL
• GOVERNING EQUATIONSand TURBULENT MODELLING
• BOUNDARYCONDITION
Topicto be covered:-
• RESULT AND DISCUSSION
1. Effectof steplocation
2.Effectof stepdepth
3.Efectof newconfigurationof step
• CONCLUSION
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3. Figure2: Validationof CLand CD for
NACA 2412 airfoil
VALIDATION TEST AND GRID INDEPENDENCY:-
Figure3: Grid independencyof stepped
airfoil.
Ref.[1]
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4. RESULTS AND DISCUSSION:-
• Numerical solutionsarepresented in threeparts and results areproduced in
Reynolds numberof 5.7×106 but at four differentangles of attack, (-2, 0, 5, 10).
Effectof StepLocation:-
Figure4: Stepshapes a) upper,
b) lowersteppedairfoils
Figure5:Velocityprofile
overthe stepcornerand
Reattachment
length
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5. Figure 6: Pressuredistributionatα=0angleof
attack fora) upper, b) lowerstepped airfoils
Figure 7: Lift coefficientversusangleofattack
fordifferent steplengthfora) upper, b) lower
stepped airfoils
Ref.[1]
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6. Figure 8: Change in lift coefficientversus step
lengthfora) upper, b) lowersteppedairfoils
Figure 9: Changein dragcoefficientversus step
lengthfora) upper, b) lowersteppedairfoils
Ref.[1]
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7. Figure 10: Lift to drag ratioversus steplengthfor
a) upper, b) lowerstepped airfoils
Ref.[1]
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8. Effectof StepDepth :-
Figure 11: Pressuredistributionat α=00angleof
attack fora) upper, b) lowerstepped airfoils
Figure 12: Lift coefficientversus angleofattackfor
different stepdepthfora) upper, b) lowerstepped
airfoils
Ref.[1]
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9. Figure 13: Lift to drag ratioversusstepdepthfor
a) upper, b) lowerstepped airfoils
Ref.[1]
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10. Effectof StepConfiguration :-
Figure 14: Step shapes fora) upper, b) lowerstepped
airfoils
Figure 15: computedvelocityvectors and streamline
within the step regionatα=0
Ref.[1]
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11. Figure 16: Pressuredistributionat α=00angleof
attack fora) upper, b) lowerstepped airfoils
Figure 17: Lift coefficientversusangleofattack
fordifferent steplengthfora) upper, b) lower
stepped airfoil
Ref.[1]
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12. Figure 18: Lift to drag ratioversus steplengthfor
a) upper, b) lowerstepped airfoil
Ref.[1]
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13. CONCLUSION
• Drag coefficient experienced higher at all angles of attack in all cases. Drag increment for
lower stepped airfoil is less than the upper stepped airfoil drag at the same angle of attack,
step depth and step length.
• Incorporating backward-facing step on upper surface caused a reduction of lift coefficient and
lift to drag ratio at all angles of attack. Therefore the presence of step on upper surface offers
no advantages over unmodified airfoil but showed some positive effects on delaying the stall
point. The improvement of stall angle of attack is increased with the increases of step
length and depth.
• From the geometric point of view of the step, it is recommended that the step on upper
surface should not be extended back completely to the trailing edge, but step cuts the
intermediate upper airfoil surface in order to reduce the negative effect of reduction in lift and
lift to drag ratio.
• For lower stepped airfoil, lift coefficient was higher at all angles of attack. In some angle of
attack a betterratio of lift to drag is achieved.
Based on this study one concluded thata single configuration is not, and cannotbe, the best
configuration atevery angle ofattack.
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14. REFERENCES
[1] Masoud Boroomandand Shirzad Hosseinverdi , Numerical Investigationof
TurbulentFlow Arounda Stepped Airfoilat High Reynolds NumberASME
2009 Fluids Engineering Division Summer MeetingVolume 1:ISBN: 978-0-
7918-4372-7
[2] Kline R, The ultimatepaperplane. Simonand Schuster, NewYork, N.Y, 1985
[3] LumsdaineE, Johnson W.S, FletcherL.M, Peach J.E, Investigationof the
Kline-Fogleman Airfoil Section forRotorBlade Application. 1974, NASA, AE-
74-1054-1
[4] Finaish F, Witherspoon S, Aerodynamicperformanceof an airfoilwith
step-inducedvortex for lift augmentation. J Aerospace Eng, ASCE, 1998; 7:9-16
[5] Abbot I. H, Von Doenhoff A. E, Theory of Wing Sections. McGraw-Hill
Book Company, NewYork, 1949
[6] Fertis D. G, Newairfoil designconceptwith improvedaerodynamic
characteristics. J Aerospace Eng, ASCE, 1994; 7:328-339
[7] Adams E. W, Johnston J. P, Eaton J. K, Experimentson the structureof
turbulentreattaching flow. 1984, Report MD- 43, Departmentof Mechanical
Engineering, Stanford University
[9] Thangam S, KnightD. D, Effect of step heighton the separated flow pasta
backward facingstep. Phys, Fluids, 1989; 3:604-606
[9] Adams E. W, Eaton J. K, An LDA studyof the backward facingstep flow
including theeffect of velocity bias. J. Fluids Eng, 1988; 110:275-282
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