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1. Ph.D. PUBLIC VIVA –VOCE EXAMINATION 1 VENUE: PADUR HALL-1 HITS,PADUR.CHENNAI-603103 DATE: 01-04-2024 TIME: 11.00 AM Supervisor Dr. VISHNU KUMAR GC Associate Professor Department of Aeronautical Engineering Research scholar VIGNESWARAN CM Reg. No:. AE1908 Department of Aeronautical Engineering

2. 2 INVOCATION

3. ACKNOWLEDGEMENT First and foremost, I would like to thank the Lord Almighty for His presence and immense blessings throughout the research work. I am truly grateful to my supervisor Dr. Vishnu kumar GC , Associate Professor, Department of Aeronautical Engineering for his valued interpretations, valuable guidance continuous motivation, innovative ideas, and constant support throughout my research 3

4. ACKNOWLEDGEMENT I would like to express my deepest thanks to Dr. Elizabeth Verghese , Founder Chancellor Dr. Anand Jacob Verghese , Chancellor Dr. Ashok Verghese , Pro-Chancellor Dr. S.N. Sridhara , Vice-Chancellor Dr. Angelina Geetha , Dean(E&T) Dr. C. Kezi Selva Vijila , Controller of Examinations Dr. GC. Vishnukumar , Research Supervisor Dr. R. Asokan , Dean, Department of Aeronautical Dr. Parthasarathy Vasanthakumar Head, Department of Aeronautical Dr. R. Santhanakrishnan , Research coordinator 4

5. TITLE OF THE Ph.D. THESIS “AERODYNAMIC PERFORMANCE ANALYSIS OF COFLOW JET AIRFOIL” 5

6. INTRODUCTION Evolution of Flight Curiosity sparked by birds. Early attempts and limitations. Wright Brother’s pioneering achievement. Evolution of aviation technology Advancements and innovations 6 Fig 1 – Evolution of flight

7. Airfoil Airfoil serve as the fundamental shape for generating lift in aircraft, essential for enabling flight. Fig 2(a) - Cambered airfoil 7 In an overall aircraft phases, the landing and takeoff phases required a maximum value of C l, in order to reduce the takeoff and landing distance. To overcome the small wing problems during takeoff/landing, it can be fitted with high lift devices Fig 2(b) - Airfoil evolution

8. HIGH LIFT DEVICE A high lift devices are installed on aircraft wings to enhance lift during takeoff and landing. 8 Fig 3 –Flow control technique 1.Passive flow technique 2.Active flow technique When a flow control technique is developed, there may be three characteristic needed to be considered: Aerodynamic Effectiveness (Lift & Drag coefficients) Energy efficient Easy implementation

9. CO-FLOW JET AIRFOIL The new airfoil flow control technique using co-flow jet (CFJ) is developed by considering all the above mentioned three characteristics. Fig 4- CFJ airfoil The slots are opened by translating a great portion of the suction surface downward. A high energy jet is then injected near leading edge tangentially ZNMF- zero-net mass flux Co-flow jet (CFJ) airfoil flow control technique alternative for collecting the jet mass flow from propulsion system. 9 injection slot near leading edge suction slot near trailing edge

10. LITERATURE SURVEY In-depth Exploration: This chapter focuses on an extensive review of literature concerning co-flow jet airfoil, encompassing seminal research, experiments, and computational studies. Critical Analysis: It examines the historical context, evolution of fundamental concepts, and methodologies, emphasizing their implications across diverse applications Identifying Gaps and Potential: Discuss challenges and limitations associated with co-flow jet airfoil technology, emphasizing the identification of gaps in current knowledge requiring further investigation for future advancements in aeronautical excellence. 10

11. A Review of CFJ airfoil testing: Maximum lift, stall margin, and drag reduction Fig 5(b) - The Lift curve Fig 5(a) - CFJ airfoil set up in wind tunnel 11 Zha and Paxton (2004) NACA 0025 CFJ airfoil is a unique active control flow device with ZNMF developed by Zha & Paxton (2004). Wind tunnel tests have demonstrated its efficacy in enhancing aerodynamic performance metrics, including stall angle, lift coefficient, and various other factors . Zha et al (2007) They performed the computational analysis to know the jet effects on CFJ airfoil performance using 𝑘-𝜖 turbulence model compared with experimental data.

12. LITERATURE SURVEY- continued 12 Zha et al (2006) The comparative analysis was carried out through numerical simulations, examining the differences between a CFJ airfoil equipped with both injection and suction slots and an airfoil with injection slots only. Since any airfoil with a jet injection needs to have a jet suction to satisfy the mass conservation law, this study indicates that the suction occurring on the suction surface such as the CFJ airfoil is more beneficial than drawing the jet mass flow from the aircraft engine inlet. Fig 6- The airfoil with injection and the suction occurring through the engine

13. 13 Dano et al (2006) The blending of a co-flow jet (CFJ) with mainstream is examined to reveal the insight of the CFJ airfoil mixing process by utilizing Digital Particle Image Velocimetry (DPIV) flow visualization method Fig 7 - DPIV flow visualization LITERATURE SURVEY- continued Later, in 2011 they had done the experiment to determine the aerodynamic forces acting on NACA 6415 CFJ airfoil with discrete jet injection slot. A discrete CFJ airfoil can achieve an extra 50% boost in maximum lift, an increase of 30% in stall AoA , and a substantial 60% drag reduction

14. CFJ mechanisms on aircraft wings 14 Lefebvre et al (2016) A comprehensive parametric investigation is conducted through numerical analysis, encompassing a range of 3D CFJ wings. This study focuses on the NACA 23121 airfoil and examines various parameters, and their respective impacts on critical aerodynamic properties. Boling et al (2020) The CFJ wing has greater free shear layer streamwise vorticity near the tip than the baseline wing at the same AoA and the overall strength of the tip vortex is greater for the CFJ wing, compared to the baseline wing at the same angle of attack. Wang et al (2019) CFJ wings can be attributed to their remarkable capacity for lift enhancement, which effectively counteracts the amplified induced drag, resulting in an overall superior performance.

15. CFJ airfoil embedded with Micro Compressor 15 Ren et al (2018) Conducted simulations under typical cruise conditions, replacing the conventional pump with a micro-compressor within a 3D CFJ airfoil setup. In comparison to the conventional baseline airfoil, this transformation yielded a remarkable 37.6% boost in lift coefficient, a substantial 56.6% surge in productivity efficiency, and a substantial 65.5% reduction in drag coefficient. Xu et al (2020) Conducted a comprehensive numerical analysis, revealing a distinctive phenomenon in the operation of micro-compressors. Their findings indicated that these micro-compressors operated along an operating line significantly deviating from their originally intended design operating line, characterized by a substantially lower pressure ratio.

16. CFJ electric aircraft design 16 Lefebvre & Zha (2015) Done the pioneering conceptual design of an electric airplane incorporating CFJ flow control. This innovative approach resulted in an aircraft with remarkably high wing loading, a compact size, and exceptional aerodynamic efficiency, representing a significant milestone in the development of electric aviation technology. Specification Range – 300 NM Mach – 0.15 V takeoff – 224.6 m/s W/S – 182.3 Kg/ m3 CL – 1.3 L/D – 36

17. Diverse applications of CFJ technology 17 Xu et al (2020) CFJ method incorporated on the M2129 serpentine duct for alleviating flow separation while maintaining low energy consumption. The CFJ mechanism emerges as a highly effective solution for mitigating flow distortion issues within S-duct systems, simultaneously enhancing the total pressure recovery. Fig 8(a)- S duct Fig 8(b)- Cylinder with CFJ mechanism Yang & Zha (2018) They numerically investigated the C Lmax achievable through CFJ flow control in the context of cylinder flows. Their findings indicated that the highest lift coefficient, coupled with optimal efficiency, was attained when the suction and injection slots were placed at 0° relative to the reference point.

18. A notable contribution of other researchers 18 Hossain et al (2015) Conducted meticulous experiments on wind tunnel focusing on the performance of the CFJ airfoil variant NACA 0015. Khoshnevis et al (2020) They computationally analysed the performance of CFJ NACA 0025 airfoil with five distinct medium Reynolds number by employing SST-K-ῶ turbulence model solved by URANS solver. Li et al (2020) Performed wind tunnel experiments, revealing that the PCFJ airfoil outperforms in delaying flow separation. Sun et al (2019) They performed computational analysis to enhance the performance of a wind turbine by incorporating a CFJ mechanism in a NACA 0015 airfoil. Haolin et al (2021) They performed a numerical examination to assess how adding a simple high-lift device to a CFJ airfoil could enhance its performance, specifically focusing on its suitability for low-speed take-off and landing situations.

19. RESEARCH GAP Implementation of CFJ to thin and moderate airfoil are needed detailed investigation The alternate solution for pump is required and it needed through examination Effect of position slots on aerodynamic performance studies are required. Effect of CFJ parameters on Aerodynamic performance studies by using a non dimensional number can be developed. Less numerical studies used mesh by Icem cfd tool with ‘ O’grid topology. Expanding data for real aircraft integration. Noise and Vibrations. Regulatory Considerations. 19

20. OBJECTIVE To implement a CFJ technique on a moderate thickness airfoil for enhancing the aerodynamic performance characteristic of an airfoil through the numerical analysis. To execute a numerical analysis on CFJ-equipped airfoils, employing the robust capabilities of the ICEM CFD meshing tool to ensure the precise capture of flow dynamics at predetermined points. To investigate the impact of injection and suction slot positions on the aerodynamic effectiveness of the airfoil. To establish the robust correlation between the aerodynamic characteristics of CFJ-equipped airfoils and a non-dimensional parameter. To examine an effect of the mass flow rate, jet velocity and the injection height on aerodynamic characteristic of CFJ airfoil To quantify the pump power consumption and minimization strategies 20

21. METHODOLOGY Comparison of co-Flow Jet Airfoil Performance with baseline airfoil . Effect of location and dimension of slots on aerodynamic performance of CFJ airfoil Effect of CFJ parameters on aerodynamic performance of CFJ airfoil Effect of coefficient of jet momentum on aerodynamic performance of CFJ airfoil 21 Grid independency test for baseline and CFJ airfoil . Power consumption of CFJ airfoil

22. Baseline airfoil - Design and Analysis 22 Baseline Airfoil NACA 0018 airfoil was selected for the present study. Reason for choosing NACA 0018 Airfoil . CFJ mechanism can be implemented in any airfoils with various thicknesses. Implementation easier in airfoils with larger thickness (25% of c & above). This Project targets symmetric airfoil with moderate thickness (18% of c) CFJ airfoil was designed for a specified Mach number & Reynold’s number ( M = 0.1, a corresponding velocity is 34.02m/s ) and with transition Reynold’s number ( Re = 0.65 million ) As per above requirement, the chord of the CFJ airfoil is calculated ( c = 283 mm ) and designed accordingly. Bell 23P – 39E AIRCOBRA, BOEING 294 SERIES, BOEING 299 SERIES, BOEING 314 CLIPPER are the aircrafts having NACA 0018 airfoil . Software used Design : Catia V-5 Mesh : Icem CFD Analysis : ANSYS Fluent

23. BASELINE AIRFOIL continued 23 CFD Analysis Jacobs and Sherman (1937) experimental data were used to evaluate the solver ability. The results of the numerical analysis almost in par with the experimental values. Percentage of error – 11.9% Figure 9(a) - the comparison of aerodynamic coefficients of baseline airfoil with the experimental result. Grid independency test O-type structured grid is used. M1 - 1.2 lakhs, M2 -1.8 lakhs, and M3 -2.3 lakhs nodes are generated. Selected a y + value of 1 and utilized 10 inflation layers in the mesh design. Lift Coefficient vs AoA Drag Coefficient vs AoA

24. Pressure distribution over a NACA 0018 airfoil at 0 deg Angle of attack validation [18] 24 Figure 9 (b) - pressure distribution for a baseline airfoil Reference [18] Present study

25. Pressure distribution over a NACA 0018 airfoil at Stalling(16 deg ) AoA Figure 9(c) - coefficient of pressure for a baseline airfoil at stalling angle 25

26. CFJ AIRFOIL Grid Independency Test To carry forward the CFD analysis of CFJ airfoil, the first grid-independent study has to be done. To investigate the grid independency of the computational domain, meshes with different numbers of nodes such as 50 k(grid 1), 1 lakh (grid 2), 1.6 lakhs (grid 3), 2.2 lakhs (grid 4) and 2.9 lakhs (grid 5) are generated for the following design specification. Chord length of CFJ airfoil: 283 mm Location of Injection Slot: 9% of the Chord (25.47mm) Location of Suction Slot: 82% of the Chord ( 232.06mm) Height of the Injection Slot: 0.75% of the Chord ( 2.1225mm) Height of the Suction Slot: 2.5 × Height of the Injection Slot ( 5.306mm) 26 Fig 10 – CFJ Airfoil

27. THE O GRID MESH USED IN FLOW COMPUTATION Fig.11 (a) Far field Fig.11(b) Near field 27

28. THE O GRID MESH USED IN FLOW COMPUTATION Fig.11 (c) near injection slot Fig.11 (d) near suction slot 28

29. COMPUTATIONAL DOMAIN & BOUNDARY CONDITIONS 29 Boundary conditions: Injection slot - ‘ mass flow inlet’ ( assumed as 0.15 kg/s, a corresponding velocity in injection slot = 57.6 m/s ) Suction slot - ‘outlet vent’ ( To maintain the ZNMF, static pressure at the suction slot has to be iterated to match the injection mass flow rate. ) CFJ airfoil surface – ‘ wall’ Far field – pressure far field Figure 12 - Computational Domain

30. NUMERICAL MODELLING The pressure and shear stress distribution for a 2D incompressible flow over a CFJ airfoil are computed using a pressure-based solver. For computing, the Spalart– Allmaras turbulence model was used, which was proposed by the Spalart and Allmaras (1992). With a single governing kinematic equation, the Spalart– Allmaras model was created specifically for aeronautical applications. The SIMPLE algorithm , developed by Patankar and Spalding (1972) was used to calculate the pressure-velocity coupling. The second order upwind scheme was used for spatial discretization. The convergence criteria have been chosen with the purpose of reducing the computational time and its set to 10 -08 for the iterative procedure in the simulation. 30

31. RESULTS Lift Coefficient vs AoA Drag Coefficient vs AoA Figure 13 - the aerodynamic coefficients vs the AoA curve for the four different grid sizes 31 Discussion CL curve converges after grid-3 node size where as Drag curve shows variation. grid-4 and grid-5 minimize this variation So grid-4 (2.2 lakh ) has selected as an optimum mesh size to conduct the numerical analysis for the further design.

32. Pressure and velocity contours 32 Discussion The pressure and velocity contours of a CFJ airfoil at stalling angle of attack clearly shows the flow pattern around the CFJ airfoil as well as the flow separation from the CFJ airfoil surface. The direction of the jet coming out from injection slot is tangent to the CFJ surface and it does not disrupt the streamline of the flow. The velocity vectors near suction slot clearly illustrate how well the air is sucked by the suction slot. 14(a) Pressure contours 14(b) Velocity contours Figure14 – the contours at stalling angle for grid-4 14(c) Velocity vectors near injection & suction slot

33. Velocity contour velocity contour near injection Velocity vector near injection Velocity vector near suction CFJ ANIMATION VIDEOS 33

34. VALIDATION 34 CFJ Airfoil NACA 0025 Chord 125.7mm Mach number 0.11 Re number 3.8*10^5 Free stream velocity 37.4 m/s Location of injection slot 7.11% of c Location of suction slot 83.18% of c Injection slot height 0.65% of c Suction slot height 1.96% of c Injection mass flow rate 0.22 kg/s CFD solver   RANS3D (inhouse CFD software) Turbulence model Splarat allmaras Sea level boundary conditions Wang, B., Haddoukessouni , B., Levy, J. and Zha , G.C., 2008. Numerical investigations of injection-slot-size effect on the performance of coflow jet airfoils.  Journal of Aircraft ,  45 (6), pp.2084-2091. Figure 16 - the comparison of aerodynamic coefficients of Zha -CFJ airfoil experimental and numerical (RANS3D) results with numerical (fluent solver ) result.

35. Evaluation of CFJ Performance on Aerodynamic Coefficients Part -A (With respect to geometry) Case 1 Injection slot varies from 6% to 13% of chord for a fixed suction slot at 82% of c Case 2 Injection slot varies from 6% to 13% of chord for a fixed suction slot at 85% of c Case 3 Varying suction slot height from 0.5 to 2.5 times of injection slot height for fixed suction and injection slot location 35

36. RESULTS Lift Coefficient vs AoA Drag Coefficient vs AoA 36 Case 1 The investigation is carried out for the following design specifications of CFJ airfoil for an AoA range of 0° - 20°. Chord length of CFJ airfoil: 283 mm Location of Injection Slot: varying from 6% to 13% of the C by unit increment Location of Suction Slot: 82% of the C Height of the Injection Slot: 0.75% of the C Height of the Suction Slot: 2.5 × Height of the Injection Slot Figure 17 - the lift coefficient and drag coefficient of CFJ airfoil for all design specifications

37. Case 1 continued… 37 CFJ airfoil increases lift compared to baseline due to energized flow from injection air. Flow attachment delays boundary layer separation, enhancing aerodynamic performance. Varying injection slot location from leading edge boosts lift coefficient of CFJ airfoil. CFJ mechanism alters airfoil shape, initially decreasing lift coefficient. However, lift increase from CFJ mechanism outweighs decrease from altered shape. As long as, the CFJ airfoil shape remains close to the baseline airfoil shape, it will enhance the aerodynamic coefficients of the CFJ airfoil. Overall, CFJ airfoil exhibits higher lift coefficient than baseline. Percentage increase in lift coefficient ranges from 3.6% to 31.9%. CFJ airfoil performing well in order to increase the lift coefficient also to reduce the drag coefficient

38. COEFFICIENT OF PRESSURE - Suction at 82% of c 38 Cp for an injection slot at 6% of c Cp for an injection slot at 13% of c Cp for an injection slot at 9% of c Figure 18 shows the coefficient of pressure for an injection slot at 6%, 9% & 13% of c

39. COEFFICIENT OF PRESSURE Figure 18 (b) - shows the comparison coefficient of pressure for suction @ 82% of c and injection @ 6%, 9% and 13% of c 39

40. RESULTS Lift Coefficient vs AoA Drag Coefficient vs AoA 40 Case 2 To get a better understanding of the effect of CFJ, again the investigation is carried out for the same specification But the location of Suction Slot fixed at 85% of the C. A percentage of increase in maximum lift coefficient of CFJ airfoil compares to the baseline airfoil is varies from 2.58% to 29.3% for an injection slot location varies from 6% to 13% of chord and suction slot at 85% of chord. Figure 19 - the lift coefficient and drag coefficient of CFJ airfoil for all design specifications

41. COEFFICIENT OF PRESSURE - Suction at 85% of c 41 Figure 20 - the coefficient of pressure for an injection slot at 6%, 9% & 13% of c Cp for an injection slot at 6% of c Cp for an injection slot at 9% of c Cp for an injection slot at 13% of c

42. COEFFICIENT OF PRESSURE Figure 20(b) - the comparison of coefficient of pressure for suction @ 85% of c and injection @ 6%, 9% and 13% of c 42

43. CASE 2 continued… 43 In another aspect, if the suction slot shifted from 82% of c to 85% of c, the maximum lift coefficient starts to decreasing for the fixed injection slot location. For example , the suction slot locates at 82% of the c is generate a lift coefficient 2.58% higher than the suction slot locates at 85% of the c , for the injection slot at 13% of c. Figure 21 - the comparison of lift coefficient for the injection slot at 13 % of the chord and suction slot at 82% and 85% of the chord. To reduce the workload of the pump or to reduce the power consumption of the pump, the suction slot has to locate at the airfoil where the pressure of the flow over the top surface of the airfoil is maximum. In addition, there should be a minimum optimal distance is required between injection and suction slot to conserve the mass flow rate.

44. CASE 3 Results Lift coefficient vs AoA Drag coefficient vs AoA 44 Varying suction slot height from 0.5 to 2.5 times of injection slot height for fixed suction and injection slot location. Location of Injection Slot: 9% of the Chord Location of Suction Slot: 82% of the Chord Height of the Injection Slot: 0.75% of the Chord Height of the Suction Slot: varying as 0.5, 1, 1.5, 2 & 2.5 × Height of the Injection Slot. Figure 21(b) - the comparison of the Lift coefficient and Drag coefficient of CFJ airfoil for all design specifications.

45. Case 3 continued… 45 The result shows that the coefficient of lift of CFJ airfoil is increasing by decreasing the height of the suction slot. At a certain suction slot height (threshold), lift increase due to CFJ is outweighed by aerodynamic shape effects. Percentage of increase in maximum lift compared to baseline is 17.02% to 34.55%. Concludes that increasing suction slot height decreases CFJ airfoil's lift coefficient. Beyond threshold height, aerodynamic performance decreases. Threshold height is a function of free stream Mach number, injection mass flow rate, and jet velocity.

46. COEFFICIENT OF PRESSURE - Suction at 82% of c 46 Figure 22 - the coefficient of pressure for a various suction slot height Cp for an suction height = 0.5 × injection height Cp for an suction height = 1.5 × injection height Cp for an suction height = 2.5 × injection height

47. COEFFICIENT OF PRESSURE Figure 22(b) - the comparison of coefficient of pressure for different suction height 47

48. RESULTS Lift Coefficient vs AoA Drag Coefficient vs AoA 48 CASE 3 continued… To get a better understanding of the effect of CFJ, again the investigation is carried out for the same specification But the location of Suction Slot fixed at 85% of the C. A percentage of increase in the maximum coefficient of lift of CFJ airfoil compares to the baseline airfoil is increase from 14.53% to 33.32% Figure 23 - shows the comparison of the Lift coefficient and Drag coefficient of CFJ airfoil for all design specifications.

49. COEFFICIENT OF PRESSURE - Suction at 85% of c 49 Figure 24 shows the coefficient of pressure for a various suction slot height Cp for an suction height = 0.5 x injection height Cp for an suction height = 1.5 x injection height Cp for an suction height = 2.5 x injection height

50. COEFFICIENT OF PRESSURE Figure 24(b) - shows the comparison of coefficient of pressure for different suction height 50

51. CASE 3 continued… 51 For a suction slot locate at 82% of a c having a height of 1.5 times injection slot height compare to the suction slot located at 85% of a c having the same height. The coefficient of lift is increasing from 1.8323 to 1.8492 and the required suction pressure is decreased from 20000 pa to 19280 pa to maintain the ZNMF. Figure 25 - shows the comparison of lift coefficient for the injection slot at 13 % of the chord and suction slot at 82% and 85% of the chord. Optimize the suction slot by considering location, height, and pump efficiency. Choose location where upper surface has higher pressure. Suggests suction slot height at least two times greater than injection slot height to avoid choking and reduce pump workload while maintaining aerodynamic performance.

52. COEFFICIENT OF PRESSURE Figure 25(b)- shows the comparison of coefficient of pressure for same suction height with different location of suction slot 52

53. Evaluation of CFJ Performance on Aerodynamic Coefficients Part - B (With respect to coefficient of jet momentum) The CFJ airfoil's aerodynamic performance is affected by a number of factors, including injection velocity, mass flow rate, injection height, free stream velocity, Reynolds number and slots locations. A greater number of numerical analyses are necessary to compute the C L and C D variation of the CFJ airfoil with the above specified parameters. As a result, in this project, the aerodynamic performance of the CFJ airfoil is evaluated using a non-dimensional parameter called as the Coefficient of jet Momentum. 53

54. Coefficient of jet Momentum : Similar to the C L and C D , it can also be defined as ………..(1) Where, represents the mass flow rate at injection slot, ‘ V j ’ represents the injection jet velocity, represents the density of the free stream, ‘V’ represents the velocity of the free stream and ‘S’ represents the platform area. In this study, the free stream velocity and the injection jet velocity are chosen to be in the incompressible flow range only . So the preceding equation can be simplified to ………..(2) Where, ‘ H inj ’ represents the injection slot height and ‘C’ represents the chord of the CFJ airfoil. 54

55. Design Criteria CFJ Airfoil – Nomenclature 55 CFJ airfoils analyzed with three Cμ values: 0.03, 0.04, and 0.05 Parameters altered: injection height, mass flow rate, injection velocity Injection jet velocity range: 48 to 100 m/s. Aerodynamic performance unsatisfactory when injection velocity ≤ free stream velocity Optimal performance achieved with injection velocity at least 1.5 times free stream velocity The CFJ airfoils are designed and segmented into three cases. The labeling of CFJ airfoils is designed in such a way to indicate the Cμ . Last digit multiplied by 0.01 implies Cμ for that case For example; Case 1A3 CFJ airfoil "1A" denotes constant injection slot height (0.75% chord) "3" indicates Cμ (multiplied by 0.01)

56. CASE 1 56 By keeping the height of injection slot as constant, the C μ is varied from 0.03 to 0.05 by changing the injection mass flow rate and injection jet velocity. The design specifications of the CFJ airfoils for this case are follows; V j is calculated by using equation 2 and is obtained by the equation 1. Table 1 : The design specification of the CFJ airfoils for CASE 1

57. CASE 2 57 By keeping the mass flow rate of injection slot as constant, the C μ is varied from 0.03 to 0.05 by changing the height of injection slot and injection jet velocity. The design specifications of the CFJ airfoils for this case are follows; Table 2 : The design specification of the CFJ airfoils for CASE 2 V j is calculated by using equation 1 and H inj is obtained by the equation 2.

58. CASE 3 58 By keeping the injection jet velocity as constant, the C μ is varied from 0.03 to 0.05 by changing the height of injection slot and injection mass flow rate. The design specifications of the CFJ airfoils for this case are follows; Table 3 : The design specification of the CFJ airfoils for CASE 3 is calculated by using equation 1 and H inj is obtained by the equation 2.

59. RESULTS 59 Discussion For an identical C μ , the C L is more for the CFJ airfoil with higher injection jet velocity and smaller injection slot height than the all other CFJ airfoils with different design specifications. Case 3C3 CFJ airfoil generates higher lift whereas case 1A3 CFJ airfoil generates lower lift . This 3C3 CFJ airfoil has a higher injection jet velocity, as well as a lower injection height and mass flow rate, than any other CFJ airfoils in the C μ = 0.03. Figure 26(a) Figure 26(b) Lift coefficient vs AoA of C μ = 0.03 Drag coefficient vs AoA of C μ = 0.03 Figure 26 - The comparison of Lift coefficient and Drag coefficient of CFJ airfoil for all design specifications having C μ of 0.03.

60. RESULTS - continued 60 Discussion - continued The CFJ airfoils of the Case 2B4 has generates the higher lift in the C μ of 0.04. In which the injection jet velocity is higher and the injection slot height and mass flow rate are lower compares to all other CFJ airfoils in this group The CFJ airfoils of the Case 1A4 has generates the lower lift in the C μ of 0.04. Figure 27(a) Figure 27(b) Lift coefficient vs AoA of C μ = 0.03 Drag coefficient vs AoA of C μ = 0.03 Figure 27 - The comparison of Lift coefficient and Drag coefficient of CFJ airfoil for all design specifications having C μ of 0.04.

61. RESULTS - continued 61 Discussion - continued The CFJ airfoils of the Case 2B5 has generates the higher lift in the C μ of 0.04. In which the injection jet velocity is higher and the injection slot height and mass flow rate are lower compares to all other CFJ airfoils in this group The CFJ airfoils of the Case 3A5 has generates the lower lift in the C μ of 0.04. Figure 28(a) Figure 28(b) Lift coefficient vs AoA of C μ = 0.03 Drag coefficient vs AoA of C μ = 0.03 Figure 28 - The comparison of Lift coefficient and Drag coefficient of CFJ airfoil for all design specifications having C μ of 0.05.

62. Discussion - continued… 62 CFJ airfoils with same Cμ and injection velocity have nearly identical C L . In cases 1B4 and 3C4 where injection jet velocity and Cμ are similar, C L and C D are the same. Example: Case 3A5 with lower velocity generates more C L than Case 3B4 with higher velocity. Occurs when difference in injection velocities is small. Higher injection jet velocity generally leads to more C L . Exception: CFJ airfoil with lower injection velocity but higher Cμ can generate more C L .

63. Discussion - continued… 63 Lift enhancement and drag reduction mechanisms differ for CFJ airfoils. Similar Cμ CFJ airfoils with higher injection mass flow rate have lesser C D compares to lower mass flow rate. Numerical analysis shows higher injection velocity yields more lift. Same injection velocity leads to similar lift. CFJ with lower velocity and higher Cμ can generate more lift. Rare occurrence when injection velocities differ slightly. CFJ airfoils boost lift by energizing free stream Drag reduction achieved by filling wake with larger mass flow rate of air.

64. COEFFICIENT OF PRESSURE – for salient cases 64 Cp for a case 3C3 (higher cl in cμ = 0.03) Cp for a case 1A3 (lower cl in cμ = 0.03) Cp for a case 2B4 (higher cl in cμ = 0.04) Cp for a case 1A4 (lower cl in cμ = 0.04)

65. COEFFICIENT OF PRESSURE- continued Figure29- the coefficient of pressure for a salient cases 65 Cp for a case 2B5 (higher cl in cμ = 0.05) Cp for a case 3A5 (lower cl in cμ = 0.05)

66. Hyperlink for cp graph for all cases CONTOURS FOR ALL ANALYSIS\PART 5\cp snipping part 5 66

67. Influence of CFJ parameters on aerodynamic coefficients (Part C) 67 Injection height Injection jet velocity Mass flow rate

68. Result and Discussion 68 Distinct injection height with a same jet velocity CASE 3C3 b) CASE 3C4 c) CASE 3C5 C Lmax increases with increasing height of injection slot for same jet velocity. Lift coefficient enhancement ranges from 27.7% to 41.9% ( i ) (ii) Figure 30 - lift curve for section ( i ) & (ii) (ii) Distinct jet velocity with same injection height. CASE 1B3 b) CASE 1B4 c) CASE 1B5 CFJ airfoil with higher injection velocity increases CL more than lower velocity counterpart at same slot height. CASE 1B5 airfoil exhibits 48% higher C Lmax

69. DISCUSSION – continued…. It was found that if the same velocity is injected to different slot heights, the C L max is greater for the CFJ airfoil with higher slot height , whereas when various velocity is injected to the CFJ airfoil with fixed slot height, the C L max is greater for the CFJ airfoil with higher injection velocity . Furthermore, the CFJ airfoil produces more C L has a higher injection mass flow rate, however this cannot be concluded straight away because higher injection mass flow in the both sections is due to higher velocity. Injecting a lower velocity in a higher injection slot height can also result in a higher mass flow rate. 69

70. Result and Discussion 70 (iii) Increase the injection height with increase in jet velocity a) CASE 1B3 b) CASE 3B4 c) CASE 3C5 Higher injection slot and higher jet velocity performs well Lift coefficient enhancement ranges from 14.8% to 42.6% (iii) (iv) Figure 31 - lift curve for section (iii) & (iv) (iv) Increase the injection height with decrease in jet velocity. CASE 2B5 b) CASE 2B4 c) CASE 2B3 Greater jet velocity and a lower injection slot has a higher C Lmax Lift coefficient enhancement ranges from 14.7% to 55.8%

71. DISCUSSION – continued…. This investigation's main objective was to determine which factor – injection height or jet velocity-had the biggest impacts on aerodynamic performance. The results show that lift coefficient is enhanced for increasing jet velocity with increasing injection height as well as for other circumstances, i.e. increasing injection velocity with decreasing injection height. Although higher injection slots reduce the C L due to poor aerodynamic shape, they can be overcome by injecting higher jet velocities, whereas lower jet velocities injecting into lower injection slots do not raise the C L even though they have streamlined aerodynamic shape. 71

72. DISCUSSION – continued…. Furthermore, in section ( i ), (ii) and (iii) the CFJ airfoil produces more C L has a higher injection mass flow rate, however this cannot be concluded straight away because higher injection mass flow rate in the all 3 sections is due to higher jet velocity but injecting a lower velocity in a higher injection slot height can also result in a higher mass flow rate. This condition was captured in the section (iv) 72

73. (v) Impact of injection mass flow rate All of the CFJ airfoils in section (iv) have the same mass flow rate of 0.1, however the CFJ airfoil with the higher velocity and lower slot produces more C L than the airfoil with the lower injection velocity and higher injection slot. Even with a high mass flow rate, the CFJ airfoil will not perform well if the injection velocity is low. 73

74. ENERGY EXPENDITURE Power consumption plays a vital role in the lift enhancement process, because ultimately it will determine the aircraft system efficiency, the amount of energy source to be carried, and the gross weight of the aircraft. The power consumption is determined by the mass flow rate and total pressure change across the suction and injection slot in the process is given as P t inj – total pressure at injection slot P t suc – total pressure at suction slot 74

75. To reduce the power consumption, Total pressure ratio changes across the slots has to be minimum as much as possible. Jet mass flow has to be minimum as much as possible. The basic principle to reduce the CFJ power consumption is to reduce the flow energy loss, specially the total pressure ratio that is required to sustain the CFJ. In mechanics, if a certain amount of mass flow is to be dumped to a large space via a hole, a smaller size hole will cause more energy loss than a large size hole. 75

76. It is hence expected that a large injection size CFJ airfoil may have lower power consumption than a smaller size CFJ airfoil. However, the first constrain is that the injection slot size should not be too large that it does not generate sufficient velocity and momentum to enhance lift and it will also affect the airfoil geometry. If the CFJ airfoils requires higher mass flow rate of air, the power consumption also increase. In order to reduce the power consumption, the require mass flow rate of air can be injected through various slot size and with different location so that it is possible to vary the total pressure changes 76

77. 1. Power consumption calculated for the CFJ airfoil for the suction slot is placed at the 82% & 85% of c and injection slot is varying from the 6% to 13% of c. Figure 32 - Power consumption of CFJ airfoil with varying slots location. 77

78. 2. Power consumption calculated for the CFJ airfoil for the suction slot height varies from 0.5 times to 2.5 times of injection height where the injection and suction slots are placed at 9% and 82% of c. Figure 33 - Power consumption of CFJ airfoil with varying suction slot height. 78

79. 3. Power consumption calculated for the all cases of CFJ airfoil Figure 34 - Power consumption of CFJ airfoil for all cases. 79

80. If the injection slot is placed at point on the airfoil where the static pressure is minimum, the power consumption will be minimum also if the suction slot height reduces, the power required to suck the mass flow rate is increases. The power consumption of CFJ airfoil can be reduce by enlarging the injection height for the fixed mass flow rate but if higher mass flow rate injected to the higher injection slot, the power consumption will also increase. In terms of fixed jet velocity and fixed injection height, the power consumption can reduce only by injecting less mass flow rate of air. 80

81. CONCLUSION The present study has numerically investigated the effect of the CFJ mechanism on the aerodynamic performance of airfoil. The results from the analysis are proved that the CFJ airfoil will produce more lift coefficient than the baseline airfoil. This is because the downstream gets energized due to the injection air. So that the flow remains attached over to the body, and its increased the lift coefficient. The effect of the location of the injection and suction slots on CFJ airfoil performance are also studied successfully. The result indicated that the lift coefficient is increasing by varying the injection slot location away from the leading edge for fixed suction slot location. 81

82. Continued.. This project also successfully investigated the impact of the suction slot height on the aerodynamic performance of the CFJ airfoil. This research concludes that the suction slot in the CFJ airfoil is not only designed to satisfy the ZNMF, but it also has an impact on the aerodynamic performance of the CFJ airfoil. It is observed that the coefficient of lift is increasing when the height of the suction slot is decreased which is beneficial in terms of aerodynamics requirement, but the suction pressure needed to reach the ZNMF is also increasing, which is unfavourable in terms of pump power and workload. 82

83. Continued.. This research also successfully established the correlation between aerodynamic performances of a CFJ airfoil and coefficient of jet momentum ( C μ ). According to the present investigation, the C μ is an effective non-dimensional parameter that correlates well with the CFJ airfoil's aerodynamic performance. According to numerical analysis, if C μ is identical, then the CFJ airfoil with higher injection velocity generates more lift; but, if the injection velocity is also the same, the lift is also similar; however, if C μ is high, the CFJ airfoil with lower injection velocity also generates more lift. This is a rare occurrence that only occurs when the difference in the injection jet velocities are small. 83

84. Continued.. This research also successfully explored the effect of the CFJ airfoil injection mass flow rate, injection height and injection jet velocity on the aerodynamic coefficients . Its concluded that the jet velocity plays a significant role in influencing aerodynamic performance. This research also successfully calculated the power consumption of the various design of CFJ airfoils. The power consumption the CFJ airfoil can be reduced by the total pressure ratio changes across the slots and injection Jet mass flow rate 84

85. LIST OF PUBLICATIONS ARISING FROM THE WORK Journal publication 1. Vigneswaran, C. M., & Kumar GC, V. (2021). Aerodynamic performance analysis of co-flow jet airfoil.  International Journal of Aviation, Aeronautics, and Aerospace ,  8 (1), 10. (Scopus indexed (Q3)) 2. Vigneswaran, C. M., & Kumar, G. V. (2023). Numerical investigation of the co-flow jet airfoil on aerodynamic performance.  Progress in Computational Fluid Dynamics ,  23 (3), 163-169. (SCI & Scopus indexed (Q3)) 3. Vigneswaran, C. M., & VishnuKumar, G. C. (2023). Computational analysis of influence of CFJ components aerodynamic performance.   Physics of Fluids ,  35 (9). (SCI & Scopus indexed (Q1)) Conference publication 4. Vigneswaran, C. M., & Kumar, G. V. (2022). Numerical analysis of co flow jet airfoil on enhancement of aerodynamic performance.  Materials Today: Proceedings , 82, 103-107. (Scopus indexed) 5. Vigneswaran, C. M., & VishnuKumar, G. C. (2023). Computational analysis of influence of geometry on CFJ airfoil aerodynamic coefficients. In  Journal of Physics: Conference Series IOP Publishing , 2484(1), 012042. (Scopus indexed) 85

86. REFERENCES   1. Abdolamir B khoshnevis , Shima Yazdani et al. (2020) ‘Analysis of co flow jet effects on airfoil at moderate Reynolds number’, Journal of Theoretical and Applied Sciences , Warsaw.   2. Abdolamir Bak Khoshnevis , Shima Yazdani & Erfan Salimipour . (2020) ‘Effects of CFJ flow control on aerodynamic performance of symmetric NACA airfoils’, Journal of Turbulence , 21:12, 704-721, DOI:10.1080/14685248.2020.1845911.   3. Abinav R., Nair N.R., Sravan P., Kumar P., Nagaraja S.R. (2016) ‘CFD analysis of co flow jet airfoil’, Indian Journal of Science and Technology , 9, 45   4. ANSYS ® Fluent User’s Guide, Release Version 18.1, Inc.   5. Baoyuan Wang, Bahaa Haddoukessouni , Jonathan Levy, and Ge -Cheng Zha. (2007) ‘Numerical investigations of injection slot size effect on the performance of co-flow jet airfoil’, University of Miami Publications, AIAA 2007-4427.     86

87. 6. Hossain Md. A., Uddin Md. N., Islam Md. R., Mashud M. (2015) ‘Enhancement of aerodynamic properties of an airfoil by co flow jet (CFJ) flow’, American Journal of Engineering Research , 4.1   7. Jacobs, E., & Sherman A. (1937) ‘Airfoil section characteristics as affected by variations of the Reynolds number’, Report number NACA-TR-586. https://ntrs.nasa.gov/citations/19930091662   8. Patankar , S.V. (1980) ‘ Numerical heat transfer and heat flow’ , Taylor and Francis, ISBN 978-3-540-42074-3 .   9. Patankar , S. V. and Spalding, D.B. (1972), ‘A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flows’, International Journal of Heat and Mass Transfer , Volume 15, Issue 10, Pages 1787-1806.   10. Sai Likitha Siddanathi . (2016) ‘Application of coflow jet concept to aircraft lift increase’, IJAMAE , Volume 3, Issue 1. 87

88. 11. Ge -Cheng Zha, Bruce F. Carroll, Adam Wells, Craig D. Paxton. (2005) ‘High performance airfoil using co-flow jet flow control’, AIAA Paper 2005-1260   12. Ge -Cheng Zha, Wei Gao , Craig D. Paxton, Alexis Palewicz . (2006) ‘Numerical investigations of co-flow jet airfoil with and without suction’, AIAA Paper 2006-1061 13. Spalart, P.R, Allmaras , S.R. (1992) ‘A one equation turbulence model for aerodynamic flows’, AIAA 92-0439.    14. Zha G., Paxton C. (2004) ‘A novel airfoil circulation augment flow control method using co- flow jet’, 2nd AIAA Flow Control Conference , Portland, Oregon. 15. Zha G., Paxton C., Conley C.A., Wells A., Carroll B.F. (2006) ‘Effect of injection slot size on the performance of coflow jet airfoil’, Journal of Aircraft , 43, 4, 987-995 88

89. 16. Zha G., Gao W., Paxton C.D. (2007) ‘Jet effects on coflow jet airfoil performance’, AIAA Journal , 45, 6, 1222-1231   17. Zhi H, Zhenhao Zhu, Yujin Lu, Deng S, Tianhang Xiao. (2021) ‘Aerodynamic performance enhancement of co-flow jet airfoil with simple simple high-lift device, Chinese Journal of Aeronaut ics, https://doi.org/10.1016/j.cja.2021.01.011 18 . Numerical Study on the Aerodynamic Characteristics of the NACA 0018 Airfoil at Low Reynolds Number for Darrieus Wind Turbines Using the Transition SST Model, MDPI 89

90. INTELECTUAL INTERARACTIONS 90

91. THANK YOU 91

92. APPENDIX 92

93. TABLE -2 RESULTS FOR PART A 93 sl no Description m dot inj (kg/s) H inj (m) V inj (m/s) stalling angle Cl max Cl/Cd power(watts) 1 suction slot at 82% of C & injection slot varies from 6% to 13% of C 6% of c 0.15 0.0021 57.7 15 1.42 17.6 195.6 2 7% of c 0.15 0.0021 57.7 15 1.50 18.5 184.2 3 8% of c 0.15 0.0021 57.7 15 1.57 19.4 177.7 4 9% of c 0.15 0.0021 57.7 16 1.61 19.8 182.1 5 10% of c 0.15 0.0021 57.7 16 1.65 20.3 180.0 6 11% of c 0.15 0.0021 57.7 18 1.72 21.2 193.6 7 12% of c 0.15 0.0021 57.7 18 1.77 21.8 183.7 8 13% of c 0.15 0.0021 57.7 18 1.81 22.4 189.7 9 suction slot at 85% of C & injection varies from 6% to 13% of C 6% of c 0.15 0.0021 57.7 14 1.41 22.9 212.6 10 7% of c 0.15 0.0021 57.7 15 1.46 17.7 221.9 11 8% of c 0.15 0.0021 57.7 15 1.53 23.1 200.1 12 9% of c 0.15 0.0021 57.7 16 1.57 21.0 193.9 13 10% of c 0.15 0.0021 57.7 17 1.60 18.7 205.5 14 11% of c 0.15 0.0021 57.7 17 1.66 22.1 214.8 15 12% of c 0.15 0.0021 57.7 17 1.73 19.7 211.9 16 13% of c 0.15 0.0021 57.7 18 1.78 22.0 201.7 17 suction height varies and slot locate at 82% of c 0.5*H inj 0.15 0.0021 57.7 17 1.85 25.7 1464.9 18 1*H inj 0.15 0.0021 57.7 17 1.81 31.8 509.6 19 1.5*H inj 0.15 0.0021 57.7 17 1.73 25.0 324.1 20 2*H inj 0.15 0.0021 57.7 17 1.66 23.0 269.1 21 2.5*H inj 0.15 0.0021 57.7 16 1.61 22.3 172.1 22 suction height varies and slot locate at 85% of c 0.5*H inj 0.15 0.0021 57.7 17 1.83 26.3 1554.5 23 1*H inj 0.15 0.0021 57.7 17 1.77 22.0 582.7 24 1.5*H inj 0.15 0.0021 57.7 17 1.72 20.9 380.4 25 2*H inj 0.15 0.0021 57.7 17 1.64 19.2 299.2 26 2.5*H inj 0.15 0.0021 57.7 16 1.57 21.0 218.4

94. TABLE -2 RESULTS FOR PART B 94 sl no Description m dot inj (kg/s) H inj (m) V inj (m/s) stalling angle Cl max Cl /Cd Power (watts) 27 CASE 1A3 0.125 0.0021 48.1 15 1.31 22.6 132.3 28 1A4 0.144 0.0021 55.6 15 1.47 25.7 148.9 29 1A5 0.161 0.0021 62.1 18 1.82 21.2 217.2 30 1B3 0.102 0.0014 58.9 15 1.53 28.1 120.0 31 1B4 0.118 0.0014 68.0 19 1.90 29.0 253.3 32 1B5 0.132 0.0014 76.1 18 2.03 37.4 270.7 33 2A3 0.12 0.0020 50.2 16 1.34 26.8 147.9 34 2A4 0.12 0.0015 66.9 18 1.84 30.9 187.3 35 2A5 0.12 0.0012 79.2 19 2.13 36.3 263.8 36 2B3 0.1 0.0014 60.2 15 1.57 28.1 119.9 37 2B4 0.1 0.0010 80.2 19 2.12 35.9 268.0 38 2B5 0.1 0.0008 100.3 19 2.22 36.2 373.3 39 2C3 0.11 0.0016 54.7 15 1.51 20.3 135.8 40 2C4 0.11 0.0012 73.0 19 2.00 28.1 262.0 41 2C5 0.11 0.0010 88.5 19 2.14 36.6 340.5 42 3A3 0.102 0.0014 61.2 15 1.57 28.7 126.8 43 3A4 0.131 0.0017 61.2 17 1.68 20.3 222.0 44 3A5 0.164 0.0022 61.2 18 1.80 21.0 256.9 45 3B3 0.098 0.0012 64.6 17 1.72 26.6 144.8 46 3B4 0.13 0.0016 64.6 18 1.80 24.3 230.2 47 3B5 0.155 0.0020 64.6 19 1.90 23.9 262.4 48 3C3 0.088 0.0011 68.0 17 1.75 30.3 159.1 49 3C4 0.118 0.0014 68.0 19 1.90 22.6 239.3 50 3C5 0.147 0.0018 68.0 19 1.94 27.9 251.6