Numerical Simulation of Effect Modification of Single Slotted Flap on Wing Cessna C208B Grand Caravan for Aerodynamic Performance

Numerical Simulation of Effect Modification of Single Slotted Flap 5 Fig. 1. Wing geometry in simulation Fig. 2. Single-slotted flap geometry in simulation Fig. 3. Simulation Domain and Boundary Condition 2.2 Grid Independence Test The use of simulation software requires data accuracy both at the pre-processing and post- processing stages. The grid-independent test stage is needed to find out and determine the most efficient grid structure and level for modeling results close to the actual conditions [12]. This independent grid test is carried out for meshing which tends to be constant, the number of meshing is divided into several types, then from this type of meshing the smallest value of each meshing will be found by comparing numerical C D graphs. The number of meshing is divided into 10 types. Table 1 shows the comparison of the values C D generated from ten types of meshing. One of the considerations used in a numerical simulation is a low and constant C D value. So in this simulation, Mesh 5 will be used as a reference for the next simulation according to Anderson’s [13] criterion. 6 S. Yusuf et al. Table 1. Grid Independence Test Analysis on Test Object without Flap Jenis Mesh Element Node Drag (N) C D Meshing 1 2973528 536344 551.932 0.007103 Meshing 2 3144327 567622 551.113 0.007093 Meshing 3 3342603 603273 552.029 0.007105 Meshing 4 3579492 646215 554.961 0.007142 Meshing 5 3985830 719004 552.925 0.007116 Meshing 6 4345541 783368 553.072 0.007118 Meshing 7 4776373 861801 554.978 0.007027 Meshing 8 5308558 957603 554.463 0.007156 Meshing 9 5830581 1049415 551.257 0.007002 Meshing 10 6472375 1090534 552.242 0.007157 3 Result and Discussion This result will be discussed through the coefficient of lift, coefficient of drag, and coefficient of lift-to-drag ratio. In addition, it also discusses the visualization of the contour coefficient pressure, velocity, and vorticity magnitude. So based on the analysis of the numerical simulation results, the aerodynamic performance and its characteristics will be obtained. 3.1 Coefficient of Lift Figure 4 shows a graph between the coefficient of lift and the angle of attack at the flap angle (αF ) = 0º, 15º, and 30º. It can be seen that the flap angle has a significant effect on the C L value of the wing Cessna 208b Grand Caravan. Comparison of the C L values of the flap angle (αF ) 0º, 15º, and 30º to the angle of attack provides information that an increase in the flap angle can increase production at a low angle of attack. However, increasing the flap angle can reduce the maximum C L. It can be seen that the variation αF = 0º can produce the highest maximum C L value than other variations, which is 0.7336. And experienced the longest loss of lift or stall, which occurred at αF = 18º. While the lowest maximum C L value is generated by variation αF = 30º, which is 0.630 at αF = 14º. Even though it produces the lowest maximum C L value, this variation can produce a greater C L value than the variation at a low angle of attack. 3.2 Coefficient of Drag Figure 5 shows the graph between C D and the angle of attack on the variation of the flap angle (αF ) positioned at 0º, 15º, and 30º. The graph has provided information that the flap angle has a significant effect on the C D value of the Cessna 208b Grand Caravan wing. Numerical Simulation of Effect Modification of Single Slotted Flap 7 Fig. 4. Lift coefficient at Flap Angle (αF ) 0º, 15º, and 30º Fig. 5. Drag coefficient at Flap Angle (αF ) 0º, 15º, and 30º. The addition of the flap angle also affects the C D value significantly. It can be seen that the use of an αF = 30º flap angle produces the highest C D value. This indicates that the greater the addition of the flap angle, the more the resulting C D value will increase. This pattern is similar to the research conducted by Hussein et al. [14]. This is caused by increasing the flap angle, the greater the outer cross-section which is perpendicular to the direction of airflow. 3.3 Lift to Drag Ratio Figure 6 shows a graph between C L/C D and the angle of attack at various flap angles (αF ) positioned at 0º, 15º, and 30º. It can be seen that the variation of the flap angle 0º produces the largest C L/C D value of 13.65 when the angle of attack is at 8º. And at the angle of attack after that, the performance decreased due to the addition of the resulting drag force. While the variation of the 15° flap angle, continues to decrease in 8 S. Yusuf et al. Fig. 6. Lift to Drag ratio at Flap Angle (αF ) 0º, 15º, and 30º value C L/C D as the angle of attack increases. However, the αF = 15° flap angle variation can produce a value C L/C D better than the αF = 0° at the 0° angle of attack. The same pattern occurs in the αF = 30° flap angle with a value of C L/C D higher than the αF = 15° flap angle. Therefore, the flap angle of αF = 30° is good to use during take-off flight conditions because it produces the most optimal C L/C D value at a 0° angle of attack. The graph shows that the use of flap angle can affect the value of C L/C D generated. Although the use of flaps can provide an additional C L value, the C D value will also increase as the flap angle used increases. At a low angle of attack, the addition of the flap angle has helped to generate additional lift which increases the value of C L/C D. However, as the angle of attack increases, the value of C L/C D continues to decrease due to the increase in the resulting drag. 3.4 Velocity Contour When the flap angle is positioned at αF = 15° with the same angle of attack, there is an increase in the velocity difference between the top and bottom surfaces. This causes the addition of the C L value as well as C D. And when the flap angle is increased to αF = 30°, airflow and turbulent separation occur only at the top of the flap. The point of airflow separation is depicted by a dark blue contour with a certain area. Meanwhile, turbulent flow is indicated by an irregular streamlined direction. This is due to the increasing cross-sectional area perpendicular to the direction of the airflow so that the momentum of the incoming airflow through the gap cannot delay the separation point. The comparison of the wing with the flap angle positioned at αF = 30° can be identified by three angles of attack, namely α = 0°, 8°, and 16°. At an angle of attack of α = 0°, there is little point of separation or turbulent flow. This is depicted by a blue contour area located in the upper area of the flap. When the angle of attack is positioned at α = 8°, the airflow separation area is slightly widened to the center of the top surface of the wing. However, the characteristics of the streamlined direction have not shown significant difference from the α = 0° angle of attack. And when the angle of attack is positioned at αF = 30°, there are significant differences that occur in both contour color Numerical Simulation of Effect Modification of Single Slotted Flap 9 Fig. 7. Velocity contour at Wing Cessna 208b Grand Caravan with Variasi Single Slotted Flap and streamline characteristics. The area of airflow separation is widened to occur in the maximum chamber airfoil and is followed by turbulent flow in the blue contour area. Meanwhile, the momentum of the airflow entering the gap from the flap is not able to delay the separation point. Based on the simulation results, it can be seen that the addition of the flap angle greatly affects the aerodynamic characteristics of the high angle of attack. The larger the flap angle used, the greater the separation. The point of stagnation is getting further away from the leading edge as the angle of attack increases. However, with increasing the flap angle for the same angle of attack, the flow separation increases significantly. For αF = 0° flap angle, the flow separation (blue zone on the left) at an angle of attack of α = 16° is less than that of αF = 15° and 30° flap angle (Fig. 7). 3.5 Pressure Coefficient Contour The pressure contour in Fig. 8 changes as the flap angle increases. The most significant area of pressure change is the leading edge area on the upper surface airfoil. This event is explained by variation αF = 30º; α = 16º which experienced a significant difference in pressure between the leading edge and trailing edge of the wing surface. With the flaps that are deflected by 15º and 30º, it seems as if the velocity at the bottom of the airfoil is slowed, while at the top of the airfoil the fluid velocity is accelerated resulting in a low-pressure coefficient in that area. Where the leading edge of the airfoil is blue and the trailing edge is red. 10 S. Yusuf et al. Fig. 8. Pressure Coefficient Contour on the Cessna 208b Grand Caravan wing with single slotted flap variation Numerical Simulation of Effect Modification of Single Slotted Flap 11 Fig. 8. (continued) At α = 16º with the flap angle positioned to αF = 0º, there is a low-pressure formation in the leading edge area which is shown in solid blue. However, when the flap angle is positioned at αF = 15º the low-pressure area widens and an increase in pressure occurs in the trailing edge area. And when the flap angle is enlarged to αF = 30º there is an expansion of the minimum pressure area with inconsistent contours. This indicates the occurrence of airflow separation or large turbulence experienced by the airflow after passing through the wing surface. The existence of these events is reinforced by significant impairment in C L value. 3.6 Vorticity Magnitude Contour In Fig. 9, the contours of the vorticity magnitude are shown by flap angles of αF = 0°, 15°, and 30° and angles of attack at α = 0°, 8°, and 16° in the midspan wing area. The red contour shows a high vorticity value while the green color indicates a low vorticity value. At a flap angle of αF = 0° and an angle of attack of α = 0°, strong vortices are formed with a length of less than half the chord length behind the wing. When the angle of attack is positioned at α = 8°, the area is extended. 12 S. Yusuf et al. Fig. 9. Vorticity Magnitude Contour on the Cessna 208b Grand Caravan wing with single slotted flap variation Based on the simulation results, it provides information that the addition of the angle of attack and flap angle can produce varying induce drag. The higher the angle of attack or flap angle used, the greater the induced drag generated. This greatly affects the value. 4 Conclusion Numerical simulation of the effect of single-slotted flap modification on the Cessna C208b Grand Caravan wing on aerodynamic performance resulted in the following conclusions. 1. Comparison of C L values for flap angles αF = 0º, 15º, and 30º to the angle of attack provides information that increasing flap angle can increase C L production at a low angle of attack. However, increasing the flap angle can reduce the maximum C L. 2. The addition of the flap angle also significantly affects the C D value. It can be seen that the use of an αF = 30º flap angle produces the highest C D value. This indicates that the greater the addition of the flap angle, the more the resulting C D value will increase. 3. Although the use of flaps can provide additional C L value, the C D value will also increase as the flap angle used increases. At a low angle of attack, the addition of the flap angle has helped to generate additional lift which increases the value of C L/C D. However, as the angle of attack increases, the value of C L/C D continues to decrease due to the increase in the resulting drag Numerical Simulation of Effect Modification of Single Slotted Flap 13 4. The pressure contour changes as the flap angle increases. The most significant areas of pressure changes are the leading edge and upper surface areas, especially the maximum chamber airfoil. 5. The larger the flap angle used, the greater the separation. The point of stagnation is getting further away from the leading edge as the angle of attack increases. However, with increasing the flap angle for the same angle of attack, the flow separation increases significantly. 6. Based on the simulation results, it provides information that the addition of the angle of attack and flap angle can produce varying induce drag. The higher the angle of attack or flap angle used, the greater the induced drag generated. This greatly affects the value of the C D References 1. J. Duncan, Pilot ’ s Handbook of Aeronautical Knowledge, Pilot. Handb. Aeronaut. Knowl. (2016) 524. 2. J.D. Anderson, Fundamentals of Aerodynamics (6th edition), McGraw-Hill, 2011. 3. K. Biber, Stall Hysteresis of an Airfoil with Slotted Flap, 42 (2005). 4. J. Chapman, Numerical Investigation of Flow Characteristics of a Slotted NACA 4414 Air- foil Numerical Investigation of Flow Characteristics of a Slotted NACA 4414 Airfoil, (2019). 5. D. Foster, H. Irwin, B. Williams, The Two-Dimensional Flow Around a Slotted Flap, Aeronaut. Res. Counc. Reports Memo. 3681. (1971). 6. C. Velkova, M. Todorov, Study of The Influence of A Gap between The Wing and Slotted Flap on The Aerodynamic Characteristics of Ultra-Light Aircraft Wing Airfoil, (2015). 7. C. Velkova, M. Todorov, G. Durand, Study the Influence of a Gap between the Wing and Slotted Flap over the Aerodynamic Characteristics of Ultra-Light Aircraft Wing Airfoil, 5 (2015) 278–285. https://doi.org/10.17265/2159-5275/2015.05.002. 8. M.D. Todorov, Aerodynamic Characteristics of Airfoil with Single Slotted Flap for Light Airplane Wing, (2015). 9. S.P. Setyo Hariyadi, Sutardi, W.A. Widodo, I. Sonhaji, Numerical Study of Secondary Flow Characteristics on the Use of the Winglets, J. Phys. Conf. Ser. 1726 (2021). https://doi.org/ 10.1088/1742-6596/1726/1/012012. 10. N. Mulvany, L. Chen, J. Tu, B. Anderson, Steady-State Evaluation of Two-Equation RANS (Reynolds-Averaged Navier-Stokes) Turbulence Models for High-Reynolds Number Hydrodynamic Flow Simulations, Dep. Defence, Aust. Gov. (2004) 1–54. 11. S.P.S. Hariyadi, B. Junipitoyo, Sutardi, W.A. Widodo, Stall Behavior Curved Planform Wing Analysis with Low Reynolds Number on Aerodynamic Performances of Wing Airfoil Eppler 562, J. Mech. Eng. 19 (2022) 201–220. 12. S.P. Setyo Hariyadi, Sutardi, W.A. Widodo, M.A. Mustaghfirin, Aerodynamics Analysis of the Wingtip Fence Effect on UAV Wing, Int. Rev. Mech. Eng. 12 (2018). https://doi.org/10. 15866/ireme.v12i10.15517. 13. J.D. Anderson, J.D. Anderson Jr, Computational Fluid Dynamics The Basics with Applica- tions, 1995. https://doi.org/https://doi.org/10.1017/CBO9780511780066. 14. E.Q. Hussein, H.N. Azziz, F.L. Rashid, Aerodynamic Study of Slotted Flap for Naca 24012 Airfoil by Dynamic Mesh Techniques and Visualization Flow, J. Therm. Eng. 7 (2021) 230– 239. https://doi.org/10.18186/THERMAL.871989. 14 S. Yusuf et al. 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