Analysis of Swept and Unswept Wings in Subsonic and Supersonic Flows 

G- Meet Link: https://meet.google.com/bvq-xunh-qdr?hs=224
 
Mentors: 

• Pratheek C Bandigedi 

• R M Deva Adhithiyan 

Mentees: 

• Ayushman Rastogi 

• Aryan Subramanian 

Summary: 

Two variations of wing models, employing the NACA 65A204 airfoil, have been created using SolidWorks/Fusion360. Computational Fluid Dynamics (CFD) simulations utilizing ANSYS Fluent have been conducted on both wing designs across subsonic (Mach number < 1) and supersonic (Mach number > 1) speeds. The drag, lift, coefficient of drag (Cd), and coefficient of lift (Cl) values were then calculated and analysed through plotted graphs. 

Aim:  

The aim of the project is to assess the superior aerodynamic performance of swept wings, particularly at supersonic speeds, with a focus on reduced drag and increased speed. This evaluation will be conducted through comparative analysis of drag, lift, coefficient of drag (Cd), and coefficient of lift (Cl) between swept and unswept wing configurations using CFD simulations on ANSYS Fluent. 

Introduction: 

As aircraft have progressed to higher speeds, nearing the speed of sound, the formation of shockwaves on wing surfaces has led to increased drag, necessitating additional thrust to maintain velocity. To enable supersonic flight, wing designs have been angled in a swept configuration, which results in a slower local airflow and reduced pressure compared to unswept wings. This strategic sweeping allows aircraft to achieve higher speeds before encountering shockwave formation, enabling flight at velocities exceeding Mach 1. 

Wing sweep, a technique implemented to mitigate the adverse effects of local supersonic flows during high-velocity flight, serves to alleviate the detrimental impact of shockwaves caused by said flows on an aircraft's aerodynamic performance. By sweeping the wing backward, the incoming airflow can be delineated into two distinct components: one flowing over the airfoil and another traversing along the wing's leading-edge perpendicular to the airfoil. While the former contributes to both lift and drag generation, the latter has negligible aerodynamic influence. In subsonic regimes for swept wings, the utilization of only a fraction of the incoming airflow results in diminished lift production compared to unswept wings. However, as velocities approach and surpass the speed of sound, the reduced airspeed over the airfoil in a swept wing confers an advantage by impeding the rapid escalation of drag experienced by unswept configurations. Theoretical postulations of these principles are to be empirically validated throughout the course of this project. 

Methodology: 

Coordinates of the NACA 65A204 airfoil were plotted, and wing geometries were modelled using CAD software such as SolidWorks/Fusion360. 

These designs were then imported into ANSYS Fluent in Design Modeller, where a cuboidal fluid domain was established along with a Body of Influence. 

Subsequently, the mesh was generated featuring named sections like inlet, outlet, wing, and wall with conditions optimised to strike a balance between computational power and result accuracy. 

Following this, the setup was completed, with conditions outlined as listed below. 

Solver:  

Density Based  

Steady State  

Absolute Velocity Formulation  

Model: Energy On Viscous K-Omega SST  

 
Material:   

Fluid: Air (Ideal Gas, Viscosity Model: Sutherland)  

 
Boundary Conditions:  

Inlet: Velocity Inlet [ 206m/s (M 0.6), 343m/s (M 1.0), 480m/s (M 1.4)]  

Outlet: Pressure Outlet  

Wall: Pressure Far Field [Mach Values: 0.6, 1.0, 1.4]  

Wing: Wall  

Reference Values: Area = 0.135 m^2 (Wing Area)  

 
Definition Reports: CL, Lift, CD, Drag 

Initialization: Standard   

Upon conducting simulations and confirming graph convergence, pressure contours were obtained, and graphs depicting coefficient of drag (Cd), coefficient of lift (Cl), lift, and drag were analysed, with the lift and drag values calculated using function calculators in ANSYS. 

Results (Pressure contours and Plots): 

Swept Wing at Mach 0.6 

      

                                 

Swept Wing at Mach 1.4 

 

    

                                             

Unswept Wing at Mach 0.6 

    

                               

 

Unswept Wing at Mach 1.4 

 

Quantities	Swept		Unswept
	Mach 0.6	Mach 1.4	Mach 0.6	Mach 1.4
Lift (N)	418.284	540.723	1231.78	-
Drag (N)	24.0475	302.923	52.9057	-
L/D (Lift to Drag Ratio)	17.42	1.79	23.28	-

 
( - ): Indicates values couldn’t be extracted from simulations 

 

Conclusion: 

Following successful CFD simulations of the Swept back wing, we confirmed alterations in the L/D ratio transitioning from subsonic to supersonic flow. Our findings supported our theoretical comprehension of the wing sweep effect, showcasing an improved L/D ratio for unswept wings at subsonic velocities. Additionally, under supersonic conditions, we noted a simulation breakdown with unswept wings, yielding inconclusive outcomes. This discrepancy underscores the unsuitability of unswept wings in supersonic environments. 

References: 

A Comparison of the Experimental Aerodynamic Characteristics of an Oblique Wing with Those of a Swept Wing – NASA Technical Memorandum  

(NASA TM X-3547) 

 

An Experimental Investigation of Three Oblique-wing And Body Combinations at Mach Numbers Between 0.60 And 1.40 - NASA Technical Memorandum 

(NASA TM X-62,256) 

 

 

 

 

Report prepared on May 10, 2024, 11:48 a.m. by:

• R M Deva Adhithiyan [Piston]
• Pratheek Bandigedi [Piston]

Report reviewed and approved by Nikesh Shetty [Piston] on May 10, 2024, 5:03 p.m..