Aerodynamic Characteristics Estimation of Variable Geometry Airfoil in Supersonic Air Flow

master's thesis

• Title (croatian): Proračun aerodinamičkih karakteristika aeroprofila promjenjive geometrije u nadzvučnoj struji zraka
• Author: Leo Matak
• Mentor: Karolina Krajček Nikolić (mentor)
• Committee member: Doris Novak (predsjednik povjerenstva)
• Committee member: Davor Franjković (član povjerenstva)
• Committee member: Anita Domitrović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Transport and Traffic Sciences; (Division of Aeronautics); (Department of Aeronautics); Zagreb
• Defense date and country: 2021-05-04, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Traffic and Transport Technology; Air Traffic

Abstract

The primary objective of this research project is to evaluate the aerodynamics behavior of the NACA 64A-204 airfoil used in the F-16 wings. The reason for selecting the F-16 wing, and therefore the airfoil used in the wing, is the characteristic behavior of in-flight changes to the airfoil geometry. The changes are made by deflecting the leading and trailing edge flaps which result in changing the wing and airfoil geometry. Two approaches were selected for obtaining the results. Linearized supersonic airfoil theory and Computational Fluid Dynamics. Linear theory offers concise results but with certain limitations, such as thin airfoil and small angles of attack. CFD solves for full Navier-Stokes equations taking into account viscosity, wall shear and stresses; which are not found in the linear theory terms. Lift coefficient values obtained are very similar for both approaches, what differs them is the drag value. As expected, the CFD approach gives higher values for drag. However, it is worth noting how the linear theory offers almost identical results for both drag and lift values under certain conditions which do not go over the imposed limitations. The paper reveals how the change in the airfoil geometry, when going from subsonic to supersonic flight, affects the lift to drag ratio. It is shown how for supersonic flight regime the supersonic flight configuration provides over 10% higher value for CL/CD ratio at 1-degree angle of attack based on the CFD results, and over 6% higher value for the same conditions based on the linear theory. Such an increase is detrimental for combat aircraft which rely on afterburner and heavy fuel consumption.

Abstract (croatian)

Cilj ovog rada bio je procjena promjene aerodinamičkih karakteristika aeroprofila NACA 64A-204 korištenog u krilima borbenog zrakoplova F-16. Razlog odabira krila F-16 jest njegova mogućnost promjene geometrije krila tijekom leta. Mjenjajući položaj prednjih i stražnjih krilaca zrakoplov ima mogućnost promjene zakrivljenosti aeroprofila, pa tako i krila. Dva su pristupa korištena za proračune koeficijenata. Linearizirana teorija nadzvučnog aeroprofila i metode Računalne Dinamike Fluida (CFD). Linearna teorija pruža dosta točne rezultate ali pri određenim ograničenja kao što su – tanki aeroprofili i mali napadni kutovi. Računalna dinamika fluida nema takvih ograničenja, i rezultate dobiva rješavajući kompletne Navier-Stokes jednadžbe uzimajući u obzir sile viskoznosti, trenja i naprezanja. Rezultati dobiveni za koeficijente uzgona dosta su slični u oba pristupa, ono što ih razlikuje su vrijednosti koeficijenta otpora. Očekivano, CFD pristup daje veće vrijednosti otpora. Međutim, bitno je istaknuti kako linearna teorija pruža gotovo identične rezultate i za uzgon i za otpor pri određenim uvjetima koji ne idu iznad ograničenja teorije. Na kraju rada prikazano je kako i koliko utječe promjena u geometriji aeroprofila pri prelasku iz podzvučnog u nadzvučan let. Pokazano je kako za režim nadzvučnog kruziranja konfiguracija sa smanjenom zakrivljenosti – konfiguracija za nadzvučno kruziranje – pruža i preko 10% veći odnos Cl/Cd za napadni kut od 1 stupanj na temelju CFD rezultata, i preko 6% veći odnos predviđen linearnom teorijom za iste uvjete. Za borbene zrakoplove koji dosta zavise o potrošnji goriva i korištenju učinaka afterburner-a, takvo povećanje je dosta bitno.

• Keywords: F-16; NACA 64A-204; Supersonic linear airfoil theory; cambered airfoil; CFD
• Keywords (english): F-16; NACA 64A-204; linearna teorija nadzvučnog aeroprofila; zakrivljeni aeroprofil; računalna dinamika fluida
• Language: english
• URN:NBN: urn:nbn:hr:119:135218
• Study programme: Title: Aeronautics; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka aeronautike (magistar/magistra inženjer/inženjerka aeronautike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-06-08 14:41:01