TY  - JOUR
A1  - Götten, Falk
A1  - Havermann, Marc
A1  - Braun, Carsten
A1  - Marino, Matthew
A1  - Bil, Cees
T1  - Improved Form Factor for Drag Estimation of Fuselages with Various Cross Sections
JF  - Journal of Aircraft
N2  - The paper presents an aerodynamic investigation of 70 different streamlined bodies with fineness ratios ranging from 2 to 10. The bodies are chosen to idealize both unmanned and small manned aircraft fuselages and feature cross-sectional shapes that vary from circular to quadratic. The study focuses on friction and pressure drag in dependency of the individual body’s fineness ratio and cross section. The drag forces are normalized with the respective body’s wetted area to comply with an empirical drag estimation procedure. Although the friction drag coefficient then stays rather constant for all bodies, their pressure drag coefficients decrease with an increase in fineness ratio. Referring the pressure drag coefficient to the bodies’ cross-sectional areas shows a distinct pressure drag minimum at a fineness ratio of about three. The pressure drag of bodies with a quadratic cross section is generally higher than for bodies of revolution. The results are used to derive an improved form factor that can be employed in a classic empirical drag estimation method. The improved formulation takes both the fineness ratio and cross-sectional shape into account. It shows superior accuracy in estimating streamlined body drag when compared with experimental data and other form factor formulations of the literature.
Y1  - 2020
U6  - http://dx.doi.org/10.2514/1.C036032
SN  - 1533-3868
SP  - 1
EP  - 13
PB  - AIAA
CY  - Reston, Va.
ER  - 
TY  - JOUR
A1  - Götten, Falk
A1  - Finger, Felix
A1  - Havermann, Marc
A1  - Braun, Carsten
A1  - Marino, M.
A1  - Bil, C.
T1  - Full configuration drag estimation of short-to-medium range fixed-wing UAVs and its impact on initial sizing optimization
JF  - CEAS Aeronautical Journal
N2  - The paper presents the derivation of a new equivalent skin friction coefficient for estimating the parasitic drag of short-to-medium range fixed-wing unmanned aircraft. The new coefficient is derived from an aerodynamic analysis of ten different unmanned aircraft used for surveillance, reconnaissance, and search and rescue missions. The aircraft is simulated using a validated unsteady Reynolds-averaged Navier Stokes approach. The UAV’s parasitic drag is significantly influenced by the presence of miscellaneous components like fixed landing gears or electro-optical sensor turrets. These components are responsible for almost half of an unmanned aircraft’s total parasitic drag. The new equivalent skin friction coefficient accounts for these effects and is significantly higher compared to other aircraft categories. It is used to initially size an unmanned aircraft for a typical reconnaissance mission. The improved parasitic drag estimation yields a much heavier unmanned aircraft when compared to the sizing results using available drag data of manned aircraft.
KW  - Parasitic drag
KW  - UAV
KW  - CFD
KW  - Aircraft sizing
Y1  - 2021
U6  - http://dx.doi.org/10.1007/s13272-021-00522-w
SN  - 1869-5590 (Online)
SN  - 1869-5582 (Print)
N1  - Corresponding author: Falk Götten
VL  - 12
SP  - 589
EP  - 603
PB  - Springer
CY  - Berlin
ER  -