The impact of vertical wing placement on the wave drag and sonic-boom performance at supersonic speeds

The impact of vertical wing placement on the wave drag and sonic-boom performance at supersonic speeds

Kinderman, Hendrik Wisse (TU Delft Aerospace Engineering)

Schrijer, F.F.J. (mentor)

Delft University of Technology

Aerospace Engineering

2017-12-19

This research project aims at obtaining a better understanding of vertically translating the wing and the related wing-body interference effects on the drag and sonic boom. Computational Fluid Dynamics (CFD) analysis using the Euler equations has been used to evaluate an airplane with different vertical wing placements at a lift coefficient of 0.15 at a Mach-number of 1.6 and also in zero-lift conditions. Pressure distributions, drag forces and pressure signatures have been calculated in order to assess the performance in terms of wave drag and sonic booms. These results have been analysed to find out why certain effects are happening for these configurations. The low wing configuration has the highest lift-to-drag ratio due to interference on the upper wing surface close to the fuselage. The lift-to-drag ratio for CL = 0.15 is found to be 4.79% higher compared to the worst performing configuration, the high wing configuration. Due to the local geometry of the low wing configuration it is possible to cre- ate additional suction on the upper wing surface, which positively affects the performance. Pressure signatures are extracted at 1 body-length distance (70푚) from the aircraft for several azimuth angles. These distributions show that the low wing configuration also has the lowest impulse and maximum overpressure. The higher wing configurations show an extra peak in overpressure emanating from the trailing end of the wing, which is created due to interference effects. Below the wing surface there is a large volume of the fuselage, while it is absent for the low wing configuration. Therefore the higher wing configurations show an extra peak in the pressure signature.
Next to this discovery, an analysis is presented to relate the geometry of the configurations to the wave drag by assessing the cross-sectional area distribution using different intersection methods. These methods are compared with other methods found in the literature. Two methods which use a single Mach-cone have been analysed, as well as a method incorporating a forward and a backward pointed Mach-cone. One method translates a Mach-cone vertically to align the vertex of the Mach-cone with the centroid of the intersection with the aircraft. This gives an x,z-position which can be used to adjust the area distribution. The drag for the methods using a single Mach-cone was overestimated by a factor of 2, but after multiplying these results by a factor of / the results for the heigh-weighted Mach-cone method approached the wave drag results from CFD within 5%. The double Mach-cone method showed an even better agreement with less variation, while no multiplication factor was applied.
A further analysis has taken place to find out why some methods that incorporate a single Mach- cone to evaluate the cross-sectional area to calculate the wave drag, overestimate the drag by a factor of 2. It is found that these methods do not overestimate the drag for a simple shape, such as a Sears- Haack body. The methods simply overestimate the cross-sectional area, which needs smoothing to obtain an area distribution that is suitable for drag calculation. The double Mach-cone method is a method that smoothens the area distribution, since the forward cone lowers the cross-sectional area in the front of an aircraft and adds cross-sectional area in the tail part of the aircraft.
Further research is required to find out if these methods using a single Mach-cone can be applied to any geometry or not. Next to that it is recommended to research the sonic boom of other aircraft configurations with wings shifted further back to see if the sonic-boom from the tail can be reduced. Further research is necessary to see if the interference effects on the upper side of the wing of the low wing configuration are present in viscous flows. If the positive interference effects from this thesis are present in a viscous flow, this might see a reduction in fuel burn and maybe contribute to commercial supersonic flight becoming a reality again.

sonic boom
vertical wing placement
wave drag
drag
supersonic
pressure signature
lift
zero-lift
area ruling
area rule
Mach
cone

http://resolver.tudelft.nl/uuid:b5eaa808-6067-46a5-8d45-0e14d18ceeef

Student theses

master thesis

© 2017 Hendrik Wisse Kinderman