OSTIV Congress Day 2

Aerodynamic Effects of the Canopy/Fuselage Gap on a modern Sailplane; A.S. Jonker, J.J. Bosman

R. Starke

The first presentation of the day was presented by Richard Starke. It was authored by A.S. Jonker, J.J. Bosman. In this work, the transition from laminar to turbulent of the flow over the front section of a fuselage was determined in flight experiments using an acoustic probe. It was found that transition was forced at the forward canopy gap on the upper surfaces, and was near the theoretical location on the lower surface of the fuselage. Further investigations were performed using computational fluid dynamics (CFD), and various gap sizes and inflow/outflow rates through the gap were considered. It was concluded that performance gains are achievable with a small gap and complete sealing, or a slightly negative cockpit pressure.

Refinement of glider aerodynamic design; J.J. Bosman

The next talk was given by Johan Bosman who used computational fluid dynamics (CFD) to increase the performance of the next generation 18-m class sailplane. In order to gain an additional 2 points of maximum glide ratio over current gliders, approximately 4 N of drag reduction are need, which is quite challenging at the current state of the art. Bosman looked at the improving the fuselage-wing combination and concluded that a high-wing configuration will provide roughly 3-N drag savings over a mid-wing configuration. Additional drags can be saved by properly placing inlet and outlets of the cockpit ventilation system. For example, an inlet near the leading edge of the wing root has some positive effects on the flow over the junction by removing a high-pressure spot. Further studies looked at vertical fin-tailboom junctions with more potential drag savings. Overall, an 18-m class glider with a maximum lift-to-drag ratio of 56 seems quite feasible.

Design of a Winglet for a Sailplane using a multi-objective evolutionary algorithm optimization method; F. Kody, S. Schmitz, and G. Bramesfeld

G. Bramesfeld

The first talk after the break was presented by Götz Bramesfeld. It was co-authored by Frank Kody and Sven Schmitz, and was entitled “Design of a Winglet for a Sailplane using a multi-objective evolutionary algorithm optimization method.” This presentation specifically detailed the approach to developing an evolutionary optimization design scheme. The tools developed were described, including a discussion of evolutionary algorithms. Although the winglet design example presented was driven for a single design point, thee result did perform well over a range of airspeeds. The new method shows promise for future design work.

Numerical Investigation of Wing-Winglet Juncture; J. Coder and M. Maughmer

M. Maughmer

The next presentation was given by Mark Maughmer who discussed recent comparison studies of experiments and predictions of various computational fluid dynamics (CFD). Whereas XFOIL, MSES, and Profil are relatively reliable in predicting the low drag region and maximum lift, modern CFD codes, such as Overflow, led to unsatisfactory results. Those inaccuracies are related mainly to problems with the prediction of transition from laminar to turbulent flow. Despite significant advancements in modeling transition behavior, more work is needed. Nevertheless, CFD analysis provides some insight that is not possible otherwise as shown with the simulated complex flow field at the round-out from wingtip to winglet, as shown in an example simulation of an 18-m Discuss.

The Penn State Human Powered Aircraft Project; M. Maughmer

Second to last talk was given by Mark Maughmer who provided an update on the activities of the “Akaflieg” Penn State and their Human Powered Aircraft. In 1989 Penn State University (PSU) adapted the Akaflieg concept to the aerospace curriculum as a response to engineering education shortcoming that was identified by the National Science Foundation. The PSU Sailplane Class balances aircraft fabrication and paper design studies to develop and maintain skill sets of engineering students. Over the decade several projects were pursued, including frequent designs for the AIAA Design , Build, Fly Competition. One of the more recent projects is a human powered airplane in persuit of the Kramer Flight Challenge. The aircraft has been built and flown successfully, although weighted and without an onboard pilot. Instead it was controlled by radio controlled. The aircraft empty weight is approximately 60 lbs and about 80 ft wingspan.

Estimating Wind Velocities from limited sailplane flight data; N. Zhang, R. Millane, E. Enevoldsen, J. Murray

The last talk of the day was about the estimation of wind speeds using GPS data and some airspeed data. With only ground speed and airspeed available one can show that the horizontal wind speed and direction can be estimated by flying two or more headings at different speeds through a circle-intersection method. In a similar approach, then wind speed can be estimated by using only GPS data. In this case, however, the airspeed constraints have to be known, for example stall and maximum allowable airspeed. Estimations using existing GPS flight data and radiosonde traces agree reasonably well and demonstrate the viability of that approach. Once the horizontal wind components are determined, the vertical wind component can be backed out from GPS data using the aircraft flight polar.

Note:
The senior authors have been requested to submit their papers to OSTIV’s quarterly, peer-reviewed, print and on-line journal Technical Soaring. The contact is Chief Editor Dr. Judah Milgram. Thus, soon you will be able to study the complete papers.