Wind tunnel description

The research was carried out in wind tunnel placed at Aerodynamic Department Faculty of Power and Aeronautical Engineering Warsaw University of Technology. The test focused only on longitudinal cases. The wind tunnel facilities is equipped with devices which is able to measurement the drag force, the lift force and force cause the pitching moment. The campaign was carried out for free stream speed equal V=40m/s, Re=705 000 and for range of angles of attack from 0^o to 45^o.

5.2 Model

The model was built in 1:15 scale. The baseline configuration consist of the axis symmetrical fuselage, the sweep wing, all moving tail placed on the wing tips and the triangular strake.

Two group of strake were tested. The first group consists of SFF attach to the leading edge of triangular strake. The flap was rotated around the same hinge line. Fig. 26 and Fig. 27 presented two shapes of flaps which were tested.

Second type was the strake retractable flap.

Fig. 28 to Fig. 31 presents wind tunnel model of this kind of flap.

Fig. 26 Trapeze flap attach to the triangular strake.

Fig. 27 Ogee flaps attach to the triangular strake.

Fig. 28 The strake retractable flap for full leading edge rotation.

Fig. 29 The strake retractable flap for full leading edge rotation.

Fig. 30 The strake retractable flap for half leading edge rotation.

Fig. 31 The strake retractable flap for half leading edge rotation.

Study on the influence of deflected strake on the rocket plane aerodynamic characteristics.

CEAS 2013 The International Conference of the European Aerospace Societies 5.3 Results

Results of wind tunnel test include chart of lift force versus angle of attack and chart of pitching moment coefficient versus angle of attack for some of investigated configuration.

Fig. 32 Retractable semi-span flap - Lift coefficient vs.

AoA.

Fig. 33 Retractable semi-span flap – Pitching moment coefficient vs. AoA.

Fig. 34 Retractable full-span flap - Lift coefficient vs.

AoA.

Fig. 35 Retractable full-span flap – Pitching moment coefficient vs. AoA.

Fig. 36 Ogee flap – Pitching movement coefficient vs.

AoA.

Fig. 37 Trapeze SFF – Pitching moment coefficient vs.

AoA.

5.4 Conclusions

According to experimental results all presented type of flaps a little improves the pitching moment coefficient. However the most

effective solution is full span retractable flaps (see Fig. 35) but this configuration has the lowest value of lift coefficient (see Fig. 34).

Additionally, the result of computation for SFF 7 was validated by wind tunnel test (see Fig. 37). The difference between numerical and experimental data is connected with method of numerical calculation (inviscid flow), different configuration of all moving tail in wind tunnel model compare to numerical model and precision of define reference point during experiment.

6 Summary and Conclusions

The main goal of this paper was to research the influence of movable strake on the aerodynamic characteristics of aircraft in tailless configuration. Two concepts of movable strake were considered: hinged strake and Stake Forward Flap. .

Results of computation reveal that the concept of hinged strake is promising, but the some problems with implementation may occur.

It is connected with quite large area of strake which will be deflected.

Conception of SFF reveals that it will be very useful but only to control the pitching moment.

The increase of lift coefficient caused by flap deflection is rather low.

The wind tunnel test was used to validate the numerical computation and to check other concept of flap. Results reveal small improvement of aerodynamic coefficient by presented cases.

Usually tailless configuration of aircraft designed with a strake has a big problem with pitching moment. Results of presented investigation show that for triangular strake with the simple straight flap deflected obtain stability for full range of angle of attack is possible. Moreover, the lost of lift coefficient caused by deflected flap is slight.

Research presented in this paper includes only preliminary analysis of the movable strake.

It is planned to continue the further research on presented problem.

Acknowledgements

Authors would like to express our thank for Aerodynamic Department for access to wind tunnel. Moreover, the baseline configuration of the wind tunnel model was built by students of two-staged spacepalne for suborbital tourism”, Transactions of the Institute of Aviation, Vol.

191 No.4/2007, pp.33-42

[3] Figat M., Gali2ski C., Kwiek A., „Modular Aeroplane System. A Concept and Initial Investigation”, Proceeding of ICAS 2012 Conference, Brisbane, paper number ICAS 2012-1.3.2

[4] Figat M., Gali2ski C., Kwiek A., „Modular Aeroplane System to space tourism”, Progress in Aeronautics Vol. 32, No. 1, 2011, pp. 24-37 [5] Lamar J.E., Frink N.T., “Aerodynamic Features

of Designed Strake-Wing Configurations”, Journal of Aircraft, Vol. 19, No. 8, 1982 pp.

639-646

[6] Polhamus E.C., „A Concept of the vortex lift of sharp-edge delta wing based on a

leading-edge-suction analogy”, NASA technical note, Washington D.C. 1966

[7] Mitchell A. M, Delery J., „Research into vortex breakdown control”, Progress in Aerospace Sciences, Vol. 37, pp. 385-418, 2001

[8] Rao D. M., “Vortical Flow Management for improved configuration aerodynamic- recent experiences” Vigyan Research Associates. Inc.

[9] Zahao W., Kwak D., Rinoie K., „Studies on Improvment of Nonlinear Pitching Moment Charactersitics of Cranked-Arrow Wing”

Proceeding of ICAS 2012 Conference, Brisbane, paper number ICAS 2012-3.2.1

[10]MGAERO A Cartesian Multigird Euler Code for Flow Around Arbitrary Configuration User’s Manual Version 3.1.4

[11] Mavriplis D.J., “Three-Dimensional Unstructured Multigrid for the Euler Equations”, Journal of Aircraft, Vol. 30, No 7, July 1992

CEAS 2013 The International Conference of the European Aerospace Societies Abstract

The paper shows preliminary results of aeroelastic analyses of two half-wing models, having curved and swept planform, carried out at the Aerospace Unit of the Department of Civil and Industrial Engineering of Pisa University. For a wing with a curved planform, as demonstrated in previous papers regarding rigid models of wings, the wave drag effects are strongly reduced in the transonic flight conditions.

In the paper some results obtained by using Star-CCM+^® 6.04.14 and Abaqus^® 6.11 in “co-simulation” are summarized: for this reason the present numerical comparison, between a curved wing and a swept wing, includes the effects of structure’s deformability (the wings have the same aspect ratio). The beneficial effects of the planform shape on drag polar curves are confirmed.

Moreover the curved planform configuration improves the wing’s aeroelastic behavior: for a fixed value of CL the reaction moments and stress values at the root of the curved wing are reduced by about 5%÷8% with respect the data obtained for the swept wing at the same flight conditions.

Finally, preliminary numerical analyses carried out at high angles of attack show that, as expected, the centers of pressure of the wings

move forward with percentage variation of their longitudinal positions that are quite similar.

These results indicate that the curved planform shape does not change in a drastic fashion the performances of a wing when the stall condition are reached.

1 Introduction

It is well known that a method to reduce the effect of a shock wave over wings, flying at high subsonic conditions, concerns the increase of the sweep angle of the leading edge. Modern aircrafts have high value of this angle and also high levels of tapering. To obtain the same effects, that is a reduction of both shock wave effects and drag for the aircraft, the curved wing concept has been introduced and discussed by the authors in some previous papers ([1], [2], [3]). To get a confirmation of the good aerodynamic behaviour of such a wing configuration, a new comparative analysis has been executed, at the Aerospace Unit of the University of Pisa, adopting a fluid-structure interaction technique: this analysis provides obviously the effects of the elastic deformation of the wings’ structure, representing in a more realistic fashion the loading condition of a flying wing.

In the research development the two wings shown in Figure 1 have been considered [4], [5].

The two wings have the same aspect ratio (half span and chords’ distribution are similar:

Fluid-Structure Interaction Analyses of Wings with Curved