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Test section design for measuring the drag coefficient of a suborbital rocket model at Ma 2.45

100%

Wasilczuk F. , Kurowski M. , Flaszyński P.

tom Nr 3 (276)

86--100

This study investigates the drag coefficient of three models of suborbital rockets with different nosecones. A test section allowing for force measurement of a 1:50 scale rocket model was designed with the aid of numerical simulations. The velocity obtained in the wind tunnel corresponds with a Mach number of 2.45. RANS simulations were used in verifying operating parameters, as well as testing the support configurations for connecting the model with the bottom wall of the tunnel section. Pressure distribution measurements on the top and bottom walls of the wind tunnel matched simulation results well. The shock structure in the test section was visualized using the schlieren technique, revealing that the measured angle of the main shock generated at the tip of the rocket matched the simulation data. Finally, the measured forces were compared with simulations for one of the nosecone configurations. Despite very good agreement for pressure distribution on the wind tunnel walls and shock structure, a significant mismatch in the forces measured was nevertheless observed: the simulated CD (0.57) being four times larger than that obtained in measurements (0.138). Further analysis of the test section is required to pinpoint the source of discrepancies and redesign the force measurement system to achieve improved force results.

Measurement uncertainty contribution to the MLP neural network learning algorithm applied to an aerodynamic external balance calibration curve fitting

100%

Barbosa I. M. , del Moral Hernandez E. , Reis M. L. C. C. , Mello O. A. F.

tom Vol. 14, nr 1

101-115

The aim of this study is to fit a calibration curve to a multivariate measurement system considering uncertainty in load measurements. The experimental data are generated from the calibration of the aerodynamic external balance of the subsonic wind tunnel n.o 2, at the Brazilian Institute of Aeronautics and Space. To fit the calibration curve, Multilayer Perceptron Artificial Neural Networks are submitted to the learning process. Studies employing several different architectures were carried out in order to improve the MLP convergence. The uncertainty in measurements is taken into consideration, through the modification of the learning algorithm, which in its classical approach, considers the data points free from error sources. The results of both methodologies, learning algorithm endowed with and without uncertainties, are compared. The artificial neural network performance in predicting future calibration data is explored through the simulation process.

Wind tunnel tests of the effects of aerodynamic interference on a stadium roof

86%

Bosak G.

tom R. 111, z. 6-B

41--53

This paper summarizes results of wind tunnel tests of a non-standard stadium roof. Aerodynamic laboratory studies were accomplished in a boundary layer wind tunnel. The main objective of the research was to determine the distribution of the mean wind net pressure coefficient over the stadium roof surfaces as affected by the aerodynamic interference between the stadium structure and a large oval sports event hall, located nearby. Interference coefficients of wind pressure and global wind forces acting upon the surfaces of the stadium roof were calculated. The aerodynamic studies showed a significant influence of the oval Atlas Arena sports-event hall on the wind load subjected to the stadium structure.

W artykule przedstawiono rezultaty badań modelowych w tunelu aerodynamicznym niestandardowego zadaszenia stadionu. Badania zostały wykonane w tunelu aerodynamicznym z warstwą przyścienną. Podstawowym celem analiz było określenie rozkładu wartości współczynnika średniego ciśnienia wiatru na powierzchniach zadaszenia w warunkach występowania interferencji aerodynamicznej pomiędzy konstrukcją stadionu a rozległą owalną halą widowiskowo-sportową położoną w bliskim sąsiedztwie. Wyznaczono współczynniki interferencji odnoszące się do ciśnienia wiatru na powierzchni zadaszenia oraz do sumarycznych sił działania wiatru na konstrukcję dachu stadionu. Badania wykazały znaczący wpływ hali widowiskowo-sportowej Atlas Areny na działanie wiatru na konstrukcję stadionu.

Assessment of the concept of a propeller working in a slot in the middle of wing of a micro air vehicle

58%

Mieloszyk J. , Galiński C.

tom Vol. LX, nr 2

269--282

Two configurations of micro-airplanes are compared in this paper. The first, very innovative one, has a propeller working in a slot in the middle of the wing. The second airplane has more classical configuration with a pusher propeller. Advantages and disadvantages of both configurations are evaluated, which makes it possible to assess what are the best possible mission types for each micro-airplane.

W artykule porównano dwie konfiguracje mikrosamolotów. Pierwsza z nich, innowacyjna, ma śmigło w szczelinie płata. Druga, bardziej konwencjonalna zakłada wykorzystanie śmigła pchającego. Oceniono wady i zalety obydwu konfiguracji, dzięki czemu można wskazać najbardziej odpowiednie rodzaje misji dla każdego z mikrosamolotów.