Abstract
The article describes the concept of scaled model and its application in the process of real aircraft prototyping. Computer simulations of aerodynamic flows are commonly used in the design of aircraft. Numerous data on the characteristics of an airplane can be obtained using tunnel tests of geometry scaled models. To get complete information in extreme or unstable conditions, dynamically scaled models are tested. The scaled model is reduced model of the real airplane which has specific qualities similar to real aircraft qualities and these relations are strictly defined with characteristic similarity numbers (factors). The paper presents methodology for determining scale factors in relation to geometric, aerodynamic and structural properties (mass, stiffness) of the aircraft. The methodology was presented on the example of passenger aircraft (Tu-154M) model developed in Faculty of Mechatronics and Aerospace of the Military University of Technology (FMA MUT Warsaw, PL).
Highlights
YY ZZ LLUnknown speed vectors: linear V (U, V, W);; angular Ώ (P, Q, R)
To be dynamically similar, model has to have the solution of motion equations in dimensionless form the same as real airplane
The factors were determined taking into account the following assumptions: - model and real plane are at the same flight altitude;; - the effect of compressibility was omitted;; - moments of inertia determined for the aircraft mass of 78000 kg
Summary
Unknown speed vectors: linear V (U, V, W);; angular Ώ (P, Q, R). Mass terms: total mass(m);; moments of inertia – axial /deviational (Jx, Jy, Jz /Jxy, Jxz, Jyz), static moments (Sx, Sy, Sz). Vector of external loads: forces F (X, Y, Z) and moments M (L, M, N). Dynamic motion equation for any force vector X is the following: m(UU + QW RV) – Sx(Q2 + R2) – Sy (RṘ – PQ) + Sz(QQ – PR) = X (2). Dimensionless form X, after dividing equation (2) by the dynamic term (ρSv02):. The components of dimensionless equation (3) of the model and the real plane must be equal. The same transformations for 5 equations can be done. The dynamic similarity scale coefficients are determined. Basic similarity coefficients are shown in table 1
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