A model of non-stationary aerodynamic longitudinal characteristics

Аuthors

Trifonova T. I.^*, Shelyukhin Y. F.^*, Shukhovtsov D. V.^*

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

*e-mail: flight15@tsagi.ru

Abstract

Aircraft dynamics modeling at high angles of attack requires adequate reproduction of all forces and moments acting on the aircraft under these conditions. Until recently, accounting for the ambiguity (non — stationarity) of lifting force and pitch moment coefficients c_y and m_z dependencies causes difficulties due to the lack of simple enough mathematical models of this phenomenon. The problem is aggravated by the need to calculate the aircraft dynamics in real time, which is mandatory for the bench research and crew training simulators.

The paper considers the problem of developing mathematical model of such kind based on the data obtained by the results of the tests of the of twin-engine passenger plane of the traditional scheme model with the of OVP-102B installation, which reproduces the aircraft model angle of attack harmonic oscillations at different setting angles and frequencies.

Based on the analysis of dynamic dependencies c_y(α,ά) and m_z(α,ά) obtained as test results we proposed a rather simple model for the coefficients c_y and m_z calculation as a function of the current angle of attack α(t).

The model is based on the static dependencies of lifting force and pitch moment coefficients c_y and m_z conversion by the first order differential equation (aperiodic link) with time constant T depending on the angle of attack and its rate of change.

The paper presents the technique of the input parameters and time constant forming based on known c_y(α) , m_z(α) and α(t) dependencies.

The comparison of non-stationary characteristics computed by the model with the results of wind tunnel and flight tests confirmed the suitability of the developed model for computation and experimental research of aircraft dynamics at high angles of attack.

Keywords:

non-stationary characteristics, lift coefficient, pitching-moment coefficient, angle of attack

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