Mathematical model of an airflow mass velocity module in the unpressurized aircraft compartment

Ensuring reliability of the onboard equipment is one of the challenges in designing the unpressurized aircraft instrument compartments. To address this challenge, thermal state of the aircraft compartments is studied using mathematical models of their thermal state. Mathematical models of the compartment thermal state incorporate their elements thermophysical characteristics and include the air mass velocity (product of the air density and velocity). The paper presents results of studying the air mass velocity modulus in the unpressurized compartments of two maneuverable aircraft based on the flight test results. To construct a mathematical model of the air mass velocity modulus, phenomena causing air motion in the instrument compartments are analyzed. The paper shows that the air mass velocity modulus depends on both the flight mode parameters and the air thermophysical parameters outboard. Mathematical model parametric identification uses the Broyden-Fletcher-Goldfarb-Shanno method for the aircraft acceleration mode. An original transducer is developed for measuring the air mass velocity modulus. Optimal ratio of the hot-wire anemometer geometric parameters is analytically determined and experimentally proven. The paper assesses dynamic and static errors in the modulus measurement using mathematical models of the transient convective-radiative heat transfer within the aircraft transducer compartment.
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