Identification of roll damping coefficient using the free rotation method

Abstract

The free rotation method represents the simplest method for roll damping coefficient identification in experimental aerodynamics. To apply this method, it is necessary to spin the model to a desired angular velocity and then release the model to spin freely under flow conditions, recording the variation in time of the model’s rolling rate. Thus, applying the logarithmic decrement formula at any roll rate between near zero and the desired angular velocity, the roll damping moment will be calculated. This paper presents the application of the free rotation method on raw data obtained for different Mach numbers and incidences, considering different regression functions, time windows and their implications. Last but not least, the necessary correction methods and their impact on the results are presented.

Keywords

• roll damping coefficient
• experimental aerodynamics
• free rotation method
• regression methods
• wind tunnel