Bayraktar UAV Dynamic Stability Derivatives: CFD Simulation by Ansys Fluent

Description

Dynamic Stability Derivatives: Bayraktar UAV CFD Simulation Training

Introduction

The determination of an UAV’s dynamic stability and control derivatives is vital for the development of accurate flight models and control system design. These coefficients, which relate aerodynamic moments to angular motion, are traditionally obtained through costly and time-consuming wind tunnel tests.

In Bayraktar UAV dynamic stability derivatives project, a numerical approach based on computational fluid dynamics (CFD) combined with the forced oscillation technique is proposed to efficiently extract the derivatives of the dynamic stability of an UAV in the subsonic flight regime.

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Bayraktar is an unmanned aerial vehicle from Turkey. It is a long-lasting, medium-altitude drone. It can be used for surveillance and reconnaissance.

It has a top speed of more than 220 kilometers per hour. The UAV has a fuel capacity of 300 liters. The range can go up to 300 km. 5.48 kilometers is the operational altitude. The greatest height is 7.62 kilometers Maximum loitering time for this drone is 27 hours.

In this simulation, a Bayraktar UAV with one propeller rotating around the horizontal axis is modeled using ANSYS Fluent software. The device is moving at a speed of 140 km/h.

The geometry of the present model is three-dimensional and has been designed using Design Modeler software. We do the meshing of the present model with Fluent Meshing software. The mesh type is Tetrahedral, and the element number is 5,932,646.

The computational domain is specifically structured with three fluid regions to facilitate the motion: a rotating internal fluid region for the blade, an oscillating internal fluid region that completely encloses the drone, and an external fluid region that does not oscillate. This research focuses on applying a specific cosine oscillation to the drone and analyzing the resulting aerodynamic moments to quantify the dynamic stability derivatives.

Methodology

In Bayraktar study used a transient, pressure-based CFD simulation in ANSYS Fluent to analyze the incompressible flow around a UAV to derive dynamic derivatives. The flow physics was modeled using the k-ω SST turbulence model. The key method involved the oscillatory region technique, in which an inner fluid region, containing the UAV, was forced into a simple harmonic oscillation via a UDF, while the outer domain was set with inlet and outlet boundary conditions. This setup, with good time resolution, was designed to capture the aerodynamic response necessary to calculate dynamic stability derivatives.

Results and Conclusion

The most commonly used and important coefficients in the discussion of stability have been extracted after simulation and are given in the table below. Using these coefficients, it is possible to comment on whether a drone is stable or not in terms of static and dynamic. Also, using the extracted data, hysteresis diagrams have been drawn, which can be understood by considering the shape and direction of rotation of these rings, whether the drone is stable or not.