Introduction

The aim of this study is to find out if the addition of different shaped indented vortex generators to aerofoils can replace a conventional vortex generator and therefore increase the lift and stability of the aircraft without increasing drag. The study will discuss the change in lift and drag characteristics and discover the best placement and distribution of divots across the aerofoil. It will also test the change of pressure, lift and drag within a wind tunnel and CFD simulation. It will also cover delaying the separation of flow over an aerofoil to improve the manoeuvrability of an aircraft. Any improvements found will apply to a multitude of applications such as in military aircraft, helicopter rotor blades and wind turbine blades. Theoretical Data collected in this study can be backed up by practical data gathered in a wind tunnel.

Past Literature

Past studies have proven that inward shaped dimples are more effective than outward dimples and the best positioning for the divots are between 10%-20% of the Chord length. The vortex generators work by creating rotating flow over the top surface of the aerofoil, moving the separation of flow further aft, therefore, creating a difference in pressure across more of the surface of the aerofoil. This in turn creates more lift and reduces the drag on the aerofoil.

3D Printing Aerofoils

In this case, a Creality Ender 3 V2 with various upgrades was used to 3D print the aerofoil sections in PLA+, made by eSUN, which provided excellent results after much trialling. The issues that arose during printing were mainly that of change in temperature of the environment. Due to long print times of over 3 days, the change in temperature would affect the prints through thermal expansion and quicker part cooling causing them to fail. A 1/15^th scale model of the aerofoil was printed to ensure the fit was correct and there were no issues with the shape. The image below shows the test print. It shows both the plain teardrop-shaped dimple side and a plain side. A line can be seen up the side and this is called the Z-axis seam caused by the change in printing layers. It can be removed using tools in Ultimaker Cura such as smart hiding to give a smooth surface finish.

Results

The practical results of the aerofoils have yet to be analysed however, the results from the computational analysis show that the aerofoils with the addition of vortex generators have an increased coefficient of lift of up to 5%. The predicted increase from the practical data is around 10% for the lift of the aerofoil and a slight reduction in drag. This proves the value of adding vortex generators to aerofoils and will be backed up by practical data taken from inside an AF-1300 subsonic wind tunnel.