| Περίληψη: | In this student research project, the methods of aerodynamic improvement of a wide variety of aircrafts, with the main objective of reducing drag force, are examined. Different ways of drag reduction are analyzed but an in-depth and further study is made on the methodology of riblet films.
Firstly, we find the literature and references from experts in the subject, as to the positive impact of riblet films in terms of drag reduction. As we firstly do our research of the riblet films, then the different geometries of riblets are studied, experimental and theoretical results under specific conditions are reported. Also, their installation in the aviation industry and various problems faced by scientists who are called upon to carry out the proper use of riblets are mentioned.
Then the results of the ONERA M6 wing are validated so that we have a first attempt with the computational fluid dynamics programs. Three different meshes were created in terms of their density, but of the same type, in order to compare the numerical results with the experimental ones. From the validation of the wing results we have drawn some useful conclusions for the correct creation of the meshes, which will then be used for the study of riblets.
Subsequently, five different models of riblets on a flat plate are examined, which are placed inside a rectangular duct of fixed dimensions and located on its lower surface. The rectangular duct was chosen because the top surface is a flat surface parallel to the flow as is the bottom surface of the duct, which is the riblets, so a simultaneous comparison of the two surfaces can be made without the need for additional grids.
The models were tested under the same conditions and for the dimensioning of the riblets some parameters were taken from the flight conditions of the Greek Civil Unmanned Aircraft RX-1, HCUAV. In addition, four different speeds were used for each model. From the results we can have a general view of the ideal non-dimensional distance of the riblets s+, as well as the variation of the vortices, created due to the flow, due to the riblets. We also notice a change in the flow velocity along the riblets.
|
|---|
