Water tunnel validation and experiments at high angles of attack for aircraft conceptual design

Sammanfattning: The identification of aerodynamic characteristics at high angles of attack for combat aircraft during conceptual design are addressed in this work. The requirements during conceptual design to predict such characteristics rapidly and cost effectively mean that accuracy must often be compromised. In order to allow configuration selection to be undertaken and so proceed to preliminary design the design team seeks not only quantitative information but also useful qualitative information that guides towards possible problem areas and potential for improvement. In the present work the water tunnel is proposed to offer potential as such a tool.While such a proposition for the use of the water tunnel is not new, a comprehensive study of the scaling issues (most particularly with regard to Reynolds number) has not been undertaken. The present work seeks to address this issue by undertaking qualitative and quantitative flow visualisation and force and moment comparisons with the published literature for standard test cases such as delta wings. These comparisons show that the effect of Reynolds number is minor, and that it is masked by more significant issues related to experimental setup and data acquisition. As a note of warning, it is demonstrated that where Reynolds number is important then water tunnel data must be treated with caution.Both static and dynamic tests on a wide range of planforms ranging from simpledelta wings, double delta wings, forebodies and complete configurations were performed to demonstrate the above issues. As such, this work provides a database for further development and investigation of the key issues raised, as well as a pointer towards areas worthy of further investigation.For conceptual design of configurations which are insensitive to Reynolds number it is shown that the water tunnel is of benefit as a diagnostic tool from which prudent configuration selections can be made, or at least that it acts as a means of guiding the design team towards the optimum design.