Manchester University - Reynolds Number
One of the most important characteristics in aircraft wing design is the Reynolds Number which describes the behaviour of airflow around awing section. This was important in the early years of aviation but is critical today as air vehicles achieve great heights and speeds.
The Reynolds Number is dimensionless, so it doesn't have any units. This makes it useful for comparing aircraft of all sizes. It's simply how easily liquids (including air) flow versus how much they resist flowthrough shear stress. It gives aircraft designers an idea of the amount of turbulence that will manifest in a fluid under different conditions.
The lower the number the smoother the airflow, and higher the number the more turbulence.
The science underpinning this discovery was undertaken at Manchester University (then known as Owens College) by Osborne Reynolds, one of the forefathers of fluid dynamics research.
Born in Belfast in 1842, he had by 1868 become one of the first professors in UK university history to hold the title of 'Professor of Engineering'.
(Monochrome Photograph) - Osborne Reynolds
His early work was on magnetism and electricity, but after 1873 he concentrated on fluid dynamics. It was in this area that his contributions were of world leading importance especially to the aviation industry.
Using his dye apparatus he studied the conditions of transition from smooth to turbulent flow at different speeds indicated by patterns of dye injected into water in a long tube.
At low speed, the dye showed regular straight lines. When the flow velocity increased, the dye became turbulent. He also noticed that the of turbulent flow was also dependant on viscosity.
From this he developed the parameter now known as the Reynolds
Number. The lower the number the smoother the airflow, and higher the number the more turbulence.
The original dye test apparatus that Osborne Reynolds used to develop his theories remains on display at Manchester University in the Department of Mechanical and Aeronautical Engineering.
Scan the QR code to see Andrew Kennaugh of Manchester University demonstrate the original Reynolds apparatus.
For its aircraft designs, Woodford had its own high speed wind tunnel that was used to help the design teams understand the Reynolds Number applicable to the wings relative to different height and speed conditions, and several of the original wind tunnel models and aerofoil sections are on display within the Avro Heritage Museum.