Observations on High Reynolds Number Turbulent Boundary Layer Measurements

An experimental study that examines spatial resolution effects on the measured streamwise velocity component is presented. Normal hot-wire measurements for mean flow velocity profiles, streamwise turbulence intensity profiles in addition to their respective spectra at different levels within the turbulent boundary layers will be presented. Measurements were carried out at Reynolds number based on momentum thickness, Rθ= 20,000. Matching the same Reynolds number of the flows is achieved by varying the measuring station and consequently the reference freestream velocity. Wires of non-dimensional lengths l, ranging from 11−54, were used. These measurements show that attenuation in hot-wire signals for long wires extend not only deep within the boundary layer, but also to the low wavenumber part of the spectra. It is conjectured that wires with the same l, will be prone to further attenuation due to the increase of end conduction loss with increasing freestream velocity.