Changes In Boundary Layer Structure Research Articles

Observations of atmospheric boundary layer temperature profiles with a small unmanned aerial vehicle

AbstractSmall Unmanned Meteorological Observer (SUMO) unmanned aerial vehicles (UAVs) were used to observe atmospheric boundary layer temperature profiles in the vicinity of McMurdo Station, Antarctica during January and September 2012. The observations from four flight days are shown and exhibit a variety of boundary layer temperature profiles ranging from deep, well-mixed conditions to strong, shallow inversions. Repeat UAV profiles over short periods of time (tens of minutes to several hours) revealed rapid changes in boundary layer structure. The success of the SUMO flights described here demonstrates the potential for using small UAVs for Antarctic research.

Turbulent boundary layers on axially-inclined cylinders. II. Circumferentially averaged wall-pressure wavenumber–frequency spectra

The boundary layer on a long cylinder with its axis at small inclinations to the freestream (an idealisation of “streamers” used in underwater seismic surveys) has been studied experimentally. For the range of incidence 0–6°, there is no evidence of vortex shedding at typical Reynolds numbers. The circumferentially averaged fluctuating wall pressure decreases with increasing incidence, showing that increases in extraneous noise in seismic measurements when the streamer is at incidence are not caused by the changes in boundary layer structure. Wavenumber–frequency spectra of the circumferentially averaged wall pressure show a convective ridge that persists for the range of incidences studied.