**The flows over and within
cavities or surface cut-outs is of relevance to many branches of engineering,
ranging from the small cavities due to gaps in the body work of vehicles and the
variable roughness of river channel beds, through open weapons and cargo bays on
aircraft, to the larger scale flows in urban street
canyons.**

**This page shows some results from studies of the flows in
rectangular planform cavities where the flow is yawed to the cavity principal
axis. The measurements carried out have included mean and unsteady pressures,
together with flow visualisation. Comparisons have
also been made with CFD predictions.**

**For
nominally 2-D rectangular cavities, the flow may be classified as
"open", closed or transitional, depending on the cavity streamwise
length to depth ratio (L / D). Open flow regimes exhibit distinct peaks in
measured sound pressure spectra, whilst the closed cavity signals are more
broadband.**

**As
a cavity is yawed there are distinct changes in the flow pattern, the wall and
base pressure distributions and overall drag (a typical example of the mean
pressure coefficient, Cp, distributions is shown below, where red are the
highest positive pressures and blue represents negative, or suction, pressures).**

**Detailed
studies for a range of cavity geometies, of different Length, Width (W) and
Depth has allowed an extension of the categorisation of 2-D cavity flows to 3-D
planforms.**

**Some comparisons
between the mean flow pressure coefficients and overall cavity drag have been
made with CFD predictions using the FLUENT code. The results show generally good
agreement.**

**The
measurements, CFD predictions and flow visualisation studies have allowed an
interpretation of the basic flow field and how it changes with yaw angle.**