Local heat/mass transfer distributions on the bottom surface of a cavity exposed to an approaching turbulent boundary layer: Aspect ratio effects

•Mass transfer on the bottom surface of rectangular cavities is measured with a naphthalene sublimation technique. The effects of cavity length to depth (0.75 to 10) and width-to-depth (0.54-10) are examined.•Depending on the aspect ratio, the flow structures can be substantially different, yielding significantly different mass transfer distributions on the cavity floor.•The presence of sidewalls establishes a system of vortices which cause strong local variations in transport.•Insight into the high-resolution mass transfer distributions is gained by examining flow streamlines calculated using RANS computations.