The work presented in this paper represents an experimental investigat
ion into secondary flows, turbulent boundary layers and the interactio
n of the two as they develop in a zero-pressure-gradient rotating flow
field. A duct of intermediate aspect ratio was used to examine second
ary flows and determine when they begin to govern the boundary layer d
evelopment. The aspect ratio (A) was defined as duct height/width at t
he upstream end of the working section. Measurements were taken at thr
ee aspect ratios: A = 1, 2 and 4. A qualitative indication of secondar
y flow strength was established with mean-cross-stream-plane velocity
measurements. A first-order analysis of the secondary flow is presente
d which provides a reasonable estimation of their strength. Mid-span m
ean-flow, turbulence and spectra profiles were measured on the duct wa
lls parallel to the axis of rotation. Results are generally presented
for A = 2 and 1. For A = 4 and 2 there were minor effects of secondary
flows observed on the mid-span mean flow parameters. The turbulent sh
ear measurements showed some secondary flow effect for A = 2. All turb
ulence and mean-flow quantities were strongly affected by secondary fl
ows for A = 1. Spectra results presented for A = 2 showed most variati
on at the low-to-mid wavenumber end. Spectra results for A = 1 showed
a bodily shift of the whole spectrum towards low wavenumber on the pre
ssure side and high wavenumber on the suction side.