Reduced dynamical models are derived for transitional flow and heat tr
ansfer in a periodically grooved channel. The full governing partial d
ifferential equations are solved by a spectral element method. Spontan
eously oscillatory solutions are computed for Reynolds number Re great
er than or equal to 300 and proper orthogonal decomposition is used to
extract the empirical eigenfunctions at Re=430, 750, 1050, and Pr=0.7
1. In each case, the organized spatio-temporal structures of the therm
ofluid system are identified, and their dependence on Reynolds number
is discussed. Low-dimensional models are obtained for Re=430, 750, and
1050 using the computed empirical eigenfunctions as basis functions a
nd applying Galerkin's method. At least four eigenmodes for each field
variable are required to predict stable, self-sustained oscillations
of correct amplitude at ''design'' conditions. Retaining more than six
eigenmodes may reduce the accuracy of the low-order models due to noi
se introduced by the low-energy high order eigenmodes. The low-order m
odels successfully describe the dynamical characteristics of the flow
for Re close to the design conditions. Far from the design conditions,
the reduced models predict quasi-periodic or period-doubling routes t
o chaos as Re is increased. The case Pr=7.1 is briefly discussed. (C)
1997 American Institute of Physics.