Summary: Characterization of the effect of Froude number on
surface waves and heat transfer in inclined turbulent
open channel water flows
B. Freeze, S. Smolentsev *, N. Morley, M. Abdou
UCLA, Department of Mechanical and Aerospace Engineering, Fusion Science and Technology Center, 44-114 Engineering IV,
P.O. Box 951597, Los Angeles, CA 90095-1597, USA
Received 30 December 2002; received in revised form 4 April 2003
Interfacial heat transport in open channel turbulent flows is strongly dependent on surface waves that can appear as
a result of the interaction of bulk turbulence with the free surface. The paper describes wave/heat transfer phenomena in
inclined turbulent open surface water flows. The experiments were conducted in a regime of transition from ``weak'' to
``strong'' turbulence, in which the stabilizing influences of gravity and surface tension are relatively small against the
disturbing effects of turbulence. A key role of the Froude number, Fr?, built through the surface-normal component of
g has been revealed. As Fr? grows, the wave amplitude grows, and the frequency spectrum shifts towards shorter waves.
These changes lead to a heat transfer improvement, enough to double the heat transfer coefficient. The experimental
data have been compared with calculations based on a ``Ke'' model. As a result, the range of applicability of the
standard model has been established as Fr? < 2000. The turbulent Prandtl number has been evaluated for Fr? < 700.
Ó 2003 Elsevier Ltd. All rights reserved.
Keywords: Turbulence; Free surface; Heat transfer; Waves; Turbulent Prandtl number