Shallow Turbulent Flows
Shallow Flows in our environment
flows exist where the horizontal length scales of the flow domain are
much larger than the depth. Such shallow flows are ubiquitous
in nature, ranging from river, estuarine, and oceanic flows to
stratified flows in the atmosphere. Although turbulent eddy
size is typically limited by the shortest dimension, large-scale
coherent turbulent structures are observed in shallow flows with
length-scales orders of magnitude greater than the depth.
Shallow flows is also the subject of an IAHR conference series: the
Flows conference was held in Delft, The Netherlands in 2003
and the second one will be held in 2008 in Hong Kong, China. As an
example see to the right a picture of Argo Merchant, an oil tanker (200
m long) that run aground in December 1976 in 3m shallow waters near
Natucket Island generating a vortex street of the order of hundreds of
Vortex street behind Argo Merchant in 3m shallow waters (visualised by crude oil).
Satellite pictures of atmospheric and ocean wakes, plumes and vortices [NASA].
visualization of cylinder wakes in the shallow water basin (IfH).
Laboratory Experiments and Numerical Studies
Our research at IfH includes experimental,
analytical and numerical work. The laboratory experiments
include Laser Doppler Velocimetry (LDV) measures of the turbulent flow
characteristics coupled with Laser Induced Fluorescence (LIF) to
understand the short time- and space-scale turbulent transport
characteristics of the flow. Laboratory experiments also
include Particle Image Velocimetry (PIV) coupled with Planar
Concentration Measurements (PCA) to study the basin-scale transport
characteristics of the large coherent structures. These
laboratory data are then used to interpret numerical stability
analysis focused on the stability of these shallow wakes. The
different stability regimes determine the fashion in which these
large-scale structures detach from the obstacle; thus, they determine
the nature of the turbulent transport.
techniques were adapted and developed for appropriate use in the
IfH - Shallow Water Basin. Among them are Particle Image Velocimetry -
PIV, Particle Tracking Velocimetry - PTV, Laser Doppler Velocimetry -
LDV-LIF, Planar Concentration Analysis - PCA.
Mass concentration in LCS in shallow cylinder wake flow [v.Carmer 2005].
Enhanced turbulent mixing in shallow flows by LCS [Rummel et al 2005].
rummel (at) ifh uka de