10.20381/ruor-18974
Post, Gavin Charles
The measurement of Reynolds stresses in a model river bend using acoustic doppler velocimeters
Université d'Ottawa / University of Ottawa
2007
Engineering, Civil.
Université d'Ottawa / University of Ottawa
Université d'Ottawa / University of Ottawa
2013-11-07
2013-11-07
2007
2007
en
Thesis
Source: Masters Abstracts International, Volume: 47-06, page: 3687.
http://hdl.handle.net/10393/27906
This thesis reports the first two experiments in long term study of the distribution of Reynolds stresses in a model river bend, as well as the development and procedural details of the model river bend itself. The open channel flume measures 18.2 m along the centerline, and is 1 m wide with a uniform 0.3 m deep mobile sand bed. With a 12.2 m straight approach, a 135 bend with 1.5 m constant radius, followed by a straight exit section, this bend is considered to be sharply curved. The first experiment was conducted with a channel slope of 0.044% which, for the 0.2 m flow depth resulted in clear water scour conditions in the bend with a planned dimensionless boundary shear stress, tau*, of 0.035. For the second experiment, the slope was increased to 0.064% to ensure movement in the straight approach section which required sediment circulation. Dimensionless boundary shear stress for the second test was selected to be 0.05. Following development of equilibrium bed topography in the first test, a total of 609 time-series measurements lasting 2 minutes each were taken at a wide distribution throughout the entire bend. Two Vectrino ADVs were used for velocity measurements operating at a sampling frequency of 200Hz and the ability of these sensors to directly measure 3D Reynolds stress is a key aspect of this study. With a noted lack of data on Reynolds stresses for which to calibrate turbulent flow models, this thesis is designed to identify these stresses. Through the examination of the mean flow properties and verifying that the measurements are correct, the discovery of two zones of high streamwise-vertical Reynolds stress are reported, one at the beginning of the scour hole formation, and the other at the tip of the downstream point bar. For this thesis the results from the first experiment will be examined in detail, and the second will be discussed only from a qualitative point of view since all measurements could not be completed.