Coherent structures around isolated spur dikes at various approach flow angles

The turbulent flow structures around an isolated spur dike located at three different approach flow angles are investigated. Detached eddy simulation is used at a channel Reynolds number of 45,000. Experimental velocity measurements were also conducted using acoustic Doppler velocimetry for validating the simulations. It is found that the size and orientation of the horseshoe vortex system change considerably with the approach flow angle. The main necklace vortex is largest in size and most coherent for 90 degrees. Within this orientation it has larger amplitude bimodal oscillations compared to the 60 degrees and 120 degrees cases. A new scour mechanism is defined for the 60 degrees case which is expected to generate more scour upstream of the spur dike. The possible scour area around the spur dike is found to be the maximum in the 90 degrees case which is roughly by 15% larger than that of the 120 degrees case.


Coherent structures in a sharply curved bend with and without a spur dike.
Köken, Mete; Budak, Ezgi (null; 2017-08-18)
: Results of three-dimensional (3D) Detached Eddy Simulation (DES) are used to investigate the changes in flow and large-scale coherent structures within a high-curvature open channel, with and without an isolated spur dike located on the outer bank of the
Effect of spur dike length on the horseshoe vortex system and the bed shear stress distribution
Köken, Mete; Göğüş, Mustafa (2015-03-04)
Turbulent flow structures forming around isolated spur dikes in a horizontal channel are investigated in this study. In the analysis detached eddy simulation is used under fully turbulent incoming flow conditions at a channel Reynolds number of 45,000. Changes in the structure of the horseshoe vortex system, bed shear stress and pressure standard deviation on the bed are investigated for three different spur dike lengths. In all of the cases the main horseshoe vortex undergoes bimodal oscillations, which le...
Analysis and control of complex flows in U-bends using computational fluid dynamics
Güden, Yiğitcan; Yavuz, Mehmet Metin; Department of Mechanical Engineering (2014)
Analysis and control of flow structure is crucial in the sense that the increase in the ratio of inertial and centrifugal forces to viscous forces destabilizes the flow and creates a three-dimensional complex flow consisting of stream wise parallel counter-rotating vortices, so-called Dean vortices. In addition, due to the curvature in U-bends, in line with these vortices, a high level of turbulence is detected, which is quite critical in considering noise problems and structural failures. In this thesis, c...
Coherent structures at different contraction ratios caused by two spill-through abutments
Köken, Mete (Informa UK Limited, 2017-8-23)
Detached eddy simulation (DES) at a channel Reynolds number of 45,000 is used to investigate the coherent structures forming around spill-through abutments located at opposite sides of a rectangular channel which contract the flow section. Changes in the coherent structures are investigated for two contraction ratios at two different scour stages. It is observed that at the small contraction ratio the coherent structures forming around the abutments are similar to the ones observed for isolated abutments. H...
Elliptical Pin Fins as an Alternative to Circular Pin Fins for Gas Turbine Blade Cooling Applications Part 2 Wake Flow Field Measurements and Visualization Using Particle Image Velocimetry
Uzol, Oğuz (null; 2001-06-07)
Extensive wake flow field measurements and visualizations are conducted using particle image velocimetry (PIV) inside the wakes of the elliptical and circular pin fin arrays in order to better understand the flow physics and the loss mechanisms of these devices. The true-mean velocity field inside the wake two diameters downstream of the pin fin arrays is obtained by collecting and ensemble averaging a large number of PIV samples in the midplane of the test section. Additional experiments are also conducted...
Citation Formats
M. Köken, “Coherent structures around isolated spur dikes at various approach flow angles,” JOURNAL OF HYDRAULIC RESEARCH, pp. 736–743, 2011, Accessed: 00, 2020. [Online]. Available: