Abstract
Spur dikes are well-known structures that are widely used in rivers and coastal regions. Depending on their types, sizes, and orientation angles, spur dikes can substantially change flow characteristics. Results of previous studies indicate that the presence of an ice cover in rivers can cause complicated flow structures. The present experimental study investigates velocity fields and turbulence structures in the vicinity of spur dikes under ice cover with different roughness coefficients. The spur dikes were set up at the following three angles of orientation, 90°, 60°, and 45°. Our results show that the strongest velocity fluctuation occurs immediately above the scour hole surface and very close to the dike tip. The increase in the dike angle toward upstream, the velocity component values increase, leads to a larger scour hole. Results show that an increase in dike angle of each 10° (from 45° to 90°) increases the scour depth between 5% and 10%, depending on flow conditions. Furthermore, the increase in the cover roughness coefficient and the blockage ratio of a spur dike leads to a further increase in turbulence kinetic energy and 3D velocity components values. The findings of this study imply that the appearance of an ice cover can increase turbulence intensities up to nearly 30%.
Highlights
Spur dikes are extended structures where one end is at the riverbank, and the other one is projected toward the river flow [1]
It can be concluded that under an ice-covice-covered flow condition, the vertical velocity component (Uz ) is the most important ered flow condition, the vertical velocity component (Uz) is the most important velocity velocity component for developing scour holes comparing to other velocity components component for developing scour holes comparing to other velocity components (Ux and (Ux and Uy )
To have a comprehensive study on flow characteristics in the vicinity of a dike, experiments have been conducted under conditions of open channel, smooth covered, and rough covered flow condition
Summary
Spur dikes are extended structures where one end is at the riverbank, and the other one is projected toward the river flow [1]. These constructions have been widely used for many purposes, such as river bank protection, flood control, improvement of a navigational course, control of scour process, landscape improvement, and ecosystem restoration [2]. Regardless of the different types of spur dikes, they redirect flow from the river bank and affect the flow regime, flow velocity, sediment transportation, and scour process [3]. The scour process will be affected by the shape and size of the spur dike, features of bed material, and flow conditions [4]. Zhang et al [5] investigated bed morphology, sediment distribution, and flow field in a channel with a series of impermeable spur dikes on both sides of the channel
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