Flow and sediment transport around the patch of vegetation are closely linked to landform evolution, and the understanding of such processes allows effective river restoration and management. Numerical investigation of flow and suspended sediment (with size, ds, ranging between 10 and 40 μm) deposition within and around a circular patch of emergent vegetation was conducted using a two‐dimensional model, in which the vegetation was assumed as a porous zone. A von Kármán vortex street formed due to the interaction of the separated shear layers at solid volume fraction ≥ 0.1. As the flow blockage increased, the distance from the back of the patch (where the recirculation and large‐scale vortices developed) decreased. The suspended sediment deposition was observed within and downstream of the patch, where the velocity and turbulence were diminished. When the flow blockage was low, deposition in the wake region occurred over a long distance. When the flow blockage was large enough to develop the vortex street, the enhanced deposition occurred in two regions immediately downstream of the patch and within the recirculation zone. For sufficiently high flow blockages, however, the recirculation zone was the only location of enhanced deposition in the wake region. The region of enhanced deposition was observed both in the patch and the wake region as 0.84 ≤ u*/u*c (ratio of the friction velocity to the critical friction velocity) ≤ 1.35, whereas reduced deposition occurred in the wake region as u*/u*c (associated with sediment size) decreased. The deposited region in the wake region corresponded to the length scale of vortex formation regardless of sediment size.
When applying the slip form system, the early setting time of concrete corresponds to the hardening time of early-age concrete indicating that cast-in-place concrete has developed sufficient strength to be safely stripped off the form. This hardening time is thus an important indicator for the determination of the slip-up velocity of the slip form system. Therefore, need is for a technique enabling to evaluate the early hardening time of concrete in order to secure the safety of the slip form system and the quality of the constructed concrete. Among the methods using ultrasonic waves, this paper applies the surface wave velocity to evaluate the degree of hardening of concrete so as to estimate the early setting time and decide the slip-up time of the slip form system. To that goal, penetration resistance test, compressive strength test and surface wave velocity measurement test are performed concurrently with respect to the mix materials and curing temperature of concrete. The test results are used to derive the relationship between the compressive strength and surface wave velocity according to the early hardening time of concrete. Continuous wavelet transform is applied for the measurement of the surface wave velocity. The validity of the application of the continuous wavelet transform is verified through numerical analysis. Finally, the surface wave velocity required for the slip-up of the slip form system is proposed and the applicability of the proposed surface wave velocity for the determination of the climbing time of the slip form system is verified by means of tests on a reduced-scale slip form system prototype.
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