M. Boechat Albernaz1*, N. Geleynse1, D. Schoonhoven1, M. Teunis2, L. Perk1, R Snoek1, W. Lengkeek2
1 WaterProof BV; 2 Waardenburg Ecology
The Sand Wing development is part of Rijkswaterstaat's innovation program for coastline maintenance. The project studies the feasibility of a near bed fixed structure, i.e. the Sand Wing, in contributing to sand transport and the maintenance of sandbanks. The structure should extend the lifetime of sediment nourishments or reducing the need for them.
We tested the Sand Wing ogive configuration by means of physical experiments. The physical experiments were performed in a flume (13 x 0.45 x 0.25m) and in a basin (race track basin with 4 x 2 x 0.35m). The experiments enclosed flow-only conditions over a fixed bed and experiments with a mobile sand bed covering different mobility scenarios. Measurements of flow, turbulence and sediment concentrations were carried out for conditions without the wing (reference case) and with different Sand Wing angles wrt to the main flow.
The Sand Wing in its current configuration is able to enhance sand suspension and to deflect the sand transport laterally. Both effects are highly desirable for the sandbank application. The physical experiments were able to unravel the conceptual working principle of the structure and also to quantify the turbulence and the resulting sand transport and deposition. The sand transport and deposition with the Sand Wing are a factor of 2-3 higher than the reference. The next phases of the project contemplate the assessment of the structure in numerical models and possibly a pilot project.
Figure 1: Flume experiments of the Sand Wing with mobile sand bed. Left: Sand Wing with 30º orientation; Right: no Sand Wing. Both experiments were performed with 0.3 m/s flow velocity.