PHASE-LAG EFFECTS IN OSCILLATORY SHEET FLOW

Proceedings of the International Conference on Coastal Engineering

Jan S. Ribberink²  C. Marjolein Dohmen-Janssen¹  Gizella van der Hout¹ 

[1] Delft University of Technology, Hydraulics & Offshore Eng. Section;University of Twente, Section of Civil Eng. & Management

关键词: sheetflow;    oscillatory flow;    phase lag;   

DOI  :  10.9753/icce.v26.%p

学科分类：建筑学

来源: Coastal Engineering Research Council

【 摘 要 】

It is often assumed that in sheet flow conditions the transport rate in oscillatory flow behaves quasi-steady, i.e. showing a direct relation with the instantaneous flow velocity (e.g. Ribberink et ah, 1994). In this paper it will be shown that this assumption is not always valid. Therefore a new semi-unsteady sand transport model is developed which takes into account phase-lag effects of the sediment on the net transport rate. In order to verify this new semi-unsteady model and two existing quasi-steady models, new experiments were performed in the Large Oscillating Water Tunnel (LOWT) of WLDELFT HYDRAULICS. Together with earlier experiments these measurements form a data set of net sand transport rates of uniform sand for three different grain sizes (D50 = 0.13; 0.21 and 0.32 mm) in combined wave-current sheetflow conditions. The verification shows that phase-lag effects become important for a combination of fine sand, large flow velocities and small wave periods. Under these conditions the quasi-steady models cannot predict the behaviour of the net transport rates correctly and the predictions of the new semi-unsteady model show much better agreement.

【 授权许可】

Unknown