| ATTRIBUTE | VALUE |
|---|
| type | A |
| database id | 3829 |
| title | Bedload transport due to waves versus laboratory experiments |
| authors | Kaczmarek L. M., O`Connor B. A., Zeidler R. B. |
| pages | 45 — 76 |
| full text link | http://www.ibwpan.gda.pl/storage/app/media/ahem/ahem45no14str045.pdf |
| affiliations | - Institute of Hydro-Engineering of Polish Academy of the Sciences, ul. Kościerska 7, 80-952 Gdańsk, Poland
- University of Liverpool, Dept. of Civil Engineering, Brownlow Street, P.O. Box 147, Liverpool L69 3 Bx, Great Britain
|
| abstracts | The transport of sediment as bedload under wave action is studied both theoretically and experimentally. A theoretical approach based on grain-grain interaction ideas is proposed in analogy to the flow of dry, cohesionless materials. Nearbed sediment dynamics is modelled in two regions i.e. a collision-dominated granular-fluid region and a bed-bounded turbulent fluid shear region with continuous profiles of stress and velocity connecting both regions. An iteration procedure is employed to match the velocity and shear stress profiles in both regions using a theoretical bed level for the outer wave-induced flow of δsx, which is taken as an arbitrary fraction of the thickness of the moving, collision-dominated bed layer, δn. Previous comparisons with experimental data had suggested a value of δsx/δn = 0.5. The model has been operated for a range of sediments and for both low and high wave conditions. Comparison of model results with a range of experimental data suggests that the model provides realistic answers for both bed roughness and bedload transport thicknesses and rates for flat bed conditions provided variable values of δsx/δn ≤ 0.50 are used. For sheet-flow conditions rea1istic values for bed roughness, bedload concentration and transport rate are obtained for δsx/δn = 0.50, although further model modifications are required to include the effects of suspended load. Finally, the model was found to produce realistic values of bed roughness and sediment transport rates for rippled bed conditions, provided δsx/δn = 0.50, which provides a measure of compensation for form drag, which is not explicitly included in the model. |
| attributes | [reviewed] [scientific] |
| language | en |
| points | 6 |
| ATTRIBUTE | VALUE |
|---|
| type | A |
| database id | 3830 |
| title | Contact load model and sediment transport due to waves versus laboratory data |
| authors | Kaczmarek L. M., Ostrowski R. |
| pages | 77 — 100 |
| full text link | http://www.ibwpan.gda.pl/storage/app/media/ahem/ahem45no14str077.pdf |
| affiliations | - Institute of Hydro-Engineering of the Polish Academy of Sciences, Kościerska 7, 80-953 Gdańsk, Poland
|
| tasks | Z 2.2.2/1998: Opracowanie teoretycznego modelu przebudowy profilu dna z uwzględnieniem warunków losowego ruchu falowego |
| abstracts | A contact load layer model is presented, dealing with the effect of suspended sediment on total sediment transport near the bed. The contact load layer is identified as the transition zone between the outer region (suspension layer) and the bedload layer. First, the physical aspects of momentum transfer are discussed and the contact layer is defined. Further, following Deigaard (1993) a new formulation of the skin friction being a combination of turbulence and the collisions between the grains, based on the diffusion concept, is postulated. Making use of the proposed solution procedure, the new system of equations is employed to compute time-dependent sediment concentration and velocity, wave-period-average concentration and transport rate (net and average in half period), together with the determination of two calibration coefficients, basically unknown in Deigaard's (1993) approach. The bedload model of Kaczmarek et al. (published simultaneously) provides the boundary conditions for the solution of the contact load layer. The comparisons between the model results and available laboratory data yield satisfactory conformity. Significant discrepancies between the model results and experimental data are found at higher level above bed. They are most probably Jinked to convective events in flow reversal. |
| attributes | [reviewed] [scientific] |
| language | en |
| points | 6 |