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A common shortcoming of the two-phase k-��k-�� models has been its inability to reproduce the large concentration peaks that can happen near flow reversals (e.g., [26]?and?[39]). In comparison, single phase [https://en.wikipedia.org/wiki/Lazabemide lazabemide] k-��k-�� models [25] and the present two-phase k-��k-�� model (Fig. 1?and?Fig. 2) do produce such peaks of suspended sediment concentration near flow reversal. Could this be a clear superiority of the k-��k-�� model? To investigate this issue further, we present the phase-averaged sediment concentration in the sheet layer obtained from experiments and each model for cases MA7515 and CA7515 in Fig. 7?and?Fig. 8 respectively. The peaks of suspended sediment concentration near flow reversal are easily distinguishable in the k-��k-�� model results (panel (d)). However, these peaks are also very clearly correlated in time with a brief erosion of the bed (see red contours in both figures). The explanation for this combined behaviour lies in the fundamental sediment mass balance used in the model. In the present one-dimensional vertical (1DV) model, the overall mass is conserved in the numerical domain, which goes from within the sediment throughout the boundary layer. A peak in suspended sediment would therefore necessarily be associated with a temporary erosion of the bed. As mentioned previously, this behaviour near flow reversal is not observed in the numerical results from the k-��k-�� model, for which both features are absent. These disparities between the two models around flow reversals have been related to the differences in [http://www.selleckchem.com/products/ABT-888.html Veliparib] the singularity of the eddy viscosity when turbulent variables (k,��,��k,��,��) [http://www.selleckchem.com/products/DAPT-GSI-IX.html DAPT mouse] approach zero (e.g., [25]). This is confirmed in Fig. 9 where significant differences in near-bed eddy viscosity are found around flow reversal, in phase with the concentration peaks. In comparison, the time-dependent behaviour of both k-��k-�� and k-��k-�� models is broadly similar for the near-bed turbulent kinetic energy (Fig. 10). Concentration peaks at flow reversal are now a well-know feature in wave-current sheet flows and are significantly more important for finer grains [40]. The experimental data of [36]?and?[37] for fine sand (respectively D50=130D50=130?�̦�m and D50=150D50=150?�̦�m) do not exhibit the complete combined behaviour of the k-��k-�� model (Fig. 11?and?Fig. 12). In both experiments, peaks in suspended concentration were indeed measured around flow reversal, but a corresponding erosion peak does not seem to occur. In Fig. 11, suspended concentration peaks are evident shortly before t/T=0.5t/T=0.5 in the time histories for z>0z>0, but no drop in concentration, which would be the manifestation of sudden erosion, is observed in the time histories for z