A triple frequency AQUAscat ABS system was employed to measure finernsediment suspension under sheet flow conditions generated in a laboratory oscillatory Utubernwith both symmetric and asymmetric waves. A numerical direct inversion approach,rnwhich was based on wave-period-averaged sediment concentration from independentrnmeasurements to convert the ABS signals to the sediment concentration, was described inrnthis paper. The comparison of the sediment concentration measured by the ABS systemrnand a suction sampler showed that the new proposed direct conversion approach workedrnsatisfactorily in the present study. The results also revealed that the low frequency ABSrnmeasurements yielded better agreement for both wave-period-averaged and intra-waveperiodrnconcentrations than the higher frequency ABS measurements due to the highrnattenuation.
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