Determination of Thickness of the Sediments in a Rectangular Pipe by Modal Frequencies´ Shift

This paper presents an approach which estimates the depth of the porous sediments on the bottom of a rectangular pipe by comparing the measured propagation modespsila frequencies to that calculated by finite element method (FEM). It is validated by comparing the calculated results to the theoretical results for the rectangular pipe with rigid boundary condition and to the experimental results with sediments laid on the bottom of the rectangular flume. The comparison results show that the disagreements between measured depth and the calculated depth are less 3 percent. This method can be used to monitoring or measuring the depth of the sediments on the bottom of a pipe.