For the suspended sediment discharge:
(6)
Calculate Z for each size fraction using Equation 4.41
Calculate E = 2Ds / yo for each fraction
(7)
Determine l1 and l2 for each fraction from Figures 4.9 and 4.10
(8)
Calculate PE using Equation 4.32
(9)
(10)
Compute the suspended discharge from IB qB (1 + PE I1 + I2) from Equation 4.31
Sum up all the qB and all the iB to obtain the total suspended discharge Qss
(11)
Thus, the total bed sediment discharge is computed as:
(12) Add the results of Step 5 and 11.
A sample problem showing the calculation of the total bed sediment discharge using
Einstein's procedure is presented in Section 4.13.
4.5.3 Comparison of Meyer-Peter and Mller and Einstein Contact Load Equations
Chien (1954) has shown that the Meyer-Peter and Mller, equation can be modified into the
form
3/2
4
φ* =
- 0.188
(4.45)
ψ
*
Figure 4.12 shows the comparison of Equation 4.45 with Einstein's ψ* vs. φ* relation for
uniform bed sediment size and for sediment mixtures using D35 in the Einstein relation and
D50 in the Meyer-Peter and Mller relation. They show good agreement for coarse sands,
but diverge for fine sands. This supports the premise that the Meyer-Peter and Mller
equation is most applicable to coarse grain sizes with little or no suspended load.
Figure 4.12. Comparison of the Meyer-Peter and Mller and Einstein methods for
computing contact load (Chien 1954).
4.21
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