Dp=0.5000 m (about 20 inch)

   05: Dp=0.5000 m, The Limit Deposit Velocity, Slip Factor & The Bed Fraction

For the Limit Deposit Velocity a set of standard graphs is created for a spatial or transport volumetric concentration of 17.5%.

At this concentration the LDV is at a maximum.

For the slip factor and the bed fraction a set of standard graphs is created for a transport volumetric concentration of 17.5%.

For other concentrations the graphs may differ, especially the volumetric transport concentration graphs. 


The Limit Deposit Velocity versus the Particle Diameter

The Limit Deposit Velocity is defined as the line speed above which no fixed or sliding bed is present. Below the Limit Deposit Velocity there is either a fixed or a sliding bed. The Limit Deposit Velocity curve is constructed out of 5 curves and is dependent on the concentration. The graph below shows the 5 curves and the resulting curve for a 17.5% volumetric concentration. The 5 curves are:

  1. Very small particles, the LDV is based on a sliding bed in the viscous sub-layer (the red curve, left part).
  2. Small particles, the LDV is based on the potential energy required to keep the particles in suspension (the red curve).
  3. Medium particles, a transition region between small and large particles.
  4. Large particles, the LDV is based on a limiting sliding bed in turbulent flow (the green curve left part).
  5. Very large particles (d/Dp>0.015), the LDV is based on increasing porosity in a sliding bed, named sliding flow (the green curve right part).

The LDV has a lower limit based on the transition line speed between the sliding bed regime and the heterogeneous flow regime. This lower limit depends on the sliding friction coefficient (the brown curves).

The Durand Froude Number FL for the Limit Deposit Velocity versus the Particle Diameter

Since in dredging the concentration is not a constant, the Limit Deposit Velocity curves are plotted in the following graph for concentrations of 1% up to 25%. By doing this a lower and an upper limit can be defined for the Limit Deposit Velocity.

The Bed Fraction & Slip Factor versus the Line Speed

Knowing the Limit Deposit Velocity, the slip factor can be constructed and based on the slip factor, the bed fraction or bed height. Also the spatial volumetric concentration Cvs based on a constant delivered volumetric concentration Cvt is shown.




 Login | Home | Resources | Site map | Traffic | 105 active visitors 

Fullxml powered website © fullxml.org
Last updated
Copyright 2001- © Dr.ir. S.A. Miedema - all rights reserved



Copyright © Dr.ir. S.A. Miedema

Send email to WebMaster with questions or comments about this website.