
Calibration Parameters
143
For uniform particle sizes, Engelund (1953) suggests the following range of
values for the laminar and turbulent resistance coefficients:
Porosity - scientific background
For Boussinesq wave simulations, the equations in MIKE 21 BW have been
modified to include porosity and the effects of non-Darcy flow through porous
media. In this way, it is possible for MIKE 21 to model partial reflection,
absorption and transmission of wave energy at porous structures such as
rubble mound breakwaters (see e.g. Madsen and Warren (1984) and Madsen
(1983)).
The main effects of porosity are introduced by additional laminar and turbu-
lent friction terms for describing losses due to flow through a porous struc-
ture. In most practical cases the pore sizes are relatively large (typically 0.1 m
to 1.0 m), and the turbulent losses will dominate. The laminar loss term has
also been included to allow the simulation of small scale physical model tests.
The flow resistance inside the porous structure is described by the non-linear
term
(5.6)
where
and
account for the laminar and turbulent friction loss, respectively,
and
U
is the velocity.
and
are determined by the empirical expressions
recommended by Engelund (1953):
(5.7)
where:
Laminar
Turbulent
Spherical particles
780
1.8
Rounded particles
1000
2.8
Angular particles
up to 1500
up to 3.6
n
=
porosity (pore volume/unit volume)
=
kinematic viscosity of water
d
=
a characteristic diameter of the structure units (the grain size)
0
=
a laminar particle form resistance coefficient
0
=
a turbulent particle form resistance coefficient
+
U
U
0
1
n
–
3
n
2
-------------------
d
2
-----
0
1
n
–
n
3
----------------- 1
d
---
=
=
Содержание 21 BW
Страница 1: ...MIKE 2017 MIKE 21 BW Boussinesq Waves Module User Guide...
Страница 2: ...2...
Страница 4: ...4 MIKE 21 BW DHI...
Страница 13: ...General Description 13 Figure 2 4 Simulation of wave penetration into Frederikshavn harbour Denmark...
Страница 16: ...Introduction 16 MIKE 21 BW DHI...
Страница 75: ...2DH Boussinesq Wave Module Examples 75 Figure 4 45 Visualisation 2D of instantaneous surface elevation...
Страница 185: ...Entries Arranged Alphabetically 185 Figure 5 58 Application of different time extrapolation factors...
Страница 190: ...Reference Manual 190 MIKE 21 BW DHI...
Страница 192: ...Scientific Documentation 192 MIKE 21 BW DHI...
Страница 193: ...193 INDEX...