USER MANUAL SWAN Cycle III version 40.72A

Appendix A
Definitions of variables
In SWAN a number of variables are used in input and output. Most of them are related
to waves. The definitions of these variables are mostly conventional.
HSIGN
Significant wave height, denoted as H s in meters, and defined as
H s = 4√ ∫ ∫ E(ω,θ)dωdθ
where E(ω,θ) is the variance density spectrum and ω is the absolute
radian frequency determined by the Doppler shifted dispersion relation.
However, for ease of computation, H s can be determined as follows:
H s = 4√ ∫ ∫ E(σ,θ)dσdθ
HSWELL
Significant wave height associated with the low frequency part of
the spectrum, denoted as H s,swell in meters, and defined as
H s,swell = 4√ ∫ ωswell
0
∫ 2π
0 E(ω,θ)dωdθ
TMM10
with ω swell = 2πf swell and f swell = 0.1 Hz by default (this can be changed
with the command QUANTITY).
Mean absolute wave period (in s) of E(ω,θ), defined as
∫ ∫ ∫ ω
T m−10 = 2π
−1 E(ω,θ)dωdθ
∫ ∫ ω
E(ω,θ)dωdθ
= 2π∫ −1 E(σ,θ)dσdθ
∫ ∫ E(σ,θ)dσdθ
TM01
Mean absolute wave period (in s) of E(ω,θ), defined as
(∫ ∫ ) −1 (∫ ∫ ) −1
ωE(ω,θ)dωdθ
T m01 = 2π ∫ ∫ ωE(σ,θ)dσdθ
E(ω,θ)dωdθ
= 2π ∫ ∫ E(σ,θ)dσdθ
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