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Movement of water particles is circular and the orbit gets
smaller with depth until there is no motion at L/2.
Movement of water parcels is elliptical and the orbit gets
flatter until it is just a back and forth movement at
the bottom.
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4. N¨ng l-îng sãng
1. Ph- ¬ng tr×nh ®éng n¨ng sãng .
2. Ph- ¬ng tr×nh thÕ n¨ng.
dE dx zdz gdx
t
. . . ..
0
2
2
....
4
12
agEt
3. N¨ng l- îng toµn phÇn cña chÊt ®iÓm n- íc.
E h
8
2
. .
E = E® + Et
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4. Tèc ®é nhãm sãng
21
21
CC
CC
Cn
§Þnh nghÜa
Tèc ®é nhãm sãng lµ lo¹i tèc ®é ®Æc tr- ng mang n¨ng
l- îng sãng theo ph- ¬ng truyÒn sãng.
(4.1)
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4. Tèc ®é nhãm sãng (tt)
CC
sh
n
212
2
( )
CCC
n
212
2
CC C
C C
C
C
C
n
2
2 2
- NÕu C1C2C
-Khi th× (3) tiÕn tíi (2), cßn khi th× ,
khi ®ã tèc ®é nhãm sãng ®- îc tÝnh nh- lµ:
-§èi víi vïng n- íc n«ng
H
(4.2)
(4.3)
(4.4)
H
0
2)2( sh
S
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shallow water
breaking criterium
0.0001 0.001 0.01 0.1 1.0
0.001
0.0001
0.01
0.1
cnoidal
waves
linear wave theory
(Airy)
Stokes 2nd order
Stokes 3rd order
Stokes 5th order
2
H
gT
2
d
gT
0.142
H
L
0.78
H
d
deep water
breaking criterium
226
H
gT
Applicability of wave theoriesApplicability of wave theories
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5. Qu¸ tr×nh h×nh thµnh sãng giã
Giai ®o¹n æn ®Þnh
Giai ®o¹n ph¸t sinh
Giai ®o¹n triÖt tiªu
Giai ®o¹n ph¸t triÓn