Numerical modeling of waves for a tsunami early warning system
Numerical modeling of waves for a tsunami early warning system
Numerical modeling of waves for a tsunami early warning system
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<strong>Numerical</strong> <strong>modeling</strong> <strong>of</strong> <strong>waves</strong> <strong>for</strong> a <strong>tsunami</strong> <strong>early</strong> <strong>warning</strong> <strong>system</strong><br />
∇h (ccg∇ha)+k 2 ccga =0 (B.4)<br />
which comes from the assumption made on the free surface elevation <strong>of</strong><br />
being time harmonic, as follows<br />
η (x, y, t) =a (x, y) · e iωt<br />
the first term <strong>of</strong> equation (B.4) can be expanded so that it yields to<br />
(B.5)<br />
(ccg) x ax + ccgaxx +(ccg) y ay + ccgayy + k 2 ccga =0 (B.6)<br />
The derivatives <strong>of</strong> the first order which compare in equation (B.6) become<br />
ax = auux + avvx<br />
ay = auuy + avvy<br />
(ccg) x =(ccg) u ux +(ccg) v vx<br />
(ccg) y =(ccg) u uy +(ccg) v vy<br />
For the derivatives <strong>of</strong> the second order it become<br />
axx =(ax) x =(ax) u ux +(ax) v vx =<br />
=(auux + avvx) u ux +(auux + avvx) v vx =<br />
=[auuux + au (ux) u + auvvx + av (vx) u ] ux+<br />
[auvux + au (ux) v + avvvx + av (vx) v ] vx =<br />
= auuu 2 x + auux (ux) u + auvvxux + avux (vx) u +<br />
auvuxvx + auvx (ux) v + avvv 2 x + avvx (vx) v =<br />
= auuu 2 x + avvv 2 x +2auvvxux + au (ux) x + av (vx) x<br />
and similarly <strong>for</strong> the second derivative in y:<br />
ayy =(ay) y =(ay) u<br />
uy +(ay) v<br />
vy =<br />
=(auuy + avvy) u<br />
uy +(auuy + avvy) v<br />
vy =<br />
= <br />
<br />
auuuy + au (uy) u + auvvy + av (vy) u<br />
<br />
auvuy + au (uy) v + avvvy + av (vy) v<br />
uy+<br />
<br />
vy =<br />
= auuu 2 y + auuy (uy) u + auvvyuy + avuy (vy) u +<br />
auvuyvy + auvy (uy) v + avvv 2 y + avvy (vy) v =<br />
= auuu 2 y + avvv 2 y +2auvvyuy + au (uy) y + av (vy) y<br />
finally the first and third terms <strong>of</strong> equation (B.6) becomes<br />
(B.7)<br />
(B.8)<br />
(B.9)<br />
Università degli Studi di Roma Tre - DSIC 114