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Zienkiewicz O.C., Taylor R.L. Vol. 3. The finite - tiera.ru

Zienkiewicz O.C., Taylor R.L. Vol. 3. The finite - tiera.ru

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258 Waves<br />

where m is the number of terms in the Hankel function series, r is the radius of the<br />

boundary, L c is the distance between the equidistant nodes on ÿ C, p is the number<br />

of nodes, and H n and H 0 n are Hankel functions and derivatives.<br />

Other authors have worked out the explicit forms of the above matrices for linear<br />

shape functions, and also it is possible to work them out for any type of shape function,<br />

using, if necessary, numerical integration. It will be noticed that the matrix ^K is<br />

diagonal. This is because the boundary ÿ B is circular and the Hankel functions are<br />

orthogonal. If a non-circular domain is used, ^K will become dense. Chen and Mei 36<br />

applied the method very successfully to a range of problems, most notably that of<br />

resonance e€ects in an arti®cial o€shore harbour, the results for which are shown<br />

in <strong>Vol</strong>ume 1, Chapter 17, Fig. 17.6.<br />

<strong>The</strong> method was also utilized by Houston, 38 who applied it to a number of real<br />

problems, including resonance in Long Beach harbour, shown in Fig. 8.6.<br />

Note: Number of node points = 1701<br />

Number of elements = 2853<br />

(a) Finite element grid, grid 3<br />

Scale<br />

3000 0 3000 6000<br />

feet<br />

Fig. 8.6 Finite element mesh and wave height magni®cation for Long Beach Harbour, Houston. 38

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