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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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6.6.1 Riemann shocktube ± a transient problem in one<br />

dimension 1<br />

This is treated as a one-dimensional problem. Here an initial pressure di€erence<br />

between two sections of the tube is maintained by a diaphragm which is destroyed<br />

at t ˆ 0. Figure 6.2 shows the pressure, velocity and energy contours at the seventieth<br />

time increment, and the e€ect of including consistent and lumped mass matrices is<br />

illustrated. <strong>The</strong> problem has an analytical, exact, solution presented by Sod 57 and<br />

the numerical solution is from reference 1.<br />

6.6.2 Isothermal ¯ow through a nozzle in one dimension<br />

Here a variant of the Euler equation is used in which isothermal conditions are<br />

assumed and in which the density is replaced by a where a is the cross-sectional<br />

ρ<br />

1.000<br />

0.425<br />

0<br />

t = 0<br />

u Lumped mass<br />

e<br />

2.5<br />

2.0<br />

Some preliminary examples for the Euler equation 177<br />

t = 18.5<br />

Consistent<br />

mass<br />

Fig. 6.2 <strong>The</strong> Riemann shocktube problem. 1;57 <strong>The</strong> total length is divided into 100 elements. Pro®le illustrated<br />

corresponds to 70 time steps ( t ˆ 0:25). Lapidus constant C Lap ˆ 1:0.

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