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Implicit-Explicit Runge-Kutta schemes for hyperbolic systems ... - utenti

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Order conditions<br />

Assume<br />

˜ci = �<br />

j ãi,j, ci = � �<br />

j<br />

ai,j,<br />

i ˜wi = 1, �<br />

i wi = 1.<br />

then the analysis can be limited to autonomous <strong>systems</strong> and the first order conditions<br />

are automatically satisfied.<br />

Second order:<br />

�<br />

i ˜wi˜ci = 1/2, �<br />

i wici = 1/2, �<br />

i ˜wici = 1/2, �<br />

i wi˜ci = 1/2,<br />

Third order:<br />

�<br />

ij ˜wiãij˜cj = 1/6, �<br />

i ˜wi˜ci˜ci = 1/3, �<br />

ij wiaijcj = 1/6, �<br />

i wicici = 1/3,<br />

Mixed conditions:<br />

�<br />

ij ˜wiãijcj = 1/6, �<br />

ij ˜wiaij˜cj = 1/6, �<br />

ij ˜wiaijcj = 1/6,<br />

�<br />

ij wiãijcj = 1/6, �<br />

ij wiaij˜cj = 1/6, �<br />

ij wiãij˜cj = 1/6,<br />

�<br />

i ˜wicici = 1/3, �<br />

i ˜wi˜cici = 1/3,<br />

�<br />

i wi˜ci˜ci = 1/3, �<br />

i wi˜cici = 1/3.<br />

Remark If wi = ˜wi and ci = ˜ci, then mixed conditions are automatically satisfied. This is<br />

not true <strong>for</strong> higher that third order accuracy<br />

8

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