2. Perfect fluid hypothesis

2.1 Entropy conservation

The solution to the entropy equation (4) is very simple when the dissipative terms due to viscosity and thermal conductivity are negligible. This is the case for a perfect fluid for which :

• the mechanical tension is normal to each surface element and independent of its orientation: T _ij = – pδ _ij ;

• the heat flow is zero: q _i = 0 ;

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