GLOSSARY

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A state of a thermodynamic system near to thermodynamic equilibrium in a sense that at any moment of time t and any spatial location  \bf r there is a small area of space where fluid can be considered as being at thermodynamic equilibrium during some period of time.


Particularly in fluid dynamics it means that:

(1) T=T(t, {\bf r})


the fluid temperature is fully determined at any point in time t and any spatial location {\bf r} = (x,y,z) of a fluid flow

(2) p=p(t, {\bf r})


the fluid pressure is fully determined at any point in time t and any spatial location {\bf r} = (x,y,z) of a fluid flow

(3) \rho = \rho(p, T)=\rho(p(t, {\bf r}), T(t, {\bf r}))


fluid density is a function of pressure p and temperature T only, so that it depends on time t and spatial location {\bf r} = (x,y,z) implicitly

(4) \mu = \mu(p, T)=\mu(p(t, {\bf r}), T(t, {\bf r}))


fluid viscosity is a function of pressure p and temperature T only, so that it depends on time t and spatial location {\bf r} = (x,y,z) implicitly

(5) \lambda = \lambda(p, T)=\lambda(p(t, {\bf r}), T(t, {\bf r}))


fluid thermal conductivity is a function of pressure p and temperature T only, so that it depends on time t and spatial location {\bf r} = (x,y,z) implicitly

(6) c_p = c_p(p, T)=c_p(p(t, {\bf r}), T(t, {\bf r}))


fluid isobaric specific heat capacity is a function of pressure p and temperature T only, so that it depends on time t and spatial location {\bf r} = (x,y,z) implicitly

(7) \alpha = \alpha(p, T)=\alpha(p(t, {\bf r}), T(t, {\bf r}))


fluid Joule–Thomson coefficient is a function of pressure p and temperature T only, so that it depends on time t and spatial location {\bf r} = (x,y,z) implicitly

(8) G \rightarrow \rm min \ \Leftrightarrow \mathrm{d}G = 0


The Gibbs free energy is at minimum

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