 What is a shock ? • At the begining of the simulation we disturbe the flow with a velocity such as : .
• The fastest fluid catches up with the slowest one so that to create a velocity break. This phenomena is called shock.
• We can notice that if the disturbance was : the contrary would have happen : the slope would have decreased.

How can you see the viscosity?
• The viscosity tends to erase the disturbance in the flow. Bigger the viscosity is, faster the disturbance has no more effect.
• Following are three results that can show this role.
• viscosity = 0.0001 m2/s
• The shock appears.
• The viscosity makes the difference of velocity decrease till there is no more break. • viscosity = 0.01 m2/s
• The shock tends to appear. • viscosity = 1 m2/s
• The viscosity is too big to let the shock appear : the disturbance is erased as soon as it appears.
• We can notice that the following schematics time scale is smaller than the previous one. Numerical scattering
• This phenomena appears for small values of the viscosity
• It produces oscillations oscilation around the shock. • We can notice that the numerical scattering depends on the numerical variables. It appears sooner (for bigger values of the viscosity) when is bigger.
 viscosity  0.01 m2/s  0.001 m2/s  0.0001 m2/s   