Function dynamic_pressure_kernel 

pub fn dynamic_pressure_kernel<R>(
    rho: &Density<R>,
    u: &Speed<R>,
) -> Result<Pressure<R>, PhysicsError>
where
    R: RealField + FromPrimitive,

Dynamic pressure q = 0.5 · ρ · u² (Pa).

Always non-negative since ρ ≥ 0 (Density invariant) and u² ≥ 0.