Closed Qcellaris closed 1 year ago
Hi Stephen,
The stepper is correct.
See that the auhat is computed with a negative sign
here d_u
is updated
So when we add auhat
in
we have
d_u (old) + dtb2 * (au - auhat)
and the negative sign is already taken care in the equation.
I hope this clears the doubt.
You are completely right, I didn't look carefully enough. Thanks for your reply!
Dear developers,
When we look at equation 13 in "A transport-velocity formulation for smoothed particle hydrodynamics", by Adami, Hu and Adams 2013, we see the term: $$\frac{\tilde d\mathbf{v}_i}{dt}-\frac{p_b}{m_i}\sum_j(V^2_i+V^2j)\frac{\partial W}{\partial r_{ij}}\mathbf{e}\{ij}$$ of which the first term is computed in equation 8. In the TVFScheme of pysph the result is stored in au, av and aw. The second term is stored in pysph as auhat, avhat and awhat. Then if we look at the time integration:
We see that in the update of the advection velocity auhat, avhat and awhat are used. If I look at the paper correctly the background pressure force of equation 15 consists of both terms so I think it should be (au-auhat), (av-avhat) and (aw-awhat), i.e.: