From a8caad1ade24f21b9de039150ec4c75419d8eedc Mon Sep 17 00:00:00 2001
From: Miikka Vaisala <mvaisala@asiaa.sinica.edu.tw>
Date: Thu, 18 Jul 2019 17:34:09 +0800
Subject: [PATCH] A draft of the sink particle plan.

---
 doc/manual/convert.sh       |  1 +
 doc/manual/sink_particle.md | 44 +++++++++++++++++++++++++++++++++++--
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/doc/manual/convert.sh b/doc/manual/convert.sh
index ad47094..39d997c 100755
--- a/doc/manual/convert.sh
+++ b/doc/manual/convert.sh
@@ -1 +1,2 @@
 pandoc sink_particle.md -o sink_particle.html --mathml
+pandoc manual.md -o manual.html --mathml
diff --git a/doc/manual/sink_particle.md b/doc/manual/sink_particle.md
index 4e8eabf..eb86610 100644
--- a/doc/manual/sink_particle.md
+++ b/doc/manual/sink_particle.md
@@ -27,6 +27,10 @@ Based on `sink` gravitational force effect is added to the momentun equation (vi
 
 ## Stage 4: Accretion
 
+This part of the process is most complicated, and will require special
+attention.  The starting point should be the Truelove criterion, but we migh
+need additional subgrid model assumptions. 
+
 Jeans length
 \begin{equation}
 \lambda_\mathrm{J} = \Big( \frac{\pi c_s^2}{G \rho} \Big)^{1/2}
@@ -36,8 +40,44 @@ Truelove-Jeans density.
 \begin{equation}
 \rho_\mathrm{TJ} = \frac{\pi J^2 c_s^2}{G \Delta x^2}
 \end{equation} 
-where $J = \Delta x / \lambda_\mathrm{J}$
+where $J = \Delta x / \lambda_\mathrm{J}$. Lee et al. (2014) set $J=1/8$.
+
+Magnetic Truelove criterion
+\begin{equation}
+\rho_\mathrm{TJ, mag} = \rho_\mathrm{TJ} (1 + 0.74/\beta)
+\end{equation}
+
+Accreted mass 
+\begin{equation}
+ (\rho - \rho_\mathrm{TJ, mag})\Delta x^3
+\end{equation}
 
 ## Stage 5: Data gathering (device to host)
 
-We need to combine accretion calculated in multiple GPUs.  
+After accretion we will need to gather all data to `sink.mass`. This might need gathering from multiple GPUs, i.e. like in 
+
+Depends on the stencils size and shape used for at the accretion stage. Currently the method is not clear. 
+
+## Plan 
+
+### 1. Add gravitating particle
+
+Add a particle with specific mass and location. No accretion included. 
+
+### 2. Add simple accretion
+
+Add an accretion property of the particle. Use just a basic form. 
+
+### 3. Add Complicated accretion
+
+Add accretion properties which might be useful for the sake of physical correctness and/or numerical stability. 
+
+### 4. Add particle movement. (OPTIONAL)
+
+Make is possible for the particle to accrete momentum in addition to mass, and therefore influence its movement. 
+
+### 5. Multiple particles. (VERY OPTIONAL)
+
+Create sink particles dynamically and allow the presence of multiple sinks. 
+
+