1 files changed, 3 insertions, 0 deletions
diff --git a/param.ccl b/param.ccl
index 3c05d85..2fb9026 100644
--- a/param.ccl
+++ b/param.ccl
@@ -63,6 +63,9 @@ CCTK_REAL TOV_Position_z[10] "Position of neutron star, z coordinate" STEERABLE=
   *:* :: "real"
 } 0.0
 
+# contravariant fluid three velocity as measured by the Eulerian observers: v^i = u^i / (alpha u^t) + beta^i / alpha
+# as used by HydroBase. Follows the Valencia formulation eg. eqs. 26 and 27 of Font et al's paper (gr-qc/9811015) or 
+# below Equ. 31 in http://relativity.livingreviews.org/Articles/lrr-2008-7/articlesu1.html#x6-30002.1
 CCTK_REAL TOV_Velocity_x[10] "(fixed) Velocity of neutron star, x coordinate (caution!)" STEERABLE=always
 {
   *:* :: "real"