From fd05b50e5ccf463bc86ffcd19c520754e5bc03e7 Mon Sep 17 00:00:00 2001
From: rhaas <rhaas@ac85fae7-cede-4708-beff-ae01c7fa1c26>
Date: Fri, 11 Jan 2013 15:04:15 +0000
Subject: GRHydro_InitData: add parameter to offset radial origin

r_code = r_KS - r0 with r0=1M by default. This avoids placing the
central singularity on the grid.

From: Roland Haas <roland.haas@physics.gatech.edu>

git-svn-id: http://svn.einsteintoolkit.org/cactus/EinsteinInitialData/GRHydro_InitData/trunk@196 ac85fae7-cede-4708-beff-ae01c7fa1c26
---
 param.ccl            |  5 +++++
 src/GRHydro_BondiM.c | 15 +++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/param.ccl b/param.ccl
index 51c4c9d..1eb8e46 100644
--- a/param.ccl
+++ b/param.ccl
@@ -381,6 +381,11 @@ CCTK_REAL bondi_bmag "B_0 parameter for magnetized Bondi"
   0:* :: "Anything positive"
 } 0.01
 
+CCTK_REAL bondi_radial_offset "redefine r_grid=r_KS-r0 to avoid singularity on grid"
+{
+  0:* :: "Any positive number"
+} 0.0
+
 CCTK_BOOLEAN set_bondi_beta_sonicpt "Set plasma beta parameter instead of bondi_bmag"
 {
 } no
diff --git a/src/GRHydro_BondiM.c b/src/GRHydro_BondiM.c
index ef7c1c5..f947abb 100644
--- a/src/GRHydro_BondiM.c
+++ b/src/GRHydro_BondiM.c
@@ -1097,6 +1097,21 @@ void GRHydro_BondiM(CCTK_ARGUMENTS)
     xpos[YY] = y[i] ;
     xpos[ZZ] = z[i] ;
 
+    if (bondi_radial_offset > 0.) {
+      double rspher_orig = sqrt(SQR(xpos[XX])+SQR(xpos[YY])+SQR(xpos[ZZ]));
+      double rspher_new = rspher_orig + bondi_radial_offset;
+      if(rspher_orig < SMALL_BONDI) { 
+        xpos[XX] = rspher_new;
+        xpos[YY] = 0.;
+        xpos[ZZ] = 0.;
+      } else {
+        for(int n = XX ; n <= ZZ ; n++) {
+          xpos[n] *= rspher_new/rspher_orig;
+        }
+      }
+    }
+
+
     switch( coord_type ) {
   
     case COORD_BOYERLINDQUIST :
-- 
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