diff --git a/src/hydro/Gadget2/hydro_iact.h b/src/hydro/Gadget2/hydro_iact.h
index b604f7d4a812df0f973bb1f1acde7a5286cc9bfb..f92531bcce30d6c1461bb1366f88bc282a2747e7 100644
--- a/src/hydro/Gadget2/hydro_iact.h
+++ b/src/hydro/Gadget2/hydro_iact.h
@@ -37,8 +37,6 @@
*errors and interactions
* missed by the Gadget-2 tree-code neighbours search.
*
- * The code uses internal energy instead of entropy as a thermodynamical
- *variable.
*/
/**
@@ -142,9 +140,6 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_density(
pi->density.wcount += wi;
pi->density.wcount_dh -= u * wi_dx;
- /* const float ih3 = h_inv * h_inv * h_inv; */
- /* const float ih4 = h_inv * h_inv * h_inv * h_inv; */
-
const float fac = mj * wi_dx * ri;
/* Compute dv dot r */
@@ -154,24 +149,6 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_density(
const float dvdr = dv[0] * dx[0] + dv[1] * dx[1] + dv[2] * dx[2];
pi->div_v -= fac * dvdr;
- /* if(pi->id == 515050 && pj->id == 504849) */
- /* message("Interacting with %lld. r=%e hi=%e u=%e W=%e dW/dx=%e dh_drho1=%e
- * dh_drho2=%e\n fac=%e dvdr=%e pj->v=[%.3e,%.3e,%.3e]", */
- /* pj->id, */
- /* r, */
- /* hi, */
- /* u, */
- /* wi * ih3, */
- /* wi_dx * ih4, */
- /* -mj * (3.f * kernel_igamma * wi) * ih4, */
- /* -mj * u * wi_dx * kernel_igamma * ih4, */
- /* fac * ih4, */
- /* dvdr, */
- /* pj->v[0], */
- /* pj->v[1], */
- /* pj->v[2] */
- /* ); */
-
/* Compute dv cross r */
curlvr[0] = dv[1] * dx[2] - dv[2] * dx[1];
curlvr[1] = dv[2] * dx[0] - dv[0] * dx[2];
@@ -225,28 +202,31 @@ __attribute__((always_inline)) INLINE static void runner_iact_force(
/* Compute sound speeds */
const float ci = pi->force.soundspeed;
const float cj = pj->force.soundspeed;
- float v_sig = ci + cj;
/* Compute dv dot r. */
const float dvdr = (pi->v[0] - pj->v[0]) * dx[0] +
(pi->v[1] - pj->v[1]) * dx[1] +
(pi->v[2] - pj->v[2]) * dx[2];
- /* Artificial viscosity term */
- float visc = 0.f;
- if (dvdr < 0.f) {
- const float mu_ij = fac_mu * dvdr * r_inv;
- v_sig -= 3.f * mu_ij;
- const float rho_ij = 0.5f * (rhoi + rhoj);
- const float balsara_i =
- fabsf(pi->div_v) /
- (fabsf(pi->div_v) + pi->force.curl_v + 0.0001 * ci / fac_mu / hi);
- const float balsara_j =
- fabsf(pj->div_v) /
- (fabsf(pj->div_v) + pj->force.curl_v + 0.0001 * cj / fac_mu / hj);
- visc = -0.25f * const_viscosity_alpha * v_sig * mu_ij / rho_ij *
- (balsara_i + balsara_j);
- }
+ /* Balsara term */
+ const float balsara_i =
+ fabsf(pi->div_v) /
+ (fabsf(pi->div_v) + pi->force.curl_v + 0.0001 * ci / fac_mu / hi);
+ const float balsara_j =
+ fabsf(pj->div_v) /
+ (fabsf(pj->div_v) + pj->force.curl_v + 0.0001 * cj / fac_mu / hj);
+
+ /* Are the particles moving towards each others ? */
+ const float omega_ij = fminf(dvdr, 0.f);
+ const float mu_ij = fac_mu * r_inv * omega_ij; /* This is 0 or negative */
+
+ /* Signal velocity */
+ const float v_sig = ci + cj - 3.f * mu_ij;
+
+ /* Now construct the full viscosity term */
+ const float rho_ij = 0.5f * (rhoi + rhoj);
+ const float visc = -0.25f * const_viscosity_alpha * v_sig * mu_ij *
+ (balsara_i + balsara_j) / rho_ij;
/* Now, convolve with the kernel */
const float visc_term = 0.5f * visc * (wi_dr + wj_dr) * r_inv;
@@ -255,23 +235,6 @@ __attribute__((always_inline)) INLINE static void runner_iact_force(
/* Eventually got the acceleration */
const float acc = visc_term + sph_term;
- /* //if(pi->id == 1000 && pj->id == 1100) */
- /* if(pi->id == 515050 && pj->id == 504849) */
- /* message("Interacting with %lld. r=%e hi=%e hj=%e dWi/dx=%e dWj/dx=%3e
- * dvdr=%e visc=%e sph=%e", */
- /* pj->id, */
- /* r, */
- /* 2*hi, */
- /* 2*hj, */
- /* wi_dr, */
- /* wj_dr, */
- /* dvdr, */
- /* visc_term, */
- /* sph_term */
- /* ); */
- /* if(pi->id == 1100 && pj->id == 1000) */
- /* message("oO"); */
-
/* Use the force Luke ! */
pi->a_hydro[0] -= mj * acc * dx[0];
pi->a_hydro[1] -= mj * acc * dx[1];
@@ -337,28 +300,31 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_force(
/* Compute sound speeds */
const float ci = pi->force.soundspeed;
const float cj = pj->force.soundspeed;
- float v_sig = ci + cj;
/* Compute dv dot r. */
const float dvdr = (pi->v[0] - pj->v[0]) * dx[0] +
(pi->v[1] - pj->v[1]) * dx[1] +
(pi->v[2] - pj->v[2]) * dx[2];
- /* Artificial viscosity term */
- float visc = 0.f;
- if (dvdr < 0.f) {
- const float mu_ij = fac_mu * dvdr * r_inv;
- v_sig -= 3.f * mu_ij;
- const float rho_ij = 0.5f * (rhoi + rhoj);
- const float balsara_i =
- fabsf(pi->div_v) /
- (fabsf(pi->div_v) + pi->force.curl_v + 0.0001 * ci / fac_mu / hi);
- const float balsara_j =
- fabsf(pj->div_v) /
- (fabsf(pj->div_v) + pj->force.curl_v + 0.0001 * cj / fac_mu / hj);
- visc = -0.25f * const_viscosity_alpha * v_sig * mu_ij / rho_ij *
- (balsara_i + balsara_j);
- }
+ /* Balsara term */
+ const float balsara_i =
+ fabsf(pi->div_v) /
+ (fabsf(pi->div_v) + pi->force.curl_v + 0.0001 * ci / fac_mu / hi);
+ const float balsara_j =
+ fabsf(pj->div_v) /
+ (fabsf(pj->div_v) + pj->force.curl_v + 0.0001 * cj / fac_mu / hj);
+
+ /* Are the particles moving towards each others ? */
+ const float omega_ij = fminf(dvdr, 0.f);
+ const float mu_ij = fac_mu * r_inv * omega_ij; /* This is 0 or negative */
+
+ /* Signal velocity */
+ const float v_sig = ci + cj - 3.f * mu_ij;
+
+ /* Now construct the full viscosity term */
+ const float rho_ij = 0.5f * (rhoi + rhoj);
+ const float visc = -0.25f * const_viscosity_alpha * v_sig * mu_ij *
+ (balsara_i + balsara_j) / rho_ij;
/* Now, convolve with the kernel */
const float visc_term = 0.5f * visc * (wi_dr + wj_dr) * r_inv;