diff --git a/src/oneD/StFlow.cpp b/src/oneD/StFlow.cpp
index aafaed5a0..02fb636ca 100644
--- a/src/oneD/StFlow.cpp
+++ b/src/oneD/StFlow.cpp
@@ -1054,24 +1054,23 @@ void StFlow::evalContinuity(size_t j, double* x, double* rsd, int* diag, double
             -(rho_u(x,j+1) - rho_u(x,j))/m_dz[j]
             -(density(j+1)*V(x,j+1) + density(j)*V(x,j));
     } else if (m_isFree) {
+        // terms involving V are zero as V=0 by definition
         if (grid(j) > m_zfixed) {
             rsd[index(c_offset_U,j)] =
-                - (rho_u(x,j) - rho_u(x,j-1))/m_dz[j-1]
-                - (density(j-1)*V(x,j-1) + density(j)*V(x,j));
+                - (rho_u(x,j) - rho_u(x,j-1))/m_dz[j-1];
         } else if (grid(j) == m_zfixed) {
             if (m_do_energy[j]) {
                 rsd[index(c_offset_U,j)] = (T(x,j) - m_tfixed);
             } else {
                 rsd[index(c_offset_U,j)] = (rho_u(x,j)
-                                            - m_rho[0]*0.3);
+                                            - m_rho[0]*0.3); // why 0.3?
             }
         } else if (grid(j) < m_zfixed) {
             rsd[index(c_offset_U,j)] =
-                - (rho_u(x,j+1) - rho_u(x,j))/m_dz[j]
-                - (density(j+1)*V(x,j+1) + density(j)*V(x,j));
+                - (rho_u(x,j+1) - rho_u(x,j))/m_dz[j];
         }
     } else {
-        // unstrained
+        // unstrained with fixed mass flow rate
         rsd[index(c_offset_U, j)] = rho_u(x, j) - rho_u(x, j - 1);
     }
 }