Convective term in heat equation for solid region in conjugateHeatFoam- Foam Extend
 

I tried to modify the solver by adding the convective part but it is giving:

Segmentation fault (core dumped)

I tried:

fvScalarMatrix* TSolidEqn = new fvScalarMatrix
(
(rhoCpsolid)*
(
fvm::ddt(Tsolid)
+ fvm::div(phis, Tsolid) //modification
)
- fvm::laplacian(ksolidf, Tsolid, "laplacian(k,T)")
+ fvm::SuSp(-solidThermo.S()/Tsolid, Tsolid)
);

where phis is surfaceScalarField and is defined as: linearInterpolate(U) & solidMesh.Sf()


Can anyone help me in this regard? How can I fix this issue?