A Novel Stencil Selection Method for the Gradient Reconstruction on Unstructured Grid based on OpenFOAM

•A novel stencil selection method for the gradient reconstruction is presented.•An advancing front technique is used for boundary information.•The new method is robust for various kinds of unstructured meshes.•The convergence speed is improved to be 1.64 ∼ 2.60x faster than that of extLSQR.•A competitive order of accuracy can be achieved by less stencil cells.