The current work presents the incorporation of the Lower-Order Refined (LOR) preconditioner within the incompressible Navier-Stokes equations solver of the open-source spectral/hp element
method framework Nektar++. This preconditioner is constructed on a low-order (P=1) finite element
discretisation spectrally equivalent to a given high-order discretisation. The LOR preconditioner provides advantages like low cost operator evaluations, constant memory requirement per degree of freedom,
minimal sensitivity to high aspect-ratio elements and controlled iterative condition number with increasing problem size. The contribution extends to developing a functional LOR preconditioner tailored for
mixed-element 3D mesh configurations, encompassing both prismatic and tetrahedral elements, allowing
usage for complex geometries requiring unstructured 3D meshes with boundary layers. Notably, the
Nektar++ implementation is the first instance of using the LOR preconditioner with a modal expansion
basis function. This study presents the iterative performance and scaling of the proposed preconditioner
to solve the pressure Poisson system arising from the incompressible Navier-Stokes equations solver for
industrial test cases relevant to the context of race-car aerodynamics.