Performance on manycore devices is dependent data access patterns where different devices (NVIDIA, Intel-Phi, NUMA) require different data access patterns. A performance-portable programming model does not force a false-choice between arrays-of-structures or structures-of-arrays, instead it defines abstractions to transparently adapt data structures to meet device requirements. The KokkosArray library implements this strategy through simple and intuitive multidimensional array abstractions. Usability and performance-portability is demonstrated with proxy-applications for finite element and molecular dynamics codes. MiniMD, a proxy-application for the LAMMPS molecular dynamic code, has implementations in OpenMP, OpenCL, CUDA, and now KokkosArray. A comparison of miniMD''s KokkosArray implementation with the previous three versions demonstrate the relative strengths and weaknesses of KokkosArray, and that how the portable version retains about 95% of the performance of the "native" versions. Multiphysics applications with heterogeneous finite element discretizations have complex and highly irregular data structures. A KokkosArray-based prototype unstructured heterogeneous finite element mesh library and its support for heterogeneous manycore parallel computations will be presented.