STABLE AND ACCURATE BOUNDARY TREATMENTS FOR COMPACT, HIGH-ORDER FINITE-DIFFERENCE SCHEMES

The stability characteristics of various compact fourth- and sixth-order spatial operators are used to assess the theory of Gustafsson, Kreiss and Sundstrom (G-K-S) for the semidiscrete initial boundary value problem (IBVP). In all cases, favorable comparisons are obtained between G-K-S theory, eigenvalue determination, and numerical simulation. The conventional definition of stability then is sharpened to include only those spatial discretizations that are asymptotically stable (bounded, left half-plane (LHP) eigenvalues). It is shown that many of the higher-order schemes that are G-K-S stable are not asymptotically stable. A series of compact fourth- and sixth-order schemes is developed, all of which are asymptotically and G-K-S stable for the scalar case. A systematic technique is then presented for constructing stable and accurate boundary closures of various orders. The technique uses the semidiscrete summation-by-parts energy norm to guarantee asymptotic and G-K-S stability of the resulting boundary closure. Various fourth-order explicit and implicit discretizations are presented, all of which satisfy the summation-by-parts energy norm.