A STABLE SHIFTED-LEGENDRE PROJECTION SCHEME FOR GENERATING P-N BOUNDARY-CONDITIONS

A projection scheme for generating PN boundary conditions based on the shifted Legendre polynomials is discussed. The projection scheme yiel ds N+1 conditions for each boundary of a slab, just twice the number o f conditions required. The resulting overdetermined system of equation s is subsequently reduced to a square system by means of a standard le ast-squares technique. Tests carried out for several problems indicate that the procedure is numerically stable in high-order, in contrast t o the findings of some years ago when a similar projection scheme was first proposed.