1. Scientist, Nortek, 27 Drydock Ave., Boston, MA 02210; formerly, DeFrees Hydraulics Laboratory, School of Civil and Environmental Engineering, Cornell Univ., 220 Hollister Hall, Ithaca, NY 14853 (corresponding author).
2. Professor, DeFrees Hydraulics Laboratory, School of Civil and Environmental Engineering, Cornell Univ., 220 Hollister Hall, Ithaca, NY 14853.