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Unformatted text preview: 7.1. ISOTHERMAL, ISOCHORIC KINETICS 261 LBracket1 NO RBracket1 LBracket1 N RBracket1 10 Minus 11 10 Minus 9 10 Minus 7 10 Minus 5 0.001 0.1 10 t LParen1 s RParen1 10 Minus 12 10 Minus 10 10 Minus 8 10 Minus 6 LBracket1 N RBracket1 , LBracket1 NO RBracket1 LParen1 mole Slash1 cc RParen1 Figure 7.10: ρ NO and ρ N versus time for Zel’dovich mechanism at T = 1500 K , P = 6 . 23550 × 10 5 dyne/cm 2 . 18.104.22.168 Stiffness, time scales, and numerics One of the key challenges in computational chemistry is accurately predicting species concen- tration evolution with time. The problem is made difficult because of the common presence of physical phenomena which evolve on a widely disparate set of time scales. Systems which evolve on a wide range of scales are known as stiff, recognizing a motivating example in mass-spring-damper systems with stiff springs. Here we will examine the effect of tempera- ture and pressure on time scales and stiffness. We shall also look simplistically how different numerical approximation methods respond to stiffness.numerical approximation methods respond to stiffness....
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This note was uploaded on 11/26/2011 for the course EGN 3381 taught by Professor Park-sou during the Fall '11 term at FSU.
- Fall '11