The following is a general procedure for obtaining the delay time. If 

 (t_^)^ <_ (""^ J.) 3^+]^ > substitute D for s, select the equation having the correct 



limits from equations 13a, b, or c, and solve for t. If (t^)^ > (''^Pj^ + ^j proceed 

 in the same manner using equation 14a or b. 



APPENDIX n: CELL BURNING FRACTION 



The fraction of a cell that is burning at time 9 since its ignition is evalu- 

 ated from the distance equations for s in appendix 1. Initially the front of the 

 burning zone spreads into the cell as described by s with t = 6. The rear of the 



burning zone follows in the same manner but with t = 6 - t , where t is the 

 to r r 



residence time in the cell. During passage of the fire, the front and the rear of 

 the burning zone may exist in the cell together, separately, or be absent. The 

 following equations account for all cases: 



F = 



F = s(e)/D 



F = (s(e)-s(e-Tp)/D 



F = 1 



F = l-sCe-T^/D 



F = 

 where 



F 

 D 

 D' 

 t , 



for e<o 



for D' <D and 0<e<T 



— — r 



or for D'>D and OO^t , 

 « d 



for D'<D and t <e<t , 



— r — d 



for D'>D and t ,<e<T 

 d — r 



for D'<D and t ,<e<t,+T 

 — d — d r 



or for D'>D and x <e<t,+T 

 r — d r 



for e>t ,+T 

 d r 



fraction of the cell that is burning at time 

 cell size 



transition distance 



delay time 



cell residence time 



The cell has not been 

 ignited. 



The fire front is in the 

 cell. There is no 

 burned out area. 



Both the fire front and 

 rear are in the cell. 



The entire cell is 

 burning . 



The fire front has passed 



the cell. 

 There is a burned out area. 



The cell is burned out. 



s [6) = distance the front of the burning zone has spread at time t = 6 according 

 to equation 9 or 10 



sCe-T 3 

 r 



distance the rear of the burning zone has spread at time t 

 according to equation 9 or 10. 



3-T 



28 



