228 



BELL SYSTEM TECHNICAL JOURNAL 



The comparable empirical equation for the accelerated method of 

 test is 



lOF 



where 



Vm = 



Y = 



1 - 0.692 F' 



jT^O. 05^0.2 



(6) 



and 



Vm = Accelerated method threshold velocity. 



The other terms are the same as given above. This equation has a 

 degree of accuracy comparable to equation (5). 



These two equations, (5) and (6), were combined to form equation 

 (7) which was used to determine expected natural wind threshold 

 velocities from the accelerated method results. 



= T' 



2.24L"-i«5''-''3 



^0.3 



1 



0.6Q2 



^^n. 05 en. 2 



(7) 



The terms in this equation are the same as those given above. 



