-5- 625 



NOTES Off THE APPLICATION OF THE REVISED DOME ANALYSIS METHOD 

 The staf^es of the method are :- 



1. Determine tne accrcximate Oeoth, a , by the original oome analysis methoO. 



''0 



2. Calculate th; initial aome v^-l-ocity at trii centre v^^ ft. /second. 



3. °lot th? calculated dsoth on the Dasis of dome radius (as in Figure 2 in this report) 

 and determine the dome- factor n. This is the mecn value of the decth gradient Between a 

 radius equal to i 3 and 3/2 3 , exoresse:; as ^. oercentage. 







4. Note the time t. frotr. detonation to the first aocearance of the olume and the height, h, 

 of the dome, at the same instant. 



h. d 



From this calculate V = 2 



^c 



5. Evaluate the correction factor /x where 



^J. = 0.50 + 0.78 V/v + C.012 n - 0.00012 n^. 



6. Otjtain thi' corrected decth o i-.s 



Notes which may be heli>ful at the di ff event stapes are eiven below , 



1. It is fcuno Best to work with dome measurements taken at the centre and aooroximately 

 Detwsen radii equal to i d and 3/2 d on either side of the centre. Measurements at four or 

 five radii are sufficient, ° For OomOs ^ which detonate after only a short time delay (say one 

 second or less) the cavity formed ^-.t entry will still Dc open. In these circumstances It has 

 been found satisfactory to base the oeoth calculation en Joms measurements taken only en the 

 side away from the cavity. The other siJs :f the ocme tencJs t: oe distorted by the cavity and 

 is r.bscurec oy the solash from the imcact :f the b.-mb. 



2. In obtaining the initial velocity, v , from tne dome height it is important to use the 

 time from tns first aocearance of tne soray. This may oe between two frames of the cine film 

 but the exact instant can usually be decided ay slotting the curve of oome height for successive 

 frames ano noting where it cuts the axis. 



3. In generril this method of obtaining n will oe found to give a fair measure of the mean 

 depth gradient, |f there. should be dny suooen distortion in the deotn calculated close tc the 

 measuring points this mciy be disregar;sc an: th^ mean grai^ient taken through the reneining ocints. 

 In the present analysis this was only found necessary in one exanole, 



4. txcerience in the analysis has shown that it is the aooearance of the main plume that must 

 be looked for In determining t ano that the fine soouts which sometimes precede the plume can bo 

 disregarded, 



