Critical height

FIGURE 7.43 Critical height of an obstacle vs. distance from supply slot with a height hj (a) and supply nozzle with diameter do (b) Reproduced from Nielsen. ... 

Critical Height at which a Deftagration-to-Detonation Transition will Occur. Description of test The mat to be tested is loaded into a 2-inch diameter pipe capped at the lower end. 

Hc is the initial height corresponding to the critical height at which the constant settling rate gives way to a diminishing rate. 

If the bed is deeper than this critical height, slugging will take place for a gas velocity higher than the minimum velocity of slugging ... 

The critical heights where minimum 0/10 and at least 1/10 ignition occurs are recorded and reported. 

After many trials, the critical heights at which the sample response changes from "go" to "no go" or the reverse is determined. 

When these critical heights are found, tests should be done one step higher and one step lower. After that the fall height should be lowered when sample response is "go" and should be raised when it is "no go". Tests should be continued following this procedure. 

In total 20 tests, including 2 tests of the critical height, should be done. 

In [10] the no flowout condition is expressed in terms of the critical height H,r... 

Safe separation studies were conducted to achieve increased production and cost effectiveness with improved safety. A typical ammunition production line flow diagram (in this case for the manufacture of 105 mm projectile) consists of several work areas as shown in Fig 8. ( (l) Receiving and storage, (2) Box open and inspect (3) Melt Pour (U) Cool (5) Hold (6) Funnel Pull and (T) Riser Preparation.) Explosive material is transferred by automatic conveyor between these work areas. The requirement was to establish safe separation between explosive boxes, pallets with and without funnels, buckets, and to determine critical height of continuous feed flake Comp B and TNT. The objective of these tests was to establish minimum nonpropagation distances between these items so that an explosion chain reaction will be prevented. 

The effects evaluation will determine the likelihood of a transition to propagation and the consequences that can occur, critical height/depth and critical diameter tests will be performed to determine the detonability of a material in bulk or layer form (on a conveyor). Based on the transition results, a decision is made to complete one of the following effects evaluation tests such as a) firespread test which will include rate of flAme spread, heat of flux, and occurrence of fire brands and b) airblast tests including fragment tests. 

Obviously, it would be quite useful to know the precursors of such critical states, and be able to predict imminent catastrophes. It has been suggested recently (by Acharyya and Chakrabarti 1996a,6) that looking at the growth of the responses to the appropriate local and weak pulsed perturbations in some models, the approach to the self-organised critical state can be studied and its appearance can be predicted. This has been demonstrated, in particular, in the BTW critical height model (introduced in Section 1.2.3 of the first chapter, and also discussed in the previous section). It has been... 

Hydrocarbons accumulated along an inclined barrier rock - carrier rock interface, will start to migrate laterally updip through the carrier rock when the critical height of the hydrocarbon column is exceeded again by addition of hydrocarbons. 

The critical height of the hydrocarbon column under vertical groimdwater flow conditions becomes... 

From expression 4.22 follows that vertically upward directed groundwater flow will diminish the critical height z of the hydrocarbon column while vertically downward directed flow will increase its vertical height. 

To determine the critical height h of the string, we should write the liquid flow rate conservation condition the flow rate through the film cross-section is equal to the amount of liquid deposited from the gas flow on the string segment from our cross-section all the way to top. 

Repeating this reasoning for the subsequent rows, we can find the critical height for any row of strings ... 

Coulomb wedge theory of earth pressure, critical height of clay banks... 

Inner ring Critical height Fully inserted Critical height Extracted... 

Analyses on the foundations for Abutments A and B were also carried out. The lateral earth pressure on piles was calculated using stress distribution behind piles proposed by Tschebotarioff (1973) as shown in Figure 12.14. Since the spacing of piles was about three times the width of the pile, the group of piles and soil can be assumed to act as a unit. The ultimate lateral resistance, Ru was calculated using assumption of Poulos Davis (1980) that assumed 4 5 at the surface, increasing to a constant value of 9Su at three times the width of the pile. The critical height of... 

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