OCR Text |
Show accentuates surface irregularities is not possible above e. = 4.58 torr). Fig. 7b illustrates conditions for a medium humidity at e, = 2.29 torr (= CSE^ X while Fig. 7c for e, = 0.29 torr corresponds to very dry air. In calculating the individual curves 1 to 9, nT was chosen to give typical combinations for - M( ( X.) . Curve No. 1 (/# L= - 0.90 ( a), - 9.20 ( b), - 33.00 ( c) ° C). Here the air is saturated in respect' to water and in all cases - M decreases with increasing ( X',. - M changes much more slowly after than before the inflection point which represents the change- over from a melting to a non- melting surface, but then again decreases more rapidly so that eventually - M< 0, representing deposition of ice on the surface. This indicates the formation of rime, which G. Hofmann C3] has discussed in detail together with dew and hoarfrost formation. Because the increase in M is larger, the larger is CC. ( and thus, the smaller the radius of curvature of a ridge), very sharp ice feathers form facing into the wind. This rime formation is possible when the air is supersaturated in respect, to ice. It does not occur with Curve No. 2 (/$ = - 0.80 ( a), - 815 ( b), - 30.00 ( c) ° C) . In this case the air is saturated in respect to ice. For a melting surface, Curve No. 2 does not differ greatly from Curve No. 1. Beyond the inflection point - M still decreases slightly and, at large values of CC. , becomes slightly less than zero and independent of OC. . Fig. 7. Ablation - M as a function of the heat transfer coefficient CC, for p = 525 torr and Q+ B = meal cm- 2 min- 1 , as well as typical combinations of eL and / xr. . ( See text for further details.) The correct values for corresponding radii of curvature are entered at the top of Fig. 7a. 22 |