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Show ( 24') H' = h'f 1 + ( 2 v ' v2)/ g Y h' 11/ 3 L • ' » • m a x J The numerical illustration given above would lead to a damming height of about 12 meters. D. Thrust Effect of Avalanches Referring to Equations ( 17), ( 21), and ( 22), the specific thrust pressure near the underlying surface ( Boden) may be written: ( 25) p= Y ( h' + v2/ 2g) = Y H = Y H' r • m 3 ' m ' max where Y m = C Y +( Y / 2) ( 1 + y / Y F> P/ P0 ]/[ l + < Y / YF ) < P / P 0 > ] ^ m a x = ( Y + Y F p/ p0)/ U + p/ p0) H' = maximum damming height From a combination of the equations it follows that: ( 25*) p - Y F [ ( ( q/ 2> 2 + HpQ/ y F ) X / 2 - q/ 2 ] in which q = p0/ Y -( H/ 2) ( 1 + Y / Y F} The uppermost boundary value for p is the specific thrust pressure from the equation of momentum: ( 25") pm a x = Y _( h' + v2/ g) This maximum pressure can occur, however, only if the snow is plastered onto the obstacle by inelastic impact and remains there without damming up or flowing laterally. However, inasmuch as snow flows like a fluid which is dammed up on impact and flows off laterally, Equation ( 25) is valid. Occasionally Equation ( 25' f) also is quoted erroneously in the literature for this situation, because the momentum equation was not applied to a complete control surface, i. e., the pressure distribution was not taken into consideration beyond the cross section of the impinging stream. Separation of snow from the aerosol can only occur in the following cases : a) By sedimentation if the velocity of the aerosol falls below about 6/ 5 of the velocity of fall of the particles in air. b) If the aerosol is so lightly loaded with solid particles, i. e., if the snow is so thoroughly disintegrated that, with a sudden drop in velocity of the air, A v, ( for example as a result of obstruction), no adjacent 41 |