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The surface configuration and internal structure of artificial hailstones

1968; Wiley; Volume: 94; Issue: 399 Linguagem: Inglês

10.1002/qj.49709439902

1477-870X

I. H. Bailey, W. C. Macklin,

Fluid Dynamics and Heat Transfer

Abstract An experimental study has been made of the external and internal structure of artificial hailstones grown freely supported in a vertical wind tunnel. In addition the nature of ice deposits formed on fixed stationary objects and objects rotating about a horizontal axis has been investigated at airspeeds of 35 to 40 m s −1 . Lobe‐like growth similar to that found in natural hailstones has been reproduced. The lobes are most pronounced when the accreted droplets are small and when growth takes place near the wet limit. With large droplets and when the growth is very spongy the surface irregularities are far less marked. It is inferred that the lobe‐like growth is due to a collection efficiency effect. The drag coefficients of a number of artificial hailstones have been measured. None of the values is greater than 0·66. Some of the moderate sized stones (4 to 6 cm diameter) entered the critical flow regime where their drag coefficients were considerably reduced. This did not occur, however, for large (10 cm diameter) very irregular hailstones.