shows the enlarged photograph near the apex cone of 70°.
The velocity vectors calculated by CFD simulations are also included in
the photograph. For the lower part of the apex cone, a small amount of
soap foam remained, but the soap foam is not detected on the upper
zone of the apex cone. From the flow vectors, the upper and lower
parts of the apex cone correspond to the upward and downward flow
regions, respectively. The critical line of the soap foam might be
considered to be the separation line of the upward and downward
flows. Fig. 9 shows the flow visualization photographs of soap foam
with various kinds of apex cones. Also included in each photograph
are the flow vectors calculated by CFD simulations. The area of soap