1989 Volume 51 Issue 3 Pages 57-64
The maximum velocity of air stream in a straight tube exists at the cross-sectional center of the tube. A boom type blow head, however, has outlets at regular intervals on the bottom line of the tube. Accordingly, the maximum velocity Vmax is not at the cross-sectional center and is slightly biased toward the bottom line on which the outlets are.
The authors showed experimental formula of velocity distribution to calculate mean velocity V and flux Q from the data of dynamic pressure Pd at the cross-sectional center. The velocity u of an arbitrary point on the central vertical line in the cross-section were expressed as a function of distance between the point and the bottom line as follows;
u/Vc×100(%)=αyε(1-y)ι
where:
Vc=the velocity at the cross-sectional center
y=distance from the bottom line
ε, ι=index number which express the inclination of curvature of velocity distribution
Because the horizontal distribution of the velocity is thought to be symmetry, index ε′ should be equal to ι′. And y is distance from the inner side surface. In a boom type blow head, the central velocity Vc is not equal to the maximum velocity Vmax. And the pipe factor F of the heads was found to be 0.87 in practical conditions.
