Page 12 - Combined_73_OCR

Ua = Velocity in tunnel without
model present

Using velocity ratios we can expand the term as follows:

(5)

or

(6)

where □ I! Velocity increase at tunnel wall due to model
blockage

Uq = Velocity increase at tunnel ceiling due to
model blockage

The terms (Ua/u^) and (ua/uq) are the velocity ratio terms presented by

Hensel whi (u^/Ua) and (uq/U^) are measured quantities. For bodies of

revolution, the velocity ratio terms are:

(ua/Utj) = • 56 (7)

(ua/u ii .29 (8)

It should be noted that the ground plane is assumed as a plane of sym­

metry in applying this method and this is reflected in equations 7 and

8.

Table II shows the relative agreement of the three methods dis­

cussed :

TABLE II - TOTAL BLOCKAGE FACTORS

Method Factor (Kt)

Pope 1.024
Herriot 1.054
Hensel (wall) 1.019
Hensel (ceiling) 1.020