A Wind-Tunnel Investigation of Bomb Release at a Mach Number of 1.62 Page: 4 of 30
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NACA RM L53L29
3
SIMILARITY RELATION
For most dynamic testing, near-complete simulation of prototype
conditions is desirable. This becomes difficult in the cases where the
tests are to be made in moderately small wind tunnels where models are
limited in size, especially for supersonic testing where the prototype
Mach number must be duplicated and, consequently, in many cases, the
prototype velocity is approximated (see ref. 3). Therefore, for the
present tests, simulation was limited to the ratio of bomb mass and
dynamic pressure so that
Drag Drag
(Gravity forced (Gravity forced
model (prototype
This means that the path of the model center of gravity essentially
duplicated the path of the prototype center of gravity for the releases
where the bomb attitude was near-level, that is, where the upsetting
lifts and moments were small.
This relation of drag to gravity can be put in the form,
model 3 'prototype
and, by assuming CDmodel = CDprototype (this assumption will be dis-
cussed later), then,
Model = prototypee
For the present test the prototype was assumed to be a 5,000-pound
Douglas Aircraft Co., Inc., store which established Wprototype and
Zprototype' By assuming various altitudes, prototype was established
for this constant Mach number of 1.62. With regard to the model, the
tunnel dimensions established model. In order to fulfill the similar-
ity relation, the ratio (i) had to be small; so the tunnel was
S1model
operated at low stagnation pressures (thereby resulting in low tunnel
dynamic pressures) and the models were constructed of lead. Variations
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Rainey, Robert W. A Wind-Tunnel Investigation of Bomb Release at a Mach Number of 1.62, report, March 19, 1954; (https://digital.library.unt.edu/ark:/67531/metadc60060/m1/4/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.