Asymmetry of nozzle's throat produces oscillatory type net side-force axial profile. Using mean values of localized static pressure and Mach number, scaling laws for flat-plate supersonic flow over protrusion are applied to nozzle expansion cone irregularities to give approximate indication of perturbed-pressure profiles and induced side forces

Dowdy, M. W.

Strand, L. D.

English

NASA Technical Reports Server

Re 
Lir
September 170	 Brief 70-10406 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech B rief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Experimental Investigation and Analysis of Two Sources

of Nozzle-Thrust Misalignment 
Expansion	 Dimensions are in inches 
Joint
Test Assembly 
Irregularities in a nozzle's surface and asymmetry 
of the throat can produce measurable and possibly 
significant side forces. An investigation is reported 
(see Note 2) of the possible effects of nozzle-surface 
irregularities and throat asymmetry on the position 
of the nozzle's thrust vector. Such irregularities and 
asymmetry can result from delamination or erosion of 
a nozzle's ablative materials during firing of a rocket. 
The objects of the investigation were: (1) to determine 
whether (and if so to what extent) an exaggerated 
asymmetry in the nozzle throat's cross section dis-
places the thrust vector; and (2) to extend flat-plate 
protrusion data to nozzle flow to determine to what 
extent a protrusion to the flow, in the nozzle's expan-
sion region, displaces the thrust vector.
Experiments were conducted in a three-dimensional 
gas-flow test facility (see fig.). The flow channel was 
a gas line tapping a 21-in, hypersonic wind tunnel 
downstream from the heated-air supply and upstream 
from the inlet valve to the test section. In air-supply 
potential the auxiliary flow channel essentially equaled 
the wind tunnel: maximum supply pressure, about 
660 psia; maximum rate of air flow, 10 lb/sec. The 
temperature of the supply could be controlled be-
tween 90° and 1350°F. 
For both nozzles all pressure data expressed as 
ratios relative to the plenum supply pressure were 
essentially independent of test-supply pressure. For 
both, the net side force, summed over the nozzle's 
expansion ratio, reached a maximum and then con-
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19700000392 2020-03-17T00:47:41+00:00Z
tinued to decrease as the nozzle was traversed along 
its axis, leveling-off at a minimum overall value for 
the asymmetric-nozzle case. 
The characteristics of the perturbed-unperturbed 
pressure-ratio profile approached those of pressure-
ratio profiles found earlier for flat-plate, turbulent-
boundary-layer flow over two-dimensional protru-
sions; the differences were probably due to the three-
dimensional nature of the experimental protrusion. 
The asymmetric nozzle's net side-force profile 
maximum proved to be not solely attributable to the 
particular geometry of the test nozzle. A highly simpli-
fied three-dimensional flow-field analysis gave reason-
ably good parity with the asymmetric-nozzle experi-
mental data. 
It is believed that a two-dimensional asymmetric-
nozzle parametric analysis predicts the correct trend 
of change in magnitude of induced nozzle side force 
with a decreasing degree of throat asymmetry. Asym-
metry in the region of the nozzle's throat produces 
an oscillatory type of net side-force axial profile. By 
use of mean values of the localized static pressure and 
Mach number, scaling laws for flat-plate supersonic 
flow over a protrusion can be applied to irregularities 
in the nozzle expansion cone for an approximate in-
dication of the perturbed-pressure profiles and there-
fore the induced side forces. 
For a first estimate of the induced side force, a 
rough surface-pressure integration should be carried
out with use of axial-pressure profiles obtained by a 
two-dimension flow analysis in the plane of the desired 
side-force direction. 
Note: 
The following documentation may be obtained from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-CR-105905 (N69-37609), Cold-
Flow Experimental Investigation and 
Analysis of Two Sources of Nozzle 
Thrust Misalignment 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: L. D. Strand and M. W. Dowdy of 
Caltech /J PL
under contract to 
NASA Pasadena Office 
(NPO-1 1355) 
Brief 70-10406	 Category 06


Experimental investigation and analysis of two sources of nozzle-thrust misalignment

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server