24,212 research outputs found
Ignition Transients of Large Segmented Solid Rocket Boosters
A model is described which provides a means for analyzing the complexities of ignition transients and pressure peaks of large, high performance, segmented solid rocket boosters. The method accounts for: (1) temporal and spatial development of the flow field set up by the head end igniter discharge, (2) ignition and flame spreading coupled to chamber flow, (3) the steep velocity, pressure, and temperature gradients that occur during the early phases of ignition, and (4) the interactions that produce ignition spikes (i.e., compression of chamber gases during pressurization, erosive burning, and mass added effect of igniter discharge). The technique differs from earlier models in that the flow interactions between the slots and main chamber are accounted for, and the original computer program for monolithic motors is improved. The procedures were used to predict the ignition transients of the current design for the space shuttle booster
Observations of breakup processes of liquid jets using real-time X-ray radiography
To unravel the liquid-jet breakup process in the nondilute region, a newly developed system of real-time X-ray radiography, an advanced digital image processor, and a high-speed video camera were used. Based upon recorded X-ray images, the inner structure of a liquid jet during breakup was observed. The jet divergence angle, jet breakup length, and fraction distributions along the axial and transverse directions of the liquid jets were determined in the near-injector region. Both wall- and free-jet tests were conducted to study the effect of wall friction on the jet breakup process
Modeling of combustion processes of stick propellants via combined Eulerian-Lagrangian approach
This research is motivated by the improved ballistic performance of large-caliber guns using stick propellant charges. A comprehensive theoretical model for predicting the flame spreading, combustion, and grain deformation phenomena of long, unslotted stick propellants is presented. The formulation is based upon a combined Eulerian-Lagrangian approach to simulate special characteristics of the two phase combustion process in a cartridge loaded with a bundle of sticks. The model considers five separate regions consisting of the internal perforation, the solid phase, the external interstitial gas phase, and two lumped parameter regions at either end of the stick bundle. For the external gas phase region, a set of transient one-dimensional fluid-dynamic equations using the Eulerian approach is obtained; governing equations for the stick propellants are formulated using the Lagrangian approach. The motion of a representative stick is derived by considering the forces acting on the entire propellant stick. The instantaneous temperature and stress fields in the stick propellant are modeled by considering the transient axisymmetric heat conduction equation and dynamic structural analysis
Flavor Mixing and the Permutation Symmetry among Generations
In the standard model, the permutation symmetry among the three generations
of fundamental fermions is usually regarded to be broken by the Higgs
couplings. It is found that the symmetry is restored if we include the mass
matrix parameters as physical variables which transform appropriately under the
symmetry operation. Known relations between these variables, such as the
renormalization group equations, as well as formulas for neutrino oscillations
(in vacuum and in matter), are shown to be covariant tensor equations under the
permutation symmetry group.Comment: 12 page
Inclusion of Z->b b-bar vertex corrections in Precision Electroweak Tests on the Sp(6)_L X U(1)_Y Model
We extend our previous work on the precision electroweak tests in the Sp(6)_L
X U(1)_Y family model to include for the first time the important Z->b b-bar
vertex corrections encoded in a new variable epsilon_b, utilizing all the
latest LEP data. We include in our analysis the one loop EW radiative
corrections due to the new bosons in terms of epsilon_1, epsilon_b and
. We find that the correlation between epsilon_1 and epsilon_b
makes the combined constraint much stronger than the individual ones. The model
is consistent with the recent CDF result of m_t=174\pm 10^{+13}_{-12}\GeV,
but it can not accomodate m_t\gsim 195\GeV.Comment: Latex, 16 pages+4 figures(not included but available as uuencoded or
PS files from [email protected]), PURD-TH-94-08, SNUTP-94-4
Rephasing invariance and neutrino mixing
A rephasing invariant parametrization is introduced for three flavor neutrino
mixing. For neutrino propagation in matter, these parameters are shown to obey
evolution equations as functions of the induced neutrino mass. These equations
are found to preserve (approximately) some characteristic features of the
mixing matrix, resulting in solutions which exhibit striking patterns as the
induced mass varies. The approximate solutions are compared to numerical
integrations and found to be quite accurate.Comment: 18 pages, 6 figure
- …