Numerical analysis of flow and heat transfer in the VAFB LOX storage Dewar tank

The present report describes numerical simulation of three-dimensional transient distributions of velocity and temperature of liquid oxygen (LOX) in the LOX Dewar tank of Vendenberg Air Force Base (VAFB). The present analyses cover the replenish time period only. Four test cases have been considered. For all four cases, the input boundary conditions are comprised of LOX facility heat loads, drain flow rates, recirculation flow rates and dewar heating. All the quantities are prescribed as functions of time. The first two test cases considered sensitivity of results to the computational grid. In Case 3, system heat load was changed, while in Case 4, a lower LOX level was specified. Cases 1 and 2 showed that the temperatures were not sensitive to the grid refinement. This provided a basic check on the numerical model. Cases 3 and 4 showed that the thermal boundary layer motion near the tank surface becomes more significant at the late time, e.g., 5 1/2 hours from replenish start. Comparison between results of Cases 3 and 4 showed, as expected, that the smaller initial LOX volume given in Case 4, results in higher temperature level. All calculated velocity and temperature distributions were found to be plausible

Discrete element weld model, phase 2

A numerical method was developed for analyzing the tungsten inert gas (TIG) welding process. The phenomena being modeled include melting under the arc and the flow in the melt under the action of buoyancy, surface tension, and electromagnetic forces. The latter entails the calculation of the electric potential and the computation of electric current and magnetic field therefrom. Melting may occur at a single temperature or over a temperature range, and the electrical and thermal conductivities can be a function of temperature. Results of sample calculations are presented and discussed at length. A major research contribution has been the development of numerical methodology for the calculation of phase change problems in a fixed grid framework. The model has been implemented on CHAM's general purpose computer code PHOENICS. The inputs to the computer model include: geometric parameters, material properties, and weld process parameters

Rocket injector anomalies study. Volume 1: Description of the mathematical model and solution procedure

The capability of simulating three dimensional two phase reactive flows with combustion in the liquid fuelled rocket engines is demonstrated. This was accomplished by modifying an existing three dimensional computer program (REFLAN3D) with Eulerian Lagrangian approach to simulate two phase spray flow, evaporation and combustion. The modified code is referred as REFLAN3D-SPRAY. The mathematical formulation of the fluid flow, heat transfer, combustion and two phase flow interaction of the numerical solution procedure, boundary conditions and their treatment are described

Pitch-angle diffusion coefficients from resonant interactions with electrostatic electron cyclotron harmonic waves in planetary magnetospheres

Pitch-angle diffusion coefficients have been calculated for resonant interaction with electrostatic electron cyclotron harmonic (ECH) waves in the magnetospheres of Earth, Jupiter, Saturn, Uranus and Neptune. Calculations have been performed at two radial distances of each planet. It is found that observed wave electric field amplitudes in the magnetospheres of Earth and Jupiter are sufficient to put electrons on strong diffusion in the energy range of less than 100 eV. However, for Saturn, Uranus and Neptune, the observed ECH wave amplitude are insufficient to put electrons on strong diffusion at any radial distance

Source of the Bursty Bulk Flow Diffuse Aurora: Electrostatic Cyclotron Harmonic and Whistler Waves in the Coupling of Bursty Bulk Flows to Auroral Precipitation

Electron cyclotron harmonic (ECH) and whistler chorus waves are recognized as the two mechanisms responsible for the resonant waveparticle interactions necessary to precipitate plasma sheet electrons into the ionosphere, producing the diffuse Aurora. Previous work has demonstrated ECH waves dominate electron scattering at L shells >8, while whistler chorus dominates scattering at L shells L 1, consistent with electron betatron acceleration. Here, however, we nd whistler chorus emissions throughout an interval of fast ows where Te,/Te,||< 1. Parallel electron beams account for the enhanced parallel electron temperature and serve as the instability mechanism for the whistler chorus. The parallel electron beams and associated cigarshaped distributions are consistent with Fermi acceleration at dipolarizations in fast ows. We demonstrate that the scattering efciency of the whistler chorus exceeds that of ECH waves, which THEMIS also detects during the fast ows. The obliquity of the whistler waves permits efcient scattering of lowerenergy electrons into the diffuse aurora. We conclude that Fermi acceleration of electrons provides one important freeenergy source for the waveparticle interactions responsible for coupling plasma sheet electrons into the diffuse aurora during substorm conditions

Analysis of physical-chemical processes governing SSME internal fluid flows

The efforts to adapt CHAM's computational fluid dynamics code, PHOENICS, to the analysis of flow within the high pressure fuel turbopump (HPFTP) aft-platform seal cavity of the SSME are summarized. In particular, the special purpose PHOENICS satellite and ground station specifically formulated for this application are listed and described, and the preliminary results of the first part two-dimensional analyses are presented and discussed. Planned three-dimensional analyses are also briefly outlined. To further understand the mixing and combustion processes in the SSME fuelside preburners, a single oxygen-hydrogen jet element was investigated

Teaching a Minimally Structured Back-Progpagation Network to Recognise Speech Sounds

An associatve network was trained on a speech recognition task using continuous speech. The input speech was processed to produce a spectral representation incorporating some of the transformations introduced by the peripheral auditory system before the signal reaches the brain. Input nodes to the network represented a 150-millIsecond time window through which the transformed speech passed in 2-millisecond steps. Output nodes represented elemental speech sounds (demisyllables) whose target values were specified based on a human listener's ability to identify the sounds in the same input segment. The work reported here focuses on the experience and train on conditions needed to produce natural generalizations between training and test utterances

Trajectory Correction Flight Control System using Pulsejeton an Artillery Rocket

A trajectory correction flight control system is small and durable, and consists of a lateralpulsejet ring mounted on the rocket body. The pulsejet ring consists of a finite number of individualpulsejets. Each pulsejet on the ring imparts a single, short-duration, large force to the rocket inthe plane normal to the rocket axis of symmetry. Lateral pulsejets are used by flight controlsystem to assist the rocket to follow a pre-specified (command) trajectory. The trajectory-trackingflight control system computes the position error by comparing the measured position of therocket with the pre-specified trajectory. In actual application, the position of the rocket couldbe measured using in-house inertial measurement unit (IMU) or by ground-based-tracking radarsystem located at the firing site. A study has been undertaken to explore the feasibility of reducingthe impact point dispersion of a routinely-used artillery rocket using lateral pulsejets coupledto a trajectory correction flight control system. Simulation studies have been conducted to arriveat tuning parameters, namely the tracking error window size, the required elapsed time betweenthe pulsejet firings and the angle of tolerance between the tracking error and the individualpulsejet force. Further, the robustness of the methodology wrt measurement noise has also beenevaluated.Defence Science Journal, 2008, 58(1), pp.15-33, DOI:http://dx.doi.org/10.14429/dsj.58.162