Simulation of turbomachinery flows

With the interest in jet propulsion at the end of World War II, aerodynamicists were challenged to develop mathematical models which could be used to design turbomachinery components for jets. NASA Lewis engineers and scientists played a major role in meeting this challenge. Some of their accomplishments are highlighted as well as those of others. Several problems are addressed which must be solved if jet propulsion technology is to advance

Pest Status of the Fall Armyworm, Spodoptera Frugiperda (J. E. Smith), on Conventional and Transgenic Cotton Expressing the Bacillus Thuringiensis CryIA (C) Delta-Endotoxin: Development, Survival, and Host-Strain Influence.

The pest status of the fall armyworm, Spodoptera frugiperda (J. E. Smith), including development and survival on conventional and transgenic Bacillus thuringiensis (Bt) cotton and host-strain influences, was examined in laboratory and field studies. Neonates (1st instars) were fed leaves from conventional (cv. DP 5415 and cv. DP 5690) and transgenic Bt (cv. NuCOTN 33\rm\sp{B} and cv. NuCOTN 35\rm\sp{B}) cotton. There were no significant differences $(P\u3e0.05)$ between cultivars in larval mortality and survival to the pupal and adult stages. However, times to pupation and adult eclosion were significantly longer $(P\u3c0.05)$ for larvae fed transgenic Bt cotton compared to conventional cotton. In addition, larvae weighed significantly less $(P\u3c0.05)$ when fed transgenic Bt cotton compared to conventional cotton. A study was conducted to determine when cotton bolls become tolerant to fall armyworm injury. Fifth instars were caged individually on bolls of various ages from conventional (cv. DP 5415) and transgenic Bt (cv. NuCOTN 33\rm\sp{B}) cotton to define the period of boll susceptibility to larval injury. For DP 5415 bolls, there was no significant linear relationship $(P\u3e0.05)$ describing larval mortality or successful boll penetration as a function of boll age. Larvae were able to successfully penetrate ($\u3e$60%) DP 5415 bolls throughout boll development. For NuCOTN 33\rm\sp{B} bolls, there was a significant linear relationship $(P\u3c0.05)$ describing larval mortality (increased as bolls developed) or successful boll penetration (decreased as bolls developed) as a function of boll age. Larvae were able to successfully penetrate ($\u3e$40%) NuCOTN 33\rm\sp{B} bolls at 350 heat-units. Studies were conducted to determine if there were differences in susceptibility between the two host-associated fall armyworm strains to conventional (cv. DP 5415 and cv. DP 5690) or transgenic Bt (cv. NuCOTN 33\rm\sp{B} and cv. NuCOTN 35\rm\sp{B}) cotton or to selected insecticides. Fall armyworms collected from various forage grasses were consistently more susceptible to conventional cotton, transgenic Bt cotton, and selected insecticides than larvae collected from field corn. The utility of the sodium channel para locus to distinguish fall armyworm host-associated strains also was addressed. Genetic differentiation in the para locus was not correlated with host-associated strains. However, results suggest that this molecular marker is useful for distinguishing closely related Spodoptera spp

Average-passage simulation of counter-rotating propfan propulsion systems as applied to cruise missiles

Counter-rotating propfan (CRP) propulsion technologies are currently being evaluated as cruise missile propulsion systems. The aerodynamic integration concerns associated with this application are being addressed through the computational modeling of the missile body-propfan flowfield interactions. The work described in this paper consists of a detailed analysis of the aerodynamic interactions between the control surfaces and the propfan blades through the solution of the average-passage equation system. Two baseline configurations were studied, the control fins mounted forward of the counter-rotating propeller and the control fins mounted aft of the counter-rotating propeller. In both cases, control fin-propfan separation distance and control fin deflection angle were varied

Simulation of turbomachinery flows

Significant advancements have been made in the last five years in the ability to model turbomachinery flows of engineering interest. This advancement can be directly attributed to the second generation of supercomputers like the Cray XMP and Cray 2 and advanced instrumentation techniques. Early on, the National Aeronautics and Space Administration Lewis Research Center recognized the potential gains in turbomachinery performance and life that could be achieved by taking advantage of this technology and instituted a comprehensive research program in turbomachinery flow modeling. This activity combined the areas of fluid flow analysis, computational fluid dynamics, and experimental fluid mechanics. As a result of this activity, Lewis has become an internationally recognized leader in turbomachinery flow modeling. Many of the research activities conducted under this program are utilized by industry. The presentation gives an overview of this program and provides sample illustration of simulation performed to date

Differential Cross Sections for Electromagnetic Dissociation

Differential cross; sections for electromagnetic dissociation in nucleus-nucleus collisions are calculated. The kinetic energy distributions is parameterized with a Boltzmann distribution and the angular distribution is assumed isotropic in the projectile frame. In order to be useful for three-dimensional transport codes, these cross sections are available in both the projectile and lab frames. Comparison between theory and experiment is good. The formalism applies to single and multiple nucleon removal, a particle removal, and fission in electromagnetic reactions of nuclei. (c) 2006 Elsevier B.V. All rights reserved

Simulation of 3-D viscous flow within a multi-stage turbine

This work outlines a procedure for simulating the flow field within multistage turbomachinery which includes the effects of unsteadiness, compressibility, and viscosity. The associated modeling equations are the average passage equation system which governs the time-averaged flow field within a typical passage of a blade row embedded within a multistage configuration. The results from a simulation of a low aspect ratio stage and a one-half turbine will be presented and compared with experimental measurements. It will be shown that the secondary flow field generated by the rotor causes the aerodynamic performance of the downstream vane to be significantly different from that of an isolated blade row

Average-passage flow model development

A 3-D model was developed for simulating multistage turbomachinery flows using supercomputers. This average passage flow model described the time averaged flow field within a typical passage of a bladed wheel within a multistage configuration. To date, a number of inviscid simulations were executed to assess the resolution capabilities of the model. Recently, the viscous terms associated with the average passage model were incorporated into the inviscid computer code along with an algebraic turbulence model. A simulation of a stage-and-one-half, low speed turbine was executed. The results of this simulation, including a comparison with experimental data, is discussed

Electromagnetic Dissociation Cross Sections using Weisskopf-Ewing Theory

It is important that accurate estimates of crew exposure to radiation are obtained for future long-term space missions. Presently, several space radiation transport codes exist to predict the radiation environment, all of which take as input particle interaction cross sections that describe the nuclear interactions between the particles and the shielding material. The space radiation transport code HZETRN uses the nuclear fragmentation model NUCFRG2 to calculate Electromagnetic Dissociation (EMD) cross sections. Currently, NUCFRG2 employs energy independent branching ratios to calculate these cross sections. Using Weisskopf-Ewing (WE) theory to calculate branching ratios, however, is more advantageous than the method currently employed in NUCFRG2. The WE theory can calculate not only neutron and proton emission, as in the energy independent branching ratio formalism used in NUCFRG2, but also deuteron, triton, helion, and alpha particle emission. These particles can contribute significantly to total exposure estimates. In this work, photonuclear cross sections are calculated using WE theory and the energy independent branching ratios used in NUCFRG2 and then compared to experimental data. It is found that the WE theory gives comparable, but mainly better agreement with data than the energy independent branching ratio. Furthermore, EMD cross sections for single neutron, proton, and alpha particle removal are calculated using WE theory and an energy independent branching ratio used in NUCFRG2 and compared to experimental data