The design/analysis of flows through turbomachinery: A viscous/inviscid approach

The development of a design/analysis flow solver at NASA Lewis Research Center is discussed. The solver is axisymmetric and can be run inviscidly with assumed or calculated blockages, or with the viscous terms computed. The blade forces for each blade row are computed from blade-to-blade solutions, correlated data or force model, or from a full three dimensional solution. Codes currently under development can be separated into three distinct elements: the turbomachinery interactive grid generator energy distribution restart code (TIGGERC), the interactive blade element geometry generator (IBEGG), and the viscous/inviscid multi-blade-row average passage flow solver (VIADAC). Several experimental test cases were run to validate the VIADAC code. The tests, representative of typical axial turbomachinery duct axisymmetric wind tunnel body problems, were conducted on an SR7 Spinner axisymmetric body, a NASA Rotor 67 Fan test bed, and a transonic boatail body. The results show the computations to be in good agreement with test data

The role of shear in dissipative gravitational collapse

In this paper we investigate the physics of a radiating star undergoing dissipative collapse in the form of a radial heat flux. Our treatment clearly demonstrates how the presence of shear affects the collapse process; we are in a position to contrast the physical features of the collapsing sphere in the presence of shear with the shear-free case. By employing a causal heat transport equation of the Maxwell-Cattaneo form we show that the shear leads to an enhancement of the core temperature thus emphasizing that relaxational effects cannot be ignored when the star leaves hydrostatic equilibrium.Comment: 15 pages, To appear in Int. J. Mod. Phys.

Computational and theoretical aspects of a grain-boundary model at finite deformations

A model to describe the role of grain boundaries in the overall response of a polycrystalline material at small length scales subject to finite deformations is presented. Three alternative thermodynamically consistent plastic flow relations on the grain boundary are derived and compared using a series of numerical experiments. The numerical model is obtained by approximating the governing relations using the finite element method. In addition, the infinitesimal and finite deformation theories are compared, and the limitations of the former made clear

Computational and theoretical aspects of a grain-boundary model that accounts for grain misorientation and grain-boundary orientation

A detailed theoretical and numerical investigation of the infinitesimal single-crystal gradient plasticity and grain-boundary theory of Gurtin (2008) "A theory of grain boundaries that accounts automatically for grain misorientation and grain-boundary orientation". Journal of the Mechanics and Physics of Solids 56 (2), 640-662, is performed. The governing equations and flow laws are recast in variational form. The associated incremental problem is formulated in minimization form and provides the basis for the subsequent finite element formulation. Various choices of the kinematic measure used to characterize the ability of the grain boundary to impede the flow of dislocations are compared. An alternative measure is also suggested. A series of three-dimensional numerical examples serve to elucidate the theory

Simulation of electron transport in quantum well devices

Double barrier resonant tunneling diodes (DBRTD) have received much attention as possible terahertz devices. Despite impressive experimental results, the specifics of the device physics (i.e., how the electrons propagate through the structure) are only qualitatively understood. Therefore, better transport models are warranted if this technology is to mature. In this paper, the Lattice Wigner function is used to explain the important transport issues associated with DBRTD device behavior

Growth in demand and supply of pulses in India-A normative approach

The changing scenario of consumption and production of pulses will have significant influence on the demand- supply prospects of pulses in India. The country as whole, production of redgram had increased marginally (0.45%) during 1980-2012(Overall study period), though there is positive and significant growth in production(2.86%) during 1980-90 (Period-I), mainly due to lower growth during 1991-2012(period-II). The significant growth in production (1.39%) and productivity (1.04%) of bengalgram in the entire period except area (0.35%) was observed. However, growth in greengram production (1.14%) and productivity (1.21%) was found almost similar. In case of blackgram, positive growth rate in area, productivity and production in both the periods have ultimately resulted higher growth rates in the overall period. The growth in total pulses production indicated that growth in area (-0.10%) was negative while it was positive both in production (1.49%) and productivity (1.59%) during period-I. Similar pattern of growth was observed during period-II and in the overall study period. The estimated demand for pulses were 183.62 lakh tonnes over supply of 148.66 lakh tonnes indicating deficit of 34.96 lakh tonnes during 2001 –2011. Further, demand for pulses expected to reach 225.36 and 255.16 lakh tonnes in the year 2020 and 2030 respectively. Whereas, supply of pulses will reach 218.50 and 237.00 lakh tonnes in the same period indicating narrow gap between demand and supply in the future