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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Atomic collision with rigid rotor at subthreshold energies compared to theoretical predictions of resonance energies and several variational principles for phase shift
Adiabatic approximation for nonreactive molecular collisions obtained from variational principle
Excited state energy upper bounds in second order perturbation theory using Hylleraas variational principle
Sum rule properties of finite set of wave functions obtained from application of variational principles to basis functions linear combinations
Variational principles of relativistic fluid thermodynamics
Variational method to approximate solutions of perturbation equations, perturbation analyses, and use of perturbation theory to infer variational principle
Steady state time dependent perturbation theory and variational principles
Nonconservative problems motion stability analysis based on restricted admissible displacements, establishing two variational principles
Nonlinear panel flutter for random excitation and linear/nonlinear aerodynamic loading, using Rayleigh-Ritz approximation to Hamilton variational principle
Two dimensional structures large strain elastoplastic analysis by finite element method, using variational principles to derive equilibrium equations
Elastic plate uniform extension with rectangular crack by three dimensional bending theory, using variational principle
Finite element method approximations outside variational principle in elasticity problems, examining convergence to exact solution
Nonlinear panel flutter analysis and response under random excitation or nonlinear aerodynamic loading, using Rayleigh-Ritz approximation to Hamilton variational principle
Relativistic fluid thermodynamics for compressible fluid reversible adiabatic flow, using variational principle to derive stress-energy tensor
The dynamic characteristics of two-stage slender elastic body were investigated. The first stage, containing a solid-fuel rocket, possesses variable mass while the second stage, envisioned as a flexible case, contains packaged instruments of constant mass. The mathematical formulation was in terms of vector equations of motion transformed by a variational principle into sets of scalar differential equations in terms of generalized coordinates. Solutions to the complete equations were obtained numerically by means of finite difference techniques. The problem has been programmed in the FORTRAN 4 language and solved on an IBM 360/50 computer. Results for limited cases are presented showing the nature of the solutions.
The finite element method is extended to thermal analysis by forming a variance analysis of temperature results so that the sensitivity of predicted temperatures to uncertainties in input variables is determined. The temperature fields within a finite number of elements are described in terms of the temperatures of vertices and the variational principle is used to minimize the integral equation describing thermal potential energy. A computer calculation yields the desired solution matrix of predicted temperatures and provides information about initial thermal parameters and their associated errors. Sample calculations show that all predicted temperatures are most effected by temperature values along fixed boundaries; more accurate specifications of these temperatures reduce errors in thermal calculations.
The uniaxial deformation of an elastic-plastic medium containing a doubly periodic square array of circular cylindrical voids is studied under plane-strain conditions. Both the effects of geometrical nonlinearities resulting from large deformation and physical nonlinearities arising from plastic material behavior are included in formulating the problem. A variational principle is used as the basis for implementing a finite-element solution. Results are obtained for the change in void shape and size under increasing overall strain, the overall tensile behavior of the material with voids, and the development of the plastic zone about a void.
Various theorems in the theory of spinless particle scattering by a real central potential are derived directly from the Kohn variational principle.