Engineering topics

Marraffa, Lionel

Publications and source records attributed to Marraffa, Lionel.

4 records

NASA NTRS1989

Numerical simulation of unsteady flows generated by dissociating nitrogen diffusion

An explicit time accurate predictor-corrector scheme, similar to MacCormack's, has been used to simulate unsteady nonequilibrium laminar chemically-reacting diffusion-reaction generated flows. A zonal approach, along with nonstructured boundaries, allows computation of internal and external flow with the same computer code. Results for equilibrium flows generated by dissociating, vibrationally relaxing nitrogen in a rectangular chamber are presented. The unsteady flows were generated strictly by the chemical reactions and concentration gradients.

Marraffa, Lionel↗

NASA NTRS1988

A physically consistent model for artificial dissipation in transonic potential flow computations

The effect that artificial dissipation has on numerical solutions of the transonic Full Potential Equation (FPE) are investigated by comparing the artificially dissipative FPE to a Physically Dissipative Potential (PDP) equation. Analytic expressions were derived from the variables C and M sub c that are used in the artificial density formulation. It was shown that these new values generate artificial dissipation which is equivalent to the physical dissipation existing in the PDP equation. The new expression for the variables C and M sub c can easily be incorporated into the existing full potential codes which are based either on the artificial density or on the artificial viscosity formulation. A comparison of Physically Dissipative Potential (PDP), Artificial Density or Viscosity (ADV), Artificial Mass Flux (AMF), and ADV with variable C and M sub c formulation (MCC) is also presented.

Dulikravich, George S.↗

NASA NTRS1988

A survey of the reaction rate constants for the thermal dissociation and recombination of nitrogen and oxygen

The objective of the present report is to survey the various values of forward and backward reaction rate constants used by investigators in the field of high-temperature (T greater than 2000 K) gas reactions involving nitrogen and oxygen only. The objective is to find those values that correlate well so that they can be used for the studies of hypersonic flow and supersonic combustion with reasonable confidence. Relatively good agreement among these various values is observed for temperatures lower than 10,000 K.

Marraffa, Lionel↗

NASA NTRS1988

Computations of unsteady dissociating nitrogen flows

A time-accurate computer program has been developed to solve flows involving nonequilibrium chemical reactions and vibrational relaxation. The program is based on a multidomain approach and an explicit MacCormack scheme. Results are presented for three simple test cases, involving nitrogen dissociation in a closed box.

Marraffa, Lionel↗