Engineering topics

Fay, John F.

Publications and source records attributed to Fay, John F..

7 records

NASA NTRS1993

Pressure dither in venting analyses

Venting analyses simulate the time-dependent flow of air or another gas from one compartment to another, or to an ambient profile. The flow through the vent connecting the compartments is assumed to be one-dimensional, quasi-steady, and isentropic with an empirical discharge coefficient included to account for irreversible flow losses. When a venting analysis is performed numerically, an upper limit on the accuracy exists due to the effects of the numerical integration method. Because this manifests itself in a first-order method by a rapid oscillation about the true answer, this phenomenon is referred to as pressure dither. This paper explores the origin of the phenomenon and gives simple formulae for predicting when it will occur and the greatest achievable accuracy for a given time step.

Fay, John F.↗

NASA NTRS1993

Venting through multiple-layer insulation on Space Station Freedom. I - Flow rate testing and analysis

A test was conducted to determine the venting characteristics of multiple-layer insulation (MLI). It involved forcing air through four samples of MLI components and measuring the pressure differences and flow rates. Results from this test have been used to create a mathematical model of the flow through the MLI components. This model is used in a companion paper to predict the results of a second test and the venting behavior of MLI on the Space Station.

Sharp, Jeffrey B.↗

NASA NTRS1993

Venting through multiple-layer insulation on Space Station Freedom. II - Ascent rate pressure chamber testing

A test was conducted to determine the venting characteristics of the multiple-layer insulation (MLI) to be installed on the Space Station Freedom (SSF). A full MLI blanket with inter-blanket joints was installed onto a model of a section of the SSF pressure wall, support structure, and debris shield. Data were taken from this test and were used to predict the venting of the actual Space Station pressure-wall/MLI/debris-shield assemply during launch and possible re-entry. It was found that the pressure differences across the debris shields and MLI blankets were well within the specified limits in all cases.

Sharp, Jeffrey B.↗

NASA NTRS1992

Laminar hypersonic flow over a compression using the HANA code

A hypersonic blunt-body code, HANA (Hypersonic Analysis for Aerobrakes), has been used to model the flow with compression corner angles of 15 and 24 degrees. A comparison is made between experimental flow data and numerical results of previous investigations which include surface pressures, skin friction coefficients, heat transfer rates, and flow field geometries.

Fay, John F.↗

NASA NTRS1991

Aerothermodynamic environment predictions in support of the Aeroassist Flight Experiment

A computational fluid dynamic (CFD) simulation has been made of the flow past an Aeroassist Flight Experiment (AFE) aerobrake model with a payload and sting. The simulation involves solving the complete Navier-Stokes equations in three dimensions. Comparisons with data taken in a Mach 10 wind tunnel test are made and agreement is shown to be very good. Points of comparison include the aerobrake surface pressure and heat transfer rate, the sting surface streamlines, and the sting heat transfer rate. The dependence of the solution on the grid is also explored. Finally, predictions are made for conditions which correspond to a hypersonic shock tunnel force and moment test to be carried out later this year.

Fay, John F.↗

NASA NTRS1991

Aerobrake aerothermodynamic environment predictions in support of the Aeroassist Flight Experiment

A computational fluid dynamic (CFD) simulation of the flow past an Aeroassist Flight Experiment (AFE) aerobrake under wind tunnel test conditions has been made. The Navier-Stokes equations in three dimensions were solved numerically using a finite-volume, implicit approach. Comparisons with experimental data include surface pressures and heat transfer rates and aerodynamic coefficients. Agreement with experiment is shown to be excellent. The dependence of the solution on the computational grid is explored. The present work is preliminary to simulation of the flow past the AFE under flight conditions, which at present cannot be duplicated with ground-based experimental facilities.

Fay, John F.↗

NASA NTRS1990

Stability analysis of multigrid acceleration methods for the solution of partial differential equations

A calculation is made of the stability of various relaxation schemes for the numerical solution of partial differential equations. A multigrid acceleration method is introduced, and its effects on stability are explored. A detailed stability analysis of a simple case is carried out and verified by numerical experiment. It is shown that the use of multigrids can speed convergence by several orders of magnitude without adversely affecting stability.

Fay, John F.↗