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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Code inspection instructional validation

The Shuttle Data Systems Branch (SDSB) of the Flight Data Systems Division (FDSD) at Johnson Space Center contracted with Southwest Research Institute (SwRI) to validate the effectiveness of an interactive video course on the code inspection process. The purpose of this project was to determine if this course could be effective for teaching NASA analysts the process of code inspection. In addition, NASA was interested in the effectiveness of this unique type of instruction (Digital Video Interactive), for providing training on software processes. This study found the Carnegie Mellon course, 'A Cure for the Common Code', effective for teaching the process of code inspection. In addition, analysts prefer learning with this method of instruction, or this method in combination with other methods. As is, the course is definitely better than no course at all; however, findings indicate changes are needed. Following are conclusions of this study. (1) The course is instructionally effective. (2) The simulation has a positive effect on student's confidence in his ability to apply new knowledge. (3) Analysts like the course and prefer this method of training, or this method in combination with current methods of training in code inspection, over the way training is currently being conducted. (4) Analysts responded favorably to information presented through scenarios incorporating full motion video. (5) Some course content needs to be changed. (6) Some content needs to be added to the course. SwRI believes this study indicates interactive video instruction combined with simulation is effective for teaching software processes. Based on the conclusions of this study, SwRI has outlined seven options for NASA to consider. SwRI recommends the option which involves creation of new source code and data files, but uses much of the existing content and design from the current course. Although this option involves a significant software development effort, SwRI believes this option will produce the most effective results.

Orr, Kay↗
NASA NTRS2017

Further Validation of a CFD Code for Calculating the Performance of Two-Stage Light Gas Guns

Earlier validations of a higher-order Godunov code for modeling the performance of two-stage light gas guns are reviewed. These validation comparisons were made between code predictions and experimental data from the NASA Ames 1.5" and 0.28" guns and covered muzzle velocities of 6.5 to 7.2 km/s. In the present report, five more series of code validation comparisons involving experimental data from the Ames 0.22" (1.28" pump tube diameter), 0.28", 0.50", 1.00" and 1.50" guns are presented. The total muzzle velocity range of the validation data presented herein is 3 to 11.3 km/s. The agreement between the experimental data and CFD results is judged to be very good. Muzzle velocities were predicted within 0.35 km/s for 74% of the cases studied with maximum differences being 0.5 km/s and for 4 out of 50 cases, 0.5 - 0.7 km/s.

Ballistic Range↗
NASA NTRS1995

Effects of cavity dimensions, boundary layer, and temperature on cavity noise with emphasis on benchmark data to validate computational aeroacoustic codes

This report documents the results of an experimental investigation on the response of a cavity to external flowfields. The primary objective of this research was to acquire benchmark of data on the effects of cavity length, width, depth, upstream boundary layer, and flow temperature on cavity noise. These data were to be used for validation of computational aeroacoustic (CAA) codes on cavity noise. To achieve this objective, a systematic set of acoustic and flow measurements were made for subsonic turbulent flows approaching a cavity. These measurements were conducted in the research facilities of the Georgia Tech research institute. Two cavity models were designed, one for heated flow and another for unheated flow studies. Both models were designed such that the cavity length (L) could easily be varied while holding fixed the depth (D) and width (W) dimensions of the cavity. Depth and width blocks were manufactured so that these dimensions could be varied as well. A wall jet issuing from a rectangular nozzle was used to simulate flows over the cavity.

Ahuja, K. K.↗
NASA NTRS1992

Hypersonic code efficiency and validation studies

Renewed interest in hypersonic and supersonic flows spurred the development of the Compressible Navier-Stokes (CNS) code. Originally developed for external flows, CNS was modified to enable it to also be applied to internal high speed flows. In the initial phase of this study CNS was applied to both internal flow applications and fellow researchers were taught to run CNS. The second phase of this research was the development of surface grids over various aircraft configurations for the High Speed Research Program (HSRP). The complex nature of these configurations required the development of improved surface grid generation techniques. A significant portion of the grid generation effort was devoted to testing and recommending modifications to early versions of the S3D surface grid generation code.

Bennett, Bradford C.↗
NASA NTRS1992

NASA F-16XL supersonic laminar flow control program overview

The viewgraphs and discussion of the NASA supersonic laminar flow control program are provided. Successful application of laminar flow control to a High Speed Civil Transport (HSCT) offers significant benefits in reductions of take-off gross weight, mission fuel burn, cruise drag, structural temperatures, engine size, emissions, and sonic boom. The ultimate economic success of the proposed HSCT may depend on the successful adaption of laminar flow control, which offers the single most significant potential improvements in lift drag ratio (L/D) of all the aerodynamic technologies under consideration. The F-16XL Supersonic Laminar Flow Control (SLFC) Experiment was conceived based on the encouraging results of in-house and NASA supported industry studies to determine if laminar flow control is feasible for the HSCT. The primary objective is to achieve extensive laminar flow (50-60 percent chord) on a highly swept supersonic wing. Data obtained from the flight test will be used to validate existing Euler and Navier Stokes aerodynamic codes and transition prediction boundary layer stability codes. These validated codes and developed design methodology will be delivered to industry for their use in designing supersonic laminar flow control wings. Results from this experiment will establish preliminary suction system design criteria enabling industry to better size the suction system and develop improved estimates of system weight, fuel volume loss due to wing ducting, turbocompressor power requirements, etc. so that benefits and penalties can be more accurately assessed.

Fischer, Michael C.↗
NASA NTRS2000

Contribution of the Recent AUSM Schemes to the Overflow Code: Implementation and Validation

We shall present results of a recent collaborative effort between the authors attempting to implement the numerical flux scheme, AUSM+ and its new developments, into a widely used NASA code, OVERFLOW. This paper is intended to give a thorough and systematic documentation about the solutions of default test cases using the AUSNI+ scheme. Hence we will address various aspects of numerical solutions, such as accuracy, convergence rate, and effects of turbulence models, over a variety of geometries, speed regimes. We will briefly describe the numerical schemes employed in the calculations, including the capability of solving for low-speed flows and multiphase flows by employing the concept of numerical speed of sound. As a bonus, this low Mach number formulations also enhances convergence to steady solutions for flows even at transonic speed. Calculations for complex 3D turbulent flows were performed with several turbulence models and the results display excellent agreements with measured data.

Liou, Meng-Sing↗
NASA NTRS1993

Validation of multi-temperature nozzle flow code NOZNT

A computer code NOZNT (Nozzle in n-Temperatures), which calculates one-dimensional flows of partially dissociated and ionized air in an expanding nozzle, is tested against five existing sets of experimental data. The code accounts for: a) the differences among various temperatures, i.e., translational-rotational temperature, vibrational temperatures of individual molecular species, and electron-electronic temperature, b) radiative cooling, and c) the effects of impurities. The experimental data considered are: 1) the sodium line reversal and 2) the electron temperature and density data, both obtained in a shock tunnel, and 3) the spectroscopic emission data, 4) electron beam data on vibrational temperature, and 5) mass-spectrometric species concentration data, all obtained in arc-jet wind tunnels. It is shown that the impurities are most likely responsible for the observed phenomena in shock tunnels. For the arc-jet flows, impurities are inconsequential and the NOZNT code is validated by numerically reproducing the experimental data.

Park, Chul↗
NASA NTRS2006

Source Noise Modeling Efforts for Fan Noise in NASA Research Programs

There has been considerable progress made in fan noise prediction over the past 15 years. NASA has conducted and sponsored research that has improved both tone and broadband fan noise prediction methods. This presentation highlights progress in these areas with emphasis on rotor/stator interaction noise sources. Tone noise predictions are presented for an advanced prediction code called "LINFLUX". Comparisons with data are" included for individual fan duct modes. There has also been considerable work developing new fan broadband noise prediction codes and validation data from wind tunnel model tests. Results from several code validation exercises are presented that show improvement of predicted sound power levels. A summary is included with recommendations for future work.

Huff, Dennis L.↗
NASA NTRS1994

A Selection of Experimental Test Cases for the Validation of CFD Codes, Volume 2

This report presents the results of a study by Working Group 14 of the AGARD Fluid Dynamics Panel. The thirty nine test cases that are documented cover the subsonic, transonic, and supersonic flow regimes and five classes of geometries. Included in the five classes of geometries are: Two Dimensional Airfoils; Three Dimensional Wings, designed for predominantly attached flow conditions; Slender Bodies, typical of missile type configurations; Delta Wings, characterized by a conical type of vortex flow; and Complex Configurations, either in a geometrical sense or because of complicated flow interactions. The report is presented in two volumes. Volume 1 provides a review of the theoretical and experimental requirements, a general introduction, summary of the test cases and recommendations for the future. Volume 2 contains detailed information on the test cases.

Advisory Group for Aerospace Research and Developm↗
NASA NTRS1996

Comparison of Predicted Low Speed Fan Rotor/Stator Interaction Modes to Measured

The V072 Rotor Wake/Stator Interaction Code is widely used as a state-of-the-art prediction code. This paper validates the code by comparing experimentally measured mode levels to those predicted by V072. The experimental mode levels were measured by the Rotating Rake system installed on the 48 inch Active Noise Control Fan at NASA Lewis Research Center. V072 predicted mode levels by inputting the actual wake profiles of the ANCF rotor measured by a 2-component hotwire. The mode levels were also predicted from the V072 wake models. V072 reasonably predicts the mode levels within the design limits of the code.

Sutliff, Daniel L.↗
NASA NTRS1997

Validation of Framework Code Approach to a Life Prediction System for Fiber Reinforced Composites

The grant was conducted by the MMC Life Prediction Cooperative, an industry/government collaborative team, Ohio Aerospace Institute (OAI) acted as the prime contractor on behalf of the Cooperative for this grant effort. See Figure I for the organization and responsibilities of team members. The technical effort was conducted during the period August 7, 1995 to June 30, 1996 in cooperation with Erwin Zaretsky, the LERC Program Monitor. Phil Gravett of Pratt & Whitney was the principal technical investigator. Table I documents all meeting-related coordination memos during this period. The effort under this grant was closely coordinated with an existing USAF sponsored program focused on putting into practice a life prediction system for turbine engine components made of metal matrix composites (MMC). The overall architecture of the NMC life prediction system was defined in the USAF sponsored program (prior to this grant). The efforts of this grant were focussed on implementing and tailoring of the life prediction system, the framework code within it and the damage modules within it to meet the specific requirements of the Cooperative. T'he tailoring of the life prediction system provides the basis for pervasive and continued use of this capability by the industry/government cooperative. The outputs of this grant are: 1. Definition of the framework code to analysis modules interfaces, 2. Definition of the interface between the materials database and the finite element model, and 3. Definition of the integration of the framework code into an FEM design tool.

Gravett, Phillip↗
NASA NTRS2008

Supersonic Combusting Jet Experiments for Code Development and Validation

Computational fluid dynamics (CFD) methods based on the Reynolds averaged Navier-Stokes (RANS) equations are extensively employed in the design of hypersonic airbreathing engines. A fundamental weakness in these methods is the accurate mathematical modeling of turbulence and turbulence-combustion interactions. This paper is one of a companion pair of papers which describe the use of the combined dual pump CARS and newly developed interferometric Rayleigh scattering optical system to acquire time-accurate turbulence and mixing data with which to aid calibration and verification of the current turbulence models. This test program consisted of a pilot laboratory-scale experiment used to develop the optical system and data acquisition techniques, and a significantly larger experiment to acquire the necessary turbulence data. The flow is an axially-symmetric, supersonic, combusting, free jet that provides good optical access, consisting of a central jet of hot "vitiated air" and a coflow jet of hydrogen or ethylene fuel. In this paper the development of both experiments is described. Facility and flow visualization data are presented for various types of flames, including the flames selected for detailed study with the CARS/Rayleigh optical techniques.

Cutler, Andrew D.↗
NASA NTRS2014

Validation of CFD Codes for Parawing Geometries in Subsonic to Supersonic Flows

Computational Fluid Dynamic studies of a rigid parawing at Mach numbers from 0.8 to 4.65 were carried out using three established inviscid, viscous and independent panel method codes. Pressure distributions along four chordwise sections of the wing were compared to experimental wind tunnel data gathered from NASA technical reports. Results show good prediction of the overall trends and magnitudes of the pressure distributions for the inviscid and viscous solvers. Pressure results for the panel method code diverge from test data at large angles of attack due to shock interaction phenomena. Trends in the flow behavior and their effect on the integrated force and moments on this type of wing are examined in detail using the inviscid CFD code results.

Direct Entry Trajectory↗
NASA NTRS2003

Pulsed Inductive Thruster (PIT): Modeling and Validation Using the MACH2 Code

Numerical modeling of the Pulsed Inductive Thruster exercising the magnetohydrodynamics code, MACH2 aims to provide bilateral validation of the thruster's measured performance and the code's capability of capturing the pertinent physical processes. Computed impulse values for helium and argon propellants demonstrate excellent correlation to the experimental data for a range of energy levels and propellant-mass values. The effects of the vacuum tank wall and massinjection scheme were investigated to show trivial changes in the overall performance. An idealized model for these energy levels and propellants deduces that the energy expended to the internal energy modes and plasma dissipation processes is independent of the propellant type, mass, and energy level.

Schneider, Steven↗
NASA NTRS1996

Validation of NASA Thermal Ice Protection Computer Codes: Program Overview - Part 1

The Icing Technology Branch at NASA Lewis has been involved in an effort to validate two thermal ice protection codes developed at the NASA Lewis Research Center. LEWICE/Thermal (electrothermal deicing & anti-icing), and ANTICE (hot-gas & electrothermal anti-icing). The Thermal Code Validation effort was designated as a priority during a 1994 'peer review' of the NASA Lewis Icing program, and was implemented as a cooperative effort with industry. During April 1996, the first of a series of experimental validation tests was conducted in the NASA Lewis Icing Research Tunnel(IRT). The purpose of the April 96 test was to validate the electrothermal predictive capabilities of both LEWICE/Thermal, and ANTICE. A heavily instrumented test article was designed and fabricated for this test, with the capability of simulating electrothermal de-icing and anti-icing modes of operation. Thermal measurements were then obtained over a range of test conditions, for comparison with analytical predictions. This paper will present an overview of the test, including a detailed description of: (1) the validation process; (2) test article design; (3) test matrix development; and (4) test procedures. Selected experimental results will be presented for de-icing and anti-icing modes of operation. Finally, the status of the validation effort at this point will be summarized. Detailed comparisons between analytical predictions and experimental results are contained in the following two papers: 'Validation of NASA Thermal Ice Protection Computer Codes: Part 2- The Validation of LEWICE/Thermal' and 'Validation of NASA Thermal Ice Protection Computer Codes: Part 3-The Validation of ANTICE'

Miller, Dean↗
NASA NTRS1989

An Experimental Method for Measuring Water Droplet Impingement Efficiency on Two- and Three-dimensional Bodies

An experimental method was developed to determine the droplet impingement characteristics on 2-D and 3-D bodies. The experimental results provide the essential droplet impingement data required to validate water droplet trajectory codes, which are used in the analysis of aircraft icing. A body, whose water droplet impingement characteristics are required, is covered at strategic locations by thin strips of moisture absorbing (blotter) paper, and is exposed to an air stream containing a water dye solution spray cloud. Water droplet impingement data are extracted from the dyed blotter strips by measuring the optical reflectance of the dye deposit on the strips, using an automated reflectometer. Models tested include a 4-inch diameter cylinder, a NACA 652015 airfoil section, a MS(1)-0317 supercritical airfoil section, three simulated ice shapes, an axisymmetric inlet and a Boeing 737-300 inlet model. Detailed descriptions of the dye tracer technique, instrumentation, data reduction method and the results obtained are presented. Analytical predictions of collection efficiency characteristics for most test configurations are included for comparison.

Trajectory code validation↗