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NASA NTRS1995

Direct adaptive performance optimization of subsonic transports: A periodic perturbation technique

Aircraft performance can be optimized at the flight condition by using available redundancy among actuators. Effective use of this potential allows improved performance beyond limits imposed by design compromises. Optimization based on nominal models does not result in the best performance of the actual aircraft at the actual flight condition. An adaptive algorithm for optimizing performance parameters, such as speed or fuel flow, in flight based exclusively on flight data is proposed. The algorithm is inherently insensitive to model inaccuracies and measurement noise and biases and can optimize several decision variables at the same time. An adaptive constraint controller integrated into the algorithm regulates the optimization constraints, such as altitude or speed, without requiring and prior knowledge of the autopilot design. The algorithm has a modular structure which allows easy incorporation (or removal) of optimization constraints or decision variables to the optimization problem. An important part of the contribution is the development of analytical tools enabling convergence analysis of the algorithm and the establishment of simple design rules. The fuel-flow minimization and velocity maximization modes of the algorithm are demonstrated on the NASA Dryden B-720 nonlinear flight simulator for the single- and multi-effector optimization cases.

Espana, Martin D.↗

NASA NTRS1976

Some recent developments in the aerodynamics of wings for high speeds

The items discussed are: (1) a recently proposed correction formula for the effect of compressibility in two dimensional subsonic flow; (2) the equivalence rule and the area rule for transonic speeds; (3) reciprocal relations in linearized wing theory; and (4) some general results connected with the problem of minimum wave resistance. The paper concludes with an example showing indentation of the fuselage to obtain favorable interference with the wing at supersonic speeds.

Jones, R. T.↗

NASA NTRS1990

Liquid Rocket Booster (LRB) for the Space Transportation System (STS) Systems Study. Amendment 13: Orientation meeting

The topics are presented in viewgraph form and include the following: LRB study results summary -- Feb. 1989; LRB study results -- Jan. 1990; Shuttle configuration with booster options; LRB study results -- Sept. 1990; LRB statement of work tasks; ground rules and assumptions; study flow of design, manufacturing/production, and test program/certification; study products; study schedule; and candidate 1.5 stage engine arrangements.

Source record↗

NASA NTRS1995

Acoustic field in unsteady moving media

In the interaction of an acoustic field with a moving airframe the authors encounter a canonical initial value problem for an acoustic field induced by an unsteady source distribution, q(t,x) with q equivalent to 0 for t less than or equal to 0, in a medium moving with a uniform unsteady velocity U(t)i in the coordinate system x fixed on the airframe. Signals issued from a source point S in the domain of dependence D of an observation point P at time t will arrive at point P more than once corresponding to different retarded times, Tau in the interval (0, t). The number of arrivals is called the multiplicity of the point S. The multiplicity equals 1 if the velocity U remains subsonic and can be greater when U becomes supersonic. For an unsteady uniform flow U(t)i, rules are formulated for defining the smallest number of I subdomains V(sub i) of D with the union of V(sub i) equal to D. Each subdomain has multiplicity 1 and a formula for the corresponding retarded time. The number of subdomains V(sub i) with nonempty intersection is the multiplicity m of the intersection. The multiplicity is at most I. Examples demonstrating these rules are presented for media at accelerating and/or decelerating supersonic speed.

Bauer, F.↗

NASA NTRS2004

Development and Evaluation of an Airborne Separation Assurance System for Autonomous Aircraft Operations

NASA Langley Research Center is developing an Autonomous Operations Planner (AOP) that functions as an Airborne Separation Assurance System for autonomous flight operations. This development effort supports NASA s Distributed Air-Ground Traffic Management (DAG-TM) operational concept, designed to significantly increase capacity of the national airspace system, while maintaining safety. Autonomous aircraft pilots use the AOP to maintain traffic separation from other autonomous aircraft and managed aircraft flying under today's Instrument Flight Rules, while maintaining traffic flow management constraints assigned by Air Traffic Service Providers. AOP is designed to facilitate eventual implementation through careful modeling of its operational environment, interfaces with other aircraft systems and data links, and conformance with established flight deck conventions and human factors guidelines. AOP uses currently available or anticipated data exchanged over modeled Arinc 429 data buses and an Automatic Dependent Surveillance Broadcast 1090 MHz link. It provides pilots with conflict detection, prevention, and resolution functions and works with the Flight Management System to maintain assigned traffic flow management constraints. The AOP design has been enhanced over the course of several experiments conducted at NASA Langley and is being prepared for an upcoming Joint Air/Ground Simulation with NASA Ames Research Center.

Barhydt, Richard↗

NASA NTRS2005

Amateur Cleanrooms: Costs May Not Offset Benefits

Contamination and Coatings Branch During my career at NASA, I have encountered a variety of cleanroom systems. With many projects, cost pressures and lack of adequate facilities have forced the managers to resort to amateur cleanrooms to manufacture spacecraft and instruments. These rooms are usually spaces that have been used for other purposes that are converted to cleanroom, usually without the assistance of a contamination control specialist. Often, scientists and engineers are successful in converting an area for experimental use. However, when the area is used for production, countless difficulties are encountered. This paper will document some of the disasters that I have personally witnessed and offer some guidelines for contamination professionals to follow if you are called upon to assist in the development of new cleanrooms. Cleanroom come in all shapes and sizes from special purpose mini-environments (such as flow benches) to large, expansive production facilities. These areas may require a variety of unit operations to be carried out within a short range of each other. The design of the cleanroom should account for compatibilities of these operations to protect the product and personnel. The level of cleanliness has traditionally been associated with the method of ventilation. However, just because and =ea has HEPA filters and greater that 20 air changes per hour does not mean that it is a cleanroom. Airflow is extremely complex; the only way to properly design a cleanroom is through the use of a computer based model. In the aerospace industry, few engineered cleanrooms are modeled. Modeling has been perceived as expensive; however, modern programs and fast computers are changing perception. It is the lack of appreciation for how air flow and location within a cleanroom affects the product that causes most of the problems I have experienced. Currently, the rules defining the best air flow design practices are based on simplistic historical data that are often wrong. The performance of a cleanroom is defined by a set of complex interactions between the airflow, sources of contamination and heat, position of the air terminals and exhausts as well as the objects occupying the space in question. These subtleties are almost never appreciated in the setup of amateur cleanrooms (and sadly, in some engineered cleanroom as well). Experience with the room, measurement of air flows in the room, and black light inspections can be used to

Ramsey, W. Lawrence↗

NASA NTRS2013

Workflow-Based Software Development Environment

The Software Developer's Assistant (SDA) helps software teams more efficiently and accurately conduct or execute software processes associated with NASA mission-critical software. SDA is a process enactment platform that guides software teams through project-specific standards, processes, and procedures. Software projects are decomposed into all of their required process steps or tasks, and each task is assigned to project personnel. SDA orchestrates the performance of work required to complete all process tasks in the correct sequence. The software then notifies team members when they may begin work on their assigned tasks and provides the tools, instructions, reference materials, and supportive artifacts that allow users to compliantly perform the work. A combination of technology components captures and enacts any software process use to support the software lifecycle. It creates an adaptive workflow environment that can be modified as needed. SDA achieves software process automation through a Business Process Management (BPM) approach to managing the software lifecycle for mission-critical projects. It contains five main parts: TieFlow (workflow engine), Business Rules (rules to alter process flow), Common Repository (storage for project artifacts, versions, history, schedules, etc.), SOA (interface to allow internal, GFE, or COTS tools integration), and the Web Portal Interface (collaborative web environment

Izygon, Michel E.↗

NASA NTRS1975

Integration of aft-fuselage-mounted flow through engine nacelles on an advanced transport configuration at Mach numbers from 0.6 to 1.0

An approximately 1/30th-scale model of a CTOL aircraft designed for efficient cruise between Mach 0.9 and 0.98 was tested in the Lewis Research Center's 8- by 6-Foot Supersonic Wind Tunnel. Aft-fuselage axial force and pressure were measured for a series of locally area-ruled engine installations. Two flow-through nacelles with different exit diameters which simulated inlet mass flow ratios of 0.46 and 0.6 (based on maximum nacelle cross-sectional) area were investigated. Both an NACA-1 cowl and a blunter supercritical cowl were tested with these nacelles. Variations in the amount of local area ruling were investigated and an aft fuselage without nacelles was tested for reference. Results observed with flow-through nacelles indicate that efficient cruise may be obtained on this type of aircraft with aft-fuselage-mounted engine nacelles.

Blaha, B. J.↗

NASA NTRS1981

Inviscid transonic flow over axisymmetric bodies

Axisymmetric transonic flow is of interest not only because of its practical application to missile and launch vehicle aerodynamics but also because of its relation, in terms of area rule, to fully three dimensional flow. RAXBOD computer program analyzes steady, inviscid, irrotational, transonic flow over axisymmetric bodies in free air. RAXBOD uses finite-difference relaxation method to solve numerically exact formulation of disturbance velocity potential with exact surface boundary conditions. Agreement with available experimental results has been good in cases where viscous effects and wind-tunnel wall interference are not important.

South, J. C., Jr.↗

NASA NTRS1951

Concerning the flow about ring-shaped cowlings Part VI : further measurements on inlet devices

The present report presents as a supplement to the fourth report (available as ATI 5045, Air Materiel Command) in the series of investigations concerning the flow about ring-shaped cowlings further wind-tunnel measurements on inlet devices which are to show the influence of the radius of the nose of the cowling on the flow conditions. Moreover, a simple rule for the design of such arrangements, containing a hub in the interior, is suggested.

AIR FLOW - ENGINE COWLINGS↗

NASA NTRSDate not supplied

Derivation of Effective Properties Based on Porous Scale Simulations Using Filtering Techniques

This study presents a method for derivation of effective properties at the interface and in-depth of porous materials. The method defines a Representative Elementary Volume (REV) and applies filtering techniques to computer effective properties such as porosity and flow quantities, such as velocity and pressure. The script, developed to process the data was tested on the VTK type files that contain the mesh information and the flow solution. The method allows to choose between two types of filters, such as cellular and top-hat and define the size of the REV and number of samples along the domain. Extraction of the REV from the domain is performed to exact boundaries requested for the user. This is done using a triangulation technique and cutting through the cells to comply to the requested boundaries of the volume. The method can be applied to both structured and unstructured meshes. Filtering the material porosity and flow quantities involves integration of the numerical data. The algorithm provides three integration methods, such as Riemann sum, Monte Carlo and Quadrature rule to perform the integration. The Monte-Carlo technique permits the use of either uniform or linearly spaced distribution of points. The Quadrature rule is currently applicable to tetrahedral element types. The Monte Carlo and Quadrature rule methods require interpolation of the flow quantities at the sample points. For interpolation, two methods were tested and are readily available, Gaussian interpolation and re-sampling. It has been shown that re-sampling method has better consistency and acceptable accuracy in interpolation of the data. The algorithm was written in Python language and uses a number of modules. The major module besides numpy is PyVista. It is used to process the computational domain, clip the REV and interpolate the data. Quadrature rule integration was performed using a quadpy module. ParaView software was used externally to convert the flow solution to the VTK (or more specifically VTU) format. Integration of ParaView in the same environment with PyVista encountered problems and could not be implemented in this work. The developed algorithm is expected to be applicable to unstructured meshes and more complex porous structures as soon as the data can be passed in VTK type format. With the report is provided Python script for filtering the solution and a Matlab script for simple generation and processing of 2-D and 3-D porous channel geometries. The two scripts don't communicate.

Alexsander Zibitsker↗

NASA NTRS1977

Boundary-value problem of configurations with compressible free vortex flow

A self-consistent version of the compressible boundary-value problem for configurations with leading-edge vortex separation is formulated, based on the assumption that the compressible flow field is controlled by the linearized potential equation. The stream surface boundary condition and the zero pressure jump condition of the compressible free vortex flows are analyzed; application of the Goethert rule permits the compressible nonlinear boundary-value problem for the subsonic flow domain to be transformed into an equivalent nonlinear incompressible problem. The compressibility corrections developed are used in numerical calculations of subsonic leading-edge vortex flows about planar wing geometries. The sample calculations, employing an inviscid flow model in which the wing and vortex sheets are represented by piecewise continuous quadratic doublet sheet distributions, are applicable to high subsonic Mach numbers.

Brune, G. W.↗

NASA NTRS1987

Advanced experimental techniques for transonic testing

Problems common to wind tunnels, including low Reynolds numbers, wall interference, support interference, and flow unsteadiness are discussed, and it is noted that with increasing aircraft size, existing transonic tunnels are becoming more inadequate in terms of their Reynolds-number capability. Problems attributed to scale effect are covered, and techniques for increasing Reynolds number are presented. These include operating with a heavy gas or a mixture of gases, increasing the operating pressure in the tunnel, increasing the size of the model, and/or reducing the test temperature. Acceptable levels of flow unsteadiness are reviewed, along with the problems associated with the flow over wind-tunnel models influenced by flow unsteadiness. Sources of flow unsteadiness present in a continuous transonic tunnel driven by a compressor or a fan are listed, and rules for ensuring low levels of flow unsteadiness are given.

Kilgore, Robert A.↗

NASA NTRS1994

A new algorithm for five-hole probe calibration, data reduction, and uncertainty analysis

A new algorithm for five-hole probe calibration and data reduction using a non-nulling method is developed. The significant features of the algorithm are: (1) two components of the unit vector in the flow direction replace pitch and yaw angles as flow direction variables; and (2) symmetry rules are developed that greatly simplify Taylor's series representations of the calibration data. In data reduction, four pressure coefficients allow total pressure, static pressure, and flow direction to be calculated directly. The new algorithm's simplicity permits an analytical treatment of the propagation of uncertainty in five-hole probe measurement. The objectives of the uncertainty analysis are to quantify uncertainty of five-hole results (e.g., total pressure, static pressure, and flow direction) and determine the dependence of the result uncertainty on the uncertainty of all underlying experimental and calibration measurands. This study outlines a general procedure that other researchers may use to determine five-hole probe result uncertainty and provides guidance to improve measurement technique. The new algorithm is applied to calibrate and reduce data from a rake of five-hole probes. Here, ten individual probes are mounted on a single probe shaft and used simultaneously. Use of this probe is made practical by the simplicity afforded by this algorithm.

Reichert, Bruce A.↗

NASA NTRS1972

Calculative techniques for transonic flows about certain classes of wing body combinations

Procedures based on the method of local linearization and transonic equivalence rule were developed for predicting properties of transonic flows about certain classes of wing-body combinations. The procedures are applicable to transonic flows with free stream Mach number in the ranges near one, below the lower critical and above the upper critical. Theoretical results are presented for surface and flow field pressure distributions for both lifting and nonlifting situations.

Stahara, S. S.↗

NASA NTRS1986

Two-phase flows and heat transfer within systems with ambient pressure above the thermodynamic critical pressure

In systems where the design inlet and outlet pressures P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.

Hendricks, R. C.↗

NASA NTRS1986

Two-phase flows and heat transfer within systems with ambient pressure above the thermodynamic critical pressure

In systems where the design inlet and outlet pressure P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.

Hendricks, R. C.↗

NASA NTRS2000

Single Airfoil Gust Response Problem

An unsteady aerodynamic code, called GUST3D, has been developed to solve the single, non-constant coefficient, inhomogeneous convective wave equation for flows with periodic vortical disturbance. The code uses a frequency-domain approach with second-order central differences and a Sommerfeld radiation condition in the far field. It has been extensively validated on model problems with analytical solutions. GUST3D requires as input certain mean flow quantities which are calculated separately by a potential flow solver. This solver calculates the mean flow using a Gothert's Rule approximation. On the airfoil surface, it uses the solution calculated by the potential code FL036. A figure shows the mean pressure along the airfoil surface. To calculate the unsteady pressure, GUST3D was run oil systematically refined grids to obtain a converged solution at each frequency. It was found that 24 points per wavelength was sufficient for convergence. The location of the outer grid boundary was also varied to check for sensitivity to the far-field boundary condition.

Scott, James R.↗