Engineering topics

Barger, Raymond L.

Publications and source records attributed to Barger, Raymond L..

17 records

NASA NTRS1994

Automatic procedures for computing complete configuration geometry from individual component descriptions

Procedures are derived for developing a complete airplane surface geometry starting from component descriptions. The procedures involve locating the intersection lines of adjacent components and omitting any regions for which part of one surface lies within the other. The geometry files utilize the wave-drag (Harris) format, and output files are written in Hess format. Two algorithms are used: one, if both intersecting surfaces have airfoil cross sections; the other, if one of the surfaces has circular cross sections. Some sample results in graphical form are included.

Barger, Raymond L.↗

NASA NTRS1994

Automatic computation of Euler-marching and subsonic grids for wing-fuselage configurations

Algebraic procedures are described for the automatic generation of structured, single-block flow computation grids for relatively simple configurations (wing, fuselage, and fin). For supersonic flows, a quasi two-dimensional grid for Euler-marching codes is developed, and some sample results in graphical form are included. A type of grid for subsonic flow calculation is also described. The techniques are algebraic and are based on a generalization of the method of transfinite interpolation.

Barger, Raymond L.↗

NASA NTRS1993

Automatic computation of wing-fuselage intersection lines and fillet inserts with fixed-area constraint

Procedures for automatic computation of wing-fuselage juncture geometry are described. These procedures begin with a geometry in wave-drag format. First, an intersection line is computed by extrapolating the wing to the fuselage. Then two types of filleting procedures are described, both of which utilize a combination of analytical and numerical techniques appropriate for automatic calculation. An analytical technique for estimating the added volume due to the fillet is derived, and an iterative procedure for revising the fuselage to compensate for this additional volume is given. Sample results are included in graphical form.

Barger, Raymond L.↗

NASA NTRS1992

A method for designing blended wing-body configurations for low wave drag

A procedure for tailoring a blended wing-body configuration to reduce its computed wave drag is described. The method utilizes an iterative algorithm within the framework of first-order linear theory. Four computed examples are included. In each case, the zero-lift wave drag was reduced without an increase in the drag due to lift.

Barger, Raymond L.↗

NASA NTRS1992

Trajectory fitting in function space with application to analytic modeling of surfaces

A theory for representing a parameter-dependent function as a function trajectory is described. Additionally, a theory for determining a piecewise analytic fit to the trajectory is described. An example is given that illustrates the application of the theory to generating a smooth surface through a discrete set of input cross-section shapes. A simple procedure for smoothing in the parameter direction is discussed, and a computed example is given. Application of the theory to aerodynamic surface modeling is demonstrated by applying it to a blended wing-fuselage surface.

Barger, Raymond L.↗

NASA NTRS1992

Diffracted and head waves associated with waves on nonseparable surfaces

A theory is presented for computing waves radiated from waves on a smooth surface. With the assumption that attention of the surface wave is due only to radiation and not to dissipation in the surface material, the radiation coefficient is derived in terms of the attenuation factor. The excitation coefficient is determined by the reciprocity condition. Formulas for the shape and the spreading of the radiated wave are derived, and some sample calculations are presented. An investigation of resonant phase matching for nonseparable surfaces is presented with a sample calculation. A discussion of how such calculations might be related to resonant frequencies of nonseparable thin shell structures is included. A description is given of nonseparable surfaces that can be modeled in the vector that facilitates use of the appropriate formulas of differential geometry.

Barger, Raymond L.↗

NASA NTRS1992

Design and analysis of low boom concepts at Langley Research Center

The objective of the sonic boom research in the current High Speed Research Program is to ultimately make possible overland supersonic flight by a high speed civil transport. To accomplish this objective, it is felt that results in four areas must demonstrate that such a vehicle would be acceptable by the general public, by the airframers, and by the airlines. It should be demonstrated: (1) that some waveform shape has the possibility of being acceptable to the general public; (2) that the atmosphere would not totally destroy such a waveform during propagation; (3) that a viable airplane could be built which produces such a waveform; and (4) that any performance penalty suffered by a low boom aircraft would be counteracted by the economic benefit of overland supersonic flight. The work being done at LaRC is in support of the third element listed above--the area of configuration design. The initial part of the paper will give a review of the theory being used for configuration designs and discuss two theory validation models which were built and tested within the past two years. Discussion of the wind tunnel and theoretical results (linear theory and higher order methods) and their implications for future designs will be included.

Darden, Christine M.↗

NASA NTRS1992

Comparison of jet plume shape predictions and plume influence on sonic boom signature

An Euler shock-fitting marching code yields good agreement with semiempirically determined plume shapes, although the agreement decreases somewhat with increasing nozzle angle and the attendant increase in the nonisentropic nature of the flow. Some calculations for the low boom configuration with a simple engine indicated that, for flight at altitudes above 60,000 feet, the plume effect is dominant. This negates the advantages of a low boom design. At lower altitudes, plume effects are significant, but of the order that can be incorporated into the low boom design process.

Barger, Raymond L.↗

NASA NTRS1990

Fuselage design for a specified Mach-sliced area distribution

A procedure for designing a fuselage having a prescribed effective area distribution computed from -90 deg Mach slices is described. This type of calculation is an essential tool in designing a complete configuration with an effective area distribution that corresponds to a desired sonic boom signature shape. Sample calculations are given for M=2 and M=3 designs. The examples include fuselages constrained to have circular cross sections and fuselages having cross sections of arbitrary shape. It is found that, for a prescribed effective area distribution having sharp variations, the iterative procedure converges to a smoothed approximation to the prescribed distribution. For a smooth prescribed area distribution, the solution is not unique.

Barger, Raymond L.↗

NASA NTRS1989

A procedure for computing surface wave trajectories on an inhomogeneous surface

Equations are derived for computing surface waves on smooth surfaces, including surfaces with a nonuniform wave speed. The prior literature dealt primarily with the theoretical development with little consideration given to computational methods, and examples were limited to waves on surfaces of simple analytic description, such as cones, spheres, and cylinders. The computational procedure presented is a relatively general method. Sample calculations illustrate the procedure for a class of practical shapes of the type that include aerodynamic and hydrodynamic surfaces. Equations are also included for computing the spreading of rays into a surrounding medium that will support waves.

Barger, Raymond L.↗

NASA NTRS1989

Path-Following Solutions Of Nonlinear Equations

Report describes some path-following techniques for solution of nonlinear equations and compares with other methods. Use of multipurpose techniques applicable at more than one stage of path-following computation results in system relatively simple to understand, program, and use. Comparison of techniques with method of parametric differentiation (MPD) reveals definite advantages for path-following methods. Emphasis in investigation on multiuse techniques being applied at more than one stage of path-following computation. Incorporation of multipurpose techniques results in concise computer code relatively simple to use.

Barger, Raymond L.↗

NASA NTRS1988

Weak-wave analysis of shock interaction with a slipstream

A weak wave analysis of shock interaction with a slipstream is presented. The theory is compared to that for the acoustic case and to the exact nonlinear analysis. Sample calculations indicate that the weak wave theory yields a good approximation to the exact solution when the shock waves are sufficiently weak that the associated entropy increase is negligible. A qualitative discussion of the case of counterflowing streams is also included.

Barger, Raymond L.↗

NASA NTRS1988

A simplified approach to axisymmetric dual-reflector antenna design

A procedure is described for designing dual reflector antennas. The analysis is developed by taking each reflector to be the envelope of its tangent planes. Rather than specifying the phase distribution in the emitted beam, the slopes of the emitted rays were specified. Thus, both the output wave shape and angular distribution of intensity can be specified. Computed examples include variations from both Cassegrain and Gregorian systems, permitting deviation from uniform source distributions and from parallel beam property of conventional systems.

Barger, Raymond L.↗

NASA NTRS1988

A performance index approach to aerodynamic design with the use of analysis codes only

A method is described for designing an aerodynamic configuration for a specified performance vector, based on results from several similar, but not identical, trial configurations, each defined by a geometry parameter vector. The theory shows the method effective provided that: (1) the results for the trial configuration provide sufficient variation so that a linear combination of them approximates the specified performance; and (2) the difference between the performance vectors (including the specifed performance) are sufficiently small that the linearity assumption of sensitivity analysis applies to the differences. A computed example describes the design of a high supersonic Mach number missile wing body configuration based on results from a set of four trial configurations.

Barger, Raymond L.↗

NASA NTRS1987

On minimizing the number of calculations in design-by-analysis codes

A method is presented for aerodynamic design for a specified pressure distribution, using analysis codes only. The method requires a very conservative number of analysis runs, and therefore is appropriate when the analysis code is a large code in terms of storage and/or running time. Three model problems illustrate some capabilities and limitations of the method.

Barger, Raymond L.↗

NASA NTRS1961

Ionization and Deionization Processes in Low-Density Plasma Flows

Various plasma relaxation processes that are significant in laboratory plasma flows for aerospace physics studies are discussed on the basis of a survey of time decay studies of immobile plasmas. Some of the problems analyzed and discussed are: the relative importance of the various recombination mechanisms, catalytic deionization by electro- negative particles, delayed ionization produced by metastable action, and heating of the flow by deionization reactions.

Barger, Raymond L.↗

NASA NTRS1959

Boundary-Induced Downwash Due to Lift in a Two-Dimensional Slotted Wind Tunnel

A solution has been obtained for the complete tunnel-interference flow for a lifting vortex in a two-dimensional slotted tunnel. Curves are presented for the longitudinal distribution of tunnel-induced downwash angle for various values of the boundary openness parameter and for various heights of the vortex above the tunnel center line. Some quantitative discussion is given of the use of these results in calculating the tunnel interference for three-dimensional wings in rectangular tunnels with closed side walls and slotted top and bottom.

Katzoff, S.↗