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At least 199 records · Page 11

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DOE OSTI2025

A Novel Approach to Fast Calculation of High-Order Q-Cumulants

The method of Q-cumulants has been shown as a powerful tool to study the fine details of the azimuthal anisotropies in high-energy nucleus-nucleus collisions. A new method for the fast calculation of arbitrary order Q-cumulant $v_{n}\{2k\}$ values, based on the partition of a non-negative integer l $\le$ m for calculation of the 2m-particle azimuthal correlations is presented in this paper. Unlike the standard Q-cumulants method in which the calculation of high-order multi-particle calculations is impractical, the newly proposed method enables easy calculation. The validity of the method is proven via a toy model that uses the elliptic power distribution to simulate anisotropic emission of particles. The method enables the study of fine details of the $v_{2}$ distribution, such as higher-order central moments of the $v_{2}$ distribution, as well as the hydrodynamic behavior of the Quark-Gluon Plasma.

FOS: Physical sciences↗

NASA NTRS1974

Analysis and calculation of lightning-induced voltages in aircraft electrical circuits

Techniques to calculate the transfer functions relating lightning-induced voltages in aircraft electrical circuits to aircraft physical characteristics and lightning current parameters are discussed. The analytical work was carried out concurrently with an experimental program of measurements of lightning-induced voltages in the electrical circuits of an F89-J aircraft. A computer program, ETCAL, developed earlier to calculate resistive and inductive transfer functions is refined to account for skin effect, providing results more valid over a wider range of lightning waveshapes than formerly possible. A computer program, WING, is derived to calculate the resistive and inductive transfer functions between a basic aircraft wing and a circuit conductor inside it. Good agreement is obtained between transfer inductances calculated by WING and those reduced from measured data by ETCAL. This computer program shows promise of expansion to permit eventual calculation of potential lightning-induced voltages in electrical circuits of complete aircraft in the design stage.

Plumer, J. A.↗

NASA NTRS1973

Polarizability calculations on water, hydrogen, oxygen, and carbon dioxide

A semiclassical model of damped oscillators is used as a basis for the calculation of the dispersion of the refractive index, polarizability, and dielectric permeability in water, hydrogen, and oxygen in liquid and gaseous states, and in gaseous carbon dioxide. The absorption coefficient and the imaginary part of the refractive index are also calculated at corresponding wavelengths. A good agreement is obtained between the observed and calculated values of refractive indices, and between those of absorption coefficients in the region of absorption bands. The calculated values of oscillator strengths and damping factors are also discussed. The value of the polarizability of liquid water was about 2.8 times that of previous calculations.

Nir, S.↗

NASA NTRS1976

A submerged singularity method for calculating potential flow velocities at arbitrary near-field points

A discrete singularity method has been developed for calculating the potential flow around two-dimensional airfoils. The objective was to calculate velocities at any arbitrary point in the flow field, including points that approach the airfoil surface. That objective was achieved and is demonstrated here on a Joukowski airfoil. The method used combined vortices and sources ''submerged'' a small distance below the airfoil surface and incorporated a near-field subvortex technique developed earlier. When a velocity calculation point approached the airfoil surface, the number of discrete singularities effectively increased (but only locally) to keep the point just outside the error region of the submerged singularity discretization. The method could be extended to three dimensions, and should improve nonlinear methods, which calculate interference effects between multiple wings, and which include the effects of force-free trailing vortex sheets. The capability demonstrated here would extend the scope of such calculations to allow the close approach of wings and vortex sheets (or vortices).

Maskew, B.↗

NASA NTRS1977

Method of fan sound mode structure determination computer program user's manual: Modal calculation program

A computer user's manual describing the operation and the essential features of the Modal Calculation Program is presented. The modal Calculation Program calculates the amplitude and phase of modal structures by means of acoustic pressure measurements obtained from microphones placed at selected locations within the fan inlet duct. In addition, the Modal Calculation Program also calculates the first-order errors in the modal coefficients that are due to tolerances in microphone location coordinates and inaccuracies in the acoustic pressure measurements.

Pickett, G. F.↗

NASA NTRS1978

H-H, C-H, and C-C NMR spin-spin coupling constants calculated by the FP-INDO method for aromatic hydrocarbons

The FP-INDO (finite perturbation-intermediate neglect of differential overlap) method is used to calculate the H-H, C-H, and C-C coupling constants in hertz for molecules of six different benzenoid hydrocarbons: benzene, naphthalene, biphenyl, anthracene, phenanthrene, and pyrene. The calculations are based on both the actual and the average molecular geometries. It is found that only the actual molecular geometries can always yield the correct relative order of values for the H-H coupling constants. For the calculated C-C coupling constants, as for the calculated C-H coupling constants, the signs are positive (negative) for an odd (even) number of bonds connecting the two nuclei. Agreements between the calculated and experimental values of the coupling constants for all six molecules are comparable to those reported previously for other molecules.

Long, S. A. T.↗

NASA NTRS1980

Numerical calculations of the collapse of nonrotating, magnetic gas clouds

Results of the first self-consistent numerical calculations of the dynamic collapse of a magnetized protostellar gas cloud are presented. Symmetry about an axis parallel to the initial magnetic field direction has been assumed, so that the calculations could be performed on a two-dimensional grid. Also, the cloud was taken to be nonrotating and isothermal, and the magnetic field was assumed to remain frozen in to the gas. As starting models for the calculations, gas spheres with uniform density and magnetic field were used. The time evolution of the clouds has been calculated for roughly two initial free-fall times, at which point the central density has increased by a factor of approximately 10,000 to 1,000,000. Several such calculations have been performed for different values of the cloud's initial thermal, magnetic, and gravitational energies. In virtually all cases it is found that, once a flattened core forms in the cloud, the central magnetic field strength, B, varies with gas density, rho, according to (d log B/d log rho) = 1/2. This behavior is independent of the initial energy ratios mentioned above. It is also found that the magnetic field is able to prevent completely the collapse of part of the outer envelope of the cloud.

Scott, E. H.↗

NASA NTRS1980

Quasi-projection-operator calculation of autoionization states of O5/+/ /O VI/ and Si11/+/ /Si XII/

A practical approach to calculating diagnostic parameters includes both scattering and statelike (autoionization) elements. The paper presents inelastic quasi-projection-operator calculations of autoionization states of the three-electron ions of oxygen and silicon for states below the n = 3 manifod of the respective two-electron parent (O VI and Si XII). Wave functions containing up to 40 configurations are calculated. The O VI calculated results agree with experimental results within the experimental error (about + or - 2 eV) while for the Si XII case, it was necessary to include relativistic effects. Where formulas are available (states for which p + q = 2), the Si XII results are also in good agreement with experimental results for 2Se, 2Po, and 2De states. Since the calculated results for some of the higher states did not agree with identifications proposed by Trabert et al. (1979), alternative identifications are suggested.

Wakid, S.↗

NASA NTRS1982

Improved Venus ionopause altitude calculation and comparison with measurement

Improved approximations are incorporated into the inviscid fluid method originated by Spreiter et al (1970) in calculations of the altitude of the Venus ionopause. The altitude calculations are then compared with median altitudes measured by the Pioneer Venus retarding potential analyzer. The calculated ionopause shape is found to closely approximate the measured meridian shape in the solar zenith angle (SZA) range of zero-135 deg. The use of improved ionospheric pressure field ionosheath pressure and Prandtl-Meyer expansion approximations lowers the terminator ionopause altitude to approximately half that obtained with the usual Spreiter approximations. It is also determined that the calculated dawn ionopause is about 300 km higher than the dusk ionopause, and that both ionopauses are close to their respective measured meridian values. It is concluded that median ionopause altitude within the SZA angle range may be calculated without inclusion of a viscous interaction in the theory.

Knudsen, W. C.↗

NASA NTRS1982

Numerical calculation of the parameters of the efflux from a helium dewar used for cooling of heat shields in a satellite

The parameters of the efflux from a helium dewar in space were numerically calculated. The flow was modeled as a one dimensional compressible ideal gas with variable properties. The primary boundary conditions are flow with friction and flow with heat transfer and friction. Two PASCAL programs were developed to calculate the efflux parameters: EFFLUZD and EFFLUXM. EFFLUXD calculates the minimum mass flow for the given shield temperatures and shield heat inputs. It then calculates the pipe lengths, diameter, and fluid parameters which satisfy all boundary conditions. Since the diameter returned by EFFLUXD is only rarely of nominal size, EFFLUXM calculates the mass flow and shield heat exchange for given pipe lengths, diameter, and shield temperatures.

Brendley, K.↗

NASA NTRS1982

Analytical calculation of a single jet in crossflow and comparison with experiment

A series of calculations of a jet in crossflow using a three-dimensional finite difference model of the Navier-Stokes equations were made on a series of progressively finer grids. With a reasonable number of grid point (40x30x20), calculated jet penetration and mixing characteristics were found to compare favorably with the experimental measurements of Crabb, Durao and Whitelaw. The calculated results were grid dependent (i.e., numerical or false diffusion was present in the result). A finer grid calculation indicated that turbulence model deficiencies may become more noticeable in the calculated results as the magnitude of numerical diffusion is reduced.

Clauss, R. W.↗

NASA NTRS1985

Transonic calculations for a flexible supercritical wing and comparison with experiment

Pressure data measured on the flexible DAST ARW-2 wing are compared with results calculated using the transonic small perturbation code XTRAN3S. A brief description of the analysis is given and a recently-developed grid coordinate transformation is described. Calculations are presented for the rigid and flexible wing for Mach numbers from 0.60 to 0.90 and dynamic pressures from 0 to 1000 psf. Calculated and measured static pressures and wing deflections are compared, and calculated static aeroelastic trends are given. Attempts to calculate the transonic instability boundary of the wing are described.

Bennett, R. M.↗

NASA NTRS1985

Comparison of big event with calculations of the air shower development

The incidence of high energy hadrons and electron-photons in air showers at various stages of development is calculated. Numerical calculation is used to solve the diffusion equation for a nuclear cascade and analytical calculation for cascade shower induced gamma rays. From these calculations, one can get the longitudinal development of the high energy hadron and electron-photon components, and the energy spectra of these components at various depths of air shower development. The total number of hadrons (N sub H) and electron-photon components (N sub gamma) are related according to stages of the air shower development and primary energy. The relation of the total energy of hadron and electron-photon component above the threshold energy is given. The energy balance between both components is also a useful parameter to study high energy events accompanying air showers. The relation of N sub H and fractional hadronic energy E (sum E sub H sup gamma/sum E sub H sup gamma + Sum E sub gamma) is calculated. This relation is helpful to understand the stage of air shower development(t) and primary energy (E sub p).

Niwa, M.↗

NASA NTRS1985

Transonic calculations for a flexible supercritical wing and comparison with experiment

Pressure data measured on the flexible DAST ARW-2 wing are compared with results calculated using the transonic small perturbation code XTRAN3S. A brief description of the analysis is given and a recently developed grid coordinate transformation is described. Calculations are presented for the rigid and flexible wing for Mach numbers from 0.60 to 0.90 and dynamic pressures from 0 to 1000 psf. Calculated and measured static pressures and wing deflections are compared, and calculated static aeroelastic trends are given. Attempts to calculate the transonic instability boundary of the wing are described.

Bennett, R. M.↗

NASA NTRS1986

Thermodynamic Calculations for Complex Chemical Mixtures

General computer program, CECTRP, developed for calculation of thermodynamic properties of complex mixtures with option to calculate transport properties of these mixtures. Free-energy minimization technique used in equilibrium calculation. Rigorous equations used in transport calculations. Program calculates equilibrium compositions and corresponding thermodynamic and transport properties of mixtures. CECTRP accommodates up to 24 reactants, 20 elements, and 600 products, 400 of which are condensed. Written in FORTRAN IV for any large computer system.

Mcbride, B. J.↗

NASA NTRS1985

A Numerical Method of Calculating Propeller Noise Including Acoustic Nonlinear Effects

Using the transonic flow fields(s) generated by the NASPROP-E computer code for an eight blade SR3-series propeller, a theoretical method is investigated to calculate the total noise values and frequency content in the acoustic near and far field without using the Ffowcs Williams - Hawkings equation. The flow field is numerically generated using an implicit three dimensional Euler equation solver in weak conservation law form. Numerical damping is required by the differencing method for stability in three dimensions, and the influence of the damping on the calculated acoustic values is investigated. The acoustic near field is solved by integrating with respect to time the pressure oscillations induced at a stationary observer location. The acoustic far field is calculated from the near field primitive variables as generated by NASPROP-E computer code using a method involving a perturbation velocity potential as suggested by Hawkings in the calculation of the acoustic pressure time-history at a specified far field observed location. the methodologies described are valid for calculating total noise levels and are applicable to any propeller geometry for which a flow field solution is available.

Korkan, K. D.↗

NASA NTRS1986

Unsteady transonic flow calculations for wing-fuselage configurations

Unsteady transonic flow calculations are presented for wing-fuselage configurations. Calculations are performed by extending the XTRAN3S unsteady transonic small-disturbance code to allow the treatment of a fuselage. Details of the XTRAN3S fuselage modeling are discussed in the context of the small-disturbance equation. Transonic calculations are presented for three wing-fuselage configurations with leading edge sweep angles ranging from 0 deg to 46.76 deg. Simple bending and torsion modal oscillations of the wing are calculated. Sectional lift and moment coefficients for the wing-alone and wing-fuselage cases are compared and the effects of fuselage aerodynamic interference on the unsteady wing loading are revealed. Tabulated generalized aerodynamic forces used in flutter analyses, indicate small changes in the real in-phase component and as much as a 30% change in the imaginary component when the fuselage is included in the calculation. These changes result in a 2 to 5% increase in total magnitude and a several degree increase in phase.

Batina, J. T.↗

NASA NTRS1985

Calculation of recoil implantation profiles using known range statistics

A method has been developed to calculate the depth distribution of recoil atoms that result from ion implantation onto a substrate covered with a thin surface layer. The calculation includes first order recoils considering projected range straggles, and lateral straggles of recoils but neglecting lateral straggles of projectiles. Projectile range distributions at intermediate energies in the surface layer are deduced from look-up tables of known range statistics. A great saving of computing time and human effort is thus attained in comparison with existing procedures. The method is used to calculate recoil profiles of oxygen from implantation of arsenic through SiO2 and of nitrogen from implantation of phosphorus through Si3N4 films on silicon. The calculated recoil profiles are in good agreement with results obtained by other investigators using the Boltzmann transport equation and they also compare very well with available experimental results in the literature. The deviation between calculated and experimental results is discussed in relation to lateral straggles. From this discussion, a range of surface layer thickness for which the method applies is recommended.

Fung, C. D.↗