7,995 research outputs found
An implicit method for the calculation of inlet flow fields
Inlet flow fields are calculated by an implicit, time marching procedure to solve the thin layer Navier-Stokes equations formulated in body fitted coordinates. Because the method can be used for a flow field with both subsonic and supersonic regions, it is applicable to subcritical as well as supercritical inlet operation. Results are presented and discussed for an inlet of current design practice. Results include inviscid calculations performed for supercritical inlet operation with uniform and nonuniform inflow boundary conditions as well as for subcritical inlet operation with uniform inflow boundary conditions. Results for viscous calculations performed for supercritical inlet operation with uniform inflow boundary conditions are also discussed
Calculation of two-dimensional inlet flow fields by an implicit method including viscous effects: User's manual
Inlet flow fields for airbreathing missiles are calculated by the adaptation of a two dimensional computational method developed for the flow around airfoils. A supersonic free stream is assumed to allow the forebody calculation to be uncoupled from the inlet calculation. The inlet calculation employs an implicit, time marching finite difference procedure to solve the thin layer Navier-Stokes equations formulated in body fitted coordinates. The mathematical formulation of the problem and the solution algorithm are given. Numerical stability and accuracy as well as the initial and boundary conditions used are discussed. Instructions for program use and operation along with the overall program logic are also given
A supersonic three-dimensional code for flow over blunt bodies: Program documentation and test cases
The use of a computer code for the calculation of steady, supersonic, three dimensional, inviscid flow over blunt bodies is illustrated. Input and output are given and explained for two cases: a pointed code of 20 deg half angle at 15 deg angle of attack in a free stream with M sub infinite = 7, and a cone-ogive-cylinder at 10 deg angle of attack with M sub infinite = 2.86. A source listing of the computer code is provided
Calculation of two-dimensional inlet flow fields in a supersonic free stream by an implicit marching code with nonorthogonal mesh generation: User's manual
An implicit, shock-capturing finite-difference code which is used to calculate two-dimensional inlet flow fields in a supersonic free stream is explained. The Euler equations are subjected to general nonorthogonal transformation and a body-fitted coordinate system is employed. The mathematical formulation of the problem is given along with the numerical algorithm. Initial and boundary conditions, numerical stability, program limitations, and accuracy is discussed. An overall program logic as well as instructions for program use and operation are also furnished
Calculation of two-dimensional inlet flow fields in a supersonic free stream: Program documentation and test cases
The use of a computer code for the calculation of two dimensional inlet flow fields in a supersonic free stream and a nonorthogonal mesh-generation code are illustrated by specific examples. Input, output, and program operation and use are given and explained for the case of supercritical inlet operation at a subdesign Mach number (M Mach free stream = 2.09) for an isentropic-compression, drooped-cowl inlet. Source listings of the computer codes are also provided
Time-Symmetrized Kustaanheimo-Stiefel Regularization
In this paper we describe a new algorithm for the long-term numerical
integration of the two-body problem, in which two particles interact under a
Newtonian gravitational potential. Although analytical solutions exist in the
unperturbed and weakly perturbed cases, numerical integration is necessary in
situations where the perturbation is relatively strong. Kustaanheimo--Stiefel
(KS) regularization is widely used to remove the singularity in the equations
of motion, making it possible to integrate orbits having very high
eccentricity. However, even with KS regularization, long-term integration is
difficult, simply because the required accuracy is usually very high. We
present a new time-integration algorithm which has no secular error in either
the binding energy or the eccentricity, while allowing variable stepsize. The
basic approach is to take a time-symmetric algorithm, then apply an implicit
criterion for the stepsize to ensure strict time reversibility. We describe the
algorithm in detail and present the results of numerical tests involving
long-term integration of binaries and hierarchical triples. In all cases
studied, we found no systematic error in either the energy or the angular
momentum. We also found that its calculation cost does not become higher than
those of existing algorithms. By contrast, the stabilization technique, which
has been widely used in the field of collisional stellar dynamics, conserves
energy very well but does not conserve angular momentum.Comment: figures are available at http://grape.c.u-tokyo.ac.jp/~funato/; To
appear in Astronomical Journal (July, 1996
Experimental demonstration of a measurement-based realisation of a quantum channel
We introduce and experimentally demonstrate a method for realising a quantum
channel using the measurement-based model. Using a photonic setup and modifying
the bases of single-qubit measurements on a four-qubit entangled cluster state,
representative channels are realised for the case of a single qubit in the form
of amplitude and phase damping channels. The experimental results match the
theoretical model well, demonstrating the successful performance of the
channels. We also show how other types of quantum channels can be realised
using our approach. This work highlights the potential of the measurement-based
model for realising quantum channels which may serve as building blocks for
simulations of realistic open quantum systems.Comment: 8 pages, 4 figure
A study of prediction methods for the high angle-of-attack aerodynamics of straight wings and fighter aircraft
Work is described dealing with two areas which are dominated by the nonlinear effects of vortex flows. The first area concerns the stall/spin characteristics of a general aviation wing with a modified leading edge. The second area concerns the high-angle-of-attack characteristics of high performance military aircraft. For each area, the governing phenomena are described as identified with the aid of existing experimental data. Existing analytical methods are reviewed, and the most promising method for each area used to perform some preliminary calculations. Based on these results, the strengths and weaknesses of the methods are defined, and research programs recommended to improve the methods as a result of better understanding of the flow mechanisms involved
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