Coarse-grained molecular dynamics (CGMD) is a technique developed as a concurrent multiscale model that couples conventional molecular dynamics (MD) to a more coarse-grained description of the periphery. The coarse-grained regions are modeled on a mesh in a formulation that generalizes conventional finite element modeling (FEM) of continuum elasticity. CGMD is derived solely from the MD model, however, and has no continuum parameters. As a result, it provides a coupling that is smooth and provides control of errors that arise at the coupling between the atomistic and coarse-grained regions. In this article, we elaborate on the formulation of CGMD, describing in ... continued below
Coarse-grained molecular dynamics (CGMD) is a technique developed as a concurrent multiscale model that couples conventional molecular dynamics (MD) to a more coarse-grained description of the periphery. The coarse-grained regions are modeled on a mesh in a formulation that generalizes conventional finite element modeling (FEM) of continuum elasticity. CGMD is derived solely from the MD model, however, and has no continuum parameters. As a result, it provides a coupling that is smooth and provides control of errors that arise at the coupling between the atomistic and coarse-grained regions. In this article, we elaborate on the formulation of CGMD, describing in detail how CGMD is applied to anharmonic solids and finite temperature simulations. As tests of CGMD, we present in detail the calculation of the phonon spectra for solid argon and tantalum in 3D, demonstrating how CGMD provides a better description of the elastic waves than that provided by FEM. We also present elastic wave scattering calculations that show the elastic wave scattering is more benign in CGMD than FEM. We also discuss the dependence of scattering on the properties of the mesh. We introduce a rigid approximation to CGMD that eliminates internal relaxation, similar to the Quasicontinuum technique, and compare it to the full CGMD.
Description: Report presenting an investigation of the ejection release characteristics of the MB-1 rocket from the missile bay of a model of the Convair F-106A airplane with its fin tips retracted at a simulated altitude of 18,670 feet. Successful ejections of the rocket were made at supersonic speeds by applying a combination of ejection velocity and nose-down pitching moment at release.
Investigation of ejection release characteristics of four dynamically scaled internal-store shapes from a 1/17-scale simulated bomb bay of the Republic F-105 airplane at Mach numbers of 1.39 and 1.98
Description: Report presenting an investigation of the release characteristics of dynamically scaled stores carried internally in a simulated bomb bay at Mach numbers of 1.39 and 1.98. A model of the Republic F-105 half-fuselage and bomb-bay configuration was tested with four store shapes: the MK-7 store, the bluff store, the TX-28 store, and turnabout TX-28 store. Results regarding ejection photographs and data plots are also provided.
Description: Report presenting flight testing of a rocket-powered model of a cruciform canard missile configuration with a low-aspect-ratio wing and blunt nose. Results regarding the lift coefficient, dynamic stability, static stability, control effectiveness, and drag are provided.
Flight characteristics of a wingless rocket- powered model with four externally mounted air-to-air missiles at Mach numbers 0.7 to 1.6
Description: Report presenting a flight investigation of four air-to-air missiles mounted by pylons on a rocket-powered basic wingless buffet-research vehicle to determine the trim, buffet, and drag characteristics of the combination.
A flight and analog study of the effect of elevating the radar-boresight axis upon stability and tracking performance of an automatically controlled interceptor
Description: Report presenting flight and analog-simulator tests with a prototype automatic interceptor in order to study the effects of elevating the radar-boresight axis on the stability and tracking performance of the system. Results regarding effects of interceptor rolling motion upon tracking errors, similarity of flight results and analog-computer results, effect of elevating the radar-boresight axis upon stability, effect of elevating the radar-boresight axis upon the required bank-angle feedback, and application of the principle of elevated radar-boresight axis are provided.
Description: Report presenting a flight investigation of a rocket-launched solid-fuel ram-jet engine designed to bypass cooling air around the fuel charge. The internally cooled combustor averted combustor burn-out during the flight test. Results regarding the net thrust coefficient, gross thrust coefficient, time history of the air specific impulse, and total fuel load are provided.
Description: Report on an investigation to determine the erect and inverted spin and recovery characteristics of a model of the North American FJ-4 airplane. The testing found that either a flat-type of steep-type spin may be obtained when the airplane is spinning erect. The optimum recovery technique from inverted spins was full rudder reversal with simultaneous movement of the ailerons to full with the stick maintained full forward.
Description: Report discussing an investigation to determine the low-speed aerodynamic characteristics of a North American FJ-3 airplane with a segmented spoiler-slot-deflector lateral control system installed ahead of convention ailerons and operated as individual units and as combined segments. The longitudinal characteristics of the plane, the spoiler-slot-deflector effectiveness, and spoiler-deflector hinge-moment data are all described.
Description: Report presenting data to determine the component and overall engine performance up to an altitude limit for the J71-A-11 (600-B36) turbojet engine. Engine operation using JP-4 fuel at Mach number 0.8 was satisfactory up to an altitude of about 60,000 to 65,000 feet, and engine operation with marginal combustion stability was maintained to an altitude of about 80,000 feet. Results regarding the altitude operating limits, component performance, overall engine performance, contribution of individual component losses to overall engine performance losses, exhaust-nozzle-area requirements, and altitude performance at rated engine conditions are provided.
Description: Flutter characteristics of three low-aspect-ratio all-movable half-span control surfaces at Mach numbers from 1.49 to 2.87.
Description: Lithium hydride and magnesium as high temperature internal coolants with skin materials.
Description: The results of an investigation of several internal water-inertia-separation inlets consisting of a main duct and an alternate duct designed to prevent automatically the entrance of large quantities of water into a turbojet engine in icing conditions are presented. Total-pressure losses and icing characteristics for a direct-ram inlet and the inertia-separation inlets are compared at similar aerodynamic and simulated icing conditions. Complete ice protection for inlet guide vanes could not be achieved with the inertia-separation inlets investigated. Approximately 8 percent of the volume of water entering the nacelles remained. In the air passing into the compressor inlet. Heavy alternate-duct-elbow ice formations caused by secondary inertia separation resulted in rapid total-pressure losses and decreases in mass flow. The duration in an icing condition for an inertia-separation- inlet, without local surface heating, was increased approximately four times above that for a direct-ram inlet with a compressor-inlet screen. For normal nonicing operation, the inertia-separation- inlet total-pressure losses were comparable to a direct-ram installation. The pressure losses and the circumferential uniformity of the mass flow in all the inlets were relatively independent of angle of attack. Use of an inertia-separation inlet would in most cases require a larger diameter nacelle than a direct-ram inlet in order to obtain an alternate duct sufficiently large to pass the required engine air flow at duct Mach numbers below 1.0 at the minimum area.
Description: Report presenting an investigation to determine the effects of simulated engine nacelles and wing-root freedoms on the flutter characteristics of a cambered, modified, swept, tapered, semispan wing through a range of Mach numbers. Wings were tested with and without nacelles and with the model restrained, free to roll, and free to translate in the vertical direction. Results regarding the effect of nacelles, flutter boundary, and effect of wing-mount freedom are provided.
January 1,267 1267 February 1,037 1037 March 1,124 1124 April 1,174 1174 May 1,069 1069 June 1,159 1159 July 1,099 1099 August 1,150 1150 September 1,161 1161 October 1,080 1080 November 988 988 December 904 904