Cart3D Simulations for the Second AIAA Sonic Boom Prediction Workshop

Simulation results are presented for all test cases prescribed in the Second AIAA Sonic Boom Prediction Workshop. For each of the four nearfield test cases, we compute pressure signatures at specified distances and off-track angles, using an inviscid, embedded-boundary Cartesian-mesh flow solver with output-based mesh adaptation. The cases range in complexity from an axisymmetric body to a full low-boom aircraft configuration with a powered nacelle. For efficiency, boom carpets are decomposed into sets of independent meshes and computed in parallel. This also facilitates the use of more effective meshing strategies - each off-track angle is computed on a mesh with good azimuthal alignment, higher aspect ratio cells, and more tailored adaptation. The nearfield signatures generally exhibit good convergence with mesh refinement. We introduce a local error estimation procedure to highlight regions of the signatures most sensitive to mesh refinement. Results are also presented for the two propagation test cases, which investigate the effects of atmospheric profiles on ground noise. Propagation is handled with an augmented Burgers' equation method (NASA's sBOOM), and ground noise metrics are computed with LCASB

Numerical Simulation of Bolide Entry with Ground Footprint Prediction

As they decelerate through the atmosphere, meteors deposit mass, momentum and energy into the surrounding air at tremendous rates. Trauma from the entry of such bolides produces strong blast waves that can propagate hundreds of kilometers and cause substantial terrestrial damage even when no ground impact occurs. We present a new simulation technique for airburst blast prediction using a fully-conservative, Cartesian mesh, finite-volume solver and investigate the ability of this method to model far- field propagation over hundreds of kilometers. The work develops mathematical models for the deposition of mass, momentum and energy into the atmosphere and presents verification and validation through canonical problems and the comparison of surface overpressures, and blast arrival times with actual results in the literature for known bolides. The discussion also examines the effects of various approximations to the physics of bolide entry that can substantially decrease the computational expense of these simulations. We present parametric studies to quantify the influence of entry-angle, burst-height and other parameters on the ground footprint of the airburst, and these values are related to predictions from analytic and handbook-methods

CR-SUBMANIFOLDS OF SASAKIAN MANIFOLDS

ABSTRACT: Recently, K.Yano and M.Ko

Necessary and sufficient conditions for eventually vanishing oscillatory solutions of functional equations with small delays

Necessary and sufficient conditions are found for all oscillatory solutions of the equation (rn−1(t)(rn−2(t)(−−−(r2(t)(r1(t)y′(t)))−−−)))+a(t)h(y(g(t)))=b(t) to approach zero. Sufficient conditions are also given to ensure that all solutions of this equation are unbounded

Description of a design method for cryogenic concrete tanks based on a comparison between 2D and 3D numerical models

-Ammonia is used in the industry for the manufacture of fertilizers, explosives and polymers and is stored at -33°C in refrigerated tanks. In most cases, tanks are cylindrical and are composed of a steel liner that contains the ammonia, with the liner itself being protected by an outer reinforced concrete tanks. The function of the concrete tank is to keep the ammonia safe in case of a leak in the liner. If a leak happens, the concrete wall will be suddenly subjected to a thermal shock, with a large temperature gradient between its internal and external faces (20°C to -33°C). These thermal effects lead to cracks in concrete that allow the ammonia to escape. The junctions between walls and the base slab and, walls and the roof are particularly sensitive to this cracking phenomemon. The aim of this paper is to present a method for the design of concrete ammonia tanks, especially taking into account thermal effects. Firstly, a 2D finite element model based on a plane frame is developed. The advantage of this approach, compared to 3D modeling, is that it requires little computing power and engineering time. Then, a 3D model is used to validate the 2D approach, and to identify it