Special Coverage

Home

Large Eddy Simulation Composition Equations for Two-Phase Fully Multicomponent Turbulent Flows

The composition probability density function moment variables are based on a new type of filter. NASA’s Jet Propulsion Laboratory, Pasadena, California Liquid sprays are commonly used to inject fuels into combustion devices, making it important to study multicomponent (MC) two-phase flows in order to reveal their physics. “Multicomponent” is the terminology describing all fuels that are combinations of a myriad of species. Single-component simulations lack a detailed representation of the complex composition and reaction mechanisms of realistic fuels, which can contain hundreds to thousands of species. Some species may be responsible for fuel ignition, other species may be the initiators of soot formation, and yet others may be involved in surface corrosion, all of which demonstrates the importance of being able to track the multitude of species.

Posted in: Information Sciences, Electronics & Computers, Briefs

Read More >>

Scheduling Targeted and Mapping Observations with State, Resource, and Timing Constraints

NASA’s Jet Propulsion Laboratory, Pasadena, California This innovation creates observations of both targeted geographical regions of interest and general mapping observations, while respecting spacecraft constraints such as data volume, observation timing, visibility, lighting, season, and science priorities. This tool, therefore, addresses both geometric and state/timing/resource constraints by using a grid-based approach. These set covering constraints are then incorporated into a greedy optimization scheduling algorithm that incorporates operations constraints to generate feasible schedules. The resultant tool generates schedules of hundreds of observations per week out of potentially thousands of observations.

Posted in: Information Sciences, Electronics & Computers, Briefs, TSP

Read More >>

Safety Analysis of Conflict Prevention Algorithms

This algorithm provides guidance maneuvers to avoid conflict in air traffic management systems. Langley Research Center, Hampton, Virginia Different types of information are used to help aircraft maintain separation standards. At the lowest level, information is needed to indicate if separation standards will be violated in the near future, called a conflict. Once a conflict is detected, then conflict resolution information may be used to create a new path in which there is no conflict. Most future airspace concepts propose using computer algorithms to produce this information. Both conflict detection and resolution algorithms usually work in a pair-wise fashion: the ownership aircraft and one other aircraft. In situations where traffic density is low, this pair-wise assumption does not significantly impact operations. However, when traffic density is high, resolving one conflict may result in new near-term conflicts called secondary conflicts. These secondary conflicts may be nearer (in time) than the original conflict being addressed, so, the safety of the aircraft depends on avoiding these conflicts.

Posted in: Information Sciences, Electronics & Computers, Briefs, TSP

Read More >>

CT-CURS: Unwrapping/Re-slicing Software for Cylindrical Objects Inspected Using Computed Tomography

This method provides 10¥ greater ability to resolve flaws in cylindrical CT data. John H. Glenn Research Center, Cleveland, Ohio Ultra-thin-wall metallic cylinders are extremely difficult to analyze for flaws from top-view X-ray computed tomography (CT) slices and volume renderings. A protocol has been developed using software to unwrap and re-slice the ultra-thinwall cylinder CT data into 2D sheets from the exterior to the interior of the cylinder. This method is based on interior and exterior surface edge detection, and under proper conditions, is fully automated and requires no input from the user except proper voxel dimension from the CT experiment and wall thickness of the part. By performing this transformation to a series of 2D sheets, and utilizing a local contrast expansion method in which each sheet is automatically contrast expanded between its minimum and maximum gray values, the flaws “pop out” at the inspector. This software has allowed NASA to extend the in-house world-class micro-computed tomography method for 10x better flaw resolution for cylindrical structures.

Posted in: Information Sciences, Electronics & Computers, Briefs

Read More >>

Trajectory Specification for High-Capacity Air Traffic Control

Automating separation monitoring and guidance would relieve human controllers of the primary responsibility for safe separation. The doubling or tripling of airspace capacity that will be needed over the next several decades will require that tactical separation guidance be automated for appropriately equipped aircraft in high-density airspace. Four-dimensional (4D) trajectory assignment (three-dimensional position as a function of time) will facilitate such automation. A standard trajectory specification format based on XML (Extensible Markup Language) is proposed for that purpose.

Posted in: Electronics & Computers, Test & Measurement, Briefs, TSP

Read More >>

Co-Optimized, Blunt-Body Re-entry Vehicle Design Process

A document describes a design optimization method for determining optimal shapes for vehicles with mid-range lift-to-drag ratios that are entering or re-entering planetary atmospheres. The design space includes consideration of hypersonic aerothermodynamic properties (for minimizing heating) and hypersonic aerodynamic properties (for maximizing maneuverability and stability). It allows for flexible trajectory design. The method allows geometry and analysis grids (meshes) to be rapidly created from a limited set of parameters, which once defined, can be interpreted in a straightforward and intuitive manner.

Posted in: Electronics & Computers, Briefs, TSP

Read More >>

Adaptive Periodic-Correlation Algorithm for Shack-Hartmann Wavefront Sensing

Conventional Shack-Hartmann Wavefront Sensing requires a point source such as a star to perform wavefront sensing. This software allows one to conduct such sensing using an extended-scene or scene-based image. The software allows a Shack-Hartmann Wavefront Sensor (SH-WFS) to be used with an extended scene. It estimates the shift between the positions of a reference and test extended-scene sub-images or cells.

Posted in: Information Sciences, Electronics & Computers, Sensors, Briefs, TSP

Read More >>