Engineering topics
Publications and source records attributed to Fung, Jimmy.
How do we want to consider computational performance? For instance, it tends to fall “between the cracks” of our communities. How have we considered it in the past? How do we avoid code-to-code comparisons, e.g. keep it internal but share lessons learned or ways to measure performance? How do we handle different types of codes, e.g. single-physics, multi-physics? How to consider this considering our plans to port to new machines?
The goal of this milestone is to demonstrate readiness of the Sandia Parallel Aerodynamics Reentry Code (SPARC) and the Electro-Magnetic Plasma in Realistic Environments (EMPIRE) code for use on the forthcoming El Capitan exascale platform, which will enable simulation of weapons-relevant problems at unprecedented scale and fidelity.
The goal of this milestone is to demonstrate readiness of LLNL Next-Generation simulation capability for use on the forthcoming El Capitan exascale platform, which will enable simulation of weapons-relevant problems at unprecedented scale and fidelity.
As displayed in the FY23 ASC Implementation Plan (IP) and the Milestone Reporting Tool (MRT), the milestone description and completion criteria state: Demonstrate the capability to execute mission-relevant calculations with a multiphysics code from the Ristra project at scale on the pre-El Capitan Early Access System 3 (EAS-3). These calculations must use the GPU hardware available on EAS-3, the AMD MI-250s, to achieve any reasonable performance.
This report describes the development of transfer function models for the trailing-edge and upper and lower spoiler actuators of the Benchmark Active Control Technology (BACT) wind tunnel model for application to control system analysis and design. A simple nonlinear least-squares parameter estimation approach is applied to determine transfer function parameters from frequency response data. Unconstrained quasi-Newton minimization of weighted frequency response error was employed to estimate the transfer function parameters. An analysis of the behavior of the actuators over time to assess the effects of wear and aerodynamic load by using the transfer function models is also presented. The frequency responses indicate consistent actuator behavior throughout the wind tunnel test and only slight degradation in effectiveness due to aerodynamic hinge loading. The resulting actuator models have been used in design, analysis, and simulation of controllers for the BACT to successfully suppress flutter over a wide range of conditions.
Recent studies of the micro-dynamic behavior of a deployable telescope metering truss have identified instabilities in the equilibrium shape of the truss in response to low-energy dynamic loading. Analyses indicate that these micro-dynamic instabilities arise from stick-slip friction within the truss joints (e.g., hinges and latches). The present study characterizes the low-magnitude quasi-static load cycle response of the precision revolute joints incorporated in the deployable telescope metering truss, and specifically, the hysteretic response of these joints caused by stick-slip friction within the joint. Detailed descriptions are presented of the test setup and data reduction algorithms, including discussions of data-error sources and data-filtering techniques. Test results are presented from thirteen specimens, and the effects of joint preload and manufacturing tolerances are investigated. Using a simplified model of stick-slip friction, a relationship is made between joint load-cycle behavior and micro-dynamic dimensional instabilities in the deployable telescope metering truss.