Extraction and Visualization of Swirl and Tumble Motion from Engine Simulation Data

Abstract

Summary. An optimal combustion process within an engine block is central to the performance of many motorized vehicles. Associated with this process are two important patterns of flow: swirl and tumble motion, which optimize the mixing of fluid within each of an engine's cylinders. Good visualizations are necessary to analyze these in-cylinder flows. The simulation data associated with in-cylinder tumble motion within a gas engine, given on an unstructured, time-varying and adaptive resolution CFD grid, demands robust visualization methods that apply to unsteady flow. We present a range of methods including integral, feature-based, and image-based schemes with the goal of extracting and visualizing these two important patterns of motion. We place a strong emphasis on automatic and semi-automatic methods, including topological analysis, that require little or no user input. We make effective use of animation to visualize the time-dependent simulation data and describe the challenges and some of the implementation measures necessary in an application of the presented methods to unstructured, time-varying and volumetric grids.

Interactive cross-detector analysis of vortical flow data

“…In this application evaluation we continue work done by Garth et al [8] and Laramee et al [15] where the regions of turbulence behind the gaskets were not considered. Computational fluid dynamics software is used to inspect and improve the design process and we know that engineers invest large amounts of time to optimize the geometry of cooling jackets.…”

Using Visualization to Debug Visualization Software

“…For example, we implemented a streamline tracing algorithm on boundary meshes from CFD [3,9] (as in Figure 1). This type of algorithm poses challenges because the meshes are unstructured and adaptive resolution.…”

“…The algorithm uses an adaptive resolution space-partitioning octree where internal nodes store the minimum and maximum data values of their children. The difficult aspect of this error was that it only occurred at data resolutions of 128 3 or greater (and not at 64 3 or smaller). To track down the error, we implemented a simple, generic, error-checking procedure that examined: (1) locations of triangle vertices-testing to see if they fell outside of their associated cube and (2) the maximum and minimum data values of each node in the octree to ensure that all child values fell within this range.…”

Asymmetric Tensor Analysis for Flow Visualization

“…In the southern hemisphere ð r ¼ sin ' < 0Þ, the values of the dual-eigenvectors are swapped. Consequently, the major dual-eigenvector field J 1 is discontinuous across curves where ' ¼ 0, which correspond to pure symmetric tensors (11) that form the boundaries between regions of counterclockwise rotations and regions of clockwise rotations.…”

“…Achieving this ideal motion results in an optimal mixing of air and fuel and, thus, a more efficient combustion process. A number of vector field visualization techniques have been applied to a simulated flow inside the diesel engine [23], [11], [4]. These techniques include arrow plots, color-coding velocity, textures, streamlines, vector field topology, and tracing particles.…”