Contributed by Jonathan Binns
BMW Oracle Racing
Trying to sell potential customers on the benefits of complex multi-hole probe technology would be nearly impossible without being able to provide a first-hand demonstration of the probe’s capability to generate quality data. For Aeroprobe Corp., that’s where Tecplot Focus software comes into the picture. The Blacksburg, VA-based manufacturer of multi-hole probe instrumentation uses Tecplot Focus visualization software to prove its products’ capabilities to prospective customers.
Seeking Answers to Probing Questions
Aeroprobe specializes in the manufacturing, calibration and application of multi-hole probe technology and provides measurement technology to the aerodynamic and fluid dynamic testing communities. Multi-hole probe systems are based on the acquisition of the probe’s port pressures. The test pressures are then compared against a probe calibration map, which was generated in the company’s laboratories.
This comparison is performed by Aeroprobe’s pressure-to-velocity reduction software Multiprobe™, which returns the total and static pressures at the probe tip, as well as the two flow angles required to compute the 3D velocity. With the aid of 2D or 3D traversing systems, the user can map out planes or volumes of the test flow, conceivably generating thousands of data points, with possibly dozens of variables at each point.
Although the company also conducts research for the Air Force Research Laboratories and other government agencies through the SBIR program, this plot was generated for a commercial customer using Tecplot to visualize their probe data. Tecplot is used in these applications to visualize data generated when traversing scales are employed to automatically move the probe and generate 2D planes or 3D volumes of probe data.
Assessing Flow Quality of Intake Manifolds
In this particular case, one of Aeroprobe’s customers was interested in the flow quality through a set of automotive intake manifolds they had designed. To determine the flow quality of the manifolds, the team looked at three components of velocity, plus the total and static pressure located on 18 separate planes. These planes of data were acquired with three different manifolds of circular cross-section, each with a different internal vane structure. The manifolds took the input flow and turned it horizontally through a bend of 135°. The manifolds were identical except for the design of the internal vanes.
Manifold 1 had no internal vane structure. Manifold 2 had a vane that was oriented vertically and horizontally centered in the manifold. Manifold 3 had a manifold of a more complex design, the idea being that it would perform better than Manifold 2. Two indications of better performance was that the static pressure was as constant as possible over the cross-section of the flow, ensuring that each combustion cylinder would receive similar volumes of air at similar pressure, and the existence of vortical structures that would enhance the mixing of air and fuel.
Multiple planes were acquired, with the z = 0 location at the outlet plane of the manifold, positive z outside of the manifold and along the axis of the manifold. The images represent a comparison of the performance of these manifolds. (Note: only the results for manifolds 1 and 3 were included to keep the data as concise as possible).
Automatically traversing a seven-hole probe and acquiring pressure data from the probe ports at the data points is indicated on the plots generated by the data. The data in the 18 planes were each acquired separately, so that multiple data acquisition procedures were required. The resulting pressure data was reduced to total and static pressure, velocity magnitude and flow angles using Multiprobe™. The velocity components (u, v and w) were then calculated.
Plotting a Way to Better Flow Quality
The plot was created by importing the planar data into Tecplot and performing a triangulation on the data using the software’s triangulation tool. Once the data was triangulated, the contour plots of w (z-component of velocity), Pt (total pressure) and Ps (static pressure) were generated, with the velocity vectors overlayed on the color contours.
For proper comparison, it was important that the color contours and the velocity vectors have consistent levels and lengths throughout the plots. For this reason, the style of the plots (using Tecplot Stylesheets) were maintained and new data sets loaded, which made it easier to make consistent plots much faster, says Matthew D. Zeiger, senior scientist and CEO of Aeroprobe Corp.
The results indicated that Manifold 3 was the most effective at producing a more consistent static pressure (Ps) across the outlet plane (Z0 plots), while also producing in-plane vortical flows to enhance mixing. “It also showed to our customer that the Aeroprobes could be used to generate good data in their application,” adds Zeiger. “As a direct result of this demonstration, the customer decided to purchase a system to investigate further the capability of the Aeroprobes as a flow diagnostic tool.”
Tecplot is the Visualization Tool of Choice at Aeroprobe
Zeiger believes that Tecplot is an essential tool for the company to employ when demonstrating the capabilities of its high-tech probes to prospective customers. “The idea is that we can show that the probe is generating quality data, and we can use Tecplot to generate very nice plots that give the customer an indication of what they can expect to achieve by using the probe,” says Zeiger. “In some cases, our customers are using the probe experiments to compare with CFD data, and Tecplot facilitates the comparison.”
Tecplot Focus is also used at the company to visualize some of its internal data sets, which are used to determine if a probe/system is working properly, or in some cases to benchmark the probe data.
For several years, Aeroprobe developed and sold its own data visualization package. “However,” Zeiger adds, “it became obvious that we were not going to keep up with Tecplot’s capabilities even if we expended a large amount of time and money in further development of this internal code.”
Aeroprobe also sells Tecplot as part of the multi-hole probe system packages. Many Aeroprobe customers currently use Tecplot to analyze multi-hole probe data from varied applications such as wakes of automobiles and aircraft and recirculating flows in spray dryers.
Among Tecplot’s greatest strengths, Zeiger believes, is its ability to save the layout and input new data, which results in identical levels, axes, etc. with different data. “This feature allows us to set the layout and style and move quickly through a data set in comparison of many different planes of data.” Zeiger also credits the software’s ability to work with 1D, 2D and 3D sets, especially large data sets with many variables as well as its flexibility in accepting data that facilitates the programming of data acquisition and reduction codes to quickly and easily write to data files that can be imported into Tecplot.
Getting the job done at Aeropobe would prove difficult without the use of Tecplot Focus software. “We would still be able to generate the data, but without Tecplot, we would be hard-pressed to generate visualizations of the data that would be effective in showing our customers the capabilities of the Aeroprobes,” says Zeiger.