CFD software’s success with flush

CAD-integrated computational fluid dynamics (CFD) software from Flomerics saved time in the design of an innovative flush valve

Johnson Design’s Denali Flushometer flush valve delivers a fixed volume of water independent of the position of the restriction on the rolling diaphragm which is randomly installed at various positions during the valve assembly.
Engineering manager Dustin Borg used EFD.Lab to evaluate the performance of the valve as the restriction was rotated 360º, in order to ensure that it delivered the right amount of water in each position.
“It reduced the time required to optimise the design by enabling us to evaluate design concepts in software without having to build a prototype,” Borg said.
Flush valves take advantage of pressure differentials between the inlet and control chambers. The pilot valve, when engaged by the handle, vents the control chamber – lowering its pressure and allowing the rolling diaphragm to open, which begins the flush cycle. Rolling diaphragms expose only a small area of unsupported diaphragm to pressure differentials, resulting in much lower forces.
“But it’s usually not possible to determine in advance where the restriction on the rolling diaphragm will end after the valve is assembled,” Borg said. “One valve of the same model may deliver 1.5 gallons while another will deliver 1.7 gallons. We decided to overcome this problem in the Denali Flushometer by evening out the pressure that the valve is exposed to around its entire circumference.”
This would have been difficult using physical prototyping, as it would have meant repeated assembly and disassembly of the valve, each time slightly changing the position of the rolling diaphragm.
“EFD.Lab automatically distinguished between the solid and empty spaces in our CAD model and meshed the empty regions to prepare for flow analysis,” said Borg.

Virtual testing on engines
GM Powertrain, part of General Motors, has used Algor’s FEA software to diagnose the operation of an automotive electrical conductor.
Staff project engineer Ed Billings oversaw an experiment to test the conductor, which is part of a proprietary automotive sub-assembly. GM Powertrain engineers modelled the conductor in Algor and then ran virtual tests to determine the stresses resulting from forces exerted during a moulding process.
Billings frequently uses Algor software when designing and analysing GM parts.
“It helps to discriminate between design flaws and manufacturing flaws,” he said.
He also uses it when considering new designs or concepts— to determine assembly stresses, functional stresses and changes in seals, bores and gaskets, under given temperature changes.

Three degrees of enhancement
CFD software supplier Fluent has made three new releases, which it says will improve CAD interoperability and enhance mesh generation.
TGrid 4.0, Gambit 2.3 and 3Matic-for-Fluent 1.0 are all major upgrades to Fluent's pre-processing capabilities. They provide new functionality allowing users to go from CAD geometries to Fluent CFD solvers more quickly.
A powerful Surface Wrapper, added to TGrid4.0, allows users to wrap up multiple geometry files from several sources into single, high-quality surface mesh. It has reduced meshing times for applications in the automotive, aerospace and biomedical industries.
The 3Matic-for-Fluent software from Materialise is a complementary conditioning module for converting hundreds of files from mixed geometry sources into an optimal triangular meshing format for TGrid 4.0's new Surface Wrapper. This cleanup process
ensures that each CAD part is fully connected, of minimal size, and with sufficient resolution to capture the underlying geometrical details.
Finally, a new set of CAD readers in Gambit 2.3 allows users to bring native geometry into Gambit more effectively. Geometry operations like clean-up, construction, design modification and decomposition now work directly on all geometric representations.
“Every user of Fluent's pre-processing software will benefit from these new releases,” said Ferit Boysan, vice president and general manager of the fluids business unit at Ansys – Fluent’s parent company.

Tom Shelley

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