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John serves on the development team as a Senior Engineering Software Developer, teaches several training classes a year and assists in consulting projects as needed. He previously worked for Siemens Building Technologies as an automation system specialist/engineer and American GFM as a design engineer and lead mechanical/electrical engineer in...

John serves on the development team as a Senior Engineering Software Developer, teaches several training classes a year and assists in consulting projects as needed. He previously worked for Siemens Building Technologies as an automation system specialist/engineer and American GFM as a design engineer and lead mechanical/electrical engineer in support of research projects. John holds a Bachelor of Science in Mechanical Engineering (2004) from Old Dominion University.

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John Rockey

Benefits of the Discrete Gas Cavity Model

AFT Impulse 5 now includes a second cavitation model option: The Discrete Gas cavity Model (DGCM). So, what is it and how is it different from the existing cavitation model? This article will provide a very high level overview. The method of characteristics (the finite difference basis for 1D transient flow modeling) assumes a constant wave speed for each pipe, from time step to time step. There are, however, many things that would cause a change in wave speed; cavitation being one the most significant. A change in wave speed will have a dramatic effect on the pressure spike that occurs...
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Recent Comments
Guest — aqeel
what is actually meaning of this statement ***CRITICAL WARNING*** The following pipes have vapor volumes in computing stations gr... Read More
Tuesday, 15 August 2017 09:49
John Rockey
Hi Aqeel, AFT Impulse allows vapor cavity sizes to grow and shrink as is dictated by the system hydraulics, meaning that there is ... Read More
Thursday, 17 August 2017 16:41
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John Rockey

Show Junction Locations

One of the many new features in AFT Impulse 5 is the ability to show junction locations in profile plots. This can be enormously helpful when analyzing large, complicated systems. When enabled, all junction locations are identified by a vertical bar with a junction ID flag at the top. To show junction locations, click on the button in the toolbar.Show Junction Locations will also work for animations.
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Recent Comments
Guest — Kishore Ravindran
HI We are using AFT fathom Version 8, in my company for process piping calculations. We often face a problem of getting negative v... Read More
Friday, 27 June 2014 03:56
John Rockey
Hi Kishore, Your question does not appear to be related to the "Show Junction Locations" topic. Please email your question to Supp... Read More
Friday, 27 June 2014 21:10
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John Rockey

Model Specialty Valves Accurately with AFT Impulse 5

Applied Flow Technology is proud to release a new version of AFT Impulse, now at version 5. AFT Impulse 5 encapsulates all of the new interface and navigational enhancements from AFT Fathom 8, as well as a considerable breadth of new and improved technical features. One such feature is our newly enhanced Relief Valve Junction. A relief valve can still be modeled as Internal, Exit, or Inline Exit, but we now offer four unique opening/closing profiles as well. With these new profiles, you can now directly model many specialty valves which were previously difficult to model accurately! Another very useful enhancement...
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John Rockey

Exhaustive Tolerance Criteria

AFT Arrow uses Newton iteration to find a simultaneous solution for all junction pressures. Well, maybe not all junctions. When “Use Exhaustive Tolerance Criteria” is NOT selected, AFT Arrow will only check junction pressures that find their way into the solution matrix. The AFT Arrow solver builds a matrix of equations based on the number of flow splits in the model. Each flow split must have a common pressure that is consistent with the flow and pressure drop in all of the connected pipes. Finding the right pressure for each flow split can become rather tricky. To find the pressure using...
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John Rockey

Default Model Input

The ability to specify default input parameters is a feature that is common to all AFT software products. Diameter, Friction Model, and Design Factors can be specified by default for pipes. Input properties for Junctions are specific to each junction type, so the only common default property is elevation. The default input options are found in “Parameter and Unit Preferences”. In general, this feature makes model building faster and more efficient. The user should, however, be aware of how this affects the “Status” of pipes and junctions. The “Status”, to which I am referring, is the green light to run the...
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John Rockey

Balance Energy At Junction … What?

AFT Fathom has the ability to model heat transfer. The default mode (found in system properties) is “Constant Fluid Properties”. To avoid confusion in the default mode, several of the heat transfer input fields and option boxes are invisible or disabled until one of the following heat transfer modes are employed:  Heat Transfer With Energy Balance (Single Fluid)Heat Transfer With Energy Balance (Multiple Fluids) Upon selecting one of these heat transfer modes, the user may notice an option box labeled “Balance Energy at Junction”; found at the lower left of the first tab in the properties window for the Assigned Pressure...
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John Rockey

Annotation Images

One of the many new features in Fathom 8 is the ability to show images in the annotation box. This simple feature will allow the engineer to easily and clearly communicate a vast array of information through the Workspace and Visual Report.   To add an image to the Workspace or Visual Report, as seen above, select the Annotation tool from the toolbox. Then select the “Line/Arrow/Image” tab and specify the file path to your image. Once the image is selected, click OK. The image box shown on the workspace can be easily moved and resized.
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