Dynamic solutions for a fluid world™

As an AFT Applications Engineer, Erin helps to troubleshoot customer models, teaches seminars that train customers to use AFT software, and develops content to enhance users' understanding of the software. She previously worked as an engineering consultant at Performance Associates Inernational and Purple Mountain Technology Group. Erin is a certif...ied Engineer in Training and holds a Bachelor of Science in Chemical and Biochemical Engineering (2012) from Colorado School of Mines. More
Erin Onat

Pulsation Frequency Analysis Takes a New Turn

In recent years, engineering efforts have been increasingly focused on analyzing and preventing detrimental pulsations in pipelines. One major source of these pulsations is caused by acoustical resonance. Undesirable acoustical resonance happens when pressure pulses (the source of which is often a positive displacement pump) excite the system's nat...
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Erin Onat

Let the Heat Flow: Modeling Heat Transfer in Pipes in AFT Fathom and AFT Arrow

Among the many talents of AFT Fathom and AFT Arrow software is the ability to model heat transfer. While a major source of heat transfer is heat exchangers , this blog will address heat transfer that occurs in pipes. First, for the basics: Just what is heat transfer? Well, heat transfer occurs when there is a temperature difference between two objects at different temperatures. As all engineers know, the common theme of physics is that matter and energy alike travel spontaneously from higher, more chaotic surroundings to calmer, lower energy situations (not unlike the stereotypical engineer), and heat transfer is...
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Erin Onat

Are you for real? Understanding and Troubleshooting Artificial Transients in AFT Impulse

Around this time of year with Thanksgiving just around the corner, I always reflect on the truly endless list of things I am so grateful for. While this list is by no means exhaustive, some of these things include my loved ones, my awesome job at AFT, the bounty of pumpkin-flavored treats that sweeten up my fall-time snacking options, and of course, AFT Impulse’s detection of artificial transients. While the dreaded Warning message that an artificial transient triggers can cause any engineer’s stomach to turn, I’ll explain why every AFT Impulse user should add this feature to his/her list of...
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Recent Comments
alen
Thank you Erin for drawing our attention to this issue. One thing that I miss here is HOW to resolve the issue. How to specificall... Read More
Tuesday, 14 November 2017 09:52
Erin Onat
Thank you for taking the time to read my blog and to give me some feedback! The model discussed in this blog involves a somewhat... Read More
Friday, 01 December 2017 01:40
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Erin Onat

Closing the Loop on Modeling Closed Loop Systems in AFT software

For several users of AFT software , it goes pretty predictably: first you place a pressure junction, then maybe a pump, then some sources of pressure drop including valves and heat exchangers, and then the model is finished off with another pressure junction. Of course, this is greatly oversimplifying the process and the vast array of systems that are modeled with AFT software, but here’s my point: most users are more familiar with modeling open systems that include individual pressure junctions located both upstream and downstream of the system. But what about modeling closed systems? The truth is that modeling...
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Kevin
Really nice article! This greatly simplifies the thought process around closed systems. I think it's worth noting that the absol... Read More
Monday, 18 September 2017 22:05
Erin Onat
Kevin, The clarification you pointed out is vital, and I have updated my post to be more explicit about this point. Thank you for... Read More
Tuesday, 19 September 2017 16:54
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Erin Onat

Inherent vs. Installed Control Valve Curves and How They Relate to AFT Software

As tech support engineers, we sometimes receive questions from users confused about what control valve characteristic curve (inherent or installed) they are inputting into AFT Fathom , AFT Arrow , or AFT Impulse . The inherent control valve characteristic curve plots the valve open percent versus the percent of maximum Cv. This curve is true regardless of the system effects on the valve. The installed control valve characteristic curve plots the valve open percent versus the flow through the valve, and this plot is dependent on the conditions specific to the system. For example, if the control valve flow setpoint...
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Erin Onat

Give me some details about Detailed Tees!

Frequently in tech support, when a difficult-to-converge model comes in, one of the first things we check is whether or not any tees in the model are being modeled as detailed tees. The reason for this is that the hydraulic calculations involving detailed tees can be complex due to the interdependence between velocity and pressure loss for each pipe connected to the tee. Iteration must, therefore, be performed to find a pressure loss and flow through each connecting pipe that agrees with the rest of the flow and pressure solutions in the model. This begs the question, then, what calculations...
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Erin Onat

Combining Pipes in AFT Impulse to Decrease Model Run Times: How Resistance Curves Are Merged into Pipes to Increase Pipe Section Length

They say that time is of the essence, and as engineers, that couldn’t ring truer! AFT pipe flow software is there to help engineers save time by more safely, efficiently, and rapidly designing and analyzing their piping systems. AFT Impulse , Applied Flow Technology’s waterhammer tool, helps engineers analyze transient incompressible flow behavior that can cause potentially detrimental pressure surges. It uses the Method of Characteristics, which requires the pipes to be sectioned using a Characteristic Grid. In this Characteristic Grid, all of the pipes are broken into an integer number of section lengths, and pressure waves are assumed to...
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Ajay
Hi Erin, This method really helps to reduce the runtime of model but in some model like the one which i have with me has few small... Read More
Friday, 05 May 2017 06:37
Erin Onat
Hi Devendra, Thank you very much for your comment, and I'm very glad that you have found this blog useful. There is no way to ig... Read More
Monday, 08 May 2017 17:25
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