AFT Blog
Welcome to the Applied Flow Technology Blog where you will find the latest news and training on how to use AFT Fathom, AFT Arrow, AFT Impulse, AFT xStream and other AFT software products.
When Should You Use Variable Pipe Resistance?
Have you ever finished running an AFT Impulse model and then received the following Warning message shown in Figure 1 and then wondered what it means? During a waterhammer analysis, the flowrates are constantly changing all throughout the system, therefore, the velocities and Reynold's numbers are also constantly changing. The friction factor
What Does “Head (HGL)” Mean for Submerged Pumps and Exit Pressures?
In AFT Fathom and AFT Impulse, it is possible to model a submerged pump where a short and possibly frictionless suction pipe for the pump’s inlet does not need to be modeled. When modeling a submerged pump, there are two options available for specifying the system inlet boundary condition at the pump suction. As shown in Figure 1 below,
When to Begin? Time and Events in Transient Studies
To define any transient event in AFT Impulse or AFT Fathom XTS the application must know when it begins. To do so, the user should know how time and event logic is approached in AFT’s transient solvers. In this article, we will discuss the three different time bases used in the applications, the selection of a single or repeating event, and the man
Start your engines! Modeling an Inertial Pump Startup
There are many (six!) ways to define a pump transient event in AFT Impulse. This gives you great flexibility in creating a model that behaves the way you want it to. One thing true for all pumps is that they must be started at least once. Pump startups often cause significant transient effects on the system so you may wish to model this with AFT Im
Hurricanes and the Art of Computer Modeling
Especially in Irma’s case, there was considerable discussion of the computer modeling used to predict the path and strength of the hurricane. As I have worked in computer modeling for most of my 30+ year career, this piqued my interest and I decided to educate myself a little more on the topic as it relates to hurricanes. The first resource I purs
Shhhh! Suppressing Sound Waves From Rocket and Space Shuttle Engines
The peak flow rate on the Space Shuttle deluge system was 900,000 gpm (200,000 m3/hr). That is not a typo! For reliability, the entire system is gravity driven from a 290 ft (88 m) tower. See photo below. Below, photo I took in 2013 of Space Shuttle Launch Complex 39 with Deluge System Tower at right AFT video which shows NASA Space Shuttle laun
What is Pogo and Why On Earth Would Anyone Want To Suppress It?
How did I end up getting assigned this project? Well, I had a few things going for me at that stage of my career. Firstly was that my company division was on a massive hiring spree. Since I had been hired three years earlier my division had doubled in size. Fortuitously for me, that meant I was now in the upper 50% of seniority. Secondly, I had ju
How a Russian Hydraulics Handbook Gained the Respect of the American Nuclear Industry
In that we used Idelchik at both of my first two jobs, when I started AFT in 1993 I assumed that everyone knew about and used Idelchik. I found out that was not the case. If you have not heard of Idelchik's handbook, it is voluminous at 861 pages. It has by far the best information available on how to calculate pressure losses in tees and wyes. An
Liquids And Gases And Slurries, Oh My!
AFT software graphic Tip: If you know how to use AFT Fathom, then you are over the learning curve by about 90%when it comes to knowing how to use AFT Arrow, and about 80% of how to use AFT Impulse. One of the best advantages to AFT software tools is they offer a full solution for any single-phase pipe flow analysis calculations.Whether you
Intermediate Elevations and Splitting Pipes
Hello AFT readers! It has been quite a while since I have written a blog for you all. I had a recent discussion with a user and discovered a couple pain points that may be common. We did not have any blogs on the topics yet and I figured it was time to get back in the game and write another blog for our readers! The pain points were: 1. Modeling sy
Did you know that New Jersey is a barrier in Spain?
It is true. New Jersey is a barrier in Spain. I saw it with my own eyes. Bear with me and I will explain. When I travel internationally I find the people, cultural and language differences fascinating. Last month I was fascinated once again. My blog last month was written while on an airplane as I travelled to Europe (see my July blog When Pipe Str
Powerful Tools for Power Generation
Establishing and maintaining an electrical grid is a monumental task spanning many professions and disciplines. Fluid dynamics plays an important role in nearly any method of power generation. Between ensuring safety, reliable production of power, and minimizing operational costs, there are countless ways that modeling fluid flow can
6 Reasons Why Flow Analysis is Necessary
To all of the engineers reading this article, we made it! Whew! Reading a three-part series is like running a marathon. Way to go!If you are new to this series, we encourage you to read this article as well as the previous two: Part 1: Six Reasons to Use a Flow Analysis and Part 2: Flow Analysis Is Neglected. In this article are six reasons en
You Should Combine Your Pipes
One of the many powerful features in AFT Impulse is the ability to calculate transient forces during a waterhammer/surge event (See "Evaluating Dynamic Loads in Piping Systems Caused by Waterhammer" white paper). The resulting transient forces can be exported into a pipe stress analysis software. Pipe stress analysis care about what the trans
A Space Shuttle Trifecta Achieved Today
It was not intentional. The Trifecta I mean. It just sort of happened organically. But now that I have completed it, I think it is kind of cool.There are three Space Shuttles that have flown into space and are now in American museums:Discovery - in the Smithsonian Air & Space Museum in Chantilly, Virginia (near Washington D.C. f
Waterhammer: In our Booth?
What booth and why does it have waterhammer? Come find out! In a few weeks, AFT and yours truly will be at the Turbomachinery and Pump Symposia (TPS) in Houston – September 10-12 to be precise. We will have a booth (#2824 for those who are coming). And we will have waterhammer. Not just waterhammer software. We have that every year and, as in previ
Making Sense of xT – Valve Loss in Compressible Flow
Almost every piping system has valves, and an accurate solution requires accurate valve losses. For incompressible systems, this is relatively straightforward. What happens when we introduce the complexities of compressible flow? Valve Sizing Equation in Incompressible Flow In liquid flow - like that calculated by AFT Fathom or AFT Im
It’s a New Decade, Baby – Let’s Go Solve Some Problems!
Happy New Year and Happy New Decade to all of you around the globe! As engineers, our society depends on us to help solve problems and make everyone's lives better. To provide power, water and heat are the basics. To provide transportation and communication are now critical technologies. Plus lots more.The unfortunate truth is that in solving the p
The Modern World, Technology, Social Distancing and Pandemics
Like most of you, I have no expert advice to give related to the current worldwide pandemic caused by COVID-19 – also known as the Coronavirus. Thus, I won't presume to offer advice or wisdom on that topic. But everyone is talking about, reacting to and being affected by the pandemic. It seems almost insensitive to not acknowledge that.As the Presi
Q&A: Calculating Transient Forces for Pipe Stress Analysis
In June 2020, AFT's Reinaldo Pinto presented the webinar Calculating Transient Forces for Pipe Stress Analysis. The webinar focused on generating unbalanced forces due to surge in AFT Impulse and exporting them to CAESAR-II. During the webinar, 28 questions were asked. Below are the responses. Download the presentation: www.aft.com/w
Secret Variable-g Feature in AFT Software? Yep, and It is Now Visible to All
When I wrote AFT Impulse 1 back in 1996, I slipped in an undocumented feature to make it capable of modeling the first waterhammer project I did in industry. Since then, this feature had a secret (i.e., undocumented) way of being enabled. AFT Impulse 8 will be released any day, and we have finally made this feature accessible to all. In the User Op
AFT Arrow is 25 Years Old…and Still Going Strong
As the original developer of AFT Arrow, I consider it as one of my babies. This month it is all grown up and now 25 years old. Back in March we came out with the latest new version AFT Arrow 8 – just as the COVID-19 crisis was emerging.Those who have taken an AFT Arrow seminar which I have taught (at least fifty classes and counting!) have likely h
Pump Geeks from a Century Ago - von Kármán and Knapp
Flow going backwards through a pump? Then the pump starts rotating in reverse? Where the heck is the check valve to stop the flow? These are all great questions (which I will answer later in this article).Theodore von Kármán and Robert Knapp were working on these questions in the early 1930's. Most engineering students encounter von Kármán in their
Digital Twin – Identical or Fraternal?
When I was a child, I was jealous of twins. I thought how cool it would be to have a twin. I had twin cousins a few years older than I was that I saw on a frequent basis. I always got them confused. Which one was Roger, and which one was Ronny?A buzzword floating around recently is "digital twin". Sounds cool. What is it? According to a webinar by
Nuclear Power to the Rescue!
My High School Physics Teacher When I was in high school (four decades ago!) I had an awesome physics teacher in my junior year, Mr. Kindred. His class was a key influence in my decision to pursue a career in mechanical engineering.I recall Mr. Kindred discussing the future of fusion power and commenting, as was common at that time, that "fusion p
What Is Transient Analysis?
You're tasked to perform a transient analysis of a piping system and it would be really helpful if there was a good software tool out there to help you. Well, you've come to the right place because AFT has great solutions! But our first question is, "What kind of transient analysis are you trying to do?" You might s
Calling All Waterhammer Experts – We Need You On This New Committee!
As you know, AFT is a developer of a world leading waterhammer simulation tool in AFT Impulse. We regularly get asked for waterhammer guidance by engineers tasked with building piping systems. While there are some excellent waterhammer resources available, there is not much decision-making content from non-commercial authoritative organizations. Th
Is there steam on your (Microsoft) Windows? How ASME Steam Tables came to be.
In the modern world there are many things we take for granted – especially in first-world countries. Among them are the reliable availability of water and electricity. To our homes. To our workplaces. Just about everywhere.Engineers also take things for granted. One of those is reliable data on the properties of steam and water. But it was not alwa
Russia, War and Big Changes for Liquified Natural Gas (LNG)
Wow, have things changed a lot in the last two months! Russia's unprovoked attack on Ukraine in February has literally changed the world. Our hearts and prayers go out to the Ukrainian people who are experiencing unimaginable suffering. Tens of thousands of people have died and many more have had their lives upended. Now two months later Sweden and
Don't throw a fit over your Fitting K Factors - Part 1: Fittings & Losses in AFT Fathom
AFT Fathom, AFT Arrow, AFT Impulse, and AFT xStream all have a tab in the Pipe Properties window called "Fittings & Losses" which allows users to quickly specify K factors for components within a pipeline such as valves, elbows, and area changes. The Fittings & Losses allow you to simplify your model and avoid workspace clutter by int
Would Newton Approve of How You Use His Law?
Improve Safety & Accuracy in Pipe Force Predictions ASME B31 piping code requires engineers to consider loads on pipes from waterhammer, steam hammer and other fluid transients. In principle, this means using Newton's Second Law which he published over three centuries ago. In 1687 to be specific. And in Latin if you want to read it in it
Restore Your Sanity, and Your Corrupted Model Files
Users occasionally contact AFT saying they have lost their model files or cannot open them. Can you imagine spending hours, days, or months building models, and all of a sudden, the progress and work is gone?! If it happens right before a deadline, the engineer will most likely have a minor panic attack, and feelings of anger, depression, or hopele
When Waterhammer Makes Things Explode
Last month I presented a technical paper that was both the easiest and the hardest paper I have written. The paper was on a waterhammer accident in 2016 at an alumina refinery which caused a slurry pump to catastrophically fail. The pump casing exploded and the hot, caustic slurry it was pumping sprayed onto a technician nearby resulting in severe
My Recent Visit With Newton and Galileo
I suspect Europeans who live near world history sites just accept this as normal. For a backwater American like me, it is amazing to come across the final resting places of Isaac Newton and Galileo. I recently had that privilege in London and Florence. On my 60th birthday in early April, I had the privilege of visiting Westminster Abbey. Among the
AFT Arrow & AFT xStream New Features Coming Soon
We recently discussed the new features coming out in AFT Fathom 13 and AFT Impulse 10. Now let's talk about the compressible gas and steam side of the product launches. You may be more familiar with AFT Fathom, as it is our flagship incompressible steady state analysis product. AFT Arrow is its counterpart for compressible steady sta
Awesome Annotation Tool Additions
The Annotation Tool has new shapes and customization options which will help you organize, markup, comment, and effectively present your models when using the new versions of Fathom 13, Arrow 10, Impulse 10, and xStream 3. In addition to the pre-existing rectangles and ellipses, you can now add diamonds, pentagons, hexagons, octagons, clouds, trian
Pause and Resume Lengthy Transient Simulations Using Checkpoint Files
Much can be done to reduce model run times, but it's a fact of life with transient simulations that some systems are just large and complex, need to cover longer spans of time, or have dynamics that can only be accurately captured with finer sectioning. In such cases, long run times can be unavoidable.Have you ever needed to pause a lengthy si
Capture Complex Settling Slurry Behavior With the 4-Component Slurry Model
The Settling Slurry Module (SSL) for AFT Fathom and AFT Impulse has long been used to model complex systems with settling slurries in a range of industries. Previously all slurry models were variations of the Wilson, Addie, Clift method requiring differing levels of user input to use. The release of AFT Fathom 13 and AFT Impulse 10 has brought with
How Pipe Flow Analysis Enhances Chemical Processing
Do you really understand what's happening throughout your chemical processing system? In all applications, but especially with chemical processing, it's important to understand how your system is behaving and to ensure the requirements for the system, including temperature, environmental influences, pressure, flow, etc. are met.AFT addresses pipe f
10 New Features Coming to Datacor Pipe Flow Modeling Software in 2025
Releasing June 30, 2025, Datacor's latest upgrade delivers powerful enhancements across its Pipe Flow Modeling Software suite—Fathom, Arrow, Impulse, and xStream. Designed to accelerate workflows, improve model accuracy, and provide deeper engineering insight, these new features span everything from smart automation to cross-application integratio