AFT Blog
Scuba divers and casual swimmers alike are all too familiar with the discomfort (and sometimes outright pain) experienced in their ears as they descend deeper into the water. This discomfort is experienced for good reason: for each 33 feet you descend into the water, you experience considerably more pressure (about 1 whole atmosphere) due to the hydrostatic pressure of the water. As the pressure of the surrounding water increases, the air trapped in the middle ear remains at atmospheric pressure, but the pressure in the outer ear is significantly higher, which puts significant force on the eardrum. Anyone who has ever...
If you are performing a hydraulic analysis on your fire system, chances are high that you are working hard and maybe scratching your head in order to adhere to the NFPA codes. The good news is that you can streamline the calculations outlined in the codes with AFT Fathom! NFPA 15 is the standard for fixed water spray systems that are used in fire protection. AFT Fathom has been able to perform all the standard hydraulic calculations for a fire protection analysis for a long time, including the usage of Hazen-Williams factors. But now with AFT Fathom 9, you can easily...
One of the most common causes of waterhammer in pipelines is a valve closure. As the valve closes, the flowing liquid is forced to stop, resulting in a transfer of kinetic energy to potential energy, which ultimately causes a pressure increase. If this increase in pressure is large enough, extremely severe damage can result in the pipeline. Engineers frequently mitigate this waterhammer by selecting a valve that closes slowly enough to prevent the pressures from getting too high. However, a valve that closes too slowly can cause problems elsewhere in the pipeline or result in other undesirable outcomes in the process....
One of the new features in AFT Fathom 9 was the ability to model equivalent lengths instead of K factors for various types of fittings. Since AFT Fathom's existence, the standard K factor loss models have been used to quantify the pressure losses across a fitting such as an elbow, a valve, etc. One of the reasons why the K factor method is very useful is because it is broad and applicable to a wide range of different fittings. However, the equivalent length method is also a way that engineers will typically quantify the losses through their fittings and they will...
The process of sizing a pump for the application of priming a piping system as well as for normal operation is slightly more involved than if the system was already primed and the pump was to be sized for a liquid full system. For a system priming application, the intermediate elevations at high points in a piping system are relevant in regard to the pump that is used. If a pump is not able to generate enough head in order to overcome the high intermediate elevation points in a system, then the pump will provide no benefit to the system, even...
When evaluating the hydraulic behavior of aged pipelines and/or pipelines that are exposed to particularly corrosive or dirty fluids, building and running a hydraulic model is a great first step, but more engineering may be required. This is because, over time, residue in the pipeline fluid can buildup in the pipeline and essentially decrease the pipe inner diameter while increasing the roughness of the pipe’s inner surface. Corrosion can also change the roughness of the pipe’s inner surface. Engineers know that these changes due to buildup and corrosion in the pipes can significantly affect the hydraulics of the system, so while building a hydraulic model of the system is essential to evaluate its behavior, calibrating the model to account for these changes can be just as important in getting an accurate representation of your system. AFT Fathom and AFT Arrow offer a goal seeking module to assist with this calibration process with one data set of flow data. To understand how this can be done, visit Dylan’s blog. My blog here will take Dylan’s discussion one step further and discuss how AFT Fathom and AFT Arrow can be used to calibrate a hydraulic model with not just one but with multiple data sets using the GSC (Goal Seek and Control) module.
Previously, we talked about the Graph Guide and how to create Stacked Graphs. Another way to see the interactions between parameters is to show them on one graph with dual Y-axes and a common X-axis scale. I am going to again start with the AFT Impulse model, ‘Pump Startup With Event Transient.imp’, which is installed in the Examples folder, and use the ‘One Pump Start With One Running’ scenario. In the previous blog, we used a Stacked Graph to examine the pressures and flows at two valves (J6 and J9), which opened during the simulation. This time, we will put them...