Table of Contents
Flow types and fluid modelling
What about multiphase flow?
BOSfluids is primarily aimed at single-phase flow conditions, with three exceptions: it can handle the formation and collapse of vapour cavities (cavitation); it can simulate the flashing of liquids in tube rupture scenarios; and it has a sophisticated model for simulating the rapid flooding of empty (fire water) systems. This model handles two-phase flow conditions in which the fluid-liquid interface is perpendicular to the pipe axis. It does not handle general two-phase flow conditions or phase transitions. More information about this model is available in this publication.
Is BOSfluids suitable for cryogenic systems?
Yes, as long as phase transitions and/or multiphase flow conditions are not significant. Cavitation can be handled (with limitations).
Can BOSfluids model slurries with the new non-Newtonian liquid model?
Yes.
Where do fluid properties come from, particularly bulk modulus, and can users override them?
There is a built-in database with liquid properties. You can also specify your own as a function of temperature.
How are drag reducing agents modelled, and what inputs are needed?
The simplest option is to specify a constant drag reduction factor. You can also specify the drag reduction factor as a function of the Reynolds number.
Can you show a filter model setting?
BOSfluids does not have dedicated filter elements, but you can most probably use an Equipment element instead. This element type enables you to specify an arbitrary relation between the flow rate and the pressure drop. You could, for instance, specify a linear relation between the pressure drop and flow rate to model certain types of filters. In this case you only need to know the pressure drop at some specific flow rate through the filter.
What can BOSfluids do for water infrastructure?
What do you need? BOSfluids can do a lot.
Thermal analysis and tube rupture
How does the steady state thermal analysis handle trapped liquid thermal expansion?
It does not and cannot, because it calculates only a steady state solution; for a trapped liquid a pressure needs to be specified.
How is heat loss handled at valves, flange pairs, etc.? Is it applied as in ISO 12241 or have you used an internal model?
The thermal solver in BOSfluids assumes that pressure losses within valves and similar non-pipe elements are converted into heat. It further assumes that there is no heat transfer between these kinds of elements and their surroundings; these elements are viewed as being “lumped” (no length) by the thermal solver.
Does the gas flow through inline restrictions model capture the Joule-Thomson effect?
Yes, in two ways. The steady state thermal solver accounts for the J-T effect. The tube rupture model in BOSfluids also accounts for the J-T effect.
Can BOSfluids model a shell and tube heat exchanger tube rupture?
Yes, absolutely. It implements a tube rupture model that supports flashing and the Joule-Thomson effect. I have very recently used it in an engineering consulting project.
Pumps, compressors and valves
Can BOSfluids model positive displacement pumps (screw pumps, reciprocating pumps)? If yes, what input data is required?
BOSfluids features dedicated element types for reciprocating pumps and compressors. They essentially require you to specify the piston geometry: diameter, crank shaft radius, connecting rod length, and clearance volume. You can use periodic flow boundary conditions to model screw compressors.
In pump sizing calculations, is it possible to calculate the required minimum circulation flow rate, which is normally provided by the vendor?
The latest BOSfluids version provides support for pump sizing scenarios. That is, you can determine the required operating point and the system curve with little effort.
Can BOSfluids simulate pump start-up into a line that is not fully filled?
This might be possible with the Flood & Drain model, but there are some limitations (no general multiphase flow conditions).
Can you walk through a complete pump study?
No, there is no time for that. But I can demonstrate how to analyse various types of pump-related scenarios.
Can BOSfluids model the transient effects of a PSV valve operation (pop action)?
Yes, BOSfluids provides a dedicated Relief Valve element type that can be used to simulate the operation of a wide range of pressure safety valves. This element type enables you to simulate in a detailed way how the relief valve (PSV) opens and closes.
How does BOSfluids model a HIPPS closure and its effect on the upstream system?
In the same way as it would handle a surge event. I would love to set up a private demo for you.
Acoustic and flow-induced vibration (AIV/FIV)
Acoustic and flow-induced vibration (AIV/FIV)
BOSfluids uses the NORSOK or Energy Institute Guidelines to perform an AIV assessment. There is no step-by-step guidance; you create a model and let BOSfluids handle the rest.
How does the AIV assessment to Energy Institute / NORSOK work, from input to likelihood of failure result?
The starting point is a piping model for which the steady state conditions can be computed. Then, for each valve and orifice in the model, a sound power level is calculated. The EI calculation rules are applied to determine how noise propagates through the model. At the specified locations, a likelihood of failure is calculated from the sound power level at that location.
Once an AIV risk is identified, what mitigation options does the assessment point to?
The assessment currently does not include suggestions for mitigating measures. You could reduce noise by changing flow rates and/or pressure drops.
Model import, interfaces and BOSpulse
Can isometric data be imported via PCF or a similar format?
Yes, absolutely. BOSfluids has an excellent PCF import interface.
I have hydraulic models prepared in AFT Fathom; what is the most convenient way to transfer them into BOSfluids? Can models be transferred at all?
BOSfluids can import piping models from various file formats, but, unfortunately, AFT is not amongst them. BOSfluids can import Piping Component Files (generated by an increasing number of 3-D modelling and CAD applications), CAESAR II, Bentley AutoPIPE, PIPENET, EPANET, and some more.
Can BOSfluids exchange models with CAESAR II or PRG tools, and how are transient loads (e.g. elbow-to-elbow force pairs) extracted for a static stress model or support design?
This is one of the strongest points of BOSfluids. BOSfluids is one of the best solutions for combined flow and stress analyses because it can deal with 3-D piping models. It has a bi-directional interface with CAESAR II.
How do BOSfluids and BOSpulse work together, and which tool covers which study?
BOSfluids focuses on steady state and general transient flow conditions. BOSpulse focuses on periodic flow conditions. They are fully compatible with each other.
Large models and run times
Is it possible to do detailed modelling at full isometric level for a complex system surge analysis?
This is absolutely possible in BOSfluids. In fact, we do that all the time in our surge projects. The Piping Component File interface in BOSfluids enables you to pull in detailed piping models from various 3-D modelling and CAD applications. BOSfluids can easily deal with thousands and even tens of thousands of elements in a single model. The transient solver applies a so-called grid coarsening technique (described in this publication) to dramatically shorten calculation times for large and complex piping models.
What is the typical run time for a complex system?
The transient flow solver in BOSfluids implements some algorithms (explained in this publication) that reduce calculation times by one or even two orders of magnitude. As an example, consider a large model we have used in a past surge analysis (pump trip). This model consists of about 12,000 (pipe) elements, ranging from 100 mm to 600 m in length. Running a transient analysis requires about 4 seconds of compute time for each simulated (real-world) second. That is, it runs only four times slower than in real time.