Waterhammer

Waterhammer, Acoustic Waves, and Other Fast Transients

Waterhammer is an impulse load created by sudden changes such as valve opening or closing. The resulting pressure loads can have catastrophic effects on pumps, pressure transducers, turbines, and valves. Waterhammer events typically occurs over a millisecond time frame, but may spand several seconds in large systems. The ability of SINDA/FLUINT and FloCAD® to capture fast transients allows the modeling of waterhammer and other fast transient events such as acoustic waves propagating through ducts that contain compressible and even two-phase fluids.

Historically, the Method of Characteristics (MOC) was often used to predict wave propagation phenomena, while FloCAD uses a finite difference/volume approach. What is the difference? FloCAD may be optionally used to model wave propagation events, while MOC-based software can't be used for much else. MOC is inapplicable to phenomena such as slow transients (much less steady states), heat transfer, two-phase flows with phase change, mixtures, etc.

Shown below is a comparison between FloCAD and a MOC solution, as documented in Wylie and Streeter's Fluid Transients (1982 edition, Example 3-1). The RMS error is about 1%: on the order of the interpolation error. To enable an "apples to apples" comparison, default FloCAD features had to be turned off such as the automatic inclusion of frictional losses, heating effects, heat transfer, fluid properties, etc.

Chart showing Comparison between FloCAD and a MOC solution

Other validations have included comparisons with column separation events … a flashing phenomenon not easily handled by MOC-based programs. In fact, SINDA/FLUINT is capable of full two-fluid nonhomogeneous phasic nonequilibrium analysis if needed. What does that mean? It means FloCAD is the only commercial off-the-shelf program that is capable of modeling waterhammer and similar oscillations and instabilities in two-phase multiple-component flows.

FloCAD's implicit solution techniques enable it to take large time steps, and the availability of simplifying assumptions means that FloCAD is just as applicable to parametric sweeps of steady-state heat exchanger performance as it is to simulating detailed waterhammer events. In other words, FloCAD doesn't have to concentrate on higher order effects like fast transients. But such capabilities are there if needed.

FloCAD online training

Class times: May 2 & 4 from 10am to 2pm MT

Cost: $425

This online class will provide an introduction to fluid modeling components within FloCAD. The class will be held over a 2-day period, with daily sessions running approximately 4 hours each. The class uses a mixture of lecture, demonstrations, and self-paced tutorials to allow attendees to practice building fluid system models and interpreting results. The presentations will comprise 2 - 3 hours of each session, and the instructor will be available during the remainder of the time for questions during tutorials. Attendees must have basic working knowledge of SINDA and Thermal Desktop as these topics will not be covered but their usage is required for FloCAD.

Register here

Thermal Desktop, RadCAD, and TD Direct in-class training

Date: April 25-28, 2017, 8:00 a.m. to 5:00 p.m., daily
Location: Lakewood, CO

CRTech will be hosting introductory training for Thermal Desktop, RadCAD and TD Direct. Lecture and hands-on tutorials introduce attendees to basic Thermal Desktop and RadCAD usage and allow practice building models and interpreting results. The class will also introduce students to SpaceClaim direct modeling CAD interface and advanced meshing tools in TD Direct.

Daily Schedule

Day 1 and 2: Introduction to SINDA and Thermal Desktop
Day 3: Introduction to RadCAD
Day 4: Introduction to TD Direct
 

To learn more about this class and to register, visit our Training Page.

Anode and cathode of a flow battery

Using Sinaps? It is not too soon to get started with TD/FloCAD!

This webinar describes the process for converting from Sinaps to Thermal Desktop (TD) and FloCAD. This process includes using an exporter which works with Version 6.0 of the CRTech tool suite (expected to be released in May of 2017).

Come learn about the basics of TD/FloCAD, including many compelling features not available in Sinaps. The webinar will also cover how to manage the transition period, during which you may be using both programs simultaneously. This is also a chance to ask questions. 

If you missed this webinar, please contact us for the presentation material and recording.