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Extreme is in the eye of the beholder

July 01, 2014
KEYWORDS flow / fluid dynamics
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Attend a fluid dynamics seminar on extreme flows and the topics covered might include things like distorted turbulent shear layers, shock-wave boundary layer interaction, high Reynolds number wall turbulence, biometric flows, instrumentation and sports dynamics.

We don’t go into that kind of technology specialization in this our annual supplement on flow technology, but the editorial features in the issue do discuss commercial flow technology at low temperatures and low flows, and for large line sizes and other relevant production parameters .

Further, if you take a step back and look at the bigger picture, you might agree that the process industries are among the biggest players most impacted by what could be characterized as an era defined by the most extreme flows.

Look at it this way: The thing about today’s extreme sports is that instead of patient dedication to the joining of mind and body through the practice and performance associated with baseball, basketball and tennis, it’s all about taking on more and more risk in the hope of out-sized rewards in the form of big bucks and media attention.  

Also, google “extreme flows” and you’ll form the impression that the most extreme flows involve investment capital scurrying around the globe voraciously seeking security and profit.

These same extreme risk-reward management relationships that we see in capital markets and among today’s youth is also evident as oil & gas company giants master petroleum flows from difficult-of-access unconventional oils, whether from shale, light tight oil formations, deepwater subsea, under salt domes or other.

The U. S. Energy Information Administration’s most recent Short-Term Energy Outlook predicts natural gas output this year will increase four percent from 2013, setting a record for the fourth straight year to 73 billion cubic feet per day. Gas inventories fell to an 11-year low in March after the frigid winter spurred record demand.

Models and analytics

A paper on the prediction of extreme geophysical, industrial and biophysical flows using particle methods, by Messrs. Cleary, Cohen, Harrison, Sinnot, Prakash and Mead, groups processes as diverse as eating and locomotion, extreme geophysical flows such as tsunamis and dam-collapse inundation, bio-medical applications such as the transport of material in the gastro-intestinal tract and heart pumps and industrial processes such as crushing and grinding. They examine the use of mesh-less particle-based methods such as DEM (Discrete Element Method and SPH (Smoothed Particle Hydrodynamics that they say have a strong range of predictive advantages over traditional grid-based continuum methods for these type applications.

In all cases, there are significant sources of variability that need to be taken into account in the modeling: For geophysical/disaster modeling, variability is mainly reflected in the range and nature of the scenarios that need to be considered in building risk frameworks in which these models can predict specific consequences. For example, the paper notes that the range of possible failure scenarios of a dam or the range of heights, speeds and water volumes for tsunamis generated by poorly understood initiation events.

In all such applications there is uncertainty about material properties and the details of the initial conditions whose effects need to be understood. For example, in an industrial crusher or mill, the authors say, the performance of the process is heavily influenced by the specific nature of the material being comminuted. This can vary strongly between materials and between different instances of what is nominally the same material. Such variability influences both the inputs to specific instances of the deterministic models and the usage scenarios that need to be considered.

Water flowing underground

According to Noah Garrison, a blogger for the Natural Resources Defense Council Staff, for much of California, 2013 was the driest year since the state started keeping records more than 150 years ago. Statewide, the average rainfall was only seven inches, far less than the long-term average of 22 inches.

An analysis released recently by the NRDC and the Pacific Institute shows that capturing stormwater runoff for water supply across Southern California and the San Francisco area could increase local water supplies by between 420,000 and 630,000 acre-feet per year, roughly the amount of water used by the entire city of Los Angeles on an annual basis.

In the run-up media coverage to this weekend’s big national golf tournament, the U.S. Open, the issue of water use at golf courses has been current. In fact, several analysts spoke with confidence of big changes coming to golf courses from which sprinkler systems have been removed, trees are disappearing and the rough is really rough. At a single golf course, an example was cited of a golf course at which, as a result of these changes, 25 million gallons of water a year will be saved.

Energy and water are the life blood of the process industries and extreme flows in those two sectors are amongst the day’s biggest headlines. The stories in this year’s flow supplement are meant for those who patiently and in great detail, every day tend to measured, productive process flows that are slowly but surely tending to the extreme.

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