What We Have Here is a Fluid Dynamics Problem

By Jon Miller Updated on November 9th, 2015

IMG_1812This weekend I attended a community recital to hear my daughter play piano. There were 23 children playing solo and duet pieces on the piano, violin, cello, clarinet and saxophone. There were even a few singers. At the conclusion of the recital, one of the music teachers thanked the audience and asked everyone to help put away the folding chairs. About 60 people stood up, folded their chair and shuffled towards the storage cabinets along the walls, to a grinding halt. After a moment I thought, “What we have here is a fluid dynamics problem.”

Fluid dynamics are behind what people commonly think of as a “flow problem”. In the context of lean management, we imagine material flow or information flow. Simply put, a flow problem involves material or information taking longer to arrive at its destination than the customer wants. This is not only a problem for the customer, it is a problem for the producer because the recovery of the cash and costs associated with creating the flow is also delayed. Flow problems can sink companies. The just-in-time pillar of the Toyota Production System, supported by SMED, heijunka and various other support systems, are countermeasures to root causes of such flow problems.


It would seem like there is nothing simpler than asking a few dozen adults to put some folding chairs into a wall cabinet. However, in our case all but 3 or 4 people found themselves waiting and watching at any given time, as those closest to the storage cabinets fitted their chairs in the box. Folding the chair is not hard. Lifting the chair is not hard. Even putting the chair in the cabinet is not hard. Fighting your way through 57 other people to the cabinet is the hard part. Luckily, patience and civility prevailed. Although the music teacher who asked us all to put away the chairs was no doubt well-intentioned, as with any endeavor there are good and bad ways to get this done.

How to put away 60 chairs in 3 wall cabinets at a community center, in order of effectiveness:

Best method: Organize a bucket brigade consisting of 4-5 people per crew, each assigned to one box.

Good method: Ask an unspecified number of people to help put chairs away, let the others go home, and allow the volunteers to self-organize.

Acceptable method: Each person folds and and stacks their chair against the wall near the cabinets, with a few people moving them into cabinet.

Method observedEveryone attempts to complete the entire process of fold, carry, put away, for their chair.

Worst method: Leave the chairs in place and let the next people who use the space rearrange them. While this method may seem fastest (zero time spent if everyone walks away after the recital) only the first group saves time and time is wasted for all following groups.

Whatever it is that we are trying to flow, when that thing gets to a certain thickness and density, we get into trouble. Putting away chairs after a community center event is a benign and trivial case of a fluid dynamics problem. Stampedes at Middle Eastern religious pilgrimages, scrambles to the exit at indoor fireworks-involving nightclubs, and competitive Black Friday shoppers are deadlier instances of fluid dynamics problems. When we remain ignorant of how fluid dynamics affects our well-being, we risk wasting money, time and even health.

When I become philosopher king, I will decree that for any multi-person endeavor, one of them shall be assigned as a logistics person.

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