All Terrain Thinking

A Compendium of things I think are Important

Generally Speaking, Think on this...

Being a “rat” can actually be fun

M. Hoepfer

The job I write about here is not one of the fanciest ones. It involves hands-on work, and getting oily, bumped and scratched on a regular basis. I work in a wind tunnel, and while this may sound like an interesting job, like every other job it becomes a normality after a while.

In wind tunnels, models are measured for automobiles, airplanes, buildings, wind turbines, and everything else that could possibly depend on, or be damaged by, flowing air. While it may be obvious for airplanes to be measured in wind tunnels, cars (not only race cars!) for example are not only being tested for low drag (which translates to fuel economy, which became a much more important sales argument in the recent past), but also for lift/ downforce, which has great influence on the car’s behavior at higher speed, and is a major contributor to safe handling. Especially for airplanes, wind tunnel measurements are an essential part during the preliminary design phase and for certification, and may very well prove the designer’s ideas to be infeasible in reality. Therefore, these tests must be done with high speed and accuracy, and low margin for error.

As a wind tunnel engineer, one is responsible for everything concerning the proper operation for those measurements. This involves a wide variety of knowledge and experiences. Wind tunnel time is very expensive, and must be planned to be as short as possible. Design of Experiments techniques may come in handy here. Models must be built, prepared, and installed in the tunnel. This requires very good skills with hands-on work, all sorts of hardware tools, materials behavior, etc. Of course, the tunnel itself must be maintained, and in the very rare cases of spare time, improved.

Measuring a wind tunnel model also requires knowledge of measuring techniques and installations. One must be able to estimate aerodynamic forces and moments, and set up the hardware accordingly. So, of course, being fit in all aspects of aerodynamics is essential. It’s absolutely necessary to know the tricks that air would play on you when you take measurements, and very often, appropriate corrections must be made.

One should also be fit in at least two different programming languages, LabView and Matlab. The former is to program the actual data acquisition software, the latter is very helpful for data evaluation. Further computer skills would also include CFD, Computational Fluid Dynamics, which will help to predict the behavior to be expected, and can shorten the whole process by quite a lot. Unlike popular belief, CFD is not likely to replace wind tunnel measuring any time soon.

If, as in my case, the set-up for each experiment or model is a unique one, having an idea of electronics definitely helps, as sometimes the measurement hardware must be modified, or own small electronics must be developed to aid the existing hardware.

Once the data is taken, one must be able to judge the correctness of the results. Here again aerodynamic experience comes into play. Having a solid knowledge of statistics and statistical inference helps to find errors, and deal with them accordingly if necessary. Data must be processed, and since these measurements are usually taken for customers, they must also be prepared for presentations. Of course, one must be in contact with the customers at all times, since they want feedback on how things are going, or whether they go well at all, so it helps to have a bit of what one might call people skills. If things go haywire, one must be able to sit with the customer, find the errors, and suggest feasible and viable alternatives. Being able to set up and stick to a time schedule is essential, as is the ability for accounting, cost- and risk calculation and evaluation. It’s almost like a managerial type of job at times.

Wind tunnels are usually not hit by daylight too often. Many times, the models measured are those of new prototypes, and no-one wants the competition to see any of these. This is especially critical when DoD (Department of Defence) projects come in. But I also had cases where the (automotive) customer even allowed only certain people of the wind tunnel crew to actually see and work on the model. Wind tunnel people are sometimes referred to as “tunnel rats,” and while this synonym may not be the most charming of all, usually wind tunnel engineers are looked at with a certain amount of respect by many. I could imagine that many people would enjoy a bit more hands-on, rather than doing computer all day long.

One gets to work together with many different kinds of people. Oftentimes, help from workshops is required, be it metal, wood, or electronics. These people are very down to earth, helpful and approachable. It also helps to be in good standing with them, since they are the ones that can help you if your car breaks down, or you need a small part made for your home or hobby.

The customer one has to work with is usually the engineering type as well. They know of the difficulties of the job, and are mostly ready to help and jump in if need be. Of course, they need to be genuinely interested in getting good results quickly, but very often, they seem quite interested in the processes involved to get them what they need.

Eventually, every now and then, (project) management must be dealt with as well. This sometimes proves to be trickier than one thinks. Oftentimes, managers completely lack the insight and technical understanding needed to judge the necessity and quality of the work. They need to reduce cost, and a wind tunnel is a formidable way of spending a lot of money for things whose meaning may not be immediately visible.

If someone would want to work in this field, I would recommend it wholeheartedly, but also advice to exercise caution. While the work scope is extremely widespread, and one gets to be in contact with a wide variety of different products, processes and people, it is at times extremely frustrating work when “nothing works” and the customer is breathing down your neck. Be ready to bump your head and get dirty and oily, and you will be rewarded with an extremely versatile and interesting work.

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