physics

Standard wind tunnel models

Standard wind tunnel models is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Standard wind tunnel models rather than just read about it. In short: Standard wind tunnel models, also known as reference models, calibration models (French: maquettes d'étalonnage) or test check-standards are objects of relatively simple and precisely defined shapes, having known aerodynamic characteristics, that are tested in wind tunnels. Standard models are used in order to verify, by comparison of wind tunnel test results with previously published results, the complete measureme…

Key takeaways

Standard wind tunnel models belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Standard wind tunnel models to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Standard wind tunnel models from memory before moving on to harder problems.

Reference excerpt

Standard wind tunnel models, also known as reference models, calibration models (French: maquettes d'étalonnage) or test check-standards are objects of relatively simple and precisely defined shapes, having known aerodynamic characteristics, that are tested in wind tunnels. Standard models are used in order to verify, by comparison of wind tunnel test results with previously published results, the complete measurement chain in a wind tunnel, including wind tunnel structure, quality of the airstream, model positioning, transducers and force balances, data acquisition system and data reduction software. More specifically, standard wind tunnel models are used for:

confirmation of the reliability of the data from a new wind tunnel by comparison with results from other wind tunnel facilities; providing baselines for correlation of results from different wind tunnels; checkouts of data repeatability over time; checkouts of data repeatability after repairs or modifications of the wind tunnel structure; assessment of the wall interference effects; identification of problems and faults in the operation of a wind tunnel; verification of new measurement techniques or devices; training of wind tunnel personnel. Besides, results from wind tunnel tests of standard models are used as test cases for verification of computational-fluid-dynamics (CFD) computer codes. In most wind tunnels, standard models are tested during the commissioning and calibration of the facility. This sometimes has an unfortunate effect that the test results are not as good as they can be, because the wind tunnel and its measurement system have not yet been optimally tuned at the time of the test. However, some laboratories have adopted the practice of periodical testing of a standard model every couple of years in order to provide a continued confidence in the reliability of measurements in their wind tunnels. Standard wind tunnel models are usually (but not always) intended for one of the basic wind tunnel measurement types, such as the measurement of forces and moments with force balances or measurements of pressure distribution. Results of wind tunnel tests of these models are generally published in the form of nondimensional aerodynamic coefficients (thus being made independent of model size) and made available to the wind-tunnel community, often in review reports containing inter-facility comparisons of data, discussing observed scatter of results, different testing conditions, production differences between models etc. As the majority of wind tunnel tests is related to aeronautics, most standard wind tunnel models resemble simplified forms of wings, airplanes or missiles. Such are, for static tests: NACA 0012 and CLARK Y (2D wing-segment models with typical airfoils), AGARD-B / AGARD-C (generic delta-wing-airplane shapes), ONERA-M (a generic transport-airplane shape), HB-2 (Hypervelocity ballistic model 2, a shape similar to a reentry-body). For dynamic tests, the often-used standard models are: SDM (Standard dynamic model, a generic fighter-like airplane shape somewhat similar to F-16)), BFM (Basic finner model, a generic conical-cylindrical missile with four fins at the rear end) and MBFM (Modified basic finner model). A number of other standard models exists as well. With the increased use of wind tunnels in the testing of road vehicles, several standard models of generic car shapes were defined., such as the Ahmed body , MIRA reference car , etc. Some wind tunnel laboratories perform periodical checkouts using internally defined standard models that are selected from the repository of models previously tested in the facility Geometry of a standard wind tunnel model is defined relative to some easily identified parameter (see figure), e.g. body diameter or wing chord. The geometry is published by the institution proposing the model. Beside the model itself, a standard model support, such as a sting, to be used with the model, is usually defined. An actual model is built to a size suitable for the size of a specific wind tunnel test section, in particular taking care that the frontal blockage of the model (the ratio of the model cross-section area to wind tunnel test section area) is kept well below 1% (except for wall-interference research where the models may be larger). In order to eliminate the effects of production differences between models in inter-facility comparisons, sometimes the same physical standard model is tested in several wind tunnels

See also Wind tunnel AGARD-B wind tunnel model

References

External links Media related to Standard wind tunnel models at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Standard wind tunnel models

Start with the simplest possible case. Write down what Standard wind tunnel models claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Standard wind tunnel models before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Standard wind tunnel models ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Standard wind tunnel models

In research: Standard wind tunnel models appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Standard wind tunnel models in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Standard wind tunnel models is common in secondary-school and first-year university syllabi. It links to neighbouring topics Physical models, Wind tunnels, so understanding it makes those chapters shorter.
In everyday life: Look for Standard wind tunnel models outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Standard wind tunnel models in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Standard wind tunnel models means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Standard wind tunnel models out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Standard wind tunnel models in simple terms?

Why does Standard wind tunnel models matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Standard wind tunnel models?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Standard wind tunnel models.