scope:

This document provides a recommended test nomenclature for steady-state wind tunnel testing involving force, moment, and pressure data. This guide may be used as a translator (Rosetta stone) between different facilities and customers. The use of this document will enhance the understanding and communication between customers and facilities in the wind tunnel testing community.

A major focus throughout this process has been to achieve a balance between too much or too little detail in the nomenclature parameters and definitions. When the names become too long, it is no longer nomenclature, but a full description of the item. The best nomenclature is immediately understood with no need to look it up. It is recognized that for this guide to be fully adopted, it must be easy to use and understand.

Purpose

Test nomenclature ambiguity can be a source of confusion, error, and inefficiency. While wind tunnel facilities measure many of the same physical quantities and apply similar corrections to their data, no two facilities and customers use the same set of nomenclature. This presents difficulties for facilities with multiple customers and customers who test at multiple facilities. This sometimes leads to serious confusion, especially when a variable ends up with the same name but a different meaning. Finally, wind tunnel operation often requires the transfer of staff between facilities, which would be greatly facilitated by common nomenclature at each facility.

Constraints

For each parameter addressed, a standard name is defined for use by data reduction, display, and storage devices. The computer names are limited to fourteen characters with no distinction made between upper and lower case. Only standard letters, numbers, and the underscore character are allowed (no symbols or Greek letters); subscripts and superscripts are not allowed. The meaning, unit of measure, and sign convention are defined for each parameter as well as a recommended name for publication. The standard units for each parameter are defined for the International System, SI, and the English system. Units are not defined for the publication parameters since it is typically done in the publication.

The following groups of testing parameters are included in this recommended nomenclature:

Test Section Conditions;

Model Axis Systems and Attitude;

Dimensional References;

and Pressures, Forces, Moments, and their Coefficients.

Naming Convention

The parameter names consist of a base name and a four-character suffix, which provides information about the parameter. The base name is a commonly used, and thus recognizable, name for the specific parameter. The suffix begins with an underscore character to set it apart from the base name.

The remaining three characters begin with an "S" to identify and associate the parameter with this AIAA Wind Tunnel Nomenclature standard. An "X" in this position instead of an "S" indicates that a change was made to the parameter requiring the user to seek further guidance.

The next character in the suffix defines the parameter group. For example, all parameters describing the empty test section flow field have an "F" in this position.

The last character of the parameter name defines the system of units. "I" indicates that the SI convention is used, "E" indicates that English units are presented, and "C" indicates that the parameter is nondimensional.

The previous statements result in the formulation of the following suffix for all standard parameters:

_Sxy

Where: _S identifies the nomenclature as part of this recommended standard

x is the group descriptor

A Angles

C Coordinate systems

F Flow field (empty test section at model location)

G Geometry - lengths, areas, and weight

L Loads - forces, moments and their coefficients

P Pressures and their coefficients

y is the units descriptor

I SI units

E English units

C Common to English and SI units

For example, the extension "_SFE" would be attached to all tunnel flow condition parameters using English units. Therefore, the nomenclature name for the freestream dynamic pressure (q) in English units is Q_SFE.

Balance or Parameter Number

Some parameters are associated with the balances that are used during a wind tunnel test. These parameters have an n following the base name representing the balance number. For example, on a test with two balances, THETABALn_SAC would have the names THETABAL1_SAC and THETABAL2_SAC representing the balance pitch angle for balance 1 and 2, respectively.

Other parameters that need additional identification are associated with pressure measurements. Pressure measurements are split into two groups, model surface pressures and other model or testrelated pressures such as base and tunnel wall pressures. The model surface pressures are identified by an array (indicated by () in the name), which can be an array of single numbers, an array of two numbers indicating row and pressure number, or any other array type. The second group of parameters have an x following the parameter base name. An example would be PBASEx_SPE where PBASE1_SPE and PBASE2_SPE represent base pressures 1 and 2, respectively.

Corrections

Calculations, equations, or other details describing tares and corrections (i.e., tunnel wall corrections and weight tares) are not provided because they tend to be facility dependent. Rather, "fully corrected" in this document indicates that the facility has applied all corrections that they typically provide. Wall pressure coefficients are normalized by an uncorrected q; model pressure coefficients and force and moment coefficients by a corrected q, which is defined by the facility.

There are three defined levels of corrections described in this document; uncorrected, corrected for base and cavity pressures, and corrected for all facility specified adjustments.

Parameters containing U_Sxy are uncorrected. The subscript u is used in the publication names.

Parameters containing BC_Sxy are corrected for base/cavity pressures only. The subscript bc is used in the publication names.

Parameters not containing the above include all corrections normally provided by the facility (i.e., Q_SFE is the fully corrected tunnel dynamic pressure).