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Foundation :: Engineering Applications :: SWTPAS


Subsonic Wind Tunnel Performance Analysis Software

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source code available SOURCE CODE AVAILABLE

SWTPAS was developed as an aid in the design and analysis of subsonic wind tunnels. It brings together and refines previously scattered and over-simplified techniques used for the design and loss prediction of the components of subsonic wind tunnels. It implements a system of equations for determining the total pressure losses and provides general guidelines for the design of diffusers, contractions, corners and the inlets and exits of non-return tunnels.

The algorithms used in the program are applicable to compressible flow through most closed- or open-throated, single, double- or non-return wind tunnels or ducts. A comparison between calculated performance and that actually achieved by several existing facilities produced generally good agreement. Any system through which air is flowing which involves turns, fans, contractions etc. (e.g., an HVAC system) may benefit from analysis using this software. This program is an update of ARC-11138 which includes PC compatibility and an improved user interface.

The method of loss analysis used by the program is a synthesis of theoretical and empirical techniques. Generally, the algorithms used are those which have been substantiated by experimental test. The basic flowstate parameters used by the program are determined from input information about the reference control section and the test section. These parameters were derived from standard relationships for compressible flow. The local flow conditions, including Mach number, Reynolds number and friction coefficient are determined for each end of each component or section. The loss in total pressure caused by each section is calculated in a form non-dimensionalized by local dynamic pressure. The individual losses are based on the nature of the section, local flow conditions and input geometry and parameter information. The loss forms for typical wind tunnel sections considered by the program include:
  • constant area ducts,
  • open throat ducts,
  • contractions,
  • constant area corners,
  • diffusing corners,
  • diffusers,
  • exits,
  • flow straighteners,
  • fans,
  • and fixed, known losses.

Input to this program consists of data describing each section; the section type, the section end shapes, the section diameters, and parameters which vary from section to section. Output from the program consists of a tabulation of the performance-related parameters for each section of the wind tunnel circuit and the overall performance values that include the total circuit length, the total pressure losses and energy ratios for the circuit, and the total operating power required. If requested, the output also includes an echo of the input data, a summary of the circuit characteristics and plotted results on the cumulative pressure losses and the wall pressure differentials.
SWTPAS carries the NASA case number ARC-13129. It was originally released as part of the NASA COSMIC collection.
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