Engineering Applications ::
Subsonic Wind Tunnel Performance Analysis Software
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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,
- constant area corners,
- diffusing corners,
- flow straighteners,
- 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
SWTPAS carries the NASA case number ARC-13129. It was originally released as part of the NASA COSMIC collection.
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