Public Domain Aeronautical Software (PDAS)

VuCalc is based on a program of the same name written by Tom Benson of NASA Glenn as an aid to making calculations in compressible fluid dynamics. There are six screens, each of which performs a different class of calculations.

#### Isentropic Flow

The isentropic flow page enables the user to calculate the total temperature ratio, total pressure ratio, total density ratio, area ratio, Mach angle and Prandtl-Meyer function for any Mach number. In addition, the values of any one of these quantities may be specified and VuCalc will solve for the corresponding Mach number and the remaining quantities.
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#### Normal Shock

The ratios of downstream to upstream values of various quantities may be computed for any Mach number. As with the isentropic flow page, the value of any flow parameter may be specified and VuCalc will calculate the corresponding Mach number and all other quantities.
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#### Oblique Shock

The oblique shock problem has an additional degree of freedom in specifying the problem. In this case, the user supplies the upstream Mach number and one of the following variables: ramp angle, wave angle, total pressure ratio, static pressure ratio, temperature ratio, density ratio or downstream Mach number. The other variables will then be computed and displayed. Of course, there are many cases for which there is no solution with an attached shock.
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#### Standard Atmosphere

A flight condition in the standard atmosphere is specified by the altitude and Mach number. For these conditions, the values of velocity, temperature, density, pressure, speed of sound, unit Reynolds number, viscosity, dynamic pressure are computed and displayed. SI or US units may be used for input. When switching between SI and US units, the previous case is remembered and the appropriate values are shown for the other set of units.
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#### Rayleigh Flow

The flow condition known as Rayleigh Flow assumes that the flow is in a constant-area duct without friction but with heat transfer. This type of flow turns out to be a good approximation of heat exchangers and of constant-area combustion chambers such as is typical of gas turbines. Typical tables of Rayleigh Flow show ratios of various thermodynamic flow quantities at a given Mach number to the value of this same quantity at a Mach number of 1.0 with the flow modified by heat transfer without friction. Typical quantities are static temperature, total temperature, static pressure, total pressure, density, and velocity. As on the other pages, one may select a given value of any flow parameter and command VuCalc to compute the coressponding Mach number as well as the remaining flow parameters.
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#### Fanno Flow

Fanno flow assumes flow in a constant-area duct with friction but without heat transfer. As on the other pages, one may select a given value of any flow parameter and command VuCalc to compute the coressponding Mach number as well as the remaining flow parameters.
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#### Usage

The program may be used as supplied, but because the source code is included, the functions that compute the flow quantities are available for inclusion in your own computing projects. The flow ratios in terms of Mach number are straightforward codings of the equations in NACA Report 1135 or any gas dynamics textbook. The inverse relations can sometimes be solved by algebraic manipulation, but must be computed by numerical root finding in others.

## Alternate Programs

• There is a similar calculator developed by William Devenport of Virginia Tech.
• This program was not released by NASA through COSMIC. The source code for the C version of Vu-Calc with graphical interface for a Silicon Graphics workstation was obtained from NASA Lewis (now Glenn). The code was converted to Pascal and the Delphi interface for Microsoft Windows by Public Domain Aeronautical Software. All value added by PDAS is placed in the public domain.

Get a copy of all the programs from Public Domain Computer Programs for the Aeronautical Engineer.
Last updated: by Ralph Carmichael, pdaerowebmaster AT gmail DOT com
Public Domain Aeronautical Software (PDAS)