The original version of this program is called VuCalc and is based on the program by Tom Benson of NASA Glenn Research Center as an aid to making calculations in compressible fluid dynamics. Benson's original code was for Silicon Graphics workstations running Unix. I modified it to run on a PC running Microsoft Windows with the Delphi programming environment.. In 2019, I decided to update the application, mainly because the user base of Delphi and Pascal seemed to be drying up and also users wanted apps on their phones. I decided that the best solution that maximized the user base would be a single-page web application that used the screen layout features of HTML5 and CSS along with a JavaScript coding of the gas dynamic equations. This new app is self-contained in a file called flowcalc.html and no additional files are needed for use. All calculations are performed on the local machine and no server is used. This insures that one should be able to use the app on any operating, including mobile devices and the calculations are not dependent upon internet access.

A distinctive (perhaps unique) characteristic of the HTML application lies in its transparency. Although all HTML files are in some sense open source, in practice it can be quite difficult to decipher the source code. The text of flowcalc.html can be read on an ordinary computer display without sidewise scrolling and can be output on an ordinary printer.

VuCalc and FlowCalc are based on a program 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

Normal Shock

Oblique Shock

Rayleigh Flow

Fanno Flow

Standard Atmosphere

There is also a screen for setting gamma, the ratio of specific heats and a main screen that is displayed upon launch of the application.

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 the program will solve for the corresponding
Mach number and the remaining quantities.

Screen Shot (Delphi)

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 the program will calculate the
corresponding Mach number and all other quantities.

Screen Shot (Delphi)

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.

Screen Shot (Delphi)

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 the program to compute the coressponding
Mach number as well as the remaining flow parameters.

Screen Shot (Delphi)

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 the program to compute the coressponding
Mach number as well as the remaining flow parameters.

Screen Shot (Delphi)

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.

Screen Shot (Delphi)

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. The gasdynamic equations as coded in JavaScript may be copied directly from the HTML file. Python and Fortran versions are also available from the download page.

- There is a similar calculator developed by William Devenport of Virginia Tech.
- There is a program called Compressible Flow Toolbox, written by Kevin Melcher of NASA Glenn that is available thru the NASA Software Repository. This is a MATLAB program.

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.

- Go to the page of references for these programs.
- Go to the download page for these programs.