# Compressible Aerodynamics Calculator - Help

This calculator, written in Javascript by William Devenport at the Aerospace and Ocean Engineering Department, Virginia Tech, computes the standard relations for compressible flow of a perfect gas. The calculator is intended to provide a faster more convenient alternative to printed tables and charts (e.g. NACA Report 1135). Three sets of relations are included;
• Isentropic Flow Relations
• Normal Shock Relations
• Oblique Shock relations
The relations themselves are taken from standard aerodynamics texts. Symbols have their usual meanings. 'Gamma' and 'rho' are substituted for the corresponding greek letters denoting the ratio of specific heats and density. Subscript 'o' is used to refer to stagnation or total conditions, superscript '*' refers to sonic conditions.

For each set of relations the calculator is used by selecting the variable to input, typing in its value, and then pressing the calculate key. For example, to compute the flow properties corresponding to a Prandtl-Meyer angle of 20 degrees, go to the 'Isentropic flow relations'. Click on the field immediately following 'INPUT:' that says 'Mach Number' and select 'P-M angle (deg.)'. Replace whatever is in the next field (adjacent to the 'Calculate' button) with 20 and press 'Calculate'. Output is displayed in the table immediately following.

Values from the output (or input) fields may be copied and pasted to any input field or to the 'Scratch pad' at the bottom of the screen. The scratch pad is for performing the miscellaneous calculations necessary when using the Calculator to solve an aerodynamics problem. Arithmetic expressions typed into the left-hand box of the scratch pad are computed and the result displayed in the right-hand box. Results may be pasted into the input fields of the Calculator. Expressions may contain contain the operators */+- (no ^ or **), the functions pow(,), sqrt(), exp(), log(), abs(), sin(), cos(), tan(), asin(), acos() and atan(), and parentheses. Note that all angles are assumed to be in radians and that out-of-range functions (e.g. sqrt(-1)) return zero.

You may adjust the size of the frame containing the scratch pad, should it be too big or too small, by dragging the frame divider up or down.

Reference: Equations, Tables and Charts for Compressible Flow, NACA Report 1135, Avail. AMTEC Engineering Inc., Bellevue, WA 98004.