Function area_mach_ratio_kernel 

pub fn area_mach_ratio_kernel<R>(mach: R, gamma: R) -> Result<R, PhysicsError>
where
    R: RealField + FromPrimitive,

Area–Mach relation for quasi-one-dimensional isentropic duct flow: A/A* = (1/M) · [ 2/(γ+1) · (1 + (γ−1)/2 · M²) ]^((γ+1)/(2(γ−1))), where A* is the sonic-throat area.

Dimensionless. A/A* = 1 exactly at M = 1; the relation is double-valued in M for A/A* > 1 (one subsonic, one supersonic branch).

Errors

PhysicsError::PhysicalInvariantBroken unless M is finite and > 0 (the relation divides by M, and A/A* diverges at rest) and γ is finite and > 1 (NaN inputs are rejected).

References

• Anderson, “Modern Compressible Flow: With Historical Perspective,” McGraw-Hill — area–Mach relation, quasi-one-dimensional flow (Ch. 5).