Struct Boattail 

#[non_exhaustive]
pub struct Boattail {
    pub length_m: f64,
    pub fore_diameter_m: f64,
    pub aft_diameter_m: f64,
    pub area_ratio: f64,
    pub length_ratio: f64,
    pub half_angle_rad: f64,
    pub rule_factor: f64,
    pub separation_weight: f64,
    pub chart_end_ratio: f64,
}

A boattail’s geometry and the terms of its pressure drag that don’t depend on the Mach number. Coefficients are on its fore area π d₁²/4.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

length_m: f64

Length l, m.

fore_diameter_m: f64

Fore diameter d₁, m.

aft_diameter_m: f64

Aft diameter d₂, m.

area_ratio: f64

Area ratio a = (d₂/d₁)².

length_ratio: f64

Length over fore diameter, l/d₁.

half_angle_rad: f64

Half-angle of the cone through the same ends, θ = atan((d₁ − d₂)/(2l)), rad.

rule_factor: f64

Niskanen’s boattail factor (eq. 3.88), used below Mach 0.8.

separation_weight: f64

The share of the separated value in the supersonic drag and base pressure: (SEPARATION_ONSET_RAD, SEPARATION_COMPLETE_RAD) mapped linearly to (0, 1).

chart_end_ratio: f64

The chart’s share of the 2D limit at its end, x = 1.4, at most 1: r in the drag past the chart.

Implementations

impl Boattail

pub fn new( length_m: f64, fore_diameter_m: f64, aft_diameter_m: f64, ) -> Result<Self, AeroError>

A boattail of length_m narrowing from fore_diameter_m to aft_diameter_m, compared as the cone through the same ends. For one length, area ratio and Mach number Jack found the cone’s wave drag the smallest of conical, tangent-parabolic and secant-parabolic boattails (NACA TN 2972 p. 1), so a curved boattail likely drags more than hpr gives; its steeper aft end may also separate where the cone’s chord angle doesn’t.

Errors

AeroError::Domain for a non-positive or non-finite length or fore diameter, a negative aft diameter, or diameters that don’t decrease.

pub fn expansion_limit(&self, mach: f64) -> Result<f64, AeroError>

The 2D limit C_PM = −C_p,PM(M, θ)(1 − a) at mach ≥ 1: a Prandtl–Meyer expansion’s pressure over the whole annulus.

Errors

As expansion_pressure_coefficient.

pub fn attached_pressure_drag(&self, mach: f64) -> Result<f64, AeroError>

The attached boattail’s pressure drag at mach ≥ 1: the chart held to the 2D limit, and past the chart’s end the limit less the chart’s share of it closing as 1/x (module docs).

Errors

As expansion_pressure_coefficient.

pub fn pressure_drag_coefficient(&self, mach: f64) -> Result<f64, AeroError>

The boattail’s pressure drag on its fore area at any Mach number (module docs): Niskanen’s rule to Mach 0.8; from Mach 1, the attached drag (held at its Mach 1.2 value to Mach 1.2) blended toward the separated value at the Mach number itself; a straight line between. So a boattail steep enough to separate completely drags like the step it tends to.

Errors

AeroError::Domain for a negative or non-finite Mach number.

pub fn base_pressure_ratio( &self, mach: f64, base_area_ratio: f64, ) -> Result<f64, AeroError>

The factor on the base drag of a base right behind this boattail, of area ratio a_b (the base’s area over the boattail’s fore area): boattail_base_pressure_ratio, moved toward 1 by the separation weight.

Errors

As boattail_base_pressure_ratio.

Trait Implementations

impl Clone for Boattail

fn clone(&self) -> Boattail

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Boattail

impl Debug for Boattail

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for Boattail

fn eq(&self, other: &Boattail) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Boattail

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Boattail