hpr_design/
finish.rs

1//! Surface finishes: the roughness height that limits a surface's skin friction.
2//!
3//! The named finishes are the rows of Barrowman 1967 Table 4-1 ("Approximate Surface Roughness
4//! Heights of Physical Surfaces", p. 46, after Hoerner, *Fluid-Dynamic Drag*, 1965, p. 5-3).
5//! Niskanen 2009 Table 3.2 (p. 44) reprints ten of its fifteen rows with the same heights. Any
6//! other roughness is a [`Finish::Custom`] height. See `docs/physics/aero.md`.
7
8use serde::{Deserialize, Serialize};
9
10use crate::error::DesignError;
11use crate::shapes::check_dimension;
12
13/// A surface finish, by its roughness height `R_s`.
14#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize, schemars::JsonSchema)]
15#[serde(tag = "kind", rename_all = "snake_case", deny_unknown_fields)]
16#[non_exhaustive]
17pub enum Finish {
18    /// A mirror-like surface, 0 µm (Barrowman Table 4-1).
19    Mirror {},
20    /// Average glass, 0.1 µm.
21    AverageGlass {},
22    /// A finished and polished surface, 0.5 µm.
23    Polished {},
24    /// An aircraft-type sheet-metal surface, 2 µm (Barrowman Table 4-1 only).
25    SheetMetal {},
26    /// An optimum paint-sprayed surface, 5 µm.
27    OptimumPaint {},
28    /// Planed wooden boards, 15 µm.
29    PlanedWood {},
30    /// Paint in aircraft mass production, 20 µm. The default.
31    MassProductionPaint {},
32    /// Bare steel plating, 50 µm (Barrowman Table 4-1 only).
33    BareSteel {},
34    /// A smooth cement surface, 50 µm.
35    SmoothCement {},
36    /// A surface with an asphalt-type coating, 100 µm (Barrowman Table 4-1 only).
37    AsphaltCoating {},
38    /// A dip-galvanized metal surface, 150 µm.
39    DipGalvanized {},
40    /// Incorrectly sprayed aircraft paint, 200 µm.
41    PoorPaint {},
42    /// The natural surface of cast iron, 250 µm (Barrowman Table 4-1 only).
43    CastIron {},
44    /// Raw wooden boards, 500 µm.
45    RawWood {},
46    /// An average concrete surface, 1000 µm.
47    Concrete {},
48    /// A given roughness height.
49    Custom {
50        /// Roughness height, m.
51        roughness_m: f64,
52    },
53}
54
55impl Default for Finish {
56    fn default() -> Self {
57        Finish::MassProductionPaint {}
58    }
59}
60
61impl Finish {
62    /// Every named finish, smoothest first.
63    pub const NAMED: &'static [Finish] = &[
64        Finish::Mirror {},
65        Finish::AverageGlass {},
66        Finish::Polished {},
67        Finish::SheetMetal {},
68        Finish::OptimumPaint {},
69        Finish::PlanedWood {},
70        Finish::MassProductionPaint {},
71        Finish::BareSteel {},
72        Finish::SmoothCement {},
73        Finish::AsphaltCoating {},
74        Finish::DipGalvanized {},
75        Finish::PoorPaint {},
76        Finish::CastIron {},
77        Finish::RawWood {},
78        Finish::Concrete {},
79    ];
80
81    /// Roughness height `R_s`, m.
82    ///
83    /// # Errors
84    ///
85    /// [`DesignError::Domain`] for a custom height that is negative or not finite.
86    pub fn roughness_m(&self) -> Result<f64, DesignError> {
87        const MICRON: f64 = 1e-6;
88        Ok(match *self {
89            Finish::Mirror {} => 0.0,
90            Finish::AverageGlass {} => 0.1 * MICRON,
91            Finish::Polished {} => 0.5 * MICRON,
92            Finish::SheetMetal {} => 2.0 * MICRON,
93            Finish::OptimumPaint {} => 5.0 * MICRON,
94            Finish::PlanedWood {} => 15.0 * MICRON,
95            Finish::MassProductionPaint {} => 20.0 * MICRON,
96            Finish::BareSteel {} | Finish::SmoothCement {} => 50.0 * MICRON,
97            Finish::AsphaltCoating {} => 100.0 * MICRON,
98            Finish::DipGalvanized {} => 150.0 * MICRON,
99            Finish::PoorPaint {} => 200.0 * MICRON,
100            Finish::CastIron {} => 250.0 * MICRON,
101            Finish::RawWood {} => 500.0 * MICRON,
102            Finish::Concrete {} => 1000.0 * MICRON,
103            Finish::Custom { roughness_m } => {
104                check_dimension("roughness height", roughness_m, true)?;
105                roughness_m
106            }
107        })
108    }
109}
hpr_design/finish.rs

hpr_design/
finish.rs
