feedtwin.engine.design.DischargeModel Class Reference

Public Member Functions
float	cd_infinite (self, float|None diameter=None)
float	cd (self, float reynolds, *, float|None pressure=None, float|None temperature=None, float|None diameter=None)

Static Public Attributes
float	cd_inf = 0.6
float	a_re = 0.0
float	cd_min = 0.15
bool	use_pressure_correction = False
float	p_ref = 5.0e6
float	a_p = 0.0
bool	use_temperature_correction = False
float	t_ref = 90.0
float	a_t = 0.0
bool	use_geometry_cd = False
float	d_ref = 2.0e-3
float	d_min = 4.0e-4
float	cd_small_hole_exponent = 0.20
float	cd_large_hole_log_gain = 0.015
float	cd_inf_max = 0.62
float	cd_inf_min_geom = 0.48

Detailed Description

Reynolds- and geometry-dependent discharge coefficient.

``Cd(Re) = Cd_inf(d) - a_Re / sqrt(Re)``, clamped to ``[Cd_min, Cd_inf(d)]``,
with optional pressure and temperature corrections. Reproduced rather than
re-derived: this must agree with EngineDesign's own answer at the same
operating point or the two tools are modelling different injectors, and a
boundary that disagrees with the thing it bounds is worse than no boundary.

``Cd_inf`` depends on hole size when ``use_geometry_cd`` is set, which it is
on the current vehicle's config. Small drilled holes lose a little to their
rougher relative edge; large well-rounded ports gain a little. Leaving it out
was worth about six points of injector stiffness on the real engine --
enough to move a design from inside its 20-30% band to outside it, which is
exactly the kind of quiet disagreement between two tools that costs an
afternoon to find.

Definition at line 102 of file design.py.

Member Function Documentation

cd()

float feedtwin.engine.design.DischargeModel.cd	(		self,
		float	reynolds,
		*	,
		float | None	pressure = None,
		float | None	temperature = None,
		float | None	diameter = None )

Definition at line 151 of file design.py.

References a_p, a_re, a_t, cd_infinite(), cd_min, max, min, p_ref, t_ref, use_pressure_correction, and use_temperature_correction.

Referenced by feedtwin.engine.balance.SideBalance.effective_area().

cd_infinite()

float feedtwin.engine.design.DischargeModel.cd_infinite	(		self,
		float | None	diameter = None )

High-Reynolds ``Cd`` for a hole of this size.

Definition at line 137 of file design.py.

References cd_inf, cd_inf_max, cd_inf_min_geom, cd_large_hole_log_gain, cd_small_hole_exponent, d_min, d_ref, max, min, and use_geometry_cd.

Referenced by cd().

Member Data Documentation

a_p

float feedtwin.engine.design.DischargeModel.a_p = 0.0

static

Definition at line 125 of file design.py.

Referenced by cd().

a_re

float feedtwin.engine.design.DischargeModel.a_re = 0.0

static

Definition at line 121 of file design.py.

Referenced by cd().

a_t

float feedtwin.engine.design.DischargeModel.a_t = 0.0

static

Definition at line 128 of file design.py.

Referenced by cd().

cd_inf

feedtwin.engine.design.DischargeModel.cd_inf = 0.6

static

Definition at line 120 of file design.py.

Referenced by cd_infinite().

cd_inf_max

feedtwin.engine.design.DischargeModel.cd_inf_max = 0.62

static

Definition at line 134 of file design.py.

Referenced by cd_infinite().

cd_inf_min_geom

feedtwin.engine.design.DischargeModel.cd_inf_min_geom = 0.48

static

Definition at line 135 of file design.py.

Referenced by cd_infinite().

cd_large_hole_log_gain

float feedtwin.engine.design.DischargeModel.cd_large_hole_log_gain = 0.015

static

Definition at line 133 of file design.py.

Referenced by cd_infinite().

cd_min

feedtwin.engine.design.DischargeModel.cd_min = 0.15

static

Definition at line 122 of file design.py.

Referenced by cd().

cd_small_hole_exponent

float feedtwin.engine.design.DischargeModel.cd_small_hole_exponent = 0.20

static

Definition at line 132 of file design.py.

Referenced by cd_infinite().

d_min

float feedtwin.engine.design.DischargeModel.d_min = 4.0e-4

static

Definition at line 131 of file design.py.

Referenced by cd_infinite().

d_ref

float feedtwin.engine.design.DischargeModel.d_ref = 2.0e-3

static

Definition at line 130 of file design.py.

Referenced by cd_infinite().

p_ref

float feedtwin.engine.design.DischargeModel.p_ref = 5.0e6

static

Definition at line 124 of file design.py.

Referenced by engine.layerx.flight.InlineAscent._specific(), and cd().

t_ref

float feedtwin.engine.design.DischargeModel.t_ref = 90.0

static

Definition at line 127 of file design.py.

Referenced by cd().

use_geometry_cd

bool feedtwin.engine.design.DischargeModel.use_geometry_cd = False

static

Definition at line 129 of file design.py.

Referenced by cd_infinite().

use_pressure_correction

bool feedtwin.engine.design.DischargeModel.use_pressure_correction = False

static

Definition at line 123 of file design.py.

Referenced by cd().

use_temperature_correction

bool feedtwin.engine.design.DischargeModel.use_temperature_correction = False

static

Definition at line 126 of file design.py.

Referenced by cd().

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The documentation for this class was generated from the following file:

• lib/feedtwin/feedtwin/engine/design.py