airframe¶
-
class
airframe.
Airframe
[source]¶ Bases:
object
-
static
airframe
(source, theta, phi, inputs: openmdao.vectors.default_vector.DefaultVector) → numpy.ndarray[source]¶ Compute airframe noise mean-square acoustic pressure (msap).
- Parameters
source – pyNA component computing noise sources :type source: Source
inputs (openmdao.vectors.default_vector.DefaultVector) – unscaled, dimensional input variables read via inputs[key]
- Returns
msap_af
- Return type
np.ndarray [n_t, settings.N_f]
-
static
landing_gear
(settings: Dict[str, Any], ac: Dict[str, Any], M_0: numpy.float64, c_0: numpy.float64, theta: numpy.float64, phi: numpy.float64, I_landing_gear: numpy.int64, freq: numpy.ndarray) → numpy.ndarray[source]¶ Compute landing gear mean-square acoustic pressure (msap)
- Parameters
settings (Dict[str, Any]) – pyna settings
ac (Dict[str, Any]) – aircraft parameters
M_0 (np.float64) – ambient Mach number [-]
c_0 (np.float64) – ambient speed of sound [m/s]
theta (np.float64) – polar directivity angle [deg]
phi (np.float64) – azimuthal directivity angle [deg]
I_landing_gear (np.int64) – landing gear deflection (0/1) [-]
freq (np.ndarray [settings.N_f]) – 1/3rd octave frequency [Hz]
- Returns
msap_lg
- Return type
np.ndarray [settings.N_f]
-
static
leading_edge_slat
(settings: Dict[str, Any], ac: Dict[str, Any], M_0: numpy.float64, c_0: numpy.float64, rho_0: numpy.float64, mu_0: numpy.float64, theta: numpy.float64, phi: numpy.float64, freq: numpy.ndarray) → numpy.ndarray[source]¶ Compute leading-edge slat mean-square acoustic pressure (msap).
- Parameters
settings (Dict[str, Any]) – pyna settings
ac (Dict[str, Any]) – aircraft parameters
M_0 (np.float64) – ambient Mach number [-]
c_0 (np.float64) – ambient speed of sound [m/s]
rho_0 (np.float64) – ambient density [kg/m3]
mu_0 (np.float64) – ambient dynamic viscosity [kg/m/s]
theta (np.float64) – polar directivity angle [deg]
phi (np.float64) – azimuthal directivity angle [deg]
freq (np.ndarray [settings.N_f]) – 1/3rd octave frequency [Hz]
- Returns
msap_les
- Return type
np.ndarray [settings.N_f]
-
static
trailing_edge_flap
(settings: Dict[str, Any], ac: Dict[str, Any], M_0: numpy.float64, c_0: numpy.float64, theta: numpy.float64, phi: numpy.float64, theta_flaps: numpy.float64, freq: numpy.ndarray) → numpy.ndarray[source]¶ Compute trailing-edge flap mean-square acoustic pressure (msap).
- Parameters
settings (Dict[str, Any]) – pyna settings
ac (Dict[str, Any]) – aircraft parameters
M_0 (np.float64) – ambient Mach number [-]
c_0 (np.float64) – ambient speed of sound [m/s]
theta (np.float64) – polar directivity angle [deg]
phi (np.float64) – azimuthal directivity angle [deg]
theta_flaps (np.float64) – flap deflection angle [deg]
freq (np.ndarray [settings.N_f]) – 1/3rd octave frequency [Hz]
- Returns
msap_tef
- Return type
np.ndarray [settings.N_f]
-
static
trailing_edge_horizontal_tail
(settings: Dict[str, Any], ac: Dict[str, Any], M_0: numpy.float64, c_0: numpy.float64, rho_0: numpy.float64, mu_0: numpy.float64, theta: numpy.float64, phi: numpy.float64, freq: numpy.ndarray) → numpy.ndarray[source]¶ Compute horizontal tail trailing edge mean-square acoustic pressure (msap).
- Parameters
settings (Dict[str, Any]) – pyna settings
ac (Dict[str, Any]) – aircraft parameters
M_0 (np.float64) – ambient Mach number [-]
c_0 (np.float64) – ambient speed of sound [m/s]
rho_0 (np.float64) – ambient density [kg/m3]
mu_0 (np.float64) – ambient dynamic viscosity [kg/m/s]
theta (np.float64) – polar directivity angle [deg]
phi (np.float64) – azimuthal directivity angle [deg]
freq (np.ndarray [settings.N_f]) – 1/3rd octave frequency [Hz]
- Returns
msap_h
- Return type
np.ndarray [settings.N_f]
-
static
trailing_edge_vertical_tail
(settings: Dict[str, Any], ac: Dict[str, Any], M_0: numpy.float64, c_0: numpy.float64, rho_0: numpy.float64, mu_0: numpy.float64, theta: numpy.float64, phi: numpy.float64, freq: numpy.ndarray) → numpy.ndarray[source]¶ Compute vertical tail trailing edge mean-square acoustic pressure (msap).
- Parameters
settings (Dict[str, Any]) – pyna settings
ac (Dict[str, Any]) – aircraft parameters
M_0 (np.float64) – ambient Mach number [-]
c_0 (np.float64) – ambient speed of sound [m/s]
rho_0 (np.float64) – ambient density [kg/m3]
mu_0 (np.float64) – ambient dynamic viscosity [kg/m/s]
theta (np.float64) – polar directivity angle [deg]
phi (np.float64) – azimuthal directivity angle [deg]
freq (np.ndarray [settings.N_f]) – 1/3rd octave frequency [Hz]
- Returns
msap_h
- Return type
np.ndarray [settings.N_f]
-
static
trailing_edge_wing
(settings: Dict[str, Any], ac: Dict[str, Any], M_0: numpy.float64, c_0: numpy.float64, rho_0: numpy.float64, mu_0: numpy.float64, theta: numpy.float64, phi: numpy.float64, freq: numpy.ndarray) → numpy.ndarray[source]¶ Compute wing trailing edge mean-square acoustic pressure (msap).
- Parameters
settings (Dict[str, Any]) – pyna settings
ac (Dict[str, Any]) – aircraft parameters
M_0 (np.float64) – ambient Mach number [-]
c_0 (np.float64) – ambient speed of sound [m/s]
rho_0 (np.float64) – ambient density [kg/m3]
mu_0 (np.float64) – ambient dynamic viscosity [kg/m/s]
theta (np.float64) – polar directivity angle [deg]
phi (np.float64) – azimuthal directivity angle [deg]
freq (np.ndarray [settings.N_f]) – 1/3rd octave frequency [Hz]
- Returns
msap_w
- Return type
np.ndarray [n_t, settings.N_f]
-
static
theory¶
The Fink method is used to assess airframe noise. The general equation for the mean-square acoustic pressure for the aircraft noise components is:
This equation is applied to the individual noise source contributions (denoted by subscript comp), namely wing trailing edge (including main wing, horizontal and vertical tail), leading edge slat, trailing edge flap and landing gear noise (including main and nose gear).
Wing trailing edge noise¶
The equations in this section are applicable to the main wing, horizontal tail or vertical tail surface (denoted by the subscript x). The acoustic power for trailing edge noise is given by:
In this equation, the constant \(K_{xte} = 7.075\cdot 10^{-6}\) for an aerodynamically clean wing configuration and \(K_{xte} = 4.464\cdot 10^{-5}\) for non-clean configuration. The boundary layer thickness at the wing trailing edge in this equation is given by:
where \(A_w\) and \(b_w\) are the wing area and span of the respective wing element. The spectral distribution function, \(F_{xte}(S_{xte})\), is given by:
The directivity function, \(D_{xte}\), the Strouhal number, \(S_{xte}\), and the spectral distribution function, \(F_{xte}(S_{xte})\), are given by:
Leading edge slat¶
The noise from the leading edge slats has 2 components, because of 2 different noise generating mechanisms. Firstly, an increase in the main wing trailing edge noise, because of the change in boundary layer thickness (component 1), and secondly, the noise generated by the slat itself (component 2). The noise power of both components is equal to \(\Pi^*_{les,1} = \Pi^*_{les,2} = 4.464\cdot 10^{-5} M_0^5 \delta_{wte}^*\), where the boundary layer thickness of the main wing, \(\delta_{wte}^*\), is given by the equation in the wing section. The directivity function, \(D_{les}\), of both noise components is equal and given by the same equation from the wing section. The spectral distribution function, \(F_{les}\), is given by:
where the spectrum functions \(S_{les,1} = S_{les,2}\) are given by the same equation from the wing section.
Trailing edge flaps¶
The noise power of the trailing edge flaps depends on the number of slots and is given by:
The spectral distribution function, \(F_{tef}\), for single, double and triple slotted flaps is given by:
The directivity function, \(D_{tef}\), and the Strouhal number, \(S_{tef}\), are given by:
Landing gear¶
If the landing gear is extracted, the noise for each landing gear (i.e. main gear, nose gear) consists of wheel-noise and strut-noise. The noise power for the landing gear noise is given by:
The spectral distribution function, \(F_{lg}\), for the landing gear noise is given by:
The directivity function, \(D_{lg}\), and the Strouhal number, \(S_{lg}\), for the landing gear noise are given by:
Combining the aircraft noise components¶
The total mean-square acoustic pressure of the aircraft noise is given by the sum of the individual components:.
HSR suppression¶
An airframe suppression factor, \(\sigma\), as function of frequency, \(f\), and polar directivity angle, \(\theta\) is applied to the total mean-square acoustic pressure: