Near-Field Noise Prediction for Landing Gear Based on Detached Eddy Simulations

2014 ◽  
Vol 472 ◽  
pp. 105-110
Author(s):  
Ning Hu ◽  
Xuan Hao ◽  
Cheng Su ◽  
Wei Min Zhang ◽  
Han Dong Ma
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Sound Pressure ◽  
Near Field ◽  
Separated Flow ◽  
Landing Gear ◽  
Aerodynamic Noise ◽  
Noise Prediction ◽  
Detached Eddy Simulation ◽  
Eddy Simulation

A four-wheel rudimentary landing gear is studied numerically by detached eddy simulation (DES) based on the Spalart-Allmaras turbulence model. The surface sound pressure level and sound pressure spectra are calculated using the obtained unsteady flow field. The investigation shows that DES can describe the steady and unsteady properties in the flow around rudimentary landing gear. It can give reasonable results since the flow around the landing gear is a massive separated flow. The results prove the feasibility of DES type methods in massive separated unsteady flow field and aerodynamic noise prediction for landing gear, and can be used in the study of landing gear noise reduction.

Noise Prediction for Multi-Element Airfoil Based on FW-H Equation

2011 ◽  
Vol 52-54 ◽  
pp. 1388-1393
Author(s):  
Jun Tao ◽  
Gang Sun ◽  
Ying Hu ◽  
Miao Zhang
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Near Field ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Noise Prediction ◽  
Far Field ◽  
Acoustic Analogy ◽  
Acoustic Information ◽  
Good Agreement

In this article, four observation points are selected in the flow field when predicting aerodynamic noise of a multi-element airfoil for both a coarser grid and a finer grid. Numerical simulation of N-S equations is employed to obtain near-field acoustic information, then far-field acoustic information is obtained through acoustic analogy theory combined with FW-H equation. Computation indicates: the codes calculate the flow field in good agreement with the experimental data; The finer the grid is, the more stable the calculated sound pressure level (SPL) is and the more regularly d(SPL)/d(St) varies.

The effect of doors and cavity on the aerodynamic noise of fuselage nose landing gear

2021 ◽  
pp. 1475472X2110032
Author(s):  
Yongfei Mu ◽  
Jie Li ◽  
Wutao Lei ◽  
Daxiong Liao
Keyword(s):  
Separated Flow ◽  
Leading Edge ◽  
Landing Gear ◽  
Aerodynamic Noise ◽  
Sound Waves ◽  
Detached Eddy Simulation ◽  
Airframe Noise ◽  
Interference Phenomenon ◽  
Delayed Detached Eddy Simulation ◽  
The Doors

The aerodynamic noise of landing gears have been widely studied as an important component of the airframe noise. During take-off and landing, there are doors, cavity and fuselage around the landing gear. The noise caused by these aircraft components will interfere with aerodynamic noise generated by the landing gear itself. Hence, paper proposes an Improved Delayed Detached Eddy Simulation (IDDES) method for the investigation of the flow field around a single fuselage nose landing gear (NLG) model and a fuselage nose landing gear model with doors, cavity and fuselage nose (NLG-DCN) respectively. The difference between the two flow fields were analyzed in detail to better understand the influence of these components around the aircraft’s landing gear, and it was found that there is a serious mixing phenomenon among the separated flow from the front doors, the unstable shear layer falling off the leading edge of the cavity and the wake of the main strut which directly leads to the enhancement of the noise levels. Furthermore, after the noise sound waves are reflected by the doors several times, an interference phenomenon is generated between the doors. This interference may be a reason why the tone excited in the cavity is suppressed.

Detached-Eddy Simulations Over a Simplified Landing Gear

2002 ◽  
Vol 124 (2) ◽  
pp. 413-423 ◽  
Author(s):  
L. S. Hedges ◽  
A. K. Travin ◽  
P. R. Spalart
Keyword(s):  
Stokes Equations ◽  
Separated Flow ◽  
Flow Fields ◽  
Equation Model ◽  
Landing Gear ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Navier Stokes Equations ◽  
Instantaneous Flow ◽  
Eddy Simulation

The flow around a generic airliner landing-gear truck is calculated using the methods of Detached-Eddy Simulation, and of Unsteady Reynolds-Averaged Navier-Stokes Equations, with the Spalart-Allmaras one-equation model. The two simulations have identical numerics, using a multi-block structured grid with about 2.5 million points. The Reynolds number is 6×105. Comparison to the experiment of Lazos shows that the simulations predict the pressure on the wheels accurately for such a massively separated flow with strong interference. DES performs somewhat better than URANS. Drag and lift are not predicted as well. The time-averaged and instantaneous flow fields are studied, particularly to determine their suitability for the physics-based prediction of noise. The two time-averaged flow fields are similar, though the DES shows more turbulence intensity overall. The instantaneous flow fields are very dissimilar. DES develops a much wider range of unsteady scales of motion and appears promising for noise prediction, up to some frequency limit.

Unsteady Behaviors of Steam Flow in a Control Valve With T-Junction Discharge Under the Choked Condition: Detached Eddy Simulation and Proper Orthogonal Decomposition

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Peng Wang ◽  
Hongyu Ma ◽  
Yingzheng Liu
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Proper Orthogonal Decomposition ◽  
Control Valve ◽  
Orthogonal Decomposition ◽  
Detached Eddy Simulation ◽  
Flow Passage ◽  
Eddy Simulation ◽  
Periodic Fluctuations ◽  
Proper Orthogonal

Due to the practical space limitation, the control valve in industrial utilities is usually immediately followed by a short flow passage, which would introduce considerable complexity into highly unsteady flow behaviors, along with the flow noise and structure vibration. In the present study, the unsteady behaviors of the steam flow inside a control valve with a T-junction discharge, when the valve operates under the choked condition, are numerically simulated. Toward this end, the detached eddy simulation (DES) is used to capture the spatiotemporally varying flow field in the serpentine flow passage. The results show periodic fluctuations of the aerodynamic forces on the valve spindle and periodic fluctuations of the pressure and flow rate at the two discharge outlets. Subsequently, proper orthogonal decomposition (POD) analysis is conducted using the velocity field and pressure field, identifying, respectively, the dominant coherent structures and energetic pressure fluctuation modes. Finally, the extended-POD method is used to delineate the coupling between the pressure fluctuations with the dominant flow structures superimposed in the highly unsteady flow field. The fourth velocity mode at St = 0.1, which corresponds to the alternating oscillations of the annular wall-attached jet, is determined to cause the periodic flow imbalance at the two discharge outlets, whereas signatures of the first three modes are found to be dissipated in the spherical chamber. Such findings could serve as facts for vibration prediction and optimization design. Particularly, the POD and extended-POD techniques were demonstrated to be effective methodologies for analyzing the highly turbulent flows in engineering fluid mechanics.

Study on flow field and aerodynamic noise of electric vehicle rearview mirror

2021 ◽  
pp. 095440702110228
Author(s):  
Xiaowei Hao ◽  
Zhigang Yang ◽  
Qiliang Li
Keyword(s):  
Flow Field ◽  
Proper Orthogonal Decomposition ◽  
Electric Vehicle ◽  
Sound Pressure ◽  
Pressure Level ◽  
Orthogonal Decomposition ◽  
Aerodynamic Noise ◽  
Turbulent Pressure ◽  
Rearview Mirror ◽  
Proper Orthogonal

With the development of new energy and intelligent vehicles, aerodynamic noise problem of pure electric vehicles at high speed has become increasingly prominent. The characteristics of the flow field and aerodynamic noise of the rearview mirror region were investigated by large eddy simulation, acoustic perturbation equations and reduction order analysis. By comparing the pressure coefficients of the coarse, medium and dense grids with wind tunnel test results, the pressure distribution, and numerical accuracy of the medium grid on the body are clarified. It is shown from the flow field proper orthogonal decomposition of the mid-section that the sum of the energy of the first three modes accounts for more than 16%. Based on spectral proper orthogonal decomposition, the peak frequencies of the first-order mode are 19 and 97 Hz. As for the turbulent pressure of side window, the first mode accounts for approximately 11.3% of the total energy, and its peak appears at 39 and 117 Hz. While the first mode of sound pressure accounts for about 41.7%, and the energy peaks occur at 410 and 546 Hz. Compared with traditional vehicle, less total turbulent pressure level and total sound pressure level are found at current electric vehicle because of the limited interaction between the rearview mirror and A-pillar.

EFFECTS OF BOUNDARY-LAYER THICKNESS ON UNSTEADY FLOW CHARACTERISTICS INSIDE OPEN CAVITIES AT SUBSONIC AND TRANSONIC SPEEDS

2012 ◽  
Vol 19 ◽  
pp. 206-213
Author(s):  
DANG-GUO YANG ◽  
JIAN-QIANG LI ◽  
ZHAO-LIN FAN ◽  
XIN-FU LUO
Keyword(s):  
Boundary Layer ◽  
Unsteady Flow ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Sound Pressure ◽  
Flow Characteristics ◽  
Open Cavity ◽  
Aerodynamic Noise ◽  
Sustained Oscillation ◽  
Cavity Depth

An experimental study was conducted in a 0.6m by 0.6m wind-tunnel to analyze effects of boundary-layer thickness on unsteady flow characteristics inside a rectangular open cavity at subsonic and transonic speeds. The sound pressure level (SPL) distributions at the centerline of the cavity floor and Sound pressure frequency spectrum (SPFS) characteristics on some measurement positions presented herein was obtained with cavity length-to-depth ratio (L/D) of 8 over Mach numbers (Ma) of 0.6 and 1.2 at a Reynolds numbers (Re) of 1.23 × 107 and 2.02 × 107 per meter under different boundary-layer thickness to cavity-depth ratios (δ/D). The experimental angle of attack, yawing and rolling angles were 0°. The results indicate that decrease in δ/D leads to severe flow separation and unsteady pressure fluctuation, which induces increase in SPL at same measurement points inside the cavity at Ma of 0.6. At Ma of 1.2, decrease in δ/D results in enhancing compressible waves. Generally, decrease in δ/D induces more flow self-sustained oscillation frequencies. It also makes severer aerodynamic noise inside the open cavity.

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