scholarly journals Near-and-far field modeling of advanced tail-rotor noise using source-mode expansions

2019 ◽  
Vol 453 ◽  
pp. 328-354 ◽  
Author(s):  
Michel Roger ◽  
Korcan Kucukcoskun
Keyword(s):  
Far Field ◽  
Rotor Noise ◽  
Field Modeling

Far field modeling of the Mamala Bay outfalls

1998 ◽  
Vol 38 (10) ◽  
pp. 323-330
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Field Model ◽  
Near Field ◽  
Far Field ◽  
Field Modeling ◽  
Visitation Frequency ◽  
Statistical Variation ◽  
Long Time ◽  
Harmonic Average ◽  
Ocean Outfall ◽  
Acoustic Doppler Current Profilers

The results of far field modeling of the wastefield formed by the Sand Island, Honolulu, ocean outfall are presented. A far field model, FRFIELD, was coupled to a near field model, NRFIELD. The input data for the models were long time series of oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers and density stratification measured by thermistor strings. Thousands of simulations were made to predict the statistical variation of wastefield properties around the diffuser. It was shown that the visitation frequency of the wastefield decreases rapidly with distance from the diffuser. The spatial variation of minimum and harmonic average dilutions was also predicted. Average dilution increases rapidly with distance. It is concluded that any impact of the discharge will be confined to a relatively small area around the diffuser and beach impacts are not likely to be significant.

scholarly journals Far Field Modeling of Electromagnetic Time Reversal and Application to Selective Focusing on Small Scatterers

2008 ◽  
Vol 69 (3) ◽  
pp. 830-844 ◽  
Author(s):  
X. Antoine ◽  
B. Pinçon ◽  
K. Ramdani ◽  
B. Thierry
Keyword(s):  
Time Reversal ◽  
Far Field ◽  
Field Modeling ◽  
Small Scatterers

Far-field modeling of obstructed Laguerre–Gauss beams

2020 ◽  
Vol 37 (11) ◽  
pp. C20 ◽  
Author(s):  
Abdelhalim Bencheikh ◽  
Saoussene Chabou ◽  
Ouis Chouaib Boumeddine
Keyword(s):  
Far Field ◽  
Field Modeling

scholarly journals Some Peculiarities of Helicopter Main Rotor Aeroacoustic for Far-Field Observer

2019 ◽  
Vol 213 ◽  
pp. 02048
Author(s):  
Alexander Kusyumov ◽  
Sergey Mikhailov ◽  
Sergey Kusyumov ◽  
Elena Romanova ◽  
Georgios Barakos
Keyword(s):  
Experimental Data ◽  
Cfd Simulation ◽  
Helicopter Rotor ◽  
Test Case ◽  
Far Field ◽  
Main Rotor ◽  
Blade Loading ◽  
Rotor Noise ◽  
Helicopter Main Rotor ◽  
Rotor Acoustics

Mathematical models for helicopter rotor acoustics are usually based on the Ffowcs Williams–Hawkings (FW–H) equation. The level of rotor noise is determined by geometry (thickness noise) of a flying vehicle and distributed blade loading (loading noise). Initially, the FW-H equation was obtained from Euler’s equations and does not depend on the viscosity of flow. In the present work the UH-1H helicopter is considered as a test case for numerical CFD simulation and comparison to experimental data.

Modeling the Praia dos Ingleses submarine outfall, Florianópolis, Santa Catarina, Brazil

2013 ◽  
Vol 67 (8) ◽  
pp. 1832-1840
Author(s):  
J. L. B. Carvalho ◽  
A. Trevisan ◽  
V. Santos ◽  
L. Franklin-Silva ◽  
L. A. Alves
Keyword(s):  
Continuous Monitoring ◽  
Initial Conditions ◽  
Near Field ◽  
Treatment Plant ◽  
Residual Water ◽  
Far Field ◽  
Santa Catarina ◽  
Initial Dilution ◽  
Field Modeling ◽  
New Location

An outfall 1,800 m long was initially proposed by CASAN (Water and Sanitation Company of Santa Catarina) to dispose of treated domestic residual water effluent from Praia dos Ingleses beach. The final plan average flow, estimated for the summer season is 0.1543 m³/s. The characteristics on the near field of the diffuser were calculated using the NRFIELD model supplied by a series of current profiles and density, gathered at the diffuser location between March and April, 2007. Reliable information of raw sewage fecal coliform concentration and nutrients has been supplied by CASAN, based on continuous monitoring of sewage in its treatment plants. The diffuser was designed in such a way that it maximizes the initial dilution allowing the nutrients concentration to comply with legislation limits. However, results showed that the treatment plant should be designed to mainly reduce total phosphorus. A hydrodynamic model was implemented to generate current fields for the far field modeling. Information gathered in the field on variation in water level, wind, and current velocity and direction was used for boundary and/or initial conditions. Then, a Lagrangian advective–diffusive model was used to evaluate the extent of the plumes. The results of far field modeling showed a need to increase the outfall length. A new location 3,300 m from the beach has been proposed.

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