A model-scale test with single-stream nozzle exhaust geometries was carried out at the anechoic chamber of Beihang University in Beijing, China. The spectral characteristics are investigated, and the effects of the fo...A model-scale test with single-stream nozzle exhaust geometries was carried out at the anechoic chamber of Beihang University in Beijing, China. The spectral characteristics are investigated, and the effects of the following parametric variations are reported in this paper: impact of nozzle operating conditions on spectra; impact of the presence of a plug; and effectiveness of chevron configurations for noise mitigation. The measurement shows that the change of pressure values has more impact on spectra than the change of temperature values. The spectral change due to pressure is shown at all band numbers for unheated conditions whereas it is more pronounced at highfrequency ranges for heated conditions. An impact of the presence of a plug is also clearly observed.The reduction of noise is moderate up to band number of 35, and becomes more significant at higher band numbers. It is observed that chevron nozzles are more efficient at high pressure and temperature values. It is expected that the quantified analysis will be used to develop an empirical model of single jet noise, which will be the baseline for the development of prediction of noise from turbofan engines of high bypass ratios.展开更多
In this paper, we constructed the halophyte Mesocosm experimental group which was used as a substrate material that consisted of tidal flat and dredged sediment. Depending on whether the ingredients of vegetation and ...In this paper, we constructed the halophyte Mesocosm experimental group which was used as a substrate material that consisted of tidal flat and dredged sediment. Depending on whether the ingredients of vegetation and substrate material of Mesocosm, we constructed Mesocosm A (tidal flat sediment + Salicornia herbecea), Mesocosm B (only dredged sediment), Mesocosm C (dredged sediment + Salicornia herbecea). Monitoring was carried out of seawater quality factors (Chemical Oxygen Demand (COD), Total Nitrogen (T-N), Total Phosphorus (T-P), temperature, salinity), sediment factors (Chemical Oxygen Demand (COD), Total (T-N), Total Phosphorus (T-P) and growth of Salricornia herbecea) in each Mesocosm. Habitat Stability Index of vegetation was calculating by using the monitoring results. HSI of Mesocosm C was calculated from 0.87 to 0.95 as compared to the relatively high HSI Mesocosm A, it was evaluated to be able to be used in the restoration of the coastal salt marsh with dredged sediment.展开更多
文摘A model-scale test with single-stream nozzle exhaust geometries was carried out at the anechoic chamber of Beihang University in Beijing, China. The spectral characteristics are investigated, and the effects of the following parametric variations are reported in this paper: impact of nozzle operating conditions on spectra; impact of the presence of a plug; and effectiveness of chevron configurations for noise mitigation. The measurement shows that the change of pressure values has more impact on spectra than the change of temperature values. The spectral change due to pressure is shown at all band numbers for unheated conditions whereas it is more pronounced at highfrequency ranges for heated conditions. An impact of the presence of a plug is also clearly observed.The reduction of noise is moderate up to band number of 35, and becomes more significant at higher band numbers. It is observed that chevron nozzles are more efficient at high pressure and temperature values. It is expected that the quantified analysis will be used to develop an empirical model of single jet noise, which will be the baseline for the development of prediction of noise from turbofan engines of high bypass ratios.
文摘In this paper, we constructed the halophyte Mesocosm experimental group which was used as a substrate material that consisted of tidal flat and dredged sediment. Depending on whether the ingredients of vegetation and substrate material of Mesocosm, we constructed Mesocosm A (tidal flat sediment + Salicornia herbecea), Mesocosm B (only dredged sediment), Mesocosm C (dredged sediment + Salicornia herbecea). Monitoring was carried out of seawater quality factors (Chemical Oxygen Demand (COD), Total Nitrogen (T-N), Total Phosphorus (T-P), temperature, salinity), sediment factors (Chemical Oxygen Demand (COD), Total (T-N), Total Phosphorus (T-P) and growth of Salricornia herbecea) in each Mesocosm. Habitat Stability Index of vegetation was calculating by using the monitoring results. HSI of Mesocosm C was calculated from 0.87 to 0.95 as compared to the relatively high HSI Mesocosm A, it was evaluated to be able to be used in the restoration of the coastal salt marsh with dredged sediment.
