The characteristics of swirler flow field, including cold flow field and combustion flow field, in gas tur- bine combustor with two-stage swirler are studied by using particle image velocimetry （PIV）. Velocity compo...The characteristics of swirler flow field, including cold flow field and combustion flow field, in gas tur- bine combustor with two-stage swirler are studied by using particle image velocimetry （PIV）. Velocity compo- nents, fluctuation velocity, Reynolds stress and recirculation zone length are obtained, respectively. Influences of geometric parameter of primary hole, arrangement of primary hole, inlet air temperature, first-stage swirler an- gle and fuel/air ratio on flow field are investigated, respectively. The experimental results reveal that the primary recirculation zone lengths of combustion flow field are shorter than those of cold flow field, and the primary reeir- culation zone lengths decrease with the increase of inlet air temperature and fuel/air ratio. The change of the geo- metric parameter of primary hole casts an important influence on the swirler flow field in two-stage swirler com- bustor.展开更多
Wind plays an important role in hydrodynamic processes such as the expansion of Changjiang （Yangtze） River Diluted Water （CDW）, and shelf circulation in the Changjiang estuary. Thus, it is essential to include win...Wind plays an important role in hydrodynamic processes such as the expansion of Changjiang （Yangtze） River Diluted Water （CDW）, and shelf circulation in the Changjiang estuary. Thus, it is essential to include wind in the numerical simulation of these phenomena. Synthetic aperture radar （SAR） with high resolution and wide spatial coverage is valuable for measuring spatially inhomogeneous ocean surface wind fields. We have collected 87 ERS-2 SAR images with wind-induced streaks that cover the Cbangjiang coastal area, to verify and improve the validity of wind direction retrieval using the 2D fast Fourier transform method. We then used these wind directions as inputs to derive SAR wind speeds using the C-band model. To demonstrate the applicability of the algorithms, we validated the SAR-retrieved wind fields using QuikSCAT measurements and the atmospheric Weather Research Forecasting model. In general, we found good agreement between the datasets, indicating the reliability and applicability of SAR- retrieved algorithms under different atmospheric conditions. We investigated the main error sources of this process, and conducted sensitivity analyses to estimate the wind speed errors caused by the effect of speckle, uncertainties in wind direction, and inaccuracies in the normalized radar cross section. Finally, we used the SAR-retrieved wind fields to simulate the salinity distribution off the Changjiang estuary. The findings of this study will be valuable for wind resource assessment and the development of future numerical ocean models based on SAR images.展开更多
In this paper the results of an experimental investigation, finalized to analyze the effect of roughness elements on the Oscillatory Boundary Layer （OBL）, were presented and discussed. These experiments can be usefu...In this paper the results of an experimental investigation, finalized to analyze the effect of roughness elements on the Oscillatory Boundary Layer （OBL）, were presented and discussed. These experiments can be useful for the characterization of the complex hydrodynamic mechanisms in coastal environment, where the bottom boundary layer is very often subject to momentum exchange processes due to the presence of macro-structures on the bottom able to strongly influence and modify its own structure. In this investigation, experiments were performed in an oscillating water tunnel, covering a range of frequencies to from 0.646 up to 2.319 rad.s^-1. The roughness elements were modelled by mean of a matrix of stiff cylinders arranged on the bottom of the tunnel and two densities of cylinders were considered, corresponding to low and high density respectively. Velocity measurements were obtained by 2C DPIV （2 Component Digital Particle Image Velocimetry） technique. A detailed visualization of the flow through adjacent cylinders, including scalar velocity maps and streamlines are presented. Furthermore phase-averaged velocity distributions are here provided. Moreover, root-mean-squared velocities are considered and an empirical relation between （1） the root-mean-squared velocities and the distance from the bottom; （2） the velocity attenuation coefficient and the Reynolds number is obtained for both the considered configurations.展开更多
By constructing a Gray map, a class of constacyclic codes over ring R = R＋ vR is studied. Using cyclic codes and negacyclic codes of length p^s over ring R, the structure of （1 - 2v）-constacyclic codes and dual cod...By constructing a Gray map, a class of constacyclic codes over ring R = R＋ vR is studied. Using cyclic codes and negacyclic codes of length p^s over ring R, the structure of （1 - 2v）-constacyclic codes and dual codes of length p^s over ring R are given, the Gray images of （1 - 2v）-constacyclic codes in a particular case are also studied. It is shown that linear codes of length pS over ring R are （1 -2v）-constacyclic codes if and only if their Gray images are distance-invariant cyclic codes of length 2p^s over ring R.展开更多
Particle Imaging Velocimetry （PIV） is utilized to investigate the flow structures of an oscillating cylinder attached to a flexible tail. At the same oscillation frequency and amplitude, the mean streamwise velocity...Particle Imaging Velocimetry （PIV） is utilized to investigate the flow structures of an oscillating cylinder attached to a flexible tail. At the same oscillation frequency and amplitude, the mean streamwise velocity along the wake central-line and the mean vertical velocity around the trailing edge of the flexible tail can be greatly increased with the tail length. Meanwhile, the longer the flexible tail is, the larger its deformation is. In order to study the influence of flexible tail length on the wake pattern of the experimental model, the relationships between the swirling strength Aci of vortex structure near the tail end and the velocity of tail trailing edge have been revealed. Moreover, the convection tracks and the Aci of vortex cores for different flexible tails are discussed.展开更多
基金Supported by the National Natural Science Foundation of China(50906040)the Nanjing University of Aeronautics and Astronautics Research Funding(NZ2012107,NS2010052)~~
文摘The characteristics of swirler flow field, including cold flow field and combustion flow field, in gas tur- bine combustor with two-stage swirler are studied by using particle image velocimetry （PIV）. Velocity compo- nents, fluctuation velocity, Reynolds stress and recirculation zone length are obtained, respectively. Influences of geometric parameter of primary hole, arrangement of primary hole, inlet air temperature, first-stage swirler an- gle and fuel/air ratio on flow field are investigated, respectively. The experimental results reveal that the primary recirculation zone lengths of combustion flow field are shorter than those of cold flow field, and the primary reeir- culation zone lengths decrease with the increase of inlet air temperature and fuel/air ratio. The change of the geo- metric parameter of primary hole casts an important influence on the swirler flow field in two-stage swirler com- bustor.
基金Supported by the National Basic Research Program of China(973 Program)(No.2010CB951204)the State Key Laboratory of Estuarine and Coastal Research grant(No.SKLEC-2012KYYW02)
文摘Wind plays an important role in hydrodynamic processes such as the expansion of Changjiang （Yangtze） River Diluted Water （CDW）, and shelf circulation in the Changjiang estuary. Thus, it is essential to include wind in the numerical simulation of these phenomena. Synthetic aperture radar （SAR） with high resolution and wide spatial coverage is valuable for measuring spatially inhomogeneous ocean surface wind fields. We have collected 87 ERS-2 SAR images with wind-induced streaks that cover the Cbangjiang coastal area, to verify and improve the validity of wind direction retrieval using the 2D fast Fourier transform method. We then used these wind directions as inputs to derive SAR wind speeds using the C-band model. To demonstrate the applicability of the algorithms, we validated the SAR-retrieved wind fields using QuikSCAT measurements and the atmospheric Weather Research Forecasting model. In general, we found good agreement between the datasets, indicating the reliability and applicability of SAR- retrieved algorithms under different atmospheric conditions. We investigated the main error sources of this process, and conducted sensitivity analyses to estimate the wind speed errors caused by the effect of speckle, uncertainties in wind direction, and inaccuracies in the normalized radar cross section. Finally, we used the SAR-retrieved wind fields to simulate the salinity distribution off the Changjiang estuary. The findings of this study will be valuable for wind resource assessment and the development of future numerical ocean models based on SAR images.
文摘In this paper the results of an experimental investigation, finalized to analyze the effect of roughness elements on the Oscillatory Boundary Layer （OBL）, were presented and discussed. These experiments can be useful for the characterization of the complex hydrodynamic mechanisms in coastal environment, where the bottom boundary layer is very often subject to momentum exchange processes due to the presence of macro-structures on the bottom able to strongly influence and modify its own structure. In this investigation, experiments were performed in an oscillating water tunnel, covering a range of frequencies to from 0.646 up to 2.319 rad.s^-1. The roughness elements were modelled by mean of a matrix of stiff cylinders arranged on the bottom of the tunnel and two densities of cylinders were considered, corresponding to low and high density respectively. Velocity measurements were obtained by 2C DPIV （2 Component Digital Particle Image Velocimetry） technique. A detailed visualization of the flow through adjacent cylinders, including scalar velocity maps and streamlines are presented. Furthermore phase-averaged velocity distributions are here provided. Moreover, root-mean-squared velocities are considered and an empirical relation between （1） the root-mean-squared velocities and the distance from the bottom; （2） the velocity attenuation coefficient and the Reynolds number is obtained for both the considered configurations.
基金supported by the National Natural Science Foundation of China under Grant No.61370089
文摘By constructing a Gray map, a class of constacyclic codes over ring R = R＋ vR is studied. Using cyclic codes and negacyclic codes of length p^s over ring R, the structure of （1 - 2v）-constacyclic codes and dual codes of length p^s over ring R are given, the Gray images of （1 - 2v）-constacyclic codes in a particular case are also studied. It is shown that linear codes of length pS over ring R are （1 -2v）-constacyclic codes if and only if their Gray images are distance-invariant cyclic codes of length 2p^s over ring R.
基金supported by the National Natural Science Foundation of China (Grant No. 10832001)the Innovation Foundation of BUAA for PhD Graduates
文摘Particle Imaging Velocimetry （PIV） is utilized to investigate the flow structures of an oscillating cylinder attached to a flexible tail. At the same oscillation frequency and amplitude, the mean streamwise velocity along the wake central-line and the mean vertical velocity around the trailing edge of the flexible tail can be greatly increased with the tail length. Meanwhile, the longer the flexible tail is, the larger its deformation is. In order to study the influence of flexible tail length on the wake pattern of the experimental model, the relationships between the swirling strength Aci of vortex structure near the tail end and the velocity of tail trailing edge have been revealed. Moreover, the convection tracks and the Aci of vortex cores for different flexible tails are discussed.
