Pub Date : 2016-01-01DOI: 10.6041/J.ISSN.1000-1298.2016.02.005
M. Yang, L. Yan, Yuli Wang, C. Gong, J. Lu
As a basic flow form, free round turbulent jet has been used in various industry fields such as water jet cutting, water cleaning, fuel spray, etc. To understand the development of jet and some of its underlying characteristics, it is crucial that the mechanism of jet instability should be recognized. A robust two-phase flow large eddy simulation (LES) algorithm was applied to predict the liquid instability and the coherent structure of free round turbulent jet. The main objective was to characterize the liquid instability mechanism without resorting stability analysis. Special attention was focused on how the instability and the eddy structure in the near field of round jet were affected by the imposed inlet velocity and disturbance. In this respect, the cases within the range of Re=10000~80000 at various disturbance intensities were tested. Results revealed that the velocity and disturbances played an important role in the stability of liquid jet. The unperturbed liquid core length and scale of surface wave were decreased, and a wide variety of vortexes were produced in the near field of jet with velocity and disturbance intensity increased. The decay rates of average velocity along the central axis of jet were similar under different disturbance intensities at the same Reynolds number (or different Reynolds numbers at the same disturbance intensity). The positive entrainment was enhanced and the radial spread of the jet along the streamwise became more significant with the Reynolds number increased.
{"title":"Instability and interfacial coherent structure of free round turbulent jet","authors":"M. Yang, L. Yan, Yuli Wang, C. Gong, J. Lu","doi":"10.6041/J.ISSN.1000-1298.2016.02.005","DOIUrl":"https://doi.org/10.6041/J.ISSN.1000-1298.2016.02.005","url":null,"abstract":"As a basic flow form, free round turbulent jet has been used in various industry fields such as water jet cutting, water cleaning, fuel spray, etc. To understand the development of jet and some of its underlying characteristics, it is crucial that the mechanism of jet instability should be recognized. A robust two-phase flow large eddy simulation (LES) algorithm was applied to predict the liquid instability and the coherent structure of free round turbulent jet. The main objective was to characterize the liquid instability mechanism without resorting stability analysis. Special attention was focused on how the instability and the eddy structure in the near field of round jet were affected by the imposed inlet velocity and disturbance. In this respect, the cases within the range of Re=10000~80000 at various disturbance intensities were tested. Results revealed that the velocity and disturbances played an important role in the stability of liquid jet. The unperturbed liquid core length and scale of surface wave were decreased, and a wide variety of vortexes were produced in the near field of jet with velocity and disturbance intensity increased. The decay rates of average velocity along the central axis of jet were similar under different disturbance intensities at the same Reynolds number (or different Reynolds numbers at the same disturbance intensity). The positive entrainment was enhanced and the radial spread of the jet along the streamwise became more significant with the Reynolds number increased.","PeriodicalId":35080,"journal":{"name":"农业机械学报","volume":"39 1","pages":"35-44"},"PeriodicalIF":0.0,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86179912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-01-01DOI: 10.6041/J.ISSN.1000-1298.2015.09.048
Sijing Ye, Dehai Zhu, X. Yao, Yan-Li Yue, Jianxi Huang, Lin Li
{"title":"Mobile GIS based approach for collection of crop planting environment data","authors":"Sijing Ye, Dehai Zhu, X. Yao, Yan-Li Yue, Jianxi Huang, Lin Li","doi":"10.6041/J.ISSN.1000-1298.2015.09.048","DOIUrl":"https://doi.org/10.6041/J.ISSN.1000-1298.2015.09.048","url":null,"abstract":"","PeriodicalId":35080,"journal":{"name":"农业机械学报","volume":"46 1","pages":"325-334"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90259767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-01-01DOI: 10.6041/J.ISSN.1000-1298.2015.06.014
J. Cai, J. Pan, A. Guzzomi
{"title":"Pressure fluctuations around volute tongue of centrifugal pump","authors":"J. Cai, J. Pan, A. Guzzomi","doi":"10.6041/J.ISSN.1000-1298.2015.06.014","DOIUrl":"https://doi.org/10.6041/J.ISSN.1000-1298.2015.06.014","url":null,"abstract":"","PeriodicalId":35080,"journal":{"name":"农业机械学报","volume":"10 1","pages":"92-96"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77322791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-01-01DOI: 10.6041/J.ISSN.1000-1298.2015.04.005
H. Quan, Ren-nian Li, Q. Su, W. Han, Lei Jiang, Yi Jin
{"title":"Internal flow characteristic of screw centrifugal pump based on PIV","authors":"H. Quan, Ren-nian Li, Q. Su, W. Han, Lei Jiang, Yi Jin","doi":"10.6041/J.ISSN.1000-1298.2015.04.005","DOIUrl":"https://doi.org/10.6041/J.ISSN.1000-1298.2015.04.005","url":null,"abstract":"","PeriodicalId":35080,"journal":{"name":"农业机械学报","volume":"220 1","pages":"28-32"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77781762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.6041/J.ISSN.1000-1298.2014.07.038
J. Liu, H. Bi, P. Zhu, Jingmei Sun, J. Zhu, T. Chen
The Xylosma racemosum forest located in Huairou District of Beijing was chosen as research objects, texture parameters as well as derivative texture indices of different window sizes from ALOS fusion imagery with resolution of 2.5 m were measured. Stepwise multiple regression models were developed to describe the relationship between textures (including texture parameters and derivative texture indices) and field measurements of stand volume. The main objective was to compare estimation accuracy between model established by texture parameters and that by derivative texture indices, select the most effective Xylosma racemosum stand volume estimate model and select the most effective window size. Results indicate that the value of adjusted R2 of fitting models established by derivative texture indices were better than those of texture parameters at the same window size, the value of adjusted R2 of stand volume model could be improved significantly by combination of texture parameters and derivative texture indices at the same window size, the optimal estimation model of Xylosma racemosum stand volume was obtained when all of the texture parameters and derivative texture indices of all window sizes were introduced into stepwise multiple regression, 11×11 was the optimal window size with the largest adjusted R2 for fitting Xylosma racemosum stand volume by texture parameters and derivative texture indices generated at one single window size.
{"title":"Estimating stand volume of Xylosma racemosum forest based on texture parameters and derivative texture indices of ALOS imagery","authors":"J. Liu, H. Bi, P. Zhu, Jingmei Sun, J. Zhu, T. Chen","doi":"10.6041/J.ISSN.1000-1298.2014.07.038","DOIUrl":"https://doi.org/10.6041/J.ISSN.1000-1298.2014.07.038","url":null,"abstract":"The Xylosma racemosum forest located in Huairou District of Beijing was chosen as research objects, texture parameters as well as derivative texture indices of different window sizes from ALOS fusion imagery with resolution of 2.5 m were measured. Stepwise multiple regression models were developed to describe the relationship between textures (including texture parameters and derivative texture indices) and field measurements of stand volume. The main objective was to compare estimation accuracy between model established by texture parameters and that by derivative texture indices, select the most effective Xylosma racemosum stand volume estimate model and select the most effective window size. Results indicate that the value of adjusted R2 of fitting models established by derivative texture indices were better than those of texture parameters at the same window size, the value of adjusted R2 of stand volume model could be improved significantly by combination of texture parameters and derivative texture indices at the same window size, the optimal estimation model of Xylosma racemosum stand volume was obtained when all of the texture parameters and derivative texture indices of all window sizes were introduced into stepwise multiple regression, 11×11 was the optimal window size with the largest adjusted R2 for fitting Xylosma racemosum stand volume by texture parameters and derivative texture indices generated at one single window size.","PeriodicalId":35080,"journal":{"name":"农业机械学报","volume":"52 1","pages":"245-254"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80823620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1007/978-3-642-37922-2_122
Fei Feng, G. Song, Laihong Shen, J. Xiao
{"title":"Simulation of Bio-syngas Production from Biomass Gasification via Pressurized Interconnected Fluidized Beds","authors":"Fei Feng, G. Song, Laihong Shen, J. Xiao","doi":"10.1007/978-3-642-37922-2_122","DOIUrl":"https://doi.org/10.1007/978-3-642-37922-2_122","url":null,"abstract":"","PeriodicalId":35080,"journal":{"name":"农业机械学报","volume":"9 1","pages":"1145-1155"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88397808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.6041/J.ISSN.1000-1298.2014.07.047
M. Yang, J. Lu, Yuli Wang, C. Gong, L. Yan
Three commonly used two-equation turbulence models were adopted. The computed velocity field was compared with the data from corresponding laser Doppler anemometer measurement to analyze the accuracy of these models. By adjusting the model parameters, the simulation data can fit into the experimental result. The optimal viscosity coefficients Cμ in these used eddy viscosity models were presented. It is shown that the RNG k-e model is more sensitive to Cμ, while the results from Standard k-e model vary almost linearly with the change of the Cμ value. Study on the simulated flow field gives that if the peak of turbulence kinetic energy appears within the radial span, it will affect the velocity distribution along the jet axis; otherwise, it will modify the velocity magnitude. The proposed numerical scheme reduces the physical complexities involved in ultra-high pressure injection process so that it can be applied to archive fast production from relevant CAE workflow.
{"title":"Analysis of eddy viscosity models in predicting flow field of high-speed water jet","authors":"M. Yang, J. Lu, Yuli Wang, C. Gong, L. Yan","doi":"10.6041/J.ISSN.1000-1298.2014.07.047","DOIUrl":"https://doi.org/10.6041/J.ISSN.1000-1298.2014.07.047","url":null,"abstract":"Three commonly used two-equation turbulence models were adopted. The computed velocity field was compared with the data from corresponding laser Doppler anemometer measurement to analyze the accuracy of these models. By adjusting the model parameters, the simulation data can fit into the experimental result. The optimal viscosity coefficients Cμ in these used eddy viscosity models were presented. It is shown that the RNG k-e model is more sensitive to Cμ, while the results from Standard k-e model vary almost linearly with the change of the Cμ value. Study on the simulated flow field gives that if the peak of turbulence kinetic energy appears within the radial span, it will affect the velocity distribution along the jet axis; otherwise, it will modify the velocity magnitude. The proposed numerical scheme reduces the physical complexities involved in ultra-high pressure injection process so that it can be applied to archive fast production from relevant CAE workflow.","PeriodicalId":35080,"journal":{"name":"农业机械学报","volume":"67 1","pages":"306-312"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80271386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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