The first part of this study is focused on the numerical modelling and experimental investigation of transonic flow through a 2D model of the male rotor-housing gap in a dry screw compressor.Numerical simulations of t...The first part of this study is focused on the numerical modelling and experimental investigation of transonic flow through a 2D model of the male rotor-housing gap in a dry screw compressor.Numerical simulations of the clearance flow are performed with the help of the in-house compressible Navier-Stokes solver.Experimental measurements based on the Schlieren method in Toepler configuration are carried out.The objective of the second part of the study is to derive the analytical solution of gas microflow development in a gap between two parallel plates.The microflow is assumed to be laminar,incompressible and the velocity slip boundary conditions are considered at the walls.The constant velocity profile is prescribed at the inlet.For the mathematical description of the problem,the Oseen equation is used.The analytical results are compared with the numerical ones obtained using the developed incompressible Navier-Stokes solver including the slip flow boundary conditions.展开更多
Using data from direct numerical simulation （DNS） of incompressible and compressible channel flow, we develop a method of sub-ensemble decomposition to investigate the pressure gradient effect on the Karman constant...Using data from direct numerical simulation （DNS） of incompressible and compressible channel flow, we develop a method of sub-ensemble decomposition to investigate the pressure gradient effect on the Karman constant and the additive constant B characterizing the mean velocity profile （MVP）. The sub-ensemble decomposition is defined according to the magnitude of vertical fluctuation velocity, which mimics coherent motions like ejection and sweep. DNS data analysis shows that each sub-ensemble displays a distinct Karman constant, with a variation which mimics effects of pressure gradient. The latter is demonstrated by a relation between sub-ensembles＇ km and Bm similar to empirical data under various pressure gradients. A set of global parameters, k0-pg=0.39 ＆ B0-pg=5.5, are then derived for interpreting two constants observed by Nagib et al.展开更多
基金supported by the grant GACR 101/08/0623 of the Czech Science Foundation and by the research project MSM4977751303 of the Ministry of Education,Youth and Sports of the Czech Republic
文摘The first part of this study is focused on the numerical modelling and experimental investigation of transonic flow through a 2D model of the male rotor-housing gap in a dry screw compressor.Numerical simulations of the clearance flow are performed with the help of the in-house compressible Navier-Stokes solver.Experimental measurements based on the Schlieren method in Toepler configuration are carried out.The objective of the second part of the study is to derive the analytical solution of gas microflow development in a gap between two parallel plates.The microflow is assumed to be laminar,incompressible and the velocity slip boundary conditions are considered at the walls.The constant velocity profile is prescribed at the inlet.For the mathematical description of the problem,the Oseen equation is used.The analytical results are compared with the numerical ones obtained using the developed incompressible Navier-Stokes solver including the slip flow boundary conditions.
基金supported by the National Natural Science Foundation of China (Grant No. 90716008 and 10921202)the National Basic Research Program of China (Grant No. 2009CB724100)
文摘Using data from direct numerical simulation （DNS） of incompressible and compressible channel flow, we develop a method of sub-ensemble decomposition to investigate the pressure gradient effect on the Karman constant and the additive constant B characterizing the mean velocity profile （MVP）. The sub-ensemble decomposition is defined according to the magnitude of vertical fluctuation velocity, which mimics coherent motions like ejection and sweep. DNS data analysis shows that each sub-ensemble displays a distinct Karman constant, with a variation which mimics effects of pressure gradient. The latter is demonstrated by a relation between sub-ensembles＇ km and Bm similar to empirical data under various pressure gradients. A set of global parameters, k0-pg=0.39 ＆ B0-pg=5.5, are then derived for interpreting two constants observed by Nagib et al.
