The Experts below are selected from a list of 15705 Experts worldwide ranked by ideXlab platform
Jinjun Wang - One of the best experts on this subject based on the ideXlab platform.
-
dynamics of vortical structures in Cylinder Wall interaction with moderate gap ratio
Journal of Fluids and Structures, 2013Co-Authors: Guosheng He, Jinjun WangAbstract:Abstract The interaction between the wake of a transverse circular Cylinder and the underlying flat-plate boundary layer with a moderate gap ratio G/D=1.0 is investigated using both hydrogen-bubble-based and PIV-based visualization techniques. The spanwise rollers in the Cylinder wake are found to be capable of inducing secondary vortices in the near-Wall region. The mutual induction from the counter-clockwise rollers, which are closer to the Wall, plays a primary role, so that these secondary vortices present linear lift-up motion at first. Their subsequent evolution dominantly determines the characteristics of the wake/boundary-layer interaction. Two different vortex interaction scenarios are observed: the secondary vortices can be either entrained into the rollers or pushed down towards the Wall. This leads to a rapid three-dimensional destabilization process, through which streamwise vortices are generated. And it is suggested that these streamwise vortices are the dominant structures to promote the following boundary layer transition.
-
Dynamics of vortical structures in Cylinder/Wall interaction with moderate gap ratio
Journal of Fluids and Structures, 2013Co-Authors: Guosheng He, Jinjun WangAbstract:Abstract The interaction between the wake of a transverse circular Cylinder and the underlying flat-plate boundary layer with a moderate gap ratio G/D=1.0 is investigated using both hydrogen-bubble-based and PIV-based visualization techniques. The spanwise rollers in the Cylinder wake are found to be capable of inducing secondary vortices in the near-Wall region. The mutual induction from the counter-clockwise rollers, which are closer to the Wall, plays a primary role, so that these secondary vortices present linear lift-up motion at first. Their subsequent evolution dominantly determines the characteristics of the wake/boundary-layer interaction. Two different vortex interaction scenarios are observed: the secondary vortices can be either entrained into the rollers or pushed down towards the Wall. This leads to a rapid three-dimensional destabilization process, through which streamwise vortices are generated. And it is suggested that these streamwise vortices are the dominant structures to promote the following boundary layer transition.
Guosheng He - One of the best experts on this subject based on the ideXlab platform.
-
dynamics of vortical structures in Cylinder Wall interaction with moderate gap ratio
Journal of Fluids and Structures, 2013Co-Authors: Guosheng He, Jinjun WangAbstract:Abstract The interaction between the wake of a transverse circular Cylinder and the underlying flat-plate boundary layer with a moderate gap ratio G/D=1.0 is investigated using both hydrogen-bubble-based and PIV-based visualization techniques. The spanwise rollers in the Cylinder wake are found to be capable of inducing secondary vortices in the near-Wall region. The mutual induction from the counter-clockwise rollers, which are closer to the Wall, plays a primary role, so that these secondary vortices present linear lift-up motion at first. Their subsequent evolution dominantly determines the characteristics of the wake/boundary-layer interaction. Two different vortex interaction scenarios are observed: the secondary vortices can be either entrained into the rollers or pushed down towards the Wall. This leads to a rapid three-dimensional destabilization process, through which streamwise vortices are generated. And it is suggested that these streamwise vortices are the dominant structures to promote the following boundary layer transition.
-
Dynamics of vortical structures in Cylinder/Wall interaction with moderate gap ratio
Journal of Fluids and Structures, 2013Co-Authors: Guosheng He, Jinjun WangAbstract:Abstract The interaction between the wake of a transverse circular Cylinder and the underlying flat-plate boundary layer with a moderate gap ratio G/D=1.0 is investigated using both hydrogen-bubble-based and PIV-based visualization techniques. The spanwise rollers in the Cylinder wake are found to be capable of inducing secondary vortices in the near-Wall region. The mutual induction from the counter-clockwise rollers, which are closer to the Wall, plays a primary role, so that these secondary vortices present linear lift-up motion at first. Their subsequent evolution dominantly determines the characteristics of the wake/boundary-layer interaction. Two different vortex interaction scenarios are observed: the secondary vortices can be either entrained into the rollers or pushed down towards the Wall. This leads to a rapid three-dimensional destabilization process, through which streamwise vortices are generated. And it is suggested that these streamwise vortices are the dominant structures to promote the following boundary layer transition.
Thomas Keller - One of the best experts on this subject based on the ideXlab platform.
-
Impact of sample dimensions, soil-Cylinder Wall friction and elastic properties of soil on stress field and bulk density in uniaxial compression tests
Soil and Tillage Research, 2019Co-Authors: Renato P. De Lima, Thomas KellerAbstract:Abstract Compressive properties of arable and forest soils are typically derived from data obtained in uniaxial confined compression tests. However, the stress field, final state of compression and thus compressive properties derived from such tests are dependent on sample dimensions, soil-Cylinder Wall friction and soil material properties. In this study, we analysed the stress field and bulk density distribution within a cylindrical soil sample under uniaxial compression, and how these are affected by sample dimension, soil-Cylinder Wall friction and elastic properties of soil. For this, we modelled a uniaxial compression test using the finite element method (FEM) and performed simulations for a range of sample diameter to height ratios (D/h), different values of soil-Wall friction coefficient (μ) and different soil elastic properties (Young’s modulus and Poisson’s ratio). We use experimental data to validate the findings. The results showed a high impact of soil-Cylinder Wall friction on the stress field within the sample. This resulted in stress concentration at the top of sample edges (Walls) and decreasing stresses at the bottom of the sample. However, the relative impact of soil-Wall friction on sample average behaviour decreased with increasing D/h. These results suggest that the effect of soil-Wall friction on sample-average bulk density cannot be neglected unless D/h >8. Correction of bulk density for μ and D/h could be a practical way to compare data obtained in laboratories using different sample sizes.
Evangelos G. Giakoumis - One of the best experts on this subject based on the ideXlab platform.
-
The influence of Cylinder Wall temperature profile on the second-law diesel engine transient response
Applied Thermal Engineering, 2005Co-Authors: Constantine D. Rakopoulos, Evangelos G. GiakoumisAbstract:Abstract A developed software is used to study the effect of the Cylinder Wall temperature profile on the second-law transient performance of a turbocharged diesel engine. The simulation, based on the filling and emptying approach, includes analysis of mechanical friction per degree crank angle, mathematical simulation of the fuel pump, while each equation in the model is solved separately for every Cylinder of the six-Cylinder diesel engine under study. The model is validated against experimental data for various load changes. A second-law analysis is performed for every process of the diesel engine covering its transient operation. The effect of the Cylinder Wall temperature profile on the second-law transient response of the engine is depicted in detailed, multiple diagrams. Special reference is made to the interesting low heat rejection (“adiabatic”) case. It is shown from the analysis that after a ramp increase in load the second-law terms including the various irreversibilities ones, unlike their first law counterparts, are heavily impacted by the Cylinder Wall temperature variation, thus providing an increased potential for extra work recovery. This fact best highlights the results of the second-law analysis and its diversification as compared to the first-law theory.
-
The influence of Cylinder Wall temperature profile on the second-law diesel engine transient response
Applied Thermal Engineering, 2005Co-Authors: Constantine D. Rakopoulos, Evangelos G. GiakoumisAbstract:A developed software is used to study the effect of the Cylinder Wall temperature profile on the second-law transient performance of a turbocharged diesel engine. The simulation, based on the filling and emptying approach, includes analysis of mechanical friction per degree crank angle, mathematical simulation of the fuel pump, while each equation in the model is solved separately for every Cylinder of the six-Cylinder diesel engine under study. The model is validated against experimental data for various load changes. A second-law analysis is performed for every process of the diesel engine covering its transient operation. The effect of the Cylinder Wall temperature profile on the second-law transient response of the engine is depicted in detailed, multiple diagrams. Special reference is made to the interesting low heat rejection (""adiabatic"") case. It is shown from the analysis that after a ramp increase in load the second-law terms including the various irreversibilities ones, unlike their first law counterparts, are heavily impacted by the Cylinder Wall temperature variation, thus providing an increased potential for extra work recovery. This fact best highlights the results of the second-law analysis and its diversification as compared to the first-law theory. © 2004 Elsevier Ltd. All rights reserved
-
Cylinder Wall temperature effects on the transient performance of a turbocharged Diesel engine
Energy Conversion and Management, 2004Co-Authors: Constantine D. Rakopoulos, Evangelos G. Giakoumis, Dimitrios C. RakopoulosAbstract:Developed explicit simulation program is used to study the effect of the Cylinder Wall temperature on the transient performance of a turbocharged Diesel engine. The simulation, based on the filling and emptying approach, provides several innovations, such as detailed analysis of the thermodynamic and dynamic differential equations on a degree crank angle basis, analysis of transient mechanical friction and also a detailed mathematical simulation of the fuel pump. Each equation in the model is solved separately for every Cylinder of the six Cylinder Diesel engine considered. The model is validated against experimental data for various load changes. The effect of the Cylinder Wall temperature on the transient response of the engine is studied and depicted in detailed, multiple diagrams. Special reference is made to the interesting limited cooled (adiabatic) case. It is shown from the analysis that after a ramp increase in load, the speed response as well the other important properties of the engine and turbocharger are marginally impacted by the Cylinder Wall temperature, affected only slightly when an adiabatic Wall configuration is chosen.
Constantine D. Rakopoulos - One of the best experts on this subject based on the ideXlab platform.
-
The influence of Cylinder Wall temperature profile on the second-law diesel engine transient response
Applied Thermal Engineering, 2005Co-Authors: Constantine D. Rakopoulos, Evangelos G. GiakoumisAbstract:Abstract A developed software is used to study the effect of the Cylinder Wall temperature profile on the second-law transient performance of a turbocharged diesel engine. The simulation, based on the filling and emptying approach, includes analysis of mechanical friction per degree crank angle, mathematical simulation of the fuel pump, while each equation in the model is solved separately for every Cylinder of the six-Cylinder diesel engine under study. The model is validated against experimental data for various load changes. A second-law analysis is performed for every process of the diesel engine covering its transient operation. The effect of the Cylinder Wall temperature profile on the second-law transient response of the engine is depicted in detailed, multiple diagrams. Special reference is made to the interesting low heat rejection (“adiabatic”) case. It is shown from the analysis that after a ramp increase in load the second-law terms including the various irreversibilities ones, unlike their first law counterparts, are heavily impacted by the Cylinder Wall temperature variation, thus providing an increased potential for extra work recovery. This fact best highlights the results of the second-law analysis and its diversification as compared to the first-law theory.
-
The influence of Cylinder Wall temperature profile on the second-law diesel engine transient response
Applied Thermal Engineering, 2005Co-Authors: Constantine D. Rakopoulos, Evangelos G. GiakoumisAbstract:A developed software is used to study the effect of the Cylinder Wall temperature profile on the second-law transient performance of a turbocharged diesel engine. The simulation, based on the filling and emptying approach, includes analysis of mechanical friction per degree crank angle, mathematical simulation of the fuel pump, while each equation in the model is solved separately for every Cylinder of the six-Cylinder diesel engine under study. The model is validated against experimental data for various load changes. A second-law analysis is performed for every process of the diesel engine covering its transient operation. The effect of the Cylinder Wall temperature profile on the second-law transient response of the engine is depicted in detailed, multiple diagrams. Special reference is made to the interesting low heat rejection (""adiabatic"") case. It is shown from the analysis that after a ramp increase in load the second-law terms including the various irreversibilities ones, unlike their first law counterparts, are heavily impacted by the Cylinder Wall temperature variation, thus providing an increased potential for extra work recovery. This fact best highlights the results of the second-law analysis and its diversification as compared to the first-law theory. © 2004 Elsevier Ltd. All rights reserved
-
Cylinder Wall temperature effects on the transient performance of a turbocharged Diesel engine
Energy Conversion and Management, 2004Co-Authors: Constantine D. Rakopoulos, Evangelos G. Giakoumis, Dimitrios C. RakopoulosAbstract:Developed explicit simulation program is used to study the effect of the Cylinder Wall temperature on the transient performance of a turbocharged Diesel engine. The simulation, based on the filling and emptying approach, provides several innovations, such as detailed analysis of the thermodynamic and dynamic differential equations on a degree crank angle basis, analysis of transient mechanical friction and also a detailed mathematical simulation of the fuel pump. Each equation in the model is solved separately for every Cylinder of the six Cylinder Diesel engine considered. The model is validated against experimental data for various load changes. The effect of the Cylinder Wall temperature on the transient response of the engine is studied and depicted in detailed, multiple diagrams. Special reference is made to the interesting limited cooled (adiabatic) case. It is shown from the analysis that after a ramp increase in load, the speed response as well the other important properties of the engine and turbocharger are marginally impacted by the Cylinder Wall temperature, affected only slightly when an adiabatic Wall configuration is chosen.
