The solutions widely used at present for calculating complicated mine ventilation networks are ones in which resistance of the branches and characteristic parameters of the fans are taken as basic input data. But it i...The solutions widely used at present for calculating complicated mine ventilation networks are ones in which resistance of the branches and characteristic parameters of the fans are taken as basic input data. But it is time and energy consuming to obtain the branch resistance values. A new solution is developed in this paper in which the branch resistance values are obtained through measuring and evaluating the airflow of the whole ventilation network. Theoretical analysis is made of the establishment of a linear equation series with branch resistance as unknown numbers, an equation series for which one, and only one, result of solutions exists. This solution is programmed in C language and passed on a personal computer. The programmed solution programmed proves of practical use, as demonstrated by specific examples. Being different from other solutions, the method takes the branch airflow and fan working points as basic input data, and the present solution is of greater advantage for calculating ventilation networks of mines in operation.展开更多
Different advection schemes and two-equation turbulence closure models based on eddy viscosity concept are used to compute the drag coefficient around a circular cylinder at high Reynolds number (106).The numerical re...Different advection schemes and two-equation turbulence closure models based on eddy viscosity concept are used to compute the drag coefficient around a circular cylinder at high Reynolds number (106).The numerical results from these simulations are compared with each other and with experimental data in order to evaluate the performance of different combinations of advection scheme and two-equation turbulence model.The separate contributions from form drag and friction drag are also ana-lyzed.The computational results show that the widely used standard k-ε turbulence closure is not suitable for such kind of study,while the other two-equation turbulence closure models produce acceptable results.The influence of the different advection schemes on the final results are small compared to that produced by the choice of turbulence closure method. The present study serves as a reference for the choice of advection schemes and turbulence closure models for more complex numerical simulation of the flow around a circular cylinder at high Reynolds number.展开更多
文摘The solutions widely used at present for calculating complicated mine ventilation networks are ones in which resistance of the branches and characteristic parameters of the fans are taken as basic input data. But it is time and energy consuming to obtain the branch resistance values. A new solution is developed in this paper in which the branch resistance values are obtained through measuring and evaluating the airflow of the whole ventilation network. Theoretical analysis is made of the establishment of a linear equation series with branch resistance as unknown numbers, an equation series for which one, and only one, result of solutions exists. This solution is programmed in C language and passed on a personal computer. The programmed solution programmed proves of practical use, as demonstrated by specific examples. Being different from other solutions, the method takes the branch airflow and fan working points as basic input data, and the present solution is of greater advantage for calculating ventilation networks of mines in operation.
基金the support by the National Basic Research Program of China(Nos.2009CB421201,2011CB403501)the National Natural Science Foundation of China(Nos.40876012,41076007)
文摘Different advection schemes and two-equation turbulence closure models based on eddy viscosity concept are used to compute the drag coefficient around a circular cylinder at high Reynolds number (106).The numerical results from these simulations are compared with each other and with experimental data in order to evaluate the performance of different combinations of advection scheme and two-equation turbulence model.The separate contributions from form drag and friction drag are also ana-lyzed.The computational results show that the widely used standard k-ε turbulence closure is not suitable for such kind of study,while the other two-equation turbulence closure models produce acceptable results.The influence of the different advection schemes on the final results are small compared to that produced by the choice of turbulence closure method. The present study serves as a reference for the choice of advection schemes and turbulence closure models for more complex numerical simulation of the flow around a circular cylinder at high Reynolds number.
