Based on numerical modelling for two-dimensional flow in which the density of effluent is different from that of environment, the flow and concentration fields are couplingly solved. Through numerical integration the ...Based on numerical modelling for two-dimensional flow in which the density of effluent is different from that of environment, the flow and concentration fields are couplingly solved. Through numerical integration the flow rate and contaminant distributions with different angles and different momentum of effluent can be obtained. The results given in this paper could be a base for quantitative estimation in hydraulic engineering design and assessment and planning of water quality.展开更多
When water flows through a multiple-orifice energy disspator, flow vibration and cavitation may become very important problems. A new kind of the energy dissipator has recieved much attention because of its effectiven...When water flows through a multiple-orifice energy disspator, flow vibration and cavitation may become very important problems. A new kind of the energy dissipator has recieved much attention because of its effectiveness in energy dissipation. In this paper numerical simulations of turbulent flows in a dissipator were presented. The flow was considered to be an asymmetric two-dimensional steady flow. K-Ε turbulent model was used and solution procedure was described. The calculation was performed with different flow conditions. Calculated results of the flow field are compared with experiments. The results demonstrate that turbulent flow through dissipator can be predicted.展开更多
The problem of free surface is one of main difficulties in the numerical calculation of turbulent flow. This paper presents the concept of 'elastic-lid' for the first time, which is used to calculate the stead...The problem of free surface is one of main difficulties in the numerical calculation of turbulent flow. This paper presents the concept of 'elastic-lid' for the first time, which is used to calculate the steady turbulent flow domains with complex free surfaces. This method can be combined with the existing steady turbulence models. Compared with MAC and other unsteady methods, it is simpler and can give us the parameters related to turbulent flow. The method is supported by the techniques of 'block-off' and 'elastic-grid', which can be selected for different problems. Finally, three examples are given to show the application of the 'elastic-lid' method. The calculated results are in good agreement with the measured.展开更多
To predict the temperature field due to heated water discharge, experiment and numerical methods are both usually used. A cubic spline method introduced by Rubin et al. has higher accuracy, but can not be used in non-...To predict the temperature field due to heated water discharge, experiment and numerical methods are both usually used. A cubic spline method introduced by Rubin et al. has higher accuracy, but can not be used in non-linear equations like turbulent model. Authors have built a new scheme of cubic spline for non-linear partial differential equation and presented a SIMPLE-like algorithm for solving k-Ε model. Numerical results were compared with the experimental results. The results compared show that the new cubic spline scheme can be successfully used to nonlinear and strong coupling partial differential equations. The differences between experimental data and numerical results may be resulted from the turbulent model itself, therefore, further investigation is needed for these problems.展开更多
When the self-aeration occurres in steep chutes, there is an equilibrium region of uniform air concentration, because aeration is the result of the combined actions of the turbulence and buoyance. In this paper Wood&#...When the self-aeration occurres in steep chutes, there is an equilibrium region of uniform air concentration, because aeration is the result of the combined actions of the turbulence and buoyance. In this paper Wood's method was improved. The calculating model of the rising velocity of the air bubbles and the turbulent diffusion coefficient was derived. The air concentration distribution formula for upper and lower region was obtained. Results show if the aeration ratio is high, the interaction between air and water should be taken into consideration and the turbulent transport equation be modified properly. The analytical solutions show a good agreement with the measured data.展开更多
文摘Based on numerical modelling for two-dimensional flow in which the density of effluent is different from that of environment, the flow and concentration fields are couplingly solved. Through numerical integration the flow rate and contaminant distributions with different angles and different momentum of effluent can be obtained. The results given in this paper could be a base for quantitative estimation in hydraulic engineering design and assessment and planning of water quality.
文摘When water flows through a multiple-orifice energy disspator, flow vibration and cavitation may become very important problems. A new kind of the energy dissipator has recieved much attention because of its effectiveness in energy dissipation. In this paper numerical simulations of turbulent flows in a dissipator were presented. The flow was considered to be an asymmetric two-dimensional steady flow. K-Ε turbulent model was used and solution procedure was described. The calculation was performed with different flow conditions. Calculated results of the flow field are compared with experiments. The results demonstrate that turbulent flow through dissipator can be predicted.
文摘The problem of free surface is one of main difficulties in the numerical calculation of turbulent flow. This paper presents the concept of 'elastic-lid' for the first time, which is used to calculate the steady turbulent flow domains with complex free surfaces. This method can be combined with the existing steady turbulence models. Compared with MAC and other unsteady methods, it is simpler and can give us the parameters related to turbulent flow. The method is supported by the techniques of 'block-off' and 'elastic-grid', which can be selected for different problems. Finally, three examples are given to show the application of the 'elastic-lid' method. The calculated results are in good agreement with the measured.
文摘To predict the temperature field due to heated water discharge, experiment and numerical methods are both usually used. A cubic spline method introduced by Rubin et al. has higher accuracy, but can not be used in non-linear equations like turbulent model. Authors have built a new scheme of cubic spline for non-linear partial differential equation and presented a SIMPLE-like algorithm for solving k-Ε model. Numerical results were compared with the experimental results. The results compared show that the new cubic spline scheme can be successfully used to nonlinear and strong coupling partial differential equations. The differences between experimental data and numerical results may be resulted from the turbulent model itself, therefore, further investigation is needed for these problems.
文摘When the self-aeration occurres in steep chutes, there is an equilibrium region of uniform air concentration, because aeration is the result of the combined actions of the turbulence and buoyance. In this paper Wood's method was improved. The calculating model of the rising velocity of the air bubbles and the turbulent diffusion coefficient was derived. The air concentration distribution formula for upper and lower region was obtained. Results show if the aeration ratio is high, the interaction between air and water should be taken into consideration and the turbulent transport equation be modified properly. The analytical solutions show a good agreement with the measured data.
