eDART uses a Computational Fluid Dynamics packaged called FloEFD. FloEFD is embedded in SolidWorks and works directly on the solid model – no negative regions for the fluid need to be created. The finite volume mesh is fully controllable and uses a structured non-body fitted hex mesh. Where the cells intersect the solid boundary, what is termed partial cells are created and a proprietary modified wall function is employed to deal with the boundary layer – both laminar and turbulent regimes may exist in the same model. Simply, boundary conditions are applied and in an iterative manner, the computer converges upon a flow solution. eDART uses normal water for most of its analyses to give an understanding of flow patterns – shown with velocity and pressure cut plots and flow trajectories – and calculate pertinent variables and then modifies the presented results by using empirical functions to deal with factors such as aeration and solids concentration.
Back Pressure Pipe
In a mineral concentrator the crushed ore is passed through a cascading system of floatation machines. eDART valves are located between each cell to control the flow and are subjected to the pressure drop which is a function of the height between the two, aeration in both, vertical head and density change should there be any feed introduced to the process, however on the last cell there is a significant pressure drop across the valve. Back pressure pipes, otherwise known as goosenecks or riser pipes, are used in this case to represent another cell so the valve does not have to be specially designed for this increased pressure drop. The resulting reduction in step for the last cell before the sump can be used to reduce the overall height of the bank or allow for another piece of equipment to be used like a metallurgical sampler. FloEFD is used to determine throat diameters and discharge height in these back pressure pipes.
eDART uses FloEFD to model inlets and outlets of distribution and splitter boxes to optimise the design and get good mixing and even flow from the outlets. Good box design will often have a dropbox in the inlet chamber to cushion the inlet flow if fed from the top, an underflow weir to the boiling chamber and an overflow weir which can be split easily to achieve the desired output.