CFD Application for Sand Separation Pit
Posted on April 21, 2026 Computational Fluid Dynamics Separation Water
The application of CFD to liquid flows with suspended solids can be especially useful in numerous water-based processes. One particular application was for sand separation in a manure handling system. Of particular interest in this situation was whether impeller mixers would be able to keep fine sand particles in suspension in a sand separation pit with an attached pump box, and what the settling rate of coarser sand particles would be within the pit.
A model of the sand pit and the impellers was created and the actual sand particle size distribution was represented using several discrete sand particle sizes. The impellers were modeled as shrouded cylindrical fan elements and then simulations with the Eulerian mixture model were conducted. Based on these simulations, it was determined that fine sand particles would remain in suspension and could be pumped out, while particles larger than a certain size would settle out in the middle of the pit.
The simulations were able to predict the settling rate of these larger particles and thus the client was able to determine how often the pit would need to be manually cleaned out to remove the settled sand. Based on these numbers, the client was able to recommend a reasonable clean-out schedule rather than a complete redesign of the pit, which led to significant cost savings.
In addition, further studies were carried out to determine the optimal size and locations for openings between the pump box and the main pit so that pumping requirements could be achieved, and finally the average residence time of the flow into the pit was determined to monitor the settling of particles that could not be tolerated in the stream that was being pumped out of the pit. This information allowed the client to confidently recommend a pump box design that would not jeopardize pump integrity.
This case study again illustrates the benefit of CFD simulations for the analysis of difficult industrial problems which required realistic estimates of important processing criteria.