W.S.G. Isaac Newton

For the last 11 weeks, I worked on an internship at Demcon Multiphysics. This is a department of Demcon which works on modelling various physical and engineering problems in the domains of fluid, thermal, structural, electromagnetism, plasma and more. Demcon Multiphysics works on both internal projects for Demcon and projects for external clients. The projects they do therefore range from small projects of a few hours to days to larger projects of weeks to months.

For my internship, I worked on gaining more understanding of the numerical modelling of cross-flow fans. This is a specific type of turbomachinery that has both suction and discharge in the radial direction (see image). This project was created due to an underprediction of fan performance occurring in earlier work for clients.

To gain understanding I did a literature study and CFD modelling of the fan in 2D and 3D. Due to the specific flow field and the interaction the housing has on the flow field, the simulations were transient, meaning the mesh of a rotating region including the blades is rotated every time step.

It was found that the type of turbulence model chosen could have a strong influence on the flow field, which means various alternatives had to be tested.

In the end, using Siemens Star CCM+ and an alternative turbulence model we could get accurate results (within 5%) around the best efficiency point (BEP) of the fan and higher volume flow rates. At volume flow rates below the BEP and the stall region of the fan curve, the simulation would underpredict the performance drastically, following a parabolic shape back down to 0 Pa pressure build instead of building pressure. This region is not fully understood yet, a Detached Eddy Simulation was even done to try and discover what is being missed, but this yielded the same problems. Therefore, this is something that needs to be researched further.

I enjoyed my time at Demcon Multiphysics, it was a nice place to complete my internship. The atmosphere was friendly and there is a strong foundation which encourages learning new things, such as biweekly workshops from other colleagues on certain topics.