Swimming pools are expensive - and not just because of the staff. Heating and water circulation result in high maintenance costs for local authorities. But how much water circulation is really necessary to meet the legal requirements and ensure safe operation? In the past, the calculations for this were based on empirical values. A different approach is to replicate complete water basins as digital twins and run through flow simulations and possible changes. That's cheap, takes little time and can reduce swimming pool costs considerably.
Only at first glance does a swimming pool resemble a large bathtub. But there is always complex technology behind it. Many pumps and filters beneath the swimming pool circulate and clean the water.
"A lot helps a lot" is no longer the modern approach
In the past, pools were often oversized, following the motto "a lot helps a lot". The costs caused by the massive circulation are correspondingly high. Hardly anyone questions whether fewer pumps could also provide the required performance.
Dye tests are carried out prior to commissioning. These are supposed to check the pool hydraulics and achieve coloring within a legally prescribed time. But the depths at which the water circulates and for how long (and is therefore not exchanged and cleaned) is often unknown. Extensive tests to specifically test the direction and flow rate of the jets do not always reflect reality.
Smart City approach: digital twin and simulation
By now, however, scientifically sound and proven calculation methods exist that can fully calculate and visualize water flows even for complex pool geometries. These CFD simulations (Computational Fluid Dynamics) take into account technical variables such as the inflow and outflow volume of the water, jet position and geometry, floor and pool geometry and much more.
Ultimately, the simulation creates a digital twin of the pool, which technically behaves in exactly the same way as the real pool. It can then be extensively modified and adapted. This allows engineers to determine very quickly how fewer or more jets, an improvement of the pool hydraulics and a reduction of the pump power affect the retention time of the water in different areas and heights in the pool. Thanks to an optimized volume flow, less water spills over the edge which reduces noise pollution in the indoor pool. Reducing water circulation saves operating and energy costs. The reduced noise is more comfortable for bathers.
EDAG has the necessary know-how
Currently, there are hardly any engineers on the German market who can run a fully digital pool simulation. However, EDAG has been using flow simulations in the field of automotive engineering very successfully for some time. The pool operator mattiaqua has therefore commissioned the EDAG Group in a pilot project to calculate and optimize the flow situation of the pool in Mainz-Kostheim near Wiesbaden. Using the construction plans and an on-site evaluation, the pool could be fully digitized and then simulated. 
Fewer jets and better circulation
The simulation showed that, despite numerous jets at the edge of the pool, there was a large vortex in one area of the pool where the water remained for longer periods of time than in other areas of the pool. This vortex was not just superficial, but also continued into deeper layers of water. The EDAG engineers were able to solve the problem by switching off specific jets. This optimized the water circulation and prevented the vortex. As a result of successful simulation runs, the circulation of the water could be significantly improved. A dye test after switching off the jets confirmed the improved circulation.
Of course, local authorities are not limited to simulating pools that are already in operation. The calculations are particularly useful for new buildings, as they avoid expensive oversizing. This allows architects to optimize the pool geometry and jet arrangement before construction begins, thus reducing costs during construction and ongoing operation.
Advantages for pool operators
Simulation has numerous advantages for pool operators like Kostheim, especially when construction is still at the planning stage. These are:
- savings on initial and subsequent construction costs
- lower, optimized number of required jet
- exact pump performance without oversizing
- no subsequent corrections to the pool design
- no need to close the pool for flow and dye tests
- savings on ongoing operating costs
- minimized electricity costs for ongoing operation
- no subsequent increase in the required pump capacity
- sustainable operation: reduced energy consumption while maintaining consistent water quality
Further information and downloads
Would you like more detailed information on our digital flow twin? Then do not hesitate to contact Matthias Gaubatz, Head of CAE & Vehicle Safety and Fabian Epple, Sales Manager Vehicle Integration, us! We will provide you with a detailed comparison.
Our white paper "The digital swimming pool - notably reducing pool costs using fluid simulation" gives you in-depth and technical explanations on the optimization of swimming pools. 
