The design of sanitary ware not only follows aesthetic criteria but must also be subject to strict regulations that govern its proper functioning. Among these, a sanitary fixture must guarantee a good and effective cleaning of the internal surfaces, making sure that during the drainage phase the water properly removes most of the dirt.
This study aims to analyze possible alternative forms for both the water inlet and the toilet bowl itself, which maximize the surface area of the interior of the toilet wetted by water.
The variables involved are potentially multiple and interconnected: manually exploring all possible values can be a very long and complex work, as well as understanding the effects on the target set.
For this reason we have chosen to use an optimization software that responds to this need: interfacing with the most disparate software you are able to automate the work, analyze the influence of multiple parameters and understand the link between them and the performance you want to improve. The software chosen is IMPROVEit, which thanks to its simple interface allows you to easily perform both the setup phase and the processing of results.
The software is able to internally modify the shape of STL geometries on the basis of parameters set by the user, launch fluid dynamic simulations interfacing with the CFD software FLOW-3D® using the modified geometries, extract the results of the software and process them with appropriate mathematical nodes or invoking Excel to obtain the quantity to be optimized. FLOW-3D® has been chosen for its excellent capabilities, in terms of speed and accuracy, in the calculation of transient and free surface flows.
Three geometric parameters were chosen to vary, so as not to complicate the problem too much: the direction of the inlet, the outlet section of the inlet and the slope of the front part of the sanitary, playing with the curvature present here. Optimisation can certainly be complicated with more time available. The objective is to maximize the wetted surface of the inside of the sanitaryware, calculated as the integral area covered by liquid during the entire discharge time divided by the discharge time itself. Moreover, it has been imposed the constraint that the water must not escape from the upper part of the sanitary, even in small quantities, to discard those solutions that while washing the surface cause unwanted splashes.
The fluid dynamics simulation was set up by initializing the water in the tank upstream of the toilet and setting as boundary conditions the exit from the exhaust pipe and the atmospheric pressure of the air. In this way, the water flow is free to enter freely and naturally into the sanitaryware. The simulation is stopped when the tank is completely empty.
IMPROVEit has the advantage that it does not require knowledge in the field of optimization to be used, as it is able to independently choose the best strategy to achieve the goal. It only requires you to define a budget, which is the time you want to devote to optimization, because the strategy chosen is such as to seek optimal solutions around the end of this period. Since each calculation cycle (variation of the geometries, fluid dynamics simulation and elaboration of the outputs) lasts approximately 40 minutes, a budget of 25 cycles has been chosen, in order to have the result in little more than a day.
Considering that there are 3 variables at play and that the problem is complex, it can be considered a rather challenging case for the optimization software. Nevertheless, IMPROVEit has already been able to propose solutions that increase the surface area of the toilet wetted by water by up to 35%. Moreover, by analysing the panorama of the solutions found, it is possible to better understand the influence of the various factors. It can be seen, in fact, as larger outlet diameters premino because they allow a greater leakage of mass in the unit of time, despite a reduced throttle leads to higher speeds. The direction of the inlet that gives the best results, however, is aligned with the horizontal plane, while the shape of the sanitary has more varied effects, without highlighting such a clear trend.