Dishwasher performance is crucial for efficient and thorough cleaning, especially in modern households and industrial applications. Simulating the internal water dynamics allows engineers to optimize nozzle placement, spray patterns, and flow rates, ensuring effective water coverage across all dish surfaces. This approach not only improves cleaning efficiency but also helps reduce water and energy consumption. With shonDy, these optimizations can be achieved quickly and accurately, making it an essential tool for designing and refining dishwasher systems.
Case description
Geometry
The dishwasher geometry in this case is based on a publicly available design from GrabCAD, representing a classic, older-style model—dare we say, archaic. While it doesn’t reflect the latest innovations, this geometry is ideal for showcasing shonDy’s capabilities. Its simplicity highlights the starting points of an optimization process and how shonDy can drive improvements. Key features such as spray arm optimization, water distribution, and coverage analysis demonstrate how shonDy delivers fast, precise results.
In addition to the basic geometry, we incorporated several enhancements to enrich the simulation. These include two additional spray arms in the upper compartment, a ceiling spray, and an updated dishwasher floor designed for improved water management. Of course, no dishwasher simulation would be complete without dishes—strategically placed to evaluate water coverage and cleaning efficiency. These additions showcase how shonDy handles complex configurations and provides insights for optimization.
Case set-up
The simulation covers a total physical runtime of 17 seconds, accurately modeling the dishwasher’s alternating spray system. In this setup, the lower spray arm operates exclusively from 0 to 10 seconds, while the upper spray arms and ceiling spray take over from 10 to 17 seconds. The rotation speeds are set at 45 RPM for the spray arms and 135 RPM for the ceiling spray, replicating realistic operating conditions. The particle radius of the fluid particles was set to 0.0004 m.
Inlets and Outlet handling
Inlets - Lower Spray Arm
The spray arm nozzles are modeled with 10 distinct inlets, each with a radius of 0.002 m. The central 8 nozzles primarily face upward, with a slight side tilt, alternating their angles by ±6° in the x-z plane for better coverage.
The two edge inlets have specialized roles:
- One is oriented upward and tangential to the spray arm, simulating the nozzle responsible for generating the rotational impulse.
- The other is directed upward and radial to the spray arm.
Flow rates of the outer nozzles deliver 3.65 l/min, while the central nozzles provide 2.92 l/min. Together, the total flow rate reaches 30.6 l/min.
Inlets - Upper Spray Arm
The upper spray arm also features 10 inlets, but their configuration differs slightly due to the design of the support arm. Also theay are more tilted: The two outer nozzles are tilted at 45° in the rotational direction, while the central nozzles alternate their tilt at ±35°, ensuring optimized water distribution and dynamic coverage.
The impulse nozzles have a flow rate of 2.38 l/min, while the central nozzles have a flow rate of 1.9 l/min. Combined, these inlets achieve a total flow rate of approximately 20 l/min, providing efficient and effective water coverage.
Inlet - Ceiling Spray
The Ceiling spray differs from the spray arms in its design. Instead of multiple nozzles, it features a single large inlet with a radius of 0.01 m. Water distribution is achieved through a rotating physical geometry, which operates at 135 RPM. The flow rate of the ceiling spray is set at 7 l/min, providing a focused and efficient spray pattern. (See image below for a visual representation.)
Outlet
An outlet is positioned below the lower spray arm to remove fluid particles that are no longer part of the dishwashing process. Its primary purpose is to limit the overall number of fluid particles in the simulation, ensuring a more efficient and manageable computational process.
Results
Coverage Rate as an Efficiency Metric
To quantify the dishwasher’s efficiency, the coverage rate of the dishes was assessed at specific time steps (10 seconds and 15 seconds) during the simulation. The images below show the time-averaged coverage rate over a 5-second period for both the upper and lower dishes. This metric provides valuable insight into the effectiveness of water distribution and the thoroughness of cleaning. In other words, a 50% averaged coverage rate means that, on average, 50% of the time the dishes are in contact with water.
Results after 10 seconds
In the first 10 seconds, only the lower spray arm is active. This is reflected in the coverage, with the lower compartment being much better wetted than the upper one. This clearly indicates that relying solely on a lower spray arm, as suggested in the original geometry, would not be sufficient for optimal cleaning. However, even within the lower compartment, several areas remain either not wetted or inadequately covered. This suggests suboptimal liquid distribution. Potential reasons for this could include the lower spray arm being too small, the lower rack being positioned too close to the spray arm, or the nozzles being insufficient in number or not optimally positioned.
Results after 15 seconds
The results after 15 seconds are shown below. During this time, only the upper nozzles are active. As expected, the distribution improves in the upper compartment, but overall, the changes are minimal. The upper compartment is now better wetted, but similar issues persist, as seen earlier. There are still areas with insufficient liquid coverage, indicating that the water distribution is not optimal.
Water in The dishwasher
In the lower diagram, the total volume of water over time is shown. As seen, no more than 0.5 L is ever involved in the simulation at once. This means that even though there is a constant flow rate of about 30 l/min, the water drains quickly enough. In a real dishwasher, the water that flows back would then be reused and redistributed through the nozzles for cleaning.
Summary
This simulation demonstrated that shonDy is capable of realistically modeling a dishwasher, accurately simulating its alternating spray system and providing essential parameters for optimization. The total physical runtime of the simulation was 17 seconds, with the lower spray arm operating from 0 to 10 seconds and the upper spray arms and ceiling spray from 10 to 17 seconds. The rotation speeds were set at 45 RPM for the spray arms and 135 RPM for the ceiling spray, replicating real-world operating conditions. The particle radius of the fluid was 0.0004 m.
Throughout the simulation, key factors such as spray arm configurations, nozzle flow rates, and coverage rates were analyzed. It was shown that while the lower spray arm performed well for the lower compartment, relying solely on it would not be sufficient for optimal cleaning, highlighting the importance of the alternating spray system. The simulation also provided insights into water distribution, with a focus on coverage rates, which are crucial for assessing cleaning efficiency.
The goal of this simulation was not to optimize the dishwasher itself, but to showcase the capabilities of shonDy. The presented simulation serves as a starting point for an optimization task, demonstrating shonDy’s potential for enhancing appliance performance through detailed fluid dynamics modeling and fast, precise analysis.
