Ass Savers

CFD Simulation of the Protection Level offered by a Mudguard for Bikes

Assess and validate the protection level offered by the addition of a piece of plastic equipment (mudguard) on a bike. This component aims at reducing the dirtiness that a cyclist sustains when he passes through puddles or mud that spray up from the tires.

Description:
Ass Savers is a Swedish company that has designed a concept for a mudguard made of plastic sheets. It is specially designed to be attached to the underside of a bicycle seat. This component can minimize splashing on the buttocks and lower back. Its other advantages are its light weight, ease of installation, and affordability. Furthermore, it is recyclable!
Ass Savers and Lx Sim worked together, pooling their expertise to develop a CFD simulation procedure to evaluate and demonstrate the protection level from splashes that the mudguard offers.

Experiment:
– Combine many physical models of the dynamics of fluids in a single simulation.
– Obtain representative qualitative results

Lx Sim Expertise:
– Fluid dynamics simulations with the multi-physics software STAR-CCM+ from the company CD-adapco.

Benefits:
– Rapid identification of the level of splashing during a passage through water and quick comparison between concepts.
– Limit the number of prototypes and test cycles by first validating concepts. Simulation allows making adjustments to the initial design and correct problems before fabrication and testing of the first prototype.

Methodology:
With our expertise in CFD simulation, we were able to begin by designing a simulation to demonstrate and analyze the effectiveness of this product. First, we used a bike model and cyclist that were available in our libraries. Then we simulated the airflow using the STAR-CCM+ software. The simulation allowed us to add a model for water in the form of a thin film on the ground that was carried on different surfaces, such as wheels. Another model of Lagrangian droplets was then used to represent the water as it is influenced by the air forces in motion around the cyclist. A mass interaction model allowed us to convert the water film into droplets and return them to film upon surface impingement. These steps allowed us to combine all air and water dynamics into a single simulation.

Results:
Lx Sim used the methodology described above to simulate a cyclist moving through water with and without mudguards. Simulations have convincingly shown that the use of an Ass Savers’ mudguard protects a large part of the back of the cyclist.