Study on the Aspiration Properties of Glassrun Seal System under Time-Varying Pressure Difference

When a vehicle is driven at high speed, there exists intricate flow pattern and vortex shedding at the side window area with intense pressure fluctuation. A significant dynamic pressure difference between the vehicle's exterior and interior can render the side window sealing system vulnerable to aspiration. This susceptibility can lead to the generation of leakage noise, adversely affecting acoustic comfort in the vehicle's cabin. This paper delves into the aspiration properties of glassrun seal system under time-varying pressure difference. A nonlinear finite element model of the glassrun seal was established to simulate the quasi-static deformation of the sealing strip during installation process, which aims to obtain the deformed geometric shape and residual stress after this process. Then, the exterior flow field of the glassrun sealing area of a simplified vehicle model was calculated with CFD simulation to obtain the hydrodynamic pressure excitation acting on the outer surface of the sealing strip at different wind speeds, and the results were subsequently validated through wind tunnel test. With Arbitrary Lagrangian-Eulerian (ALE) numerical method, fluid-structure interaction (FSI) was simulated, the morphing mesh and overset mesh techniques were used to achieve FSI boundary motion and effective closure of the wall boundary gap, respectively. In this way, a nonlinear dynamic model of the coupled sealing structure and flow field was comprehensively established. Considering factors such as contact friction model, the forced vibration response and sealing aspiration condition of the sealing strip under actual excitation of time-varying pressure difference were analyzed. The results demonstrate that the contact state between the seal and the side window becomes unstable, when the hydrodynamic pressure fluctuation intensity on the outer surface of the glassrun seal is 34%, and the average pressure difference reaches approximately 1700 Pa. This instability manifests as a significant and persistent fluctuation on the contact area, ultimately leading to aspiration. These findings are of significant importance for optimization of the side window sealing system and precaution of aspiration noise.