Aerodynamic investigation of a vehicle in highly turbulent flow

Sammanfattning

This master’s thesis presents the design, simulation, and experimental validation ofan active turbulence generator aimed at reproducing realistic, highly turbulent flowconditions for vehicle aerodynamic testing in a scale wind tunnel. The main goalis to bridge the gap between idealized wind tunnel tests and the unsteady, turbulentflow scenarios encountered during real-world highway and urban driving. Toachieve this, an active turbulence generator using oscillating airfoils was developed.The airfoils, based on the NACA 0015 profile, were actuated to produce adjustableturbulence intensities and length scales, matching conditions such as turbulence intensitiesof 1–5% for highway speeds in real-world driving scenarios. ComputationalFluid Dynamics (CFD) simulations were conducted using the κ−ω SST turbulencemodel with an overset mesh technique to accurately resolve the unsteady interactionbetween the moving airfoils and the freestream. The simulations analyzed characteristicparameters including turbulence intensity, turbulent length scale distributions,and aerodynamic loads on a DrivAer reference model. The design was optimizedto ensure turbulence generation across the test section while keeping the requiredmechanical power within feasible limits. A mechanical system driven via a singlemotor through a chain was designed and manufactured using rapid prototyping techniques,allowing synchronized oscillatory motion of all seven airfoils. The systemwas integrated into the Chalmers scale wind tunnel and tested. The findings serveas a solid foundation to be built upon in future projects regarding the developmentof an active turbulence generator.