Active Flow Control for Reducing Drag on Trucks: from Concept to Full Scale Testing

Doctoral thesis, 2017

There is no doubt that road vehicle transportation is needed to improve efficiency, to reduce power consumption and to contribute to a sustainable mobility. Aerodynamics plays a crucial role in this, and its optimization can have a significant impact on fuel efficiency. The work reported in this thesis thus investigates the applicability of an active flow control technique able to improve the aerodynamic performance of trucks. CFD simulations and wind tunnel experiments are conducted to explore the potential of such a device. The process starts with a preliminary LES study (Re = 1 × 10^5 ) and ends with a proof of concept full scale test of a real truck (Re = 3.5 × 10^6 ). The PANS method and scaled model wind tunnel experiments were essential to bridge the initial preliminary findings to the final full scale test. PANS was first validated (using in-house experimental data and data from test cases) and then used to simulate the efficacy of AFC at higher Re (Re = 5 × 10^5 ), introducing realistic flow conditions (wind gusts). In addition, wind tunnel experiments of a scaled, simplified truck cabin were used to demonstrate the applicability of the control. The results focus on two main points. First, synthetic jets were shown to be an effective and low energy consumption technique to control a pressure induced separated flow and for reducing drag on trucks. Second, PANS was shown to be an interesting method for industrial applications. Its capability to resolve unsteady flow cases preserving the accuracy of the flow structures prediction is shown, even when meshes are relatively coarse.