Passive Drag Reduction Optimization for Complex Commercial Vehicle Models

The long-distance transportation of heavy commercial vehicles is facing increasing pressure. Low wind resistance and low fuel consumption will become the objective requirements and development trend of heavy commercial vehicles. In this paper, the 1:1 complex model of commercial vehicle is taken as the research object to study the passive drag reduction of the commercial vehicle. First, simulation analysis is conducted, and then the wind tunnel test of the 1:2.5 complex model is performed to verify the accuracy of the simulation scheme and results. Then, the geometric shape of the cab is parameterized and controlled by 13 parameters. After determining the range of parameter changes, Latin hypercube sampling is selected, and large eddy simulation is used for numerical simulation to construct the sample space. Taking the shape parameter as the input factor and the coefficient of drag CD as the target response, the initial surrogate model is constructed, and the sample points are supplemented by the combination of global and local point addition strategies to improve the accuracy of the surrogate model. Finally, R2=0.812. The local details of the optimization results are optimized, and the low-wind-resistance shapes of the cabs of the three styling styles are obtained. Among them, the bullet model has the lowest CD. Compared with the basic model, the drag reduction rate is 28%, and the coefficient of drag is simulated. The error between the value and the test value is within 1%.