Anti-PIV type 1 Monoclonal antibody, Clone CID03

An experimental investigation focused on the manipulation of the wake generated by a square back car model is presented. Four continuously-blowing rectangular slot jets were mounted on the rear face of a 1:10 commercial van model. Load cell measurements evidence drag reduction for different forcing configurations, reaching a maximum of 12% for lateral and bottom jets blowing. The spectral analysis of the pressure fluctuations evidence, for all forced cases, an energy attenuation with respect to the natural case, especially close to the shedding frequency. An energy budget highlighted the most efficient forcing configurations accounting for both the drag reduction and the power required to feed the blowing system. Two main configurations are considered: the maximum drag reduction and the best compromise, yielding 5% drag reduction and a convenient energy balance. Particle Image Velocimetry (pPIV) and stereoscopic PIV (sPIV) experiments were performed allowing the three-dimensional reconstruction of the wake in the three considered configurations. Consistently with static and fluctuating pressure measurements, sPIV results reveal a dramatic change in the wake structure when the jets blow in the maximum drag reduction configuration. Conversely, the best compromise configuration reveals a wake structure similar to the natural one.

Large-eddy simulation has been increasingly applied to internal combustion engine flows because of their improved potential to capture the spatial and temporal evolution of turbulent flow structures compared with Reynolds-averaged Navier Stokes simulation. Furthermore, large-eddy simulation is universally recognized as capable of simulating highly unsteady and random phenomena, which drive cycle-to-cycle variability and cycle-resolved events such as knocks and misfires. To identify large-scale structure fluctuations, many methods have been proposed in the literature. This article describes the application of several analysis methods for the comparison between different datasets (experimental or numerical) and the identification of large-structure fluctuations. The reference engine is the well-known TCC-III single-cylinder optical unit from the University of Michigan and GM Global R&D center; the analyses were carried out under motored engine conditions. A deep analysis of in-cylinder gas dynamics and flow structure evolution was performed by comparing the experimental results (particle image velocimetry of the velocity fields) with a dataset of consecutive large-eddy simulation cycles on four different cutting planes at engine-relevant crank angle positions. Phase-dependent proper orthogonal decomposition was used to obtain further conclusions regarding the accuracy of the simulation results and to apply conditional averaging methods. A two-point correlation and an analysis of the tumble center are proposed. Finally, conclusions are drawn to be used as guidelines in future large-eddy simulation analyses of internal combustion engines.