Towards reliable estimation of instantaneous pressure and aerodynamic loads from velocity measurements

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The modern design of many engineering systems requires quantitative analysis of fluid flows. In most cases, particularly for external flows, the ultimate goal of the analysis is the estimation of structural loads and forces generated from fluid flow interaction with system boundaries. On the other hand, design optimisation of such systems often requires insight into the flow physics. The proposed research program will address both of these aspects by enabling simultaneous characterisation of unsteady flow field development and the attendant fluid forcing based solely on experimental velocity measurements.******The program will provide robust methodologies for estimating instantaneous pressure fields from experimental velocity measurements, providing complete information about flow development. This information will also be used to estimate instantaneous fluid forcing. While such methodologies are applicable to a variety of engineering flows, it is of particular importance in fluid-structure-interaction problems, in which direct force measurement is often not feasible. The specific test case to be examined in the proposed program is that of vortex-induced vibrations (VIV) produced by the periodic shedding of vortices from a circular cylinder. This phenomenon occurs in a variety of practical applications, e.g., oil risers, offshore installations, and various civil structures that frequently employ cylindrical geometries. If it is not accurately predicted and accounted for at the design stage, VIV can impede normal system operation, shorten system lifespan, or even cause catastrophic failures. However, the required representative dynamic models are currently lacking due to the lack of insight into fluid forcing and the attendant fluid-structure coupling. The proposed research will give significant, new insight into free VIV by providing time-resolved characterisation of flow development, fluid-structure interactions, and fluid forcing. The results will be used to evaluate the existing fluid forcing models and formulate improved dynamic models of VIVs.******The program will significantly advance the state of the art in the area of experimental measurements and VIV. It will expand the current diagnostic capabilities of major importance in fluid-structure-interaction (FSI) problems and aeroacoustics, where the access to pressure field information not only gives a more complete description of the flow physics, but is also essential for the characterisation of the unsteady fluid loading (FSI) and noise generation (aeroacoustics). The findings will also have significant impacts on the practical applications by providing improved dynamic models required for accurate system response prediction and effective mitigation of VIV. Finally, the program will contribute to the training of highly qualified personnel at both graduate and undergraduate levels.