![]() ![]() Rapid image acquisition (11 s breath-hold) and image processing was feasible in all volunteers. Ascending aortic data were also compared with results from 15 patients with coronary heart disease (61 ± 13 years) to assess the clinical usefulness of the method. Ascending and descending aortic data from 15 healthy volunteers (30 ± 6 years) data were used to test the method for feasibility, and intra- and inter-observer variability. Image processing was integrated in a plug-in for the DICOM viewer OsiriX, including calculations of wave speed and wave intensity. These data were directly derived from PC-CMR using a breath-hold spiral sequence accelerated with sensitivity encoding (SENSE). Wave intensity was derived in terms of area and velocity changes. In this study, very high temporal resolution PC-CMR data is processed using an integrated and semi-automatic technique to derive wave intensity. Flow-velocity and area can both be derived from high-resolution phase-contrast cardiovascular magnetic resonance (PC-CMR). In order to further support the findings, an estimate of the uncertainty of the numerical results is derived through several repetitions of the numerical simulation with small perturbations of the initial conditions.Wave intensity analysis, traditionally derived from pressure and velocity data, can be formulated using velocity and area. It is shown that up to half-wave period after the breaking onset, the Reynolds number of the simulation does not significantly affect the solution. The limits of the main assumptions of the numerical calculations are analysed. It is seen that in the plunging regime the primary circulation induced by the breaking process scales with the velocity jump between the crest and the trough of the wave. A careful analysis of the circulation induced in water by the breaking process is carried out. A scaling dependence of the amount of air entrapped by the first plunging event on the initial steepness is found. Quantitative estimates of the amount of air entrapped by the breaking and of the degassing process are provided. Beyond a certain breaking intensity, the larger amount of air entrapped causes a reduction in the momentum transferred and the shrinkage of the layer. From weak to moderate breaking, increase in the breaking intensity results in growing transfer of horizontal momentum, as well as thickening of the surface layer. The downward transfer of the horizontal momentum is evaluated by integrating the flux of momentum through horizontal planes lying at different depths beneath the still water level. From the analysis of the local strain fields it is shown that, in the most energetic phase of plunging breaking, dissipation is mainly localized about the small air bubbles generated by the fragmentation of the air cavity entrapped by the plunging of the jet. Depending on the initial steepness ϵ, the wavetrain remains regular or develops a breaking, which can be either of spilling or plunging type. The evolution of periodic wavetrains is considered. The study, which assumes a two-dimensional flow, makes use of a two-fluids Navier–Stokes solver combined with a Level-Set technique for the interface capturing. The aim is to investigate the role played by the breaking intensity on the resulting flow. The flow generated by the breaking of free-surface waves of different initial steepnesses is simulated numerically. ![]()
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