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A numerical study of two dimensional lid-driven triangular and trapezoidal cavity flow is performed via using the lattice Boltzmann method (LBM) for steady solutions. The equilateral and right-angled isosceles triangular cavity flow at Reynolds numbers, respectively, 500 and 100 is employed as the benchmark case for code validation. The isosceles right-angled triangular cavity flow is studied for Reynolds numbers sweeping from 100 to 8100. Flow topologies are captured and analyzed. The critical Reynolds number of Hopf bifurcation is predicted by calculating the perturbation decay rate. Two different geometries of right-angled isosceles trapezoidal cavities, bowl-shaped and pyramid-shaped trapezoids, are studied at Reynolds numbers 1000 and 7000. For each type of the trapezoidal cavity, a geometric parameter l (top-line/base-line ratio) is presented to distinguish different geometries of trapezoidal cavities. The flow patterns regarding the streamlines, vortical structures, and velocity profiles are discussed. The impact of parameter l on the fluid characteristics are investigated This work was sponsored by the foundation of National Key Laboratory of Science and Technology on Aerodynamic Design and Research (No. 614220121030101) and Key Laboratory of Icing and Anti/De-icing of CARDC (Grant No. IADL20210302)

The number of applications where fluidic oscillators are expected to be used in the future, is raising sharply, then their ability of interacting with the boundary layer to modify forces on bluff bodies, enhancing heat transfer or decreasing noise generation, are just few of the applications where fluidic oscillators can be used. For each application a particular pulsating frequency and amplitude are required to minimize/maximize the variable under study, force, Nusselt number, etc. For a given range of Reynolds numbers, fluidic oscillators present a linear relationship between the output frequency and the incoming fluid flow, yet it appears the modification of the internal fluidic oscillator geometry may affect this relation. In the present paper and for a given fluidic oscillator, several performance parameters will be numerically evaluated as a function of different internal modifications via using 3D-CFD simulations. The paper is also evaluating the relation between the momentum applied to the mixing chamber incoming jet and the oscillator output characteristics. The evaluation is based on studying the output mass flow frequency and amplitude whenever several internal geometry parameters are modified. The geometry modifications considered were: the mixing chamber inlet and outlet widths, and the mixing chamber inlet and outlet wall inclination angles. The concept behind this paper is, to evaluate how much the fluidic oscillator internal dimensions affect the device main characteristics, and to analyze which parts of the oscillator produce a higher impact on the fluidic oscillator output characteristics. For the different internal modifications evaluated, special care is taken in studying the forces required to flip the jet. The entire study is performed for three different Reynolds numbers, 8711, 16034 and 32068. Among the conclusions reached it is to be highlighted that, for a given Reynolds number, modifying the internal shape affects the oscillation frequencies and amplitudes. Any oscillator internal modification generates a much relevant effect as Reynolds number increases. Under all conditions studied, it was observed the fluidic oscillator is pressure driven.

The suspensions used in heavy vehicles often consist of several oil and two gas chambers. In order to perform an analytical study of the mass flow transferred between two gas chambers separated by a nozzle, and when considering the gas as compressible and real, it is usually needed to determine the discharge coefficient of the nozzle. The nozzle configuration analyzed in the present study consists of a T shape, and it is used to separate two nitrogen chambers employed in heavy vehicle suspensions. In the present study, under compressible dynamic real flow conditions and at operating pressures, discharge coefficients were determined based on experimental data. A test rig was constructed for this purpose, and air was used as working fluid. The study clarifies that discharge coefficients for the T shape nozzle studied not only depend on the pressure gradient between chambers but also on the flow direction. Computational Fluid Dynamic (CFD) simulations, using air as working fluid and when flowing in both nozzle directions, were undertaken, as well, and the fluid was considered as compressible and ideal. The CFD results deeply helped in understanding why the dynamic discharge coefficients were dependent on both the pressure ratio and flow direction, clarifying at which nozzle location, and for how long, chocked flow was to be expected. Experimentally-based results were compared with the CFD ones, validating both the experimental procedure and numerical methodologies presented. The information gathered in the present study is aimed to be used to mathematically characterize the dynamic performance of a real suspension IM-2020-1-0001 Optimization of five Active Flow Control parameters on a SD7003 wing profile at several angles of attack from 4 to 16 and at Reynolds number 60000 (second period)