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The author has presented results of numerical modeling of the influence of the angle of attack of a thin width-limited plate with a short chord on the velocity field of the internal region of a turbulent boundary layer (TBL) and skin friction. The computations were performed by the large eddy simulation (LES) method at the Reynolds number Reθ = 540 calculated from the velocity on the channel axis and the momentum thickness. Changes in the average and pulsation characteristics of the three-dimensional velocity field under the impact of the wake of the plate and of tip vortices as functions of the angle of attack of the plate in the range ±1° have been analyzed. It has been shown that a determining influence on the formation of the velocity field is exerted by the tip vortices whose vorticity is opposite with the positive and negative angles of attack. The mean value of the skin-friction coefficient decreases by 6% at the positive angle of attack and by 14% at the negative angle with respect to the value of this coefficient in an unperturbed TBL. [ABSTRACT FROM AUTHOR]

The present experimental work is focused on designing and standardizing a direct method of measuring the drag force on a tapered cylinder in a water tunnel. The model considered in the present study is a tapered cylinder of 70:1 taper ratio (with a mean diameter( D m ) of 8 mm) placed in a water tunnel test section. The drag force is measured directly, which is acquired by using a force transducer setup (strain-gauge-based), augmented with a lever arm to amplify or attenuate the force. Multiple calibrations of the load cells were done to ensure the repeatability of experiments. The taper cylinder model is suspended inside the water tunnel and the drag force is obtained for various Reynolds numbers (based on mean diameter). It was found that the drag coefficient was ≈ 10-20 % less than a circular cylinder. [ABSTRACT FROM AUTHOR]

In this paper, we present an overview of numerical simulation methods for the flow around typical underwater vehicles at high Reynolds numbers, which highlights the dominant flow structures in different regions of interest. This overview covers the forebody, midbody, stern, wake region, and appendages and summarizes flow phenomena, including laminar-to-turbulent transition, turbulent boundary layers, flow under the influence of curvatures, wake interactions, and all associated complex vortex structures. Furthermore, the current issues and challenges of capturing these flow structures are addressed. This overview provides a deep insight into the use of numerical simulation methods, including the Reynolds-averaged Navier–Stokes (RANS) method, large eddy simulation (LES) method, and the hybrid RANS/LES method, and evaluates their applicability in capturing detailed flow features. [ABSTRACT FROM AUTHOR]

The use of wind energy, the area of wind farms, and the length of wind turbine blades continuously increase with the increase in energy demand. This study aims to simulate large wind farms in the atmospheric boundary layer with different double-rotor (DR) wind turbine arrangements using large eddy simulation. The effect of four DR wind turbine arrangements on the efficiency of a large wind farm was investigated in this study. All simulations were performed using the OpenFOAM solver. The performance of different turbine arrangements was investigated based on the mean velocity, the extent of the wake region, mean kinetic energy, and turbine power. Results showed that the arrangement of DR turbines with transverse spacing produces higher power than other layouts. Moreover, DR layouts produce the same power as single-rotor layouts with a short blade length. This scenario is important from an economic point of view. [ABSTRACT FROM AUTHOR]

The study of the visual images of fluid flows is ongoing and has intensified in recent years by advancements in light sources and receivers. Both classical schlieren instruments of the IAB series and original developments acquired new qualities. The selection of the source and visualizing diaphragm shapes allow to register the fields of various components of the reflectivity and density gradient in stratified flows (examples are given). Anodic oxidation of tin–electrolytic precipitation–is used to visualize matter transfer from a compact source. The structure of the flow pattern around a horizontally moving sphere is visualized in a wide range of parameters. [ABSTRACT FROM AUTHOR]