A numerical simulation of a spatially evolving turbulent boundary layer impacted by a spanwise traveling transversal sinusoidal wall oscillation is performed. Compared to boundary layer flow over a non-oscillating surface, i.e a standard flat plate boundary layer, a reduction of friction drag of more than 6% is found. A detailed discussion of the near-wall flow reveals similar effects as observed by other excitation methods, such as additionally implemented volume forces or longitudinal sinusoidal wall oscillation. Secondary flow structures induced by the moving wall and a controlled formation of streamwise vorticity close to the wall are identified. The wall-normal vorticity fluctuations are found to be damped such that streak instability and formation of new streaks are reduced yielding an evidently decreased friction drag.

Multi-physics simulations are at the heart of today's engineering applications. The trend is towards more realistic and detailed simulations, which demand highly resolved spatial and temporal scales of various physical mechanisms to solve engineering problems in a reasonable amount of time. As a consequence, numerical codes need to run efficiently on high-performance computers. Therefore, the framework Zonal Flow Solver (ZFS) featuring lattice-Boltzmann, finite-volume, discontinuous Galerkin, level set and Lagrange solvers has been developed. The solvers can be combined to simulate, e.g. quasi-incompressible and compressible flow, aeroacoustics, moving boundaries and particle dynamics. In this manuscript, the multi-physics implementation of the coupling mechanisms are presented. The parallelisation approach, the involved solvers and their scalability on state-of-the-art heterogeneous high-performance computers are discussed. Various multi-physics applications complement the discussion. The results show ZFS to be a highly efficient and flexible multi-purpose tool that can be used to solve varying classes of coupled problems.

Direct particle–fluid simulations of heavy spheres and ellipsoids interacting with decaying isotropic turbulence are conducted. This is the rigorous extension of the spherical particle analysis in Schneiders et al. (J. Fluid Mech., vol. 819, 2017, pp. 188–227) to $O(10^{4})$ non-spherical particles. To the best of the authors’ knowledge, this represents the first particle-resolved study on turbulence modulation by non-spherical particles of near-Kolmogorov-scale size. The modulation of the turbulent flow is precisely captured by explicitly resolving the stresses acting on the fluid–particle interfaces. The decay rates of the fluid and particle kinetic energy are found to increase with the particle aspect ratio. This is due to the particle-induced dissipation rate and the direct transfer of kinetic energy, both of which can be substantially larger than for spherical particles depending on the particle orientation. The extra dissipation rate resulting from the translational and rotational particle motion is quantified to detail the impact of the particles on the fluid kinetic energy budget and the influence of the particle shape. It is demonstrated that the previously derived analytical model for the particle-induced dissipation rate of smaller particles is valid for the present cases albeit these involve significant finite-size effects. This generic expression allows us to assess the impact of individual inertial particles on the local energy balance independent of the particle shape and to quantify the share of the rotational particle motion in the kinetic energy budget. To enable the examination of this mechanistic model in particle-resolved simulations, a method is proposed to reconstruct the so-called undisturbed fluid velocity and fluid rotation rate close to a particle. The accuracy and robustness of the scheme are corroborated via a parameter study. The subsequent discussion emphasizes the necessity to account for the orientation-dependent drag and torque in Lagrangian point-particle models, including corrections for finite particle Reynolds numbers, to reproduce the local and global energy balance of the multiphase system.

Pulsed electrochemical machining offers great potential to meet growing demands on components like miniaturization, efficiency, and functionalization. Current research activities show that the electrochemical process can be influenced by a superimposed magnetic field. While the effects of most process parameters such as pulse regimes, flow conditions, and cathode material selection are well understood, the influence of magnetic fields is still difficult to estimate for a targeted process design. Obtaining a better understanding of the magnetic field–assisted electrochemical machining process and achieving a foundation for later process simulations are the objectives of the present work where we focus on the influence of the Lorentz force in a NaNO₃-electrolyte. Therefore, an experimental setup was designed in which the magnetic field is arranged perpendicular to the electric field. To reduce the influence of the electrochemical reaction on the electrolyte flow field, a large distance between the stainless-steel electrodes was chosen. The resulting flow in the initially resting fluid is mainly induced by the Lorentz force. This electrolyte flow is studied by particle image velocimetry and is modelled by magnetohydrodynamic and multiphase simulations. Based on the experimental results, the simulations are validated. In the future, the simulation approach will be pursued, e.g., for the electrochemical machining with pulsed electric current and oscillating cathode.