#### Recent fundamental studies

**Hydrodynamic instabilities and the transition to turbulence:** onset of 3D in fluid flows.

Mechanisms for the onset of large-scale 3D vortex structures in the wake (mode A instability) [Aleksyuk, Heil, JFM, 2023].
Mechanisms for the onset of small-scale 3D vortex structures in the wake (mode B instability) [Aleksyuk, Heil, JFM, in preparation].
Basic mechanisms for the growth/decay of 3D perturbations in fluid particles [Aleksyuk, Shkadov, EJMB/F, 2018; JFS, 2019].
**Compressible flows of viscous gas:** energy separation in wakes.

An explanation of the Eckert-Weise effect [Aleksyuk, JFM, 2021].
Intensification of the energy separation in the wakes [Aleksyuk, Osiptsov, IJHMT, 2018; Aleksyuk, IJHMT, 2019].
**Flow control:** generation of vortex wakes of a certain configuration.

Active/passive control of vortex wake configuration using reinforcement learning [in preparation].
**Shallow water flows:** Riemann problem with a discontinuous bottom.
Exact solver for the Riemann problem [Aleksyuk, Malakhov, Belikov, JCP, 2022].
The uniqueness of the Riemann problem [Aleksyuk, Belikov, JCP, 2019].
#### Recent applied studies

I develop mathematical models and numerical methods for modelling river flows with non-uniform sediment transport. The results of this research are implemented in the software STREAM 2D (Aleksyuk, Belikov) and used by various groups to solve environmental problems, as well as in education.

#### CFD software

I use self-developed (Python, C++, MPI, OpenMP, CUDA) software to simulate compressible/incompressible viscous fluid flows, two-phase immiscible flows, flows in shallow water approximation, and to analyse the results using theory of hydrodynamic stability. Algorithms are based on finite element and finite volume methods. Calculations are carried out using supercomputers and/or graphics processing units.

#### Fundings

In the last 5 years, the work has been supported by 6 scientific grants and 3 contracts (connected to applied river flow simulations).