The use of default coefficient values in Reynolds-averaged Navier–Stokes turbulence models often yields incorrect results because these coefficients are based on a limited flow types. To solve this problem, a method of calibration and selection of turbulence model input coefficients is proposed using the case of incompressible round jet flow in the range of Reynolds numbers from 5100 to 86 000. For the first time for round jets, the turbulence model is calibrated based on centerline velocity using all input constants. The influence of the coefficients on the axial jet velocity is analyzed. The optimal k−ε turbulence model coefficients are determined for a set of different Reynolds numbers so that the computational result matches the experimental data. Based on these data, the dependencies of the turbulence model coefficients on the Reynolds number are constructed. As a result, an improved k−ε turbulence model based on the open-source software OpenFOAM is implemented using these relations. The main advantage of the proposed model is its dependence on a single input parameter—the Reynolds number, which is based on the nozzle exit diameter. Other coefficients are determined as a function of the Reynolds number. A validation of the improved model on jet flows at other Reynolds numbers, which are not involved in the calibration process, is performed. It is found that the proposed model significantly refines the solution for incompressible jets both in the near and far field, which allows its use in other applied applications.

The influence of the viscosity on a wave attractor flow has been previously studied, particularly in relation to the widening of the hydrodynamical structures. In this work, we simulate an attractor flow with a peculiar bottom shape that includes an underwater hill. During the simulation, we discovered a side structure appearing beyond the wave attractor. We determined that the appearance of this structure is connected to viscosity. In this article, we consider the behavior of this newly found structure. Additionally, we discuss the challenges of energy accumulation and the estimation of the Reynolds number, which is a non-trivial problem in the context of wave attractor flows.

Рассматривается стохастическая модель галактического динамо, в рамках которой коэффициент турбулентной диффузии считается случайным процессом с обновлением. Проведено численное моделирование статистических моментов, а также двухточечных и трехточечных корреляторов магнитного поля, показывающих взаимосвязь между его значениями в различные моменты времени. Продемонстрировано наличие перемежаемости, выражающейся в прогрессивном росте моментов и корреляторов в случае "спокойных" областей галактик с небольшой долей ионизованной компоненты водорода. Проведено сопоставление результатов численного эксперимента с результатами, полученными ранее аналитически. In this paper we consider a stochastic model of the galactic dynamo in which the coefficient of turbulent diffusion is considered as a random process with renewal. The numerical simulation of statistical moments as well as two-point and three-point correlators of the magnetic field showing the relation between its values at various time instants is performed. The presence of intermittency expressed in the progressive growth of moments and correlators in the case of "quiet" regions of galaxies with a small fraction of the ionized hydrogen component is shown. The numerical results are compared with the results obtained analytically earlier.