Particle-based method for investigation of the physical processes in the complex industrial tasks

The main task of this paper is improved of modeling accuracy and understanding of the physical process which arises in complex industrial tasks using Euler-Lagrange approach. There were two cases under the study. The first one was aimed to study the dynamics of selforganized turbulent structures. A first qualitative insight into the entrainment process in wind farm is obtained through particle tracking. The second case is focusing on developing the EulerLagrange approach for the understanding of the physical processes occurring the water droplets injection into a jet. The water droplets, coming out of the special sockets, are simulated by packages (parcels) of particles of a certain mass and size according to the specified flow rate. Parcels moving in the flow, breakup at high speeds, heating and evaporation are investigated

ВЕРИФИКАЦИЯ ГИБРИДНОЙ ЧИСЛЕННОЙ СХЕМЫ ДЛЯ ЗАДАЧИ НАТЕКАНИЯ СЖИМАЕМОЙ СТРУИ НА ТВЕРДУЮ ПРЕГРАДУ

The article deals with the questions of mathematical modeling of compressible jet outflow from model nozzle and jet impingiment on flat plate at various values of n. pisoCentralFoam solver which is based on the Kurganov-Tadmor hybrid numerical scheme, PISO algorithm and finite volume method, is used for the solution of this problem. The model, based on unsteady Reynolds equation and K-omega SST turbulence model with boundary functions is used for compressible jet calculation. The problem definition for calculation of jet impingiment on flat plate is given. The simulation domainwas selected as a rectangle. Only a half of the nozzle was considered for simplification. The mixed boundary condition for pressure setting in case of free jet was used on the outlet of simulation domain. The special condition for the pressure with table data, allowed to increase the value of pressure gradually, was used on the inlet of simulation domain. The value of the jet pressure degree was selected as n = 2.5 and n = 5.0. The results of distribution of the velocity magnitude, field pressure, upon symmetry axes were received. The simulations were done with grids 100 000-500 000 cells. The average value of y+ was equal to 270. The calculations were done for the end time Tend = 0.01 s. Comparison of the results of pressure distribution calculation based on nozzle length on different grids with the results of the experiment is carried out. The coincidence to engineering accuracy of 5 % is received.В статье рассматриваются вопросы математического моделирования истечения свободной сжимаемой турбулентной струи из модельного сопла и натекания струи на твердую преграду при различных степенях нерасчетности. Для решения задачи используется разработанный авторами статьи решатель pisoCentralFoam на базе гибридной численной схемы Kurganov-Tadmor, алгоритма PISO и метода контрольного объема. Для расчета сжимаемой струи используется модель на базе нестационарных уравнений Рейнольдса и k-omega SST модели турбулентности с пристеночными функциями. Приведена постановка задачи для расчета натекания струи на преграду. Расчетная область представляла собой прямоугольник. Для упрощения постановки задачи рассматривалось только половина сопла. Для случая свободной струи на задания давления на выходе расчетной области использовалось смешанное граничное условие 3-го рода. На входе расчетной области задавалось специальное табличное условие для давления, которое позволяло постепенно поднимать абсолютное значений для давления. Значение степени нерасчетности струи выбиралось равным n = 2,5 и n = 5,0. Проведен анализ сеточной сходимости на сетках от 100 тысяч до 500 тысяч ячеек. Среднее значение величины y+ составило 270. Расчеты проводились для конечного времени Tend = 0,01 секунды. Получены результаты распределения поля модуля скорости, давления на оси симметрии. Проведено сравнение результатов расчета распределения давления по длине сопла на разных расчетных сетках с результатами эксперимента. Получено совпадение с результатами эксперимента с точностью в 5 %

Real-Gas Effects and Phase Separation in Underexpanded Jets at Engine-Relevant Conditions

A numerical framework implemented in the open-source tool OpenFOAM is presented in this work combining a hybrid, pressure-based solver with a vapor-liquid equilibrium model based on the cubic equation of state. This framework is used in the present work to investigate underexpanded jets at engine-relevant conditions where real-gas effects and mixture induced phase separation are probable to occur. A thorough validation and discussion of the applied vapor-liquid equilibrium model is conducted by means of general thermodynamic relations and measurement data available in the literature. Engine-relevant simulation cases for two different fuels were defined. Analyses of the flow field show that the used fuel has a first order effect on the occurrence of phase separation. In the case of phase separation two different effects could be revealed causing the single-phase instability, namely the strong expansion and the mixing of the fuel with the chamber gas. A comparison of single-phase and two-phase jets disclosed that the phase separation leads to a completely different penetration depth in contrast to single-phase injection and therefore commonly used analytical approaches fail to predict the penetration depth.Comment: Preprint submitted to AIAA Scitech 2018, Kissimmee, Florid

Application of open-source software for industrial problems of vehicle lift-off gas dynamics

High-power shock, heat, mechanical and especially acoustic loads present a serious problem as their impact on the rocket and the launch pad can be too strong. Turbulent supersonic jets ejected from the vehicle nozzles are the main source of these loads. One way to reduce the intensity of acoustic loads is to supply a special system of water jets that interact with the supersonic gas jets near the rocket nozzles. Numerical simulation of this interaction is an important part of the design of such noise reduction systems. The proposed numerical model should enable simulation of various processes of different scale, such as gas/droplets interaction, nozzle jets in the near field, acoustic loads in the far field, chemical reactions and others. Therefore, such a model should be modular and hierarchically aligned. A flexible and extensible implementation of the numerical model can be possible with open-source codes. This paper concerns the problem of numerical simulation of compressible turbulent supersonic jets. The hybrid gas dynamics solver which was used in this investigation is one of the main modules of the general numerical model. Preliminary results of verification of this module are presented. Comparison of numerical and experimental results for various experimental cases, both Russian and foreign, is given