Three dimensional, stratified gas flows past an obstacle

1984 ◽  
Vol 55 (3) ◽  
pp. 347-368 ◽  
Author(s):  
Mark A Hausman ◽  
William W Roberts
Keyword(s):  
Three Dimensional ◽  
Gas Flows

scholarly journals Envelopes of embedded super-Earths – II. Three-dimensional isothermal simulations

2019 ◽  
Vol 488 (2) ◽  
pp. 2365-2379 ◽  
Author(s):  
William Béthune ◽  
Roman R Rafikov
Keyword(s):  
Three Dimensional ◽  
Polar Axis ◽  
High Mass ◽  
Gas Flows ◽  
Core Mass ◽  
Material Recycling ◽  
The Core ◽  
Planetary Cores ◽  
Mass Circulation ◽  
Runaway Growth

ABSTRACT Massive planetary cores embedded in protoplanetary discs are believed to accrete extended atmospheres, providing a pathway to forming gas giants and gas-rich super-Earths. The properties of these atmospheres strongly depend on the nature of the coupling between the atmosphere and the surrounding disc. We examine the formation of gaseous envelopes around massive planetary cores via three-dimensional inviscid and isothermal hydrodynamic simulations. We focus the changes in the envelope properties as the core mass varies from low (subthermal) to high (superthermal) values, a regime relevant to close-in super-Earths. We show that global envelope properties such as the amount of rotational support or turbulent mixing are mostly sensitive to the ratio of the Bondi radius of the core to its physical size. High-mass cores are fed by supersonic inflows arriving along the polar axis and shocking on the densest parts of the envelope, driving turbulence, and mass accretion. Gas flows out of the core’s Hill sphere in the equatorial plane, describing a global mass circulation through the envelope. The shell of shocked gas atop the core surface delimits regions of slow (inside) and fast (outside) material recycling by gas from the surrounding disc. While recycling hinders the runaway growth towards gas giants, the inner regions of protoplanetary atmospheres, more immune to mixing, may remain bound to the planet.

A Study of the Three-Dimensional Unsteady Real-Gas Flows Within a Transonic ORC Turbine

2014 ◽  
Author(s):  
Andrew P. S. Wheeler ◽  
Jonathan Ong
Keyword(s):  
Three Dimensional ◽  
Organic Rankine Cycle ◽  
Leading Edge ◽  
Rankine Cycle ◽  
Gas Flows ◽  
Cfd Simulations ◽  
Significant Drop ◽  
Real Gas ◽  
Turbine Efficiency ◽  
Real Gas Effects

In this paper we investigate the three-dimensional unsteady real-gas flows which occur within Organic Rankine Cycle (ORC) turbines. A radial-inflow turbine stage operating with supersonic vane exit flows (M ≈ 1.4) is simulated using a RANS solver which includes real-gas effects. Steady CFD simulations show that small changes in the inducer shape can have a significant effect on turbine efficiency due to the development of supersonic flows in the rotor. Unsteady predictions show the same trends as the steady CFD, however a strong interaction between the vane trailing-edge shocks and rotor leading-edge leads to a significant drop in efficiency.

scholarly journals Parallel implementation of multiscale approach to the numerical study of gas microflows

2016 ◽  
pp. 147-165
Author(s):  
В.О. Подрыга ◽  
С.В. Поляков
Keyword(s):  
Gas Flow ◽  
Parallel Implementation ◽  
Numerical Study ◽  
Domain Decomposition Method ◽  
Three Dimensional ◽  
Multiscale Approach ◽  
Gas Flows ◽  
Physical Processes ◽  
Gas Microflows ◽  
Complex Technical Systems

Статья посвящена параллельной реализации многомасштабного подхода для расчета течений газов в микроканалах сложных технических систем. Многомасштабный подход сочетает решения уравнений квазигазодинамики (КГД) и молекулярной динамики (МД). Представлена параллельная реализация подхода, основанная на методах расщепления по физическим процессам и разделения областей. Реализация ориентирована на использование вычислительных систем с центральной и гибридной архитектурами. Разработанные параллельные алгоритмы обладают хорошей масштабируемостью. Полученные результаты подтвердили эффективность разработанного подхода. С его помощью методами МД были получены основные коэффициентные зависимости для КГД-системы, произведен расчет трехмерного течения. This paper is devoted to a parallel implementation of multiscale approach to the numerical study of gas flows in microchannels of complex technical systems. The multiscale approach combines the solutions of quasigasdynamic (QGD) equations and molecular dynamics (MD) equations. The proposed parallel implementation of this approach is based on the method of splitting into physical processes and the domain decomposition method. The implementation is oriented for using computer systems with central and hybrid architectures. The developed parallel algorithms show a good scalability. The obtained results confirm the efficiency of the approach under consideration. This approach was used to find the basic coefficient dependences for the QGD system by MD methods and to study a three-dimensional gas flow numerically.

Numerical simulation of complex gas flows in concentrated fire vortices

2019 ◽  
Vol 5 (3) ◽  
pp. 47-68
Author(s):  
Sergei P. Bautin ◽  
Alexandr G. Obukhov
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Local Heating ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Initial Boundary ◽  
Gas Flows ◽  
Heat Conducting ◽  
Russian Academy Of Sciences ◽  
Academy Of Sciences

This article presents the results of numerical simulation of free fire vortices arising in laboratory conditions. The authors demonstrate the possibility of obtaining such concentrated fire vortices in a series of experimental studies conducted under the supervision of A. &nbsp;Yu. &nbsp;Varaksin, a corresponding member of the Russian Academy of Sciences, at the Joint Institute for High Temperatures of the Russian Academy of Sciences.<br> The authors propose to consider the analytical and numerical studies of arising complex swirling gas flows during local heating of a metal underlying surface by several sources from the point of view of gas dynamics. When considering complex flows of a heating gas as a motion of a viscous, heat-conducting, and compressible continuous medium, the complete system of Navier&nbsp;— Stokes equations is used. The proposed initial-boundary conditions made it possible to numerically determine the main gas-dynamic characteristics of the resulting three-dimensional and unsteady gas flows in free fire vortices.<br> The calculation results showed that during the formation of fiery vortices, several stages are distinguished in their development. The first stage is characterized by the occurrence of local gas flows diverging in the radial direction from the heating regions. The second stage is accompanied by the formation in the regions of the location of the heating sources of local vortices with opposite spin directions. The third stage is characterized by the fact that from smaller vortices due to the intense influx of external air a common large thermal vortex is formed, which receives a positive twist under the influence of the Coriolis force. At the fourth stage, with an increase in the rotation speed, a decrease in the vertical dimensions of the thermal vortex and its decay into several small ones is observed. Thus, the completion of the life cycle of one concentrated vortex is replaced by the formation of a new one. For the initial parameters, the lifetime of the concentrated thermal vortex is about one minute.

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