High-speed turbulent separated flows - Consistency of mathematical models and flow physics

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 725-732 ◽  
Author(s):  
David S. Dolling
Keyword(s):  
Mathematical Models ◽  
High Speed ◽  
Separated Flows ◽  
Flow Physics

Steady longitudinal vortices in supersonic turbulent separated flows

2011 ◽  
Vol 672 ◽  
pp. 451-476 ◽  
Author(s):  
ERICH SCHÜLEIN ◽  
VICTOR M. TROFIMOV
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Roughness Element ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Leading Edge ◽  
Separated Flows ◽  
Vortex Generators ◽  
Longitudinal Vortices ◽  
Oil Flow

Large-scale longitudinal vortices in high-speed turbulent separated flows caused by relatively small irregularities at the model leading edges or at the model surfaces are investigated in this paper. Oil-flow visualization and infrared thermography techniques were applied in the wind tunnel tests at Mach numbers 3 and 5 to investigate the nominally 2-D ramp flow at deflection angles of 20°, 25° and 30°. The surface contour anomalies have been artificially simulated by very thin strips (vortex generators) of different shapes and thicknesses attached to the model surface. It is shown that the introduced streamwise vortical disturbances survive over very large downstream distances of the order of 104 vortex-generator heights in turbulent supersonic flows without pressure gradients. It is demonstrated that each vortex pair induced in the reattachment region of the ramp is definitely a child of a vortex pair, which was generated originally, for instance, by the small roughness element near the leading edge. The dependence of the spacing and intensity of the observed longitudinal vortices on the introduced disturbances (thickness and spanwise size of vortex generators) and on the flow parameters (Reynolds numbers, boundary-layer thickness, compression corner angles, etc.) has been shown experimentally.

scholarly journals World Experience in Creating Mathematical Models of Air Springs: Advantages and Disadvantages

2021 ◽  
pp. 25-42
Author(s):  
A. Y Kuzyshyn ◽  
S. A Kostritsia ◽  
Yu. H Sobolevska ◽  
А. V Batih
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Mathematical Models ◽  
Dynamic Behavior ◽  
High Speed ◽  
Vertical Direction ◽  
Rolling Stock ◽  
Air Spring ◽  
Advantages And Disadvantages ◽  
Mechanical Models

Purpose. Taking into account the production and commissioning of modern high-speed rolling stock, the authors are aimed to analyze the currently created mathematical models describing the dynamic behavior of the air spring, systematize them and consider the advantages and disadvantages of each model type. Methodology. For the analysis, a comparative chronological method was used, which makes it possible to trace the development of several points of view, concepts, theories. In accordance with the adopted decision equations, the existing models of air springs were divided into three groups: mechanical, thermodynamic and finite-elements. When analyzing mathematical models, the influence of a number of parameters on the dynamic behavior of the air spring, such as disturbing force frequency, heat transfer, nonlinear characteristics of materials, the shape of the membrane, etc., was considered. Findings. A feature of mechanical models is the determination of input parameters based on the analysis of experimental results, requires access to complex measuring equipment and must be performed for each new model of an air spring separately. Unlike mechanical models, which allow taking into account the damping effect of an air spring in the horizontal and vertical direction, thermodynamic models are mainly focused on studying the dynamic behavior of an air spring in the vertical direction. The use of the finite element method makes it possible to most accurately reproduce the dynamic behavior of an air spring, however, it requires significant expenditures of time and effort to create a finite element model and perform calculations. Originality. Mathematical models of the dynamic behavior of an air spring are systematized, and the importance of their study in conjunction with a spatial mathematical model of high-speed rolling stock is emphasized. Practical value. The analysis of the mathematical models of the dynamic behavior of the air spring shows the ways of their further improvement, indicates the possibility of their use in the spatial mathematical model of the rolling stock in accordance with the tasks set. It will allow, even at the design stage of high-speed rolling stock, to evaluate its dynamic characteristic and traffic safety indicators when interacting with a railway track.

scholarly journals New Dzungaria Gates for wmlt-corridor: historical necessity

2019 ◽  
Vol 5 (3) ◽  
pp. 36-44
Author(s):  
Viktor A. Bogachev ◽  
Yuri A. Terentyev ◽  
Viktor V. Koledov ◽  
Taras V. Bogachev
Keyword(s):  
Mathematical Models ◽  
Variational Methods ◽  
High Speed ◽  
Optimization Problem ◽  
Point Of View ◽  
The North ◽  
Computer Math ◽  
Pass Through ◽  
Historical Necessity ◽  
North Western

Background: Research is ongoing relating to the analysis of a set of issues that arise in connection with the creation of the operating on the basis of vacuum magnetic technologies a transcontinental high-speed land transport corridor, connecting the eastern regions of China with Russia. As part of the variation calculus task, the geopolitical, economic, social, logistic, geographic, geomorphological, seismological, topographic components of the project are considered, in which it is assumed that the high speed overland route will pass through the north-western part of the historical region of Dzungaria. Aim: Find the most optimal from the point of view of the above components the location of the most important section of high speed overland route passing through Central Asia. Methods: Variational methods for solving an optimization problem with the use of a computer math system. Results: After creating a fairly informative and versatile picture of the region in question, the foundations of the corresponding mathematical models are built. Conclusion: The New Dzungarian Gates is a key element in choosing the location of a high-speed overland route based on VMLT.

Mathematical Models of Asymmetric Modes in High-Speed Traffic

2021 ◽  
pp. 1051-1058
Author(s):  
Kamolbek Turdibekov ◽  
Mirjalil Yakubov ◽  
Absaid Sulliev ◽  
Amangul Sanbetova
Keyword(s):  
Mathematical Models ◽  
High Speed

APPLICATION OF THE JUMPING FROGS METHOD FOR THE OPTIMIZATION OF THREE-LEVEL PLANS OF A MULTIPLE FACTOR EXPERIMENT

2019 ◽  
pp. 35-42
Author(s):  
N. Koshevoy ◽  
E. Kostenko ◽  
V. Muratov
Keyword(s):  
Mathematical Model ◽  
Mathematical Models ◽  
High Speed ◽  
Minimum Cost ◽  
Optimization Method ◽  
Experimental Designs ◽  
Minimal Cost ◽  
Taboo Search ◽  
Time Costs ◽  
The Cost

he planning of the experiment allows us to solve the problem of obtaining a mathematical model with minimal cost and time costs. The cost of implementing an experiment is significantly affected by the order of alternating levels of change in factors. Thus, it is required to find a procedure for the implementation of experiments that provides the minimum cost (time) for conducting a multivariate experiment. This task becomes especially relevant when studying long and expensive processes. The purpose of this article is the further development of the methodology of optimal planning of the experiment in terms of cost (time), which includes a set of methods for optimizing the plans of the experiment and hardware and software for their implementation. Object of study: optimization processes for the cost of three-level plans for multivariate experiments. Subject of research: optimization method for cost and time costs of experimental designs based on the use of the jumping frog method. Experimental research methods are widely used to optimize production processes. One of the main goals of the experiment is to obtain the maximum amount of information about the influence of the studied factors on the production process. Next, a mathematical model of the object under study is built. Moreover, it is necessary to obtain these models at the minimum cost and time costs. The design of the experiment allows you to get mathematical models with minimal cost and time costs. For this, a method and software were developed for optimizing three-level plans using the jumping frog method. Three-level plans are used in the construction of mathematical models of the studied objects and systems. An analysis is made of the known methods for the synthesis of three-level plans that are optimal in cost and time costs. The operability of the algorithm was tested when studying the roughness of the silicon surface during deep plasma-chemical etching of MEMS elements. Its effectiveness is shown in comparison with the following methods: swarm of particles, taboo search, branches and borders. Using the developed method and software for optimizing three-level plans using the jumping frog method, one can achieve high winnings compared to the initial experimental plan, optimal or close to optimal results compared to particle swarm, taboo search, branches and borders methods, and also high speed of solving the optimization problem in comparison with previously developed optimization methods for three-level experimental designs.

Passive Control of High-Speed Separated Flows Using Splitter Plates

AIAA Journal ◽  
2012 ◽  
Vol 50 (7) ◽  
pp. 1586-1595 ◽  
Author(s):  
Todd M. Reedy ◽  
Gregory S. Elliott ◽  
J. Craig Dutton ◽  
Yeol Lee
Keyword(s):  
High Speed ◽  
Passive Control ◽  
Separated Flows ◽  
Splitter Plates

Unsteady Mechanisms of Compressor Corner Separation Over a Range of Incidences Based on Hybrid LES/RANS

2013 ◽  
Author(s):  
Zhong-Nan Wang ◽  
Xin Yuan
Keyword(s):  
Separated Flow ◽  
Suction Side ◽  
Separated Flows ◽  
Resonance Structure ◽  
Separation Flow ◽  
Trailing Edge ◽  
Flow Physics ◽  
Unsteady Separation ◽  
Large Pressure ◽  
Corner Flows

The separation flow pattern in compressor corners is well known but its nature is not fully understood. In this paper, the numerical simulation based on hybrid LES/RANS was performed to improve our understanding about the unsteady separation structure and its dynamic mechanisms of compressor corner flows, subject to a range of incoming flow incidences. In the simulation, the attached boundary layer near the walls was modeled by RANS, while the large separated flows in the corner were resolved by LES. The simulation was carefully validated by the experimental data before flow physics investigation. The unsteady separation structures and its effects were then investigated step by step, from phenomena observation to mechanisms analysis. First, the overall separation behavior and its associated flow physics was visualized and analyzed. It was found that the unsteady separation structure was distinct from the steady view. Some additional vortex structures, normally smeared out in the steady averaging process, were crucial in the unsteady dynamic process. These small but critical vortices corresponded to large intermittency in the separation size and strength. As the incidences increased, the vortex structure became much more complex due to the enhanced interaction of these vortices. Second, the turbulence behavior was examined in the separated regions. Anisotropy and non-equilibrium of turbulence were found to be dominant in the separation region due to non-homogenous shear of the separated flow. It posed a big challenge for conventional RANS prediction. Finally, the unsteadiness of corner separated flows was fully analyzed over a range of incidences. It was found that the unsteadiness came from two sources: the suction side separation and the wake shedding. The unsteadiness increased with the incidences. The two unsteady sources interacted with each other at high incidences, which led to a big unsteady resonance structure near the blade trailing edge. The resonance was responsible for a large pressure variation, implying the enhanced noise generation near the blade trailing edge.

Sign in / Sign up

Export Citation Format

Share Document