Study On the Applicability of URANS, LES and Hybrid LES/RANS Models for Prediction of Hydrodynamics of Cyclone Separator

2021 ◽  
Author(s):  
Sai Guruprasad Jakkala ◽  
S Vengadesan
Keyword(s):  
Fluid Flow ◽  
Flow Characteristics ◽  
Mesh Size ◽  
Turbulent Energy ◽  
Computational Time ◽  
Detached Eddy Simulation ◽  
Reynolds Stresses ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Rans Models

Abstract Cyclone separators are an integral part of many industrial processes. A good understanding of the flow features is paramount to efficiently use them. The turbulent fluid flow characteristics are modelled using URANS, LES and hybrid LES/RANS turbulent models. The hybrid LES/RANS approaches, namely DES (Detached Eddy Simulation), DDES (Delayed Detached Eddy Simulation) and IDDES (Improved Delayed Detached Eddy Simulation) based on the k - $\omega$ SST RANS approaches are explored. The study is carried out for three different inlet velocities (v = 8, 16:1, and 32 m=s). The results from hybrid LES/RANS models are shown to be in good agreement with the experimental data available in the literature. Reduction in computational time and mesh size are the two main benefits of using hybrid LES/RANS models over the traditional LES methods. The Reynolds stresses are observed in order to understand the redistribution of turbulent energy in the flow field. The velocity profiles and vorticity quantities are explored to obtain a better understanding of the behaviour of fluid flow in cyclone separators.

Numerical Implementation of Detached-Eddy Simulation on a Passenger Vehicle and Some Experimental Correlation

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
L. Sterken ◽  
S. Sebben ◽  
L. Löfdahl
Keyword(s):  
Flow Characteristics ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Wake Flow ◽  
Computational Time ◽  
Detached Eddy Simulation ◽  
Passenger Vehicle ◽  
Ansys Fluent ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

This study presents an implementation of delayed detached-eddy simulation (DDES) on a full-scale passenger vehicle for three configurations with the use of commercial software harpoon (mesher) and ansys fluent (solver). The methodology aims to simulate the flow accurately around complex geometries at relevantly high Re numbers for use in industrial applications, within an acceptable computational time. Geometric differences between the three configurations ensure significant drag changes that have a strong effect on the wake formation behind the vehicle. Therefore, this paper focuses on the analysis of the base wake region. At first, the paper evaluates the performance of the DDES, where it verifies the different operating conditions of the flow around the vehicle with respect to the DDES definition. In a second step, the numerical results are correlated with force measurements and time-averaged flow field investigations, conducted in the Volvo Cars aerodynamic wind tunnel (WT). The comparison confirms a good agreement between the experiments and the simulations. The resolved flow scales obtained by DDES give a further insight into differences in the wake flow characteristics between the configurations related to their contribution to drag.

scholarly journals CFD Validation of a Model Wind Turbine by Means of Improved and Delayed Detached Eddy Simulation in OpenFOAM

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1306
Author(s):  
Camilo Sedano ◽  
Frederik Berger ◽  
Hamid Rahimi ◽  
Omar Lopez Mejia ◽  
Martin Kühn ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Computational Models ◽  
Turbine Blades ◽  
Bending Moment ◽  
Computational Time ◽  
Experimental Investigations ◽  
Detached Eddy Simulation ◽  
Blade Root ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

With the ongoing increase in the size of wind turbines, experimental investigations have become more complicated and expensive. Therefore, computational models have proven to be a viable solution for design purposes. This article aims to validate CFD simulations of an experimental model wind turbine (MoWiTO 1.8) using Delayed Detached Eddy Simulation (DDES) and Improved DDES (IDDES) turbulence modelling approaches. For the purpose of validation, integral quantities (such as power, thrust, torque and blade-root bending moment in the flapwise direction) measured in the wind tunnel are compared with numerical results obtained with OpenFOAM. In general, the computational results show a very good agreement with the measurements for most of the monitored quantities. In particular, the blade-root bending moment presents the largest difference, taking into account that the simulation assumes the turbine blades are rigid. Nevertheless, the simulation does achieve in recreating the turbulent behavior as can be evidenced by the Power Spectral Density graphs, and the wake’s velocity measurements. In general, the IDDES turbulent model achieves a better agreement to the experimental results, while maintaining a very similar computational time as the DDES model.

Numerical study of the flow over the modified simple frigate shape

2020 ◽  
pp. 095441002097775
Author(s):  
Tong Li ◽  
Yibin Wang ◽  
Ning Zhao
Keyword(s):  
Bluff Body ◽  
Recirculation Zone ◽  
Numerical Study ◽  
Reference Value ◽  
Flow Fields ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Simulation Results

The simple frigate shape (SFS) as defined by The Technical Co-operative Program (TTCP), is a simplified model of the frigate, which helps to investigate the basic flow fields of a frigate. In this paper, the flow fields of the different modified SFS models, consisting of a bluff body superstructure and the deck, were numerically studied. A parametric study was conducted by varying both the superstructure length L and width B to investigate the recirculation zone behind the hangar. The size and the position of the recirculation zones were compared between different models. The numerical simulation results show that the size and the location of the recirculation zone are significantly affected by the superstructure length and width. The results obtained by Reynolds-averaged Navier-Stokes method were also compared well with both the time averaged Improved Delayed Detached-Eddy Simulation results and the experimental data. In addition, by varying the model size and inflow velocity, various flow fields were numerically studied, which indicated that the changing of Reynolds number has tiny effect on the variation of the dimensionless size of the recirculation zone. The results in this study have certain reference value for the design of the frigate superstructure.

scholarly journals Numerical Investigation on the Influence of the Streamlined Structures of the High-Speed Train’s Nose on Aerodynamic Performances

2021 ◽  
Vol 11 (2) ◽  
pp. 784
Author(s):  
Zhenxu Sun ◽  
Shuanbao Yao ◽  
Lianyi Wei ◽  
Yongfang Yao ◽  
Guowei Yang
Keyword(s):  
Drag Reduction ◽  
Pressure Distribution ◽  
Flow Separation ◽  
High Speed ◽  
Leeward Side ◽  
Detached Eddy Simulation ◽  
Side Force ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Asymmetrical Design

The structural design of the streamlined shape is the basis for high-speed train aerodynamic design. With use of the delayed detached-eddy simulation (DDES) method, the influence of four different structural types of the streamlined shape on aerodynamic performance and flow mechanism was investigated. These four designs were chosen elaborately, including a double-arch ellipsoid shape, a single-arch ellipsoid shape, a spindle shape with a front cowcatcher and a double-arch wide-flat shape. Two different running scenes, trains running in the open air or in crosswind conditions, were considered. Results reveal that when dealing with drag reduction of the whole train running in the open air, it needs to take into account how air resistance is distributed on both noses and then deal with them both rather than adjust only the head or the tail. An asymmetrical design is feasible with the head being a single-arch ellipsoid and the tail being a spindle with a front cowcatcher to achieve the minimum drag reduction. The single-arch ellipsoid design on both noses could aid in moderating the transverse amplitude of the side force on the tail resulting from the asymmetrical vortex structures in the flow field behind the tail. When crosswind is considered, the pressure distribution on the train surface becomes more disturbed, resulting in the increase of the side force and lift. The current study reveals that the double-arch wide-flat streamlined design helps to alleviate the side force and lift on both noses. The magnitude of side force on the head is 10 times as large as that on the tail while the lift on the head is slightly above that on the tail. Change of positions where flow separation takes place on the streamlined part is the main cause that leads to the opposite behaviors of pressure distribution on the head and on the tail. Under the influence of the ambient wind, flow separation occurs about distinct positions on the train surface and intricate vortices are generated at the leeward side, which add to the aerodynamic loads on the train in crosswind conditions. These results could help gain insight on choosing a most suitable streamlined shape under specific running conditions and acquiring a universal optimum nose shape as well.

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