scholarly journals CFD Analysis of Turbulence Models to Achieve the Digester Mixing Process

2018 ◽  
Author(s):  
Jorge Flores-Velazquez ◽  
Abraham Jesus Arzeta-Rios ◽  
Waldo Ojeda Bustamante ◽  
Teodoro Espinosa-Solares
Keyword(s):  
Turbulence Models ◽  
Cfd Analysis ◽  
Mixing Process

Study of the Change of Performance of an Elastic Vertical Hydrofoil With Deformation

2014 ◽  
Author(s):  
Alexander Führing ◽  
Subha Kumpaty ◽  
Chris Stack
Keyword(s):  
Water Flow ◽  
Lift Coefficient ◽  
Flow Analysis ◽  
Turbulence Models ◽  
Flow Property ◽  
Performance Data ◽  
Cfd Analysis ◽  
Ansys Fluent ◽  
Drag Forces ◽  
Fluid Flow Analysis

In external and internal fluid flow analysis using numerical methods, most attention is paid to the properties of the flow assuming absolute rigidity of the solid bodies involved. However, this is often not the case for water flow or other fluids with high density. The pressure forces cause the geometry to deform which in turn changes the flow properties around it. Thus, a one-way and two-way Fluid-Structure Interaction (FSI) coupling is proposed and compared to a CFD analysis of a windsurfing fin in order to quantify the differences in performance data as well as the properties of the flow. This leads to information about the necessity of the use of FSI in comparison to regular CFD analysis and gives indication of the value of the enhanced results of the deformable analysis applied to water flow around an elastically deformable hydrofoil under different angles of attack. The performance data and flow property evaluation is done in ANSYS Fluent using the k-ω SST and k-ε model with a y+ of 1 and 35 respectively in order to be able to compare the behavior of both turbulence models. It is found that the overall lift coefficient in general is lower and that the flow is less turbulent because of softer transition due to the deformed geometry reducing drag forces. It is also found that the deformation of the tip of the hydrofoil leads to vertical lift forces. For the FSI analysis, one-way and two-way coupling were incorporated leading to the ability to compare results. It has been found that one-way coupling is sufficient as long as there is no stall present at any time.

scholarly journals OPTIMALIZATION OF AFTERBURNER CHANNEL IN BIOMASS BOILER USING CFD ANALYSIS

2016 ◽  
Vol 56 (5) ◽  
pp. 379-387 ◽  
Author(s):  
Jiří Pospíšil ◽  
Martin Lisý ◽  
Michal Špiláček
Keyword(s):  
Cross Sections ◽  
Flue Gas ◽  
Air Distribution ◽  
Cfd Analysis ◽  
Mixing Process ◽  
Rectangular Duct ◽  
Biomass Boiler ◽  
Cross Section Area ◽  
Section Area ◽  
Secondary Air

This contribution presents the results of parametrical studies focused on the mixing process in a small rectangular duct within a biomass boiler. The first study investigates the influence of a local narrowing located in the central part of the duct. This narrowing works as an orifice with very simple rectangular geometry. Four different free cross sections of the orifice were considered in the center of the duct, namely 100%, 70%, 50%, 30% of free cross section area in the duct. The second study is focused on the investigation of the influence of secondary air distribution pipe diameter on the mixing process in a flue gas duct without a narrowing.

CFD Analysis of Stall in a Wells Turbine

2018 ◽  
Author(s):  
Kellis Kincaid ◽  
David W. MacPhee
Keyword(s):  
Source Code ◽  
Turbulence Models ◽  
Ocean Waves ◽  
Cfd Analysis ◽  
Oscillating Water Column ◽  
Blade Profile ◽  
Flow Conditions ◽  
Wells Turbine ◽  
Sst Model ◽  
Blade Shape

The Wells turbine is a self-rectifying device that employs a symmetrical blade profile, and is often used in conjunction with an oscillating water column to extract energy from ocean waves. The effects of solidity, angle of attack, blade shape and many other parameters have been widely studied both numerically and experimentally. To date, several 3-D numerical simulations have been performed using commercial software, mostly with steady flow conditions and employing various two-equation turbulence models. In this paper, the open source code Open-FOAM is used to numerically study the performance characteristics of a Wells turbine using a two-equation turbulence model, namely the Menter SST model, in conjunction with a transient fluid solver.

CFD Analysis of the Active Part of the HYPER Spallation Target

2006 ◽  
Author(s):  
Nam-il Tak ◽  
Chungho Cho ◽  
Tae-Yung Song
Keyword(s):  
Turbulence Models ◽  
Active Part ◽  
Beam Power ◽  
Cfd Analysis ◽  
Spallation Target ◽  
Power Extraction ◽  
Commercial Code ◽  
Driven System ◽  
Challenging Tasks ◽  
Computational Fluid Dynamics Cfd

KAERI (Korea Atomic Energy Research Institute) is developing an accelerator driven system (ADS) named HYPER (HYbrid Power Extraction Reactor) for a transmutation of long-lived nuclear wastes. One of the challenging tasks for the HYPER system is to design a large spallation target having a beam power of 15∼25 MW. The present paper focuses on the thermal-hydraulic performance of the active part of the HYPER target. Computational fluid dynamics (CFD) analysis was performed using a commercial code CFX 5.7.1. Several advanced turbulence models with different grid structures were applied. The CFX results show the significant impact of the turbulence model on the window temperature. It is concluded that experimental verifications are very important for the design of the HYPER target.

CFD Analysis of Industrial Gas Turbine Exhaust Diffusers

2002 ◽  
Author(s):  
V. Vassiliev ◽  
S. Irmisch ◽  
S. Florjancic
Keyword(s):  
Gas Turbine ◽  
Measurement Data ◽  
Turbulence Models ◽  
Cfd Analysis ◽  
Cfd Modelling ◽  
Gas Turbine Exhaust ◽  
Key Aspects ◽  
Industrial Gas Turbine ◽  
Turbine Exhaust

The key aspects for the reliable CFD modelling of exhaust diffusers are addressed in this paper. In order to identify adequate turbulence models a number of 2D diffuser configurations have been simulated using different turbulence models and results have been compared with measurements. An automated procedure for a time- and resource-efficient and accurate prediction of complex diffuser configuration is presented. The adequate definitions of boundary conditions for the diffuser simulation using this procedure are discussed. In the second part of this paper, the CFD procedure is being applied to investigate the role of secondary flow on axial diffusers. Prediction results are discussed and compared with available measurement data.

Micro Gas Turbine Combustion Chamber Design and CFD Analysis

2004 ◽  
Author(s):  
Joao Parente ◽  
Giulio Mori ◽  
Viatcheslav V. Anisimov ◽  
Giulio Croce
Keyword(s):  
Gas Turbine ◽  
Design Process ◽  
Preliminary Analysis ◽  
Cooling System ◽  
System Development ◽  
Experimental Testing ◽  
Flame Temperature ◽  
Turbulence Models ◽  
Cfd Analysis ◽  
Micro Gas Turbine

In the framework of the non-standard fuel combustion research in micro-small turbomachinery, a newly designed micro gas turbine combustor for a 100-kWe power plant in CHP configuration is under development at the Ansaldo Ricerche facilities. Combustor design starts from a single silo chamber shape with two fuel lines, and is associated with a radial swirler flame stabiliser. Lean premix technique is adopted to control both flame temperature and NOx production. Combustor design process envisages two major steps, i.e. diagnostics-focussed design for methane only and experimentally validated design optimisation with suitable burner adaptation to non-standard fuels. The former step is over, as the first prototype design is ready for experimental testing. Step two is now beginning with a preliminary analysis of the burner adaptation to non-standard fuels. The present paper focuses on the first step of the combustor development. In particular, main design criteria for both burner and liner cooling system development are presented. Besides, design process control invoked both 2D and 3D CFD analysis. Two turbulence models, FLUENT standard k-ε model and Reynolds Stress Model (RSM), are refereed and the results compared. Here both a detailed analysis of CFD results and a preliminary analysis of main chemical kinetic phenomena are discussed.

Mixing Field Analysis of a Gas Turbine Burner

2002 ◽  
Author(s):  
Peter Flohr ◽  
Patrick Schmitt ◽  
Christian Oliver Paschereit
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Numerical Study ◽  
Turbulence Models ◽  
Design Tool ◽  
Field Analysis ◽  
Mixing Process ◽  
Fuel Injector ◽  
Air Mixing ◽  
Gas Turbine Burner

An analytical and numerical study has been carried out with the view on the understanding of the physical mechanisms of the mixing process in a gas turbine burner. To this end, three methods at various levels of approximation have been used: At the simplest level an analytical model of the burner flow and the mixing process has been developed. It is demonstrated how this approach can be used to understand basic issues of the fuel-air mixing and how it can be applied as a design tool which guides the optimisation of a fuel injector device. At an intermediate level of approximation, steady-state CFD simulations, based on the k–ε- and RSM-turbulence models are used to describe the mixing process. All steady simulations fail to either predict the recirculation zone or the turbulence level correctly, and can therefore not be expected to capture the mixing correctly. At the most involved level of modelling time-accurate CFD based on unsteady RSM and LES-turbulence models are performed. The simulations show good agreement with experiments (and in the case of LES excellent agreement) for both, velocity and turbulence fields. Mixing predictions close to the fuel injectors suffer from a simplification used in the numerical setup, but the mixing field is predicted very well towards the exit of the burner. The contribution of the asymmetric coherent flow structure (which is associated with the internal recirculation zone) to the mixing process is quantified through a triple decomposition technique.

scholarly journals Numerical Simulation Of Supersonic Compression Ramp Flow

2021 ◽  
Vol 12 (6) ◽  
pp. 812-821
Author(s):  
Ki-Hyuk Yang Et.al
Keyword(s):  
Shock Wave ◽  
Adaptive Mesh Refinement ◽  
Mesh Refinement ◽  
Engineering Application ◽  
Turbulence Models ◽  
Adaptive Mesh ◽  
Equation Model ◽  
Prediction Performance ◽  
Cfd Analysis ◽  
Boundary Layer Interaction

Shock wave/boundary layer interaction (SWBLI) is a highly critical problem that occurs in aircraft in transonic or supersonic flow. This study performed CFD analysis of the supersonic ramp flow of freestream Mach number 2.79. To secure reliability of the CFD analysis, adaptive mesh refinement using a gradient p sensor was used. Through this, a grid of sufficient resolution was obtained for the region of shock wave, expansion wave, and flow separation. The prediction performance of 7 turbulence models that are widely used in engineering application were compared. The baseline k–ω two-equation model showed the best prediction performance, while the SST k–ω model, which is one of the most widely used two-equation models, and the 2 Reynolds stress models showed relatively poor prediction performance. In the SWBLI problem, the use of adaptive mesh refinement made it possible to secure sufficient grid resolution; meanwhile, comparison of the prediction performance of the various turbulence models confirmed that for the SWBLI problem, the generally used turbulence model was somewhat inappropriate.

scholarly journals Improving the methodology for calculation of energy losses in axial turbine cascades

2021 ◽  
pp. 104-109
Author(s):  
М.Ю. Левенталь ◽  
Ю.М. Погодин ◽  
Ю.Р. Миронов
Keyword(s):  
Standard Deviation ◽  
Turbulence Model ◽  
Empirical Model ◽  
Turbulence Models ◽  
Operating Parameters ◽  
Cfd Analysis ◽  
Sample Standard Deviation ◽  
Rans Model ◽  
Wide Range ◽  
Turbine Cascades

Представлена оценка неопределенности прогнозирования потерь энергии в решетках профилей осевых турбин. В сравнении с экспериментальными данными рассмотрены эмпирическая модель ЦИАМ и метод CFD анализа в рамках RANS модели. Геометрические и режимные параметры решеток профилей варьируются в широком диапазоне. Результаты CFD расчета отличаются существенно в зависимости от модели турбулентности. Наименьшая неопределенность получена для модели рейнольдсовых напряжений RSM. Определено выборочное стандартное относительное отклонение для анализируемой базы данных. Применительно к CFD расчету данное отклонение составило 18,6%, применительно к эмпирической модели ЦИАМ 46,4%. Разработана эмпирическая модель коррекции потерь полученных по результатам CFD анализа с моделью турбулентности RSM. Корректирующая функция включает в себя геометрические и режимные параметры решеток и особенности течения в межлопаточном канале (всего 14 параметров). Использование разработанного подхода позволило снизить неопределённость прогнозирования потерь в 2 раза. В результате работы выборочное стандартное относительное отклонение предсказания потерь для рассматриваемой базы решеток профилей составило 9,3%. Estimation of the uncertainty in predicting profile losses using various models was performed. In comparison with the experimental data, empirical model of CIAM and method of CFD analysis are considered. RANS models are used. The geometric and operating parameters of the analyzed turbine cascades vary over a wide range. Turbulence models strongly influence loss prediction uncertainty. The smallest uncertainty was obtained using the RSM turbulence model. The sample standard deviation for the considered turbine cascades base was determined. The deviation for CFD analysis is 18.6%. For the empirical model of CIAM the deviation is 46.4%. The new empirical model has been created to correct the results of calculating losses according to the RANS model using the RSM turbulence model. The corrective function takes into account the influence of the geometric and operating parameters of the turbine cascades and the features of the airfoil flow (14 parameters in total). The developed approach allows reducing the uncertainty in the estimation of losses according to the RANS model by 2 times. As a result, the sample standard deviation in the prediction of losses is 9.3% for the considered turbine cascades base.

Fuel Nozzle Aerodynamic Design Using CFD Analysis

1997 ◽  
Vol 119 (3) ◽  
pp. 527-534 ◽  
Author(s):  
D. S. Crocker ◽  
E. J. Fuller ◽  
C. E. Smith
Keyword(s):  
Fuel Injection ◽  
Swirling Flow ◽  
Turbulence Models ◽  
Cfd Analysis ◽  
Aerodynamic Design ◽  
Flow Area ◽  
Measured Velocity ◽  
Fuel Nozzle ◽  
Cfd Analyses ◽  
Good Agreement

The aerodynamic design of airflow passages in fuel injection systems can be significantly enhanced by the use of CFD analysis. Attempts to improve the efficiency of the fuel nozzle design process by using CFD analyses have generally been unsuccessful in the past due to the difficulties of modeling swirling flow in complex geometries. Some of the issues that have been obstacles to successful and timely analysis of fuel nozzle aerodynamics include grid generation, turbulence models, and definition of boundary conditions. This study attempts to address these obstacles and demonstrate a CFD methodology capable of modeling swirling flow within the internal air passages of fuel nozzles. The CFD code CFD-ACE was used for the analyses. Results of nonreacting analyses and comparison with experimental data are presented for three different fuel nozzles. The three nozzles have distinctly different designs (including axial and radial inflow swirlers) and thus demonstrate the flexibility of the design methodology. Particular emphasis is given to techniques involved in predicting the effective flow area (ACd) of the nozzles. Good agreement between CFD predictions of the ACd (made prior to experiments) and the measured ACd was obtained. Comparisons between predicted and measured velocity profiles also showed good agreement.

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