Coupled Aerothermal Modeling of a Rotating Cavity With Radial Inflow

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Zixiang Sun ◽  
Dario Amirante ◽  
John W. Chew ◽  
Nicholas J. Hills
Keyword(s):  
Response Times ◽  
Thermal Response ◽  
Turbulence Models ◽  
Cfd Modeling ◽  
Sector Model ◽  
Eddy Simulation ◽  
Cfd Models ◽  
Rotating Cavity ◽  
Blade Clearance ◽  
Coupled Solution

Flow and heat transfer in an aero-engine compressor disk cavity with radial inflow has been studied using computational fluid dynamics (CFD), large eddy simulation (LES), and coupled fluid/solid modeling. Standalone CFD investigations were conducted using a set of popular turbulence models along with 0.2 deg axisymmetric and a 22.5 deg discrete sector CFD models. The overall agreement between the CFD predictions is good, and solutions are comparable to an established integral method solution in the major part of the cavity. The LES simulation demonstrates that flow unsteadiness in the cavity due to the unstable thermal stratification is largely suppressed by the radial inflow. Steady flow CFD modeling using the axisymmetric sector model and the Spalart–Allmaras turbulence model was coupled with a finite element (FE) thermal model of the rotating cavity. Good agreement was obtained between the coupled solution and rig test data in terms of metal temperature. Analysis confirms that using a small radial bleed flow in compressor cavities is effective in reducing thermal response times for the compressor disks and that this could be applied in management of compressor blade clearance.

Coupled Aero-Thermal Modeling of a Rotating Cavity With Radial Inflow

2015 ◽  
Author(s):  
Zixiang Sun ◽  
Dario Amirante ◽  
John W. Chew ◽  
Nicholas J. Hills
Keyword(s):  
Response Times ◽  
Thermal Response ◽  
Turbulence Models ◽  
Cfd Modelling ◽  
Sector Model ◽  
Eddy Simulation ◽  
Cfd Models ◽  
Rotating Cavity ◽  
Blade Clearance ◽  
Coupled Solution

Flow and heat transfer in an aero-engine compressor disc cavity with radial inflow has been studied using computational fluid dynamics (CFD), large eddy simulation (LES) and coupled fluid/solid modelling. Standalone CFD investigations were conducted using a set of popular turbulence models along with 0.2° axisymmetric and a 22.5° discrete sector CFD models. The overall agreement between the CFD predictions is good, and solutions are comparable to an established integral method solution in the major part of the cavity. The LES simulation demonstrates that flow unsteadiness in the cavity due to the unstable thermal stratification is largely suppressed by the radial inflow. Steady flow CFD modelling using the axisymmetric sector model and the Spalart-Allmaras turbulence model was coupled with a finite element (FE) thermal model of the rotating cavity. Good agreement was obtained between the coupled solution and rig test data in terms of metal temperature. Analysis confirms that use of a small radial bleed flow in compressor cavities is effective in reducing thermal response times for the compressor discs and that this could be applied in management of compressor blade clearance.

scholarly journals CFD Modeling of Hydrocyclones—A Study of Efficiency of Hydrodynamic Reservoirs

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 118 ◽  
Author(s):  
Marvin Durango-Cogollo ◽  
Jose Garcia-Bravo ◽  
Brittany Newell ◽  
Andres Gonzalez-Mancera
Keyword(s):  
Pressure Drop ◽  
Separation Efficiency ◽  
Collection Efficiency ◽  
Saddle Points ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Cfd Modeling ◽  
Eddy Simulation ◽  
Discrete Phase ◽  
Rsm Model

The dynamics of hydrocyclones is complex, because it is a multiphase flow problem that involves interaction between a discrete phase and multiple continuum phases. The performance of hydrocyclones is evaluated by using Computational Fluid Dynamics (CFD), and it is characterized by the pressure drop, split water ratio, and particle collection efficiency. In this paper, a computational model to improve and evaluate hydrocyclone performance is proposed. Four known computational turbulence models (renormalization group (RNG) k- ε , Reynolds stress model (RSM), and large-eddy simulation (LES)) are implemented, and the accuracy of each for predicting the hydrocyclone behavior is assessed. Four hydrocyclone configurations were analyzed using the RSM model. By analyzing the streamlines resulting from those simulations, it was found that the formation of some vortices and saddle points affect the separation efficiency. Furthermore, the effects of inlet width, cone length, and vortex finder diameter were found to be significant. The cut-size diameter was decreased by 33% compared to the Hsieh experimental hydrocyclone. An increase in the pressure drop leads to high values of cut-size and classification sharpness. If the pressure drop increases to twice its original value, the cut-size and the sharpness of classification are reduced to less than 63% and 55% of their initial values, respectively.

scholarly journals CFD Turbulence Study of PWR Spacer-Grids in a Rod Bundle

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
C. Peña-Monferrer ◽  
J. L. Muñoz-Cobo ◽  
S. Chiva
Keyword(s):  
Mechanical Stability ◽  
Turbulence Models ◽  
Cfd Modeling ◽  
Spacer Grid ◽  
Pressurized Water ◽  
Spacer Grids ◽  
Eddy Simulation ◽  
Transient Nature ◽  
Rod Bundle ◽  
Wide Range

Nuclear fuel bundles include spacers essentially for mechanical stability and to influence the flow dynamics and heat transfer phenomena along the fuel rods. This work presents the analysis of the turbulence effects of a split-type and swirl-type spacer-grid geometries on single phase in a PWR (pressurized water reactor) rod bundle. Various computational fluid dynamics (CFD) calculations have been performed and the results validated with the experiments of the OECD/NEA-KAERI rod bundle CFD blind benchmark exercise on turbulent mixing in a rod bundle with spacers at the MATiS-H facility. Simulation of turbulent phenomena downstream of the spacer-grid presents high complexity issues; a wide range of length scales are present in the domain increasing the difficulty of defining in detail the transient nature of turbulent flow with ordinary turbulence models. This paper contains a complete description of the procedure to obtain a validated CFD model for the simulation of the spacer-grids. Calculations were performed with the commercial code ANSYS CFX using large eddy simulation (LES) turbulence model and the CFD modeling procedure validated by comparison with measurements to determine their suitability in the prediction of the turbulence phenomena.

Evaluation and application of advanced CFD models for rotating disc flows

2021 ◽  
pp. 095440622110138
Author(s):  
Feng Gao ◽  
John W Chew
Keyword(s):  
Large Eddy Simulation ◽  
Turbulence Models ◽  
Published Data ◽  
Complex Flows ◽  
Rotating Disc ◽  
Eddy Simulation ◽  
Cfd Models ◽  
Turbulent Transition ◽  
Large Eddy ◽  
Buoyancy Driven Convection

This paper addresses limitations of widely used Reynolds-averaged turbulence models (RANS) for prediction of gas turbine internal air systems. Results from direct numerical simulation (DNS), wall-resolved large-eddy simulation (LES), wall-modelled large-eddy simulation (WMLES), and RANS for benchmark test cases are compared. For rotor-stator disc cavity flows results for mean velocities, velocity fluctuations, rotor torque and laminar-turbulent transition are considered and compared with published data. For cavities between co-rotating discs attention is focused on buoyancy-driven convection in the centrifugal force field. It is concluded that WMLES is suitable for application in engine conditions, offering better accuracy than RANS in some critical applications. This confirms recently published results for turbine rim sealing and is further illustrated by application to convection in a sealed cavity at higher Rayleigh number than is practical with DNS or wall-resolved LES. The results show that the approximate near-wall treatment gives reasonable results for complex flows and extend previous studies to higher speed rig conditions where Eckert number effects become significant.

scholarly journals Performance Prediction of a Hard-Chine Planing Hull by Employing Different CFD Models

2021 ◽  
Vol 9 (5) ◽  
pp. 481
Author(s):  
Azim Hosseini ◽  
Sasan Tavakoli ◽  
Abbas Dashtimanesh ◽  
Prasanta K. Sahoo ◽  
Mihkel Kõrgesaar
Keyword(s):  
Water Flow ◽  
Performance Prediction ◽  
Cfd Modeling ◽  
Computational Time ◽  
Resistance Force ◽  
Stagnation Line ◽  
Mesh Structure ◽  
Cfd Models ◽  
High Speeds ◽  
Des Model

This paper presents CFD (Computational Fluid Dynamics) simulations of the performance of a planing hull in a calm-water condition, aiming to evaluate similarities and differences between results of different CFD models. The key differences between these models are the ways they use to compute the turbulent flow and simulate the motion of the vessel. The planing motion of a vessel on water leads to a strong turbulent fluid flow motion, and the movement of the vessel from its initial position can be relatively significant, which makes the simulation of the problem challenging. Two different frameworks including k-ε and DES (Detached Eddy Simulation) methods are employed to model the turbulence behavior of the fluid motion of the air–water flow around the boat. Vertical motions of the rigid solid body in the fluid domain, which eventually converge to steady linear and angular displacements, are numerically modeled by using two approaches, including morphing and overset techniques. All simulations are performed with a similar mesh structure which allows us to evaluate the differences between results of the applied mesh motions in terms of computation of turbulent air–water flow around the vessel. Through quantitative comparisons, the morphing technique has been seen to result in smaller errors in the prediction of the running trim angle at high speeds. Numerical observations suggest that a DES model can modify the accuracy of the morphing mesh simulations in the prediction of the trim angle, especially at high-speeds. The DES model has been seen to increase the accuracy of the model in the computation of the resistance of the vessel in a high-speed operation, as well. This better level of accuracy in the prediction of resistance is a result of the calculation of the turbulent eddies emerging in the water flow in the downstream zone, which are not captured when a k-ε framework is employed. The morphing approach itself can also increase the accuracy of the resistance prediction. The overset method, however, overpredicts the resistance force. This overprediction is caused by the larger vorticity, computed in the direction of the waves, generated under the bow of the vessel. Furthermore, the overset technique is observed to result in larger hydrodynamic pressure on the stagnation line, which is linked to the greater trim angle, predicted by this approach. The DES model is seen to result in extra-damping of the second and third crests of transom waves as it calculates the stronger eddies in the wake of the boat. Overall, a combination of the morphing and DES models is recommended to be used for CFD modeling of a planing hull at high-speeds. This combined CFD model might be relatively slower in terms of computational time, but it provides a greater level of accuracy in the performance prediction, and can predict the energy damping, developed in the surrounding water. Finally, the results of the present paper demonstrate that a better level of accuracy in the performance prediction of the vessel might also be achieved when an overset mesh motion is used. This can be attained in future by modifying the mesh structure in such a way that vorticity is not overpredicted and the generated eddies, emerging when a DES model is employed, are captured properly.

scholarly journals Comparative Study of Different Turbulence Models for Cavitational Flows around NACA0012 Hydrofoil

2021 ◽  
Vol 9 (7) ◽  
pp. 742
Author(s):  
Minsheng Zhao ◽  
Decheng Wan ◽  
Yangyang Gao
Keyword(s):  
Angle Of Attack ◽  
Large Angle ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Specific Information ◽  
Cloud Cavitation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Shedding Frequency ◽  
Reynolds Average

The present work focuses on the comparison of the numerical simulation of sheet/cloud cavitation with the Reynolds Average Navier-Stokes and Large Eddy Simulation(RANS and LES) methods around NACA0012 hydrofoil in water flow. Three kinds of turbulence models—SST k-ω, modified SST k-ω, and Smagorinsky’s model—were used in this paper. The unstable sheet cavity and periodic shedding of the sheet/cloud cavitation were predicted, and the simulation results, namelycavitation shape, shedding frequency, and the lift and the drag coefficients of those three turbulence models, were analyzed and compared with each other. The numerical results above were basically in accordance with experimental ones. It was found that the modified SST k-ω and Smagorinsky turbulence models performed better in the aspects of cavitation shape, shedding frequency, and capturing the unsteady cavitation vortex cluster in the developing and shedding period of the cavitation at the cavitation number σ = 0.8. At a small angle of attack, the modified SST k-ω model was more accurate and practical than the other two models. However, at a large angle of attack, the Smagorinsky model of the LES method was able to give specific information in the cavitation flow field, which RANS method could not give. Further study showed that the vortex structure of the wing is the main cause of cavitation shedding.

scholarly journals Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 198
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Orientation Angle ◽  
Turbulence Models ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

A Joint-Industry Effort to Develop and Verify CFD Modeling Practice for Vortex-Induced Motion of a Deep-Draft Semi-Submersible

2021 ◽  
Author(s):  
Hyunchul Jang ◽  
Dae-Hyun Kim ◽  
Madhusuden Agrawal ◽  
Sebastien Loubeyre ◽  
Dongwhan Lee ◽  
...  
Keyword(s):  
Test Data ◽  
Model Test ◽  
Working Group ◽  
Cfd Modeling ◽  
Physical Model Test ◽  
Mooring Lines ◽  
Cfd Models ◽  
Induced Motion ◽  
Modeling Practice ◽  
Decay Tests

Abstract Platform Vortex Induced Motion (VIM) is an important cause of fatigue damage on risers and mooring lines connected to deep-draft semi-submersible floating platforms. The VIM design criteria have been typically obtained from towing tank model testing. Recently, computational fluid dynamics (CFD) analysis has been used to assess the VIM response and to augment the understanding of physical model test results. A joint industry effort has been conducted for developing and verifying a CFD modeling practice for the semi-submersible VIM through a working group of the Reproducible Offshore CFD JIP. The objectives of the working group are to write a CFD modeling practice document based on existing practices validated for model test data, and to verify the written practice by blind calculations with five CFD practitioners acting as verifiers. This paper presents the working group’s verification process, consisting of two stages. In the initial verification stage, the verifiers independently performed free-decay tests for 3-DOF motions (surge, sway, yaw) to check if the mechanical system in the CFD model is the same as in the benchmark test. Additionally, VIM simulations were conducted at two current headings with a reduced velocity within the lock-in range, where large sway motion responses are expected,. In the final verification stage, the verifiers performed a complete set of test cases with small revisions of their CFD models based on the results from the initial verification. The VIM responses from these blind calculations are presented, showing close agreement with the model test data.

Optimization Method of the Multistage Axial Compressors Using CFD Simulation

2021 ◽  
pp. 2141006
Author(s):  
Grigorii Popov ◽  
Igor Egorov ◽  
Evgenii Goriachkin ◽  
Oleg Baturin ◽  
Daria Kolmakova ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Optimization Problems ◽  
Search Algorithm ◽  
Pressure Ratio ◽  
Optimization Method ◽  
Cfd Modeling ◽  
Turbine Engines ◽  
Stability Margins ◽  
Axial Compressors ◽  
Cfd Models

The current level of numerical methods of gas dynamics makes it possible to optimize compressors using 3D CFD models. However, the methods and means are not sufficiently developed for their wide application. This paper describes a new method for the optimization of multistage axial compressors based on 3D CFD modeling and summarizes the experience of its application. The developed method is a complex system of interconnected components (an effective mathematical model, a parameterizer, and an optimum search algorithm). The use of the method makes it possible to improve or provide the necessary values of the main gas-dynamic parameters of the compressor by changing the shape of the blades and their relative position. The method was tested in solving optimization problems for multistage axial compressors of gas turbine engines (the number of stages from 3 to 15). As a result, an increase in efficiency, pressure ratio, and stability margins was achieved. The presented work is a summary of a long-years investigation of the research team and aims at creating a complete picture of the obtained results for the reader. A brief description of the results of industrial compresses optimization contained in the paper is given as an illustration of the effectiveness of the developed methods.

Large Eddy Simulations of a Hydrocyclone

2002 ◽  
Author(s):  
Francisco Jose´ de Souza ◽  
Aristeu Silveira Neto
Keyword(s):  
Turbulence Models ◽  
Fluid Flows ◽  
Scale Model ◽  
Staggered Grid ◽  
Subgrid Scale ◽  
Step Method ◽  
Fractional Step Method ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Subgrid Scale Modeling

Subgrid-scale modeling, which characterizes Large Eddy Simulation (LES), has been used to predict the behavior of a water-fed hydrocyclone operating without an air core. The governing equations were solved by a fractional step method on a staggered grid. The Smagorinsky subgrid-scale model was employed to account for turbulent effects. Numerical results actually capture the main features of the flow pattern and agree reasonably well with experiments, suggesting that LES represents an interesting alternative to classical turbulence models when applied to the numerical solution of fluid flows within hydrocyclones.

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