Large-Eddy Simulation of Shock-Induced Flow Separation Control Using SparkJet Concept

2016 ◽  
Author(s):  
Guang Yang ◽  
Yufeng Yao ◽  
Jian Fang ◽  
Tian Gan ◽  
Lipeng Lu
Keyword(s):  
Large Eddy Simulation ◽  
Flow Separation ◽  
Separation Control ◽  
Flow Separation Control ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Induced Flow

Large-Eddy Simulation of Separation Control for Flow over a Wall-Mounted Hump

AIAA Journal ◽  
2007 ◽  
Vol 45 (11) ◽  
pp. 2643-2660 ◽  
Author(s):  
Philip E. Morgan ◽  
Donald P. Rizzetta ◽  
Miguel R. Visbal
Keyword(s):  
Large Eddy Simulation ◽  
Separation Control ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Investigation of flow separation in a centrifugal pump impeller based on improved delayed detached eddy simulation method

2019 ◽  
Vol 11 (12) ◽  
pp. 168781401989783
Author(s):  
Yun Ren ◽  
Zuchao Zhu ◽  
Denghao Wu ◽  
Xiaojun Li ◽  
Lanfang Jiang
Keyword(s):  
Large Eddy Simulation ◽  
Centrifugal Pump ◽  
Flow Separation ◽  
Hybrid Algorithm ◽  
Internal Flow ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes ◽  
Vorticity Flux

The mechanism of flow separation in the impeller of a centrifugal pump with a low specific speed was explored by experimental, numerical, and theoretical methods. A novel delayed Reynolds-averaged Navier–Stokes/large eddy simulation hybrid algorithm combined with a rotation and curvature correction method was developed to calculate the inner flow field of the original pump for the large friction loss in the centrifugal impeller, high adverse pressure gradient, and large blade curvature. Boundary vorticity flux theory was introduced for internal flow diagnosis, and the relative velocity vector near the surface of the blade and the distribution of the dimensionless pressure coefficient was analyzed. The validity of the numerical method was verified, and the location of the backflow area and its flow features were determined. Finally, based on flow diagnosis, the geometric parameters influencing the flow state of the impeller were specifically adjusted to obtain a new design impeller. The results showed that the distribution of the boundary vorticity flux peak values, the skin friction streamline, and near-wall relative velocities improved significantly after the design change. In addition, the flow separation was delayed, the force applied on the blade was improved, the head under the part-load condition was improved, and the hydraulic efficiency was improved over the global flow ranges. It was demonstrated that the delayed Reynolds-averaged Navier–Stokes/large eddy simulation hybrid algorithm was capable to capture the separation flow in a centrifugal pump, and the boundary vorticity flux theory was suitable for the internal flow diagnosis of centrifugal pump.

Large Eddy Simulation and CDNS Investigation of T106C Low-Pressure Turbine

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Site Hu ◽  
Chao Zhou ◽  
Zhenhua Xia ◽  
Shiyi Chen
Keyword(s):  
Large Eddy Simulation ◽  
Flow Separation ◽  
Separated Flow ◽  
Low Pressure ◽  
Secondary Flows ◽  
Computational Domain ◽  
Suction Surface ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy

This study investigates the aerodynamic performance of a low-pressure turbine, namely the T106C, by large eddy simulation (LES) and coarse grid direct numerical simulation (CDNS) at a Reynolds number of 100,000. Existing experimental data were used to validate the computational fluid dynamics (CFD) tool. The effects of subgrid scale (SGS) models, mesh densities, computational domains and boundary conditions on the CFD predictions are studied. On the blade suction surface, a separation zone starts at a location of about 55% along the suction surface. The prediction of flow separation on the turbine blade is always found to be difficult and is one of the focuses of this work. The ability of Smagorinsky and wall-adapting local eddy viscosity (WALE) model in predicting the flow separation is compared. WALE model produces better predictions than the Smagorinsky model. CDNS produces very similar predictions to WALE model. With a finer mesh, the difference due to SGS models becomes smaller. The size of the computational domain is also important. At blade midspan, three-dimensional (3D) features of the separated flow have an effect on the downstream flows, especially for the area near the reattachment. By further considering the effects of endwall secondary flows, a better prediction of the flow separation near the blade midspan can be achieved. The effect of the endwall secondary flow on the blade suction surface separation at the midspan is explained with the analytical method based on the Biot–Savart Law.

Large-Eddy Simulation of Flow over a Wall-Mounted Hump with Separation Control

AIAA Journal ◽  
2006 ◽  
Vol 44 (11) ◽  
pp. 2571-2577 ◽  
Author(s):  
Donghyun You ◽  
Meng Wang ◽  
Parviz Moin
Keyword(s):  
Large Eddy Simulation ◽  
Separation Control ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Compressible Large-Eddy Simulation of Separation Control on a Wall-Mounted Hump

AIAA Journal ◽  
2010 ◽  
Vol 48 (6) ◽  
pp. 1098-1107 ◽  
Author(s):  
Jennifer A. Franck ◽  
Tim Colonius
Keyword(s):  
Large Eddy Simulation ◽  
Separation Control ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Effect of the Inlet Boundary Conditions on the Flow over Complex Terrain Using Large Eddy Simulation

Designs ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 34
Author(s):  
Yi Wang ◽  
Giulio Vita ◽  
Bruño Fraga ◽  
Jianchun Wang ◽  
Hassan Hemida
Keyword(s):  
Large Eddy Simulation ◽  
Boundary Conditions ◽  
Flow Separation ◽  
Bubble Size ◽  
Flow Region ◽  
Eddy Simulation ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Simulation Results ◽  
Case Based

For large eddy simulation, it is critical to choose the suitable turbulent inlet boundary condition as it significantly affects the calculated flow field. In this paper, the effect of different inlet boundary conditions, including random method (RAND), Lund method, and divergence-free synthetic eddies method (DFSEM), on the flow in a channel with a hump are investigated through large-eddy simulation. The simulation results are further compared with experimental data. It has been found that turbulence is nearly fully developed in the case based on the Lund method, not fully developed in the case based on DFSEM, and not developed in the case based on the RAND method. In the flow region before the hump, mean velocity profiles in the case applying the Lund method gradually fit the law of the wall as the main flow moves towards the hump, but the simulation results based on the RAND and DFSEM methods cannot fit the wall function. In the flow region after the hump, cases applying Lund and DFSEM methods could relative precisely predict the size of turbulent bubble and turbulent statistics profiles. Meanwhile, the case based on the RAND method cannot capture the positions of flow separation and re-attachment point and overestimates the turbulent bubble size. From this research, it could be found that different turbulent inflow generation methods have a manifested impact on the flow separation and re-attachment after the hump. If the coherent turbulence is maintained in the approach flow, even though turbulent intensity is not large enough, the simulation can still predict the flow separation and turbulent bubble size relative precisely.

Large-Eddy Simulation of Buoyancy-Induced Flow in a Sealed Rotating Cavity

2018 ◽  
Author(s):  
Diogo B. Pitz ◽  
John W. Chew ◽  
Olaf Marxen
Keyword(s):  
Large Eddy Simulation ◽  
Boundary Layers ◽  
Flow Structure ◽  
Flow Characteristics ◽  
Global Features ◽  
Eddy Simulation ◽  
Rotating Cavity ◽  
Large Eddy ◽  
Induced Flow ◽  
Buoyancy Induced Flow

Buoyancy-induced flows occur in the rotating cavities of gas turbine internal air systems, and are particularly challenging to model due to their inherent unsteadiness. While the global features of such flows are well documented, detailed analyses of the unsteady structure and turbulent quantities have not been reported. In this work we use a high-order numerical method to perform large-eddy simulation (LES) of buoyancy-induced flow in a sealed rotating cavity with either adiabatic or heated disks. New insight is given into long-standing questions regarding the flow characteristics and nature of the boundary layers. The analyses focus on showing time-averaged quantities, including temperature and velocity fluctuations, as well as on the effect of the centrifugal Rayleigh number on the flow structure. Using velocity and temperature data collected over several revolutions of the system, the shroud and disk boundary layers are analysed in detail. The instantaneous flow structure contains pairs of large, counter-rotating convection rolls, and it is shown that unsteady laminar Ekman boundary layers near the disks are driven by the interior flow structure. The shroud thermal boundary layer scales as approximately Ra−1/3, in agreement with observations for natural convection under gravity.

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