Large Eddy Simulation of the Vortex End in Reverse-Flow Centrifugal Separators

2009 ◽  
Author(s):  
Gleb I. Pisarev ◽  
Alex C. Hoffmann ◽  
Weiming Peng ◽  
Henk A. Dijkstra ◽  
Theodore E. Simos ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Reverse Flow ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Predicting Unsteady Loads in Marine Propulsor Crashback Using Large Eddy Simulation

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Hyunchul Jang ◽  
Aman Verma ◽  
Krishnan Mahesh
Keyword(s):  
Large Eddy Simulation ◽  
Reverse Flow ◽  
Reverse Direction ◽  
Unsteady Forces ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean ◽  
Submarine Hull ◽  
Marine Propulsor ◽  
Good Agreement

Propulsor crashback is an off-design operating condition where a propulsor rotates in the reverse direction to yield negative thrust. Crashback is characterized by the interaction of the free stream with the reverse flow generated by propulsor rotation. This causes a highly unsteady vortex ring which leads to flow separation and unsteady forces and moments on the blades. Large eddy simulation (LES) is performed for marine propulsors in crashback for various configurations and advance ratios and validated against experiments. The predictive capability of LES as a tool for propulsor crashback is demonstrated on an open propulsor, open propulsor with a submarine hull, and ducted propulsor with and without stator blades. LES is in good agreement with experiments for the mean and RMS levels, and spectra of the unsteady loads on the propulsors.

Large eddy simulation of the influence of synthetic inlet turbulence on a practical aeroengine combustor with counter-rotating swirler

2017 ◽  
Vol 233 (3) ◽  
pp. 978-990 ◽  
Author(s):  
Yu Zhou ◽  
Yuan Huang ◽  
Zhongqiang Mu
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Reverse Flow ◽  
Boundary Layer Transition ◽  
Wall Region ◽  
Inlet Condition ◽  
Eddy Simulation ◽  
Large Eddy

To study the influence of inlet turbulence on the prediction of flow structure in practical aeroengine combustor, large eddy simulation with dynamic Smagorinsky subgrid model is used to explore the complex unsteady flow field in a single burner of a typical aeroengine combustor with two-stage counter-rotating swirler. The complex geometric configuration including all film cooling holes is fully simulated without any conventional simplification in order to reduce the modeling errors. First, unsteady process that flow developing from static to statistically stationary state is fully simulated under laminar inlet condition to obtain a fundamental understanding of flow characteristics in the combustor. Afterwards, synthetic eddy method is utilized to generate a turbulent inlet condition so that a perturbation with about 5% turbulence intensity is superimposed to the inlet plane. Simulation result shows that for the laminar inflow case, flow separation occurs in the near-wall region of the diffusion section, inducing a boundary layer transition and consequently introducing turbulence with nonuniformity in space before the swirler. In contrast, synthesized inflow generated under turbulent inlet condition by synthetic eddy method is more spatially homogeneous. Time-averaged flow field inside the swirler cup reveals that turbulent inflow ultimately causes the swirling flow with higher rotating speed in central region and more uniform distribution along the circumferential direction. It also enhances the transverse jet flow from primary holes and reverse flow in the central recirculation zone, and makes streamlines corresponding to the recirculation vortices more symmetrical on central profile. Maximum recirculating velocity predicted in central recirculation zone is −27.65 m/s and −17.86 m/s in turbulent and laminar case respectively, and corresponding total pressure recovery coefficient is 96.03% and 96.81%.

Large Eddy Simulation of Film Cooling Flow Above a Flat Plate From Inclined Cylindrical Holes

2006 ◽  
Author(s):  
Ioulia V. Iourokina ◽  
Sanjiva K. Lele
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Reverse Flow ◽  
Vortex Pair ◽  
Short Film ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Surface Time ◽  
Large Eddy ◽  
Negative Effect

Large Eddy Simulation of a realistic film cooling configuration is performed, consisting of a large plenum feeding a periodic array of short film cooling holes with length to diameter ratio L/d = 3.5. Film cooling jets are issued at 35 degrees into the turbulent crossflow boundary layer above the flat surface. Time-averaged flowfield is analyzed to reveal steady and unsteady structures occurring as a result of plenum-jet-crossflow interactions. Among these structures are the flow separation inside the film-hole, reverse flow zone right behind the jet injection and the counter-rotating vortex pair in the wake of the jet. All of these structures influence the wall temperature distribution and have a negative effect on film cooling effectiveness.

Large eddy simulation of flow around a reverse rotating propeller

2013 ◽  
Vol 729 ◽  
pp. 151-179 ◽  
Author(s):  
Hyunchul Jang ◽  
Krishnan Mahesh
Keyword(s):  
Large Eddy Simulation ◽  
Vortex Ring ◽  
Free Stream ◽  
Reverse Flow ◽  
Separated Flow ◽  
High Amplitude ◽  
Reverse Direction ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

AbstractThis paper studies the flow around a propeller rotating in the reverse direction in a uniform free stream. Large eddy simulation is used to study this massively separated flow at a Reynolds number of 480 000 and advance ratios $J= - 0. 5$, $- 0. 7$ and $- 1. 0$. Simulations are performed on two grids; statistics of the loads and velocity field around the propeller show encouraging agreement between the two grids and with experiment. The impact of advance ratio is discussed, and a physical picture of the unsteady flow and its influence on the propeller loads is proposed. An unsteady vortex ring is formed in the vicinity of the propeller disk due to the interaction between the free stream and the reverse flow produced by the reverse rotation. The flow is separated in the blade passages; the most prominent is the separation along the sharp edge of the blade on the downstream side of the blade. This separation results in high-amplitude, transient propeller loads. Conditional averaging is used to describe the statistically relevant events that determine low- and high-amplitude thrust and side-forces. The vortex ring is closer and the reverse flow induced by propeller rotation is lower when the loads are high. The propeller loads scale with $\rho {U}^{2} $ for $J\lt - 0. 7$ and with $\rho {n}^{2} {D}^{2} $ for $J\gt - 0. 7$.

Large Eddy Simulation of the vortex end in reverse-flow centrifugal separators

2011 ◽  
Vol 217 (11) ◽  
pp. 5016-5022 ◽  
Author(s):  
Gleb I. Pisarev ◽  
Alex C. Hoffmann ◽  
Weiming Peng ◽  
Henk A. Dijkstra
Keyword(s):  
Large Eddy Simulation ◽  
Reverse Flow ◽  
Eddy Simulation ◽  
Large Eddy

Large eddy simulation coupled with immersed boundary method for turbulent flows over a backward facing step

2020 ◽  
pp. 095440622095489
Author(s):  
Dandan Yang ◽  
Sida He ◽  
Lian Shen ◽  
Xianwu Luo
Keyword(s):  
Large Eddy Simulation ◽  
Flow Separation ◽  
Reverse Flow ◽  
Immersed Boundary ◽  
Reattachment Length ◽  
Backward Facing Step ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Ib Method

In the present work, large eddy simulation coupled with immersed boundary (LES-IB) method is applied to simulate a backward facing step (BFS) flow, which is a canonical fluid dynamics problem involving flow separation, recirculation and reattachment that are common in many practical applications. The computed reattachment length, a primary parameter to evaluate the overall performance of the numerical method, shows promising accuracy in the present work compared to the alternative numerical simulations. Based on the mean velocity profiles at four representative locations, there is fairly well quantitative agreement among the present LES-IB, DNS and the experiment. The results reveal that the reverse flow in the reattachment region leads to little over-prediction of the reattachment length compared to the DNS result. Furthermore, second-order statistics are in good agreement with the reference data in spite of discrepancies in the recirculation and reattachment region owing to complex flow structure, verifying the accuracy of the present method. In addition, the instantaneous flow fields are also analyzed to show the capability of the present LES-IB method in vortex-capture, and one may see the transient process of flow separation based on the analysis of Lagrangian coherent structure (LCS).

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