Analysis of a New Adjustable Mixer Base on Large Eddy Simulation

2012 ◽  
Vol 594-597 ◽  
pp. 2763-2769
Author(s):  
Xin Nie ◽  
Lin Xiang Ding ◽  
Bing Guo ◽  
Li Bo Chen ◽  
Hua Chen Pan
Keyword(s):  
Large Eddy Simulation ◽  
Colloidal Particles ◽  
Internal Flow ◽  
Mixing Efficiency ◽  
Eddy Simulation ◽  
Large Eddy ◽  
New Type ◽  
Speed Change ◽  
Large Velocity Gradient ◽  
Vortex Diffusion

Abstract. This paper presents a new type of adjustable mixing equipment, and the internal flow field of the adjustable mixer have been studied by using the model of LES(Large eddy simulation),and the pressure loss, the speed change and vortex scale have been studied. In conclusion, along with blades angle and number increases, the flow resistance increases violently, so the range of blade rotating angle should be controlled within 30 degrees. As the depth of the pipeline velocity is increasingly large, large velocity gradient is contributed to the collisions between the colloidal particles. In pre-mixed, the vortex effect of the pipeline highly enhances the vortex diffusion, and improves the mixing efficiency. The vortex strength will be reinforced and dimension will be reduced, with the vanes cutting the flow, which can help flocculation.

scholarly journals Large-Eddy Simulation of Internal Flow through Human Vocal Folds

2018 ◽  
Vol 180 ◽  
pp. 02054
Author(s):  
Martin Lasota ◽  
Petr Šidlof
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Internal Flow ◽  
Vocal Folds ◽  
Computational Domain ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Scale Models ◽  
Large Eddy

The phonatory process occurs when air is expelled from the lungs through the glottis and the pressure drop causes flow-induced oscillations of the vocal folds. The flow fields created in phonation are highly unsteady and the coherent vortex structures are also generated. For accuracy it is essential to compute on humanlike computational domain and appropriate mathematical model. The work deals with numerical simulation of air flow within the space between plicae vocales and plicae vestibulares. In addition to the dynamic width of the rima glottidis, where the sound is generated, there are lateral ventriculus laryngis and sacculus laryngis included in the computational domain as well. The paper presents the results from OpenFOAM which are obtained with a large-eddy simulation using second-order finite volume discretization of incompressible Navier-Stokes equations. Large-eddy simulations with different subgrid scale models are executed on structured mesh. In these cases are used only the subgrid scale models which model turbulence via turbulent viscosity and Boussinesq approximation in subglottal and supraglottal area in larynx.

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.

J1050504 Large Eddy Simulation of internal flow of a centrifugal blower with scroll

2015 ◽  
Vol 2015 (0) ◽  
pp. _J1050504--_J1050504-
Author(s):  
Yoshinobu Yamade ◽  
Taku Iwase ◽  
Yutaka Ohta ◽  
Yang Guo ◽  
Chisachi Kato
Keyword(s):  
Large Eddy Simulation ◽  
Internal Flow ◽  
Centrifugal Blower ◽  
Eddy Simulation ◽  
Large Eddy

Examine Applicability of the RANS and LES Method on Numerical Simulation of Centrifugal Pump

2011 ◽  
Vol 55-57 ◽  
pp. 582-586
Author(s):  
Shu Jia Zhang ◽  
Yue Ping Tong ◽  
Le Hu
Keyword(s):  
Numerical Simulation ◽  
Large Eddy Simulation ◽  
Centrifugal Pump ◽  
Power Efficiency ◽  
Internal Flow ◽  
Equation Model ◽  
Eddy Simulation ◽  
Simulated Performance ◽  
Large Eddy ◽  
Performance Curves

In order to examine applicability of the Reynolds-Averaged Navier-Stokes （RANS）using Reynolds Stress equation Model (RSM) and the Large Eddy Simulation (LES) in numerical simulation of centrifugal pump, a series of 3D numerical simulation at the design point and at six off-design points were carried out with the two methods. The object is based on IS80-65-160 centrifugal pump. According to the results obtained, head, shaft power, efficiency of pump were calculated, the simulated performance curves of a centrifugal pump is processed. The simulated performance curves of a centrifugal pump were compared with the experimental performance curves. It was confirmed that RANS were suitable for the numerical simulation of the internal flow inside a centrifugal pump. But the result of LES is not very good if the same gambit which is suitable for RANS was used. Therefore, the computer resources, not propose the Large Eddy Simulation (LES) method in numerical simulations of centrifugal pump.

1007 Large Eddy Simulation of Internal Flow of Centrifugal Blower at Off Design Point

2014 ◽  
Vol 2014 (0) ◽  
pp. _1007-1_-_1007-4_
Author(s):  
Yoshinobu YAMADE ◽  
Taku IWASE ◽  
Yutaka OHTA ◽  
Yang GUO ◽  
Chisachi KATO
Keyword(s):  
Large Eddy Simulation ◽  
Internal Flow ◽  
Centrifugal Blower ◽  
Design Point ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals A formulation of convective entrainment in terms of mixing efficiency

2007 ◽  
Vol 580 ◽  
pp. 169-178 ◽  
Author(s):  
C. CHEMEL ◽  
C. STAQUET
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Ground Surface ◽  
Mixing Efficiency ◽  
Order Model ◽  
Direct Computation ◽  
First Order ◽  
Eddy Simulation ◽  
Large Eddy

The entrainment across a stably stratified interface forced by convective motions is discussed in the light of the mixing efficiency of the entrainment process. The context is the convectively driven atmospheric boundary layer and we focus on the regime of equilibrium entrainment, i.e. when the boundary-layer evolution is in a quasi-steady state. The entrainment law is classically based on the ratio R of the negative of the heat flux at the interface to the heat flux at the ground surface. We propose a parameterization for R that involves the mixing efficiency and the thickness of the interface, which matches well the direct computation of R from a high-resolution large-eddy simulation. This result enables us to derive modified expressions for the classical entrainment laws (the so-called zero- and first-order models) as a function of the mixing efficiency. We show that, when the thickness of the interface is ignored (zero-order model), the scaling factor A in the entrainment law is the flux Richardson number. This parameterization of A is further improved when the thickness of the interface is considered (first-order model), as shown by the direct computation of A from the large-eddy simulation.

Flow characteristics prediction in pump mode of a pump turbine using large eddy simulation

2016 ◽  
Vol 231 (5) ◽  
pp. 961-977 ◽  
Author(s):  
De-You Li ◽  
Lei Han ◽  
Hong-Jie Wang ◽  
Ru-Zhi Gong ◽  
Xian-Zhu Wei ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Pump Mode ◽  
Pump Turbine ◽  
Recirculation Flow ◽  
Eddy Simulation ◽  
Eddy Viscosity Model ◽  
Large Eddy ◽  
Operating Points

To obtain more accurate flow characteristics of pump turbines, the method of large eddy simulation with wall-adapting local eddy viscosity model is applied in simulating several operating points in the pump mode. Firstly, based on the experimental validation, the method of large eddy simulation could better predict the external performance and internal flow characteristics in a pump turbine in the pump mode compared with the method of Reynolds-averaged Navier–Stokes with two-equation turbulence model shear stress transport k–ω. Then, flow characteristics under 1.00 QBEP (best efficiency point), 0.91 QBEP, 0.88 QBEP, and 0.85 QBEP operating points are investigated to find out the causes of the head drop in the energy-discharge curve through large eddy simulation. The detailed analysis reveals that the head drop at the point 0.85 QBEP is related to the recirculation flow at the runner inlet. Finally, unsteady studies confirm that vortex movement at the runner inlet lead to the variation of the amplitudes and directions of the velocity, which generates the rotation of the separation vortices in the runner and stay vane channels.

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