Large-Eddy Simulation of typical industrial bends In-plane and - - PowerPoint PPT Presentation

03/03/2014 Products Solutions Services

Large-Eddy Simulation of typical industrial bends

In-plane and out-of-plane bend at Re =20’000

by V. Kumar, B. Kissling*, P. Panathansiou and F. Aydin

* Experimental data Slide 1

• V. Kumar

03/03/2014

E+H Flowtec AG

• Endress+Hauser Flowtec is a world leader in industrial flow meters
• Flow meters based on the principles
• Thermal, magnetic-inductive, vortex, ultrasonic and Coriolis
• Production centers in four continents

Large-Eddy Simulation of flows after typical industrial bends Reinach-CH Cernay-Fr Europe Asia North America Asia Greenwood / USA Suzhou / China Aurangabad / India Itatiba / Brazil

• S. America

Slide 2

• V. Kumar

03/03/2014

Product Portfolio

Line sizes from 1 mm to 3000 mm

Large-Eddy Simulation of flows after typical industrial bends

4 Line Display Touch Control 2 Line Display Pushbutton Proso sonic c Flow Promass ss Promag Prowi wirl rl t-mass ss

Slide 3

• V. Kumar

03/03/2014

Where CFD is playing its role?

• Optimizing the design of the flow meters
• Flow meters can resolve effects of the order of 0.05% to 1%
• highly accurate models and high quality grids are required
• To investigate installation effects on the flow meters
• how does the flow develops after a disturbance
• Typical disturbances are bends, diffusors, reducers

Large-Eddy Simulation of flows after typical industrial bends

→ It is very important for a turbulence model to accurately model the effects near the wall

Slide 4

• V. Kumar

03/03/2014

Bend Simulations

Large-Eddy Simulation of flows after typical industrial bends Slide 5

• V. Kumar

03/03/2014

Bend configurations investigated

In-plane or 90° bend Out-of-plane bend

• Fully-developed inlet generated by a periodic pipe simulation
• Approx. 40D downstream length in the simulation
• LES, Realizable k-eps two-layer, RSM two-layer and SST models tested
• Measurements done using clamp-on ultrasonic sensors over the 0 to 360° at

different L/D’s downstream the bends.

Large-Eddy Simulation of flows after typical industrial bends Slide 6

• V. Kumar

03/03/2014

Mesh

For the LES simulation:

• Grid resolution 𝑠+ ≅ 15, 𝑨+≅ 30, 𝜄+ =15; ∆𝑧+< 1, 𝑇𝑠 < 1.2
• Base size => 0.015 D
• ∆𝑧+ is estimated from 𝑆𝑓𝜐 = 0.199 𝑆𝑓7/8
• Approx. 10 Million Cells for both the cases

→Mesh variation and boundary layer variations were also carried

Large-Eddy Simulation of flows after typical industrial bends Slide 7

• V. Kumar

03/03/2014

LES mesh size and effort requirement

• Computational effort goes with 𝑶𝟐.𝟔 or 𝑺𝒇𝟒.𝟘
• 10-20 Million cells grids are computationally affordable for LES

Large-Eddy Simulation of flows after typical industrial bends

Affordable for industry

• ca. 2 days wall time with full

16 nodes, L/D~40

Slide 8

• V. Kumar

03/03/2014

LES Methodology

• Ratio of turbulent length scale and grid-size must be controlled
• A RANS simulation carried out before starting an LES

𝑆𝑀 = ∆ 𝑚𝑢𝑣𝑠𝑐 ≤ 0.5, 𝑚𝑢𝑣𝑠𝑐 = k3/2 ε

• CFL <1 in 96-99% cells
• Second order time- and space (BCD) discretization
• WALE Sub-grid model with wall-limiter and Cw =0.544
• Simulations are carried until the averaged mean flow does not change

anymore

• 100k time-steps with time-integration started after 20k steps.

→Synthetic turbulence at the inlet to avoid laminarization

Large-Eddy Simulation of flows after typical industrial bends Slide 9

• V. Kumar

03/03/2014

In-Plane Bend

Velocity field downstream in-plane bend

• Flow development using RKEPS

slowest among all

• SST shows artifacts close to the bend
• RSM is closest to LES
• Same grid for LES and RANS

Large-Eddy Simulation of flows after typical industrial bends Slide 10

• V. Kumar

03/03/2014

Axial and radial velocity profiles

• All RANS models predict much slower flow development for the in-plane

bend

Large-Eddy Simulation of flows after typical industrial bends Slide 11

• V. Kumar

03/03/2014

Comparison with measurements

• LDA Measurements by Kalpakli and Orlu, Int. J Heat and Fluid Flow 2013

at 0.67D Downstream the 90° bend

• Reasonably well agreement between two independent studies

Large-Eddy Simulation of flows after typical industrial bends Slide 12

• V. Kumar

03/03/2014

Ultrasonic measurements vs Simulations

5D Downstream 30D Downstream

• Deviation from mean flow velocity is plotted
• LES shows a very good agreement throughout
• RSM the best among RANS

Large-Eddy Simulation of flows after typical industrial bends Slide 13

• V. Kumar

03/03/2014

Out of plane bend at Re =20’000

• RSM gives artifacts
• SST results are similar to RSM
• Realizable k-epsilon model seems to be

best performing

• LES predicts different swirl decay than

all RANS models

Large-Eddy Simulation of flows after typical industrial bends Slide 14

• V. Kumar

03/03/2014

Comparison with ultrasonic measurements-I

• At 3D downstream
• RKEPS-2L is underpredicting the flow distortion
• LES is very close to the measurements
• Both RSM and SST shows artificial effects

→ We performed transient RANS as well without much improvement

Large-Eddy Simulation of flows after typical industrial bends Slide 15

• V. Kumar

03/03/2014

Comparison with ultrasonic measurements-II

• At 11 D downstream
• RSM model seems to recover further downstream
• In LES, swirl seems to be much faster, i.e. tangential stresses are under

predicted

→ We tested various mesh sizes and different subgrid models

Large-Eddy Simulation of flows after typical industrial bends Slide 16

• V. Kumar

03/03/2014

Conclusions

In-plane bend:

• Both RSM and LES are well predicting the flow up to 30D downstream
• Realizable K-Epsilon model predicts slower decay of disturbances
• SST significantly worse than others

Out-of-plane bend:

• RANS are better predicting the rotational decay
• Close to the bend, both RSM and SST are not performing well
• LES is predicting very well close to the bend
• However further downstream, swirl decay much slower than as predicted by RANS

and in experiments

• LES models and grid-resolution to be thoroughly investigated for swirling flows

Large-Eddy Simulation of flows after typical industrial bends Slide 17

• V. Kumar

03/03/2014

Thank you

Large-Eddy Simulation of flows after typical industrial bends

Vortictiy field in 90° bend

Slide 18

• V. Kumar