Large eddy simulation in a rotary blood pump: Viscous shear stress computation and comparison with unsteady Reynolds-averaged Navier–Stokes simulation

2018 ◽  
Vol 41 (11) ◽  
pp. 752-763 ◽  
Author(s):  
Benjamin Torner ◽  
Lucas Konnigk ◽  
Sebastian Hallier ◽  
Jitendra Kumar ◽  
Matthias Witte ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Blood Pump ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Element Mesh ◽  
Damage Prediction ◽  
Eddy Simulation ◽  
Viscous Shear ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Purpose: Numerical flow analysis (computational fluid dynamics) in combination with the prediction of blood damage is an important procedure to investigate the hemocompatibility of a blood pump, since blood trauma due to shear stresses remains a problem in these devices. Today, the numerical damage prediction is conducted using unsteady Reynolds-averaged Navier–Stokes simulations. Investigations with large eddy simulations are rarely being performed for blood pumps. Hence, the aim of the study is to examine the viscous shear stresses of a large eddy simulation in a blood pump and compare the results with an unsteady Reynolds-averaged Navier–Stokes simulation. Methods: The simulations were carried out at two operation points of a blood pump. The flow was simulated on a 100M element mesh for the large eddy simulation and a 20M element mesh for the unsteady Reynolds-averaged Navier-Stokes simulation. As a first step, the large eddy simulation was verified by analyzing internal dissipative losses within the pump. Then, the pump characteristics and mean and turbulent viscous shear stresses were compared between the two simulation methods. Results: The verification showed that the large eddy simulation is able to reproduce the significant portion of dissipative losses, which is a global indication that the equivalent viscous shear stresses are adequately resolved. The comparison with the unsteady Reynolds-averaged Navier–Stokes simulation revealed that the hydraulic parameters were in agreement, but differences for the shear stresses were found. Conclusion: The results show the potential of the large eddy simulation as a high-quality comparative case to check the suitability of a chosen Reynolds-averaged Navier–Stokes setup and turbulence model. Furthermore, the results lead to suggest that large eddy simulations are superior to unsteady Reynolds-averaged Navier–Stokes simulations when instantaneous stresses are applied for the blood damage prediction.

Hybrid Large Eddy Simulation/Reynolds-Averaged Navier–Stokes Analysis of a Premixed Ethylene-Fueled Dual-Mode Scramjet Combustor

AIAA Journal ◽  
2021 ◽  
pp. 1-17
Author(s):  
Tanner B. Nielsen ◽  
Jack R. Edwards ◽  
Harsha K. Chelliah ◽  
Damien Lieber ◽  
Clayton Geipel ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Navier Stokes ◽  
Dual Mode ◽  
Eddy Simulation ◽  
Scramjet Combustor ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

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.

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