NUMERICAL ANALYSIS OF AN AXIAL BLOOD PUMP WITH DIFFERENT IMPELLER BLADE HEIGHTS

2012 ◽  
Vol 12 (03) ◽  
pp. 1250045 ◽  
Author(s):  
JIAXING QI ◽  
YANHONG ZHOU ◽  
DONGFANG WANG ◽  
LIANG ZHONG
Keyword(s):  
Shear Stress ◽  
Flow Rate ◽  
Reverse Flow ◽  
Blood Pump ◽  
Shear Stresses ◽  
Cfd Simulations ◽  
Impeller Blade ◽  
Rotating Speed ◽  
Shear Stress Level ◽  
Computational Fluid Dynamics Cfd

Computational fluid dynamics (CFD) simulations of the flow in an axial blood pump with different blade heights (BH150, BH200 and BH250) were performed in the present study. The flow in the pump was assumed as steady and turbulent, and blood was treated as incompressible and Newtonian fluid. The flow rate increased with the rise in blade heights. At the impeller rotating speed of 20,000 rpm and a pressure of 100 mm Hg, the pump produces a flow rate up to 5 L/min in BH200 and BH250 models. The reverse flow and vortices have been identified in the BH150 and BH200 models in the outlet regions, but not for BH250 model. The high shear stress of the flow in the pump mainly occurred at the blade tips. The BH200 model achieved an expected flow rate up to 5 L/min with 90% of the shear stresses less than 500 Pa and the exposure time less than 22 ms, which has the acceptable shear stress level in the literature.

scholarly journals Assessing Bioinspired Topographies for their Antifouling Potential Control Using Computational Fluid Dynamics (CFD)

2018 ◽  
Vol 152 ◽  
pp. 02004 ◽  
Author(s):  
Jacky Ling ◽  
Felicia Wong Yen Myan
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Extended Period ◽  
Slip Boundary Condition ◽  
Shear Stresses ◽  
Cfd Simulations ◽  
Potential Control ◽  
Slip Boundary ◽  
Computational Fluid Dynamics Cfd ◽  
Wall Shear

Biofouling is the accumulation of unwanted material on surfaces submerged or semi submerged over an extended period. This study investigates the antifouling performance of a new bioinspired topography design. A shark riblets inspired topography was designed with Solidworks and CFD simulations were antifouling performance. The study focuses on the fluid flow velocity, the wall shear stress and the appearance of vortices are to be noted to determine the possible locations biofouling would most probably occur. The inlet mass flow rate is 0.01 kgs-1 and a no-slip boundary condition was applied to the walls of the fluid domain. Simulations indicate that Velocity around the topography averaged at 7.213 x 10-3 ms-1. However, vortices were observed between the gaps. High wall shear stress is observed at the peak of each topography. In contrast, wall shear stress is significantly low at the bed of the topography. This suggests the potential location for the accumulation of biofouling. Results show that bioinspired antifouling topography can be improved by reducing the frequency of gaps between features. Linear surfaces on the topography should also be minimized. This increases the avenues of flow for the fluid, thus potentially increasing shear stresses with surrounding fluid leading to better antifouling performance.

scholarly journals Investigations of Inducers Operating With High Rotational Speed

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Björn Gwiasda ◽  
Matthias Mohr ◽  
Martin Böhle
Keyword(s):  
Rotational Speed ◽  
Test Bench ◽  
Pressure Rise ◽  
Working Fluid ◽  
Cfd Simulations ◽  
High Rotational Speed ◽  
Rotating Speed ◽  
Performance Pressure ◽  
Computational Fluid Dynamics Cfd ◽  
Suction Performance

Suction performance, pressure rise, and efficiency for four different inducers are examined with computational fluid dynamics (CFD) simulations and experiments performed with 18,000 rpm and 24,000 rpm. The studies originate from a research project that includes the construction of a new test bench in order to judge the design of the different inducers. This test bench allows to conduct experiments with a rotational speed of up to 40,000 rpm and high pressure ranges from 0.1 bar to 40 bar with water as working fluid. Experimental results are used to evaluate the accuracy of the simulations and to gain a better understanding of the design parameter. The influence of increasing the rotating speed from 18,000 rpm to 24,000 rpm on the performance is also shown.

scholarly journals Effect of hydraulic and geometric factors upon leakage flow rate in pressurized pipes

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Mayara Francisca da Silva ◽  
Fábio Veríssimo Gonçalves ◽  
Johannes Gérson Janzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Leakage Flow ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Leakage Flow Rate ◽  
Geometric Factors ◽  
Leakage Area ◽  
Computational Fluid Dynamics Cfd

ABSTRACT Computational Fluid Dynamics (CFD) simulations of a leakage in a pressurized pipe were undertaken to determine the empirical effects of hydraulic and geometric factors on the leakage flow rate. The results showed that pressure, leakage area and leakage form, influenced the leakage flow rate significantly, while pipe thickness and mean velocity did not influence the leakage flow rate. With relation to the interactions, the effect of pressure upon leakage flow rate depends on leakage area, being stronger for great leakage areas; the effects of leakage area and pressure on leakage flow rate is more pronounced for longitudinal leakages than for circular leakages. Finally, our results suggest that the equations that predict leakage flow rate in pressurized pipes may need a revision.

THE EFFECTS OF EXTENSIONAL STRESS ON RED BLOOD CELL HEMOLYSIS

2015 ◽  
Vol 27 (05) ◽  
pp. 1550042 ◽  
Author(s):  
Jen-Hong Yen ◽  
Sheng-Fu Chen ◽  
Ming-Kai Chern ◽  
Po-Chien Lu
Keyword(s):  
Shear Stress ◽  
Blood Cell ◽  
Prediction Models ◽  
Cell Damage ◽  
Threshold Value ◽  
Shear Stresses ◽  
Flow Conditions ◽  
Extensional Stress ◽  
Computational Fluid Dynamics Cfd ◽  
Stress Flow

Artificial prostheses create non-physiologic flow conditions with stress forces that may induce blood cell damage, particularly hemolysis. Earlier computational fluid dynamics (CFD) prediction models based on a quantified power model showed significant discrepancies with actual hemolysis experiments. These models used the premise that shear stresses act as the primary force behind hemolysis. However, additional studies have suggested that extensional stresses play a more substantial role than previously thought and should be taken into account in hemolysis models. We compared extensional and shear stress flow fields within the contraction of a short capillary with sharp versus tapered entrances. The flow field was calculated with CFD to determine stress values, and hemolysis experiments with porcine red blood cells were performed to correlate the effects of extensional and shear stress on hemolysis. Our results support extensional stress as the primary mechanical force involved in hemolysis, with a threshold value of 1000 Pa under exposure time less than 0.060 ms.

CFD Simulations and PIV Measurements for Optimization of Flow Pattern in a Sieve Plate Extraction Column

2011 ◽  
Vol 391-392 ◽  
pp. 1464-1468
Author(s):  
Chang Chun Duan ◽  
Chun Jiang Liu ◽  
Xi Gang Yuan
Keyword(s):  
Flow Pattern ◽  
Reverse Flow ◽  
Continuous Phase ◽  
Extraction Column ◽  
Sieve Plate ◽  
Cfd Simulations ◽  
Flow Area ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Cfd

Present work deals with the optimization for flow pattern of continuous phase in a sieve plate extraction column using both computational fluid dynamics (CFD) simulations and particle image velocimetry (PIV) measurements. Firstly single-phase simulation was conducted for the traditional column and it was found that there was a very large reverse flow area between every two plates. Then step by step, by changing the downcomer structure, consisting of inclining downcomers, adding baffles, slotting downcomers and baffles and adjusting the number and size of slots, the reverse flow area was decreased and thereby the flow pattern of continuous phase was optimized. Finally, an optimal flow pattern was obtained with reverse flow area greatly reduced. In order to prove the validity of the simulation results, PIV experiments of two columns were carried out and it was found that the results of simulations and experiments are in good agreement.

NUMERICAL INVESTIGATIONS OF A CENTRIFUGAL BLOOD PUMP

2004 ◽  
Vol 04 (03) ◽  
pp. 237-255 ◽  
Author(s):  
W. K. CHAN ◽  
Y. W. WONG ◽  
Y. DING
Keyword(s):  
Leading Edge ◽  
Suction Side ◽  
Small Region ◽  
Inverse Design ◽  
Blood Pump ◽  
Impeller Blade ◽  
Centrifugal Blood Pump ◽  
Computational Fluid Dynamics Cfd ◽  
Inlet Angle ◽  
Side Flow

This paper presents computational fluid dynamics (CFD) studies of a centrifugal blood pump. 3-D models of five different blade geometries are investigated numerically using CFX-TASCflow. The impellers were designed using an inverse design technique where the swirl distributions were prescribed. The results showed the flow in the impeller passages is highly dependent on the impeller blade profiles. The flow in the radial blade impeller is unsatisfactory as flow separates at the leading edge of the suction side. Flow is confined mainly to the pressure side. Design 2, with an inlet angle of 6.7° and outlet angle of 30°, offers the greatest potential as only a small region of flow reversal is detected. Further optimization is necessary to completely eliminate regions of flow reversals. The highest scalar shear stress in both designs is 240 Pa and 120 Pa respectively. In addition, this paper demonstrates that the use of inverse design can help the designer to better design and analyze the flow field in centrifugal blood pumps.

Grid-Induced Numerical Errors for Shear Stresses and Essential Flow Variables in a Ventricular Assist Device: Crucial for Blood Damage Prediction?

2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Lucas Konnigk ◽  
Benjamin Torner ◽  
Sebastian Hallier ◽  
Matthias Witte ◽  
Frank-Hendrik Wurm
Keyword(s):  
Shear Stress ◽  
Prediction Models ◽  
Stokes Equations ◽  
Grid Size ◽  
Blood Pump ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Damage Prediction ◽  
Blood Damage ◽  
Stress Calculation

Adverse events due to flow-induced blood damage remain a serious problem for blood pumps as cardiac support systems. The numerical prediction of blood damage via computational fluid dynamics (CFD) is a helpful tool for the design and optimization of reliable pumps. Blood damage prediction models primarily are based on the acting shear stresses, which are calculated by solving the Navier–Stokes equations on computational grids. The purpose of this paper is to analyze the influence of the spatial discretization and the associated discretization error on the shear stress calculation in a blood pump in comparison to other important flow quantities like the pressure head of the pump. Therefore, CFD analysis using seven unsteady Reynolds-averaged Navier–Stokes (URANS) simulations was performed. Two simple stress calculation indicators were applied to estimate the influence of the discretization on the results using an approach to calculate numerical uncertainties, which indicates discretization errors. For the finest grid with 19 × 106 elements, numerical uncertainties up to 20% for shear stresses were determined, while the pressure heads show smaller uncertainties with a maximum of 4.8%. No grid-independent solution for velocity gradient-dependent variables could be obtained on a grid size that is comparable to mesh sizes in state-of-the-art blood pump studies. It can be concluded that the grid size has a major influence on the shear stress calculation, and therefore, the potential blood damage prediction, and that the quantification of this error should always be taken into account.

NEW TRENDS IN TISSUE ENGINEERED CARTILAGE: MICROFLUID DYNAMICS IN 3-D ENGINEERED CELL SYSTEMS

2005 ◽  
Vol 05 (03) ◽  
pp. 455-464
Author(s):  
FEDERICA BOSCHETTI ◽  
MARGHERITA CIOFFI ◽  
MANUELA TERESA RAIMONDI ◽  
FRANCESCO MIGLIAVACCA ◽  
GABRIELE DUBINI
Keyword(s):  
Shear Stress ◽  
Flow Rate ◽  
Culture Medium ◽  
Porous Scaffold ◽  
Fluid Dynamic ◽  
Tissue Growth ◽  
Shear Stresses ◽  
Mechanical Stimuli ◽  
Micro Computed Tomography ◽  
Medium Flow

Bioreactors allowing culture medium direct-perfusion overcome diffusion limitations associated with static culturing and provide flow-mediated mechanical stimuli. The hydrodynamic stress imposed on chondrocytes will depend not only on the culture medium flow rate, but also on the scaffold three-dimensional (3D) micro-architecture. We performed computational fluid-dynamic (CFD) simulations of the flow of culture medium through a 3D porous scaffold, with the aim of predicting the shear stress acting on the cells as a function of parameters that can be set in a tissue-engineering experiment, such as the medium flow rate and the diameter of the perfused scaffold section. We developed two CFD models: the first model (Model 1) was built from micro-computed tomography reconstruction of the actual scaffold geometry, while the second model (Model 2) was based on a simplification of the actual scaffold microstructure. The two models showed comparable results in terms of the distribution of the shear stresses acting on the inner surfaces of the scaffold walls. Models 1 and 2 gave a median shear stress of 3 mPa at a flow rate of 0.5 cm3 min-1 through a 15 mm diameter scaffold. Our results provide a basis for the completion of more exhaustive quantitative studies to further assess the relationship between perfusion at known micro-fluid dynamic conditions and tissue growth in vitro.

CFD Analysis of Ventilation Flow for a Scale Model Hydro-Generator

2011 ◽  
Author(s):  
Kristopher Toussaint ◽  
Federico Torriano ◽  
Jean-Franc¸ois Morissette ◽  
Claude Hudon ◽  
Marcelo Reggio
Keyword(s):  
Flow Rate ◽  
Scale Model ◽  
Interface Model ◽  
Cfd Simulations ◽  
Image Velocimetry ◽  
Highly Sensitive ◽  
Sensitivity Studies ◽  
Transient Case ◽  
Computational Fluid Dynamics Cfd ◽  
2D And 3D

In 2006, the first Computational Fluid Dynamics (CFD) simulations of the ventilation of specific hydro-generator components were performed at the Hydro-Que´bec Research Institute (IREQ) and lately the entire ventilation circuit is being investigated. Due to the complexity of flow calculations, a validation process is necessary and for this reason a 1:4 scale model of a hydro-generator has been built at IREQ to get experimental data by means of particle image velocimetry (PIV). This paper presents 2D and 3D simulation results for the scale model obtained with a commercial CFD code and addresses the challenges associated with the application of CFD to hydro-generators. In particular, the effect of rotor-stator interface (RSI) types and configuration is analyzed to determine the approach that best suits this application. Two-dimensional calculations show that the steady state multiple frames of reference (MFR) solution is highly sensitive to the type (frozen rotor (FR) vs. mixing plane (MP)) and location of the RSI. A parametric study is performed where each interface configuration is compared to the transient case results. The MFR-FR interface model produces results that may vary significantly depending on the relative rotor position and the radial location of the RSI in the air gap. The MFR-MP interface model appears to be more coherent with reference values obtained from a transient case, since the radial velocity profiles in the stator are similar. Furthermore with an appropriate radial positioning of the interface, the windage losses are within 20%. Simulations of the complete 3D ventilation circuit revealed a maximum variation of 10% in both total ventilation flow rate and total windage losses, between the RSI configurations studied. However, the relative flow distributions, normalized with respect to the total flow rate, are unaffected by changes in RSI configuration. This paper focuses mainly on sensitivity studies to numerical settings, but this comparison still requires experimental validation before any final conclusions can be made.

Design and Numerical Evaluation of an Axial Partial-assist Blood Pump for Chinese and other Heart Failure Patients

2017 ◽  
Vol 40 (9) ◽  
pp. 489-497 ◽  
Author(s):  
Guang-Mao Liu ◽  
Dong-Hai Jin ◽  
Jian-Ye Zhou ◽  
Xi-Hang Jiang ◽  
Han-Song Sun ◽  
...  
Keyword(s):  
Heart Failure ◽  
Shear Stress ◽  
Flow Rate ◽  
Tangential Velocity ◽  
Pressure Head ◽  
Left Ventricular ◽  
Blood Pump ◽  
Partial Support ◽  
Heart Failure Patients ◽  
Cantilever Structure

A fully implantable axial left ventricular assist device LAP31 was developed for Chinese or other heart failure patients who need partial support. Based on the 5-Lpm total cardiac blood output of Chinese without heart failure disease, the design point of LAP31 was set to a flow rate of 3 Lpm with 100-mmHg pressure head. To achieve the required pressure head and good hemolytic performance, a structure that includes a spindly rotor hub and a diffuser with splitter and cantilevered main blades was developed. Computational fluid dynamics (CFD) was used to analyze the hydraulic and hemodynamic performance of LAP31. Then in vitro hydraulics experiments were conducted. The numerical simulation results show that LAP31 could generate a 1 to 8 Lpm flow rate with a 60.9 to 182.7 mmHg pressure head when the pump was rotating between 9,000 and 12,000 rpm. The average scalar shear stress of the blood pump was 21.7 Pa, and the average exposure time was 71.0 milliseconds. The mean hemolysis index of LAP31 obtained using Heuser's hemolysis model and Giersiepen's model was 0.220% and 3.89 × 105% respectively. After adding the splitter blades, the flow separation at the suction surface of the diffuser was reduced. The cantilever structure reduced the tangential velocity from 6.1 to 4.7–1.4 m/s within the blade gap by changing the blade gap from shroud to hub. Subsequently, the blood damage caused by shear stress was reduced. In conclusion, the hydraulic and hemolytic characteristics of the LAP31 are acceptable for partial support.

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