scholarly journals Correlation of LVAD Outflow Graft Orientation with Aortic Root Thrombosis Rationalized by Patient Specific Computational Fluid Dynamics Simulations

2016 ◽  
Vol 35 (4) ◽  
pp. S246 ◽  
Author(s):  
M. Kassi ◽  
C. Karmonik ◽  
J. Engelke ◽  
C. Eshelbrenner ◽  
H. Rehman ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Aortic Root ◽  
Patient Specific ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Outflow Graft

Computational Fluid Dynamics Study of Cerebral Thromboembolism Risk in Ventricular Assist Device Patients: Effects of Pulsatility and Thrombus Origin

2021 ◽  
Author(s):  
Ray Prather ◽  
Eduardo Divo ◽  
Alain J. Kassab ◽  
William DeCampli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Unsteady Flow ◽  
Aortic Root ◽  
Flow Analysis ◽  
Patient Specific ◽  
Assist Device ◽  
Device Placement ◽  
Cardiovascular Simulation ◽  
Outflow Graft

Abstract Purpose: This study investigates the hypothesis that by surgically manipulating the outflow graft implantation during ventricle assist device placement, it may be possible to reduce the risk of cerebral embolism. Methods: We investigate this hypothesis using a computational approach on a patient specific basis under fully-pulsatile hemodynamics with a multi-scale computational fluid dynamics model incorporating a coupled Eulerian-Lagrangian scheme that effectively tracks emboli in the fluid domain. Blood is modeled as a non-Newtonian fluid based on the hematocrit level. Results: Preliminary flow analysis shows that, depending on the anastomosis angle the LVAD can enhance the flow to the cerebral circulation by nearly 31%. Z-test results suggest that unsteady flow modelling ought to be an integral part of any cardiovascular simulation with residual ventricular function. Assuming unsteady flow conditions, a shallow LVAD outflow graft anastomosis angle is the most optimal if thrombi are released from the aortic root reducing cerebral embolization incidence to 15.5% and from the ventricle to 17%, while a more pronounced anastomosis angle becomes advantageous when particles originate from the LVAD with an embolization rate of 16.9%. Conclusion: Overall, computations suggest that a pronounced LVAD anastomosis angle is the better implementation. Unsteady modeling is shown to be necessary in the presence of significant antegrade aortic root flow which induces cyclical flow patterns due to residual pulsatility. On the other hand depending on thrombus origin and VAD anastomosis angle there is a strong tradeoff in embolization rates.

scholarly journals Aerodynamic analysis of uphill drafting in cycling

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
T. van Druenen ◽  
B. Blocken
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Scientific Literature ◽  
Sensitivity Analyses ◽  
Air Resistance ◽  
Wind Tunnel Measurements ◽  
Aerodynamic Effect ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

AbstractSome teams aiming for victory in a mountain stage in cycling take control in the uphill sections of the stage. While drafting, the team imposes a high speed at the front of the peloton defending their team leader from opponent’s attacks. Drafting is a well-known strategy on flat or descending sections and has been studied before in this context. However, there are no systematic and extensive studies in the scientific literature on the aerodynamic effect of uphill drafting. Some studies even suggested that for gradients above 7.2% the speeds drop to 17 km/h and the air resistance can be neglected. In this paper, uphill drafting is analyzed and quantified by means of drag reductions and power reductions obtained by computational fluid dynamics simulations validated with wind tunnel measurements. It is shown that even for gradients above 7.2%, drafting can yield substantial benefits. Drafting allows cyclists to save over 7% of power on a slope of 7.5% at a speed of 6 m/s. At a speed of 8 m/s, this reduction can exceed 16%. Sensitivity analyses indicate that significant power savings can be achieved, also with varying bicycle, cyclist, road and environmental characteristics.

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