scholarly journals Design and execution of a Verification, Validation, and Uncertainty Quantification plan for a numerical model of left ventricular flow after LVAD implantation

2021 ◽  
Author(s):  
Alfonso Santiago ◽  
Constantine Butakoff ◽  
Beatriz Eguzkitza ◽  
Richard A Gray ◽  
Karen May-Newman ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Model ◽  
Uncertainty Quantification ◽  
Aortic Root ◽  
Solution Procedure ◽  
Left Ventricular ◽  
Operating Conditions ◽  
Numerical Code ◽  
Performance Curve ◽  
The Impact

Background: left ventricular assist devices (LVADs) are implantable pumps that act as a life support therapy for patients with severe heart failure. Despite improving the survival rate, LVAD therapy can carry major complications. Particularly, the flow distortion introduced by the LVAD in the left ventricle (LV) may induce thrombus formation. While previous works have used numerical models to study the impact of multiple variables in the intra-LV stagnation regions, a comprehensive validation analysis has never been executed. The main goal of this work is to present a model of the LV-LVAD system and to design and follow a verification, validation and uncertainty quantification (VVUQ) plan based on the ASME V&V40 and V&V20 standards to ensure credible predictions. Methods: The experiment used to validate the simulation is the SDSU cardiac simulator, a bench mock-up of the cardiovascular system that allows mimicking multiple operation conditions for the heart-LVAD system. The numerical model is based on Alya, the BSC's in-house platform for numerical modelling. Alya solves the Navier-Stokes equation with an Arbitrarian Lagrangian-Eulerian (ALE) formulation in a deformable ventricle and includes pressure-driven valves, a 0D Windkessel model for the arterial output and a LVAD boundary condition modeled through a dynamic pressure-flow performance curve. The designed VVUQ plan involves: (a) a risk analysis and the associated credibility goals; (b) a verification stage to ensure correctness in the numerical solution procedure; (c) a sensitivity analysis to quantify the impact of the inputs on the four quantities of interest (QoIs) (average aortic root flow, maximum aortic root flow, average LVAD flow, and maximum LVAD flow); (d) an uncertainty quantification using six validation experiments that include extreme operating conditions. Results: Numerical code verification tests ensured correctness of the solution procedure and numerical calculation verification showed small numerical errors. The total Sobol indices obtained during the sensitivity analysis demonstrated that the ejection fraction, the heart rate, and the pump performance curve coefficients are the most impactful inputs for the analysed QoIs. The Minkowski norm is used as validation metric for the uncertainty quantification. It shows that the midpoint cases have more accurate results when compared to the extreme cases. The total computational cost of the simulations was above 100 [core-years] executed in around three weeks time span in Marenostrum IV supercomputer. Conclusions: This work details a novel numerical model for the LV-LVAD system, that is supported by the design and execution of a VVUQ plan created following recognised international standards. We present a methodology demonstrating that stringent VVUQ according to ASME standards is feasible but computationally expensive.

scholarly journals A Validation/Uncertainty Quantification Analysis for a 1.5 MW Oxy-Coal Fired Furnace: Sensitivity Analysis

2018 ◽  
Vol 3 (1) ◽  
Author(s):  
Oscar H. Díaz-Ibarra ◽  
Jennifer Spinti ◽  
Andrew Fry ◽  
Benjamin Isaac ◽  
Jeremy N. Thornock ◽  
...  
Keyword(s):  
Heat Flux ◽  
Sensitivity Analysis ◽  
Uncertainty Quantification ◽  
Complex Geometry ◽  
Heat Removal ◽  
Operating Conditions ◽  
Model Parameters ◽  
Reacting Flow ◽  
Simulation Data ◽  
The Impact

A validation/uncertainty quantification (VUQ) study was performed on the 1.5 MWth L1500 furnace, an oxy-coal fired facility located at the Industrial Combustion and Gasification Research Facility at the University of Utah. A six-step VUQ framework is used for studying the impact of model parameter uncertainty on heat flux, the quantity of interest (QOI) for the project. This paper focuses on the first two steps of the framework. The first step is the selection of model outputs in the experimental and simulation data that are related to the heat flux: incident heat flux, heat removal by cooling tubes, and wall temperatures. We describe the experimental facility, the operating conditions, and the data collection process. To obtain the simulation data, we utilized two tools, star-ccm+ and Arches. The star-ccm+ simulations captured flow through the complex geometry of the swirl burner while the Arches simulations captured multiphase reacting flow in the L1500. We employed a filtered handoff plane to couple the two simulations. In step two, we developed an input/uncertainty (I/U) map and assigned a priority to 11 model parameters based on prior knowledge. We included parameters from both a char oxidation model and an ash deposition model in this study. We reduced the active parameter space from 11 to 5 based on priority. To further reduce the number of parameters that must be considered in the remaining steps of the framework, we performed a sensitivity analysis on the five parameters and used the results to reduce the parameter set to two.

scholarly journals A Model for the Thermal Behaviour of an Offshore Cable Installed in a J-Tube

Proceedings ◽  
2020 ◽  
Vol 58 (1) ◽  
pp. 31
Author(s):  
Jeremy Arancio ◽  
Ahmed Ould El Moctar ◽  
Minh Nguyen Tuan ◽  
Faradj Tayat ◽  
Jean-Philippe Roques
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Model ◽  
Thermal Behaviour ◽  
Energy Production ◽  
Power Transmission ◽  
Temperature Fields ◽  
Sobol Indices ◽  
Lumped Element ◽  
Thermal Phenomena ◽  
The Impact

In the race for energy production, supplier companies are concerned by the thermal rating of offshore cables installed in a J-tube, not covered by IEC 60287 standards, and are now looking for solutions to optimize this type of system. This paper presents a numerical model capable of calculating temperature fields of a power transmission cable installed in a J-tube, based on the lumped element method. This model is validated against the existing literature. A sensitivity analysis performed using Sobol indices is then presented in order to understand the impact of the different parameters involved in the heating of the cable. This analysis provides an understanding of the thermal phenomena in the J-tube and paves the way for potential technical and economic solutions to increase the ampacity of offshore cables installed in a J-tube.

Uncertainty Quantification of NOx Emission Due to Operating Conditions and Chemical Kinetic Parameters in a Premixed Burner

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Sajjad Yousefian ◽  
Gilles Bourque ◽  
Rory F. D. Monaghan
Keyword(s):  
Sensitivity Analysis ◽  
Uncertainty Quantification ◽  
Gas Turbine ◽  
Flow Reactor ◽  
Epistemic Uncertainty ◽  
Plug Flow ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Nox Emission ◽  
Gas Turbine Combustion

Many sources of uncertainty exist when emissions are modeled for a gas turbine combustion system. They originate from uncertain inputs, boundary conditions, calibration, or lack of sufficient fidelity in a model. In this paper, a nonintrusive polynomial chaos expansion (NIPCE) method is coupled with a chemical reactor network (CRN) model using Python to quantify uncertainties of NOx emission in a premixed burner. The first objective of uncertainty quantification (UQ) in this study is development of a global sensitivity analysis method based on the NIPCE method to capture aleatory uncertainty on NOx emission due to variation of operating conditions. The second objective is uncertainty analysis (UA) of NOx emission due to uncertain Arrhenius parameters in a chemical kinetic mechanism to study epistemic uncertainty in emission modeling. A two-reactor CRN consisting of a perfectly stirred reactor (PSR) and a plug flow reactor (PFR) is constructed in this study using Cantera to model NOx emission in a benchmark premixed burner under gas turbine operating conditions. The results of uncertainty and sensitivity analysis (SA) using NIPCE based on point collocation method (PCM) are then compared with the results of advanced Monte Carlo simulation (MCS). A set of surrogate models is also developed based on the NIPCE approach and compared with the forward model in Cantera to predict NOx emissions. The results show the capability of NIPCE approach for UQ using a limited number of evaluations to develop a UQ-enabled emission prediction tool for gas turbine combustion systems.

Uncertainty quantification of the effects of squealer tip geometry deviation on aerothermal performance

2020 ◽  
Vol 234 (7) ◽  
pp. 1026-1038
Author(s):  
Wei Shi ◽  
Pingting Chen ◽  
Xueying Li ◽  
Ren Jing ◽  
Hongde Jiang
Keyword(s):  
Sensitivity Analysis ◽  
Uncertainty Quantification ◽  
Optimization Design ◽  
Aerodynamic Performance ◽  
Parameter Sensitivity ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Parameter Sensitivity Analysis ◽  
Geometry Deviation

The first-stage rotor squealer tip is a key area in gas turbine for both aerodynamic performance and blade cooling tasks, which should be carefully designed. However, harsh operating conditions near the rotor squealer tip can cause the geometry of the squealer tip to degrade, and manufacturing inaccuracies can also cause the squealer tip geometry to deviate from the ideal design. These geometry deviations would change the flow field near the blade tip, which will influence the thermal and aerodynamic performance. Thus, it is important to quantitatively investigate the effects of squealer tip geometry deviation on the aerothermal performance. In this paper, a typical transonic first-stage turbine is employed, and three important geometric features of squealer tip, the tip clearance height (H), the squealer depth (D), and the squealer edge chamfer (R), are selected. An uncertainty quantification process is performed to study the effect of deviation of H, D, and R on the aerothermal performance. Many cases with different geometry features are checked in the current study using 3D Reynolds-averaged Navier–Stokes simulations. A parameter sensitivity analysis using Sobol Indice method is carried out to identify the key parameters to aerothermal performance of the squealer tip. The uncertainty quantification results show that the existence of the tip chamfer reduces the size of separation bubble and the dwelling range of the scraping vortex, thus, the blockage effect of the leakage flow is weakened, which results in larger amount of leakage flow and more mixing loss of squealer tips with edge chamfer than those without edge chamfer. The results of the parameter sensitivity analysis show that the height of tip clearance is the main factor that affects the aerodynamic performance of the squealer tip. This work provides a certain guiding direction for the optimization design of the turbine groove tip.

Abstract 17361: Phenotype of the Aortic Valve in Patients With Filamin-A Mutations: Echocardiographic Features and Clinical Outcomes

Circulation ◽  
2018 ◽  
Vol 138 (Suppl_1) ◽  
Author(s):  
Romain Capoulade ◽  
Caroline Cueff ◽  
Nicolas Piriou ◽  
Claire Toquet ◽  
Stéphanie Blandin ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Aortic Valve ◽  
Clinical Outcomes ◽  
Aortic Root ◽  
Ventricular Outflow Tract ◽  
Underlying Disease ◽  
Left Ventricular ◽  
Filamin A ◽  
Sinotubular Junction ◽  
The Impact

Background: Filamin-A ( FLNA ) mutations have been associated with the development of mitral valve prolapse and a unique mitral valve features described as a paradoxical restrictive leaflets motion in diastole has been recently described using a comprehensive echocardiographic screening. Polyvalvular diseases have also been reported in these patients, especially affecting the aortic valve. Objectifs: The objective of this study was to perform a comprehensive echocardiographic analysis of the aortic valve (AV) and the proximal aortic root of patients with FLNA mutations, and assess the impact of the aortic disease on outcomes. Methods: We included in this analysis 256 subjects (42±22 years, 136 men, 76 mutated: FLNA+) with confirmed genetic status, from 5 FLNA families. Comprehensive echocardiographic characterization of the aortic valve and the proximal aortic root, including the measurement of the aortic annulus, sinuses of Valsalva, sinotubular junction and ascending aorta, was performed in FLNA+ patients vs control relatives. Results: Overall, 47 subjects (18%) presented an aortic valve alteration: 40 (53%) of FLNA+ compared to 7 (4%) FLNA- subjects (p<0.001). Among the 76 FLNA+ patients, 7 (9%) had a bicuspid aortic valve phenotype as opposed to 2 (1%) in control relatives (p=0.02). The underlying disease affecting the aortic valve was AV sclerosis, stenosis and AV regurgitation with either prolapse or restricted cusps motion. A restrictive opening of the AV was also reported in some patients. Aortic valve mean gradient was slightly increased in FLNA+ compared with FLNA- subjects (5.7±5.1 vs 4.2±1.8 mmHg, P= 0.02). In adults, left ventricular outflow tract diameter (12.5±1.4 vs 12.0±1.0 mm/m 2 ; p=0.02), sinuses of Valsalva (17.8±2.5 vs 16.2±1.9 mm/m 2 ; p<0.001) and sinotubular junction (15.0±2.0 vs 13.7±1.6 mm/m 2 ; p<0.001) were larger in FLNA+ subjects as compared to control relatives. 8 FLNA+ subjects (11%; 6 males) underwent aortic valve-related surgery versus 0 in controls (p<0.001). Survival was also impaired in FLNA+ male subjects (70 year old: 72% vs 64%, p=0.03). Conclusion: The FLNA -mutated patients presented aortic valve disease more frequently, including a higher prevalence of bicuspid valve, stenosis, and regurgitation owing to either cusp prolapsed or restrictive motion. This unique features described in this population was associated with worse clinical outcomes, especially in FLNA+ males. Management and decision making should be done according to the features of these patients with polyvalvular diseases

scholarly journals Assessment of Sensitivity to Evaluate the Impact of Operating Parameters on Stability and Performance in Proton Exchange Membrane Fuel Cells

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4069
Author(s):  
Mingzhang Pan ◽  
Chengjie Pan ◽  
Jinyang Liao ◽  
Chao Li ◽  
Rong Huang ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Fuel Cell ◽  
Performance Optimization ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Output Performance ◽  
Highly Nonlinear ◽  
Exchange Membrane ◽  
The Impact

As a highly nonlinear system, the performance of proton exchange membrane fuel cell (PEMFC) is controlled by various parameters. If the effects of all parameters are considered during the performance optimization, low working efficiency and waste of resources will be caused. The development of sensitivity analysis for parameters can not only exclude the parameters which have slight effects on the system, but also provide the reasonable setting ranges of boundary values for simulation of performance optimization. Therefore, sensitivity analysis of parameters is considered as one of the methods to optimize the fuel cell performance. According to the actual operating conditions of PEMFC, the fluctuation ranges of seven sets of parameters affecting the output performance of PEMFC are determined, namely cell operating temperature, anode/cathode temperature, anode/cathode pressure, and anode/cathode mass flow rate. Then, the control variable method is used to qualitatively analyze the sensitivity of main parameters and combines with the Monte Carlo method to obtain the sensitivity indexes of the insensitive parameters under the specified current density. The results indicate that among these parameters, the working temperature of the fuel cell is the most sensitive to the output performance under all working conditions, whereas the inlet temperature is the least sensitive within the range of deviation. Moreover, the cloud maps of water content distribution under the fluctuation of three more sensitive parameters are compared; the results verify the simulated data and further reveal the reasons for performance changes. The workload of PEMFC performance optimization will be reduced based on the obtained results.

Sensitivity Study on the Impact of Surface Roughness Due to Milling on the Efficiency of Shrouded Centrifugal Compressor Impellers

2006 ◽  
Author(s):  
Friedrich-K. Benra ◽  
Verena Klapdor ◽  
Michael Schulten
Keyword(s):  
Surface Roughness ◽  
Centrifugal Compressor ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Numerical Code ◽  
Design Point ◽  
Theoretical Approaches ◽  
Wide Range ◽  
The Impact ◽  
Additional Losses

To discuss the impact of the surface roughness on the efficiency of shrouded centrifugal compressor impellers, this paper presents a theoretical examination of different parameters influencing their aerodynamic behavior. The work is based on the available literature about the influence of surface roughness on the aerodynamics of fluids. An algorithm was derived from different theoretical approaches, which allows computation of the prospective efficiency deficit of radial impellers, dependent on the specific technical roughness. With the help of a numerical code, the impact of several parameters on the efficiency of a shrouded radial impeller due to surface roughness was evaluated. Additional to the expected efficiency drop at the design point of the impeller, the computations were extended for a wide range of operating conditions covering partial loading as well as overloading conditions. All results are discussed in comparison to a hydraulically smooth impeller surface. Thus, only additional losses due to surface roughness are focused on.

Sensitivity Analysis of Large Unit Spiral Case for Different Reinforcement Arrangement

2011 ◽  
Vol 474-476 ◽  
pp. 1855-1858
Author(s):  
Xin Yong Xu ◽  
Jian Wei Wang ◽  
Zhen Yue Ma
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Model ◽  
Mechanical Characteristics ◽  
Reinforcement Ratio ◽  
Hydropower Station ◽  
Large Unit ◽  
Steel Bar ◽  
Spiral Case ◽  
The Impact ◽  
Ratio Range

A numerical model for spiral case of hydropower station is built. The contact is considered and the sensitivity analysis for different reinforcement ratio is analyzed. The impact of different ratios on structure is studied. The stress and mechanical characteristics of steel bar is analyzed. The contact status is taken. The rational reinforcement ratio range, the process and evolution regularity of concrete cracks from microcosmic aspect to macroscopic aspect are obtained.

Numerical Study of Blood Flow at the End-to-Side Anastomosis of a Left Ventricular Assist Device for Adult Patients

2008 ◽  
Author(s):  
Ning Yang ◽  
Steven Deutsch ◽  
Eric G. Paterson ◽  
Keefe B. Manning
Keyword(s):  
Blood Flow ◽  
Left Ventricular ◽  
Operating Conditions ◽  
Adult Patients ◽  
Ventricular Assist Devices ◽  
Shear Stresses ◽  
Ventricular Assist ◽  
Outflow Cannula ◽  
The Impact ◽  
Secondary Vessels

Ventricular assist devices (VADs) have been used for years in adult patients with end-stage heart failure, during bridge-to-transplant, and they have recently shown promise in aiding in myocardial recovery [1]. While the fluid mechanics within VADs has been studied extensively [2], an area which must be more adequately addressed is the outflow cannula attached as an end-to-side anastomosis to the aorta. This attachment may lead to unnaturally high and low shear stresses, turbulence, flow separation, and stagnant flows. As a result, platelet activation and thrombus formation may occur. May-Newman et al. [3] developed a laminar, continuous, computational fluid dynamics (CFD) model to study how different outflow cannula anastomoses affect flow patterns in an adult aortic model. Turbulent flows, however, were not considered. The effects of the anastomosis on the flows in the secondary vessels were neglected as well. There is a lack of detailed description of the flow field across the cannulated adult aorta based on different VAD outflow cannula configurations and operating conditions. As a result, we have developed a comprehensive model to simulate turbulent blood flow in three-dimensional models of the cannulated adult aorta under continuous flow conditions and to study the impact of the secondary vessels on the aortic arch.

scholarly journals Sensitivity Analysis of the Dynamic Behavior of a Salient-Pole Synchronous Machine Considering the Static Rotor Eccentricity Effect

2012 ◽  
Vol 10 (5) ◽  
Author(s):  
I. Albino Padilla ◽  
D. Olguín Salinas ◽  
A. Román Messina
Keyword(s):  
Sensitivity Analysis ◽  
Synchronous Machine ◽  
Operating Conditions ◽  
Synchronous Machines ◽  
Salient Pole ◽  
Salient Pole Synchronous Machine ◽  
Static Eccentricity ◽  
And Performance ◽  
The Impact

This paper presents the sensitivity analysis of the behavior of a synchronous machine using the winding functiontheory considering the effect of static air-gap eccentricity. The winding function theory as a method to calculate theinductances of synchronous machines from the geometry and the actual arranging of the windings is presented. Then,detailed numerical simulations are carried out to examine the impact of eccentricity on the steady state regimes. Theimportant role of static eccentricity and its links with various symmetrical and asymmetrical operating conditions arediscussed as well as its influence on the machine parameters and performance are investigated. Experimental andanalytical parameter results are presented for a 60 Hz, six-pole laboratory synchronous machine connected to aninfinite bus under various static eccentricity conditions.

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