scholarly journals Correcting Transport Errors During Advection of Aerosol and Cloud Moment Sequences in Eulerian Models

10.5772/34090 ◽  
2012 ◽  
Author(s):  
Robert McGraw
Keyword(s):  
Eulerian Models

scholarly journals Improved source term description in Eulerian models in ARGOS

2016 ◽  
Vol 51 ◽  
pp. S125-S127 ◽  
Author(s):  
H. Klein ◽  
J. Bartnicki ◽  
J.E. Dyve
Keyword(s):  
Source Term ◽  
Eulerian Models

Verification Benchmarks to Assess the Implementation of Computational Fluid Dynamics Based Hemolysis Prediction Models

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Prasanna Hariharan ◽  
Gavin D’Souza ◽  
Marc Horner ◽  
Richard A. Malinauskas ◽  
Matthew R. Myers
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Power Law ◽  
Analytical Solutions ◽  
Experimental Validation ◽  
Cfd Simulations ◽  
Flow Models ◽  
Flow Acceleration ◽  
Blood Damage ◽  
Eulerian Models

As part of an ongoing effort to develop verification and validation (V&V) standards for using computational fluid dynamics (CFD) in the evaluation of medical devices, we have developed idealized flow-based verification benchmarks to assess the implementation of commonly cited power-law based hemolysis models in CFD. The verification process ensures that all governing equations are solved correctly and the model is free of user and numerical errors. To perform verification for power-law based hemolysis modeling, analytical solutions for the Eulerian power-law blood damage model (which estimates hemolysis index (HI) as a function of shear stress and exposure time) were obtained for Couette and inclined Couette flow models, and for Newtonian and non-Newtonian pipe flow models. Subsequently, CFD simulations of fluid flow and HI were performed using Eulerian and three different Lagrangian-based hemolysis models and compared with the analytical solutions. For all the geometries, the blood damage results from the Eulerian-based CFD simulations matched the Eulerian analytical solutions within ∼1%, which indicates successful implementation of the Eulerian hemolysis model. Agreement between the Lagrangian and Eulerian models depended upon the choice of the hemolysis power-law constants. For the commonly used values of power-law constants (α  = 1.9–2.42 and β  = 0.65–0.80), in the absence of flow acceleration, most of the Lagrangian models matched the Eulerian results within 5%. In the presence of flow acceleration (inclined Couette flow), moderate differences (∼10%) were observed between the Lagrangian and Eulerian models. This difference increased to greater than 100% as the beta exponent decreased. These simplified flow problems can be used as standard benchmarks for verifying the implementation of blood damage predictive models in commercial and open-source CFD codes. The current study used only a power-law model as an illustrative example to emphasize the need for model verification. Similar verification problems could be developed for other types of hemolysis models (such as strain-based and energy dissipation-based methods). And since the current study did not include experimental validation, the results from the verified models do not guarantee accurate hemolysis predictions. This verification step must be followed by experimental validation before the hemolysis models can be used for actual device safety evaluations.

Linking Lagrangian model simulations with stable water isotope measurements in Arctic weather systems.

2021 ◽  
Author(s):  
Aina Johannessen ◽  
Alena Dekhtyareva ◽  
Andrew Seidl ◽  
Harald Sodemann
Keyword(s):  
Water Cycle ◽  
Lagrangian Model ◽  
Water Isotopes ◽  
Stable Water Isotopes ◽  
Atmospheric Water ◽  
Model Simulations ◽  
Evaporation Source ◽  
Isotope Measurements ◽  
Water Isotope ◽  
Eulerian Models

<p>Transport of water from an evaporation source towards a precipitation sink is the essence of the atmospheric water cycle. However, there are significant challenges with the representation of the atmospheric water cycle in models. For example, incomplete representation of sub-grid scale processes like evaporation, mixing or precipitation can lead to substantial model errors. Here we investigate the combined use of Lagrangian and Eulerian models and in-situ observations of stable water isotopes to reduce such sources of model error. The atmospheric water cycle in the Nordic Seas during cold air outbreaks (CAOs) is confined to a limited area, and thus may be used as a natural laboratory for hydrometeorological studies. We apply Lagrangian and Eulerian models together with observations taken during the ISLAS2020 field campaign in the Arctic in spring 2020 for characterising source-sink relationships in the water cycle. During the field campaign, we observed an alternating sequence of cold air outbreaks (CAO) and warm air intrusions (WAI) over the key measurement sites of Svalbard and northern Norway. Thereby, meteorological and stable water isotope measurements have been performed at multiple sites both upstream and downstream of the CAOs and WAIs. The Lagrangian model FLEXPART has been run with the input data from the regional convection-permitting numerical weather prediction model AROME Arctic at 2.5 km resolution to investigate transport patterns. The combination of observations and model simulations allows us to quantify the connection between source and sink for different weather systems, as well as the link between large-scale transport and stable water isotopes. Findings will lead to a better understanding of processes in the water cycle and the degree of conservation of isotopic signals during transport. This study may also serve as a guideline on how to evaluate the performance of Lagrangian transport models using stable water isotope measurements, and on how to detect constraints for quantifying the transport route and evaporation source from stable water isotope measurements for future work, including an aircraft campaign planned in 2021.</p>

A method to represent seasonal vertical migration of Zooplankton in 3D-Eulerian models

2006 ◽  
Vol 12 (1-2) ◽  
pp. 188-204 ◽  
Author(s):  
Thomas Neumann ◽  
Wolfgang Fennel
Keyword(s):  
Vertical Migration ◽  
Eulerian Models

scholarly journals Eulerian models of the rotating flexible wheelset for high frequency railway dynamics

2019 ◽  
Vol 449 ◽  
pp. 300-314 ◽  
Author(s):  
Luis Baeza ◽  
Juan Giner-Navarro ◽  
David J. Thompson ◽  
Juan Monterde
Keyword(s):  
High Frequency ◽  
Railway Dynamics ◽  
Flexible Wheelset ◽  
Eulerian Models

scholarly journals Thermo-Fluidic Characteristics of Two-Phase Ice Slurry Flows Based on Comparative Numerical Methods

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 898 ◽  
Author(s):  
Shehnaz Akhtar ◽  
Haider Ali ◽  
Cheol Woo Park
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Flow Velocity ◽  
Mass Fraction ◽  
Single Phase ◽  
Ice Slurry ◽  
Two Phase ◽  
Ice Concentration ◽  
Eulerian Models

Ice slurry is a potential secondary refrigerant for commercial refrigeration systems because of its remarkable thermal properties. It is necessary to optimize the heat transfer process of ice slurry to reduce the energy consumption of the refrigeration system. Thus, this study investigates the heat transfer performance of single-phase (aqueous solution) and two-phase (ice slurry) refrigerants in a straight horizontal tube. The numerical simulations for ice slurry were performed with ice mass fraction ranging from 5% to 20%. The effects of flow velocity and ice concentration on the heat transfer coefficient were examined. The results showed that heat transfer coefficient of ice slurry is considerably higher than those of single-phase flow, particularly at high flow velocity and ice content, where increase in heat transfer with a factor of two was observed. The present results confirmed that ice slurry heat transfer ability is considerably affected by flow velocity and ice concentration in laminar range. Moreover, the second part of this paper reports on the credibility three distinct two-phase Eulerian–Eulerian models (volume of fluid (VOF), mixture, and Eulerian) for the experimental conditions reported in the literature. All two-phase models accurately predict the thermal field at low ice mass fraction but underestimate that at high ice mass fractions. Regardless of the thermal discrepancies, the Eulerian–Eulerian models provide quite reasonable estimation of pressure drop with reference to experimental data. The numerical predictions from the VOF model are more accordant with the experimental results and the maximum percentage error is limited to ~20% and ~13% for thermal and pressure drop predictions, respectively.

Development of numerical Eulerian-Eulerian models for simulating multiphase pumps

2018 ◽  
Vol 162 ◽  
pp. 588-601 ◽  
Author(s):  
Jun-Won Suh ◽  
Jin-Woo Kim ◽  
Young-Seok Choi ◽  
Jin-Hyuk Kim ◽  
Won-Gu Joo ◽  
...  
Keyword(s):  
Eulerian Models

Eulerian models for turbulent spray combustion with polydispersity and droplet crossing

2009 ◽  
Vol 337 (6-7) ◽  
pp. 438-448 ◽  
Author(s):  
S. de Chaisemartin ◽  
L. Fréret ◽  
D. Kah ◽  
F. Laurent ◽  
R.O. Fox ◽  
...  
Keyword(s):  
Spray Combustion ◽  
Turbulent Spray Combustion ◽  
Turbulent Spray ◽  
Eulerian Models

scholarly journals The firn meltwater Retention Model Intercomparison Project (RetMIP): Evaluation of nine firn models at four weather station sites on the Greenland ice sheet

2020 ◽  
Author(s):  
Baptiste Vandecrux ◽  
Ruth Mottram ◽  
Peter L. Langen ◽  
Robert S. Fausto ◽  
Martin Olesen ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Weather Station ◽  
Model Intercomparison ◽  
Retention Model ◽  
Intercomparison Project ◽  
In Situ Observations ◽  
Over Time ◽  
Eulerian Models

Abstract. Perennial snow, or firn, covers 80 % of the Greenland ice sheet and has the capacity to retain part of the surface meltwater, buffering the ice sheet’s contribution to sea level. Multi-layer firn models are traditionally used to simulate the firn processes and estimate meltwater retention. We present the output from nine firn models, forced by weather-station-derived mass and energy fluxes at four sites representative of the dry snow, percolation, ice slab and firn aquifer areas. We compare the model outputs and evaluate them against in situ observations. Models that explicitly account for deep meltwater percolation overestimate percolation depth and consequently firn temperature at the percolation and ice slab sites although they accurately simulate the recharge of the firn aquifer. Models using Darcy's law and a bucket scheme compare favourably to observations at the percolation site but only the Darcy models accurately simulate firn temperature and thus meltwater percolation at the ice slab site. We find that Eulerian models, that transfer firn through fixed layers, smooth sharp gradients in firn temperature and density over time. From the model spread, we find that simulated densities (respectively temperature) have an uncertainty envelope of ±60 kg m−3 (resp. ±14 °C) in the dry snow area and up to ±280 kg m−3 (resp. ±15–18 °C) at warmer sites.

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