scholarly journals A vortex-based tip/smearing correction for the actuator line

2019 ◽  
Vol 4 (2) ◽  
pp. 369-383 ◽  
Author(s):  
Alexander R. Meyer Forsting ◽  
Georg Raimund Pirrung ◽  
Néstor Ramos-García
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Test Cases ◽  
Near Wake ◽  
Speed Range ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Applications ◽  
Flow Domain ◽  
Viscous Core ◽  
Lifting Line

Abstract. The actuator line (AL) was intended as a lifting line (LL) technique for computational fluid dynamics (CFD) applications. In this paper we prove – theoretically and practically – that smearing the forces of the actuator line in the flow domain forms a viscous core in the bound and shed vorticity of the line. By combining a near-wake representation of the trailed vorticity with a viscous vortex core model, the missing induction from the smeared velocity is recovered. This novel dynamic smearing correction is verified for basic wing test cases and rotor simulations of a multimegawatt turbine. The latter cover the entire operational wind speed range as well as yaw, strong turbulence and pitch step cases. The correction is validated with lifting line simulations with and without viscous core, which are representative of an actuator line without and with smearing correction, respectively. The dynamic smearing correction makes the actuator line effectively act as a lifting line, as it was originally intended.

scholarly journals A vortex-based tip/smearing correction for the actuator line

2019 ◽  
Author(s):  
Alexander Raul Meyer Forsting ◽  
Georg Raimund Pirrung ◽  
Néstor Ramos-García
Keyword(s):  
Wind Speed ◽  
Vortex Core ◽  
Velocity Fields ◽  
Test Cases ◽  
Near Wake ◽  
Speed Range ◽  
Cfd Applications ◽  
Flow Domain ◽  
Viscous Core ◽  
Lifting Line

Abstract. The actuator line was intended as a lifting line technique for CFD applications. In this paper we proof – theoretically and practically – that smearing the forces of the actuator line in the flow domain necessarily leads to smeared velocity fields. By combining a near-wake representation of the trailed vorticity with a viscous vortex core model, the missing induction from the smeared velocity is recovered. This novel dynamic smearing correction is verified for basic wing test cases and rotor simulations of a multi-MW turbine. The latter cover the entire operational wind speed range as well as yaw, strong turbulence and pitch step cases. The correction is validated with lifting line simulations with and without viscous core, that are representative of an actuator line without and with smearing correction, respectively. The dynamic smearing correction makes the actuator line effectively act as a lifting line, as it was originally intended.

scholarly journals Propagation of Input Uncertainty in Presence of Model-Form Uncertainty: A Multifidelity Approach for Computational Fluid Dynamics Applications

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Jian-Xun Wang ◽  
Christopher J. Roy ◽  
Heng Xiao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Parameter Space ◽  
Uncertainty Propagation ◽  
High Fidelity ◽  
Sampling Errors ◽  
Uncertainty Distribution ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Applications

Proper quantification and propagation of uncertainties in computational simulations are of critical importance. This issue is especially challenging for computational fluid dynamics (CFD) applications. A particular obstacle for uncertainty quantifications in CFD problems is the large model discrepancies associated with the CFD models used for uncertainty propagation. Neglecting or improperly representing the model discrepancies leads to inaccurate and distorted uncertainty distribution for the quantities of interest (QoI). High-fidelity models, being accurate yet expensive, can accommodate only a small ensemble of simulations and thus lead to large interpolation errors and/or sampling errors; low-fidelity models can propagate a large ensemble, but can introduce large modeling errors. In this work, we propose a multimodel strategy to account for the influences of model discrepancies in uncertainty propagation and to reduce their impact on the predictions. Specifically, we take advantage of CFD models of multiple fidelities to estimate the model discrepancies associated with the lower-fidelity model in the parameter space. A Gaussian process (GP) is adopted to construct the model discrepancy function, and a Bayesian approach is used to infer the discrepancies and corresponding uncertainties in the regions of the parameter space where the high-fidelity simulations are not performed. Several examples of relevance to CFD applications are performed to demonstrate the merits of the proposed strategy. Simulation results suggest that, by combining low- and high-fidelity models, the proposed approach produces better results than what either model can achieve individually.

Good modelling practice in applying computational fluid dynamics for WWTP modelling

2015 ◽  
Vol 73 (5) ◽  
pp. 969-982 ◽  
Author(s):  
Edward Wicklein ◽  
Damien J. Batstone ◽  
Joel Ducoste ◽  
Julien Laurent ◽  
Alonso Griborio ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Working Group ◽  
Companion Paper ◽  
Cfd Modelling ◽  
Cfd Models ◽  
Water Association ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Applications ◽  
International Water

Computational fluid dynamics (CFD) modelling in the wastewater treatment (WWT) field is continuing to grow and be used to solve increasingly complex problems. However, the future of CFD models and their value to the wastewater field are a function of their proper application and knowledge of their limits. As has been established for other types of wastewater modelling (i.e. biokinetic models), it is timely to define a good modelling practice (GMP) for wastewater CFD applications. An International Water Association (IWA) working group has been formed to investigate a variety of issues and challenges related to CFD modelling in water and WWT. This paper summarizes the recommendations for GMP of the IWA working group on CFD. The paper provides an overview of GMP and, though it is written for the wastewater application, is based on general CFD procedures. A forthcoming companion paper to provide specific details on modelling of individual wastewater components forms the next step of the working group.

An Introduction to Computational Fluid Dynamics and Its Application in Microfluidics

2019 ◽  
pp. 50-78
Author(s):  
João Lameu da Silva Júnior
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Single Phase ◽  
Chemical Engineering ◽  
Numerical Technique ◽  
Quality Parameters ◽  
Flow In Porous Media ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Applications ◽  
Volume Method

The chapter aims to introduce the computational fluid dynamics (CFD). A review was provided, outlining its development and applications on chemical engineering and microfluidics. The fundamental points of the CFD, listing the advantages and precautions of this numerical technique were provided. The description of CFD methodology including the three essential stages (pre-processing, solving, and post-processing) was made. The fundamental transport equations—total mass (continuity), momentum, energy, and species mass balances—and the usual boundary conditions used in CFD were explained. The main approaches used in multicomponent single-phase flows, single-phase flow in porous media, and multiphase flows in microscale were detailed, as well as the numerical mesh types and its quality parameters. A brief introduction of finite volume method (FVM) used by most of the available CFD codes was also performed, describing the main numerical solution features. Finally, the conclusions and future prospects of CFD applications are exposed.

Achieving high parallel performance for an unstructured unsteady turbomachinery CFD code

2007 ◽  
Vol 111 (1117) ◽  
pp. 185-193 ◽  
Author(s):  
N. Hills
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Steady State ◽  
Load Balancing ◽  
Unstructured Mesh ◽  
Test Cases ◽  
Hexahedral Mesh ◽  
Parallel Performance ◽  
Computational Fluid Dynamics Cfd ◽  
Work Done

This paper describes the work done to achieve high parallel performance for an unstructured, unsteady turbomachinery computational fluid dynamics (CFD) code. The aim of the work described here is to be able to scale problems to the thousands of processors that current and future machine architectures will provide. The CFD code is in design use in industry and is also used as a research tool at a number of universities. High parallel scalability has been achieved for a range of turbomachinery test cases, from steady-state hexahedral mesh cases to fully unsteady unstructured mesh cases. This has been achieved by a combination of code modification and consideration of the parallel partitioning strategy and resulting load balancing. A sliding plane option is necessary to run fully unsteady multistage turbomachinery test cases and this has been implemented within the CFD code. Sample CFD calculations of a full turbine including parts of the internal air system are presented.

Modelling the effect of computation sampling on insight error in computational fluid dynamics scientific simulation

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Moeti Masiane ◽  
Eric Jacques ◽  
Wuchun Feng ◽  
Chris North
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Design Methodology ◽  
Cfd Simulation ◽  
Grid Resolution ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
Independent Variable ◽  
Cfd Applications ◽  
The Ideal

Purpose The purpose of this paper is to collect data from humans as they generate insights from the visualised results of computational fluid dynamics (CFD) scientific simulation. The authors hypothesise the behaviour of their insight errors (IEs) and proceed to quantify the IEs provided by the crowd participants. They then use the insight framework to model the behaviours of the errors. Using the crowd responses and models from the framework, they test the hypotheses and use the results to validate the framework for the speedup of CFD applications. Design/methodology/approach The authors use a randomised between-subjects experiment with blocking. CFD grid resolution is the independent variable while IE is the dependent variable. The experiment has one treatment factor with five levels. In case varying timestamps has an effect on insight variance levels, the authors block the responses by timestep. In total, 150 participants are randomly assigned to one of five groups and also randomly assigned to one of five blocks within a treatment. Participants are asked to complete a benchmark and open-ended task. Findings The authors find that the variances of insight and perception errors have a U-shaped relationship with grid resolution, that similar to the previously studied visualisation applications, the IE framework is valid for insights generated from CFD results and grid resolution can be used to predict the variance of IE resulting from observing CFD post-processing results. Originality/value To the best of the authors’ knowledge, no other work has measured IE variance to present it to simulation users so that they can use it as a feedback metric for selecting the ideal grid resolution when using grid resolution to speedup CFD simulation.

Simulating Coil Embolization Treatments of Intracranial Aneurysms Using Computational Fluid Dynamics

2019 ◽  
Author(s):  
Nikhil Tulshibagwale ◽  
Stephen P. Gent
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Coil Embolization ◽  
Fluid Velocity ◽  
Volume Flow ◽  
Patient Specific ◽  
Test Cases ◽  
Aneurysm Neck ◽  
Test Models ◽  
Computational Fluid Dynamics Cfd

In this study, a commercially available computational fluid dynamics (CFD) program was used to simulate coil embolization techniques, standard coiling (SC) and stent-assisted coiling (SAC), in simplified vessels that are representative of vessels found in the brain. The test models included a curved vessel, ranging from 3mm to 4mm in diameter. The vessel was afflicted with a spherical aneurysm, ranging from 8mm to 16mm in diameter. The four test cases were simulated without treatment, with SC treatment, and with SAC treatment, for a total of twelve simulations. The parameters of interest were blood volume flow into aneurysm, fluid velocity, wall shear stress (WSS), and vorticity. Results of the simulations indicate, on average, SC and SAC reduced volume flow into the aneurysm by 50% and to over 60%, respectively. Both SC and SAC appeared to reduce distal neck WSS. Both treatments reduced average overall dome WSS by approximately 76%. Average aneurysm neck velocity was reduced by both treatments; SC reduced neck velocity by 69% and SAC reduced neck velocity by 75%. Information on SC and SAC efficacy in idealized scenarios could assist medical professionals determining viable approaches for patient-specific cases and lays foundation for future CFD studies exploring coil embolization treatments.

CFD Applications for Coal/Air Balancing in Power Plants

2003 ◽  
Author(s):  
Sowjanya Vijiapurapu ◽  
Jie Cui ◽  
Sastry Munukutla
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Power Plants ◽  
Air Flow ◽  
New Method ◽  
Industry Practice ◽  
Clean Air ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Applications

A new method for balancing coal / air flow to individual burners connected to a mill in a pulverized coal fired unit was proposed. A generalized calculation procedure based on this method was developed for sizing the orifices needed for balancing the coal / air flow. Efficient use of commercially available computational fluid dynamics (CFD) software was suggested for the calculation of the pressure drop in pipes with unclear specifications of geometries. The current industry practice is to balance the clean air flow and accept the resulting imbalance in the coal / air flow. By this new method the clean-air flow would be unbalanced in a tailored manner so that balanced coal / air flow would result. In order to implement this new method the power plants would still have to conduct clean air tests only.

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