Least Squares Fitting of Computational Fluid Dynamics Results to Measured Vertical Wind Profiles

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Adaiana F. Gomes da Silva ◽  
Edson Luiz Zaparoli ◽  
Cláudia R. Andrade
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Least Squares ◽  
Least Squares Method ◽  
Flow Characteristics ◽  
Main Tool ◽  
Adjustment Process ◽  
Bolund Hill ◽  
Wind Profiles ◽  
Mean Square Errors

Microscale numerical modeling is currently the main tool used in wind industry to assess local wind resources. This paper presents a systematic procedure to adjust computational fluid dynamics (CFD) predicted wind profiles to experimental measurements in order to minimize their differences. It can be applied when wind measurements are available. Data from ten masts with several measurement heights from the well-known Bolund hill experiment provided the observed wind profiles. Simulated profiles were calculated with windsim CFD model for the aforementioned site. Speed-up correction factors were defined through the least squares method to cross-correlate each mast as reference to all the others inside the Bolund hill domain. After, the observed and the adjusted wind profiles at the same position were compared. Moreover, root mean square errors (RMSEs) were used as a metric to evaluate the estimations and the ability of each position to be predicted and predictor. Results have shown that the quality of the adjustment process depends on the flow characteristics at each position related to the incoming wind direction. Most affected positions, i.e., when the airflow overcomes the Bolund hill escarpment, present the less accurate wind profile estimations. The reference mast should be installed upstream of the potential wind turbines' locations and after the main local characteristics of topographical changes.

scholarly journals Analysis of a Converging, Annular, Isothermal Melt Blowing Jet Using Computational Fluid Dynamics

2005 ◽  
Vol os-14 (3) ◽  
pp. 1558925005os-14
Author(s):  
Eric M. Moore ◽  
Dimitrios V. Papavassiliou ◽  
Robert L. Shambaugh
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Near Field ◽  
Flow Characteristics ◽  
Sectional Area ◽  
Melt Blowing ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Computational Fluid Dynamics Cfd

An unconventional melt blowing die was analyzed using computational fluid dynamics (CFD). This die has an annular configuration wherein the jet inlet is tapered (the cross-sectional area decreases) as the air approaches the die face. It was found that the flow characteristics of this die are different from conventional slot and annular dies. In particular, for the tapered die the near-field normalized turbulent kinetic energy was found to be lower at shallow die angles. Also, it was found that the peak mean velocity behavior was intermediate between that of conventional annular and slot dies. The centerline turbulence profiles were found to be qualitatively similar to those of annular dies; quantitatively, higher values were present for tapered dies.

Computed tomography angiography as an adjunct to computational fluid dynamics for prediction of oxygenator thrombus formation

Perfusion ◽  
2020 ◽  
pp. 026765912094410
Author(s):  
Robert G Conway ◽  
Jiafeng Zhang ◽  
Jean Jeudy ◽  
Charles Evans ◽  
Tieluo Li ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computed Tomography ◽  
Computational Fluid Dynamics ◽  
Computed Tomography Angiography ◽  
Thrombus Formation ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Region Of Interest ◽  
Computational Fluid Dynamics Analysis ◽  
Clot Burden

Introduction: Extracorporeal membrane oxygenation circuit performance can be compromised by oxygenator thrombosis. Stagnant blood flow in the oxygenator can increase the risk of thrombus formation. To minimize thrombogenic potential, computational fluid dynamics is frequently applied for identification of stagnant flow conditions. We investigate the use of computed tomography angiography to identify flow patterns associated with thrombus formation. Methods: A computed tomography angiography was performed on a Quadrox D oxygenator, and video densitometric parameters associated with flow stagnation were measured from the acquired videos. Computational fluid dynamics analysis of the same oxygenator was performed to establish computational fluid dynamics–based flow characteristics. Forty-one Quadrox D oxygenators were sectioned following completion of clinical use. Section images were analyzed with software to determine oxygenator clot burden. Linear regression was used to correlate clot burden to computed tomography angiography and computational fluid dynamics–based flow characteristics. Results: Clot burden from the explanted oxygenators demonstrated a well-defined pattern, with the largest clot burden at the corner opposite the blood inlet and outlet. The regression model predicted clot burden by region of interest as a function of time to first opacification on computed tomography angiography (R2 = 0.55). The explanted oxygenator clot burden map agreed well with the computed tomography angiography predicted clot burden map. The computational fluid dynamics parameter of residence time, when summed in the Z-direction, was partially predictive of clot burden (R2 = 0.35). Conclusion: In the studied oxygenator, clot burden follows a pattern consistent with clinical observations. Computed tomography angiography–based flow analysis provides a useful adjunct to computational fluid dynamics–based flow analysis in understanding oxygenator thrombus formation.

scholarly journals Modelling river history and evolution

2012 ◽  
Vol 370 (1966) ◽  
pp. 2123-2142 ◽  
Author(s):  
T. J. Coulthard ◽  
M. J. Van De Wiel
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Landscape Evolution ◽  
Numerical Models ◽  
Flow Characteristics ◽  
Sedimentary Facies ◽  
Cellular Models ◽  
Depositional Processes ◽  
Alluvial Architecture ◽  
Dynamics Models

Over the last few decades, a suite of numerical models has been developed for studying river history and evolution that is almost as diverse as the subject of river history itself. A distinction can be made between landscape evolution models (LEMs), alluvial architecture models, meander models, cellular models and computational fluid dynamics models. Although these models share some similarities, there also are notable differences between them, which make them more or less suitable for simulating particular aspects of river history and evolution. LEMs embrace entire drainage basins at the price of detail; alluvial architecture models simulate sedimentary facies but oversimplify flow characteristics; and computational fluid dynamics models have to assume a fixed channel form. While all these models have helped us to predict erosion and depositional processes as well as fluvial landscape evolution, some areas of prediction are likely to remain limited and short-term owing to the often nonlinear response of fluvial systems. Nevertheless, progress in model algorithms, computing and field data capture will lead to greater integration between these approaches and thus the ability to interpret river history more comprehensively.

Computational Fluid Dynamics Modeling of Gas–Liquid Cylindrical Cyclones, Geometrical Analysis

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Juan Carlos Berrio ◽  
Eduardo Pereyra ◽  
Nicolas Ratkovich
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Cfd Modeling ◽  
Nozzle Geometry ◽  
Geometrical Parameters ◽  
Experimental Setup ◽  
Dynamics Modeling ◽  
Two Phase ◽  
Mean Square Errors

The gas–liquid cylindrical cyclone (GLCC) is a widely used alternative for gas–liquid conventional separation. Besides its maturity, the effect of some geometrical parameters over its performance is not fully understood. The main objective of this study is to use computational fluid dynamics (CFD) modeling in order to evaluate the effect of geometrical modifications in the reduction of liquid carry over (LCO) and gas carry under (GCU). Simulations for two-phase flow were carried out under zero net liquid flow, and the average liquid holdup was compared with Kanshio (Kanshio, S., 2015, “Multiphase Flow in Pipe Cyclonic Separator,” Ph.D. thesis, Cranfield University, Cranfield, UK) obtaining root-mean-square errors around 13% between CFD and experimental data. An experimental setup, in which LCO data were acquired, was built in order to validate a CFD model that includes both phases entering to the GLCC. An average discrepancy below 6% was obtained by comparing simulations with experimental data. Once the model was validated, five geometrical variables were tested with CFD. The considered variables correspond to the inlet configuration (location and inclination angle), the effect of dual inlet, and nozzle geometry (diameter and area reduction). Based on the results, the best configuration corresponds to an angle of 27 deg, inlet location 10 cm above the center, a dual inlet with 20 cm of spacing between both legs, a nozzle of 3.5 cm of diameter, and a volute inlet of 15% of pipe area. The combination of these options in the same geometry reduced LCO by 98% with respect to the original case of the experimental setup. Finally, the swirling decay was studied with CFD showing that liquid has a greater impact than the gas flowrate.

The Flow Characteristics of Nanometer Microspheres in the Vessel

2013 ◽  
Vol 404 ◽  
pp. 167-170
Author(s):  
Yong Bo Yang ◽  
Li Min Qiao ◽  
Rui Gu ◽  
Xue Shan Liu ◽  
Guang Sen Zhou
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Computational Result ◽  
Blood Viscosity ◽  
Drug Carrier ◽  
Flow Characteristics ◽  
Diffusion Flow ◽  
Curative Effect ◽  
Flow Phenomenon ◽  
Biotechnology Research

The application of the nanoparticle technology is more and more popular currently. For the excellent abilities, nanoparticle technology is widely used in the biotechnology research. Nanometer microspheres can be used as a drug carrier. But the blood viscosity has relatively greater influence on its flow performance. The flow characteristics of nanometer microspheres in the vessel is very important to the curative effect. In order to resolve this problem, a length of vessel is introduced. By the CFD(computational fluid dynamics) software, the diffusion flow phenomenon is studied. The computational result and the analysis show that the nanometer microspheres would mix rapidly around the corner of the vessel. The results may provide technical reference of the further research.

scholarly journals Propeller Performance Penalty of Biofouling: Computational Fluid Dynamics Prediction

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Soonseok Song ◽  
Yigit Kemal Demirel ◽  
Mehmet Atlar
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Characteristics ◽  
Open Water ◽  
Roughness Effect ◽  
Thrust Coefficient ◽  
Propulsion Performance ◽  
Negative Effect ◽  
Open Water Performance ◽  
Propeller Performance

Abstract The negative effect of biofouling on ship resistance has been investigated since the early days of naval architecture. However, for more precise prediction of fuel consumption of ships, understanding the effect of biofouling on ship propulsion performance is also important. In this study, computational fluid dynamics (CFD) simulations for the full-scale performance of KP505 propeller in open water, including the presence of marine biofouling, were conducted. To predict the effect of barnacle fouling on the propeller performance, experimentally obtained roughness functions of barnacle fouling were used in the wall-function of the CFD software. The roughness effect of barnacles of varying sizes and coverages on the propeller open water performance was predicted for advance coefficients ranging from 0.2 to 0.8. From the simulations, drastic effects of barnacle fouling on the propeller open water performance were found. The result suggests that the thrust coefficient decreases while the torque coefficient increases with increasing level of surface fouling, which leads to a reduction of the open water efficiency of the propeller. Using the obtained result, the penalty of propeller fouling on the required shaft power was predicted. Finally, further investigations were made into the roughness effect on the flow characteristics around the propeller and the results were in correspondence with the findings on the propeller open water performance.

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