scholarly journals Snow Particle Collection Efficiency and Adjustment Curves for the Hotplate© Precipitation Gauge

2021 ◽  
Author(s):  
Arianna Cauteruccio ◽  
Enrico Chinchella ◽  
Mattia Stagnaro ◽  
Luca G. Lanza
Keyword(s):  
Wind Speed ◽  
Bluff Body ◽  
Stokes Equations ◽  
Collection Efficiency ◽  
Navier Stokes ◽  
Strong Wind ◽  
Navier Stokes Equations ◽  
Relevant Role ◽  
Tracking Model ◽  
Precipitation Gauge

AbstractThe hotplate precipitation gauge operates by means of a thermodynamic principle. It is composed by a small size disk with two thin aluminium heated plates on the upper and lower faces. Each plate has three concentric rings to prevent the hydrometeors from sliding off in strong wind. As for the more widely used tipping-bucket and weighing gauges, measurements are affected by the wind-induced bias due to the bluff-body aerodynamics of the instrument outer shape. Unsteady Reynolds-Averaged Navier-Stokes equations were numerically solved, using a k-ω shear stress transport closure model, to simulate the aerodynamic influence of the gauge body on the airflow. Wind tunnel tests were conducted to validate simulation results. Solid particle trajectories were modelled using a Lagrangian Particle Tracking model to evaluate the influence of the airflow modification on the ability of the instrument to collect the incoming hydrometeors. A suitable parameterization of the particle size distribution, as a function of the snowfall intensity, was employed to calculate the Collection Efficiency (CE) under different wind conditions. Results reveal a relevant role of the three rings in enhancing the collection performance of the gauge. Below 7.5 m s-1, the CE curves linearly decrease with increasing the wind speed, while beyond that threshold, the blocking caused by the rings counter effects the aerodynamic induced undercatch, and the CE curves quadratically increase with the wind speed. At high wind speed, the undercatch vanishes and the instrument exhibits a rapidly increasing overcatch. For operational purposes, adjustment curves were formulated as a function of the wind speed and the measured snowfall intensity.

scholarly journals Experimental validation of wind energy estimation

2020 ◽  
Vol 24 (6 Part A) ◽  
pp. 3795-3806
Author(s):  
Predrag Zivkovic ◽  
Mladen Tomic ◽  
Vukman Bakic
Keyword(s):  
Wind Speed ◽  
Linear Model ◽  
Linear Models ◽  
Stokes Equations ◽  
Momentum Conservation ◽  
Electricity Production ◽  
Navier Stokes ◽  
Energy Estimation ◽  
Navier Stokes Equations ◽  
Non Linear

Wind power assessment in complex terrain is a very demanding task. Modeling wind conditions with standard linear models does not sufficiently reproduce wind conditions in complex terrains, especially on leeward sides of terrain slopes, primarily due to the vorticity. A more complex non-linear model, based on Reynolds averaged Navier-Stokes equations has been used. Turbulence was modeled by modified two-equations k-? model for neutral atmospheric boundary-layer conditions, written in general curvelinear non-orthogonal co-ordinate system. The full set of mass and momentum conservation equations as well as turbulence model equations are numerically solved, using the as CFD technique. A comparison of the application of linear model and non-linear model is presented. Considerable discrepancies of estimated wind speed have been obtained using linear and non-linear models. Statistics of annual electricity production vary up to 30% of the model site. Even anemometer measurements directly at a wind turbine?s site do not necessarily deliver the results needed for prediction calculations, as extrapolations of wind speed to hub height is tricky. The results of the simulation are compared by means of the turbine type, quality and quantity of the wind data and capacity factor. Finally, the comparison of the estimated results with the measured data at 10, 30, and 50 m is shown.

scholarly journals PENGARUH WINDOW TO WALL RATIO TERHADAP KENYAMANAN FISIOLOGIS DENGAN MENGGUNAKAN CFD ANSYS 14.0

2020 ◽  
Vol 3 (1) ◽  
pp. 37
Author(s):  
Rahmayanti Rahmayanti
Keyword(s):  
Wind Speed ◽  
Total Energy ◽  
Field Measurement ◽  
Air Conditioning ◽  
Natural Ventilation ◽  
Stokes Equations ◽  
Measurement Data ◽  
Field Research ◽  
Navier Stokes ◽  
Navier Stokes Equations

The use of air conditioning energy (AC) as an effort to remove heat in buildings reaches 30% of the total energy needed in the building. To reduce the use of energy in buildings by using natural ventilation because the system does not use mechanics. Field research has been carried out with the result that the openings at Balai Padang are unable to make occupants' comfort. Therefore, the existing openings will be given treatment by wider the existing openings which are 20%, 30%, and 40%. This study purpose to investigate the effect of WWR on histologic comfort. The numerical methodology is based on the solution of the Navier-Stokes equations, using K-epsilon RNG. Numerical results are validated with available field measurement data. The results obtained that by increasing the percentage of openings, the wind speed is also highPenggunaan energi air conditioning (AC) sebagai upaya penghapus panas di dalam bangunan mencapai 30% dari total energi yang dibutuhkan di dalam bangunan. Upaya yang dilakukan untuk mengurangi penggunaan energi di dalam bangunan yakni dengan menggunakan penghawaan alami sebagai penghapus panas karena sistemnya yang tidak menggunakan mekanis. Penelitian lapangan telah dilakukan dengan hasil bahwa bukaan yang ada di Balai Padang tidak mampu mencukupi kebutuhan kecepatan angin yang diperlukan untuk mendinginkan fisiologis penghuni. Oleh karena itu, bukaan yang ada akan diberikan perlakuan dengan memperbesar bukaan yang ada yakni 20%, 30% dan 40%. Penelitian ini bertujuan untuk mengetahui efek dari WWR terhadap kenyamanan fisiologis penghuni.  Metode yang digunakan adalah eksperimental dengan menggunakan bantuan software CFD (computational Fluid Dimension) berdasarkan persamaan Navier-Stoke, menggunakan K-Epsilon RNG. Eksperimen dilakukan dengan validasi hasil pengukuran lapangan. Hasil yang didapatkan bahwa dengan menambah prosentase bukaan, kecepatan angin juga semakin besar.

scholarly journals Weakly nonlinear modelling of a forced turbulent axisymmetric wake

2017 ◽  
Vol 814 ◽  
pp. 570-591 ◽  
Author(s):  
Georgios Rigas ◽  
Aimee S. Morgans ◽  
Jonathan F. Morrison
Keyword(s):  
Turbulent Flows ◽  
Bluff Body ◽  
Stokes Equations ◽  
Nonlinear Models ◽  
Navier Stokes ◽  
Turbulent Regime ◽  
Navier Stokes Equations ◽  
Weakly Nonlinear ◽  
Zero Net Mass Flux ◽  
High Reynolds

A theory is presented where the weakly nonlinear analysis of laminar globally unstable flows in the presence of external forcing is extended to the turbulent regime. The analysis is demonstrated and validated using experimental results of an axisymmetric bluff-body wake at high Reynolds numbers, $Re_{D}\sim 1.88\times 10^{5}$, where forcing is applied using a zero-net-mass-flux actuator located at the base of the blunt body. In this study we focus on the response of antisymmetric coherent structures with azimuthal wavenumbers $m=\pm 1$ at a frequency $St_{D}=0.2$, responsible for global vortex shedding. We found experimentally that axisymmetric forcing ($m=0$) couples nonlinearly with the global shedding mode when the flow is forced at twice the shedding frequency, resulting in parametric subharmonic resonance through a triadic interaction between forcing and shedding. We derive simple weakly nonlinear models from the phase-averaged Navier–Stokes equations and show that they capture accurately the observed behaviour for this type of forcing. The unknown model coefficients are obtained experimentally by producing harmonic transients. This approach should be applicable in a variety of turbulent flows to describe the response of global modes to forcing.

Evaluation of wind-induced errors for the Hotplate precipitation gauge using computational fluid dynamic simulations.

2020 ◽  
Author(s):  
Enrico Chinchella ◽  
Arianna Cauteruccio ◽  
Mattia Stagnaro ◽  
Andrea Freda ◽  
Luca Giovanni Lanza
Keyword(s):  
Particle Size ◽  
Wind Speed ◽  
Velocity Field ◽  
Wind Velocity ◽  
Complex Geometry ◽  
Collection Efficiency ◽  
Fluid Dynamic ◽  
Strong Wind ◽  
Precipitation Gauge ◽  
Number Of Particles

<p>Wind is recognised as the major environmental source of error in precipitation measurements. For traditional catching type gauges, which are composed by a funnel to collect the precipitation and a container with a bluff body shape, the exposure effect produces the updraft and acceleration of the velocity field in front and above of the collector. These divert the trajectories of approaching hydrometeors producing  a relevant under-catch, which increases with increasing the wind velocity. This problem has been recently addressed in the literature using Computational Fluid Dynamics (CFD) simulations and a Lagrangian Particle Tracking (LPT) model to provide correction curves for various instruments, which closely match the under-catch observed in field measurements.</p><p>The present work concentrates on the Hotplate precipitation gauge developed at the Research Applications Laboratory, National Center for Atmospheric Research in Boulder, Colorado. The Hotplate differs from the traditional catching type gauges because it operates by means of an indirect thermodynamic principle. Therefore, it is not equipped with any funnel to collect the precipitation and is composed by a small disk with a diameter of 13 cm with two thin aluminium heated plates on the upper and lower faces. On the plates three concentric rings are installed to prevent the hydrometeors from sliding off during strong wind conditions.</p><p>In order to quantify the wind-induced error, the Unsteady Reynolds Averaged Navier Stokes (URANS) equations were numerically solved, with a k-ω SST turbulence closure model, to calculate the airflow velocity field around the instrument. Numerical results were validated by comparison with wind tunnel flow velocity measurements from pressure probes and a Particle Image Velocimetry (PIV) technique.</p><p>Then, with the objective to calculate the Collection Efficiency (CE) the hydrometeor trajectories were modelled using a literature LPT model (Colli et al. 2015) that solves the particle motion equation under the effects of gravity and wind. The path of each particle was analysed, considering the complex geometry of the gauge body, to establish whether it is captured by the instrument or not.</p><p>For various particle size/wind velocity combinations, the ratio between the number of particles captured by the instrument and the number of particles that would be captured if the instrument was transparent to the wind was calculated. Finally, the CE curve was derived assuming a suitable particle size distribution for solid precipitation.</p><p>The results show that the Hotplate gauge presents a very unique response to the wind if compared with more traditional instruments. The CE indeed decreases with increasing the wind speed up to 7.5 m/s, where the effect of geometry starts to overcome the aerodynamic effect, and slowly reverses the trend beyond that value. This effect is so prominent at high wind speed that slightly beyond 15 m/s the under-catch fully disappears and the instrument starts to exhibit a rapidly increasing over-catching bias.</p><p><strong>References:</strong></p><p>Colli, M., Lanza, L.G., Rasmussen, R., Thériault, J.M., Baker, B.C. & Kochendorfer, J. An improved trajectory model to evaluate the collection performance of snow gauges.  Journal of Applied Meteorology and Climatology, 2015, 54, 1826–1836.</p>

scholarly journals Wind Farm Fault Detection by Monitoring Wind Speed in the Wake Region

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6559
Author(s):  
Minh-Quang Tran ◽  
Yi-Chen Li ◽  
Chen-Yang Lan ◽  
Meng-Kun Liu
Keyword(s):  
Energy Dissipation ◽  
Wind Speed ◽  
Fault Detection ◽  
Wind Turbine ◽  
Wind Farm ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Wake Region ◽  
Navier Stokes Equations ◽  
Dissipation Model

A novel concept of wind farm fault detection by monitoring the wind speed in the wake region is proposed in this study. A wind energy dissipation model was coupled with a computational fluid dynamics solver to simulate the fluid field of a wind turbine array, and the wind velocity and direction in the simulation were exported for identifying wind turbine faults. The 3D steady Navier–Stokes equations were solved by using the cell center finite volume method with a second order upwind scheme and a k−ε turbulence model. In addition, the wind energy dissipation model, derived from energy balance and Betz’s law, was added to the Navier–Stokes equations’ source term. The simulation results indicate that the wind speed distribution in the wake region contains significant information regarding multiple wind turbine faults. A feature selection algorithm specifically designed for the analysis of wind flow was proposed to reduce the number of features. This algorithm proved to have better performance than fuzzy entropy measures and recursive feature elimination methods under a limited number of features. As a result, faults in the wind turbine array could be detected and identified by machine learning algorithms.

scholarly journals 2D-CFD Analyses of Flow Controlling Plates on Gable Roof Geometry Cross-Sections for Light Air to Strong Breeze Wind Speed Classifications-an Unsteady RANS Approach

2020 ◽  
pp. 1-18
Author(s):  
Kasra Amini ◽  
Alireza Mani
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Flow Field ◽  
Cross Sections ◽  
Bluff Body ◽  
Stokes Equations ◽  
Convective Heat Transfer Coefficient ◽  
Field Analysis ◽  
Navier Stokes ◽  
Gable Roof

The flow field analysis has been numerically performed on the effectiveness of a flow control mechanism called the Flow Controlling Plate (FCP) on buildings. For this purpose, the gable roof geometry has been considered as a common urban element in the western residential architecture. As the justification step towards the functionality of the concept of FCPs, the 2D numerical investigation of the flow field under the realistic assumptions of atmospheric boundary layer profiles for the spectrum ranging from the so-called light air to strong breeze wind speed classifications have been performed. The CFD (Computational Fluid Dynamics) field calculations have been conveyed as an unsteady case for the flow around a bluff body, using RANS (Reynolds Average Navier-Stokes) averaging methods targeting a solution of Navier-Stokes equations of the fluid flow. The results have proven the hypotheses of the contribution of the FCPs on preventing the flow separation on a partial region of the surface and improving the boundary layer development on the rest of the gable roof facades, which have led to a drastic reduction in the convective heat transfer coefficient as well as the drag force exerted on the roof

scholarly journals Unshielded precipitation gauge collection efficiency with wind speed and hydrometeor fall velocity. Part I: modelling results

2020 ◽  
Author(s):  
Jeffery Hoover ◽  
Pierre E. Sullivan ◽  
Paul I. Joe ◽  
Michael E. Earle
Keyword(s):  
Wind Speed ◽  
Collection Efficiency ◽  
Navier Stokes ◽  
Lagrangian Analysis ◽  
Fall Velocity ◽  
Empirical Expression ◽  
Wind Speeds ◽  
Wet Snow ◽  
Precipitation Type ◽  
Precipitation Gauge

Abstract. A new method for assessing collection efficiency using wind speed and hydrometeor fall velocity is presented for the unshielded Geonor T-200B3 precipitation gauge based on computational fluid dynamics results. Time-averaged Navier–Stokes simulations with a k–e turbulence model were used to determine the airflow around the gauge for 0 to 10 m s−1 wind speeds. Hydrometeor trajectories and collection efficiencies were determined using Lagrangian analysis for spherical 10 hydrometeor fall velocities between 0.25 to 10 m s−1 for rain (0.01–3.9 mm diameter), wet snow (0.2–21 mm diameter), dry snow (0.2–7.1 mm diameter), and ice pellets (1.5–4.3 mm diameter). The model results demonstrate that gauge collection efficiency strongly depends on both wind speed and hydrometeor fall velocity. Collection efficiency differences for identical hydrometeor fall velocities are within 0.05 for wind speeds less than 4 m s−1, despite differences in hydrometeor type, diameter, density, and mass. An empirical expression for collection efficiency with dependence on wind speed and fall velocity is 15 presented based on the numerical results, giving a RMSE of 0.03 for dry snow, wet snow, and rain, for wind speeds between 0 and 10 m s−1. The use of fall velocity captures differences in collection efficiency due to different hydrometeor types and sizes, and can be broadly applied even where the precipitation type may be unknown or uncertain. Results are compared to previous models and good model agreement with experimental results is demonstrated in Part II.

Parallel Numerical Prediction of Pulverized Coal Particle Flow in Bifurcator-Type Flow Splitters

2003 ◽  
Vol 125 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Th. Frank ◽  
H. Schneider ◽  
K. Bernert ◽  
K. Pachler
Keyword(s):  
Numerical Simulation ◽  
Gas Flow ◽  
Stokes Equations ◽  
Decomposition Methods ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Numerical Effort ◽  
Tracking Model

This paper deals with the numerical simulation of two-phase flows based on the solution of the Navier-Stokes equations with a k−ε turbulence model for the gas phase and a particle tracking model of the disperse phase fulfilling the framework of the Eulerian-Lagrangian (PSI-cell) approach. The numerical procedures for the two phases are based on multigrid and domain decomposition methods applied to a block-structured grid. Due to the enormous numerical effort of such flow simulations the entire solving procedure has been parallelized for computers of MIMD architecture. The paper gives a short description of the applied and developed numerical methods. Furthermore the numerical simulation of a particle laden gas flow through a flow splitter from the area of power engineering is presented as an example for a real world application of the numerical approach.

Inertial Impaction-Dominated Diesel Particle Collection in Filters With Rectangular Fibers

2001 ◽  
Author(s):  
S. Chen ◽  
C. S. Cheung ◽  
C. K. Chan ◽  
C. Zhu
Keyword(s):  
Stokes Equations ◽  
Collection Efficiency ◽  
Low Cost ◽  
Particulate Filter ◽  
Navier Stokes ◽  
Particulate Emission ◽  
Navier Stokes Equations ◽  
Inertial Impaction ◽  
Fiber Aspect Ratio ◽  
Two Dimensional Flow

Abstract For the control of particulate emission from diesel engines, particulate filter is of great importance. Fibrous filter is one of the most common filters due to its simplicity in structure and low cost in manufacturing. In this paper, filters with rectangular fibers are studied numerically, in which the filter is simulated as a staggered array of parallel rectangular fibers placed transverse to the flow. Two-dimensional flow field is obtained by solving the Navier-Stokes equations with the finite volume method Particle trajectories are then calculated by solving the corresponding Lagrangian equation of motion to obtain the collection efficiency of filters. The simulation considers particle capture mechanisms of interception and inertial impaction. The effects of fiber aspect ratio, filter packing density, particulate size on the collection efficiency of a rectangular fiber are also numerically determined.

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