Investigation on the function of double tipping bucket for improvement of rainfall measurement

2020 ◽  
Author(s):  
Cai Zhao ◽  
Liu Jiufu ◽  
Liu Hongwei ◽  
Liao Aimin ◽  
Liao Minhan
Keyword(s):  
Rainfall Intensity ◽  
Fluid Model ◽  
Fluid Dynamic ◽  
Systematic Errors ◽  
Rain Gauge ◽  
Water Volume ◽  
Dynamic Simulations ◽  
Mesh Method ◽  
Volume Of Fluid Model ◽  
Simulation Results

<p>The double-tipping bucket rain gauge (SL3-1) is widely used in meteorological stations to minimize the systematic errors by the influence of rainfall intensity on TBRs in China. With two tipping buckets, the upper tipping bucket turns over and injects rainwater into the converging funnel, and the lower tipping bucket can record the rainfall. In this study, CFD (computational fluid dynamic) simulations and experiments were performed to investigate the function of the double tipping bucket for TBRs in different rainfall intensity. In simulation, the volume-of-fluid model and Reynolds-averaged Navier–Stokes realizable k-ε model and dynamic mesh method were used. In experiments, electric balances, with accuracy of 0.001 g, were used to determine the water volume of the upper tipping bucket outflow. It shows that, with a converging funnel, natural precipitation is uniformed at a certain intensity around 1.9mm/min to control the rainwater outflow into blow tipping bucket to measure rainfall and reduce systematic errors caused by different precipitation intensities. Experimental results demonstrate that the outflow curve of the upper tipping bucket has high correspond with simulation results in tipping process. These results can provide knowledge of advantages of double tipping bucket rain gauge in rainfall measurement and improve the structure designs of double tipping bucket for TBRs and obtain more accurate rainfall data.</p>

The Effect of Track-Seeking Motion on Off-Track Vibrations of the Head Gimbal Assembly in HDDs

2017 ◽  
Author(s):  
Guoqing Zhang ◽  
Hui Li ◽  
Shengnan Shen ◽  
Tan Trinh ◽  
Frank E. Talke ◽  
...  
Keyword(s):  
Fluid Dynamic ◽  
Angular Acceleration ◽  
Sinusoidal Wave ◽  
Interaction Method ◽  
Square Wave ◽  
Structure Interaction ◽  
Head Gimbal Assembly ◽  
Head Positioning ◽  
Mesh Method ◽  
Simulation Results

The effect of track-seeking on off-track residual vibrations of the head-gimbal assembly (HGA) is investigated for air and helium environments using the so-called “fluid dynamic mesh” method and the “fluid-structure interaction” method. Three different angular acceleration profiles (square wave, triangular wave and sinusoidal wave) are investigated as a function of seek time (10 ms and 5 ms). Results show that smoothening of sharp transitions of the seek profile improves the performance of off-track residual vibrations during track-following and shortens the track-following time of the head positioning servo system. In addition, the effect of lateral flow (windage) on off-track residual vibrations during track-following must be considered for a square wave angular acceleration profile. Simulation results show that helium improves the track-following accuracy compared to air due to the lower windage forces acting on the HGA. We observe that the sinusoidal wave angular acceleration performs best among the three angular acceleration profiles investigated. Furthermore, seek time is found to have only a small effect on off-track residual vibrations during track-following.

scholarly journals Numerical and Experimental Investigation on the Function of Siphons for Tipping-Bucket Rain Gauges

2020 ◽  
Vol 37 (7) ◽  
pp. 1189-1201 ◽  
Author(s):  
Zhao Cai ◽  
Jiufu Liu ◽  
Aimin Liao ◽  
Xuegang Li ◽  
Minhan Liao
Keyword(s):  
Structural Design ◽  
Laboratory Experiments ◽  
Rainfall Intensity ◽  
Outer Part ◽  
Rain Gauge ◽  
Cfd Simulations ◽  
Rain Gauges ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Two Parameters

AbstractSiphons can effectively reduce the influence of rainfall intensity on the mechanical bias of tipping-bucket rain gauges (TBRs). To identify the function of siphons for TBRs, this study investigated three types of siphons: a Texas Electronics (TE) siphon, a RIMCO (RIM) siphon, and a Sutron siphon, with both computational fluid dynamics (CFD) simulations and laboratory experiments. To provide better structural designs, further simulations were conducted to adjust two parameters of the siphons: d, the distance from the cap to the outer part, and w, the distance from the main part to the cap part. The simulation results reveal that the most significant advantage of a siphon over a rain gauge collector is to provide stable outflow for the tipping bucket. The stable outflow rates were around 1.5 g s−1 (TE) and 1.55 g s−1 (RIM), while the Sutron siphon increased from 1.75 to 2.45 g s−1. The ratio of stable outflow time to a complete siphon event was 69% (TE), 81% (Sutron), and 83% (RIM). In experiments with rainfall intensity higher than 1 mm min−1, the RIM and TE siphons showed oscillations in the outflow during consecutive siphon events, whereas the Sutron siphon was relatively stable. Further simulations showed that the recommended d and w for the TE siphon are 2.5 and 1.1 mm, respectively, while the recommendations for the RIM siphon are d = 2.5 mm and w = 0.9 mm. The manufacturer’s specifications for d and w are best for the Sutron siphon. These results help to understand the functionality of siphons for TBRs, and benefit the structural design of common siphons.

scholarly journals Application of Correction Procedures for Some Systematic Measurement Errors to Rainfall Intensity Data of a Rain Gauge in Budapest

2021 ◽  
Author(s):  
Tibor Rácz
Keyword(s):  
Measurement Errors ◽  
Rainfall Intensity ◽  
Measurement Data ◽  
Sampling Period ◽  
Systematic Errors ◽  
Rain Gauge ◽  
Data Series ◽  
Idf Curves ◽  
Precipitation Gauge

The rainfall intensity measurement has a 150 years long history. In the first period of data recordings, the siphoned recording precipitation gauge (pluviographs), or siphoned rainfall writers (SRW), later, the tipping bucket gauges (TBG) were widely used. The systematic errors of these instruments resulted in lower intensity values for long periods. These errors were compensated sporadically. Most of the inaccurate data can be found in the high rainfall intensity range. Some of these data can be found in extracted, aggregated versions only, and the original measurement data is no longer available. These kinds of inherited systematic errors can be corrected. The fixing of siphoning error of SRWs and the supplementary correction of long sampling period data of TBG devices can be a suitable method for the elimination of these issues. In this paper, the application of these two methods is shown in a case study to point out the magnitude and effect of these errors on the IDF curves. The case study on the use of the before-mentioned correction procedures is performed on the rainfall data of the Budapest-Belterület (Budapest City) rainfall station, using data series spanning 105 years. These corrections show that the earlier IDF curves can show 5–10% lower intensities, mainly in the short and low return frequency rainfalls. The result of these kinds of corrections can be significant for the climate change investigations or in the re-evaluation of the elder IDF curves.

scholarly journals Hydrodynamic studies on liquid-liquid two phase flow separation in microchannel by computational fluid dynamic modelling

2021 ◽  
Vol 4 (2) ◽  
pp. first
Author(s):  
Chue Cui Ting ◽  
Afiq Mohd Laziz ◽  
Khoa Dang Dang Bui ◽  
Ngoc Thi Nhu Nguyen ◽  
Pha Ngoc Bui ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Fluid Model ◽  
Volume Of Fluid ◽  
Rapid Expansion ◽  
Separation Performance ◽  
Microfluidic Systems ◽  
Two Phase ◽  
Volume Of Fluid Model ◽  
Simulation Results ◽  
Methanol System

Microfluidic systems undergo rapid expansion of its application in different industries over the few decades as its surface tension-dominated property provides better mixing and improves mass transfer between two immiscible liquids. Synthesis of biodiesel via transesterification of vegetable oil and methanol in microfluidic systems by droplet flow requires separation of the products after the reaction occurred. The separation technique for multiphase fluid flow in the microfluidic system is different from the macro-system, as the gravitational force is overtaken by surface force. To understand these phenomena completely, a study on the hydrodynamic characteristics of two-phase oil-methanol system in microchannel was carried out. A multiphase Volume of Fluid model was developed to predict the fluid flow in the microchannel. An inline separator design was proposed along with its variable to obtain effective separation for the oil-methanol system. The separation performance was evaluated based on the amount of oil recovered and its purity. The capability of the developed model has been validated through a comparison of simulation results with published experiment. It was predicted that the purity of recovered oil was increased by more than 46% when the design with side openings arranged at both sides of the microchannel. The highest percentage recovery of oil from the mixture was simulated at 91.3% by adding the number of side openings to ensure the maximum recovery. The oil that was separated by the inline separator was predicted to be at 100% purity, which indicates that no methanol contamination throughout the separation process. The purity of the separated product can be increased by manipulating the pressure drop across the side openings. Hence, it can be concluded that the separation in a large diameter microchannel system is possible and methodology can be tuned to achieve the separation goal. Finally, the simulation results showed that the present volume of fluid model had a good agreement with the published experiment.

scholarly journals Parameterization of the Collection Efficiency of a Cylindrical Catching-Type Rain Gauge Based on Rainfall Intensity

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3431
Author(s):  
Arianna Cauteruccio ◽  
Luca G. Lanza
Keyword(s):  
Field Experiments ◽  
Rainfall Intensity ◽  
Collection Efficiency ◽  
Fluid Dynamic ◽  
Rain Gauge ◽  
Representative Specimen ◽  
Measurement Instruments ◽  
Widespread Application ◽  
Rain Gauges ◽  
Tracking Model

Despite the numerous contributions available in the literature about the wind-induced bias of rainfall intensity measurements, adjustments based on collection efficiency curves are rarely applied operationally to rain records obtained from catching-type rain gauges. The many influencing variables involved and the variability of the results of field experiments do not facilitate the widespread application of adjustment algorithms. In this paper, a Lagrangian particle tracking model is applied to the results of computational fluid dynamic simulations of the airflow field surrounding a rain gauge to derive a simple formulation of the collection efficiency curves as a function of wind speed. A new parameterization of the influence of rainfall intensity is proposed. The methodology was applied to a cylindrical gauge, which has the typical outer shape of tipping-bucket rain gauges, as a representative specimen of most operational measurement instruments. The wind velocity is the only ancillary variable required to calculate the adjustment, together with the measured rainfall intensity. Since wind is commonly measured by operational weather stations, its use adds no relevant burden to the cost of meteo-hydrological networks.

Research on Swirl-Core Nozzle with Adjustable Spray Angle Based on Vortex Theory

2010 ◽  
Vol 37-38 ◽  
pp. 1082-1087
Author(s):  
An Hong Bao ◽  
Ming Jin Yang ◽  
Xing Dai ◽  
Zhen Yu Qiu ◽  
Shou Yong Xie
Keyword(s):  
Fluid Model ◽  
Fluid Dynamic ◽  
Structural Parameters ◽  
Helix Angle ◽  
Spray Angle ◽  
Spiral Groove ◽  
Swirl Chamber ◽  
Vortex Theory ◽  
Volume Of Fluid Model ◽  
Nozzle Opening

According to Vortex Theory, the fluid flow in a swirl-core nozzle was analyzed, and an equation of spray angle was presented. The fluid in this nozzle was simulated by Volume of Fluid Model through CFD. The fluid dynamic simulation results show that diameters of nozzle opening and swirl chamber, area of spiral groove, and helix angle of the spiral groove affect the spray angle. There are optimum structural parameters for a swirl-core nozzle, and the spray angle can be adjusted by changing the depth of the swirl chamber with fixed structural parameters of the nozzle.

scholarly journals Computational modeling of gas mixture dispersion in a dynamic setup – 2d and 3d numerical approach

2018 ◽  
Vol 44 ◽  
pp. 00146 ◽  
Author(s):  
Andrzej Polanczyk ◽  
Zdzisław Salamonowicz
Keyword(s):  
Fluid Model ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Chlorine Concentration ◽  
Gas Mixture ◽  
Circular Profile ◽  
Volume Of Fluid Model ◽  
Two Stages ◽  
2D And 3D

The aim of the study was to prepare a mathematical model of gas mixture dispersion with the use of Computational Fluid Dynamic (CFD) technique. Three dimensional chlorine dispersion in a dynamic setup with the use of Volume of Fluid model (VOD) model was applied. The area of investigation was equal to 0.1km2 and the high of the mathematical domain was equal to 50m. Atmosphere was considered in two stages: as one direction of wind flow and no wind. Comparison of constant and dynamic conditions indicated high impact of wind. For the windless case circular profile of chlorine concentration around dispersion source was observed. While, for the wind application the main chlorine concentration moved ahead the source of dispersion.

scholarly journals Measuring Hydrometeors Using a Precipitation Microphysical Characteristics Sensor: Sampling Effect of Different Bin Sizes on Drop Size Distribution Parameters

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xichuan Liu ◽  
Taichang Gao ◽  
Yuntao Hu ◽  
Xiaojian Shu
Keyword(s):  
Drop Size ◽  
Rain Rate ◽  
Monte Carlo Model ◽  
Rain Gauge ◽  
Sampling Schemes ◽  
Distribution Parameters ◽  
Optimum Sampling ◽  
Simulation Results ◽  
The Impact ◽  
Good Agreement

In order to improve the measurement of precipitation microphysical characteristics sensor (PMCS), the sampling process of raindrops by PMCS based on a particle-by-particle Monte-Carlo model was simulated to discuss the effect of different bin sizes on DSD measurement, and the optimum sampling bin sizes for PMCS were proposed based on the simulation results. The simulation results of five sampling schemes of bin sizes in four rain-rate categories show that the raw capture DSD has a significant fluctuation variation influenced by the capture probability, whereas the appropriate sampling bin size and width can reduce the impact of variation of raindrop number on DSD shape. A field measurement of a PMCS, an OTT PARSIVEL disdrometer, and a tipping bucket rain Gauge shows that the rain-rate and rainfall accumulations have good consistencies between PMCS, OTT, and Gauge; the DSD obtained by PMCS and OTT has a good agreement; the probability of N0, μ, and Λ shows that there is a good agreement between the Gamma parameters of PMCS and OTT; the fitted μ-Λ and Z-R relationship measured by PMCS is close to that measured by OTT, which validates the performance of PMCS on rain-rate, rainfall accumulation, and DSD related parameters.

Towards real-time fire data synthesis using numerical simulations

2021 ◽  
pp. 073490412199344
Author(s):  
Wolfram Jahn ◽  
Frane Sazunic ◽  
Carlos Sing-Long
Keyword(s):  
Real Time ◽  
Computational Fluid Dynamic ◽  
Dynamic Models ◽  
Fluid Dynamic ◽  
Near Field ◽  
Computing Time ◽  
Temperature Correction ◽  
Dynamic Simulations ◽  
Conservation Of Energy ◽  
Fire Scenarios

Synthesising data from fire scenarios using fire simulations requires iterative running of these simulations. For real-time synthesising, faster-than-real-time simulations are thus necessary. In this article, different model types are assessed according to their complexity to determine the trade-off between the accuracy of the output and the required computing time. A threshold grid size for real-time computational fluid dynamic simulations is identified, and the implications of simplifying existing field fire models by turning off sub-models are assessed. In addition, a temperature correction for two zone models based on the conservation of energy of the hot layer is introduced, to account for spatial variations of temperature in the near field of the fire. The main conclusions are that real-time fire simulations with spatial resolution are possible and that it is not necessary to solve all fine-scale physics to reproduce temperature measurements accurately. There remains, however, a gap in performance between computational fluid dynamic models and zone models that must be explored to achieve faster-than-real-time fire simulations.

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