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 Numerical Simulation and Optimization of Wind Effects of Porous Parapets on Low-Rise Buildings with Flat Roofs

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Ye Qiu ◽  
Bingbing San ◽  
Youyi Zhao
Keyword(s):  
Fluid Dynamics ◽  
Momentum Equation ◽  
Cfd Simulations ◽  
Simulation And Optimization ◽  
Wind Tunnel Data ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Optimization Methodology ◽  
Conical Vortices ◽  
Flat Roofs

This paper presents a procedure to optimize the porosity of parapets to improve the aerodynamic behavior of low-rise buildings with flat roofs, by coupling an optimization algorithm and computational fluid dynamics (CFD) simulations. The performance of solid parapets to decrease the wind suctions on flat roofs induced by conical vortices was firstly studied, based on four turbulence closure models (standard k-ε, RNG k-ε, SST k-ω, and RSM). The simulation results were validated by comparing with the wind tunnel data. Additionally, the porous parapet was treated as a momentum sink in the governing momentum equation, and the RSM turbulence model was employed. As a result, six optimization studies focusing on the highest mean suction minimization that consider parapet height were presented. The aim of this paper is to search for the best performing porosity through an automatic CFD-based optimization methodology. At low relative heights (hp/H = 0.01∼0.05, hp is the parapet height, and H is the roof height), the porous parapet with optimal porosity in between 38.2% and 52.3% seems to be more effective than solid parapets in attenuating high corner suctions generated by conical vortices; however, the solid parapet gives the best performance in the reduction of wind suctions when hp/H ≥ 0.07.

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>

scholarly journals Rainfall estimation using moving cars as rain gauges – laboratory experiments

2013 ◽  
Vol 17 (11) ◽  
pp. 4701-4712 ◽  
Author(s):  
E. Rabiei ◽  
U. Haberlandt ◽  
M. Sester ◽  
D. Fitzner
Keyword(s):  
Optical Sensors ◽  
Laboratory Experiments ◽  
Rainfall Intensity ◽  
Computer Experiments ◽  
Rainfall Estimation ◽  
Time Step ◽  
Radar Rainfall ◽  
Rain Gauges ◽  
Wide Range ◽  
Measurement Devices

Abstract. The spatial assessment of short time-step precipitation is a challenging task. Low density of observation networks, as well as the bias in radar rainfall estimation motivated the new idea of exploiting cars as moving rain gauges with windshield wipers or optical sensors as measurement devices. In a preliminary study, this idea has been tested with computer experiments (Haberlandt and Sester, 2010). The results have shown that a high number of possibly inaccurate measurement devices (moving cars) provide more reliable areal rainfall estimations than a lower number of precise measurement devices (stationary gauges). Instead of assuming a relationship between wiper frequency (W) and rainfall intensity (R) with an arbitrary error, the main objective of this study is to derive valid W–R relationships between sensor readings and rainfall intensity by laboratory experiments. Sensor readings involve the wiper speed, as well as optical sensors which can be placed on cars and are usually made for automating wiper activities. A rain simulator with the capability of producing a wide range of rainfall intensities is designed and constructed. The wiper speed and two optical sensors are used in the laboratory to measure rainfall intensities, and compare it with tipping bucket readings as reference. Furthermore, the effect of the car speed on the estimation of rainfall using a car speed simulator device is investigated. The results show that the sensor readings, which are observed from manual wiper speed adjustment according to the front visibility, can be considered as a strong indicator for rainfall intensity, while the automatic wiper adjustment show weaker performance. Also the sensor readings from optical sensors showed promising results toward measuring rainfall rate. It is observed that the car speed has a significant effect on the rainfall measurement. This effect is highly dependent on the rain type as well as the windshield angle.

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.

Numerical Simulation of Flow Around a Generic Pickup With ISIS-CFD

2010 ◽  
Author(s):  
Emmanuel Guilmineau
Keyword(s):  
Reynolds Stress Model ◽  
Stress Model ◽  
Detached Eddy Simulation ◽  
Cfd Simulations ◽  
Flow Solver ◽  
Pickup Truck ◽  
Eddy Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Algebraic Reynolds Stress Model

Computational Fluid Dynamics (CFD) is used to simulate the flow over a pickup truck. The flow solver used is ISIS-CFD developed by the CFD Department of the Fluid Mechanics Laboratory of Ecole Centrale de Nantes. CFD simulations are carried out with the Explicit Algebraic Reynolds Stress Model (EARSM) turbulence model and the Detached Eddy Simulation (DES). The focus of the simulation is to assess the capabilities of ISIS-CFD for vehicle aerodynamic development for pickup trucks. Detailed comparisons are made between the CFD simulations and the existing experiments for a generic pickup truck. The comparisons between the simulation results and the time-averaged measurements reveals that the CFD calculations are able to track the flow trends.

scholarly journals Certified accuracy of rainfall data as a standard requirement in scientific investigations

2008 ◽  
Vol 16 ◽  
pp. 43-48 ◽  
Author(s):  
L. G. Lanza ◽  
L. Stagi
Keyword(s):  
Rainfall Intensity ◽  
Rain Gauge ◽  
Standard Requirement ◽  
Accuracy Requirement ◽  
Rain Gauges ◽  
Scientific Investigations ◽  
Intensity Measurements ◽  
Meteorological Observations ◽  
Instrument Intercomparison ◽  
Rain Data

Abstract. This paper elaborates on the rationale behind the proposed standard limits for the accuracy of rainfall intensity measurements obtained from tipping-bucket and other types of rain gauges. Indeed, based on experimental results obtained in the course of international instrument Intercomparison initiatives and specific laboratory tests, it is shown here that the accuracy of operational rain gauges can be reduced to the limits of ±1% after proper calibration and correction. This figure is proposed as a standard accuracy requirement for the use of rain data in scientific investigations. This limit is also proposed as the reference accuracy for operational rain gauge networks in order to comply with quality assurance systems in meteorological observations.

scholarly journals Investigation of Tipping-Bucket Rain Gauges Using Digital Photographic Technology

2020 ◽  
Vol 37 (2) ◽  
pp. 327-339 ◽  
Author(s):  
Minhan Liao ◽  
Jiufu Liu ◽  
Aimin Liao ◽  
Zhao Cai ◽  
Yixin Huang ◽  
...  
Keyword(s):  
Traditional Method ◽  
Rainfall Intensity ◽  
Rain Gauge ◽  
Recording Device ◽  
Calculation Formula ◽  
Rain Intensity ◽  
Primary Interest ◽  
Rain Gauges ◽  
Variation Characteristics ◽  
New Formula

AbstractWhen studying the tipping-bucket rain gauge (TBR), it is rather difficult to make an objective and sophisticated measurement of the duration of bucket rotation. From the perspective of digital photographic technology, however, the problem can be easily solved. The primary interest of this research has been to use digital photographic technology to study the TBR under laboratory conditions. In this study, the interframe difference algorithm and a camera recording device were used. Based on three types of JDZ TBRs, the time variation characteristics of bucket rotation were obtained. The time from the beginning of a tip to the time that the bucket is horizontal T1 and the time for a complete tip T2 were analyzed in detail. The results showed that T1 and T2 were functions of rainfall intensity, and T1 and T2 decrease as the rain intensity increases significantly (P < 0.001). Moreover, excellent evidence shows that the averages of T1 and T2 were positively correlated with bucket mass. It took more time for the bucket to tip as the mass of the bucket increased. Furthermore, the error of each TBR was calculated by the new proposed error calculation formula, and the new method was compared with the traditional method. The results from the two methods were very close, which demonstrates the correctness and feasibility of the new formula. However, the traditional calibration cannot acquire the variation characteristics of the tipping time, but the proposed approach can achieve this.

scholarly journals Hemodynamic Investigation of the Effectiveness of a Two Overlapping Flow Diverter Configuration for Cerebral Aneurysm Treatment

2021 ◽  
Vol 8 (10) ◽  
pp. 143
Author(s):  
Yuya Uchiyama ◽  
Soichiro Fujimura ◽  
Hiroyuki Takao ◽  
Takashi Suzuki ◽  
Motoharu Hayakawa ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Flow Diverter ◽  
Cfd Simulations ◽  
Qualitative And Quantitative ◽  
Pressure Loss Coefficient ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Wide Neck ◽  
Flow Diverters

Flow diverters (FDs) are widely employed as endovascular treatment devices for large or wide-neck cerebral aneurysms. Occasionally, overlapped FDs are deployed to enhance the flow diversion effect. In this study, we investigated the hemodynamics of overlapping FDs via computational fluid dynamics (CFD) simulations. We reproduced the arterial geometry of a patient who had experienced the deployment of two overlapping FDs. We utilized two stent patterns, namely the patterns for one FD and two overlapping FDs. We calculated the velocity, mass flow rate, wall shear stress, and pressure loss coefficient as well as their change rates for each pattern relative to the no-FD pattern results. The CFD simulation results indicated that the characteristics of the blood flow inside the aneurysm were minimally affected by the deployment of a single FD; in contrast, the overlapping FD pattern results revealed significant changes in the flow. Further, the velocity at an inspection plane within the aneurysm sac decreased by up to 92.2% and 31.0% in the cases of the overlapping and single FD patterns, respectively, relative to the no-FD pattern. The simulations successfully reproduced the hemodynamics, and the qualitative and quantitative investigations are meaningful with regard to the clinical outcomes of overlapped FD deployment.

scholarly journals Preliminary Evaluation of the HOBO Data Logging Rain Gauge at the Chuzhou Hydrological Experiment Station, China

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Zehui Zhou ◽  
Bin Yong ◽  
Jiufu Liu ◽  
Aimin Liao ◽  
Niu Wang ◽  
...  
Keyword(s):  
Rainfall Intensity ◽  
Rain Gauge ◽  
Maximum Deviation ◽  
Preliminary Evaluation ◽  
Data Logging ◽  
Rainfall Events ◽  
Rain Gauges ◽  
Experiment Station ◽  
Independent Power Supply ◽  
Hourly Rainfall

As a tipping bucket rain gauge, the HOBO Data Logging Rain Gauge RG3-M (RG3-M) has been widely used for the field precipitation observation owing to its superiority of independent power supply by a small portable battery. To quantify the measurement accuracy of the RG3-M gauge, a standard Manual Gauge (MG) and eight other models of tipping bucket rain gauges were installed at the Chuzhou hydrological experiment station of China. In this study, we first compared and investigated the accumulated mounts of 18 rainfall events of two RG3-M gauges benchmarked by the standard MG. Then, five typical rainfall events were chosen to further analyse the observed accuracy of the RG3-M gauge for different rainfall intensities at hourly temporal scale. Finally, the impacts of wind speed and rainfall intensity on the precipitation measurements of the RG3-M gauge were preliminarily explored. Results indicate that the RG3-M gauge measurement generally underestimates rainfall approximately −4% against the standard MG observation, but the maximum deviation even reaches −12.87%. In terms of the hourly rainfall process, the reliable measurement scope of the RG3-M gauge is ranging from 1.5 to 3 mm/h; however, it should be noted that the underestimation is rather significant at the higher rainfall rates (>6 mm/h). Last, it was found that rainfall intensity is a nonnegligible factor for influencing the measurement of the RG3-M gauge. But the windy effect seems to be insignificant in our experiments, which might be attributed to the similar exposure of the compared gauges.

Investigation of tipping bucket rain gauges using digital photographic technology

2020 ◽  
Author(s):  
Minhan Liao ◽  
Jiufu Liu ◽  
Aimin Liao
Keyword(s):  
Traditional Method ◽  
Rainfall Intensity ◽  
Rain Gauge ◽  
Recording Device ◽  
Calculation Formula ◽  
Rain Intensity ◽  
Primary Interest ◽  
Rain Gauges ◽  
Variation Characteristics ◽  
New Formula

&lt;p&gt;When studying the tipping bucket rain gauge (TBR), it is rather difficult to make an objective and sophisticated measurement of the duration of bucket rotation. From the perspective of digital photographic technology, however, the problem can be easily solved. The primary interest of this research has been to use digital photographic technology to study the TBR under laboratory conditions. In this study, the interframe difference algorithm and a camera recording device were used. Based on three types of JDZ TBRs, the time variation characteristics of bucket rotation were obtained. The time from the beginning of a tip to the time that the bucket is horizontal (T&lt;sub&gt;1&lt;/sub&gt;) and the time for a complete tip (T&lt;sub&gt;2&lt;/sub&gt;) were analyzed in detail. The results showed that T&lt;sub&gt;1&lt;/sub&gt; and T&lt;sub&gt;2&lt;/sub&gt; were functions of rainfall intensity, and T&lt;sub&gt;1&lt;/sub&gt;, T&lt;sub&gt;2&lt;/sub&gt; decrease as the rain intensity increases significantly (P&lt;0.001). Moreover, excellent evidence shows that the averages of T&lt;sub&gt;1&lt;/sub&gt; and T&lt;sub&gt;2&lt;/sub&gt; were positively correlated with bucket mass. It took more time for the bucket to tip as the mass of the bucket increased. Furthermore, the error of each TBR was calculated by the new proposed error calculation formula, and the new method was compared with the traditional method. The results from the two methods were very close, which demonstrates the correctness and feasibility of the new formula. However, the traditional calibration cannot acquire the variation characteristics of the tipping time, but the proposed approach can achieve this.&lt;/p&gt;

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