scholarly journals Measurement and computation of kinetic energy of simulated rainfall in comparison with natural rainfall.

2018 ◽  
Author(s):  
Petrů Jan ◽  
Kalibová Jana
Keyword(s):  
Kinetic Energy ◽  
Drop Size ◽  
Rainfall Intensity ◽  
Soil Aggregates ◽  
Meteorological Parameter ◽  
Simulated Rainfall ◽  
Fall Velocity ◽  
Rainfall Simulator ◽  
Rainfall Characteristics ◽  
Natural Rainfall

Rainfall characteristics such as total amount and rainfall intensity (I) are important inputs in calculating the kinetic energy (KE) of rainfall. Although KE is a crucial indicator of the raindrop potential to disrupt soil aggregates, it is not a routinely measured meteorological parameter. Therefore, KE is derived from easily accessible variables, such as I, in empirical laws. The present study examines whether the equations which had been derived to calculate KE of natural rainfall are suitable for the calculation of KE of simulated rainfall. During the experiment presented in this paper, the measurement of rainfall characteristics was carried out under laboratory conditions using a rainfall simulator. In total, 90 measurements were performed and evaluated to describe the rainfall intensity, drop size distribution and velocity of rain drops using the Thies laser disdrometer. The duration of each measurement of rainfall event was 5 minutes. Drop size and fall velocity were used to calculate KE and to derive a new equation of time-specific kinetic energy (KE<sub>time</sub> – I). When comparing the newly derived equation for KE of simulated rainfall with the six most commonly used equations for KE<sub>time</sub> – I of natural rainfall, KE of simulated rainfall was discovered to be underestimated. The higher the rainfall intensity, the higher the rate of underestimation. KE of natural rainfall derived from theoretical equations exceeded KE of simulated rainfall by 53–83% for I = 30 mm/h and by 119–275% for I = 60 mm/h. The underestimation of KE of simulated rainfall is probably caused by smaller drops formed by the rainfall simulator at higher intensities (94% of all drops were smaller than 1 mm), which is not typical of natural rainfall.  

scholarly journals Measurement and computation of kinetic energy of simulated rainfall in comparison with natural rainfall

2018 ◽  
Vol 13 (No. 4) ◽  
pp. 226-233 ◽  
Author(s):  
Petrů Jan ◽  
Kalibová Jana
Keyword(s):  
Kinetic Energy ◽  
Drop Size ◽  
Rainfall Intensity ◽  
Soil Aggregates ◽  
Meteorological Parameter ◽  
Simulated Rainfall ◽  
Fall Velocity ◽  
Rainfall Simulator ◽  
Rainfall Characteristics ◽  
Natural Rainfall

Rainfall characteristics such as total amount and rainfall intensity (I) are important inputs in calculating the kinetic energy (KE) of rainfall. Although KE is a crucial indicator of the raindrop potential to disrupt soil aggregates, it is not a routinely measured meteorological parameter. Therefore, KE is derived from easily accessible variables, such as I, in empirical laws. The present study examines whether the equations which had been derived to calculate KE of natural rainfall are suitable for the calculation of KE of simulated rainfall. During the experiment presented in this paper, the measurement of rainfall characteristics was carried out under laboratory conditions using a rainfall simulator. In total, 90 measurements were performed and evaluated to describe the rainfall intensity, drop size distribution and velocity of rain drops using the Thies laser disdrometer. The duration of each measurement of rainfall event was 5 minutes. Drop size and fall velocity were used to calculate KE and to derive a new equation of time-specific kinetic energy (KE<sub>time</sub> – I). When comparing the newly derived equation for KE of simulated rainfall with the six most commonly used equations for KE<sub>time</sub> – I of natural rainfall, KE of simulated rainfall was discovered to be underestimated. The higher the rainfall intensity, the higher the rate of underestimation. KE of natural rainfall derived from theoretical equations exceeded KE of simulated rainfall by 53–83% for I = 30 mm/h and by 119–275% for I = 60 mm/h. The underestimation of KE of simulated rainfall is probably caused by smaller drops formed by the rainfall simulator at higher intensities (94% of all drops were smaller than 1 mm), which is not typical of natural rainfall.

scholarly journals Influence of drop size distribution and kinetic energy in precipitation modelling for laboratory rainfall simulators

2021 ◽  
Author(s):  
Harris Ramli ◽  
Siti Aimi Nadia Mohd Yusoff ◽  
Mastura Azmi ◽  
Nuridah Sabtu ◽  
Muhd Azril Hezmi
Keyword(s):  
Kinetic Energy ◽  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Scale Model ◽  
Simulated Rainfall ◽  
Rainfall Simulator ◽  
Natural Rainfall ◽  
Set Up ◽  
The Given

Abstract. It is difficult to define the hydrologic and hydraulic characteristics of rain for research purposes, especially when trying to replicate natural rainfall using artificial rain on a small laboratory scale model. The aim of this paper was to use a drip-type rainfall simulator to design, build, calibrate, and run a simulated rainfall. Rainfall intensities of 40, 60 and 80 mm/h were used to represent heavy rainfall events of 1-hour duration. Flour pellet methods were used to obtain the drop size distribution of the simulated rainfall. The results show that the average drop size for all investigated rainfall intensities ranges from 3.0–3.4 mm. The median value of the drop size distribution or known as D50 of simulated rainfall for 40, 60 and 80 mm/h are 3.4, 3.6, and 3.7 mm, respectively. Due to the comparatively low drop height (1.5 m), the terminal velocities monitored were between 63–75 % (8.45–8.65 m/s), which is lower than the value for natural rainfall with more than 90 % for terminal velocities. This condition also reduces rainfall kinetic energy of 25.88–28.51 J/m2mm compared to natural rainfall. This phenomenon is relatively common in portable rainfall simulators, representing the best exchange between all relevant rainfall parameters obtained with the given simulator set-up. Since the rainfall can be controlled, the erratic and unpredictable changeability of natural rainfall is eliminated. Emanating from the findings, drip-types rainfall simulator produces rainfall characteristics almost similar to natural rainfall-like characteristic is the main target.

scholarly journals Set-up and calibration of a portable small scale rainfall simulator for assessing soil erosion processes at interrill scale

2017 ◽  
Vol 43 (1) ◽  
pp. 63 ◽  
Author(s):  
J. J. Zemke
Keyword(s):  
Soil Erosion ◽  
Kinetic Energy ◽  
Rainfall Intensity ◽  
Small Scale ◽  
Rainfall Erosivity ◽  
Fall Velocity ◽  
Rainfall Simulator ◽  
Spatial Homogeneity ◽  
Erosion Processes ◽  
Natural Rainfall

A portable rainfall simulator was built for assessing runoff and soil erosion processes at interrill scale. Within this study, requirements and constraints of the rainfall simulator are identified and discussed. The focus lies on the calibration of the simulator with regard to spatial rainfall homogeneity, rainfall intensity, drop size, drop fall velocity and rainfall kinetic energy. These parameters were obtained using different methods including a Laser Precipitation Monitor. A detailed presentation of the operational characteristics is given. The presented rainfall simulator setup featured a rainfall intensity of 45.4 mm·h-1 with a spatial homogeneity of 80.4% based on a plot area of 0.64 m². Because of the comparatively low drop height (2 m), the diameter-dependent terminal fall velocity (1.87 m·s-1) was lower than benchmark values for natural rainfall. This conditioned also a reduced rainfall kinetic energy (4.6 J·m-2·mm-1) compared to natural rainfall with same intensity. These shortfalls, a common phenomenon concerning portable rainfall simulators, represented the best possible trade-off between all relevant rainfall parameters obtained with the given simulator setup. Field experiments proved that the rainfall erosivity was constant and replicable.

Splash erosion experiments with silt loam and loamy sand soil under simulated rainfall produced by two types of rainfall simulators

2020 ◽  
Author(s):  
Nives Zambon ◽  
Lisbeth Lolk Johannsen ◽  
Peter Strauss ◽  
Tomáš Dostál ◽  
David Zumr ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Loamy Sand ◽  
Silt Loam ◽  
Simulated Rainfall ◽  
Sand Soil ◽  
Rainfall Simulator ◽  
Rainfall Characteristics ◽  
Splash Erosion ◽  
Loamy Sand Soil ◽  
Soil Erosion By Water

&lt;p&gt;Soil erosion by water is globally the main soil degradation process which leaves serious consequences on agricultural land and water aquifers. Splash erosion is the initial stage of soil erosion by water, resulting from the destructive force of rain drops acting on soil surface aggregates. Splash erosion studies conducted in laboratories use rainfall simulators. They produce artificial rainfall which can vary according to type of the rainfall simulator. In this study the aim was to quantify the differences in splash erosion rates affected by rainfall produced by two different rainfall simulators on two silt loam and one loamy sand soil. Splash erosion was measured using modified Morgan splash cups and the rainfall simulators were equipped with four VeeJet or one FullJet nozzle. The soil samples placed under simulated rainfall were exposed to intensity range from 28 to 54 mm h&lt;sup&gt;-1&lt;/sup&gt; and from 35 to 81 mm h&lt;sup&gt;-1&lt;/sup&gt;, depending on the rainfall simulator. Rainfall characteristics such as drop size and velocity distribution were measured with an optical laser disdrometer Weather Sensor OTT Parsivel Version 1 (Parsivel) by OTT Messtechnik. Rainfall simulator with VeeJet nozzles produced smaller drops but higher drop velocity which resulted in higher kinetic energy per mm of rainfall compared to rainfall simulator with FullJet nozzles. For the same intensity rate measured kinetic energy under the rainfall simulator with VeeJet nozzles was 45% higher than rainfall kinetic energy from rainfall simulator with FullJet nozzles. Accordingly, the average splash erosion rate was 45 and 59% higher under the rainfall simulator with VeeJet nozzles for one silt loam and loamy sand soil, respectively. Splash erosion was found to be a linear or power function of the rainfall kinetic energy, depending on rainfall simulator. The obtained results highlight the sensitivity of the splash erosion process to rainfall characteristics produced by different rainfall simulators. The heterogeneity of rainfall characteristics between different types of rainfall simulators makes a direct comparison of results obtained from similar erosion studies difficult. Further experiments including comparison between more rainfall simulators could define influencing rainfall parameters on splash erosion under controlled laboratory conditions.&lt;/p&gt;

scholarly journals A Rainfall Simulator Used for Testing of Hydrological Performances of Micro-Detention Permeable Pavement

2018 ◽  
Vol 7 (3.18) ◽  
pp. 44 ◽  
Author(s):  
Norazlina Bateni ◽  
Sai Hin Lai ◽  
Frederik Josep Putuhena ◽  
Darrien Yau Seng Mah ◽  
Md Abdul Mannan
Keyword(s):  
Rainfall Intensity ◽  
Drainage System ◽  
Rainfall Simulator ◽  
Rainfall Characteristics ◽  
Permeable Pavement ◽  
Natural Rainfall ◽  
Spatial Uniformity ◽  
Free Drainage ◽  
Coefficient Of Uniformity ◽  
Raindrop Size

A rainfall simulator for laboratory experimentation is developed to test hydrological performances of micro-detention pond permeable pavement, MDPP. Rainfall characteristics consisting of rainfall intensity, spatial uniformity, raindrop size, and raindrop velocity show that natural rainfall is simulated with sufficient accuracy. The rainfall simulator used pressure nozzles to spray water for rainfall intensity from 40 to 220mm/hr. Uniformity distribution test gives coefficient of uniformity of 95% over an area of 1m2. The raindrops falling at velocity ranging from 0.5 to 15m/s with drop sizes diameter between 2 to 5mm. Free drainage system below the rainfall simulator is accompanied with outlet tanks attached with ultrasonic sensor devices to record the outflow data. During the experiments, the outflow received is 98% in average. Experiment results in typical runoff hydrograph and percolation rate of the MDPP system. This shows the ability of the rainfall simulator to obtain initial hydrology data to aid in the design of the MDPP prototype.  

scholarly journals Impact of Disdrometer Types on Rainfall Erosivity Estimation

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 963
Author(s):  
Lisbeth Lolk Johannsen ◽  
Nives Zambon ◽  
Peter Strauss ◽  
Tomas Dostal ◽  
Martin Neumann ◽  
...  
Keyword(s):  
Drop Size ◽  
First Generation ◽  
Rainfall Intensity ◽  
Measurement Instrument ◽  
Rainfall Erosivity ◽  
Data Handling ◽  
Rainfall Characteristics ◽  
Different Types ◽  
Spatial Differences ◽  
Soil Erosion By Water

Soil erosion by water is affected by the rainfall erosivity, which controls the initial detachment and mobilization of soil particles. Rainfall erosivity is expressed through the rainfall intensity (I) and the rainfall kinetic energy (KE). KE–I relationships are an important tool for rainfall erosivity estimation, when direct measurement of KE is not possible. However, the rainfall erosivity estimation varies depending on the chosen KE–I relationship, as the development of KE–I relationships is affected by the measurement method, geographical rainfall patterns and data handling. This study investigated how the development of KE–I relationships and rainfall erosivity estimation is affected by the use of different disdrometer types. Rainfall data were collected in 1-min intervals from six optical disdrometers at three measurement sites in Austria, one site in Czech Republic and one site in New Zealand. The disdrometers included two disdrometers of each of the following types: the PWS100 Present Weather Sensor from Campbell Scientific, the Laser Precipitation Monitor from Thies Clima and the first generation Parsivel from OTT Hydromet. The fit of KE–I relationships from the literature varied among disdrometers and sites. Drop size and velocity distributions and developed KE–I relationships were device-specific and showed similarities for disdrometers of the same type across measurement sites. This hindered direct comparison of results from different types of disdrometers, even when placed at the same site. Thus, to discern spatial differences in rainfall characteristics the same type of measurement instrument should be used.

scholarly journals Disdrometer measurements under Sense-City rainfall simulator

2019 ◽  
Author(s):  
Auguste Gires ◽  
Philippe Bruley ◽  
Anne Ruas ◽  
Daniel Schertzer ◽  
Ioulia Tchiguirinskaia
Keyword(s):  
Kinetic Energy ◽  
Size Distribution ◽  
Drop Size ◽  
Rain Rate ◽  
Drop Size Distribution ◽  
Climatic Chamber ◽  
Sampling Area ◽  
Data Set ◽  
Raw Data ◽  
Rainfall Simulator

Abstract. The Hydrology, Meteorology and Complexity laboratory of Ecole des Ponts ParisTech (hmco.enpc.fr) and the Sense-City consortium (http://sense-city.ifsttar.fr/) make available a data set of optical disdrometers measurements coming from a cam-paign that took place in September 2017 under the rainfall simulator of the Sense-City climatic chamber which is located near Paris. Two OTT Parsivel2 were used. The size and velocity of drops falling through the sampling area of the devices of roughly few tens of cm2 is computed by disdrometers. This enables to estimate the drop size distribution and further study rainfall micro-physics or kinetic energy for example. Raw data, i.e. basically a matrix containing a number of drops according to classes of size and velocity, along with more aggregated ones such rain rate or drop size distribution with filtering is available. Link to the data set (Gires et al., 2019): http://doi.org/10.5281/zenodo.3347051.

scholarly journals Analysis of day rainfall characteristics of Zhengzhou

2018 ◽  
Vol 38 ◽  
pp. 01031 ◽  
Author(s):  
Zhenzhou Shen ◽  
Wenyi Yao ◽  
Peiqing Xiao ◽  
Xueqin Yang
Keyword(s):  
River Basin ◽  
Rainfall Intensity ◽  
Yellow River ◽  
Yellow River Basin ◽  
Terminal Velocity ◽  
Rainfall Characteristics ◽  
Loess Slope ◽  
Natural Rainfall ◽  
Peak Value

Raindrop characteristics, including speed and size of raindrops, in Zhengzhou city of Yellow River basin were analyzed through a natural rainfall on the loess slope. Results showed that the process of natural rainfall belonged to a parabola and counts, size and terminal velocity would increase with the rainfall intensity rising. Besides, the size and terminal velocity of natural raindrops were relatively scattered; In the process of individual rainfall, the terminal velocity and its peak value were mainly focused between 0.8~5m/s and 1m/s, respectively. Size of raindrops were mainly consisted of 0.125-0.5mm, among which the terminal velocity of raindrops with a size of 0.125mm, 0.25mm, 0.375mm, 0.5mm were primarily 0.8-3.4m/s, 0.6-3.4m/s, 0.8-1m/s, 1-1.4m/s, respectively.

Concept of a New Pluviometer for Metering Rainfall Erosivity

2012 ◽  
Vol 452-453 ◽  
pp. 316-320 ◽  
Author(s):  
Andrea Alaimo ◽  
Mauro De Marchis ◽  
Gabriele Freni ◽  
Antonio Messineo ◽  
Dario Ticali
Keyword(s):  
Rainfall Intensity ◽  
Rainfall Erosivity ◽  
Natural Phenomena ◽  
Limited Data ◽  
Empirical Relationships ◽  
Rainfall Characteristics ◽  
Natural Rainfall ◽  
Main Driver ◽  
Raindrop Splash ◽  
The Impact

Rainfall is the main driver of several natural phenomena having a large impact on human activities. Its monitoring is then very important for natural disaster prevention and for the preservation of the environment. One important phenomenon is related to soil displacement due to rainfall impact. The intensity of physical soil degradation, detachment and transport of soil particles by raindrop splash and interrill erosion is largely controlled by rainfall characteristics. There is still a lot of debate as to whichparameter expresses the best rainfall erosivity. Due to the limited data ondrop-size distribution of natural rainfall and the time consuming nature of methods to obtain these data, rain erosivity parameters are commonly obtained from empirical relationships based on rainfall intensity. This paper describes an a new pluviometer able to measure several raindrop variables and assess rainfall kinetic energy at the impact with the ground. It enables one to measure drop size and drop velocity in real time and thus any parameter linked to rainfall erosivity. The pluviometer is based on the combination of optical and electrical sensors and it is based on cheap technologies in order to allow the easy distribution of several monitoring station on the analyzed area. A description of the device and of its sensor is presented in the present paper.

scholarly journals Rainfall Kinetic Energy in Denmark: Relationship with Drop Size, Wind Speed, and Rain Rate

2020 ◽  
Vol 21 (7) ◽  
pp. 1621-1637
Author(s):  
Anna-Maria Tilg ◽  
Flemming Vejen ◽  
Charlotte Bay Hasager ◽  
Morten Nielsen
Keyword(s):  
Wind Speed ◽  
Kinetic Energy ◽  
Drop Size ◽  
Rain Rate ◽  
Turbine Blades ◽  
Wind Turbine Blades ◽  
Fall Velocity ◽  
Wind Speeds ◽  
Low Wind Speeds ◽  
Rain Rates

AbstractRainfall kinetic energy is an important parameter to estimate erosion potential in connection to soil erosion or in the recent years to the erosion of the leading edges of wind turbine blades. Little is known about the seasonal drop size distribution and fall velocity dependence of rainfall kinetic energy as well as its relationship with wind speed. Therefore, 6 years of Thies Laser Precipitation Monitor disdrometer and wind measurements from Voulund, a field site in western Denmark, were analyzed. It was found that the rainfall kinetic energy was highest in summer due to higher drop concentrations and in autumn due to more time with rain. The rainfall kinetic energy peaked for drop diameters between 0.875 and 2.25 mm independent of the season. Rainfall kinetic energy decreased significantly with increasing wind speed, if considering the vertical fall speed of the drops for the calculation of the rainfall kinetic energy. However, it should be noted that the measurement uncertainty increases with increasing wind speed. As disdrometer observations are rarer than rain rate observations, the performance of empirical equations describing the relationship between rainfall kinetic energy rate and rain rate was investigated. It was found that an equation trained with an alternative method fulfilled the statistical requirements for linear regression and had a similar error compared to equations in the literature. Based on the analyses, it can be concluded that the erosion potential due to rainfall kinetic energy is highest between June and November at low wind speeds and high rain rates.

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