Rain Flow Research Articles

Tamaño de área de drenaje y conectividad hidrológica en la formación de escorrentía en cuencas semiáridas mediterráneas. Cuenca aforada del Barranc del Carraixet

The rainfall-runoff conversion is analysed taking in consideration the contributing area and hydrological connectivity, factors needing better understanding. Within the same basin, the Barranc del Carraixet near Valencia, has been selected three scales of work: four experimental plots (8 x 40 m), micro-basin (17.01 ha) and small drainage basin (127.9 km 2 ). For the analysis of runoff generation at different scales rainfall thresholds and runoff rates and thresholds were used. For hydrological connectivity, at plot level, coefficients of determination were analyzed. Inverse relationship is given between the volume of runoff and recurrence, with increasing scale. Connectivity, at plot level, is variable, increasing the R 2 according the simplification of processes, when the interference of vegetation decreases, establishing better linearity between rain and surface flow.

Applicability of Rain Flow Method to Fatigue Life Span Estimation of Overhead Contact Wire

The rain flow method has been put forward as a method for waveform counting to estimate what the fatigue life span would be under actual waveform stress. The authors carried out experiments to test its applicability to hard drawn copper contact wire. In order to consider the effect of mean tensile stress when applying the rain flow method it is first necessary to define the fatigue life span properties for the various mean tensile stresses. The authors confirmed that these estimations can be found using fatigue test results from hard drawn copper contact wire placed under two types of mean tensile stress condition. The authors then conducted six fatigue tests to investigate the applicability of the rain flow method. The actual measured fatigue life span in tests generally exceeded estimations. The rain flow method may therefore conceivably be used to derive a method for safe estimation of fatigue life.

The Influence of Rain Sensible Heat and Subsurface Energy Transport on the Energy Balance at the Land Surface

In land surface models, which account for the energy balance at the land surface, subsurface heat transport is an important component that reciprocally influences ground, sensible, and latent heat fluxes and net radiation. In most models, subsurface heat transport parameterizations are commonly simplified for computational efficiency. A simplification made in all models is to disregard the sensible heat of rain, Hl, and convective subsurface heat flow, qcv, i.e., the convective transport of heat through moisture redistribution. These simplifications act to decouple heat transport from moisture transport at the land surface and in the subsurface, which is not realistic. The influence of Hl and qcv on the energy balance was studied using a coupled model that integrates a subsurface moisture and energy transport model with a land surface model of the land surface energy balance, showing that all components of the land surface energy balance depend on Hl The strength of the dependence is related to the rainfall rate and the temperature difference between the rain water and the soil surface. The rain water temperature is a parameter rarely measured in the field that introduces uncertainty in the calculations and was approximated using the either air or wet bulb temperatures in different simulations. In addition, it was shown that the lower boundary condition for closing the problem of subsurface heat transport, including convection, has strong implications on the energy balance under dynamic equilibrium conditions. Comparison with measured data from the Meteostation Haarweg, Wageningen, the Netherlands, shows good agreement and further underscores the importance of a more tightly coupled subsurface hydrology–energy balance formulation in land surface models.

An evaluation of three wood shred blends for post-fire erosion control using indoor simulated rain events on small plots

The assessment teams who make post-fire stabilization and treatment decisions are under pressure to employ more effective and economic post-fire treatments, as wild fire activity and severity has increased in recent years across the western United States. Use of forest-native wood-based materials for hillslope mulching has been on the rise due to potential environmental, erosion control efficacy, and economic incentives. One concern regarding use of woody materials prepared on or near burned sites is the wide range in the size distribution of the shredded materials. We tested three blends of shredded woody materials, each blend containing different amounts of fine (less than 2.5 cm in length) woody particles. The blends (AS IS with 24% fines, MIX with 18% fines, and REDUCED with 2% fines) were applied at 50 and 70% ground cover to 5-m2 plots containing burned soil placed at 40% slope and evaluated through simulated rain events which consisted of a rain only, a rain plus low flow, and a rain plus high flow period. The REDUCED blend was the optimum for both runoff and sediment concentration reduction under conditions of rainfall and rainfall plus concentrated flow. There was no difference between application rates of 50 and 70% for either of the rainfall plus concentrated flows tested. Our recommendation was that 50% ground cover of the REDUCED blend was adequate for both rainfall and sediment reduction compared to a bare soil. The other two blends were effective in reducing runoff but not sediment concentration compared to a bare soil. The wood shred manufacturing and blending process resulted in two statistically different relationships between application rate and ground cover; relationships were controlled by the amount of fines.

Rain Loads and Flow Attenuation on Roofs

Basic relationships are derived for calculating the flow attenuation and depth of storm water on roofs. Hyetographs and corresponding hydrographs are specialized to the case of roof drainage and incorporated in methods which are presented for analysis and design of roof drains. Roof storage and outflow are characterized for various roof geometries and outflow devices. The methods are applied to examples found in the literature, including those in standards of Factory Mutual Insurance Company, ASCE, and others. Assumptions implicit in those standards are tested and their limitations demonstrated. A critical duration at which the greatest water depth and outflow occur must be found on a case-by-case basis. The critical durations can differ significantly from the fixed durations specified in standards. The corresponding maximum water depths and peak outflows can also differ accordingly. For determination of roof loads, these results will have their greatest importance in warmer climates in which the rain loads govern over snow loads. An example of design specifically for flow attenuation is also presented.

Fatigue life prediction of horizontally curved thin walled box girder steel bridges

The fatigue damage accumulation rates of horizontally curved thin walled box-girder bridge have been estimated from vehicle-induced dynamic stress history using rain flow cycle counting method in the time domain approach. The curved box-girder bridge has been numerically modeled using computationally efficient thin walled box-beam finite elements, which take into account the important structural actions like torsional warping, distortion and distortional warping in addition to the conventional displacement and rotational degrees of freedom. Vehicle model includes heave-pitch-roll degrees of freedom with longitudinal and transverse input to the wheels. The bridge deck unevenness, which is taken as inputs to the vehicle wheels, has been assumed to be a realization of homogeneous random process specified by a power spectral density (PSD) function. The linear damage accumulation theory has been applied to calculate fatigue life. The fatigue life estimated by cycle counting method in time domain has been compared with those found by estimating the PSD of response in frequency domain. The frequency domain method uses an analytical expression involving spectral moment characteristics of stress process. The effects of some of the important parameters on fatigue life of the curved box bridge have been studied.

Integration of neural networks in a geographical information system for the monitoring of a catchment area

The present work takes part in a global development of reliable and robust tools allowing real-time controlling and supervising of the Têt catchment area, the main river of the Pyrénées-Orientales department (Southern France). The impact of the Têt on the department life is significant and the management of its water quality must be largely improved and better supervised. The main purpose of the work was to develop “rain flow” predictive models, using Elman recurrent neural networks and based on the identification of localized rain events. These neural models allow understanding the dynamic evolution, according to rain events, of the Têt flow at a selected point and of the Perpignan WWTP (WasteWater Treatment Plant) influent flow. Their most interesting characteristic is their capability to predict big increases in river flow and in plant influent flow. The neural models have been integrated as thematic layers in a geographical information system (GIS) allowing an efficient management and update of the records used to develop the models.

3D SIMULATION OF BLOCKING OF BRIDGE IN MOUNTAIN STREAM BY DRIFT WOODS

When a lot of drift woods due to locally heavy rain flow into a mountain stream, a bridge is caused by serious damages. Damed-up drift woods may cause a flood, and piers and slabs of a bridge can be broken due to the collision with drift woods. Because such damages due to drift woods are recently increasing, it is necessary to consider the prevention against them. In order to make effective guidelines of prevention works, detailed mechanism should be examined. However, 3D numerical simulations of dam-up process of drift woods and resultant overflow around a bridge have not been carried out before. In this study, a numerical analysis by the MPS method is executed in the 3D field to simulate dam-up process of drift woods onto a small slab bridge in a mountain stream.

Fatigue lifetime under uniaxial random loading with different mean values according to some selected models

In the paper, the experimental fatigue lives of plane specimens made of 10HNAP steel have been compared with the calculated lives for random tension loading with non-zero mean value. The cycle amplitude transformation methods proposed by Goodman and Gerber, the Van Dang criterion, averaging with the Svenson–Lipp method and the strain energy density parameter was used. Cycles were counted by the rain flow algorithm; in the case of the Svenson–Lipp method the fatigue cycles were counted by the rain flow algorithm and the level crossing algorithm. Damages were accumulated according to the Palmgren–Miner hypothesis.

Study on Generalized Fatigue Damage under Random Loading

Generalized fatigue damage is derived based on S-N curve under constant amplitude loads with S characterizes the load cycle by the combination of load peak and load amplitude. For random fatigue loads, a natural choice is to use half cycle (Range) counting method. Rain Flow counting is popular due to its useful nature to pick-out full cycles among random loads. It is found in the present research through analysis and verified by experimental results that Rain Flow counting seriously overestimate the damage for the actual true random loads owing to its inherent nature and the Range counting method is more reliable. As the filtering threshold increases gradually, the overestimation effect by Rain Flow counting method becomes less, and the calculated damages by Rain Flow and Range counting begin to converge. The filtering threshold damage corresponding to the “fatigue limits” for the concerned case was calculated. According to equal damage principle, the filtering threshold amplitudes were derived and found to vary with the load peaks. In practice, an acceptable solution is to use quasi-variable filtering thresholds.

A Study on Load Analysis and Durability Test Condition of Automobile Brake Pedal

Automobile pedal which is loaded by driver’s input is transmitting load to throttle cable, braking device and clutch device and controlling automobile. Measuring working condition and applying equivalent damage are needed for reliability of developing pedal. The measuring working condition is requiring more investigation with various respects because of widely ranged drivers, road condition and environmental condition. Additionally, when equivalent damage is applied, there are not suitable for test condition if equivalent damage is too high level to apply or unused region. In this study, load history is measured with 95percentile customer. Measured load history is converted to stress history about critical area of pedal by FEM. There are drawn up histogram of pedal cycles and load from stress history with rain flow cycle counting method, calculated relative damage of extended stress history with Palmgren-Miner rule. From the results, calculated total relative damage is applied to calculation method of test time and load. Calculation method for test condition is carried out with three methods which are enforcing with total stress by rain flow cycle counting, representative load and blocked load. Accelerated durability test condition of pedal using with relative damage and acceleration factors are proposed.

Interrill soil erosion processes and their interaction on low slopes

AbstractSoil erosion by water is mostly the result of rainfall‐driven and runoff‐driven processes taking place simultaneously during a storm event. However, the effect of interaction between these two erosion processes has received limited attention. Most laboratory experiments indicate that the rate of erosion in a rain‐impacted flow is greater than for un‐impacted flows of similar depth and velocity; however, negative interaction between the two processes has also been reported. There is no provision for any such interaction in any of the current erosion models. This paper reports on the results of a number of exact experiments on three soil types carried out in the flume of Griffith University's large rainfall simulator to study interaction between rain and runoff processes. The results show that interaction is generally positive under approximately steady state condition and there is very limited sign of negative interaction reported by others. Results provide strong evidence that raindrops continuously peel fine sediment from larger stable aggregates. This mechanism could be the reason for positive interaction during simultaneous rainfall and flow driven erosion in well aggregated soils as a result of increased fine particles in the eroded sediment. Strong positive interaction between rain and runoff erosion also occurs for medium to large aggregates. This strongly suggests that mechanisms that are not well understood are operational. It is quite possible that particle movement can be stimulated by rolling or creeping in a size‐selective manner. Indeed, such additional mechanisms may well be largely responsible for the positive interaction observed between rain and surface flow. Copyright © 2006 John Wiley & Sons, Ltd.

Characteristics of heavy elements in sediments of Lake Donghu (Wuhan) and relations to urban pollution

应用主成份分析原理,按照主成份提取的信息超过原始信息84%的原则,对武汉市东湖的主体湖区(郭郑湖和塘林湖)的0 cm-7 cm的沉积物30个代表性样品12种元素进行分析,确定其沉积物的重金属的污染源的主要类型．结果表明,郭郑湖第一污染源(占56%)为湖区周围的工业燃煤尘埃,其次(占16%)为交通尾气、生活污水和雨水片流,再次 (占12%)为电镀、印刷等行业的工业污水．塘林湖第一污染源(占65%)为湖区周围的生产性煤燃烧的粉尘,其次(17%) 为生活污水、医院污水和周围土壤的淋溶作用,再次(占9%)为废旧电池、报章杂志和农用物资等．采用均方根综合污染指数法评价分析东湖主体湖区的沉积物的污染程度为轻度污染,其中郭郑湖的污染程度高于塘林湖．;In order to determine the main types of pollution origins of the heavy metals of sediments of Lake Donghu, Wuhan, based on principle of principal components and the rule of picked-up information which is over 84% of original ones, we have analyzed twelve elements of thirty representative samples of 0 -7 cm sediments of Lake Guozheng and Lake Tanglin, which are the main sub lake of Lake Donghu, Wuhan city. The results indicate that for Guozheng Lake sediments, the first pollution origin (56%) is industry coal dust around the lake, the second origins (16%) are tail gas, domestic sewage and rain flow, and the third parts(12%) are industry sewage with electroplate and press etc. For Lake Tanglin, the first pollution origin (65%) is atmosphere dust which is from industry coal combustion, the second origins (17%) are sewage with household, hospital and soil etc, and the third parts(9%) are disused battery, newspapers and farming materials etc. Employing the comprehensive pollution indexes of heavy metals, which were calculated by root mean square on the background values, to evaluate the pollution degree of sediments of main sublakes of Lake Donghu, it is found that both of them belong to light contamination and the pollution degree of Lake Guozheng is higher than that of Lake Tanglin.

Energy and water use at a WSUD subdivision in Brisbane, Australia

This paper reports on the water and energy balances of a small ecosensitive subdivision in Brisbane, Australia. The 22-lot development is designed around individual and communal rainwater tanks, on-site greywater reuse, off-peak sewer pump outs, and energy and water efficient house design and appliances. Results to date are limited by time and occupied house constraints, but they clearly identified the importance of rainwater and greywater in substituting for potable water (up to 190 L/hh/year). However, this water self sufficiency came at the cost of specific energy use well in excess of that from centralised water and sewerage systems. Suggestions are made on how to offset these energy losses, and include greenhouse gas efficient hot water system and grid connected photovoltaics (PVs). Future monitoring will include the social attitudes of residents towards sustainable urban practices and composition of the various water streams (e.g. rain, greywater, sewage and storm flow)

Antonomous Environmental Definition of C-130 Flap Well Skin Panel

Air Force C-130 aircraft require numerous aluminum doubler repairs on the wing flap skin aft of the right-hand outboard engine. These repairs are costly and require riveting. Rivets often provide new areas of stress concentration, which causes new cracks to develop elsewhere. Boeing and the Air Force Research Laboratory (AFRL) are measuring the thermal and strain environment behind the right-hand outboard engine of a North Carolina Air National Guard (NCANG) operational C-130 aircraft (TN 93-1456) for use in design of a damped repair patch to prevent the growth of cracks in skin under the wing flap panel. During June 2003. AFRL engineers and technicians acquired data using an autonomous damage dosimeter during five operational C-130 flights. The damage dosimeter measures structural strains and temperatures on in-service aircraft to diagnose structural conditions that are difficult to analyze, such as acoustics and high cycle fatigue (HCF). The first flight was from Charlotte, North Carolina to Warner Robins Air Force Base (AFB), Georgia and returned to Charlotte. The last four flights were assault flights where the C-130 simulated cargo drops. Pilots logged the altitude and indicated airspeed, engine speed, and flap positions for the first four flights. Flap position settings were compared with dosimeter temperature and root mean square (rms) strain measurements. This paper presents typical third octave plots showing engine speed vibratory frequencies, rms time histories (TH), and correlation data for a flight. This paper also presents typical limited data in TH, probability density function (PDF), power spectral density (PSD), and rain flow formats.

レインフロー法と疲労限度線図を用いた実働荷重疲労に対する構造物信頼性評価

A service load like random load has been analyzed by the rain flow method extensively. When the reliability of a structure is estimated, mean stresses on fatigue life are probably ignored because it is not easy to measure. The purpose of this study is to propose a practical estimation method of a structural reliability for fatigue under service loads by Miner's law. In addition, the fatigue tests to obtain S-N curve is carried out under constant amplitude loading. However, the each stress ratio of cyclic stress counted with rain flow method is different. In the proposed method, the effect of stress ratio has been considered by fatigue limit diagram with failure probability. On this diagram, the increment of cumulative cycle ratio ΔDpf for each cyclic stress can be calculated with failure probability by a computer program. The expected life Npf is defined as the period when Dpf reaches 1.0. If we assume the ergodicity of the sampling time T, Npf is T/Dpf. It gives fatigue life distribution, when a structure is under service loads. In conclusion, we have got a reliability curve of the structure for fatigue life. This curve can be obtained with service load or design stress easily by using our developed program. This proposed method is practical and the industrial applicability is wide.

Comparison of the Rain Flow Algorithm and the Spectral Method for Fatigue Life Determination Under Uniaxial and Multiaxial Random Loading

Abstract This paper presents the strain energy density parameter used for fatigue life calculation under random loading by two methods. The first method is based on schematization of energy parameter histories with the rain flow algorithm. The other one is based on moments of the power spectral density function of the energy parameter. The experimental data of fatigue tests of 10HNAP steel under constant amplitude and random uniaxial loading with non-gaussion probability distribution, zero mean value, and wide-band frequency spectrum used for comparison of the rain flow algorithm and the spectral method gave satisfactory results. Next, histories of the random stress tensor with normal probability distribution, wide-band frequency, and zero mean values corresponding to biaxial tension-compression, combined tension with torsion and triaxial loading with various correlation coefficients were generated, and the lifetime was calculated. It has been observed that both methods of fatigue life determination give almost the same results.

Application of the Dang‐Van criterion for life determination under uniaxial random tension–compression with different mean values

ABSTRACTIn this paper the experimental fatigue lives of specimens made of 10HNAP steel with the lives calculated with the Goodman and Gerber methods of cycle amplitude transformation and the Dang Van criterion for uniaxial loading are compared. Cycles were counted with the rain flow algorithm and damage was accumulated according to the Palmgren–Miner hypothesis. This paper includes comparison of the results for constant amplitude loading with a non‐zero mean value and for random loading with zero or non‐zero mean values. It has been shown that for 10HNAP steel the algorithm of fatigue life calculations using the Dang Van criterion gives satisfactory results.

Variable amplitude fatigue of spot welds

ABSTRACTA new method for fatigue life prediction of spot welds subjected to variable amplitude loads is proposed. The method is based on the concept of crack closure and is experimentally verified with three different specimens and four different load signals with variable amplitude. Experimental fatigue lives were found to be within a factor of three from the predicted lives. To start with, the stress intensity factor history at the spot weld is calculated with a finite element analysis. Then, crack closure is taken into account: the crack opening stress intensity factor, which is assumed to be constant, is determined from the maximum and minimum in the history. All stress intensities lower than the crack opening level are filtered from the calculated history. The filtered history is then analysed with rain flow count. Finally, fatigue life is predicted with the Palmgren–Miner cumulative damage rule together with an effective (closure‐free) curve for spot welds. In addition, single overload tests were carried out to investigate the assumption of a constant crack opening stress.

Comparing Fatigue Life Estimates Using Experimental and Spectral Density Based Probability Distributions

Random vibration, high-cycle fatigue problems in thin-skinned structures are of concern to the U.S. Air Force. Therefore, the U.S. Air Force is interested in available methods used to approximate the response and fatigue life of aircraft structures exposed to random vibration loading, notably those exhibiting geometric nonlinear effects. The purpose of this investigation is to examine and compare the fatigue life estimates of a fully clamped aluminum plate under the influence of random electrodynamic shaker loading. The experimental strain probability density function was generated using the rain flow cycle counting technique, and the resulting fatigue estimates were compared with spectral-based finite element analysis (FEA) and experimental random response fatigue estimates (Anzai, Hiroyuki, Algorithm of the rainflow method, The International Symposium on Fatigue Damage Measurement and Evaluation under Complex Loading, OND Sokkic, Ltd., July 1991; Bannantine, J. A., Comer, J. J., and Handrock, J. L., Fundamentals of Metal Fatigue Analysis, Prentice-Hall, Inc., Upper Saddle River, NJ, 1990, pp. 193-196). The plate was modeled using the ABAQUS® linear random response algorithm and a modified nonlinear FEA code developed by Mei et al. of Old Dominion University (Dhainaut, J. M., Bin, D., Mei, C., Spottswood, S. M., and Wolfe, H. F., Non-Linear Response of Composite Panels to Random Excitation and Elevated Temperature, Structural Dynamics: Recent Advances, Univ. of Southampton, U.K., 2000; Shi, Y., and Mei, C., A Finite Element Time Domain Modal Formulation for Large Amplitude Free Vibrations of Beams and Plates, Journal of Sound and Vibration, Vol. 193, No. 2, 1996, pp. 453-464). For all scenarios the Palmgren-Miner linear damage accumulation model was utilized (Miner, M. A., Cumulative Damage in Fatigue, Journal of Applied Mechanics, Vol. 67, 1945, pp. A159-A182). This simple isotropic plate case was selected as a means for accurate assessment, as opposed to using a more complex structure initially. Results indicate that the spectral-density-based analyses provide overly conservative fatigue life estimates when compared with the experimental based fatigue life estimates.