scholarly journals Bedload Transport Monitoring in Alpine Rivers: Variability in Swiss Plate Geophone Response

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4089 ◽  
Author(s):  
Gilles Antoniazza ◽  
Tobias Nicollier ◽  
Carlos R. Wyss ◽  
Stefan Boss ◽  
Dieter Rickenmann
Keyword(s):  
Maximum Amplitude ◽  
Detailed Comparison ◽  
Bedload Transport ◽  
Measuring Site ◽  
Power Law Function ◽  
Alpine Streams ◽  
Signal Response ◽  
Alpine Rivers ◽  
The Impact ◽  
Calibration Coefficients

Acoustic sensors are increasingly used to measure bedload transport in Alpine streams, notably the Swiss plate geophone (SPG) system. An impact experiment using artificial weights is developed in this paper to assess the variability in individual plate response and to evaluate the extent to which calibration coefficients can be transferred from calibrated plates to non-calibrated plates at a given measuring site and/or to other measuring sites. Results of the experiment over 43 plates at four measuring sites have notably shown (a) that the maximum amplitude (V) recorded by individual plates tends to evolve as a power law function of the impact energy (J), with an exponent slightly larger than 1, for all the plates at all measuring sites; (b) that there is a substantial propagation of energy across plates that should be taken into account for a better understanding of the signal response; (c) that the response of individual plates is in most cases consistent, which suggests that calibration coefficients are comparable within and in between measuring sites, but site-specific and plate-specific variabilities in signal response have to be considered for a detailed comparison.

scholarly journals Signal response of the Swiss plate geophone monitoring system impacted by bedload particles with different transport modes

2021 ◽  
Author(s):  
Zheng Chen ◽  
Siming He ◽  
Tobias Nicollier ◽  
Lorenz Ammann ◽  
Alexandre Badoux ◽  
...  
Keyword(s):  
Particle Size ◽  
Maximum Amplitude ◽  
Impact Angle ◽  
Bedload Transport ◽  
Frequency Change ◽  
General Increase ◽  
Transport Mode ◽  
Centroid Frequency ◽  
Signal Response ◽  
Transport Modes

Abstract. Controlled experiments were performed to investigate the acoustic signal response of the Swiss plate geophone (SPG) system impacted by bedload particles varying in size, impact angle and transport mode. The impacts of bedload particles moving by saltation, rolling, and sliding were determined by analyzing the experimental videos and corresponding vibration signals. For a particle impact on the bed or on the geophone plates, the signature of the generated signal in terms of maximum amplitude, number of impulses and centroid frequency was extracted from the raw monitoring data. So-called signal packets were determined by performing a Hilbert transform of the raw signal. The number of packets was calculated for each transport mode and for each particle size class, with sizes ranging from 28.1 mm to 171.5 mm. The results show how the number of signal impulses per particle mass, the amplitude of the signal envelope, and the centroid frequency change with increasing particle size, and they also demonstrate the effect of bedload transport mode on the signal response of the SPG system. We found that there is a general increase in the strength of the signal response or in the centroid frequency when the transport mode changes from sliding to rolling to saltation. The findings of this study help to better understand the signal response of the SPG system for different bedload transport modes, and may also contribute to an improvement of the procedure to determine bedload particle size from the SPG signal.

Swiss Geophone Plate system: Quantification of the variability of signal response and of the signal propagation across plates using field-based impact experiments

2020 ◽  
Author(s):  
Gilles Antoniazza ◽  
Tobias Nicollier ◽  
Carlos R. Wyss ◽  
Stefan Boss ◽  
Dieter Rickenmann
Keyword(s):  
Maximum Amplitude ◽  
Signal Propagation ◽  
Bedload Transport ◽  
Swiss Alps ◽  
Measuring Station ◽  
Absolute Mass ◽  
Load Transport ◽  
Bed Load Transport ◽  
Signal Response ◽  
Plate System

<p>Impact sensors are increasingly used to indirectly monitor bedload transport in streams. Among them, the Swiss geophone impact plate system has notably proved its efficiency to continuously record bed load transport rates. Nevertheless, this approach still requires a robust calibration of the sensors to transform the relative signal of the geophones into an absolute mass of sediment in transport. Typically, the calibration is performed through the sampling during natural bedload transport events of all the particles that impact the plates, in order to build up rating curves between the signal recorded by the geophone sensors and the characteristics of the sediment that impact them (e.g. mass, grain size).  To better understand the system behavior it is important to quantify to what extent the signal response is similar (i) between sensors of a same geophone measuring station and (ii) between different geophone measuring stations. Also (iii), the amount of signal that propagates from impacted plates towards non-impacted plates (or ‘neighbouring noise’) needs to be quantified to improve the understanding of the system.</p><p>In this study, we investigate the above three elements by performing an impact experiment on the Swiss geophone plate system, and systematically record the signals produced at different plates by defined impacts of similar magnitude, and how the signal (maximum amplitude) propagates through neighbouring non-impacted plates. Each Swiss Geophone Plate of four measuring stations in the Swiss Alps – Vallon de Nant (VD), Albula (GR), Naviscence (VS) and Riedbach (VS) – were hit alternatively with impacts of increasing magnitude, and the signal they produced was systematically recorded over all the sensors of a given measuring station. Results of the study allow (i) to quantify the neighbouring noise that propagates from impacted plates towards non-impacted plates; (ii) to evaluate the attenuation rate of the signal for an impact of a given magnitude and (iii) to evaluate the variability in the propagation of neighbouring noise between sensors at a given measuring station and between different measuring stations.</p>

scholarly journals The intensity of slope and fluvial processes after a catastrophic windthrow event in small catchments in the Tatra Mountains

2021 ◽  
Vol 18 (6) ◽  
pp. 1405-1423
Author(s):  
Dariusz Strzyżowski ◽  
Elżbieta Gorczyca ◽  
Kazimierz Krzemień ◽  
Mirosław Żelazny
Keyword(s):  
Environmental Changes ◽  
Bedload Transport ◽  
Strong Wind ◽  
Tatra Mountains ◽  
Salvage Logging ◽  
Fluvial Processes ◽  
Wind Events ◽  
And Control ◽  
The Tatra Mountains ◽  
The Impact

AbstractStrong wind events frequently result in creating large areas of windthrow, which causes abrupt environmental changes. Bare soil surfaces within pits and root plates potentially expose soil to erosion. Absence of forest may alter the dynamics of water circulation. In this study we attempt to answer the question of whether extensive windthrows influence the magnitude of geomorphic processes in 6 small second- to third-order catchments with area ranging from 0.09 km2 to 0.8 km2. Three of the catchments were significantly affected by a windthrow which occurred in December 2013 in the Polish part of the Tatra Mountains, and the other three catchments were mostly forested and served as control catchments. We mapped the pits created by the windthrow and the linear scars created by salvage logging operations in search of any signs of erosion within them. We also mapped all post-windthrow landslides created in the windthrow-affected catchments. The impact of the windthrow on the fluvial system was investigated by measuring a set of channel characteristics and determining bedload transport intensity using painted tracers in all the windthrow-affected and control catchments. Both pits and linear scars created by harvesting tend to become overgrown by vegetation in the first several years after the windthrow. The only signs of erosion were observed in 10% of the pits located on convergent slopes. During the period from the windthrow event in 2013 until 2019, 5 very small (total area <100 m2) shallow landslides were created. The mean distance of bedload transport was similar (t-test, p=0.05) in most of the windthrow-affected and control catchments. The mapping of channels revealed many cases of root plates fallen into a channel and pits created near a channel. A significant amount of woody debris delivered into the channels influenced the activity of fluvial processes by creating alternating zones of erosion and accumulation.

Controlled experiments and finite element simulations with the Swiss plate geophone bedload monitoring system: particle size identification and transport mode

2021 ◽  
Author(s):  
Zheng Chen ◽  
Siming He ◽  
Tobias Nicollier ◽  
Lorenz Ammann ◽  
Alexandre Badoux ◽  
...  
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Finite Element ◽  
Quantitative Agreement ◽  
Bedload Transport ◽  
Material Structure ◽  
Flume Experiments ◽  
Fem Simulations ◽  
Transport Mode ◽  
Signal Response

&lt;p&gt;The Swiss plate geophone (SPG) system is an indirect bedload transport monitoring device that records the acoustic signals generated by bedload particle impacts, with the goal to derive the bedload flux and grain size distribution. Particle drop experiments with quartz spheres in quiescent water in a flume setting were performed to investigate the dynamic signal response of the SPG system impacted by particle-like objects varying in size and impact location. Systematic flume experiments with natural bedload particles in flowing water were conducted to study the effects of impact angle and transport mode (saltating, rolling and sliding) on the SPG signals. For each impact caused by a single particle, the number of signal impulses, the amplitude, the positive area surrounded by the signal envelope, and the centroid frequency were extracted from the raw geophone monitoring data. The finite element method (FEM) was used to construct a virtual model of the SPG system and to determine the propagation characteristics of the numerical stress wave in the material structure. The experimental and numerical results showed a qualitative and partially quantitative agreement in the changes of the signal impulses, the amplitude, and the envelope area with increasing colliding sphere size. The centroid frequencies of the SPG vibrations showed qualitatively similar dependencies with increasing particle size as some field measurements for the coarser part of the investigated range of impact sizes. The effects of variable particle impact velocities and impact locations on the geophone plate were also investigated by drop experiments and compared to FEM simulations. In addition, the signal response for different bedload transport modes and varying impact angles were explored. In summary, the FEM simulations contribute to the understanding of the signal response of the SPG system and the findings in this study may eventually result in improving the bedload grain size classification and transport mode recognition.&lt;/p&gt;

A nonlinear multi-scale theory of atmospheric blocking: Structure and evolution of blocking linked to meridional and vertical structures of storm tracks

2021 ◽  
Author(s):  
Dehai Luo ◽  
Wenqi Zhang
Keyword(s):  
Storm Track ◽  
Interaction Model ◽  
Maximum Amplitude ◽  
Transient Eddy ◽  
Baroclinic Mode ◽  
Upper Troposphere ◽  
Multi Scale ◽  
The North ◽  
Baroclinic Modes ◽  
The Impact

AbstractThis paper examines the impact of the meridional and vertical structures of a preexisting upstream storm track (PUST) organized by preexisting synoptic-scale eddies on eddy-driven blocking in a nonlinear multi-scale interaction model. In this model, the blocking is assumed, based on observations, to be comprised of barotropic and first baroclinic modes, whereas the PUST consists of barotropic, first baroclinic and second baroclinic modes. It is found that the nonlinearity (dispersion) of blocking is intensified (weakened) with increasing amplitude of the first baroclinic mode of the blocking itself. The blocking tends to be long-lived in this case. The lifetime and strength of blocking are significantly influenced by the amplitude of the first baroclinic mode of blocking for given basic westerly winds (BWWs), whereas its spatial pattern and evolution are also affected by the meridional and vertical structures of the PUST.It is shown that the blocking mainly results from the transient eddy forcing induced by the barotropic and first baroclinic modes of PUST, whereas its second baroclinic mode contributes little to the transient eddy forcing. When the PUST shifts northward, eddy-driven blocking shows an asymmetric dipole structure with a strong anticyclone/weak cyclone in a uniform BWW, which induces northward-intensified westerly jet and storm track anomalies mainly on the north side of blocking. However, when the PUST has no meridional shift and is mainly located in the upper troposphere, a north-south anti-symmetric dipole blocking and an intensified split jet with maximum amplitude in the upper troposphere form easily for vertically varying BWWs without meridional shear.

Development of Model for Acoustic Noise Generated from Bedload in Rivers 

2021 ◽  
Author(s):  
Mohamad Nasr ◽  
Thomas Geay ◽  
Sébastien Zanker ◽  
Recking Alain
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Impact Velocity ◽  
Acoustic Noise ◽  
Acoustic Power ◽  
Bedload Transport ◽  
Empirical Formulas ◽  
Impact Rate ◽  
Flux Measurements ◽  
The Impact

&lt;p&gt;Quantifying bedload transport is important for many applications such as river management and hydraulic structures protection. Bedload flux measurements can be achieved using physical sampler methods. However, these methods are expensive, time-consuming, and difficult to operate during high discharge events. Besides, these methods do not permit to capture the spatial and temporal variability of bedload transport flux. Recently, alternative measuring technologies have been developed to continuously monitor bedload flux and grain size distribution using passive or active sensors. Among them, the hydrophone was used to monitor bedload transport by recording the sounds generated by bedload particles colliding on the river bed (referred as self-generated noise SGN). The acoustic power of SGN was correlated with bedload flux in field experiments. To better understand these experimental results and to estimate measurement uncertainties, we developed a theoretical model to simulate the SGN. The model computes an estimation of the power spectral density (PSD)by considering the contribution of all signals generated by impacts between bedload particles and the riverbed, and accounting for the attenuation of the acoustic signal between the source and the hydrophone position due to river propagation effects,. In this model, we&lt;/p&gt;&lt;p&gt;The energy of acoustic noise generated from the collision between two particles is mainly dependent on the transported particles' diameter and the impact velocity. We tested different empirical formulas for the estimation of the number of impact (impact rate) and the impact velocity depending on particle size and hydraulic conditions. To characterize the acoustic power losses as a function of distance and frequency, we used an attenuation function which was experimentally calibrated for different French rivers.&lt;/p&gt;&lt;p&gt;We tested the model on a field dataset comprising acoustic and bedload flux measurements. The results indicate that the PSD model allows estimating acoustic power (in between a range of one order of magnitude) for most of the rivers considered.&amp;#160; The model sensitivity was evaluated. In particular, we observed that it is very sensitive to the empirical formulas used to determine the impact rate and impact speed. In addition, special attention should be kept in mind on the assumption of the grain size distribution of riverbed which can generate large variability in some rivers particularly in rivers with a significant sand fraction.&lt;/p&gt;

Total and fractional bedload transport in alpine streams approximated by different surrogate measurement systems

2021 ◽  
Author(s):  
Lorenz Ammann ◽  
Tobias Nicollier ◽  
Alexandre Badoux ◽  
Dieter Rickenmann
Keyword(s):  
Grain Size ◽  
Measurement Techniques ◽  
Bedload Transport ◽  
Accelerometer Sensor ◽  
Protection Measures ◽  
Measurement Systems ◽  
Size Classes ◽  
Alpine Streams ◽  
Surrogate Measurement ◽  
Using Data

&lt;p&gt;Knowledge about bedload transport in rivers is of high importance for many hydraulic engineering applications, in particular related to flood protection measures. Passive acoustic surrogate measurement techniques provide useful continuous estimates of bedload transport in terms of total mass, as well as for different grain-size classes.&lt;/p&gt;&lt;p&gt;We compare different surrogate measurement systems regarding their performance in quantifying total and fractional bedload transport in three alpine streams. The investigated measurement systems are the well-established Swiss plate geophone (SPG), an equivalent system in which the geophone sensor is replaced by an accelerometer sensor, and the miniplate accelerometer (MPA) system. The latter is a more recent device and consists of four small square metal plates embedded in elastomere elements. While the signal recorded with the SPG is known to be proportional to the transported bedload mass, we find that the MPA-signal shows a non-linear dependency. In addition, the MPA reacts more sensitively to small grain size classes than the other two systems, indicating a possible alternative to improve the quantification of bedload transport consisting of those classes.&lt;/p&gt;&lt;p&gt;Based on the raw signal recorded with the SPG and the MPA in a flume experiment, we test the ability of different empirical models to predict the known weight of the impacting particle. We show that it is possible to identify the particle weight with high accuracy with relatively simple models using data of either of the two measurement systems. One remaining challenge is to account for the site-to-site variability in the (amount of) signal caused by the combination of differing numbers of plates in the measurement setup and the lateral transmission of the signal across multiple plates, especially for the SPG system.&lt;/p&gt;

scholarly journals Impacts of some meteorological parameters on the SO2 concentrations in the city of Obrenovac, Serbia

2010 ◽  
Vol 75 (5) ◽  
pp. 703-715 ◽  
Author(s):  
Snezana Nenadovic ◽  
Ljiljana Matovic ◽  
Misko Milanovic ◽  
Sava Janicevic ◽  
Jasmina Grbovic-Novakovic ◽  
...  
Keyword(s):  
Sulfur Dioxide ◽  
Power Plants ◽  
Meteorological Parameters ◽  
North West ◽  
Wind Speeds ◽  
The North ◽  
West Part ◽  
Measuring Site ◽  
The Impact ◽  
The City

In this paper, the impacts of some meteorological parameters on the SO2 concentrations in the City of Obrenovac are presented. The City of Obrenovac is located in the north-west part of Serbia on the banks of the River Sava. The observed source emission, the power plants TENT A and TENT B are situated on the bank of the Sava River in the vicinity of Obrenovac. During the period from January to November 2006, the concentrations of sulfur dioxide in the air at 4 monitoring sites in Obrenovac were measured. It was noticed that the maximal measured daily concentrations of sulfur dioxide ranged from 1 ?g/m3 (16th November, 2006) to 98 ?g/m3 (29th January 2006) and lie under the maximal allowed concentration value according to the Serbian Law on Environmental Protection. The measured sulfur dioxide concentrations mostly showed characteristics usual for a daily acidification sulfur dioxide cycle, excluding the specificities influenced by the measuring site itself. Sulfur dioxide transport was recorded at increased wind speeds, primarily from the southeast direction. Based on the impact of meteorological parameters on the sulfur dioxide concentration, a validation of the monitoring sites was also performed from the aspect of their representivity.

Analysis of mistuned forced response in an axial high-pressure compressor rig with focus on Tyler–Sofrin modes

2019 ◽  
Vol 123 (1261) ◽  
pp. 356-377
Author(s):  
F. Figaschewsky ◽  
A. Kühhorn ◽  
B. Beirow ◽  
T. Giersch ◽  
S. Schrape
Keyword(s):  
Axial Compressor ◽  
Maximum Amplitude ◽  
Forced Response ◽  
Operating Conditions ◽  
Cfd Simulations ◽  
High Pressure Compressor ◽  
Engine Order ◽  
Stator Vane ◽  
Vibration Responses ◽  
The Impact

ABSTRACTThis paper aims at contributing to a better understanding of the effect of Tyler–Sofrin Modes (TSMs) on forced vibration responses by analysing a 4.5-stage research axial compressor rig. The first part starts with a brief review of the involved physical mechanisms and necessary prerequisites for the generation of TSMs in multistage engines. This review is supported by unsteady CFD simulations of a quasi 2D section of the studied engine. It is shown that the amplitude increasing effect due to mistuning can be further amplified by the presence of TSMs. Furthermore, the sensitivity with respect to the structural coupling of the blades and the damping as well as the shape of the expected envelope is analysed.The second part deals with the Rotor 2 blisk of the research compressor rig. The resonance of a higher blade mode with the engine order of the upstream stator is studied in two different flow conditions realised by different variable stator vane (VSV) schedules which allows to separate the influence of TSMs from the impact of mistuning. A subset of nominal system modes representation of the rotor is used to describe its mistuned vibration behaviour, and unsteady CFD simulations are used to characterise the present strength of the TSMs in the particular operating conditions. Measured maximum amplitude vs blade pattern and frequency response functions are compared against the predictions of the aeromechanical models in order to assess the strength of the TSMs as well as its influence on vibration levels.

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