Differential pressure sensor base artificial lateral line probe, iRon

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Figure 1: iRon, the lateral line probe (LLP). NACA0025 body shape showing the locations of the differential pressure sensors (1-6), and the absolute pressure sensor (7)[3].

Figure 2: Velocity estimation with an artificial lateral line. a) Distribution of pressure over the body of the lateral line. b) Estimation of velocity considering different pressure differences around the body and different shapes [4].

Figure 3: Distribution of mean pressure asymmetry for different refuge layouts (R0: control, R1: close triangles, and R2: open triangles) and hydrodynamic scenarios [3].

Developed by: Centre for Biorobotics

Date: 2016

Type: Device

Suitable for the following [[::Category:Measures|measures]]:

Introduction

“iRon” is a device that mimics the lateral line sensory system used by fish in nature (artificial lateral line) and that allows the characterization of flow fields from a fish perspective. First artificial lateral lines were developed to provide sensing capabilities to small underwater robots (EU project FILOSE, 2009-2012 [1]) and they were further developed for environmental monitoring in BONUS FishView project (2013-2016) [2].

In contrast to conventional flow measuring devices (such as ADVs, propellers, etc.), they are streamlined bodies which record the spatial distribution of fluid-body interactions at a sampling rate close to that of the sensory organs (up to 400 Hz in the latest designs). From these records, point-based hydrodynamic parameters such as velocity or turbulence metrics can be estimated, but also body-oriented metrics (“flow asymmetry”).

iRon belongs to a new generation of artificial lateral lines where an increase of sensitivity is achieved by the use of differential pressure sensors. It consists of a 0.22 m long NACA025 streamlined body, which measures the pressure gradients simultaneously using six differential pressure sensors (±2000 Pa MPXV7002). In addition, the water depth is measured by the probe using an absolute pressure sensor (0 to 10000 Pa – MPX5010GP) (Figure 1).

Application

Within the scope of FIThydro, a BMS consisting of a geophone and accelerometer was installed on the vortex tube at HPP Schiffmühle, which diverts bedload from the headwater channel to the residual flow reach. The vortex tube consists of a steel tube embedded in the side weir, connecting the two parallel channels (Figure 45). A gate valve is positioned in the side weir, which opens automatically when a predefined discharge is exceeded. The opening of the valve automatically triggers the BMS measurements.

In contrast to the SPGS, the steel tube is used as an impact plate for the BMS and the sensors are mounted directly onto the outside of the steel tube (Figure 46). Therefore, laboratory calibration was not easily possible. Instead, the system was calibrated in the field by repeatedly dumping sediment samples of known grain size distribution and volume upstream of the vortex tube and subsequently flushing them to the residual flow reach. In addition, drop tests with single grains were performed when the vortex tube was not in operation. The single grain signals help to analyze the influence of grain size, grain form, drop height, and drop location on the amplitude and frequency signals.

The first results of the presented BMS are promising, but the data analysis will be further refined and extended. Furthermore, a larger number of recorded flood events is necessary to check the plausibility of the results obtained so far. Overall, it is demonstrated that the measurement principle of the state-of-the-art SPGS can be extended to non-standardized impact plates like steel vortex tubes, and the use of an additional accelerometer sensor, given that appropriate calibration measures are taken.

Other information

The total costs for the geophone and accelerometer sensors amount to approx. 885-1'330 €. The costs for the field computer, the analog-digital-converter, and the 3G modem are approx. 5'300-6'200 €. Additional costs for the installation, data transmission, and the calibration depending on the site conditions and set-up.

Relevant literature

• Albayrak, I., Müller-Hagmann, M., Boes, R.M. (2017). Calibration of Swiss Plate Geophone System for bedload monitoring in a sediment bypass tunnel. In Proc. 2nd Intl. Workshop on Sediment Bypass Tunnels (Sumi, T., ed.), paper FP16, Kyoto University, Kyoto, Japan

• Gray, J.R., Laronne, J.B., Marr, J.D.G. (2010). Bedload-surrogate Monitoring Technologies, US Geological Survey Scientific Investigations Report 2010-5091. US Geological Survey: Reston VA.

• Rickenmann, D., Turowski, J.M., Fritschi, B., Klaiber, A., Ludwig, A. (2012). Bedload transport measurements at the Erlenbach stream with geophones and automated basket samplers. Earth Surface Processes and Landforms, 37, 1000-1011.

• Rickenmann, D., Turowski, J.M., Fritschi, B., Wyss, C., Laronne, J., Barzilai, R., Reid, I., Kreisler, A., Aigner, J., Seitz, H., Habersack, H. (2014). Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel-bed streams. Earth Surface Processes and Landforms, 39, 928-942.

• Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M, Weitbrecht, V., Boes, R.M. (2016a). Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 1. Impulse counts and particle size identification. Water Resources Research, 52, 7744-7759.

• Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M, Weitbrecht, V., Boes, R.M. (2016b). Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 2. Application to field sites with direct bed load samples. Water Resources Research, 52, 7760-7778.