Juan Francisco Fuentes-Perez

Joint Estimation of Bulk Flow Velocity and Angle Using a Lateral Line Probe

Measurement of complex natural flows, especially those occurring in rivers due to man-made structures, is often hampered by the limitations of existing flow measurement methods. Furthermore, there is a growing need for new measurement devices that are capable of measuring the hydrodynamic characteristics of complex natural flows required in environmental studies that often use fish as an indicator of ecological health. In this paper, we take the first step toward in situ natural flow measurements with a new biologically inspired probe design in conjunction with signal processing methods. The device presented in this paper is a dedicated hydrodynamically sensitive sensor array following the fish lateral line sensor modality. Low-level multidimensional sensor signals are transformed to the two key hydrodynamic primitives, bulk flow velocity and bulk flow angle. We show that this can be achieved via canonical signal transformation and kernel ridge regression, allowing velocity estimates with a less than 10 cm/s error. The approach provides robust velocity estimates not only when the sensor is ideally oriented parallel to the bulk flow, but also across the full range of angular deviations up to a completely orthogonal orientation by correcting the pressure field asymmetry for large angular deviations. Furthermore, we show that their joint estimation becomes feasible above a threshold current velocity of 0.45 m/s. The method demonstrated an error of 14 cm/s in velocity estimation in a river environment after training in laboratory conditions.

Modeling Water-Depth Distribution in Vertical-Slot Fishways under Uniform and Nonuniform Scenarios

AbstractVertical slot fishways are a type of fish pass of wide operating range that allow fish to move across obstacles in rivers. This study aims to model the performance of these structures, under uniform and nonuniform flow conditions, using discharge coefficients involving the downstream water level together with a logical algorithm. This will allow an explanation of the hydraulic behavior of this type of fishway under tailwater levels and flow variations on rivers. Two vertical slot fishways located in Duero River (North-Central Spain), subject to different hydraulic conditions, were studied for the validation of the proposed formulation. The observed values are consistent with the predicted results and, among others, demonstrate the importance of including variables that consider downstream water level. Consequently, the proposed discharge coefficients together with the algorithm have resulted in a method that enables the improvement of the performance of both existing and future vertical slot fishw...

Design and application of a fish-shaped lateral line probe for flow measurement

We introduce the lateral line probe (LLP) as a measurement device for natural flows. Hydraulic surveys in rivers and hydraulic structures are currently based on time-averaged velocity measurements using propellers or acoustic Doppler devices. The long-term goal is thus to develop a sensor system, which includes spatial gradients of the flow field along a fish-shaped sensor body. Interpreting the biological relevance of a collection of point velocity measurements is complicated by the fact that fish and other aquatic vertebrates experience the flow field through highly dynamic fluid-body interactions. To collect body-centric flow data, a bioinspired fish-shaped probe is equipped with a lateral line pressure sensing array, which can be applied both in the laboratory and in the field. Our objective is to introduce a new type of measurement device for body-centric data and compare its output to estimates of conventional point-based technologies. We first provide the calibration workflow for laboratory investigations. We then provide a review of two velocity estimation workflows, independent of calibration. Such workflows are required as existing field investigations consist of measurements in environments where calibration is not feasible. The mean difference for uncalibrated LLP velocity estimates from 0 to 50 cm/s under in a closed flow tunnel and open channel flume was within 4 cm/s when compared to conventional measurement techniques. Finally, spatial flow maps in a scale vertical slot fishway are compared for the LLP, direct measurements, and 3D numerical models where it was found that the LLP provided a slight overestimation of the current velocity in the jet and underestimated the velocity in the recirculation zone.

Estimation of Flow Turbulence Metrics With a Lateral Line Probe and Regression

The time-averaged velocity of water flow is the most commonly measured metric for both laboratory and field applications. Its employment in scientific and engineering studies often leads to an oversimplification of the underlying flow physics. In reality, complex flows are ubiquitous, and commonly arise from fluid-body interactions with man-made structures, such as bridges as well as from natural flows along rocky river beds. Studying flows outside of laboratory conditions requires more detailed information in addition to time-averaged flow properties. The choice of in situ measuring device capable of delivering turbulence metrics is determined based on site accessibility, the required measuring period, and overall flow complexity. Current devices are suitable for measuring turbulence under controlled laboratory conditions, and thus there remains a technology gap for turbulence measurement in the field. In this paper, we show how a bioinspired fish-shaped probe outfitted with an artificial lateral line can be utilized to measure turbulence metrics under challenging conditions. The device and proposed signal processing methods are experimentally validated in a scale vertical slot fishway, which represents an extreme turbulent environment, such as those commonly encountered in the field. Optimal performance is achieved after 10 s of sampling using a standard deviation feature.

RAPTOR-UAV: Real-time particle tracking in rivers using an unmanned aerial vehicle

River system measurement and mapping using UAVs is both lean and agile, with the added advantage of increased safety for the surveying crew. A common parameter of fluvial geomorphological studies is the flow velocity, which is a major driver of sediment behavior. Advances in fluid mechanics now include metrics describing the presence and interaction of coherent structures within a flow field and along its boundaries. These metrics have proven to be useful in studying the complex turbulent flows but require time-resolved flow field data, which is normally unavailable in geomorphological studies. Contactless UAV-based velocity measurement provides a new source of velocity field data for measurements of extreme hydrological events at a safe distance, and could allow for measurements of inaccessible areas. Recent works have successfully applied large-scale particle image velocimetry (LSPIV) using UAVs in rivers, focusing predominantly on surficial flow estimation by tracking intensity differences between georeferenced images. The objective of this work is to introduce a methodology for UAV based real-time particle tracking in rivers (RAPTOR) in a case study along a short test reach of the Brigach River in the German Black Forest. This methodology allows for large scale particle tracking velocimetry (LSPTV) using a combination of floating, infrared light-emitting particles and a programmable embedded color vision sensor in order to simultaneously detect and track the positions of objects. The main advantage of this approach is its ability to rapidly collect and process the position data, which can be done in real-time. The disadvantages are that the method requires the use of specialized light-emitting particles, which in some cases cannot be retrieved from the investigation area, and that the method returns velocity data in unscaled units of px/s. This work introduces the RAPTOR system with its hardware, data processing workflow, and provides an example of unscaled velocity field estimation using the proposed method. First experiences with the method show that the tracking rate of 50 Hz allows for position estimation with sub-pixel accuracy, even considering UAV self-motion. A comparison of the unscaled tracks after Savitzky-Golay filtering shows that although the time-averaged velocities remain virtually the same, the filter reduces the standard deviation by more than 40% and the maxima by 20%.

Forschung und Technik

Seit 2011 wurden durch die EnBW in Zusammenarbeit mit dem Institut fur Umwelt studien Versuche zum Scheuchen und Leiten von Fisch en mit elektrischem Strom durchgefuhrt. Dabei wurde neben der Barrierewirkung von elektrischen Feldern auch die Moglichkeit zum Stoppen und Leiten von Fisch en entlang elektrifizierter Rechenanlagen untersucht. Die Versuche wurden sowohl unter Freilandbedingungen vor dem Einlaufbauwerk eines Kraftwerks als auch in einem Versuchsbecken durchgefuhrt. Die Ergebnisse zeigen, dass durch den Einsatz elektrischer Felder eine erhohte Abweise- oder Leitwirkung erzielt werden kann.

Underwater vehicle speedometry using differential pressure sensors: Preliminary results

Underwater vehicles require accurate speedometry relative to local flow conditions to perform many tasks within the aquatic environment. This paper presents preliminary results of a differential pressure sensing system using an extension of the Pitot equation capable of providing instantaneous flow speed estimation, including yaw angles from ±45°. In contrast to systems with similar configuration based on absolute pressure sensor approaches, the differential system makes use of the pressure between two points on the sensor head, reducing the number of necessary sensors by half. The theoretical system performance and physical prototype are compared using computational fluid dynamics and flow tunnel tests from 0-0.5 m/s and angles of attack up to ±45°. The proposed speedometry device has a small form factor, uses inexpensive commodity hardware, is geometrically simple, accurate (mean absolute error of 0.024 m/s) and has low power consumption (<; 10 mW for each sensor) making it suitable for a wide spectrum of underwater vehicles.