Directional Measurements Research Articles

Method for simultaneous measurement of velocity and direction of fluid flow using fiber Bragg gratings

This work is devoted to the development and research of a new optical method for measuring the velocity of a fluid flow and determining the orthogonal directions of such a flow. Comparing with gas flow, measuring the fluid flow rate requires higher heating power and insulation, which is taken into account in this work. The standard hot-wire anemometry method is taken as a basis, but instead of a metal thread, optical fiber is used for measurements. The article presents the design of a sensitive element consisting of two optical fibers. The first fiber contains an array of fiber Bragg gratings and is used as a measurement element. The second fiber has a region with a tapered structure and is used to create a heated area. Velocity measurements are given for the range of 0.02–0.05 m/s, but are limited only by the capabilities of the measuring stand. A unique method for identifying the orthogonal flow direction, which has not been described in the literature before, is presented. Differences in the shapes of the curves for the dependences of flow rates moving in the direction and orthogonally to the axis of the sensitive element are presented. The stability of the device is also confirmed by continuous experiments for 70 min.

INTEGRATION METHOD FOR MEASURING QIBLA DIRECTION (COMPARATIVE ANALYSIS OF GOOGLE EARTH AND MIZWALA)

The accuracy of measuring the qibla direction of the mosque in Kendal, Central Java, needs attention from astronomy because the majority of people only know the traditional qibla direction measurement tool namely using a compass and the sun's shadow method. Even though errors in the use of the method will result in inaccurate measurement results and have an impact on the validity of the prayers performed. Therefore, this study compares two methods that are easy for the public to use, namely Google Earth and Mizwala. Google Earth as a method to check the qibla direction and Mizwala as a comparison method to improve Google Earth. Through mathematical qualitative methods with data collection techniques through observation and interviews, it is known that these two methods are the easiest and most accurate to determine the qibla of all mosques. The method of data collection was carried out by calculating and measuring the qibla direction towards 1 mosque and 5 musholla. Although the two methods differ in terms of appearance, that Google Earth uses a satellite network while Mizwala uses the concept of the Sun's shadow, both of them can be used in an easy and integrative way. The result of Mizwala's measurements with Google Earth conclude error tolerance that is a range of minutes of angle. In the end, the two methods can be integrated to help and increase public awareness about the importance of correct qibla direction accuracy.

Probabilistic inversion of circular phase spectra: application to two-station phase-velocity dispersion estimation in western Canada

SUMMARY Periodic directional and temporal measurements are common in seismology, and necessitate specific statistical analyses that are appropriate for circular quantities. In this work, we explore the use of a von Mises distribution as a representation of errors on circular seismological observations. Specifically, we automate the estimation of surface-wave phase-velocity dispersion for the teleseismic two-station method, which generally suffers from a 2π phase ambiguity. The use of Bayesian inverse techniques, which aim to rigorously quantify model parameter uncertainty, have become widespread throughout seismology over the last decade. Here, we apply Bayesian inversion to measurements of surface-wave phase spectra in order to estimate 1-D, path-averaged Earth structure between station pairs. The dispersion curve and associated uncertainties are additional results of the inversion, which can then be used as input for subsequent analyses (e.g. tomography). We demonstrate this technique through application to surface-wave recordings from long-running seismic stations throughout western Canada. Our results for over 10 000 station pairs reveal first-order tectonic features consistent with previous studies, which provides confidence in our approach as well as an initial step towards resolving a full 3-D seismic velocity model for the region. This work also presents a foundation for the inversion of surface-wave phase spectra to estimate 3-D Earth structure directly. Finally, the ideas presented in this work are not limited to the inversion of surface-wave phase spectra, but can also be considered for Bayesian geophysical inversion of any circular quantities.

Performance of a vehicle-mounted anemometer under crosswind: Simulation and experiment

Abstract Environmental wind measurements are essential for ensuring the operational safety of rail vehicles. In our previous work, an anemometer that can be mounted on the top of a train to achieve real-time measurements of wind speed and direction was proposed based on the pressure distributions around the cylindrical anemometer. However, the flow field on the top of the train is significantly influenced by the train; thus, the measured data might differ from the actual environmental wind parameters, particularly when trains are subjected to windbreak walls. In this study, simulations considering flow fields around trains installed with the proposed anemometer were conducted, and an improved delayed detached eddy simulation approach was adopted. Through simulations, the flow field at the top of the train was analysed, and the aerodynamic characteristics of the anemometer were investigated. Accordingly, relationships between the measured wind characteristics and environmental wind characteristics are presented under various situations herein. Field experiments were performed for the proposed anemometer installed on a certain type of high-speed train along the Nanjiang Railway in China. The results obtained from both the numerical and experimental studies show that the proposed method has high accuracy for measuring environmental wind speed and direction when mounted on the top of a train.

An Array Multi-Physics Acquisition System with Focus on Reservoir Monitoring for the Energy Transition

During the energy transition, geophysics will need to focus on novel green energy applications and to reduce the carbon footprint of hydrocarbon production. For both reservoir, monitoring is important, in particular dynamic monitoring of reservoir fluids. For renewable energies such as geothermal, electromagnetics has always been the geophysical ‘work horse’, while mostly microseismic has been used for monitoring. For hydrocarbon reservoirs, added value toward ZERO carbon footprint is obtained by increasing the recovery factor by of 30-40 % and thus reducing the cost/carbon emission per produced barrel. In addition, CO2 is sequestered in brine saturated reservoirs and also needs to be monitored. We are addressing the fluid monitoring issue here for electromagnetics and are reviewing how hardware, methodology and application are interlinked to build a complete system. Various applications and case histories where the results can be verified by borehole logs support this. The key issue is that our measurement need to respond to geologic realistic Earth formations which are, generally speaking, anisotropic. We direct the entire design of the system in solving that problem with direc-tional sensitive measurements. Next, when we want to monitor reservoir change we require a repeatability and accuracy hereto not necessary. By carefully controlling the entire hardware design from sensor to applications stage this can be achieved and we can obtain log scale resolution from surface measurement which was hereto not possible.

Continuous measurement of flow direction and streamflow based on travel time principles using a triangular distribution of acoustic tomography systems

Monitoring flood dynamics is important to provide optimal flood mitigation practices and understand their hydrological responses. Recently, applications of travel time principles have gained a growing interest in hydrological research and river engineering. In this study, flood dynamics were monitored using the fluvial acoustic tomography system (FAT), based on travel time principles. The primary objective of this study is to continuously measure the mean cross-sectional velocity, river flow direction, and river discharge using an innovative tomographic system during two flood events. In this regard, three FAT systems were placed in a gravel bed stream forming a triangle shape to measure stream velocity along two cross-sections. By investigating the magnitude of the cross-sectional mean velocity vectors and the cross-sectional areas, we proposed new equations to evaluate the expected flow direction. The performance of flow measurement by the FAT system was verified with another reference record. Importantly, we demonstrated that the minimum number of acoustic stations to determine river flow direction in unidirectional streams can be reduced to three stations which can be more practical and easier. Further, one of the novel aspects of this study is offering new guidelines to continuously estimate flow direction using a triangular distribution of tomographic systems. In general, this study presents a promising method for monitoring flow dynamics in rivers.

Directional wave measurements from navigational buoys

In-situ wave measurements are often required by marine industry standards and for verification of coastal wave forecasts. Obtaining wave measurements is costly and it would be advantageous to utilize existing platforms like navigational buoys designed for environmental monitoring. In this study, a wave sensor module (MOTUS Wave Sensor, Aanderaa Data Instruments) installed on a navigational buoy (Tideland) and a coastal buoy (EMM2.0) is validated against a dedicated wave measurement buoy (Waverider, Datawell). The validation is based upon four months of measurements off the west coast of Norway. The results show that the MOTUS sensor on-board navigational/coastal buoys provide accurate measurements of wave parameters compared to Waverider. Wave height biases were less than 0.04 m over the full wave spectra, and less than 5% for frequencies between 0.05 and 0.45 Hz (0.01 Hz bin width). Mean wave direction bias for the full spectra was 1.4 and 2.8 degrees, and less than 5 and 10 degrees in frequency bins between 0.05 and 0.45 Hz for the navigational and coastal buoy, respectively. External compass measurements were required for accurate directional measurements for the coastal buoy. The validated wave sensor provides in-situ directional wave measurements with measurement uncertainties well within recommended accuracy levels.

Reliability in measurement of three-dimensional anterior pelvic plane orientation by registration with an inertial measurement unit.

It is strongly challenging to obtain functional movement of the pelvis based on the three-dimensional (3D) dynamic anterior pelvic plane (APP) orientation information. This study provided the 3D APP orientation measurement technique by registration with an inertial measurement unit (IMU), and its reliability was tested. The local coordinate systems of the APP and the IMU sensor were registered using two images of the pelvic part from the frontal and left sagittal views in a neutral standing posture. Then, the measurement errors in the APP orientation were analyzed by comparing the values obtained from manually measured four points in the IMU sensor and the known exact values in 10 different postures. Moreover, the errors between values obtained from manually measured three anatomical points and the known exact values were also compared. The average errors were quite small (less than 0.6°) when measuring from three anatomical points and were acceptable (1.6°-3.4°) when measuring from four points in the IMU sensor. These results indicate that the measurement of APP direction using four points in the IMU sensor could be considered reliable in terms of intra-participant and inter-participant. The present technique to register the IMU sensor position and the APP direction by taking X-ray images from the frontal and sagittal directions can be fundamental information to measure the APP direction during dynamic motion when the IMU position is obtained from the IMU sensor data instead of the four-point location information.

Model to subtract contributions of scattered radiation from measured direct transmittance and specular reflectance by light diffusing materials.

The formalism of the Lorenz-Mie (LM) theory is used to estimate the contributions of radiation being scattered into the detector acceptance angle of spectrophotometers (with or without an integrating sphere) to the apparent direct transmittance and specular reflectance measurements. These contributions are subtracted from the measurements before doing the inversion to obtain the spectral variation of the scattering and absorption (S&A) coefficients of optically particulate liquid samples, decoupling the contribution to extinction from these two mechanisms. The method is applied to transmittance spectra of Pickering emulsions of dodecane oil (DO) and DO micelles with saturated dissolved Nile red dye, stabilized with anatase (T i O 2) in water. What we believe to be novel expressions are given to estimate the forward and backward average path-length parameters of propagating diffuse radiation from its equivalent quantities defined within the formalism of the LM theory and to relate these single particle average path-length parameters with the forward scattering ratio, asymmetry parameter, and higher-order coefficients in the expansion of the LM phase function. This novel approach makes it possible to avoid the underestimation of the S&A coefficients, which arises when the correction is not made by subtracting that contribution due to scattered radiation that is reaching the detectors from the directional reflectance and transmittance measurements.

Experimental setup for direct measurements of spectral directional emissivity from 0° to 80° angles at temperatures as low as 40 °C

In this work, a direct method is developed for measuring the spectral directional emissivity of optically thick materials for temperatures ranging between 40 °C and 450 °C at angles from 0° to ∼ 80°. The direct method consists in measuring and comparing thermal radiation emitted from a sample to that of a blackbody reference source. Emphasis is placed on the importance of accurate calibration when performing measurements at low temperature (<50 °C) and on the assessment of uncertainty, estimated between 2 and 20% in the best and worst configuration respectively. The sample is fixed on a heater mounted on a rotation stage allowing directional measurements. Thermal radiation is collected by an optical setup and sent to a Fourier-transform infrared spectrometer (FTIR) performing spectral measurements in the 2–25 μm range using a room-temperature DTGS detector. Sample, blackbody source and optics are placed inside a black-coated enclosure purged with dry air and equipped with temperature sensors for estimating angle-dependent ambient radiation incident on the sample. As examples to illustrate the capabilities of the setup, directional spectral measurements are performed from normal to 80° on both a SiO2 and an aluminum sample at 100 °C.

Ensemble-Based Flow Field Estimation Using the Dynamic Wind Farm Model FLORIDyn

Wind farm control methods allow for a more flexible use of wind power plants over the baseline operation. They can be used to increase the power generated, to track a reference power signal or to reduce structural loads on a farm-wide level. Model-based control strategies have the advantage that prior knowledge can be included, for instance by simulating the current flow field state into the near future to take adequate control actions. This state needs to describe the real system as accurately as possible. This paper discusses what state estimation methods are suitable for wind farm flow field estimation and how they can be applied to the dynamic engineering model FLORIDyn. In particular, we derive an Ensemble Kalman Filter framework which can identify heterogeneous and changing wind speeds and wind directions across a wind farm. It does so based on the power generated by the turbines and wind direction measurements at the turbine locations. Next to the states, this framework quantifies uncertainty for the resulting state estimates. We also highlight challenges that arise when ensemble methods are applied to particle-based flow field simulations. The development of a flow field estimation framework for dynamic low-fidelity wind farm models is an essential step toward real-time dynamic model-based closed-loop wind farm control.

Multichannel Directional Recognition SPR Curvature Sensor Based on D-Type Double-Clad Multimode Fiber

A fiber surface plasmon resonance (SPR) curvature sensor has the advantage of being insensitive to axial strain and temperature, but there are still difficulties in multichannel cascade and curvature direction identification. In this article, a multichannel directional recognition SPR curvature sensor based on D-type double-clad multimode fiber was proposed. The asymmetric structure of D-type multimode fiber can well realize directional curvature sensing. When the light in the multimode core leaks to the silica clad, due to the existence of plastic clad, it can still continue to transmit. When the refractive index of UV curable adhesive coated in different sensing areas is different, wavelength-division multiplexing multichannel sensing can be realized. When the sensing probe is bent to be convex, the maximum intensity sensitivity is 0.0057 a.u./m−1, the resonance wavelength is redshift, and the wavelength sensitivity is 0.6114 nm/m−1. When the sensor probe is bent to be concave, the maximum intensity sensitivity is 0.0043 a.u./m−1, the wavelength is blueshift, and its highest sensitivity is 0.5831 nm/m−1. In addition, this article also realizes a three-channel directional recognition SPR curvature sensor based on a D-type double-clad multimode fiber, which provides a new scheme for multichannel directional curvature measurement.

Experimental-cum-numerical approach for directional skid resistance measurement of grooved pavements

Currently there is no standard procedure for measuring the directional skid resistance of grooved pavements using the British pendulum tester (BPT). This study shows that BPT measured directional British pendulum numbers (BPNs) could over-estimate the actual directional BPN values of grooved pavements by more than 10 BPN at test angle of 90° to the grooves. The present study develops an experimental-cum-numerical procedure to provide corrections to measured directional BPNs of grooved pavements. Based on a single directional BPN measured in any test direction, the procedure permits one to calculate the full range of corrected directional BPNs at test angles between 0 and 90°. Corrected BPNs are derived from rubber-pavement friction coefficients back-calculated from measured BPNs. This was achieved through the application of two numerical skid resistance simulation models: a finite-element BPT simulation model and a finite-element sliding tire simulation model. The validity of the proposed approach was verified experimentally.

Two Low-Complexity DOA Estimators for Massive/Ultra-Massive MIMO Receive Array

Eigen-decomposition-based direction finding methods of using large-scale/ultra-large-scale fully-digital receive antenna arrays lead to a high or ultra-high complexity. To address the complexity dilemma, in this letter, three low-complexity estimators are proposed: partitioned subarray auto-correlation combining (PSAC), partitioned subarray cross-correlation combining (PSCC) and power iteration max correlation successive convex approximation (PI-Max-CSCA). Compared with the conventional no-partitioned direction finding method like root multiple signal classification (Root-MUSIC), in the PSAC method, the total set of antennas are equally partitioned into subsets of antennas, called subarrays, each subarray performs independent DOA estimation, and all DOA estimates are coherently combined to give the final estimation. For a better performance, the cross-correlation among sub-arrays is further exploited in the PSCC method to achieve the near-Cramer-Rao lower bound (CRLB) performance with the help of auto-correlation. To further reduce the complexity, in the PI-Max-CSCA method, using a fraction of all subarrays to make an initial coarse direction measurement (ICDM), the power iterative method is adopted to compute the more precise steering vector (SV) by exploiting the total array, and a more accurate DOA value is found using ICDM and SV through the maximum correlation method solved by successive convex approximation. Simulation results show that as the number of antennas goes to large-scale, the proposed three methods can achieve a dramatic complexity reduction over conventional Root-MUISC. Particularly, the PSCC and PI-Max-CSCA can reach the CRLB while the PSAC shows a substantial performance loss.

Characterizing the anisotropic response of similar and dissimilar FSW joints by DIC-based simultaneous strain measurements on two orthogonal surfaces

In friction stir welding (FSW), various zones with microstructural heterogeneity are formed with a difference in local constitute properties. To define anisotropy ratio through strain measurement in thickness and width direction simultaneously, utilizing a standard contact-type extensometer is challenging, or assuming volume constancy to calculate strain in the thickness direction may not be applicable for FSW joints. The present work proposes an approach where strain is measured concurrently on two mutually perpendicular (width and thickness) surfaces of a deforming tensile specimen by digital image correlation. Strain localization and local anisotropy ratio are calculated over the specimen gauge length, and the average anisotropy ratio is specified for the similar and dissimilar FSW joints of AA6061 and AA7075. For AA6061 similar FSW joints, tensile specimens with longitudinal axis along (θ = 0°) or close to weld line that contains solely stir zone (SZ) material and/or minimal presence heat affected zone (HAZ) exhibit uniform strain accumulation and failure from SZ. However, beyond that, the presence and orientation of HAZ influence the strain localization, anisotropy and subsequent failure. For dissimilar AA6061-AA7075 FSW joints, the anisotropic nature is largely governed by the strain localization at the softer material rather than the orientation of various zones within the specimen gauge length.

Exploring the Kinematic Structure of Mount Etna Volcano (Sicily, Italy) by Deformation Analysis and Gravity Gradient Tensors

Ground deformation monitoring of active volcanoes is used routinely to determine phases of vol‐ cano unrest and can provide insights in the evolving plumbing system of a volcano and the influence local tectonics structures have on the volcano tectonic evolution of the volcanic edifice. Volcanic deformation analysis can be performed using velocity and direction measurements of the ground surface using Global Navigation Satellite System (GNSS). In this study, we perform two‐dimen‐ sional deformation analyses of pre‐ and post‐eruptive phases with the scope of determining the strain before and after an eruptive phase at Mt. Etna Volcano (southern Italy) during 2004‐2006. In order to do so, we analyse the GNSS displacement data from Mt. Etna between 2004‐2005 and 2005‐2006 using the dedicated SSPX software. The extention, dilation and rotation maps of the study area were determined. The contraction and volumetric decrease concomitant the 2004‐2005 effusive eruptive period and extension and volumetric increase for the 2005‐2006 data series were observed. The deformation on the northeast part of Mt. Etna Volcano, which showed different characteristics with respect to its surroundings, was thought to be conditioned by the dynamic of the Pernicana fault system. Additionally, Complete Spherical Bouguer (CSB) gravity anomaly and the gravity gradient tensors were calculated giving insight on the subsurface structures of Mt. Etna Volcano and its surroundings.

Synchronous three-dimensional detection method for multiple parameters of wind fields based on vector principle.

In the area of air-assisted spray, conventional detection of speed and direction of the wind fields for spray are separately conducted, and multiple kinds of sensors have to be laid on each coordinate axis during multidimensional detection. It limits the optimization of operation effect of sprayers based on wind-field distribution characteristics. This paper proposes a novel detection method to achieve synchronous measurement of wind speed and direction in three dimensions. Wind flow was considered as vectors and the sensing structure with a regular triangular pyramid shape supported by cantilever pieces was established. Strain gauges were utilized to detect the deformation in each direction by the wind thrust onto a ball before and after wind flow. Moreover, the calculation models of wind speed and direction were developed respectively based on the relationship of 'strains-force-wind pressure-wind velocity' and the principle of space operation of vectors, so multiple parameters of wind fields could be obtained simultaneously. Calibration was conducted based on a wind tunnel and the Testo 405i anemometers. The results showed that: the minimum relative error of wind-speed values was about 0.06%, while the maximum was about 10%. The average relative error of all the directions was less than 5%. Furthermore, the measurement of the wind among artificial tree canopies demonstrated that the proposed method could effectively measure both speed value and direction of the wind among canopies, and it also helped to find the wind distribution characteristics of the fan, SFG4-2R. The results highlighted both the reliability and the practical meaning of the proposed method, which could be a technical solution for measuring and evaluating wind-field characteristics of sprayers.

Quantifying errors in wind and wave measurements from a compact, low-cost wave buoy

A yearlong wind and wave dataset derived from a cost-effective GPS wave buoy (Spotter) is compared to waves obtained from an accelerometer wave buoy (Datawell) and winds obtained from a collocated meteorological buoy. Overall, there was a strong correlation in bulk wave parameters obtained from the Spotter buoy and the Datawell buoy (RMSE of 0.06 m, 0.27 s, and 21.89° for significant wave height, mean wave period, and peak wave direction, respectively). Similarly, the bulk characteristics compared well when separating the directional wave spectra into sea and swell components with more scatter in mean wave periods for lower frequencies. Measurements of mean directional spread from the Spotter buoy were 7.51° larger than the Datawell, spreading more wave energy across different directions outside the peak direction. Additional analysis indicates that the increased directional spreading arises from a bias in the a1 and b1 spectral moments. Using the equilibrium frequency range of the wave energy spectrum, the Spotter buoy can derive wind speed and direction. This study found the Spotter buoy can report wind speed and direction with reasonable accuracy but underestimates wind speeds less than 4 m/s and greater than 8 m/s and was less accurate reporting wind directions oriented offshore. A comparison with a Spotter buoy in deeper water revealed the Spotter buoy further offshore was most accurate in reporting wind directions indicating this proxy-based measurement of wind speed and wind direction may be significantly influenced by fetch and local geography (e.g., large-scale cuspate coastlines).

Experimental and numerical study of the emissivity of rolled aluminum

Directional spectral emissivity measurements on a rolled aluminum sheet are reported between 423 and 823 K in vacuum. The results are compared to available literature data and to theoretical predictions, revealing the crucial role of the surface state in explaining the observed scatter of values. In particular, it is argued that the cold-rolling process induces a multi-scale roughness profile that significantly enhances emission at all wavelengths, a phenomenon that can be described using rigorous coupled-wave analysis (RCWA). A small peak in the p-polarized component at oblique angles is formed by the native oxide layer. Aside from the intrinsic value of the emissivity data for the application of thermographic techniques to rolled aluminum materials, the results contained in this work also serve to validate the usefulness of RCWA to simulate the emissivities of randomly rough metal surfaces, highlighting directions of further research.

Overcoming Bias: Equivariant Filter Design for Biased Attitude Estimation With Online Calibration

Stochastic filters for on-line state estimation are a core technology for autonomous systems. The performance of such filters is one of the key limiting factors to a system's capability. Both asymptotic behavior (e.g., for regular operation) and transient response (e.g., for fast initialization and reset) of such filters are of crucial importance in guaranteeing robust operation of autonomous systems. This letter introduces a new generic formulation for a gyroscope aided attitude estimator using <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N$</tex-math></inline-formula> direction measurements including both body-frame and reference-frame direction type measurements. The approach is based on an integrated state formulation that incorporates navigation, extrinsic calibration for all direction sensors, and gyroscope bias states in a single equivariant geometric structure. This newly proposed symmetry allows modular addition of different direction measurements and their extrinsic calibration while maintaining the ability to include bias states in the same symmetry. The subsequently proposed filter-based estimator using this symmetry noticeably improves the transient response, and the asymptotic bias and extrinsic calibration estimation compared to state-of-the-art approaches. The estimator is verified in statistically representative simulations and is tested in real-world experiments.