Data Reduction Methodology Research Articles

Past Developments and Current Advancements in Unsteady Pressure Measurements in Turbomachines

The aim of this paper is to review, summarize, and record long-term experience with development and application of aerodynamic probes with built-in miniature pressure transducers for unsteady pressure measurement and industrial research in turbomachine components. The focus of the first half of the paper is on the work performed at VZLU Prague, Czech Republic (Secs. 3–8). The latest development in unsteady pressure measurement techniques and data reduction methodology suitable for future research in highly loaded, high-speed turbine engine components performed at NASA GRC Cleveland, OH, is reported in Secs. 8–15 of this paper. Excellent reviews of similar activities at ETH Zürich, Switzerland by Kupferschmied, et al. (2000, “Time-Resolved Flow Measurements With Fast-Response Aerodynamic Probes in Turbomachines,” Meas. Sci. Technol., 11(7), pp. 1036–1054) and at VKI Rhode-Sain-Genèse, Belgium by Sieverding, et al. (2000, “Measurement Techniques for Unsteady Flows in Turbomachines,” Exp. Fluids, 28(4), pp. 285–321) were already reported and are acknowledged here. A short list of reported accomplishments achieved by other researchers at various laboratories is also reported for completeness. The authors apologize to those whose contributions are not reported here. It is just an unfortunate oversight, not an intentional omission.

Numerical modelling and inverse analysis of continuous compaction control

Abstract Assessing the dynamic properties of compacted materials placed in field remains a challenge. Currently, stiffness parameters of compacted fills are estimated by means of spot tests such as dry density measurement, load-plate or CBR field tests, and more recently, Continuous Compaction Control (CCC). Unfortunately, these methodologies are based on non-constitutive parameters and correlations. In this work, CCC is considered a dynamic field test that is useful to evaluate properties commonly used in earthworks design, namely: Young modulus, hysteretic damping, and Poisson’s ratio. Considering CCC load-displacement histories as an output of this field test, a parametric study within the framework of continuum mechanics could be performed to fit the CCC data test. However, a parametric study to solve such an inverse problem is time-consuming; and, moreover, it does not guarantee a proper solution. Therefore, this paper proposes a data reduction methodology that generates a solution of this inverse problem by using at least six numerical simulations within continuum mechanics. A Finite Differences code was used with a simplified version of Kelvin-Voigt viscoelastic model to solve the wave equation. In numerical simulations, field drum-soil load histories, extracted from literature, were applied to a 2D numerical soil model. Data from three CCC field tests were employed to test the usefulness and validity of the proposed data reduction methodology. Validations show its usefulness not only for full contact drum-soil case but also for the partial loss of contact. Although dynamic numerical simulations are time-consuming and depend on computer resources, real-time application is promising. This attempt of the evaluation of mechanical properties of compacted soils from CCC records shows the potential use of CCC as a dynamic field test for analysis and design of earthworks such as embankments and pavements.

Cohesive law identification of adhesive layers subject to shear load – An exact inverse solution

An exact general solution of the following inverse problem is obtained: given a couple of beams adhesively bonded along a surface parallel to their axes, subject to traction / flexure load, find the unknown interface shear force. This solution is used to identify the cohesive law that characterizes the behaviour of adhesive layers subject to shear load. In order to generate data to be used to evaluate the identification methodology, three decohesion virtual tests are performed by means of detailed FE simulations. The series of tests is related to standard test configurations, and shows the correctness of the inverse solution and the efficiency of the proposed methodology, as it is more precise than the data reduction methodologies provided by literature. If ad hoc test configurations are designed, this identification methodology can be applied to adhesion between different materials and to adhesive layers with variable behaviour.

Investigation of the thermal-hydraulic non-equilibrium in a 7 × 7 rod bundle during reflood

The current research aims at investigating the thermal–hydraulic non-equilibrium encountered in the dispersed flow film boiling (DFFB) regime under reflood conditions. A series of constant reflood tests have been performed at the 7 × 7 Rod Bundle Heat Transfer (RBHT) test facility and the experimental results have been analyzed in detail. The data not only is useful for the development of theoretical models for two-phase interfacial mass and heat transfer, void fraction, pressure drop, and rod bundle cooling prediction, but also can be used as a benchmark data base for evaluating the performance of various thermal–hydraulic analysis codes. In this paper, a complete data reduction methodology is employed to reveal and interpret important two-phase flow phenomena during reflood transients. The results show that for the region far away from the quench front location, significant thermal non-equilibrium may exist during reflood and thus poor heat removal capability of the flow mixture is expected. On the other hand, for the region immediately downstream of the quench front, the two-phase flow is found to be close to the thermal equilibrium state, indicating that both the interfacial heat transfer and the heat transfer between the rod surface and fluid mixture are very efficient. In addition, based on the liquid droplet measurement and force balance calculations, it is found that the slip ratio between the two separate phases is a strong function of the droplet size and reflood time. With a larger droplet size and a shorter distance from the quench location, the slip ratio is larger. The liquid carryover fraction at the exit of the test section is also determined as a function of the reflood time. Results indicate that only a small portion of the injected coolant mass is stored within the bundle. A significant amount of liquid mass into the test section is either evaporated or entrained in the vapor flow and eventually left the bundle.

Determination of the crack resistance curve for intralaminar fiber tensile failure mode in polymer composites under high rate loading

This paper presents the determination of the crack resistance curve of the unidirectional carbon-epoxy composite material IM7-8552 for intralaminar fiber tensile failure under dynamic loading. The methodology, proposed by Catalanotti et al. (2014) for quasi-static loading conditions, was enhanced to high rate loading in the order of about 60 s−1. Dynamic tests were performed using a split-Hopkinson tension bar, while quasi-static reference tests were conducted on a standard electromechanical testing machine. Double-edge notched tension specimens of different sizes were tested to obtain the size effect law, which in combination with the concepts of the energy release rate is used to measure the entire crack resistance curve for the fiber tensile failure mode. Digital image correlation is applied to further verify the validity of the experiments performed at both static and dynamic loading. The data reduction methodology applied in this paper is suitable for intralaminar fiber failure modes without significant delamination. Sufficient proof is given that quasi-static fracture mechanics theory can also be used for the data reduction of the dynamic tests. It is shown, that the intralaminar fracture toughness for fiber tensile failure of UD IM7-8552 increases with increasing rate of loading.

Leadership in dentistry: findings from new tool to measure clinical leadership.

BackgroundIn England, the recent reorganization of the National Health Service has led to the development of local dental networks and an emerging narrative on the importance of clinical leadership in dentistry. Analogous to clinical commissioning groups, local dental networks ensure general dental practitioners (GDPs) influence the delivery of local services. However, little is known about what GDPs think clinical leadership is and whether the construct has meaning. The aim of this study was to explore the structure of a pilot questionnaire to determine the qualities that GDPs deem are important and to use a data reduction methodology to produce a tool to measure clinical leadership.MethodsA 61-item questionnaire was distributed to GDPs across the North West of England. GDPs were asked to rate the level of importance of each item using a 7-point Likert scale. Principal component analysis and direct oblimin rotation was used to examine for factor loadings within the questionnaire. Internal validity was tested by Cronbach’s alpha.ResultsTwo principle factors emerged: “how to lead” and “how not to lead”. Individually, the item “I think it is important to have integrity” was rated as the most important.ConclusionThe study developed a refined questionnaire that captures the important qualities of clinical leadership in dentistry. This is the first questionnaire that has been developed to capture important leadership attributes for GDPs.

Experimental Determination of the Boiling Heat Transfer Coefficients of R-134a and R-417A on a Smooth Copper Tube

Flooded evaporators are widely used as compact cooling units to cool liquids. They consist of a shell-and-tube heat exchanger, with the fluid to cool flowing inside the tubes of the bundle and a refrigerant that evaporates over those tubes. Pool boiling on the external surface of the tubes is a very complex process, and therefore the boiling heat transfer coefficients (HTCs) should be determined experimentally. Copper and copper alloys tubes are commonly employed in such heat exchangers, due to their high thermal conductivity and relative low cost. On the other hand, refrigeration and air conditioning sectors are undergoing significant changes caused mainly by the necessity of replacing existing refrigerants with more environmentally friendly ones. This paper reports the experimental determination of the pool boiling HTCs of R-134a and R-417A blend on a smooth copper tube of 18.87 mm diameter, at two saturation temperatures of 10°C and 7°C. Although smooth tubes are not commonly used in shell-and-tube evaporators nowadays, it is a first approach to pool boiling of drop-in refrigerants. The experimental setup and data acquisition are described, the experimental procedure is explained, the data reduction methodology is detailed, and the results are presented and discussed.

The Mopra Southern Galactic Plane CO Survey

AbstractWe present the first results from a new carbon monoxide (CO) survey of the southern Galactic plane being conducted with the Mopra radio telescope in Australia. The 12CO, 13CO, and C18O J = 1–0 lines are being mapped over the $l = 305^{\circ }\text{--} 345^{\circ }, b = \pm 0.5^{\circ }$ portion of the fourth quadrant of the Galaxy, at 35 arcsec spatial and 0.1 km s−1 spectral resolution. The survey is being undertaken with two principal science objectives: (i) to determine where and how molecular clouds are forming in the Galaxy and (ii) to probe the connection between molecular clouds and the ‘missing’ gas inferred from gamma-ray observations. We describe the motivation for the survey, the instrumentation and observing techniques being applied, and the data reduction and analysis methodology. In this paper, we present the data from the first degree surveyed, $l = 323^{\circ } \text{--} 324^{\circ }, b = \pm 0.5^{\circ }$. We compare the data to the previous CO survey of this region and present metrics quantifying the performance being achieved; the rms sensitivity per 0.1 km s−1 velocity channel is ~1.5 K for ${\rm ^{12}CO}$ and ~0.7 K for the other lines. We also present some results from the region surveyed, including line fluxes, column densities, molecular masses, ${\rm ^{12}CO/^{13}CO}$ line ratios, and ${\rm ^{12}CO}$ optical depths. We also examine how these quantities vary as a function of distance from the Sun when averaged over the 1 square degree survey area. Approximately 2 × 106M⊙ of molecular gas is found along the G323 sightline, with an average H2 number density of $n_{\text{H}_2} \sim 1$ cm−3 within the Solar circle. The CO data cubes will be made publicly available as they are published.

In situ x-ray diffraction of solution-derived ferroelectric thin films for quantitative phase and texture evolution measurement

An in situ measurement technique is developed and presented, which utilizes x-rays from a synchrotron source with a two-dimensional detector to measure thin film microstructural and crystallographic evolution during heating. A demonstration experiment is also shown wherein the measured diffraction patterns are used to describe phase and texture evolution during heating and crystallization of solution-derived thin films. The diffraction images are measured sequentially while heating the thin film with an infrared lamp. Data reduction methodologies and representations are also outlined to extract phase and texture information from the diffraction images as a function of time and temperature. These techniques and data reduction methods are demonstrated during crystallization of solution-derived lead zirconate titanate ferroelectric thin films heated at a rate of 30 °C/min and using an acquisition time of 8 s. During heating and crystallization, a PtxPb type phase was not observed. A pyrochlore phase was observed prior to the formation and growth of the perovskite phase. The final crystallized films are observed to have both 111 and 100 texture components. The in situ measurement methodology developed in this work allows for acquiring diffraction images in times as low as 0.25 s and can be used to investigate changes during crystallization at faster heating rates. Moreover, the experiments are shown to provide unique information during materials processing.

A novel perspective to high-speed cross-hot-wire calibration methodology

A practical cross-hot-wire calibration and data reduction methodology for instantaneous measurements of mass flux and flow angle is developed for two dimensional subsonic compressible flows. Historically, data reduction for flow conditions of 0.4 < M < 1.2 is regarded as problematic, even in the simplified case of flow normal mounted wires. Thus, in comparison with the incompressible and supersonic conditions, the literature addressing these flow regimes is quite limited. The present study addresses this void by relating the wire voltages to flow conditions through renormalized, Mach and overheating independent, nondimensional quantities. Therefore, a short and robust calibration can be performed in an unheated free jet facility with applicability toward a broad range of planar flow conditions. This disposes the need for typical closed loop calibration wind tunnels which vary flow velocity, density and temperature independently to parameterize the voltage dependency in a purely empirical manner.

In situ calibration of four-wire hot-wire probes for atmospheric measurement

An in situ calibration methodology to use hot-wire anemometry for the measurement of atmospheric flow without the need for prior calibration is presented. The application of this method is expected to facilitate the usage of hot-wire anemometry to study atmospheric turbulence structures with a higher temporal and spatial resolution compared to conventional methods, such as sonic anemometry. In this method, the hot-wire anemometer is calibrated after the field experiment using the velocity data acquired from a sonic anemometer operating simultaneously. In this paper, a proper data reduction methodology is developed to perform the in situ calibration and extract the desired velocity information. The feasibility of this in situ operation of hot-wire anemometry is tested in an atmospheric research facility in the coastal region of Doha, Qatar. The obtained turbulence data is then compared with the data obtained from the sonic anemometer. Results show a good agreement between the data from the hot-wire probe, obtained at higher sampling rate, with that of the sonic anemometer measurement. In addition, application of the hot-wire probe provides the added advantage of the higher spatial and temporal measurement resolution. Finally, sensitivity of the proposed method to random noise in the input voltage is then numerically analyzed using a Monte Carlo simulation.

Split Hopkinson Pressure Bar Data Reduction Methodology for Linear Materials with Memory

Abstract The classic split-Hopkinson pressure bar (SHPB) data reduction methodology is revisited. A complete one-dimensional analysis of the SHPB system is presented for linear-elastic and viscoelastic specimens, for which the specimen and bar diameters are equal. In general, the assumptions inherent in the classic SHPB data reduction method are found to be inconsistent. However, the classic SHPB data reduction scheme is applicable in the case of acoustically soft materials. These analyses are extended to explain major issues in the general linear elastic case, including materials with regular and singular memory. Exact expressions for the average stress and strain in the specimen and Fourier transform of the memory kernel function in terms of experimental parameters in the quasi-static limit are formulated. Dynamic adjustments associated with elastic and viscous relaxation processes are also derived.

Enhanced performance of fast-response 3-hole wedge probes for transonic flows in axial turbomachinery

The paper presents the development and application of a three-sensor wedge probe to measure unsteady aerodynamics in a transonic turbine. CFD has been used to perform a detailed uncertainty analysis related to probe-induced perturbations, in particular the separation zones appearing on the wedge apex. The effects of the Reynolds and Mach numbers are studied using both experimental data together with CFD simulations. The angular range of the probe and linearity of the calibration maps are enhanced with a novel zonal calibration technique, used for the first time in compressible flows. The data reduction methodology is explained and demonstrated with measurements performed in a single-stage high-pressure turbine mounted in the compression tube facility of the von Karman Institute. The turbine was operated at subsonic and transonic pressure ratios (2.4 and 5.1) for a Reynolds number of 106, representative of modern engine conditions. Complete maps of the unsteady flow angle and rotor outlet Mach number are documented. These data allow the study of secondary flows and rotor trailing edge shocks.

Data reduction methodologies for single fibre fragmentation test: Role of the interface and interphase

The single fibre fragmentation test (SFFT) is commonly used to characterise the fibre/matrix adhesion. In order to quantify the fibre/matrix adhesion the cumulative stress transfer function (CSTF) methodology was developed so that the elastoplasticity of the matrix could be included in the analysis through the plasticity-effect model [Tripathi D, Chen F, Jones FR. A comprehensive model to predict the stress fields in a single fibre composite. J Comp Mater 1996;30;1514–38., Tripathi D, Jones FR. Measurement of the load-bearing capability of the fibre/matrix interface by single fibre fragmentation. Comp Sci Technol 1997;57:925–35.] The limitations of this technique for the data reduction have been addressed by the use of the Plasticity Model to input the non-linearity of the matrix into methodology for fragmentation of a fibre in a matrix. An improved methodology, known as the revised cumulative stress transfer function (RCSTF) is described. The adhesion of a nanoscale plasma copolymer coated glass/epoxy system has been used to examine this approach to the fragmentation process. This methodology is also extended to account for the presence of an interphase. To validate the three phase model, carbon fibre coated with high and medium modulus epoxy resin were used to simulate fibre/interphase/matrix.

Analysis of an internally mountable accelerometer balance system for use with non-isotropic models in shock tunnels

Knowledge of drag force is an important design parameter in aerodynamics. Measurement of aerodynamic forces at hypersonic speed is a challenge and usually ground test facilities like shock tunnels are used to carry out such tests. Accelerometer based force balances are commonly employed for measuring aerodynamic drag around bodies in hypersonic shock tunnels. In this study, we present an analysis of the effect of model material on the performance of an accelerometer balance used for measurement of drag in impulse facilities. From the experimental studies performed on models constructed out of Bakelite HYLEM and Aluminum, it is clear that the rigid body assumption does not hold good during the short testing duration available in shock tunnels. This is notwithstanding the fact that the rubber bush used for supporting the model allows unconstrained motion of the model during the short testing time available in the shock tunnel. The vibrations induced in the model on impact loading in the shock tunnel are damped out in metallic model, resulting in a smooth acceleration signal, while the signal become noisy and non-linear when we use non-isotropic materials like Bakelite HYLEM. This also implies that careful analysis and proper data reduction methodologies are necessary for measuring aerodynamic drag for non-metallic models in shock tunnels. The results from the drag measurements carried out using a 60° half angle blunt cone is given in the present analysis.

Longitudinal heat conduction study of a uniform power density apparatus for the experimental determination of the heat transfer coefficient

A combined experimental and numerical analysis was performed to accurately evaluate the effect of longitudinal heat conduction along an aluminium test section on the local heat transfer coefficient (HTC) experimental determination. The test section contains a rectangular channel with fins typical of compact heat exchangers. The hydraulic diameter of the channel is around 2 mm. The fluid stream is heated by flat electrical resistances clamped to the outer walls of the test section. The test section contains four zones with different fin pads each, in order to be able to generate data for several geometries at the same time at exactly the same mass flow rate. It was found that longitudinal conduction can lead to a quite uneven distribution of the heat flux to the fluid at the beginning and end of each zone of the test section. Three phenomena were found to be the cause for the observed uneven heat distribution, i.e. the longitudinal gradient of temperature along the wall induced by the fluid temperature rise, the presence of heated and non-heated zones, and the stepwise non-uniformity of the HTC along the test section induced where the fin pad changes. The study has shown that the elementary data reduction methodology, assuming that the surface power density generated by the electrical resistance and the heat flux density reaching the fluid are equal and uniform along the channel, is too far from the reality at the beginning and end of each zone of the test section, especially at low mass flow rates.

Fully digital time differential perturbed angular correlation (TDPAC) spectrometer

A new generation time differential perturbed angular correlation (PAC) spectrometer has been designed and built. The design strategy and details of the data collection and reduction methodology are reported. First results obtained by the new spectrometer are reported and compared with PAC data obtained by more conventional means.

Determination of Cylindrical Soil Specimen Dimensions by Imaging with Application to Volume Change of Bentonite-Sand Mixtures

Abstract Volumetric shrinkage of compacted bentonite and sand mixtures has been continuously monitored at small strain levels (i.e., &amp;lt;5 %) using a digital image processing technique. A special digital measurement setup and a computer algorithm have been developed in order to identify volume of the drying specimens. Volume change of three compacted bentonite-sand mixtures at different initial moisture contents were recorded during drying by means of vernier caliper and digital measurements. Continuous monitoring of the volumetric shrinkage of specimens using digital images proved that digital measurement and data reduction methodology developed herein is capable of determining the shrinkage amount with desired accuracy. It is shown in the study that consistent volumetric shrinkage strain readings can be taken using this cost effective, nondestructive, and operator independent measurement setup, which may have become the preferred shrinkage measurement methodology in soil mechanics laboratory practice with some added features.

Flight data reduction methodology for performance evaluation and comparison of model-following adaptive control laws

AbstractEven small differences in atmospheric and/or flight conditions can potentially impact significantly the evaluation of the performance of the control laws and prevent a correct comparison, especially in the case of reduced size aircraft (autonomous or remotely piloted). Consistent deterministic control inputs can only be guaranteed through some form of computer-based on-board excitation system. In this paper, a methodology is proposed for flight data reduction with the purpose of accounting for non-homogeneous atmospheric conditions and inconsistent pilot inputs. The method is developed for the specific purpose of comparing model-following adaptive control laws. Performance evaluation parameters based on angular rate tracking errors are defined and used for the comparison. As a result of this approach, an additive correction is applied to the angular rate measurements to compensate for non-homogeneous turbulence effects. A multiplicative correction factor is applied to the angular rate tracking error to take into account non-identical pilot inputs. The procedure is validated with simulation and flight data obtained in the process of designing a set of fault tolerant control laws based on non-linear dynamic inversion with neural network augmentation for the reduced size WVU YF-22 aircraft model.

WE‐D‐L100J‐06: Ultrasonic Scatterer Size Estimations in Liver Tumor Differentiation

Purpose: To evaluate the utility of an ultrasound scatterer size estimation method (combined with B‐mode features) to differentiate liver hemangioma (benign) from malignant liver tumors in a clinical study. Method and Materials: Scatterer size is estimated from the frequency dependence of the backscatter coefficient, obtained using a reference phantom method. A tissue mimicking phantom containing glass beads randomly distributed in gel was scanned by a Siemens Antares scanner equipped with a linear array transducer to verify the scatterer size data reduction methodology prior to use in clinical determinations. Excised normal human liver tissues and in vivo liver hemangiomas and malignant tumors were evaluated using the methodology using either the Siemens Antares or GE Logic 9 scanners. The results were correlated with biopsy findings. Results: For power spectra estimation, Welch's average approach yields better results than a periodogram and an autoregressive approach. Averaging over 15 independent samples with a gating window length of around 10 wavelengths is desirable to obtain reasonable size estimates based on the trade off between spatial resolution and signal‐to‐noise ratio. Therefore, angular or elevational compounding was used for in vivo data acquisition. A liver hemanigomas exhibited larger effective scatterer sizes than surrounding normal liver tissues. Combining B‐mode features, such as a halo sign, with scatterer size estimates may be useful to confirm the benign or malignant classification. Conclusion: Ultrasound scatterer sizes estimated from frequency dependent backscatter properties may provide useful clinical information, not readily available in conventional ultrasound B‐mode images. Preliminary in vivo results suggest that it may be an effective processing method for distinguishing liver hemangiomas.