Academic literature on the topic 'Unsteady analytical test case'
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Journal articles on the topic "Unsteady analytical test case":
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Alexandrova, Irina V., and Dmitri V. Alexandrov. "Dynamics of particulate assemblages in metastable liquids: a test of theory with nucleation and growth kinetics." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2171 (April 13, 2020): 20190245. http://dx.doi.org/10.1098/rsta.2019.0245.
Abstract:
This manuscript is devoted to the nonlinear dynamics of particulate assemblages in metastable liquids, caused by various dynamical laws of crystal growth and nucleation kinetics. First of all, we compare the quasi-steady-state and unsteady-state growth rates of spherical crystals in supercooled and supersaturated liquids. It is demonstrated that the unsteady-state rates transform to the steady-state ones in a limiting case of fine particles. We show that the real crystals evolve slowly in a more actual case of unsteady-state growth laws. Various growth rates of particles are tested against experimental data in metastable liquids. It is demonstrated that the unsteady-state rates describe the nonlinear behaviour of experimental curves with increasing the growth time or supersaturation. Taking this into account, the crystal-size distribution function and metastability degree are analytically found and compared with experimental data on crystallization in inorganic and organic solutions. It is significant that the distribution function is shifted to smaller sizes of particles if we are dealing with the unsteady-state growth rates. In addition, a complete analytical solution constructed in a parametric form is simplified in the case of small fluctuations in particle growth rates. In this case, a desupercooling/desupersaturation law is derived in an explicit form. Special attention is devoted to the biomedical applications for insulin and protein crystallization. This article is part of the theme issue ‘Patterns in soft and biological matters’.
2
Sbardella, L., and M. Imregun. "Linearized Unsteady Viscous Turbomachinery Flows Using Hybrid Grids." Journal of Turbomachinery 123, no. 3 (February 1, 2001): 568–82. http://dx.doi.org/10.1115/1.1371777.
Abstract:
The paper describes the theory and the numerical implementation of a three-dimensional finite volume scheme for the solution of the linearized, unsteady Favre-averaged Navier–Stokes equations for turbomachinery applications. A further feature is the use of mixed element grids, consisting of triangles and quadrilaterals in two dimensions, and of tetrahedra, triangular prisms, and hexahedra in three dimensions. The linearized unsteady viscous flow equations are derived by assuming small harmonic perturbations from a steady-state flow and the resulting equations are solved using a pseudo-time marching technique. Such an approach enables the same numerical algorithm to be used for both the nonlinear steady and the linearized unsteady flow computations. The important features of the work are the discretization of the flow domain via a single, unified edge-data structure for mixed element meshes, the use of a Laplacian operator, which results in a nearest neighbor stencil, and the full linearization of the Spalart–Allmaras turbulence model. Four different test cases are presented for the validation of the proposed method. The first one is a comparison against the classical subsonic flat plate cascade theory, the so-called LINSUB benchmark. The aim of the second test case is to check the computational results against the asymptotic analytical solution derived by Lighthill for an unsteady laminar flow. The third test case examines the implications of using inviscid, frozen-turbulence, and fully turbulent models when linearizing the unsteady flow over a transonic turbine blade, the so-called 11th International Standard Configuration. The final test case is a rotor/stator interaction, which not only checks the validity of the formulation for a three-dimensional example, but also highlights other issues, such as the need to linearize the wall functions. Detailed comparisons were carried out against measured steady and unsteady flow data for the last two cases and good overall agreement was obtained.
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Duarte, A. S. R., A. I. P. Miranda, and P. J. Oliveira. "Numerical and analytical modeling of unsteady viscoelastic flows: The start-up and pulsating test case problems." Journal of Non-Newtonian Fluid Mechanics 154, no. 2-3 (October 2008): 153–69. http://dx.doi.org/10.1016/j.jnnfm.2008.04.009.
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Boutet, Johan, and Grigorios Dimitriadis. "Unsteady Lifting Line Theory Using the Wagner Function for the Aerodynamic and Aeroelastic Modeling of 3D Wings." Aerospace 5, no. 3 (September 1, 2018): 92. http://dx.doi.org/10.3390/aerospace5030092.
Abstract:
A method is presented to model the incompressible, attached, unsteady lift and pitching moment acting on a thin three-dimensional wing in the time domain. The model is based on the combination of Wagner theory and lifting line theory through the unsteady Kutta–Joukowski theorem. The results are a set of closed-form linear ordinary differential equations that can be solved analytically or using a Runge–Kutta–Fehlberg algorithm. The method is validated against numerical predictions from an unsteady vortex lattice method for rectangular and tapered wings undergoing step or oscillatory changes in plunge or pitch. Further validation is demonstrated on an aeroelastic test case of a rigid rectangular finite wing with pitch and plunge degrees of freedom.
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Casper, J., and F. Farassat. "A New Time Domain Formulation for Broadband Noise Predictions." International Journal of Aeroacoustics 1, no. 3 (September 2002): 207–40. http://dx.doi.org/10.1260/147547202320962574.
Abstract:
A new analytic result in acoustics called “Formulation 1B,” proposed by Farassat, is used to compute the loading noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Williams-Hawkings equation with the loading source term. The formulation contains a far field surface integral that depends on the time derivative and the surface gradient of the pressure on the airfoil, as well as a contour integral on the boundary of the airfoil surface. As a first test case, the new formulation is used to compute the noise radiated from a flat plate, moving through a sinusoidal gust of constant frequency. The unsteady surface pressure for this test case is analytically specied from a result based on linear airfoil theory. This test case is used to examine the velocity scaling properties of Formulation 1B and to demonstrate its equivalence to Formulation 1A of Farassat. The new acoustic formulation, again with an analytic surface pressure, is then used to predict broadband noise radiated from an airfoil immersed in homogeneous, isotropic turbulence. The results are compared with experimental data previously reported by Paterson and Amiet. Good agreement between predictions and measurements is obtained. Finally, an alternative form of Formulation 1B is described for statistical analysis of broadband noise.
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Bitter, Martin, Michael Hilfer, Tobias Schubert, Christian Klein, and Reinhard Niehuis. "An Ultra-Fast TSP on a CNT Heating Layer for Unsteady Temperature and Heat Flux Measurements in Subsonic Flows." Sensors 22, no. 2 (January 15, 2022): 657. http://dx.doi.org/10.3390/s22020657.
Abstract:
In this paper, the authors demonstrate the application of a modified Ru(phen)-based temperature-sensitive paint which was originally developed for the evaluation of unsteady aero-thermodynamic phenomena in high Mach number but short duration experiments. In the present work, the modified TSP with a temperature sensitivity of up to −5.6%/K was applied in a low Mach number long-duration test case in a low-pressure environment. For the demonstration of the paint’s performance, a flat plate with a mounted cylinder was set up in the High-Speed Cascade Wind Tunnel (HGK). The test case was designed to generate vortex shedding frequencies up to 4300 Hz which were sampled using a high-speed camera at 40 kHz frame rate to resolve unsteady surface temperature fields for potential heat-transfer estimations. The experiments were carried out at reduced ambient pressure of p∞ = 13.8 kPa for three inflow Mach numbers being Ma∞=[0.3;0.5;0.7]. In order to enable the resolution of very low temperature fluctuations down to the noise floor of 10−5 K with high spatial and temporal resolution, the flat plate model was equipped with a sprayable carbon nanotube (CNT) heating layer. This constellation, together with the thermal sensors incorporated in the model, allowed for the calculation of a quasi-heat-transfer coefficient from the surface temperature fields. Besides the results of the experiments, the paper highlights the properties of the modified TSP as well as the methodology.
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ANTUONO, MATTEO, ANDREW J. HOGG, and MAURIZIO BROCCHINI. "The early stages of shallow flows in an inclined flume." Journal of Fluid Mechanics 633 (August 25, 2009): 285–309. http://dx.doi.org/10.1017/s0022112009007034.
Abstract:
The motion of an initially quiescent shallow layer of fluid within an impulsively tilted flume is modelled using the nonlinear shallow water equations. Analytical solutions for the two-dimensional flow are constructed using the method of characteristics and, in regions where neither of the characteristic variables is constant, by adopting hodograph variables and using the Riemann construction for the solution. These solutions reveal that the motion is strongly influenced by the impermeable endwalls of the flume. They show that discontinuous solutions emerge after some period following the initiation of the flow and that for sufficiently long flumes there is a moving interface between wetted and dry regions. Using the hodograph variables we are able to track the evolution of the flow analytically. After the discontinuities develop, we also calculate the velocity and height fields by using jump conditions to express conservation of mass and momentum across the shock and thus we show how the hydraulic jump moves within the domain and how its magnitude grows. In addition to providing the behaviour of the flow in this physical scenario, this unsteady solution also provides an important test case for numerical algorithms designed to integrate the shallow water equations.
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BROOK, B. S., S. A. E. G. FALLE, and T. J. PEDLEY. "Numerical solutions for unsteady gravity-driven flows in collapsible tubes: evolution and roll-wave instability of a steady state." Journal of Fluid Mechanics 396 (October 10, 1999): 223–56. http://dx.doi.org/10.1017/s0022112099006084.
Abstract:
Unsteady flow in collapsible tubes has been widely studied for a number of different physiological applications; the principal motivation for the work of this paper is the study of blood flow in the jugular vein of an upright, long-necked subject (a giraffe). The one-dimensional equations governing gravity- or pressure-driven flow in collapsible tubes have been solved in the past using finite-difference (MacCormack) methods. Such schemes, however, produce numerical artifacts near discontinuities such as elastic jumps. This paper describes a numerical scheme developed to solve the one-dimensional equations using a more accurate upwind finite volume (Godunov) scheme that has been used successfully in gas dynamics and shallow water wave problems. The adapatation of the Godunov method to the present application is non-trivial due to the highly nonlinear nature of the pressure–area relation for collapsible tubes.The code is tested by comparing both unsteady and converged solutions with analytical solutions where available. Further tests include comparison with solutions obtained from MacCormack methods which illustrate the accuracy of the present method.Finally the possibility of roll waves occurring in collapsible tubes is also considered, both as a test case for the scheme and as an interesting phenomenon in its own right, arising out of the similarity of the collapsible tube equations to those governing shallow water flow.
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Joseph, Jeffrey A., and Leonard F. Koederitz. "Unsteady-State Spherical Flow With Storage and Skin." Society of Petroleum Engineers Journal 25, no. 06 (December 1, 1985): 804–22. http://dx.doi.org/10.2118/12950-pa.
Abstract:
Abstract This paper presents short-time interpretation methods for radial-spherical (or radial-hemispherical) flow in homogeneous and isotropic reservoirs inclusive of wellbore storage, wellbore phase redistribution, and damage skin effects. New dimensionless groups are introduced to facilitate the classic transformation from radial flow in the sphere to linear flow in the rod. Analytical expressions, type curves (in log-log and semilog format), and tabulated solutions are presented, both in terms of pressure and rate, for all flow problems considered. A new empirical equation to estimate the duration of wellbore and near-wellbore effects under spherical flow is also proposed. Introduction The majority of the reported research on unsteady-state flow theory applicable to well testing usually assumes a cylindrical (typically a radial-cylindrical) flow profile because this condition is valid for many test situations. Certain well tests, however, are better modeled by assuming a spherical flow symmetry (e.g., wireline formation testing, vertical interference testing, and perhaps even some tests conducted in wellbores that do not fully penetrate the productive horizon or are selectively penetrate the productive horizon or are selectively completed). Plugged perforations or blockage of a large part of an openhole interval may also promote spherical flow. Numerous solutions are available in the literature for almost every conceivable cylindrical flow problem; unfortunately, the companion spherical problem has not received as much attention, and comparatively few papers have been published on this topic. papers have been published on this topic. The most common inner boundary condition in well test analysis is that of a constant production rate. But with the advent of downhole tools capable of the simultaneous measurement of pressures and flow rates, this idealized inner boundary condition has been refined and more sophisticated models have been proposed. Therefore, similar methods must be developed for spherical flow analysis, especially for short-time interpretations. This general problem has recently been addressed elsewhere. Theory The fundamental linear partial differential equation (PDE) describing fluid flow in an infinite medium characterized by a radial-spherical symmetry is (1) The assumptions incorporated into this diffusion equation are similar to those imposed on the radial-cylindrical diffusivity equation and are discussed at length in Ref. 9. In solving Eq. 1, the classic approach is illustrated by Carslaw and Jaeger (later used by Chatas, and Brigham et al.). According to Carslaw and Jaeger, mapping b=pr will always reduce the problem of radial flow in the sphere (Eq. 1) to an equivalent problem of linear flow in the rod for which general solutions are usually known. (For example, see Ref. 17 for particular solutions in petroleum applications.) Note that in this study, we assumed that the medium is spherically isotropic; hence k in Eq. 1 is the constant spherical permeability. This assumption, however, does not preclude analysis in systems possessing simple anisotropy (i.e., uniform but unequal horizontal and vertical permeability components). In this case, k as used in this paper should be replaced by k, an equivalent or average (but constant) spherical permeability. Chatas presented a suitable expression (his Eq. 10) obtained presented a suitable expression (his Eq. 10) obtained from a volume integral. It is desirable to transform Eq. 1 to a nondimensional form, thereby rendering its applicability universal. The following new, dimensionless groups accomplish this and have the added feature that solutions are obtained directly in terms of the dimensionless pressure drop, PD, not the usual b (or bD) groups. ......................(2) .......................(3) .........................(4) The quantity rsw is an equivalent or pseudospherical wellbore radius used to represent the actual cylindrical sink (or source) of radius rw. SPEJ p. 804
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Ayton, Lorna J. "Analytic solution for aerodynamic noise generated by plates with spanwise-varying trailing edges." Journal of Fluid Mechanics 849 (June 21, 2018): 448–66. http://dx.doi.org/10.1017/jfm.2018.431.
Abstract:
This paper presents an analytic solution for aerodynamic noise generated by an unsteady wall pressure gust interacting with a spanwise-variable trailing edge in a background steady uniform flow. Viscous and nonlinear effects are neglected. The Wiener–Hopf method is used in conjunction with a non-orthogonal coordinate transformation and separation of variables to permit analytical progress. The solution is obtained in terms of a tailored modal expansion in the spanwise coordinate; however, only finitely many modes are cut-on, therefore the far-field noise can be quickly evaluated. The solution gives insight into the potential mechanisms behind the reduction of noise for plates with serrated trailing edges compared to those with straight edges. The two mechanisms behind the noise reduction are an increased destructive interference in the far field, and a redistribution of acoustic energy from low cut-on modes to higher cut-off modes. Five different test-case trailing-edge geometries are considered. The analytic solution identifies which geometries are most effective in different frequency ranges: geometries which promote destructive interference are best at low frequencies, whilst geometries which promote a redistribution of energy are better at high frequencies.
Dissertations / Theses on the topic "Unsteady analytical test case":
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Regnault, Paul. "Front-Tracking mesh adaptation for the simulation of two-phase flows with coalescence and breakup." Electronic Thesis or Diss., Université Gustave Eiffel, 2023. http://www.theses.fr/2023UEFL2076.
Abstract:
Dans le cadre des écoulements diphasiques à phases séparées, ce travail porte sur la gestion dynamique du maillage de l'interface (constitué de triangles en 3D) et son impact sur l'approximation des propriétés géométriques que sont la position et la courbure. Les équations de conservation de la mécanique des fluides sont résolues sur des grille fixes, décalées et structurées. L'interface est suivie de façon lagrangienne au cours du temps avec un maillage mobile et déformable : on parle de méthode de type « Front-Tracking ». En plus des opérations de remaillage classiques (suppression et échange d'arêtes, insertion de sommets notamment), on étudiera l'adaptation du maillage à la courbure de l'interface et l'utilisation d'une approximation polynomiale pour améliorer l'insertion de sommets ou la suppression d'arêtes. Ces méthodes sont évaluées sur des surfaces analytiques mobiles et déformables, sans résolution des équations de Navier-Stokes ni changement topologique. Dans les écoulements diphasiques, des changements topologiques peuvent avoir lieu : la coalescence et la rupture. Nous proposons une méthode de coalescence et une méthode de rupture d'interface. Ces deux méthodes sont activées selon des critères de distance et sont basées uniquement sur le maillage de l'interface, sans recourir au maillage eulérien. Ces méthodes sont utilisées sur des configurations numériques et expérimentales de la littérature pour apprécier leur robustesse et leurs performancesIn the context of two-phase flows with separated phases, this work focuses on dynamic management of the interface mesh (made up of connected triangles in 3D) and its impact on the approximation of geometrical properties that are position and curvature. The conservation equations of fluid mechanics are solved on fixed, staggered and structured grids. The interface is tracked in a Lagrangian fashion with a moving and deformable mesh: this method is known as the"Front-tracking" method. In addition to classical remeshing operations (edgesplitting, collapsing and swapping for instance), we will study the adaptation of the mesh to the curvature of the interface and the use of polynomial approximation to improve edge splitting and collapsing. These methods are evaluated on analytical, mobile and deformable surfaces, with neither the resolution of the Navier-Stokes equations nor topological changes. In two-phaseflows, topological changes may happen: coalescence and breakup. We propose a method for coalescence and a method for breakup. These two methods are activated by distance criteria and rely only on the interface mesh, without resorting to the Eulerian mesh. These methods are employed on numerical and experimental configurations from the literature to appreciate their robustness and performances
Books on the topic "Unsteady analytical test case":
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United States. National Aeronautics and Space Administration., ed. Test of the semi-analytical case 1 and Gelbstoff case 2 SeaWiFS algorithm with a global data set. [Washington, DC: National Aeronautics and Space Administration, 1997.
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United States. National Aeronautics and Space Administration., ed. Test of the semi-analytical case 1 and Gelbstoff case 2 SeaWiFS algorithm with a global data set. [Washington, DC: National Aeronautics and Space Administration, 1997.
3
United States. National Aeronautics and Space Administration., ed. Test of the semi-analytical case 1 and Gelbstoff case 2 SeaWiFS algorithm with a global data set. [Washington, DC: National Aeronautics and Space Administration, 1997.
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United States. National Aeronautics and Space Administration., ed. Test of the semi-analytical case 1 and Gelbstoff case 2 SeaWiFS algorithm with a global data set. [Washington, DC: National Aeronautics and Space Administration, 1997.
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Ejeckam, R. B. Use of petrochemistry to infer tectonic origin of granitoid rocks: A test case using AECL's chemical samples from the Atikokan and Whiteshell research areas. Pinawa, Man: Whiteshell Laboratories, 1997.
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Rose, Nathan. Motorcycle Accident Reconstruction. 2nd ed. SAE International, 2022. http://dx.doi.org/10.4271/9781468603989.
Abstract:
Accident reconstruction utilizes principles of physics and empirical data to analyze the physical, electronic, video, audio, and testimonial evidence from a crash, to determine how and why the crash occurred, how the crash could have been avoided, or to determine whose description of the crash is most accurate. This process draws together aspects of mathematics, physics, engineering, materials science, human factors, and psychology, and combines analytical models with empirical test data. Different types of crashes produce different types of evidence and call for different analysis methods. Still, the basic philosophical approach of the reconstructionist is the same from crash type to crash type, as are the physical principles that are brought to bear on the analysis. This book covers a basic approach to accident reconstruction, including the underlying physical principles that are used, then details how this approach and the principles are applied when reconstructing motorcycle crashes. This second edition of Motorcycle Accident Reconstruction presents a thorough, systematic, and scientific overview of the available methods for reconstructing motorcycle crashes. This new edition contains: Additional theoretical models, examples, case studies, and test data. An updated bibliography incorporating the newest studies in the field. Expanded coverage of the braking capabilities of motorcyclists. Updated, refined, and expanded discussion of the decelerations of motorcycles sliding on the ground. A thoroughly rewritten and expanded discussion of motorcycle impacts with passenger vehicles. Updated coefficients of restitution for collisions between motorcycles and cars. A new and expanded discussion of using passenger car EDR data in motorcycle accident reconstruction. A new section covering recently published research on post-collision frozen speedometer readings on motorcycles. A new section on motorcycle interactions with potholes, roadway deterioration, and debris and expanded coverage of motorcycle falls. This second edition of Motorcycle Accident Reconstruction is a must-have title for accident reconstructionists, forensic engineers, and all interested in understanding why and how motorcycle crashes occur.
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Zydroń, Tymoteusz. Wpływ systemów korzeniowych wybranych gatunków drzew na przyrost wytrzymałości gruntu na ścinanie. Publishing House of the University of Agriculture in Krakow, 2019. http://dx.doi.org/10.15576/978-83-66602-46-5.
Abstract:
The aim of the paper was to determine the influence of root systems of chosen tree species found in the Polish Flysch Carpathians on the increase of soil shear strength (root cohesion) in terms of slope stability. The paper's goal was achieved through comprehensive tests on root systems of eight relatively common in the Polish Flysch Carpathians tree species. The tests that were carried out included field work, laboratory work and analytical calculations. As part of the field work, the root area ratio (A IA) of the roots was determined using the method of profiling the walls of the trench at a distance of about 1.0 m from the tree trunk. The width of the. trenches was about 1.0 m, and their depth depended on the ground conditions and ranged from 0.6 to 1.0 m below the ground level. After preparing the walls of the trench, the profile was divided into vertical layers with a height of 0.1 m, within which root diameters were measured. Roots with diameters from 1 to 10 mm were taken into consideration in root area ratio calculations in accordance with the generally accepted methodology for this type of tests. These measurements were made in Biegnik (silver fir), Ropica Polska (silver birch, black locust) and Szymbark (silver birch, European beech, European hornbeam, silver fir, sycamore maple, Scots pine, European spruce) located near Gorlice (The Low Beskids) in areas with unplanned forest management. In case of each tested tree species the samples of roots were taken, transported to the laboratory and then saturated with water for at least one day. Before testing the samples were obtained from the water and stretched in a. tensile testing machine in order to determine their tensile strength and flexibility. In general, over 2200 root samples were tested. The results of tests on root area ratio of root systems and their tensile strength were used to determine the value of increase in shear strength of the soils, called root cohesion. To this purpose a classic Wu-Waldron calculation model was used as well as two types of bundle models, the so called static model (Fiber Bundle Model — FIRM, FBM2, FBM3) and the deformation model (Root Bundle Model— RBM1, RBM2, mRBM1) that differ in terms of the assumptions concerning the way the tensile force is distributed to the roots as well as the range of parameters taken into account during calculations. The stability analysis of 8 landslides in forest areas of Cicikowicleie and Wignickie Foothills was a form of verification of relevance of the obtained calculation results. The results of tests on root area ratio in the profile showed that, as expected, the number of roots in the soil profile and their ApIA values are very variable. It was shown that the values of the root area ratio of the tested tree species with a diameter 1-10 ram are a maximum of 0.8% close to the surface of the ground and they decrease along with the depth reaching the values at least one order of magnitude lower than close to the surface at the depth 0.5-1.0 m below the ground level. Average values of the root area ratio within the soil profile were from 0.05 to 0.13% adequately for Scots pine and European beech. The measured values of the root area ratio are relatively low in relation to the values of this parameter given in literature, which is probably connected with great cohesiveness of the soils and the fact that there were a lot of rock fragments in the soil, where the tests were carried out. Calculation results of the Gale-Grigal function indicate that a distribution of roots in the soil profile is similar for the tested species, apart from the silver fir from Bie§nik and European hornbeam. Considering the number of roots, their distribution in the soil profile and the root area ratio it appears that — considering slope stability — the root systems of European beech and black locust are the most optimal, which coincides with tests results given in literature. The results of tensile strength tests showed that the roots of the tested tree species have different tensile strength. The roots of European beech and European hornbeam had high tensile strength, whereas the roots of conifers and silver birch in deciduous trees — low. The analysis of test results also showed that the roots of the studied tree species are characterized by high variability of mechanical properties. The values Of shear strength increase are mainly related to the number and size (diameter) of the roots in the soil profile as well as their tensile strength and pullout resistance, although they can also result from the used calculation method (calculation model). The tests showed that the distribution of roots in the soil and their tensile strength are characterized by large variability, which allows the conclusion that using typical geotechnical calculations, which take into consideration the role of root systems is exposed to a high risk of overestimating their influence on the soil reinforcement. hence, while determining or assuming the increase in shear strength of soil reinforced with roots (root cohesion) for design calculations, a conservative (careful) approach that includes the most unfavourable values of this parameter should be used. Tests showed that the values of shear strength increase of the soil reinforced with roots calculated using Wu-Waldron model in extreme cases are three times higher than the values calculated using bundle models. In general, the most conservative calculation results of the shear strength increase were obtained using deformation bundle models: RBM2 (RBMw) or mRBM1. RBM2 model considers the variability of strength characteristics of soils described by Weibull survival function and in most cases gives the lowest values of the shear strength increase, which usually constitute 50% of the values of shear strength increase determined using classic Wu-Waldron model. Whereas the second model (mRBM1.) considers averaged values of roots strength parameters as well as the possibility that two main mechanism of destruction of a root bundle - rupture and pulling out - can occur at the same. time. The values of shear strength increase calculated using this model were the lowest in case of beech and hornbeam roots, which had high tensile strength. It indicates that in the surface part of the profile (down to 0.2 m below the ground level), primarily in case of deciduous trees, the main mechanism of failure of the root bundle will be pulling out. However, this model requires the knowledge of a much greater number of geometrical parameters of roots and geotechnical parameters of soil, and additionally it is very sensitive to input data. Therefore, it seems practical to use the RBM2 model to assess the influence of roots on the soil shear strength increase, and in order to obtain safe results of calculations in the surface part of the profile, the Weibull shape coefficient equal to 1.0 can be assumed. On the other hand, the Wu-Waldron model can be used for the initial assessment of the shear strength increase of soil reinforced with roots in the situation, where the deformation properties of the root system and its interaction with the soil are not considered, although the values of the shear strength increase calculated using this model should be corrected and reduced by half. Test results indicate that in terms of slope stability the root systems of beech and hornbeam have the most favourable properties - their maximum effect of soil reinforcement in the profile to the depth of 0.5 m does not usually exceed 30 kPa, and to the depth of 1 m - 20 kPa. The root systems of conifers have the least impact on the slope reinforcement, usually increasing the soil shear strength by less than 5 kPa. These values coincide to a large extent with the range of shear strength increase obtained from the direct shear test as well as results of stability analysis given in literature and carried out as part of this work. The analysis of the literature indicates that the methods of measuring tree's root systems as well as their interpretation are very different, which often limits the possibilities of comparing test results. This indicates the need to systematize this type of tests and for this purpose a root distribution model (RDM) can be used, which can be integrated with any deformation bundle model (RBM). A combination of these two calculation models allows the range of soil reinforcement around trees to be determined and this information might be used in practice, while planning bioengineering procedures in areas exposed to surface mass movements. The functionality of this solution can be increased by considering the dynamics of plant develop¬ment in the calculations. This, however, requires conducting this type of research in order to obtain more data.
Book chapters on the topic "Unsteady analytical test case":
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Acosta, Griselda, Eric Smith, and Vladik Kreinovich. "Case When Analytical Techniques Invalidate the Conclusions of Data Mining: Reversed Flynn Effect of Decreasing IQ Test Scores." In Studies in Systems, Decision and Control, 47–52. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-46413-4_10.
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Azizi, Anaita. "From Social Media to Social Change: Online Platforms’ Impact on Kazakhstan’s Feminist and Civil Activisms." In Securitization and Democracy in Eurasia, 217–28. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-16659-4_14.
Abstract:
AbstractThe present study investigates the landscapes of feminist and civil activist movements in Kazakhstan and how these movements further developed and interacted after 2019. Given Kazakhstan’s authoritarian system of governance, social media plays a crucial role in the development of activist movements as it allows for faster and effective community mobilisation. The paper employs “the logic of connective action” concept as a theoretical basis to explore how social media has impacted the activist movement growth. The study is divided into two analytical parts: inductive and deductive. Inductive analysis is based on qualitative interviews and dedicated to exploring the goals, strategies, and challenges of feminist and activist movements, identifying the main actors, and pinpointing the movements’ interactions. The inductive analysis concludes with the proposition of the hypothesis that local cyberfeminist activism increases women’s involvement in activities dedicated to causes other than feminist one. The deductive analysis attempts to test this hypothesis via a survey developed for the present study. The paper concludes with a discussion section that summarises how feminist activism strengthens other activist movements and how the present case study can be expanded to other Central Asian states.
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Yehia Zakaria, Mohamed. "Unsteady Aerodynamics of Highly Maneuvering Flyers." In Biomimetics. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.94231.
Abstract:
In this chapter, a set of analytical aerodynamic models, based on potential flow, that can be used to predict the unsteady lift response during pitching maneuvers are presented and assessed. The result examines the unsteady lift coefficients experienced by a flat plate in high-amplitude pitch ramp motion. The pitch ramps are chosen based on two ramp pitch maneuvers of a maximum amplitudes of 25 and 45 degrees starting from zero degree. The aim is investigate the use of such classical models in predicting the lift dynamics compared to a full physical-based model. Among all classical methods used, the unsteady vortex lattice method (without considering the leading edge vortex) is found to be a very good predictor of the motion lift dynamic response for the 25 ° ramp angle case. However, at high pitch maneuvers (i.e.,the 45 ° ramp angle case), could preserve the response pattern with attenuated amplitudes without high computational burden. These mathematical analytical models presented in this chapter can be used to obtain a fast estimate for aircraft unsteady lift during pitch maneuvers instead of high fidelity models, especially in the early design phases.
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"28 Test case No 30: Unsteady cavitation in a Venturi type section(PN)." In Validation of Advanced Computational Methods for Multiphase Flow. Begell House Inc., 2005. http://dx.doi.org/10.1615/1-56700-218-8.234.
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Harris, Harriet A. "Does Analytical Philosophy Clip our Wings? Reformed Epistemology as a Test Case." In Faith and Philosophical Analysis, 100–118. Routledge, 2019. http://dx.doi.org/10.4324/9781315255521-8.
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Green, Ulrike Matthies, and Kirk E. Costion. "Conclusion." In Modeling Cross-Cultural Interaction in Ancient Borderlands. University Press of Florida, 2018. http://dx.doi.org/10.5744/florida/9780813056883.003.0009.
Abstract:
The primary goal of this volume was to test the effectiveness Cross-Cultural Interaction Model (CCIM) in various cultural contexts and time periods. Each of the volume’s case studies successfully adapted the model to their data demonstrating the flexible nature of the CCIM. Some scholars applied the model to their data as it was originally designed, while others made substantial changes in order to adapt the model to the idiosyncrasies of their cultural context. This chapter succinctly reviews the results of each individual case study and the contributions they made to strengthen CCIM for future application. One of the most important conclusions to come from the testing of the CCIM is that this process demonstrated the analytical power of a graphic model of cultural interaction which can trigger new perspectives or the identification of overlooked aspects of a thoroughly studied cultural interaction.
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Bäck, Thomas. "Artificial Landscapes." In Evolutionary Algorithms in Theory and Practice. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195099713.003.0008.
Abstract:
In order to facilitate an empirical comparison of the performance of Evolution Strategies, Evolutionary Programming, and Genetic Algorithms, a test environment for these algorithms must be provided in the form of several objective functions f : IRn → IR. Finding an appropriate and representative set of test problems is not an easy task, since any particular combination of properties represented by a test function does not allow for generalized performance statements. However, there is evidence from a vast number of applications that Evolutionary Algorithms are robust in the sense that they give reasonable performance over a wide range of different topologies. Here, a set of test functions that are completely artificial and simple is used, i.e., they are stated in a closed, analytical form and have no direct background from any practical application. Instead, they allow for a detailed analysis of certain special characteristics of the topology, e.g. unimodality or multimodality, continuous or discontinuous cases, and others. If any prediction is drawn up for the behavior of Evolutionary Algorithms depending on such strong topological characteristics, the appropriate idealized test function provides a good instrument to test such hypotheses. Furthermore, since many known test sets have some functions in common, at least a minimal level of comparability of results is often guaranteed. Finally, before we can expect an algorithm to be successful in the case of hard problems, it has to demonstrate that it does not fail to work on simple problems. On the other hand, the (public relations) effect of using artificial topologies is vanishingly small, since the test functions used are of no industrial relevance. This way, researchers working with such test functions can never rest on their industrial laurels. A more legitimate objection against artificial topologies may be that they are possibly not representative of the “average complexity” of real-world problems, and that some regularity features of their topology may inadmissibly speed up the search. However, most test function sets incorporate even multimodal functions of remarkable complexity, such that only the regularity argument counts against using an artifical function set.
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Karatas, Mumtaz, Nasuh Razi, and Hakan Tozan. "Assessing the Performance of a SAR Boat Location-Allocation Plan via Simulation." In Improving the Safety and Efficiency of Emergency Services, 142–78. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-2535-7.ch007.
Abstract:
Maritime search and rescue (SAR) operation is a critical process that aims to minimize the loss of life, injury, and material damage by rendering aid to persons in distress or imminent danger at sea. Optimal allocation of SAR vessels is a strategic level process that is to be carried out with a plan to react rapidly. This chapter seeks to evaluate the performance of a SAR boat location plan using simulation. The proposed methodology in this chapter works in two stages: First, an optimal allocation scheme of SAR resources is determined via a multi-objective mathematical model. Next, simulation is used to test the performance of the analytical solution under stochastic demand. With the heaviest traffic and maritime risk, the methodology is applied to a case study in the Aegean Sea.
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Karatas, Mumtaz, Nasuh Razi, and Hakan Tozan. "Assessing the Performance of a SAR Boat Location-Allocation Plan via Simulation." In Operations Research for Military Organizations, 67–97. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-5513-1.ch004.
Abstract:
Maritime search and rescue (SAR) operation is a critical process that aims to minimize the loss of life, injury, and material damage by rendering aid to persons in distress or imminent danger at sea. Optimal allocation of SAR vessels is a strategic level process that is to be carried out with a plan to react rapidly. This chapter seeks to evaluate the performance of a SAR boat location plan using simulation. The proposed methodology in this chapter works in two stages: First, an optimal allocation scheme of SAR resources is determined via a multi-objective mathematical model. Next, simulation is used to test the performance of the analytical solution under stochastic demand. With the heaviest traffic and maritime risk, the methodology is applied to a case study in the Aegean Sea.
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Stapleton, Jane. "Conceptual Interplay between Elements of the Tort of Negligence." In Three Essays on Torts, 65–101. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192893734.003.0003.
Abstract:
Chapter 3 examines how elements of the tort of negligence interact in critical conceptual ways and suggests that re-conceptualisation of aspects of those elements offers a more transparent and coherent framework. One argument is that a but-for concept of factual causation is inadequate and narrower than the concept evident in case law, one which can be identified by an ‘extended but-for test’. Another is that use of causal language at the analytical stage, which addresses the appropriate scope of responsibility for consequences of a specific breach (i.e. remoteness of damage), creates an obfuscating amalgam of the factual and normative. Similarly, by drawing a clear distinction between the forward-looking notion of the ‘scope of the duty’ and the backward-looking notion of the scope of responsibility for consequences the text argues that the principle that can coherently be extracted from the SAAMCO case is considerably narrower than the one being presented to courts.
Conference papers on the topic "Unsteady analytical test case":
1
Saiz, Gabriel, Mehmet Imregun, and Abdulnaser I. Sayma. "A Multi Blade-Row Linearised Analysis Method for Flutter and Forced Response Predictions in Turbomachinery." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90789.
Abstract:
A three-dimensional time-linearised unsteady Navier-Stokes solver is presented for the computation of multistage unsteady flow in turbomachinery. The objective is to address multistage aeroelastic effects for both flutter and forced response. Since the method is currently being developed, only forced response applications are studied in this paper. With this approach, travelling waves, known as spinning modes, are propagated across the multistage domain in order to take into account the interaction between the blade-rows. The method is first validated over two simple test cases for which analytical solutions were available. It is then tested on a turbine stage test case and multistage effects are evaluated from the contribution of one spinning mode included in the model. The results are compared with both time-linearised single-row and nonlinear multirow methods. Multi-row effects are shown not to be important in this case. However, the test case serves as a validation for the implementation of the methodology and further work will focus on the implementation of several spinning modes and the computations of forced response and flutter cases with several blade-rows.
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Kielb, Jason, Kurt Weber, and Bruce Crook. "Innovative Design of a Robust Turbine Stage Using Flow Analysis and Subcomponent Rig Testing With Rapid Prototypes." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-28256.
Abstract:
Designing turbine engine components for high cycle fatigue robustness can significantly reduce operating costs and improve safety. However, obtaining an optimum design and getting the new hardware into service using traditional methods is an expensive process. A process that combines state-of-the-art computational fluid dynamics (CFD) analytical simulations with subcomponent rig testing has been developed and demonstrated on a gas turbine engine. The analytical method involves spatial Fourier decomposition of vane exit total pressure from steady flow calculations. This provides an efficient method to reduce the design space and eliminate poor designs, resulting in a small subset of near-optimum designs. To confirm that the remaining candidate designs provide less unsteady forcing and to validate the CFD analysis, a unique experimental test rig was constructed. The experiments consisted of flowing ambient air through a subsection of the engine, while measuring the exit total pressure flow field around the turbine rotor exit annulus with a unique traversing probe. The measured exit total pressure was then Fourier decomposed in space to understand the resulting unsteady forcing on the blade. The costs of the flow rig and producing numerous sets of candidate hardware were much less expensive than full-scale engine or rotating rig tests. New hardware designs tested in the rig were manufactured using a rapid prototyping procedure, which allowed for extremely quick turn around in going from design concept to experimental validation. Good correlation between analysis and test was found, except in a few cases. The majority of these discrepancies were attributed to excitation sources that were impractical to include in the CFD models. This finding indicated that there are still circumstances for which the analytical tools were insufficient and hence experimental validation is still important. Both the analysis and experiments confirmed up to a 50% reduction in the amplitude of unsteady pressure for this particular engine test case.
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Schoenenborn, Harald, Virginie Chenaux, and Peter Ott. "Aeroelasticity at Reversed Flow Conditions: Part 1—Numerical and Experimental Investigations of a Compressor Cascade With Controlled Vibration." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45034.
Abstract:
The prediction of flutter and forced response at normal flow conditions has become a standard procedure during the design of compressor airfoils. But at severe off-design conditions, the flow field becomes very complex, especially during the surge blow-down phase where reversed flow conditions occur. The correct prediction of the unsteady pressures and the resulting aerodynamic excitation or damping at these conditions remains an extremely challenging task. In the first part of the paper, basic investigations for these flow conditions are presented. Aeroelastic calculations during compressor surge are shown in the second part. Experimental investigations were performed in the Annular Test Facility for non-rotating cascades at EPF Lausanne. The test cascade was exposed to flow conditions as expected during the surge blow-down phase which is characterized by large separation regions. Measurements of the steady-state flow conditions on the blade surface, at the outer wall, upstream and downstream of the cascade provided detailed information about the steady flow conditions. The cascade was then subjected to controlled vibration of the blades with constant amplitudes and inter-blade phase angles. Unsteady pressure measurements on the blade surface and at the casing wall provided information about the resulting unsteady flow conditions. Analytical CFD calculations were performed. The steady flow field was calculated using a RANS code. Based on the steady-state flow field, unsteady calculations applying a linearized code were carried out. The agreement between measurements and calculations shows that the steady flow as well as the unsteady flow phenomena can be predicted quantitatively. In addition, knowing the blade vibration mode shape, which in this case is a torsion mode, the aerodynamic damping can be determined for the corresponding flow conditions.
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Hilbert, Gary R., Ron-Ho Ni, and Ronald K. Takahashi. "Forced Response Prediction of Gas Turbine Rotor Blades." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0750.
Abstract:
Abstract An analytical forced response prediction system is used to predict turbomachinery airfoil vibratory stress amplitudes. The forced airfoil vibration can be caused by time dependent (unsteady) aerodynamic loads due to interaction with the flow field from neighboring airfoils rows, such as shocks, wakes, or pressure waves, or due to self induced unsteady aerodynamics such as vortex shedding and unsteady tip vortices. The amplitude of the forced response is of particular interest when the frequency of the time dependent unsteadiness is close to the natural frequency of the forced airfoil. At this condition, the airfoil is at or near resonance and vibratory stress can exceed the material capability causing high cycle fatigue (HCF) failures. The airfoil forced response prediction system presented here combines structural static and dynamic analysis with steady and unsteady computational fluid dynamic analysis in an iterative coupled solution to the aeroelastic problem. The system includes three dimensional viscous multistage steady and unsteady computational fluid dynamics and three dimensional geometric nonlinear structural static, linear free vibration and modal forced response analysis to predict the airfoil amplitude in the resonance modes during engine operation. This analysis system is being used to help identify the cause of HCF failure and determine corrective action. The analysis system is demonstrated using a compressor rotor excited by upstream and downstream vanes. Results are then compared with engine test data.
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Fischer, Felix, and Jörg Seume. "Acoustic Optimization Approach for Annular Diffusers in Turbomachinery Applications Using Plane Wave Modelling." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-80517.
Abstract:
Abstract The experimental investigation of unsteady aerodynamic effects in turbomachinery test rigs requires the establishment of anechoic boundary conditions in order to acquire data unaffected by acoustic reflections outside the test section. In this manner, controlled measurement environments can be achieved that allow for the acquisition of high-quality aeroacoustic and -elastic measurement data in turbomachinery test rigs. In the case of the initial design of the Aeroacoustic Wind Tunnel (AWT) at the Institute of Turbomachinery and Fluid Dynamics, acoustic reflections were observed in the diffuser section of the test rig, which interfered with the sound transmission measurements of low-pressure turbine airfoils. The present paper describes a one-dimensional semi-analytical modelling and optimization approach of sound propagation in the AWTs diffuser section for plane waves based on Webster’s horn equation. With this approach, a new hub diffuser was designed for defined geometric and aerodynamic boundary conditions, which compared to the original geometry, reduce acoustic reflections due to continuous impedance matching. The design of a new supporting strut configuration further reduces reflections due to scattering from installations in the flow path. Validation of the modelling and solution approaches are carried out based on a comparison with experimental data of the initial (reference) design, as well as numerical simulations of both designs. According to analytical and numerical models the optimized design reduces acoustic reflections by up to 21.2 dB compared to the initial design.
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Vilmin, S., E. Lorrain, Ch Hirsch, and M. Swoboda. "Unsteady Flow Modeling Across the Rotor/Stator Interface Using the Nonlinear Harmonic Method." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90210.
Abstract:
The paper presents results of the incorporation of the harmonic nonlinear method into an existing turbomachinery Navier-Stokes code. This approach, introduced by He and Ning in 1998, can be considered as a bridge between classical steady state and full unsteady calculations, providing an approximate unsteady solution at affordable calculation costs. The unsteady flow perturbation is Fourier decomposed in time, and by a casting in the frequency domain transport equations are obtained for each time frequency. The user controls the accuracy of the unsteady solution through the order of the Fourier series. Alongside the solving of the time-averaged flow steady-state equations, each frequency requires the solving of two additional sets of conservation equations (for the real and imaginary parts of each harmonic). The method is made nonlinear by the injection of the so-called deterministic stresses, resulting from all the solved frequencies, into the time-averaged flow solver. Because of the transposition to the frequency domain, only one blade channel is required like a steady flow simulation. The presented method also features a new improved treatment that enhances the flow continuity across the rotor/stator interface by a reconstruction of the harmonics and the time-averaged flow on both sides of the interface. A non-reflective treatment is applied as well at each interface. Validation for analytical and turbomachinery test cases are presented. In particular, results are compared between the harmonic method, steady-state mixing plane and full unsteady calculations. The comparison with the reference full unsteady calculation provides a quantitative indication of the accuracy of the approach, as well as the significant gain in CPU time, whereas the comparison with classical quasi-steady state solutions indicates the gain of accuracy. A multistage compressor flow is also presented to show the capabilities of the method.
7
Cheung, W. S., G. J. M. Sims, R. W. Copplestone, J. R. Tilston, C. W. Wilson, Simon R. Stow, and Ann P. Dowling. "Measurement and Analysis of Flame Transfer Function in a Sector Combustor Under High Pressure Conditions." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38219.
Abstract:
Lean premixed prevaporised (LPP) combustion can reduce NOx emissions from gas turbines, but often leads to combustion instability. A flame transfer function describes the change in the rate of heat release in response to perturbations in the inlet flow as a function of frequency. It is a quantitative assessment of the susceptibility of combustion to disturbances. The resulting fluctuations will in turn generate more acoustic waves and in some situations self-sustained oscillations can result. Flame transfer functions for LPP combustion are poorly understood at present but are crucial for predicting combustion oscillations. This paper describes an experiment designed to measure the flame transfer function of a simple combustor incorporating realistic components. Tests were conducted initially on this combustor at atmospheric pressure (1.2 bar and 550 K) to make an early demonstration of the combustion system. The test rig consisted of a plenum chamber with an inline siren, followed by a single LPP premixer/duct and a combustion chamber with a silencer to prevent natural instabilities. The siren was used to induce variable frequency pressure/acoustic signals into the air approaching the combustor. Both unsteady pressure and heat release measurements were undertaken. There was good coherence between the pressure and heat release signals. At each test frequency, two unsteady pressure measurements in the plenum were used to calculate the acoustic waves in this chamber and hence estimate the mass-flow perturbation at the fuel injection point inside the LPP duct. The flame transfer function relating the heat release perturbation to this mass flow was found as a function of frequency. The same combustor hardware and associated instrumentation were then used for the high pressure (15 bar and 800 K) tests. Flame transfer function measurements were taken at three combustion conditions that simulated the staging point conditions (Idle, Approach and Take-off) of a large turbofan gas turbine. There was good coherence between pressure and heat release signals at Idle, indicating a close relationship between acoustic and heat release processes. Problems were encountered at high frequencies for the Approach and Take-off conditions, but the flame transfer function for the Idle case had very good qualitative agreement with the atmospheric-pressure tests. The flame transfer functions calculated here could be used directly for predicting combustion oscillations in gas turbine using the same LPP duct at the same operating conditions. More importantly they can guide work to produce a general analytical model.
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Hummel, Tobias, Frederik Berger, Nicolai Stadlmair, Bruno Schuermans, and Thomas Sattelmayer. "Extraction of Linear Growth and Damping Rates of High-Frequency Thermoacoustic Oscillations From Time Domain Data." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64233.
Abstract:
This paper presents a set of methodologies for the extraction of linear growth and damping rates associated with transversal eigenmodes at screech level frequencies in thermoacoustically non-compact gas turbine combustion systems from time domain data. Knowledge of these quantities is of high technical relevance as an required input for the design of damping devices for high frequency oscillations. In addition, validation of prediction tools and flame models as well as the thermoacoustic characterization of a given unstable/stable operation point in terms of their distance from the Hopf bifurcation point occurs via the system growth/damping rates. The methodologies solely rely on dynamic measurement data (i.e. unsteady heat release and/or pressure recordings) while avoiding the need of any external excitation (e.g. via sirens), and are thus in principle suitable for the employment on operational engine data. Specifically, the following methodologies are presented: 1) The extraction of pure acoustic damping rates (i.e. without any flame contribution) from oscillatory chemiluminescence and pressure recordings. 2) The obtainment of net growth rates of linearly stable operation points from oscillatory pressure signals. 3) The identification of net growth rates of linearly unstable operation points from noisy pressure envelope data. The fundamental basis of these procedures is the derivation of appropriate stochastic differential equations, which admit analytical solutions that depend on the global system parameters. These analytical expressions serve as objective functions against which measured data are fitted to yield the desired growth or damping rates. Bayesian methods are employed to optimize precision and confidence of the fitting results. Numerical test cases given by time domain formulations of the acoustic conservation equations including high-frequency flame models as well as acoustic damping terms are set up and solved. The resulting unsteady pressure and heat release data are then subjected to the proposed identification methodologies to present corresponding proof of principles and grant suitability for employment on real systems.
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Karri, Satyaprakash, John Charonko, and Pavlos Vlachos. "Robust Gradient Estimation Schemes Using Radial Basis Functions." In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55151.
Abstract:
Utilization of Radial Basis Functions (RBFs) for gradient estimation is tested over various noisy flow fields. A novel mathematical formulation which minimizes the energy functional associated with the analytical surface fit for Gaussian (GA) and Generalized Multiquadratic (GMQ) RBFs is presented. Error analysis of the wall gradient estimation was performed at various resolutions, interpolation grid sizes, and noise levels in synthetically generated Poiseuille and Womersley flow fields for RBFs along with standard finite difference schemes. To test the effectiveness of the methods with DPIV (Digital Particle Image Velocimetry) data, the methods were compared using the velocities obtained by processing images generated from DNS data of an open turbulent channel. Random, bias and total error were computed in all cases. In the absence of noise all tested methods perform well, with error contained under 10% at all resolutions. In the presence of noise the RBFs perform robustly with a total error that can be contained under 10–15% even with 10% noise using various interpolation grid sizes, For turbulent flow data, although the total error is approximately 5% for finite difference schemes in the absence of noise, the error can go as high as 150% in the presence of as little as 1% noise. With DPIV processed data the error is 25–40% for TPS and MQ methods optimization of the fitting parameters that minimize the energy functional associated with the analytical surface using RBFs results in robust gradient estimators are obtained that are applicable to steady, unsteady and turbulent flow fields.
10
Weiss, Felix, and Christoph Kessler. "Drivetrain Influence on the Blade Loads of Hingeless Helicopter Rotors." In Vertical Flight Society 75th Annual Forum & Technology Display. The Vertical Flight Society, 2019. http://dx.doi.org/10.4050/f-0075-2019-14567.
Abstract:
The impact of structural rotor-drivetrain interaction on the blade loads of the Bo105 helicopter is investigated by numerical simulation. For this purpose, the constraint of constant rotor hub speed is dropped and a drivetrain model, consisting of discrete inertia elements and intermediate flexible elements, is connected to the hub. The structural rotor-drivetrain system is coupled to an aerodynamic model consisting of an analytical formulation of unsteady blade element loads combined with a generalized dynamic wake. A time-marching autopilot trim of the rotor-drivetrain system in wind tunnel configuration is performed for a large blade loading flight state as well as a high advance ratio flight state. The comparison of the simulation results with those of a baseline case (constant rotor hub speed) reveals a major drivetrain influence on the blade lead-lag load harmonics at blade passage frequency. Beside the full drivetrain model, reduced models are shown to be capable of predicting the drivetrain influence on blade loads, if they yield the same eigenfrequency of the coupled rotor-drivetrain mode wRDL2 (second collective lead-lag mode couples with drivetrain) as the full model. In a sensitivity analysis, wRDL2 is varied by modification of the stiffness of a reduced drivetrain model. The resulting changes in blade loads are correlated to wRDL2 , which serves as a simple but accurate classification of the drivetrain regarding its influence on vibratory blade loads. Finally, the improvement of lead-lag load prediction by the application of a drivetrain model is demonstrated through comparison of simulated loads with measurements from a wind tunnel test.
Reports on the topic "Unsteady analytical test case":
1
Buchholz. L52308 Temperature Logging as a Cavern Mechanical Integrity Test. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), October 2010. http://dx.doi.org/10.55274/r0010397.
Abstract:
This work documents case histories, develops an analytical solutions to predict a temperature decreases that occurs when gas leaks out of a well, and performs a computational fluid dynamics analyses of a generic gas well.
2
Rimpel, Aaron, Abhay Patil, and Mark Anguiano. PR-316-21201-R01 A Study of the Effects of Liquid Contamination on Seal Performance. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), July 2022. http://dx.doi.org/10.55274/r0012229.
Abstract:
This project is a continuation of research to enhance dry gas seal (DGS) reliability. Previous work reviewed failures from literature and experience of manufacturers and end-users and identified that liquid contamination was the most common cause, but it was concluded there was insufficient quantitative data to base recommendations on for further DGS reliability enhancements. Therefore, experimental and analytical investigations were pursued to fill the void. The ultimate objective was to be able to predict DGS failures due to liquid contamination, which could lead to greater DGS reliability through improvements in design, instrumentation, and monitoring. The current project phase had objectives with simulations and testing. Simulations were extended to the all other pressure conditions for further validation of the modeling assumptions. The improved simulation methodology was subsequently used to predict a condition that suggests a potential failure mode using a one-way fluid-structure interaction simulation. This resulted in a prediction that a liquid mass fraction of 4% would cause a 50% relative reduction of the seal film clearance, which was the chosen test condition to perform the validation. Testing up to three times this target value was agreed upon as the maximum concentration to perform the testing at a maximum duration of 8 minutes. This would be invoked to test more aggressively in case signs of failure were not observed. PRCI and GMRC co-funded this project.
3
Stastny, Petr, Robert Roczniok, Daniel Cleather, Martin Musalek, Dominik Novak, and Michal Vagner. Straight speed and acceleration optimal distances and reference values. A systematic review, and meta-analyses. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, May 2022. http://dx.doi.org/10.37766/inplasy2022.5.0010.
Abstract:
Review question / Objective: To summarize the sprint reference acceleration and speed values for different sprint distances and suggest optimal unification of ice-hockey straight sprint testing. Eligibility criteria: The title and abstract screening was done by two researchers (PS and RR) who selected a set of articles for full text screening, where the inclusion criteria were: 1) male or female ice-hockey players; 2) any cross-sectional or intervention study; 3) tests of ice-hockey sprinting over any distance or any battery of conditioning tests that included straight-line sprints; and, 4) results reported straight-line sprint distance, speed, time, or acceleration. In the case of disagreement between the evaluating authors, the final decision was made by a third author (MV).The full text screening exclusion criteria were: 1) if the article was not in English; 2) the testing did not include straight-line sprinting; 3) the reported values did not include data distribution; 4) the study reported only maximum speed without skating time or average speed; 5) the end of the sprint was defined by the point the player stopped sprinting; 6) the measurement was made with a stopwatch; and, 7) the study had high bias estimation. The maximum speed test was not included due to the uncertain velocity conditions at beginning of testing distance. The bias estimation was performed using the JBI (Joanna Briggs Institute) Critical Appraisal Checklist for Analytical Cross Sectional Studies (supplementary material 1).
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Rimpel, Aaron. PR-316-17200-R03 A Study of the Effects of Liquid Contamination on Seal Performance. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), January 2021. http://dx.doi.org/10.55274/r0012015.
Abstract:
This project is a continuation of research to enhance dry gas seal (DGS) reliability. Previous work reviewed failures from literature and experience of manufacturers and end-users and identified that liquid contamination was the most common cause, but it was concluded there was insufficient quantitative data to base recommendations on for further DGS reliability enhancements. Therefore, experimental and analytical investigations were pursued to fill the void. The ultimate objective was to be able to predict DGS failures due to liquid contamination, which could lead to greater DGS reliability through improvements in design, instrumentation, and monitoring. From the previous project phase, testing had demonstrated that the introduction of small quantities of oil (liquid mass fraction up to 3%) produced a slight increase in torque but impacts on temperatures and leakage were negligible. Previous simulations demonstrated converged two-phase computational fluid dynamics (CFD) with conjugate heat transfer (CHT) solutions of the seal and reasonable trends, but the agreement with test data was lower than desired. The current project phase made significant improvements to the single- and two-phase CFD simulation of the DGS, lowering the discrepancy of all previously reported performance parameters. The current simulations were performed only at the 700 psi supply pressure case. Ideal gas was used, and CHT coupling was used to predict temperatures of the primary ring. The previous wall thermal boundary conditions were not well understood, so the current work focused on establishing performance with adiabatic walls.
5
Bray, Jonathan, Ross Boulanger, Misko Cubrinovski, Kohji Tokimatsu, Steven Kramer, Thomas O'Rourke, Ellen Rathje, Russell Green, Peter Robertson, and Christine Beyzaei. U.S.—New Zealand— Japan International Workshop, Liquefaction-Induced Ground Movement Effects, University of California, Berkeley, California, 2-4 November 2016. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, March 2017. http://dx.doi.org/10.55461/gzzx9906.
Abstract:
There is much to learn from the recent New Zealand and Japan earthquakes. These earthquakes produced differing levels of liquefaction-induced ground movements that damaged buildings, bridges, and buried utilities. Along with the often spectacular observations of infrastructure damage, there were many cases where well-built facilities located in areas of liquefaction-induced ground failure were not damaged. Researchers are working on characterizing and learning from these observations of both poor and good performance. The “Liquefaction-Induced Ground Movements Effects” workshop provided an opportunity to take advantage of recent research investments following these earthquake events to develop a path forward for an integrated understanding of how infrastructure performs with various levels of liquefaction. Fifty-five researchers in the field, two-thirds from the U.S. and one-third from New Zealand and Japan, convened in Berkeley, California, in November 2016. The objective of the workshop was to identify research thrusts offering the greatest potential for advancing our capabilities for understanding, evaluating, and mitigating the effects of liquefaction-induced ground movements on structures and lifelines. The workshop also advanced the development of younger researchers by identifying promising research opportunities and approaches, and promoting future collaborations among participants. During the workshop, participants identified five cross-cutting research priorities that need to be addressed to advance our scientific understanding of and engineering procedures for soil liquefaction effects during earthquakes. Accordingly, this report was organized to address five research themes: (1) case history data; (2) integrated site characterization; (3) numerical analysis; (4) challenging soils; and (5) effects and mitigation of liquefaction in the built environment and communities. These research themes provide an integrated approach toward transformative advances in addressing liquefaction hazards worldwide. The archival documentation of liquefaction case history datasets in electronic data repositories for use by the broader research community is critical to accelerating advances in liquefaction research. Many of the available liquefaction case history datasets are not fully documented, published, or shared. Developing and sharing well-documented liquefaction datasets reflect significant research efforts. Therefore, datasets should be published with a permanent DOI, with appropriate citation language for proper acknowledgment in publications that use the data. Integrated site characterization procedures that incorporate qualitative geologic information about the soil deposits at a site and the quantitative information from in situ and laboratory engineering tests of these soils are essential for quantifying and minimizing the uncertainties associated site characterization. Such information is vitally important to help identify potential failure modes and guide in situ testing. At the site scale, one potential way to do this is to use proxies for depositional environments. At the fabric and microstructure scale, the use of multiple in situ tests that induce different levels of strain should be used to characterize soil properties. The development of new in situ testing tools and methods that are more sensitive to soil fabric and microstructure should be continued. The development of robust, validated analytical procedures for evaluating the effects of liquefaction on civil infrastructure persists as a critical research topic. Robust validated analytical procedures would translate into more reliable evaluations of critical civil infrastructure iv performance, support the development of mechanics-based, practice-oriented engineering models, help eliminate suspected biases in our current engineering practices, and facilitate greater integration with structural, hydraulic, and wind engineering analysis capabilities for addressing multi-hazard problems. Effective collaboration across countries and disciplines is essential for developing analytical procedures that are robust across the full spectrum of geologic, infrastructure, and natural hazard loading conditions encountered in practice There are soils that are challenging to characterize, to model, and to evaluate, because their responses differ significantly from those of clean sands: they cannot be sampled and tested effectively using existing procedures, their properties cannot be estimated confidently using existing in situ testing methods, or constitutive models to describe their responses have not yet been developed or validated. Challenging soils include but are not limited to: interbedded soil deposits, intermediate (silty) soils, mine tailings, gravelly soils, crushable soils, aged soils, and cemented soils. New field and laboratory test procedures are required to characterize the responses of these materials to earthquake loadings, physical experiments are required to explore mechanisms, and new soil constitutive models tailored to describe the behavior of such soils are required. Well-documented case histories involving challenging soils where both the poor and good performance of engineered systems are documented are also of high priority. Characterizing and mitigating the effects of liquefaction on the built environment requires understanding its components and interactions as a system, including residential housing, commercial and industrial buildings, public buildings and facilities, and spatially distributed infrastructure, such as electric power, gas and liquid fuel, telecommunication, transportation, water supply, wastewater conveyance/treatment, and flood protection systems. Research to improve the characterization and mitigation of liquefaction effects on the built environment is essential for achieving resiliency. For example, the complex mechanisms of ground deformation caused by liquefaction and building response need to be clarified and the potential bias and dispersion in practice-oriented procedures for quantifying building response to liquefaction need to be quantified. Component-focused and system-performance research on lifeline response to liquefaction is required. Research on component behavior can be advanced by numerical simulations in combination with centrifuge and large-scale soil–structure interaction testing. System response requires advanced network analysis that accounts for the propagation of uncertainty in assessing the effects of liquefaction on large, geographically distributed systems. Lastly, research on liquefaction mitigation strategies, including aspects of ground improvement, structural modification, system health monitoring, and rapid recovery planning, is needed to identify the most effective, cost-efficient, and sustainable measures to improve the response and resiliency of the built environment.