Journal articles: 'Unsteady'

1

Kailasanath, K. "Unsteady Combustion." AIAA Journal 35, no. 5 (May 1997): 920. http://dx.doi.org/10.2514/2.7470.

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Nandhagopal, R. "Unsteady gait." Postgraduate Medical Journal 82, no. 967 (May 1, 2006): e7-e7. http://dx.doi.org/10.1136/pgmj.2005.040774.

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3

Marsh, Laura. "Unsteady Work." Dissent 67, no. 3 (2020): 149–52. http://dx.doi.org/10.1353/dss.2020.0043.

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4

Baider, Lea. "Unsteady Balance." Journal of Pediatric Hematology/Oncology 33 (October 2011): S108—S111. http://dx.doi.org/10.1097/mph.0b013e318230ddb2.

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5

Foucault, Eric, and Philippe Szeger. "Unsteady flowmeter." Flow Measurement and Instrumentation 69 (October 2019): 101607. http://dx.doi.org/10.1016/j.flowmeasinst.2019.101607.

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6

Derrig, Anne. "Unsteady Detective." American Book Review 33, no. 1 (2011): 14. http://dx.doi.org/10.1353/abr.2011.0174.

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7

Zhang, Hongxin, Shaowen Chen, Yun Gong, and Songtao Wang. "A comparison of different unsteady flow control techniques in a highly loaded compressor cascade." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 6 (April 18, 2018): 2051–65. http://dx.doi.org/10.1177/0954410018770492.

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A numerical research is applied to investigate the effect of controlling the flow separation in a certain highly loaded compressor cascade using different unsteady flow control techniques. Firstly, unsteady pulsed suction as a new novel unsteady flow control technique was proposed and compared to steady constant suction in the control of flow separation. A more exciting effect of controlling the flow separation and enhancing the aerodynamic performance for unsteady pulsed suction was obtained compared to steady constant suction with the same time-averaged suction flow rate. Simultaneously, with the view to further exploring the potential of unsteady flow control technique, unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet (three unsteady flow control techniques) are analyzed comparatively in detail by the related unsteady aerodynamic parameters such as excitation location, frequency, and amplitude. The results show that unsteady pulsed suction shows greater advantage than unsteady pulsed blowing and unsteady synthetic jet in controlling the flow separation. Unsteady pulsed suction and unsteady synthetic jet have a wider range of excitation location obtaining positive effects than unsteady pulsed blowing. The ranges of excitation frequency and excitation amplitude for unsteady pulsed suction gaining favorable effects are both much wider than that of unsteady pulsed blowing and unsteady synthetic jet. The optimum frequencies of unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet are found to be different, but these optimum frequencies are all an integer multiple of the natural frequency of vortex shedding. The total pressure loss coefficient is reduced by 16.98%, 16.55%, and 17.38%, respectively, when excitation location, frequency, and amplitude are all their own optimal values for unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet. The optimum result of unsteady synthetic jet only slightly outperforms that of unsteady pulsed suction and unsteady pulsed blowing. But unfortunately, there is no advantage from the standpoint of overall efficiency for the optimum result of unsteady synthetic jet because the slight improvement has to require a greater power consumption than the unsteady pulsed suction and unsteady pulsed blowing methods.

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8

Botta, Nicola, and Rolf Jeltsch. "A numerical method for unsteady flows." Applications of Mathematics 40, no. 3 (1995): 175–201. http://dx.doi.org/10.21136/am.1995.134290.

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9

Fan, S., and B. Lakshminarayana. "Computation and Simulation of Wake-Generated Unsteady Pressure and Boundary Layers in Cascades: Part 1—Description of the Approach and Validation." Journal of Turbomachinery 118, no. 1 (January 1, 1996): 96–108. http://dx.doi.org/10.1115/1.2836612.

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The unsteady pressure and boundary layers on a turbomachinery blade row arising from periodic wakes due to upstream blade rows are investigated in this paper. A time-accurate Euler solver has been developed using an explicit four-stage Runge–Kutta scheme. Two-dimensional unsteady nonreflecting boundary conditions are used at the inlet and the outlet of the computational domain. The unsteady Euler solver captures the wake propagation and the resulting unsteady pressure field, which is then used as the input for a two-dimensional unsteady boundary layer procedure to predict the unsteady response of blade boundary layers. The boundary layer code includes an advanced k–ε model developed for unsteady turbulent boundary layers. The present computational procedure has been validated against analytic solutions and experimental measurements. The validation cases include unsteady inviscid flows in a flat-plate cascade and a compressor exit guide vane (EGV) cascade, unsteady turbulent boundary layer on a flat plate subject to a traveling wave, unsteady transitional boundary layer due to wake passing, and unsteady flow at the midspan section of an axial compressor stator. The present numerical procedure is both efficient and accurate in predicting the unsteady flow physics resulting from wake/blade-row interaction, including wake-induced unsteady transition of blade boundary layers.

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10

Boiko, Andrey V., and Andrey V. Ivanov. "Goertler's unsteady instability." Siberian Journal of Physics 2, no. 3 (2007): 8–15. http://dx.doi.org/10.54238/1818-7994-2007-2-3-8-15.

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11

Simons, Stephen M., and Phillip Hartwell. "UNSTEADY GAIT - RUNNER." Medicine & Science in Sports & Exercise 27, Supplement (May 1995): S99. http://dx.doi.org/10.1249/00005768-199505001-00561.

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12

Stetson, Kenneth F. "Unsteady transition location." AIAA Journal 27, no. 8 (August 1989): 1135–37. http://dx.doi.org/10.2514/3.10235.

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13

Dudley, R. "BIOMECHANICS:Enhanced: Unsteady Aerodynamics." Science 284, no. 5422 (June 18, 1999): 1937–39. http://dx.doi.org/10.1126/science.284.5422.1937.

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14

Biernat, Helfried K., Martin F. Heyn, and Valdimir S. Semenov. "Unsteady Petschek reconnection." Journal of Geophysical Research 92, A4 (1987): 3392. http://dx.doi.org/10.1029/ja092ia04p03392.

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15

Ainsworth, R. W., R. J. Miller, R. W. Moss, and S. J. Thorpe. "Unsteady pressure measurement." Measurement Science and Technology 11, no. 7 (June 16, 2000): 1055–76. http://dx.doi.org/10.1088/0957-0233/11/7/319.

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16

Geiger, Jack. "The Unsteady March." Perspectives in Biology and Medicine 48, no. 1 (2005): 1–9. http://dx.doi.org/10.1353/pbm.2005.0009.

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17

Coleman, Nailah. "Unsteady Gait - Walking." Medicine & Science in Sports & Exercise 47 (May 2015): 20. http://dx.doi.org/10.1249/01.mss.0000476447.71387.a8.

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18

Fingersh, Lee Jay. "Unsteady Aerodynamics Experiment." Journal of Solar Energy Engineering 123, no. 4 (January 1, 2001): 267. http://dx.doi.org/10.1115/1.1374208.

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19

Abrashkin, Anatoly. "Unsteady Gerstner waves." Chaos, Solitons & Fractals 118 (January 2019): 152–58. http://dx.doi.org/10.1016/j.chaos.2018.11.007.

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20

Qin, W., and H. Tsukamoto. "Theoretical Study of Pressure Fluctuations Downstream of a Diffuser Pump Impeller—Part 1: Fundamental Analysis on Rotor-Stator Interaction." Journal of Fluids Engineering 119, no. 3 (September 1, 1997): 647–52. http://dx.doi.org/10.1115/1.2819293.

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A theoretical method was developed to calculate the unsteady flow caused by the interaction between impeller and diffuser vanes in a diffuser pump by using the singularity method. The unsteady flow in the diffuser vane is assumed to be induced by three kinds of unsteady vortices: bound vortices distributed on the impeller blades and diffuser vanes, and free vortices shed from the trailing edge of diffuser vanes. In order to make clear the contribution of each harmonic component of unsteady vortices to unsteady pressure, all the unsteady vortices are expressed in the form of Fourier series. The calculated unsteady pressures downstream of impeller agree well with the corresponding measured ones. Moreover, it was shown that impulsive pressure plays a predominant role for unsteady pressures.

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21

Schobeiri, M. T., and L. Wright. "Advances in Unsteady Boundary Layer Transition Research, Part I: Theory and Modeling." International Journal of Rotating Machinery 9, no. 1 (2003): 1–9. http://dx.doi.org/10.1155/s1023621x03000010.

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This two-part article presents recent advances in boundary layer research that deal with the unsteady boundary layer transition modeling and its validation. A new unsteady boundary layer transition model was developed based on a universal unsteady intermittency function. It accounts for the effects of periodic unsteady wake flow on the boundary layer transition. To establish the transition model, an inductive approach was implemented; the approach was based on the results of comprehensive experimental and theoretical studies of unsteady wake flow and unsteady boundary layer flow. The experiments were performed on a curved plate at a zero streamwise pressure gradient under a periodic unsteady wake flow, where the frequency of the periodic unsteady flow was varied. To validate the model, systematic experimental investigations were performed on the suction and pressure surfaces of turbine blades integrated into a high-subsonic cascade test facility, which was designed for unsteady boundary layer investigations. The analysis of the experiment's results and comparison with the model's prediction confirm the validity of the model and its ability to predict accurately the unsteady boundary layer transition.

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22

Cai, Mengqi, Linshu Zhou, Hang Lei, and Hanjie Huang. "Wind Tunnel Test Investigation on Unsteady Aerodynamic Coefficients of Iced 4-Bundle Conductors." Advances in Civil Engineering 2019 (June 13, 2019): 1–12. http://dx.doi.org/10.1155/2019/2586242.

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Iced conductor motion is induced by the aerodynamic instability of these conductors. The unsteady aerodynamic characteristics are different from the steady aerodynamic characteristics. The unsteady aerodynamic coefficients of typical iced conductors’ models under torsional motion are measured by the unsteady wind tunnel test. The unsteady aerodynamic coefficients of crescent-shape and sector-shape iced 4-bundle conductors under different torsional motion frequencies, wind velocities, and ice thicknesses are obtained. Wind test results show that there are significant differences between the unsteady and steady aerodynamic coefficients. The unsteady aerodynamic coefficients curve is a loop which is different from the steady aerodynamic coefficients. In addition, the obvious differences exist between unsteady aerodynamic coefficients of crescent-shape and sector-shape iced bundle conductors. Critical parameters, including torsional motion frequencies, wind velocity, ice shape, and ice thickness, have significant influences on unsteady aerodynamic coefficients. It shows that the wind tunnel experiment results are able to provide necessary data for the investigation of iced bundle conductor motion and their prevention techniques.

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23

AZUMA, Seiji, Akira FUJII, Yoshiki YOSHIDA, and Yoshinobu TSUJIMOTO. "Unsteady Blade Stress due to Unsteady Cavitations in 3-Bladed Inducer." Proceedings of the Fluids engineering conference 2000 (2000): 225. http://dx.doi.org/10.1299/jsmefed.2000.225.

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24

YADAV, SANJAY K., ATUL KUMAR, DILIP K. JAISWAL, and NAVEEN KUMAR. "One-dimensional unsteady solute transport along unsteady flow through inhomogeneous medium." Journal of Earth System Science 120, no. 2 (April 2011): 205–13. http://dx.doi.org/10.1007/s12040-011-0048-7.

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25

Mossman, Deborah J., and Nael Al Mulki. "One-dimensional unsteady flow and unsteady pesticide transport in a reservoir." Ecological Modelling 89, no. 1-3 (August 1996): 259–67. http://dx.doi.org/10.1016/0304-3800(95)00146-8.

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26

Hunt, D. L., M. Childs, and M. Maina. "QUACC, a novel method for predicting unsteady flows — including propellers and store release." Aeronautical Journal 105, no. 1050 (August 2001): 427–34. http://dx.doi.org/10.1017/s0001924000012409.

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AbstractAerospace designers are increasingly interested in predicting unsteady flowfields such as those associated with store release, rotating propellers etc. However, the cost of performing fully unsteady calculations is usually prohibitively expensive. In order to address this problem for unsteady flows driven by a moving surface, a novel method is presented which calculates the time derivates as an analytic function of the instantaneous flowfield. This allows an accurate solution of the unsteady flow equations to be calculated using a quasi-unsteady approach. The validity of this approach is demonstrated for a store release and a propeller test case. Possible extensions to this method for more complex unsteady flows are presented.

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27

Dowell, Earl H., Kenneth C. Hall, and Michael C. Romanowski. "Eigenmode Analysis in Unsteady Aerodynamics: Reduced Order Models." Applied Mechanics Reviews 50, no. 6 (June 1, 1997): 371–86. http://dx.doi.org/10.1115/1.3101718.

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In this article, we review the status of reduced order modeling of unsteady aerodynamic systems. Reduced order modeling is a conceptually novel and computationally efficient technique for computing unsteady flow about isolated airfoils, wings, and turbomachinery cascades. Starting with either a time domain or frequency domain computational fluid dynamics (CFD) analysis of unsteady aerodynamic or aeroacoustic flows, a large, sparse eigenvalue problem is solved using the Lanczos algorithm. Then, using just a few of the resulting eigenmodes, a Reduced Order Model of the unsteady flow is constructed. With this model, one can rapidly and accurately predict the unsteady aerodynamic response of the system over a wide range of reduced frequencies. Moreover, the eigenmode information provides important insights into the physics of unsteady flows. Finally, the method is particularly well suited for use in the active control of aeroelastic and aeroacoustic phenomena as well as in standard aeroelastic analysis for flutter or gust response. Numerical results presented include: 1) comparison of the reduced order model to classical unsteady incompressible aerodynamic theory, 2) reduced order calculations of compressible unsteady aerodynamics based on the full potential equation, 3) reduced order calculations of unsteady flow about an isolated airfoil based on the Euler equations, and 4) reduced order calculations of unsteady viscous flows associated with cascade stall flutter, 5) flutter analysis using the Reduced Order Model. This review article includes 25 references.

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28

Lu, Weiyu, Guoping Huang, Jinchun Wang, and Yuxuan Yang. "Interpretation of Four Unique Phenomena and the Mechanism in Unsteady Flow Separation Controls." Energies 12, no. 4 (February 13, 2019): 587. http://dx.doi.org/10.3390/en12040587.

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Unsteady flow separation controls are effective in suppressing flow separations. However, the unique phenomena in unsteady separation control, including frequency-dependent, threshold, location-dependent, and lock-on effects, are not fully understood. Furthermore, the mechanism of the effectiveness that lies in unsteady flow controls remains unclear. Thus, this study aims to interpret further the unique phenomena and mechanism in unsteady flow separation controls. First, numerical simulation and some experimental results of a separated curved diffuser using pulsed jet flow control are discussed to show the four unique phenomena. Second, the bases of unsteady flow control, flow instability, and free shear flow theories are introduced to elucidate the unique phenomena and mechanism in unsteady flow separation controls. Subsequently, with the support of these theories, the unique phenomena of unsteady flow control are interpreted, and the mechanisms hidden in the phenomena are revealed.

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29

Schobeiri, M. T., and L. Wright. "Advances in Unsteady Boundary Layer Transition Research, Part II: Experimental Verification." International Journal of Rotating Machinery 9, no. 1 (2003): 11–22. http://dx.doi.org/10.1155/s1023621x03000022.

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This two-part article presents recent advances in boundary layer research into the unsteady boundary layer transition modeling and its validation. This, Part II, deals with the results of an inductive approach based on comprehensive experimental and theoretical studies of unsteady wake flow and unsteady boundary layer flow. The experiments were performed on a curved plate at a zero streamwise pressure gradient under periodic unsteady wake flow, in which the frequency of the periodic unsteady flow was varied. To validate the model, systematic experimental investigations were performed on the suction and pressure surfaces of turbine blades integrated into a high-subsonic cascade test facility, which was designed for unsteady boundary layer investigations. The analysis of the experiment's results and comparison with the model's prediction confirm the validity of the model and its ability to predict accurately the unsteady boundary layer transition.

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30

Ayer, T. C., and J. M. Verdon. "Validation of a Nonlinear Unsteady Aerodynamic Simulator for Vibrating Blade Rows." Journal of Turbomachinery 120, no. 1 (January 1, 1998): 112–21. http://dx.doi.org/10.1115/1.2841372.

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A time-accurate Euler/Navier–Stokes analysis is applied to predict unsteady subsonic and transonic flows through a vibrating cascade. The intent is to validate this nonlinear analysis along with an existing linearized inviscid analysis via result comparisons for unsteady flows that are representative of those associated with blade flutter. The time-accurate analysis has also been applied to determine the relative importance of nonlinear and viscous effects on blade response. The subsonic results reveal a close agreement between inviscid and viscous unsteady blade loadings. Also, the unsteady surface pressure responses are essentially linear, and predicted quite accurately using a linearized inviscid analysis. For unsteady transonic flows, shocks and their motions cause significant nonlinear contributions to the local unsteady response. Viscous displacement effects tend to diminish shock strength and impulsive unsteady shock loads. For both subsonic and transonic flows, the energy transfer between the fluid and the structure is essentially captured by the first-harmonic component of the nonlinear unsteady solutions, but in transonic flows, the nonlinear first-harmonic and the linearized inviscid responses differ significantly in the vicinity of shocks.

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31

Tran, L. T., and D. B. Taulbee. "Prediction of Unsteady Rotor-Surface Pressure and Heat Transfer From Wake Passings." Journal of Turbomachinery 114, no. 4 (October 1, 1992): 807–17. http://dx.doi.org/10.1115/1.2928034.

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The research described in this paper is a numerical investigation of the effects of unsteady flow on gas turbine heat transfer, particularly on a rotor blade surface. The unsteady flow in a rotor blade passage and the unsteady heat transfer on the blade surface as a result of wake/blade interaction are modeled by the inviscid flow/boundary layer approach. The Euler equations that govern the inviscid flow are solved using a time-accurate marching scheme. The unsteady flow in the blade passage is induced by periodically moving a wake model across the passage inlet. Unsteady flow solutions in the passage provide pressure gradients and boundary conditions for the boundary-layer equations that govern the viscous flow adjacent to the blade surface. Numerical solutions of the unsteady turbulent boundary layer yield surface heat flux values that can then be compared to experimental data. Comparisons with experimental data show that unsteady heat flux on the blade suction surface is well predicted, but the predictions of unsteady heat flux on the blade pressure surface do not agree.

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32

Sun, Yan, Guohua Xu, and Yongjie Shi. "Numerical Investigation of an Unsteady Blade Surface Blowing Method to Reduce Rotor Blade-Vortex Interaction Noise." International Journal of Aerospace Engineering 2022 (August 27, 2022): 1–19. http://dx.doi.org/10.1155/2022/9647206.

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This paper presents a numerical investigation of unsteady surface blowing using periodic variations of jet velocity with azimuthal angle to reduce helicopter rotor blade-vortex interaction (BVI) noise. The unsteady blowing is modeled as the mass flow outlet boundary condition of time-varying jet velocity on the blade surface grid using computational fluid dynamics. The same high-resolution overset grid system and flow/noise solver are used to perform a detailed flow field simulation and noise prediction for the nonblowing baseline case and the steady/unsteady blowing cases under the rotor BVI condition, and a grid convergence study for the steady and unsteady blowing cases is carried out. The BVI noise reduction and rotor thrust coefficient results of the unsteady blowing method and the previously published steady blowing with constant jet velocity are then compared. The noise reduction level of unsteady blowing is approximately equivalent to that of steady blowing (noise reduction is more than 3 dB). However, the loss in rotor thrust coefficient caused by unsteady blowing (3.3%) is only half of that by steady blowing (6.3%); the air mass cost by unsteady blowing is only 63.7% of that by steady blowing per rotation revolution. The results show that unsteady blowing can effectively reduce BVI noise with lower cost and less thrust loss.

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33

Fan, S., and B. Lakshminarayana. "Time-Accurate Euler Simulation of Interaction of Nozzle Wake and Secondary Flow With Rotor Blade in an Axial Turbine Stage Using Nonreflecting Boundary Conditions." Journal of Turbomachinery 118, no. 4 (October 1, 1996): 663–78. http://dx.doi.org/10.1115/1.2840922.

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The objective of this paper is to investigate the three-dimensional unsteady flow interactions in a turbomachine stage. A three-dimensional time-accurate Euler code has been developed using an explicit four-stage Runge–Kutta scheme. Three-dimensional unsteady nonreflecting boundary conditions are formulated at the inlet and the outlet of the computational domain to remove the spurious numerical reflections. The three-dimensional code is first validated for two-dimensional and three-dimensional cascades with harmonic vortical inlet distortions. The effectiveness of the nonreflecting boundary conditions is demonstrated. The unsteady Euler solver is then used to simulate the propagation of nozzle wake and secondary flow through the rotor and the resulting unsteady pressure field in an axial turbine stage. The three-dimensional and time-dependent propagation of nozzle wakes in the rotor blade row and the effects of nozzle secondary flow on the rotor unsteady surface pressure and passage flow field are studied. It was found that the unsteady flow field in the rotor is highly three dimensional and the nozzle secondary flow has significant contribution to the unsteady pressure on the blade surfaces. Even though the steady flow at the midspan is nearly two dimensional, the unsteady flow is three dimensional and the unsteady pressure distribution cannot be predicted by a two-dimensional analysis.

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34

Prytula, N., Ya Pyanylo, and M. Prytula. "Optimization of unsteady operating modes of gas mains." Mathematical Modeling and Computing 3, no. 2 (December 31, 2016): 183–90. http://dx.doi.org/10.23939/mmc2016.02.183.

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35

Chen, Ming Zhou, and Qi Dou Zhou. "Numerical Simulation of Fluctuating Propeller Forces and Comparison with Experimental Data." Applied Mechanics and Materials 105-107 (September 2011): 518–22. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.518.

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Unsteady CFD method based on realizable k-ε model is used for predicting unsteady forces of propeller working in non-uniform wake. First, CFD computations with different mesh scales were conducted at the propeller design condition, the results show that mesh refinement changed the results little. Then unsteady CFD simulation with different time step intervals was conducted for determining suitable time step interval, the results show that it is suitable for propeller rotating 3° per step. Based on the chosen mesh and time step interval, unsteady CFD simulation of propeller P4118 was conducted in 3-cycle and 4-cycle inflow, the unsteady thrust, torque and horizontal force agree well with experimental data, the results show that CFD method has good accuracy in predicting unsteady propeller forces.

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36

Schulz, H. D., H. E. Gallus, and B. Lakshminarayana. "Three-Dimensional Separated Flow Field in the Endwall Region of an Annular Compressor Cascade in the Presence of Rotor-Stator Interaction: Part 2—Unsteady Flow and Pressure Field." Journal of Turbomachinery 112, no. 4 (October 1, 1990): 679–88. http://dx.doi.org/10.1115/1.2927708.

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An experimental study of the unsteady three-dimensional flow and pressure field in an annular compressor cascade with an upstream rotor has been carried out at several incidences to the stator blade. The distributions of the unsteady pressures at the blade surfaces are measured using fast response Kulite sensors. The unsteady blade boundary layers and the passage flow are measured with a hot-wire sensor. A detailed interpretation of the magnitude of unsteady pressures, phase angle differences, unsteady blade boundary layers, and wake transport through the stator passage is presented and analyzed in the paper. The unsteady pressures are found to be dominant near the blade leading edge. Substantially higher pressure fluctuations occur in this region as well as on the edge of the corner flow separation region.

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37

Healy, Carol. "Help for unsteady hands." Postgraduate Medicine 112, no. 3 (September 2002): 8. http://dx.doi.org/10.3810/pgm.2002.09.1311.

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38

Ulstein, Tore, and Odd M. Faltinsen. "Two-Dimensional Unsteady Planing." Journal of Ship Research 40, no. 03 (September 1, 1996): 200–210. http://dx.doi.org/10.5957/jsr.1996.40.3.200.

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An analytical and numerical study of two-dimensional unsteady planing of a flat plate is presented. The immersion of the plate is assumed small; hence, the spray at the leading edge is represented by a square root singularity. The analogy to airfoil theory is used and the hydrodynamic problem is solved in the time domain. The time-varying wetted-length change due to the water flow is accounted for by a generalized Wagner approach. The present theory is verified by comparison with an analytical solution by Sedov (1940) for water entry of a planing plate and with the linear frequency domain solution by Bessho & Komatsu (1984) for a heaving planing plate.

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39

Pfeiffer, Friedrich. "Unsteady processes in machines." Chaos: An Interdisciplinary Journal of Nonlinear Science 4, no. 4 (December 1994): 693–705. http://dx.doi.org/10.1063/1.166048.

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40

Haller, Merrick C., and H. Tuba Özkan-Haller. "Waves on unsteady currents." Physics of Fluids 19, no. 12 (December 2007): 126601. http://dx.doi.org/10.1063/1.2803349.

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41

Philip, J. R. "Linearized unsteady multidimensional infiltration." Water Resources Research 22, no. 12 (November 1986): 1717–27. http://dx.doi.org/10.1029/wr022i012p01717.

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42

Babic, Marijan. "Unsteady Couette granular flows." Physics of Fluids 9, no. 9 (September 1997): 2486–505. http://dx.doi.org/10.1063/1.869367.

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43

Lyn, Dennis A. "Unsteady Sediment‐Transport Modeling." Journal of Hydraulic Engineering 113, no. 1 (January 1987): 1–15. http://dx.doi.org/10.1061/(asce)0733-9429(1987)113:1(1).

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44

Kwong, A. H. M., and A. P. Dowling. "Unsteady Flow in Diffusers." Journal of Fluids Engineering 116, no. 4 (December 1, 1994): 842–47. http://dx.doi.org/10.1115/1.2911859.

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The flow in a diffuser is unsteady in the range of optimum pressure recovery; diffusers can therefore be a major source of noise in pipework systems. A theory is developed to predict the frequency of this noise and good agreement with experimental results, for both conical and rectangular diffusers, is demonstrated. The acoustics of the duct to which a diffuser is connected are found to have a crucial effect on the unsteady flow within the diffuser, a point which has been overlooked previously in the literature. Once this is recognized, it is possible to reconcile experimental results for air and water diffusers.

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45

Qiao, M., and D. L. Jindrich. "Compensations during Unsteady Locomotion." Integrative and Comparative Biology 54, no. 6 (June 19, 2014): 1109–21. http://dx.doi.org/10.1093/icb/icu058.

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46

LOTT, FRANCOIS, and HECTOR TEITELBAUM. "Linear unsteady mountain waves." Tellus A 45, no. 3 (May 1993): 201–20. http://dx.doi.org/10.1034/j.1600-0870.1993.t01-2-00004.x.

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47

Hogg, Andrew J., Edward J. Goldsmith, and Mark J. Woodhouse. "Unsteady turbulent line plumes." Journal of Fluid Mechanics 856 (September 28, 2018): 103–34. http://dx.doi.org/10.1017/jfm.2018.698.

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The unsteady ascent of a buoyant, turbulent line plume through a quiescent, uniform environment is modelled in terms of the width-averaged vertical velocity and density deficit. It is demonstrated that for a well-posed, linearly stable model, account must be made for the horizontal variation of the velocity and the density deficit; in particular the variance of the velocity field and the covariance of the density deficit and velocity fields, represented through shape factors, must exceed threshold values, and that models based upon ‘top-hat’ distributions in which the dependent fields are piecewise constant are ill-posed. Numerical solutions of the nonlinear governing equations are computed to reveal that the transient response of the system to an instantaneous change in buoyancy flux at the source may be captured through new similarity solutions, the form of which depend upon both the ratio of the old to new buoyancy fluxes and the shape factors.

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48

Chin, G. J. "PSYCHOLOGY: An Unsteady State." Science 309, no. 5740 (September 2, 2005): 1459b. http://dx.doi.org/10.1126/science.309.5740.1459b.

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49

Desrayaud, Gilles, and Guy Lauriat. "Unsteady confined buoyant plumes." Journal of Fluid Mechanics 252 (July 1993): 617–46. http://dx.doi.org/10.1017/s002211209300391x.

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Two-dimensional time-dependent buoyancy-induced flows above a horizontal line heat source inside rectangular vessels, with adiabatic sidewalls and top and bottom walls maintained at uniform temperature, are studied numerically. Transitions to unsteady flows are performed by direct simulations for various depths of immersion of the source in the central vertical plane of air-filled vessels. For a square vessel and a line source near the bottom wall, the numerical solutions exhibit a sequence of instabilities, called natural swaying motion of confined plumes, beginning with a periodic regime having a high fundamental frequency followed by a two-frequency locked regime. Then, broadband components appearing in the spectra indicate chaotic behaviour and a weakly turbulent motion arises via an intermittent route to chaos. For rectangular vessels of aspect ratio greater than 2 and depths of immersion greater than the width, the flow undergoes a pitchfork bifurcation. This symmetry breaking is driven by the destabilization of an upper unstable layer of stagnant fluid above the plume. Then a subcritical Hopf bifurcation occurs. On the other hand, if the depth of immersion is lower than the width of the vessel, a stable layer of fluid is at rest below the line source. Then penetrative convection sets the whole air-filled vessel in motion and an oscillatory motion of very low frequency arises through supercritical Hopf bifurcation followed by a two-frequency locked state.

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BRUCE, P. J. K., and H. BABINSKY. "Unsteady shock wave dynamics." Journal of Fluid Mechanics 603 (April 30, 2008): 463–73. http://dx.doi.org/10.1017/s0022112008001195.

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An experimental study of an oscillating normal shock wave subject to unsteady periodic forcing in a parallel-walled duct has been conducted. Measurements of the pressure rise across the shock have been taken and the dynamics of unsteady shock motion have been analysed from high-speed schlieren video (available with the online version of the paper). A simple analytical and computational study has also been completed. It was found that the shock motion caused by variations in back pressure can be predicted with a simple theoretical model. A non-dimensional relationship between the amplitude and frequency of shock motion in a diverging duct is outlined, based on the concept of a critical frequency relating the relative importance of geometry and disturbance frequency for shock dynamics. The effects of viscosity on the dynamics of unsteady shock motion were found to be small in the present study, but it is anticipated that the model will be less applicable in geometries where boundary layer separation is more severe. A movie is available with the online version of the paper.

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Journal articles on the topic 'Unsteady'

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