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Journal articles on the topic 'Unsteady simulation'

Author: Grafiati

Published: 28 June 2021

Last updated: 17 February 2022

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1

Wang, Zhi Gang, and Zhen Ning Zhang. "Modeling and Simulation of Unsteady Aerodynamics on a Morphing Wing." Applied Mechanics and Materials 427-429 (September 2013): 77–80. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.77.

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Modeling and simulation method of unsteady aerodynamics on morphing wings were investigated. The Unsteady Vortex Lattice Method is employed to model the unsteady aerodynamics of 3-D potential flow field surrounding the wing. An UVLM computer code was then developed and validated for numerical simulation. A morphing wing which changes its dihedral angle with constant angular velocity was investigated by the code, and the lift, induced drag, and pitching moment coefficients time histories were obtained. The results show that the UVLM code is an effective tool for simulations of unsteady aerodynamics on morphing wings.

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2

Torner, Benjamin, Lucas Konnigk, Sebastian Hallier, Jitendra Kumar, Matthias Witte, and Frank-Hendrik Wurm. "Large eddy simulation in a rotary blood pump: Viscous shear stress computation and comparison with unsteady Reynolds-averaged Navier–Stokes simulation." International Journal of Artificial Organs 41, no. 11 (June 13, 2018): 752–63. http://dx.doi.org/10.1177/0391398818777697.

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Purpose: Numerical flow analysis (computational fluid dynamics) in combination with the prediction of blood damage is an important procedure to investigate the hemocompatibility of a blood pump, since blood trauma due to shear stresses remains a problem in these devices. Today, the numerical damage prediction is conducted using unsteady Reynolds-averaged Navier–Stokes simulations. Investigations with large eddy simulations are rarely being performed for blood pumps. Hence, the aim of the study is to examine the viscous shear stresses of a large eddy simulation in a blood pump and compare the results with an unsteady Reynolds-averaged Navier–Stokes simulation. Methods: The simulations were carried out at two operation points of a blood pump. The flow was simulated on a 100M element mesh for the large eddy simulation and a 20M element mesh for the unsteady Reynolds-averaged Navier-Stokes simulation. As a first step, the large eddy simulation was verified by analyzing internal dissipative losses within the pump. Then, the pump characteristics and mean and turbulent viscous shear stresses were compared between the two simulation methods. Results: The verification showed that the large eddy simulation is able to reproduce the significant portion of dissipative losses, which is a global indication that the equivalent viscous shear stresses are adequately resolved. The comparison with the unsteady Reynolds-averaged Navier–Stokes simulation revealed that the hydraulic parameters were in agreement, but differences for the shear stresses were found. Conclusion: The results show the potential of the large eddy simulation as a high-quality comparative case to check the suitability of a chosen Reynolds-averaged Navier–Stokes setup and turbulence model. Furthermore, the results lead to suggest that large eddy simulations are superior to unsteady Reynolds-averaged Navier–Stokes simulations when instantaneous stresses are applied for the blood damage prediction.

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3

Wang, Ziwei, Xiong Jiang, Ti Chen, Yan Hao, and Min Qiu. "Numerical simulation of transonic compressor under circumferential inlet distortion and rotor/stator interference using harmonic balance method." Modern Physics Letters B 32, no. 12n13 (May 10, 2018): 1840021. http://dx.doi.org/10.1142/s0217984918400213.

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Simulating the unsteady flow of compressor under circumferential inlet distortion and rotor/stator interference would need full-annulus grid with a dual time method. This process is time consuming and needs a large amount of computational resources. Harmonic balance method simulates the unsteady flow in compressor on single passage grid with a series of steady simulations. This will largely increase the computational efficiency in comparison with the dual time method. However, most simulations with harmonic balance method are conducted on the flow under either circumferential inlet distortion or rotor/stator interference. Based on an in-house CFD code, the harmonic balance method is applied in the simulation of flow in the NASA Stage 35 under both circumferential inlet distortion and rotor/stator interference. As the unsteady flow is influenced by two different unsteady disturbances, it leads to the computational instability. The instability can be avoided by coupling the harmonic balance method with an optimizing algorithm. The computational result of harmonic balance method is compared with the result of full-annulus simulation. It denotes that, the harmonic balance method simulates the flow under circumferential inlet distortion and rotor/stator interference as precise as the full-annulus simulation with a speed-up of about 8 times.

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4

Adamczyk, J. J., M. L. Celestina, and Jen Ping Chen. "Wake-Induced Unsteady Flows: Their Impact on Rotor Performance and Wake Rectification." Journal of Turbomachinery 118, no. 1 (January 1, 1996): 88–95. http://dx.doi.org/10.1115/1.2836611.

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The impact of wake-induced unsteady flows on blade row performance and the wake rectification process is examined by means of numerical simulation. The passage of a stator wake through a downstream rotor is first simulated using a three-dimensional unsteady viscous flow code. The results from this simulation are used to define two steady-state inlet conditions for a three-dimensional viscous flow simulation of a rotor operating in isolation. The results obtained from these numerical simulations are then compared to those obtained from the unsteady simulation both to quantify the impact of the wake-induced unsteady flow field on rotor performance and to identify the flow processes which impact wake rectification. Finally, the results from this comparison study are related to an existing model, which attempts to account for the impact of wake-induced unsteady flows on the performance of multistage turbomachinery.

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5

Sznajder, Janusz, and Jerzy Zółtak. "APPLICATION OF AN EULER SOLVER TO SELECTED PROBLEMS IN FLIGHT DYNAMICS." Aviation 11, no. 2 (March 31, 2007): 13–22. http://dx.doi.org/10.3846/16487788.2007.9635956.

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Several applications of a Euler solver with the formulation of the flow equations in the noninertial reference system with steady and unsteady flow analysis are presented. The steady‐flow applications include determination of aerodynamic derivatives with respect to angular velocity and analysis of vortical flow over a delta wing at high angles of attack with the determination of aerodynamic coefficients and analysis of vortex breakdown. The unsteady flow analysis is applied in the simulation of a rapid manoeuvre for the determination of unsteady forces. The results of this simulation are compared with results of simulations using steady‐flow approximation in order to assess the advantages of unsteady flow analysis in the simulation of aircraft manoeuvres.

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6

Feng, Guang, Wei-zheng Chen, Xue-sen Chu, Zhi Wang, Ming-hui Zhang, and Wei-qi Chen. "Simulation of unsteady artificial supercavities." Journal of Hydrodynamics 22, S1 (October 2010): 862–68. http://dx.doi.org/10.1016/s1001-6058(10)60050-9.

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7

Hu, Le, Shu Jia Zhang, and Cheng Xu. "The Use of Steady Multi-Phase Position and Unsteady Computational Methods in the Numerical Simulation of Double-Suction Centrifugal Pump." Advanced Materials Research 181-182 (January 2011): 201–5. http://dx.doi.org/10.4028/www.scientific.net/amr.181-182.201.

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In order to compare the steady multi-phase and unsteady calculation in double-suction centrifugal pump application, this article simulates the internal turbulent flow of the 150S-50 double suction centrifugal pump. Numerical simulation uses realizable turbulence model, simulating with two methods of steady multi-phase and unsteady in 7 cases. Based on the numerical simulation, the head, shaft power, efficiency were calculated, the simulated performance curves of a double suction centrifugal pump is processed. The results show that: The results of unsteady simulation are closer with the experimental data.

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8

Münsterjohann, Sven, Jens Grabinger, Stefan Becker, and Manfred Kaltenbacher. "CAA of an Air-Cooling System for Electronic Devices." Advances in Acoustics and Vibration 2016 (October 20, 2016): 1–17. http://dx.doi.org/10.1155/2016/4785389.

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This paper presents the workflow and the results of fluid dynamics and aeroacoustic simulations for an air-cooling system as used in electronic devices. The setup represents a generic electronic device with several electronic assemblies with forced convection cooling by two axial fans. The aeroacoustic performance is computed using a hybrid method. In a first step, two unsteady CFD simulations using the Unsteady Reynolds-Averaged Navier-Stokes simulation with Shear Stress Transport (URANS-SST) turbulence model and the Scale Adaptive Simulation with Shear Stress Transport (SAS-SST) models were performed. Based on the unsteady flow results, the acoustic source terms were calculated using Lighthill’s acoustic analogy. Propagation of the flow-induced sound was computed using the Finite Element Method. Finally, the results of the acoustic simulation are compared with measurements and show good agreement.

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9

Salehian, Saman, and Reda R. Mankbadi. "Simulations of rocket launch noise suppression with water injection from impingement pad." International Journal of Aeroacoustics 19, no. 3-5 (June 2020): 207–39. http://dx.doi.org/10.1177/1475472x20930653.

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The focus of this work is on understanding the effect of water injection from the launch pad on the noise generated during rocket’s lift-off. To simplify the problem, we consider a supersonic jet impinging on a flat plate with water injection from the impingement plate. The Volume of Fluid model is adopted in this work to simulate the two-phase flow. A Hybrid Large Eddy Simulation – Unsteady Reynolds Averaged Simulation approach is employed to model turbulence, wherein Unsteady Reynolds Averaged Simulation is used near the walls, and Large Eddy Simulation is used elsewhere in the computational domain. The numerical issues associated with simulating the noise of two-phase supersonic flow are addressed. The pressure fluctuations on the impingement plate obtained from numerical simulations agree well with the experimental data. Furthermore, the predicted effect of water injection on the far-field broadband noise is consistent with that of the experiment. The possible mechanisms for noise reduction by water injection are discussed.

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10

Hassan, O., E. J. Probert, K. Morgan, and N. P. Weatherill. "Unsteady flow simulation using unstructured meshes." Computer Methods in Applied Mechanics and Engineering 189, no. 4 (September 2000): 1247–75. http://dx.doi.org/10.1016/s0045-7825(99)00376-x.

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11

Möller, S. I., E. Lundgren, and C. Fureby. "Large eddy simulation of unsteady combustion." Symposium (International) on Combustion 26, no. 1 (January 1996): 241–48. http://dx.doi.org/10.1016/s0082-0784(96)80222-0.

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12

Tang, Jing, Jian Zhang, Bin Li, and Nai-Chun Zhou. "Unsteady flow simulation with mesh adaptation." International Journal of Modern Physics B 34, no. 14n16 (April 20, 2020): 2040080. http://dx.doi.org/10.1142/s0217979220400809.

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Mesh adaptation is a reliable and effective method to improve the precision of flow simulation with computational fluid dynamics. Mesh refinement is a common technique to simulate steady flows. In order to dynamically optimize the mesh for transient flows, mesh coarsening is also required to be involved in an iterative procedure. In this paper, we propose a robust mesh adaptation method, both refinement and coarsening included. A data structure of [Formula: see text]-way tree is adopted to save and access the parent–children relationship of mesh elements. Local element subdivision is employed to refine mesh, and element mergence is devised to coarsen mesh. The unrefined elements adjacent to a refined element are converted to polyhedrons to eliminate suspending points, which can also prevent refinement diffusing from one refined element to its neighbors. Based on an adaptation detector for vortices recognizing, the mesh adaptation was integrated to simulate the unsteady flow around a tri-wedges. The numerical results show that the mesh zones where vortices located are refined in real time and the vortices are resolved better with mesh adaptation.

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13

Wang, Qiang, Wei Li, and Yongtao Yao. "Unsteady Coupled Heat Transfer Simulation of Unsteady numerical simulation of slot flow in anti-heating tile." IOP Conference Series: Earth and Environmental Science 651 (February 10, 2021): 022023. http://dx.doi.org/10.1088/1755-1315/651/2/022023.

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14

Zhao, Xiaoran, Zhengwei Wang, Yexiang Xiao, and Yongyao Luo. "Thermodynamic analysis of energy dissipation and unsteady flow characteristic in a centrifugal dredge pump under over-load conditions." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 13 (January 10, 2019): 4742–53. http://dx.doi.org/10.1177/0954406218824350.

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The present paper aims to investigate the energy dissipation related to unsteady flow phenomena inside a three-bladed impeller of a centrifugal dredge pump under over-load operating conditions. Three-dimensional unsteady numerical simulations of the centrifugal pump are performed by adopting the SAS SST-curvature correction turbulence model with the total energy equation. The simulating results are verified by comparing the performance results and pressure fluctuation with available experimental data. The unsteady flow patterns and energy dissipation in the rotating impeller are analysed by entropy distribution and pressure fluctuation spectra. A high-entropy area appears in the impeller flow passage when the discharge increases. It is indicated in the unsteady simulation results that a vortex flow with high entropy generates and detaches periodically, which causes the hydraulic energy loss under over-load operating conditions. In numerical simulations, a frequency as 3.3 times of rotating frequency is found in the pressure spectral analysis at 1.45 Q0 operating condition, which is related to the unsteady flow structure. The secondary flow near the volute tongue is found at 1.45 Q0 operating condition due to the large angle of attack when discharge increases.

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15

Sharma, O. P., G. F. Pickett, and R. H. Ni. "Assessment of Unsteady Flows in Turbines." Journal of Turbomachinery 114, no. 1 (January 1, 1992): 79–90. http://dx.doi.org/10.1115/1.2928001.

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The impacts of unsteady flow research activities on flow simulation methods used in the turbine design process are assessed. Results from experimental investigations that identify the impact of periodic unsteadiness on the time-averaged flows in turbines and results from numerical simulations obtained by using three-dimensional unsteady Computational Fluid Dynamics (CFD) codes indicate that some of the unsteady flow features can be fairly accurately predicted. Flow parameters that can be modeled with existing steady CFD codes are distinguished from those that require unsteady codes.

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16

Yao, Zhen Qiu, and Cheng Long Yang. "Numerical Simulation of Unsteady Flow for Variable-Pitch Vertical Axis Wind Turbine." Applied Mechanics and Materials 291-294 (February 2013): 490–95. http://dx.doi.org/10.4028/www.scientific.net/amm.291-294.490.

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Using computational fluid dynamics (CFD) software Fluent, numerical simulation for unsteady flow around the vertical axis wind turbine (VAWT) was performed, which was based on the UDF controlled sliding meshes method. And SST k-ω turbulent model and SIMPLE algorithm were used to solve the unsteady incompressible N-S equation. Velocity magnitude profile, pressure, the blade force and the torque had been obtained by doing this. The result shows this method can effectively simulate the unsteady flow field performance of the variable-pitch vertical axis wind turbine, and it provides a new method for variable-pitch vertical axis wind turbine’s simulations.

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17

Luo, Bo, Wuli Chu, Song Yan, Zhengjing Shen, and Haoguang Zhang. "Assessment of improved delayed detached eddy simulation in predicting unsteady flows and sound around a circular cylinder." Modern Physics Letters B 35, no. 23 (July 8, 2021): 2150384. http://dx.doi.org/10.1142/s021798492150384x.

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Unsteady flows in the field of engineering are usually calculated by the Unsteady Reynolds-Averaged Navier–Stokes (URANS) owing to the low requirements for computational efforts. However, the numerical resolution of URANS, especially in predicting the unsteady wake flows and sound, is still questionable. In this work, unsteady flow and sound calculations of a circular cylinder are carried out using Improved Delayed Detached Eddy Simulation (IDDES) and the Ffowcs Williams–Hawkings (FW-H) analogy. The predicted results of this calculation are compared with those from the previous studies in the literature in terms of the mean and RMS of the velocity components as well as the sound pressure. The results show that IDDES retains much of the numerical accuracy of the Large Eddy Simulation (LES) approach in predicting unsteady flows and noise while requiring a reduced computational resources in comparison to LES. It is believed that the IDDES can be applied to calculate the complex unsteady flows and flow generated sound with reasonable accuracy in engineering field, which can be used as a promising method for scale-resolving simulations to avoid the expensive computational requirements of LES.

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18

Michelassi, V., J. G. Wissink, and W. Rodi. "Direct numerical simulation, large eddy simulation and unsteady Reynolds-averaged Navier—Stokes simulations of periodic unsteady flow in a low-pressure turbine cascade: A comparison." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 217, no. 4 (January 1, 2003): 403–11. http://dx.doi.org/10.1243/095765003322315469.

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The unsteady periodic flow in a low-pressure (LP) prismatic turbine vane with incoming wakes is computed by direct numerical simulation (DNS), large eddy simulation (LES) and unsteady Reynolds-averaged Navier—Stokes simulations (URANSs). The results are compared with existing measurements at a Reynolds number Re = 5.18 × 104 which reveal the presence of a large unsteady stalled region on the suction side. Both DNS and LES suggest that the boundary layer separates while being still laminar, with subsequent turbulent reattachment. Several URANSs with and without a transition model and a constraint on the turbulence time-scale designed to prevent excessive production in the stagnation region are analysed and compared with the DNS and LES. The useful information provided by DNS and LES has made it possible to improve the results of the URANSs, which ensure a fair reproduction of the flow, especially in terms of blade load and losses, although they partly fail to detail the complex wake—boundary layer interaction in the separated flow region.

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19

LI, WEI, ZHONGYONG PAN, and WEIDONG SHI. "NUMERICAL INVESTIGATION OF PUMP-TURBINES WITH DIFFERENT BLADES AT PUMP CONDITIONS." Journal of Advanced Manufacturing Systems 11, no. 02 (December 2012): 143–50. http://dx.doi.org/10.1142/s0219686712500138.

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The undesirable performance of a positive slope curve usually appears for pump-turbines running as pumps at a low flow rate. The inner flow feature of pump-turbines with 6- and 7-blades runner is studied by both steady and unsteady simulations at pump conditions. According to the steady simulation investigation, obviously back flow vortex is found in the runner passage at the low flow rate zone where the positive slope curve forms. The flow rate at which the instable flow pattern happens of 6-blades runner is smaller than that of 7-blades one. By the unsteady simulation, at the low flow rate zone similar to the steady calculations and the tested data, a rotating stall with four rotating cells can be viewed by significant dynamic post-processing, whose rotation speed is much slower than that of the runner. Therefore, the back flow vortex of steady simulation and rotating stall of unsteady simulation can be used to investigate the runner quality at design stage.

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20

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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21

Guo, Zhong-Zhou, Gang Dai, Hua Yang, and Wei-Fang Chen. "Unsteady flow simulation of a variable-sweep morphing aircraft coupled with flight control system." International Journal of Modern Physics B 34, no. 14n16 (May 30, 2020): 2040073. http://dx.doi.org/10.1142/s0217979220400731.

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Morphing aircraft has adjustable aerodynamic shapes and is suitable for variable flight conditions. And there have been growing interests in recent years. However, the forces and moments are highly nonlinear, bringing challenges in design and modeling of flight control system (FCS). In this paper, unsteady Computational Fluid Dynamics (CFD) simulations are performed by solving the Arbitrary Lagrangian–Eulerian (ALE) governing equations on unstructured dynamic mesh, then unsteady aerodynamic characteristics of a variable-sweep morphing aircraft at hypersonic speed are acquired. The nonlinearity index theory is employed to analyze the nonlinearity of pitching moments. FCS is designed using nonlinear dynamic inversion control, taking attitude angles and sweep angle into consideration. Unsteady flow simulation is performed using unsteady CFD coupled with FCS. Cases of open and close loop morphing flight over the variation of sweep angle corresponding to flight conditions are studied. Results show that the nonlinearity of unsteady forces and moments are significant. The combination of unsteady CFD and FCS provides a powerful approach to the study of morphing aircraft.

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22

SUZUKI, TAKAO, HUI JI, and FUJIO YAMAMOTO. "Instability waves in a low-Reynolds-number planar jet investigated with hybrid simulation combining particle tracking velocimetry and direct numerical simulation." Journal of Fluid Mechanics 655 (May 17, 2010): 344–79. http://dx.doi.org/10.1017/s0022112010000893.

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Instability waves in a laminar planar jet are extracted using hybrid unsteady-flow simulation combining particle tracking velocimetry (PTV) and direct numerical simulation (DNS). Unsteady velocity fields on a laser sheet in a water tunnel are measured with time-resolved PTV; subsequently, PTV velocity fields are rectified in a least squares sense so that the equation of continuity is satisfied, and they are transplanted to a two-dimensional incompressible Navier–Stokes solver by setting a multiple of the computational time step equal to the frame rate of the PTV system. As a result, the unsteady hybrid velocity field approaches that of the measured one over time, and we can simultaneously acquire the unsteady pressure field. The resultant set of flow quantities satisfies the governing equations, and their resolution is comparable to that of numerical simulation with the noise level much lower than the original PTV data. From hybrid unsteady velocity fields, we extract eigenfunctions using bi-orthogonal decomposition as a spatial problem for viscous instability. We also investigate stability/convergence characteristics of the hybrid simulation referring to linear stability analysis.

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23

Hariharan, Nathan, and Lakshmi N. Sankar. "Unsteady Overset Simulation of Rotor-Airframe Interaction." Journal of Aircraft 40, no. 4 (July 2003): 662–74. http://dx.doi.org/10.2514/2.3170.

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24

JIMBO, Tomohiko, Debasish BISWAS, Yasuyuki YOKONO, and Yoshiki NIIZEKI. "Unsteady Viscous Flow Simulation around Turbine Blade." Journal of the Visualization Society of Japan 27, Supplement1 (2007): 93–94. http://dx.doi.org/10.3154/jvs.27.supplement1_93.

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25

Mani, M. "Hybrid Turbulence Models for Unsteady Flow Simulation." Journal of Aircraft 41, no. 1 (January 2004): 110–18. http://dx.doi.org/10.2514/1.36.

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26

McCorquodale, J. A., E. M. Yuen, Z. Vitasovic, and R. Samstag. "Numerical Simulation of Unsteady Conditions in Clarifiers." Water Quality Research Journal 26, no. 2 (May 1, 1991): 201–22. http://dx.doi.org/10.2166/wqrj.1991.013.

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Abstract Primary and secondary clarifiers seldom operate with constant hydraulic and solids loading; in many plants there are significant diurnal variations in flows and solids loads. Secondary clarifiers are subject to density currents due to the relatively high concentrations of suspended solids in the influent. In this study a computer program for unsteady flow in a centre-fed circular clarifier was used to predict the effects of unsteady flow on the clarifier performance. Two cases were considered, namely: diurnal variation in flow at a constant MLSS concentration and a sudden increase in the MLSS. In both cases, the results of the model simulations indicated that clarifier performance is significantly affected by the unsteadiness of the flow; a steady state analysis at the peak flow gave lower effluent concentrations than either the diurnal flow or the step increase in the MLSS. The model simulations suggested that this effect was greater for peripheral weirs than in-board launders.

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27

Goncalves, Eric, Jean Decaix, and Regiane Fortes Patella. "Unsteady simulation of cavitating flows in Venturi." Journal of Hydrodynamics 22, S1 (October 2010): 711–16. http://dx.doi.org/10.1016/s1001-6058(10)60026-1.

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28

Bozza, F., and A. Gimelli. "Unsteady 1D Simulation of a Turbocharger Compressor." SAE International Journal of Engines 2, no. 1 (April 20, 2009): 189–98. http://dx.doi.org/10.4271/2009-01-0308.

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29

Auzyak, A. G., V. I. Budin, and F. V. Dremov. "Simulation of helicopter motion in unsteady conditions." Russian Aeronautics (Iz VUZ) 53, no. 3 (September 2010): 271–76. http://dx.doi.org/10.3103/s1068799810030050.

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30

Schafer, O. "Simulation of unsteady compressible flow in turbomachinery." Progress in Computational Fluid Dynamics, An International Journal 2, no. 1 (2002): 1. http://dx.doi.org/10.1504/pcfd.2002.003212.

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31

Iaccarino, G., A. Ooi, P. A. Durbin, and M. Behnia. "Reynolds averaged simulation of unsteady separated flow." International Journal of Heat and Fluid Flow 24, no. 2 (April 2003): 147–56. http://dx.doi.org/10.1016/s0142-727x(02)00210-2.

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32

HSU, A. T., G. HE, and Y. GUO. "Unsteady Simulation of a Jet-in-crossflow." International Journal of Computational Fluid Dynamics 14, no. 1 (January 2000): 41–53. http://dx.doi.org/10.1080/10618560008940714.

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33

Bénard, N., R. Perrault, and D. Coisne. "Unsteady 3D simulation of intra stent flow." Computer Methods in Biomechanics and Biomedical Engineering 8, sup1 (September 2005): 25–26. http://dx.doi.org/10.1080/10255840512331388083.

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34

Schwarze, R. "Unsteady RANS simulation of oscillating mould flows." International Journal for Numerical Methods in Fluids 52, no. 8 (2006): 883–902. http://dx.doi.org/10.1002/fld.1208.

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35

Allen, C. B. "Parallel simulation of unsteady hovering rotor wakes." International Journal for Numerical Methods in Engineering 68, no. 6 (2006): 632–49. http://dx.doi.org/10.1002/nme.1723.

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36

Frey, A., C. Hall, and T. Porsching. "Numerical simulation of confined unsteady aerodynamical flows." International Journal for Numerical Methods in Engineering 24, no. 7 (July 1987): 1233–50. http://dx.doi.org/10.1002/nme.1620240702.

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37

van Buuren, Ren�, Hans Kuerten, and Bernard J. Geurts. "Implicit time accurate simulation of unsteady flow." International Journal for Numerical Methods in Fluids 35, no. 6 (2001): 687–720. http://dx.doi.org/10.1002/1097-0363(20010330)35:6<687::aid-fld110>3.0.co;2-q.

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38

Ahmed, Ridha Alwan. "Simulation of Unsteady Flow Around a Cylinder." Wasit Journal of Engineering Sciences 3, no. 2 (October 1, 2015): 28–49. http://dx.doi.org/10.31185/ejuow.vol3.iss2.38.

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In this paper, the phenomena of vortex shedding from the circular cylinder surface has been studied at several Reynolds Numbers (40≤Re≤ 300).The 2D, unsteady, incompressible, Laminar flow, continuity and Navier Stokes equations have been solved numerically by using CFD Package FLUENT. In this package PISO algorithm is used in the pressure-velocity coupling. The numerical grid is generated by using Gambit program. The velocity and pressure fields are obtained upstream and downstream of the cylinder at each time and it is also calculated the mean value of drag coefficient and value of lift coefficient .The results showed that the flow is strongly unsteady and unsymmetrical at Re>60. The results have been compared with the available experiments and a good agreement has been found between them

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39

Osada, Takuya, and Reima Iwatsu. "Numerical Simulation of Unsteady Driven Cavity Flow." Journal of the Physical Society of Japan 80, no. 9 (September 15, 2011): 094401. http://dx.doi.org/10.1143/jpsj.80.094401.

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Kulish, Vladimir V., Jose´ L. Lage, Connie C. W. Hsia, and Robert L. Johnson,. "Three-dimensional, Unsteady Simulation of Alveolar Respiration." Journal of Biomechanical Engineering 124, no. 5 (September 30, 2002): 609–16. http://dx.doi.org/10.1115/1.1504445.

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A novel macroscopic gas transport model, derived from fundamental engineering principles, is used to simulate the three-dimensional, unsteady respiration process within the alveolar region of the lungs. The simulations, mimicking the single-breath technique for measuring the lung diffusing capacity for carbon-monoxide (CO), allow the prediction of the red blood cell (RBC) distribution effects on the lung diffusing capacity. Results, obtained through numerical simulations, unveil a strong relationship between the type of distribution and the lung diffusing capacity. Several RBC distributions are considered, namely: normal (random), uniform, center-cluster, and corner-cluster red cell distributions. A nondimensional correlation is obtained in terms of a geometric parameter characterizing the RBC distribution, and presented as a useful tool for predicting the RBC distribution effect on the lung diffusing capacity. The effect of red cell movement is not considered in the present study because CO does not equilibrate with capillary blood within the time spent by blood in the capillary. Hence, blood flow effect on CO diffusion is expected to be only marginal.

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Baikov, N. D., and A. G. Petrov. "Numerical Simulation of Unsteady Capillary-Gravity Waves." Doklady Physics 63, no. 10 (October 2018): 430–34. http://dx.doi.org/10.1134/s1028335818100087.

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ASHURST, WM T. "Vortex Simulation of Unsteady Wrinkled Laminar Flames." Combustion Science and Technology 52, no. 4-6 (April 1987): 325–51. http://dx.doi.org/10.1080/00102208708952582.

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Tran, T. D., B. Nennemann, T. C. Vu, and F. Guibault. "Numerical simulation of unsteady sheet/cloud cavitation." IOP Conference Series: Earth and Environmental Science 22, no. 5 (March 1, 2014): 052012. http://dx.doi.org/10.1088/1755-1315/22/5/052012.

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He, Lei, and Spyros A. Kinnas. "Numerical simulation of unsteady propeller/rudder interaction." International Journal of Naval Architecture and Ocean Engineering 9, no. 6 (November 2017): 677–92. http://dx.doi.org/10.1016/j.ijnaoe.2017.02.004.

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Krantz, Werner, Jürgen-Oliver Pitz, Daniel Stoll, and Minh-Tri Nguyen. "Simulation of driving under unsteady crosswind conditions." ATZ worldwide 116, no. 2 (January 14, 2014): 46–51. http://dx.doi.org/10.1007/s38311-014-0024-3.

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Hamed, M. S., and J. M. Floryan. "Numerical Simulation of Unsteady Nonisothermal Capillary Interfaces." Journal of Computational Physics 145, no. 1 (September 1998): 110–40. http://dx.doi.org/10.1006/jcph.1998.6023.

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Shen, Xiaobin, Huanfa Wang, Guiping Lin, Xueqin Bu, and Dongsheng Wen. "Unsteady simulation of aircraft electro-thermal deicing process with temperature-based method." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 2 (August 2, 2019): 388–400. http://dx.doi.org/10.1177/0954410019866066.

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Considering the mass and energy sources carried by the accumulated ice layer, an unsteady heat and mass transfer model of the runback water film on the deicing surface is established to simulate aircraft electro-thermal deicing process. With the extension of the freezing coefficient to the transient calculation, the coupled heat transfer of the runback water and the solid skin is solved at each time step by a temperature-based method. Unsteady numerical simulation is carried out for the electro-thermal deicing system of a NACA 0012 airfoil. The temperature variations with time are in acceptable agreement with the literature data, and the unsteady temperature-based deicing model is verified. The calculation results of temperature, runback water flux and ice thickness on the deicing surface are analyzed at different time points, and it is shown that the unsteady electro-thermal deicing model can capture the main features of the icing, ice melting and re-freezing processes in the transient deicing simulations.

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Fernández-Pato, J., and P. García-Navarro. "Finite volume simulation of unsteady water pipe flow." Drinking Water Engineering and Science 7, no. 2 (August 21, 2014): 83–92. http://dx.doi.org/10.5194/dwes-7-83-2014.

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Abstract. The most commonly used hydraulic network models used in the drinking water community exclusively consider fully filled pipes. However, water flow numerical simulation in urban pipe systems may require to model transitions between surface flow and pressurized flow in steady and transient situations. The governing equations for both flow types are different and this must be taken into account in order to get a complete numerical model for solving dynamically transients. In this work, a numerical simulation tool is developed, capable of simulating pipe networks mainly unpressurized, with isolated points of pressurization. For this purpose, the mathematical model is reformulated by means of the Preissmann slot method. This technique provides a reasonable estimation of the water pressure in cases of pressurization. The numerical model is based on the first order Roe's scheme, in the frame of finite volume methods. The novelty of the method is that it is adapted to abrupt transient situations, with subcritical and supercritical flows. The validation has been done by means of several cases with analytic solutions or empirical laboratory data. It has also been applied to some more complex and realistic cases, like junctions or pipe networks.

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Bo¨lcs, A., T. H. Fransson, and M. F. Platzer. "Numerical Simulation of Inviscid Transonic Flow Through Nozzles With Fluctuating Back Pressure." Journal of Turbomachinery 111, no. 2 (April 1, 1989): 169–80. http://dx.doi.org/10.1115/1.3262253.

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The study presents a numerical method, based on the flux vector splitting approach, to the problem of unsteady one-dimensional and two-dimensional inviscid transonic flows, with emphasis on the numerical determination of the shock position, through nozzles with time-varying back pressure. The model is first validated by comparison with exact (one dimension) and numerical (two dimensions) steady-state solutions. It is thereafter applied to the problem of time-fluctuating back pressure in quasi-one-dimensional and two-dimensional nozzles. The one-dimensional results are validated by comparison with a small perturbation analytical unsteady solution, whereafter a few sample cases are presented with the objective of understanding fundamental aspects of unsteady transonic flows. It is concluded that both the amplitude and frequency of the imposed fluctuating exit pressure are important parameters for the location of the unsteady shock. It is also shown that the average unsteady shock position is not necessarily identical with the steady-state position, and that the unsteady shock may, under certain circumstances, propagate upstream into the subsonic flow domain. The pressure jump over the shock, as well as the unsteady post-shock pressure, is different for identical shock positions during the cycle of fluctuation, which implies that an unsteady shock movement, imposed by oscillating back pressure, may introduce a significant unsteady lift and moment. This may be of importance for flutter predictions. It is also noted that, although the sonic velocity is obtained in the throat of steady-state, quasi-one-dimensional flow, this is not necessarily true for the unsteady solution. During part of the period with fluctuating back pressure, the flow velocity may be subsonic at the throat and still reach a supersonic value later in the nozzle. This phenomenon depends on the frequency and amplitude of the imposed fluctuation, as well as on the nozzle geometry.

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Petit, Olivier, and Håkan Nilsson. "Numerical Investigations of Unsteady Flow in a Centrifugal Pump with a Vaned Diffuser." International Journal of Rotating Machinery 2013 (2013): 1–14. http://dx.doi.org/10.1155/2013/961580.

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Computational fluid dynamics (CFD) analyses were made to study the unsteady three-dimensional turbulence in the ERCOFTAC centrifugal pump test case. The simulations were carried out using the OpenFOAM Open Source CFD software. The test case consists of an unshrouded centrifugal impeller with seven blades and a radial vaned diffuser with 12 vanes. A large number of measurements are available in the radial gap between the impeller and the diffuse, making this case ideal for validating numerical methods. Results of steady and unsteady calculations of the flow in the pump are compared with the experimental ones, and four different turbulent models are analyzed. The steady simulation uses the frozen rotor concept, while the unsteady simulation uses a fully resolved sliding grid approach. The comparisons show that the unsteady numerical results accurately predict the unsteadiness of the flow, demonstrating the validity and applicability of that methodology for unsteady incompressible turbomachinery flow computations. The steady approach is less accurate, with an unphysical advection of the impeller wakes, but accurate enough for a crude approximation. The different turbulence models predict the flow at the same level of accuracy, with slightly different results.

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