Accepted Manuscripts

Marcus Jansson, Magnus Andersson, Maria Pettersson and Matts Karlsson
J. Fluids Eng   doi: 10.1115/1.4043854
Cavitation erosion through water hammer and column separation is a major concern in hydraulic applications such as percussive rock drilling. Cavitation aspects must be considered both in late and early design stages, which require deep knowledge and tools for prediction. In this study, an oil-hydraulic test equipment for water hammer assessment was designed using state-of-the-art simulation tools. Several tests were performed, with and without column separation, showing good repeatability on measured pressures. At higher flow rates, column separation was the dominating feature and several high-pressure peaks with subsequent time delay reduction could be observed. These patterns were affected by the oil temperature, with most substantial changes at lower temperature ranges (<32 °C). Standard transmission line simulations managed to predict the water hammer, but as expected not the column separation which is the theme of future work using this set-up.
TOPICS: Separation (Technology), Water hammer, Pipe flow, Simulation, Temperature, Flow (Dynamics), Drilling, Testing equipment, Cavitation, High pressure (Physics), Cavitation erosion, Design, Delays, Rocks, Manual transmissions
Donald P. Rizzetta and Miguel Visbal
J. Fluids Eng   doi: 10.1115/1.4043859
Numerical calculations were carried out to investigate control of transition on a flat plate by means of local dynamic surface deformation. The configuration and flow conditions are similar to a previous computation which simulated transition mitigation. Physically, the surface modification may be produced by piezoelectrically-driven actuators located below a compliant aerodynamic surface, which have been employed experimentally. One actuator is located in the upstream plate region, and oscillated at the most unstable frequency of 250 Hz to develop disturbances representing Tollmien-Schlichting instabilities. A controlling actuator is placed downstream, and oscillated at the same frequency, but with an appropriate phase shift and modified amplitude to decrease disturbance growth and delay transition. While the downstream controlling actuator is two-dimensional (spanwise invariant), several forms of upstream disturbances were considered. These included disturbances which were strictly two-dimensional, those which were modulated in amplitude, and those which had a spanwise variation of the temporal phase shift. Direct numerical simulations were obtained by solution of the three-dimensional compressible Navier-Stokes equations, utilizing a high-fidelity computational scheme and an implicit time- marching approach. A previously devised empirical process was applied for determining the optimal parameters of the controlling actuator. Results of the simulations are described, features of the flowfields elucidated, and comparisons made between solutions of the uncontrolled and controlled cases for the respective incoming disturbances. It is found that the disturbance growth is mitigated and transition is delayed for all forms of the upstream perturbations, substantially reducing the skin friction.
TOPICS: Surface deformation, Delays, Actuators, Phase shift, Navier-Stokes equations, Engineering simulation, Computation, Skin friction (Fluid dynamics), Flow (Dynamics), Computer simulation, Simulation, Flat plates
Majdi Chaari, Afef Fekih, Abdennour C. Seibi and Jalel Ben Hmida
J. Fluids Eng   doi: 10.1115/1.4043858
Real-time monitoring of pressure and flow in multiphase flow applications is a critical problem given its economic and safety impacts. Using physics-based models has long been computationally expensive due to the spatial-temporal dependency of the variables and the nonlinear nature of the governing equations. This paper proposes a new reduced-order modeling approach for transient gas-liquid flow in pipes. In the proposed approach, artificial neural networks are considered to predict holdup and pressure drop at steady-state, from which properties of the two-phase mixture are derived. The dynamic response of the mixture is then estimated using a dissipative distributed-parameter model. The proposed approach encompasses all pipe inclination angles and flow conditions, does not require a spatial discretization of the pipe, and is numerically stable. To validate our model, we compared its dynamic response to that of OLGA©, the leading multiphase flow dynamic simulator. The obtained results showed a good agreement between both models under different pipe inclinations and various levels of gas volume fractions. In addition, the proposed model reduced the computational time by four to six folds compared to OLGA©. The above attribute makes it ideal for real-time monitoring and fluid flow control applications.
TOPICS: Pipes, Two-phase flow, Dynamic models, Flow (Dynamics), Multiphase flow, Dynamic response, Pressure drop, Steady state, Transients (Dynamics), Modeling, Artificial neural networks, Safety, Physics, Pressure, Fluid dynamics
Mohammad Mahdi Kabiri, mohammadreza Nikoomanesh, Pouya Nouraei Danesh and Mohammad Ali Goudarzi
J. Fluids Eng   doi: 10.1115/1.4043855
Proper evaluation of forces exerted on a solid boundary by liquid sloshing is difficult. If the free board in a liquid storage tank is insufficient, the sloshing waves caused by seismic excitation will collide with the tank roof and may cause major damage. The current study investigated the sloshing wave impact force (SWIF) in full-scale liquid storage tanks using numerical simulation based on the lattice Boltzmann method. Several shaking table tests have been conducted on a small-scale rectangular tank to validate the numerical model. The results of a standard dam break test have been used to express the validity of the proposed numerical model. This comparison confirms the validity of the numerical strategy for simulating the effect of sloshing. After validating the numerical model, it has been applied to a practical parametric study of SWIF in full-scale liquid tanks. The results of numerical simulation indicate that the simplified method recommended by related codes and standards for calculating SWIF in liquid tanks significantly underestimates the sloshing force. This confirms that the dynamic nature of sloshing should be considered in the design process of liquid storage tanks.
TOPICS: Stress, Sloshing, Wave forces, Computer simulation, Storage tanks, Waves, Design, Roofs, Engineering standards, Lattice Boltzmann methods, Damage, Excitation, Dams
Shi-cong Li, Xiao-yu Wang, Jing He, Mei Lin and Hanbing Ke
J. Fluids Eng   doi: 10.1115/1.4043803
An experimental study is carried out to investigate the flow characteristics downstream of the trailing edge of the horizontal vanes mounted at the branch entrance of a T-junction duct by means of particle image velocimetry (PIV). The measured region starts at the trailing edge of the vanes and ends at about 1.26D (hydraulic diameter) length downstream of the branch duct. The velocity field is obtained across a number of vertical height planes (z/D=±0.2, 0 and -0.4) under different flow conditions (cross velocity: uc=30-50 m/s; velocity ratio: R=0.08-0.18). The instantaneous flow results show that Kelvin-like vortices with counterclockwise direction appear at the heights of z/D=±0.2 and 0, and that a separation bubble is formed at the upper wall of the branch duct at the same heights, respectively. As for near wall z/D=-0.4, one large vortex is observed at the downstream channel, but the separation bubble vanishes as the branching Reynolds number is increased to 3.6×104. The time-average flow field is slightly different from that of instantaneous flow field. In addition, the vorticity distribution indicates that two significant vortex sheet layers with negative and positive values are found at the high velocity ratio or high cross velocity, and the normalized vorticity strength increases with increasing velocity ratio and decreases with increasing cross velocity except at z/D=-0.4.
TOPICS: Flow (Dynamics), Ducts, Junctions, Vortices, Bubbles, Vorticity, Separation (Technology), Particulate matter, Reynolds number
Technical Brief  
Hairui Wang and Ning Zhang
J. Fluids Eng   doi: 10.1115/1.4043804
In this study, a hydrodynamic and salinity transport model were developed for simulations of Sabine Lake water system located on the Texas-Louisiana border. The target simulation area includes several major water bodies, such as Sabine Lake, Sabine River, Sabine Pass, Sabine Neches Canal (Ship Channel), and part of Gulf Intracoastal Waterway (GIWW) and Sabine River Diversion Canal (SRDC). The SRDC supplies fresh water to the area industry, mainly petrochemical. High salinity in SRDC could significantly affect the daily production of the industry. 2-D depth-averaged shallow water equation set and 2-D depth-averaged salinity transport equation were used for developing the hydrodynamic and salinity transport numerical models in order to carry out the simulation. The major purposes of this study are to calibrate and validate hydrodynamic and salinity transport model in order to assess and predict the salinity in SRDC under severe weather conditions such as hurricane storm surges in future study. Measurement data from NOAA and USGS were used to calibrate the boundary conditions as well as to validate the model. Boundary conditions were calibrated at locations in Sabine Pass and in the north edge of the lake by using water-surface elevation data. Hydrodynamic model was validated at the USGS location using water-surface elevation data. Then the simulation estimations of water surface level and salinity were compared at three locations, and results show the accuracy of the validated model. Parallel computing was conducted in this study as well and computational efficiency was compared.
TOPICS: Hydrodynamics, Calibration, Water, Lakes, Simulation, Boundary-value problems, Canals, Rivers, Petrochemicals, Computer simulation, Shallow water equations, Ships, Storms, Surges
Drummond Biles, Alireza Ebadi, Michael P. Allard and Chris White
J. Fluids Eng   doi: 10.1115/1.4043773
A feedback controlled thermal wall plate designed to investigate thermal boundary layer flows is described and validated. The unique capabilities of the design are the ability to modify the thermal boundary conditions in a variety of ways or to hold the wall-temperature fixed even when the flow above the wall is unsteady and strongly three-dimensional. These capabilities allow for the generation and study of thermal transport in non-equilibrium boundary layer flows driven by different perturbations and of varying complexity. The thermal wall plate and the experimental facility in which the thermal wall plate is installed are first described. The wall-plate is then validated in a zero-pressure-gradient (ZPG) boundary layer flow for conditions of a uniform wall temperature and a temperature step. It is then shown that the wall temperature can be held constant even when a hemisphere body is placed on the wall that produces large localized variations in the convective heat transfer coefficient. Lastly, since the thermal wall plate is intended to support the study of thermal transport in a variety of non-equilibrium boundary layer flow, several possible experimental configurations are presented and described.
TOPICS: Design, Thermal boundary layers, Flow (Dynamics), Boundary layers, Wall temperature, Equilibrium (Physics), Pressure, Temperature, Convection, Boundary-value problems, Feedback
Tong Shuiguang, Zhao Hang, Liu Huiqin, Yu Yue, Li Jinfu and Cong Feiyun
J. Fluids Eng   doi: 10.1115/1.4043775
In this paper, the hydraulic efficiency optimization calculation method of a 10-stage centrifugal pump is researched. According to the hydraulic loss model, a multi-objective optimization calculation method based on surrogate models is proposed. In order to study the highly nonlinear relationship between key design variables and centrifugal pump external characteristic values, this paper builds the quadratic response surface, the radial basis Gaussian response surface and Kriging three surrogate models using CFD simulation analysis. Two types of calculation models (hydraulic loss model and three surrogate models) combined NSGA-? genetic algorithm are applied to optimize the key design variables and to find the optimal solution of each model. The accuracy and effectiveness of the efficiency optimization methods based on the two types of calculation models are compared and analyzed. The results show that the calculation method of hydraulic loss model based on the semi-theoretical and semi-empirical formula is less time-consuming but inaccurate. In contrast, the optimization method based on surrogate models using CFD simulation is accurate. What's more, comparing the surrogate models, the results based on the complete quadratic response surface model which makes the efficiency of the first stage centrifugal pump reach 77.26% are more accurate.
TOPICS: Centrifugal pumps, Pareto optimization, Response surface methodology, Optimization, Computational methods, Computational fluid dynamics, Design, Simulation, Simulation analysis, Genetic algorithms
Jane Alexander, Pedro Lee, Mark Davidson, HF Duan, Zhao Li, Ross Murch, Silvia Meniconi and Bruno Brunone
J. Fluids Eng   doi: 10.1115/1.4043776
Entrapped air in pipeline systems can compromise the operation of the system by blocking flow and raising pumping costs. Fluid transients are a potential tool for characterizing entrapped air pockets, and a numerical model which is able to accurately predict transient pressures for a given air volume represents an asset to the diagnostic process. This paper presents a detailed study on our current capability for modelling and predicting the dynamics of an inline air pocket, and is one of a series of articles within a broader context on air pocket dynamics. This paper presents an assessment of the accuracy of the variable wave speed and accumulator models for modelling air pockets. The variable wave speed model was found to be unstable for the given conditions, while the accumulator model is affected by amplitude and time delay errors. The time delay error could be partially overcome by combining the two models.
TOPICS: Computer simulation, Unsteady flow, Waves, Dynamics (Mechanics), Modeling, Delays, Errors, Secondary cells, Pipeline systems, Flow (Dynamics), Transients (Dynamics)
David T Fanning, Steven E. Gorrell, Daniel Maynes and Kerry Oliphant
J. Fluids Eng   doi: 10.1115/1.4043770
Inducers are used as a first stage in pumps to minimize cavitation and allow the pump to operate at lower inlet head conditions. Inlet flow recirculation or backflow in the inducer occurs at low flow conditions and can lead to instabilities and cavitation-induced head breakdown. Backflow of an inducer with a tip clearance of t = 0.32%, and with no tip clearance is examined with a series of CFD simulations. Removing the tip clearance eliminates tip leakage flow; however, backflow is still observed. In fact, the no tip clearance case showed a 37% increase in the length of the upstream backflow penetration. Tip leakage flow does instigate a smaller secondary leading edge tip vortex that is separate from the much larger backflow structure. A comprehensive analysis of these simulations suggests that blade inlet diffusion, not tip leakage flow, is the fundamental mechanism leading to the formation of backflow.
TOPICS: Diffusion (Physics), Leakage, Clearances (Engineering), Leakage flows, Flow (Dynamics), Engineering simulation, Pumps, Simulation, Cavitation, Wake turbulence, Computational fluid dynamics, Blades
Yangwei Liu, Luyang Zhong and Li-peng Lu
J. Fluids Eng   doi: 10.1115/1.4043774
Tip leakage vortex (TLV) has a large impact on compressor performance and should be accurately predicted by CFD methods. New approaches of turbulence modelling, such as DDES, have been proposed, the computational resources of which can be reduced much more than for LES. In this paper, the numerical simulations of the rotor in a low-speed large-scale axial compressor based on DDES and URANS are performed, thus improving our understanding of the TLV dynamic mechanisms and discrepancy of these two methods. We compared the influence of different time steps in the URANS simulation. The widely used long time step makes the unsteadiness extremely weak. The short time step shows a better result close to DDES. The time-step scale is related to the URANS unsteadiness and should be carefully selected. In the time-averaged flow, the TLV in DDES dissipates faster, which has a more similar structure to the experiment. Then, the time-averaged and instantaneous results are compared to divide the TLV into three parts. URANS cannot give the loss of stability and evolution details of TLV. The fluctuation velocity spectra show that the amplitude of high frequencies becomes obvious downstream from the TLV, where it loses stability. Last, the anisotropy of the Reynolds stress of these two methods is analyzed through the Lumley triangle to see the distinction between the methods and obtain the Reynolds stress. The results indicate that the TLV latter part in DDES is anisotropic, while in URANS it is isotropic.
TOPICS: Compressors, Rotors, Leakage flows, Delay differential equations, Stability, Stress, Anisotropy, Computational fluid dynamics, Modeling, Flow (Dynamics), Spectra (Spectroscopy), Turbulence, Computer simulation, Leakage, Vortices, Simulation
William Kirkland
J. Fluids Eng   doi: 10.1115/1.4043717
This paper demonstrates the usefulness of treating subsonic Fanno flow (adiabatic flow with friction of a perfect gas in a constant-area pipe) as a polytropic process. It is shown that the polytropic model allows an explicit equation for mass flow rate to be developed. The concept of the energy transfer ratio is used to develop a close approximation to the polytropic index. Explicit equations for mass flow rate and net expansion factor in terms of upstream properties and pressure ratio are developed for Fanno and isothermal flows. An approximation for choked flow is also presented. The deviation of the results of this polytropic approximation from the values obtained from a traditional gas dynamics analysis of subsonic Fanno flow is quantified and discussed, and a typical design engineering problem is analyzed using the new method.
TOPICS: Friction, Pipes, Approximation, Compressible flow, Flow (Dynamics), Pressure, Energy transformation, Gasdynamics, Design engineering
Diego /Alberto Lozano Jimenez, V M KRUSHNARAO Kotteda, Vinod Kumar and Venkata S Rao Gudimetla
J. Fluids Eng   doi: 10.1115/1.4043706
The effects of a laser beam propagating through atmospheric turbulence are investigated using the phase screen approach. Turbulence effects are modeled by the Kolmogorov description of the energy cascade theory and outer scale effect are implemented by the von Kármán refractive power spectral density. In this study we analyze a plane wave propagating through varying atmospheric horizontal paths. An important consideration for the laser beam propagation through a long atmospheric path is the random variations in the refractive index due to atmospheric turbulence. To characterize the random behavior statistical analysis of the phase data and related metrics are examined at the output signal. We train a machine learning algorithm in TensorFlow library with the data at varying propagation lengths, outer scale lengths and levels of turbulence intensity to predict statistical parameters that describe the atmospheric turbulence effects on laser propagation. TensorFlow is an interface for demonstrating machine learning algorithms and an implementation for executing such algorithms on a wide variety of heterogeneous systems, ranging from mobile devices such as phones and tablets up to large-scale distributed systems and thousands of computational devices such as GPU cards. The library contains a wide variety of algorithms including training and inference algorithms for deep neural network models. Therefore, it has been used for deploying machine learning systems in many fields including speech recognition, computer vision, natural language processing, and text mining.
TOPICS: Artificial intelligence, Lasers, Turbulence, Algorithms, Machine learning, Laser beams, Refractive index, Spectral energy distribution, Cascades (Fluid dynamics), Waves, Computers, Natural language processing, Neural network models, Signals, Statistical analysis, Text analytics, Trains, Graphics processing units
Karsten Hasselmann, Stefan aus der Wiesche and Eugeny Kenig
J. Fluids Eng   doi: 10.1115/1.4043707
An optimization study based on computational fluid dynamics (CFD) in combination with Stratford's analytical separation criterion was developed for the design of piece-wise conical contraction zones and nozzles. The risk of flow separation was formally covered by a newly introduced dimensionless separation number. The use of this separation number can be interpreted as an adaption of Stratford's separation criterion to piece-wise conical nozzles. In the nozzle design optimization process, the risk of flow separation was reduced by minimizing the separation number. It was found that the flow-optimized piece-wise conical nozzle did not correspond to a direct geometric approximation of an ideal polynomial profile. In fact, it was beneficial to reduce the flow deflection in the outlet region for a piece-wise conical nozzle to increase the nozzle performance. In order to validate the novel design method, large-scale tests for different nozzle designs were conducted by means of a wind tunnel test facility. The measured velocity profiles and wall pressure distributions agreed well with the CFD predictions.
TOPICS: Nozzles, Optimization, Separation (Technology), Computational fluid dynamics, Design, Flow separation, Flow (Dynamics), Risk, Pressure, Polynomials, Test facilities, Wind tunnels, Design methodology, Approximation, Deflection
Brian T. Bohan, Marc D. Polanka and James L. Rutledge
J. Fluids Eng   doi: 10.1115/1.4043576
This study quantified the performance and fluid disbursal capabilities of several fluidic oscillator variations injecting from the face of a backward-facing step. These devices were designed as a replacement for a pair of non-oscillating fuel injector jets in an Ultra-Compact Combustor. However, these results have relevance whenever fluid is injected from the face of a backward-facing step making the oscillator performance widely applicable. The oscillators were tested with and without co-flow and at varying co-flow velocities which controlled the strength of the recirculation behind the backward-facing step. The fluidic oscillators investigated included a single as well as paired oscillators that produced in-phase and out-of-phase synchronized jets. The injected fluid disbursal was found to be dependent on the velocity ratio of the freestream air and the injecting jet velocity. Additionally, the oscillation angle was found to be a function of Reynolds number due to the interaction of the oscillating jet with the walls of the models used in the present study. Finally, the oscillation frequency was found to be independent of Reynolds number, throat aspect ratio, working gas, and model scale which resulted in a Strouhal number of 0.017. This result was supported by non-dimensionalizing the published data from several other studies.
TOPICS: Jets, Fluids, Reynolds number, Oscillations, Flow (Dynamics), Combustion chambers, Fuel injectors
Fen Lai, Yu Wang, Saeed A. El-Shahat, Guojun Li and Xiangyuan Zhu
J. Fluids Eng   doi: 10.1115/1.4043580
Solid particle erosion is a serious issue in centrifugal pumps that may result in economic losses. Erosion prediction in centrifugal pump is complex because the flow field inside it is 3D unsteady and erosion can be affected by numerous factors. In this study, solid particle erosion of the entire centrifugal pump for liquid-solid flow is investigated numerically. Two-way coupled Eulerian-Lagrangian approach is adopted to calculate the liquid-solid interaction. The reflection model proposed by Grant and Tabakoff and the erosion model proposed by the Erosion/Corrosion Research Center are combined to calculate the erosion rate and predict the erosion pattern. Results show that for the baseline case the inlet pipe is the least eroded component, whereas the impeller is the most eroded component. The highest average and maximum erosion rates occur at the hub of impeller. The most severe erosion region of a blade is the leading edge with a curvature angle that varies from 55° to 60°. The most severe erosion region of a volute is in the vicinity of a curvature angle of 270°. The impeller erosion pattern, especially the middle part of the hub and the vicinity of the blade pressure side, can be greatly influenced by operation parameters, such as flow rate, particle concentration, and particle size.
TOPICS: Flow (Dynamics), Particulate matter, Erosion, Centrifugal pumps, Impellers, Blades, Pressure, Pipes, Corrosion, Reflection, Particle size
Filipe Pereira, Luis Eca and Guilherme Vaz
J. Fluids Eng   doi: 10.1115/1.4043539
The importance of the turbulence closure to the modeling accuracy of the Partially-Averaged Navier-Stokes equations (PANS) is investigated in prediction of the flow around a circular cylinder at Reynolds number of 3900. A series of PANS calculations at various degrees of physical resolution is conducted using three Reynolds-Averaged Navier-Stokes equations (RANS) based closures: the standard, SST, and TNT k-w models. The latter is proposed in this work. The results illustrate the dependence of PANS on the closure. At coarse physical resolutions, a narrower range of scales is resolved so that the influence of the closure on the simulations accuracy increases significantly. Among all closures, PANS-TNT achieves the lowest comparison errors. The reduced sensitivity of this closure to freestream turbulence quantities and the absence of auxiliary functions from its governing equations are certainly contributing to this result. It is demonstrated that the use of partial turbulence quantities in such auxiliary functions calibrated for total turbulent (RANS) quantities affects their behavior. On the other hand, the successive increase of physical resolution reduces the relevance of the closure, causing the convergence of the three models towards the same solution. This outcome is achieved once the physical resolution and closure guarantee the precise replication of the spatial development of the key coherent structures of the flow.
TOPICS: Navier-Stokes equations, Turbulence, Resolution (Optics), Flow (Dynamics), Reynolds-averaged Navier–Stokes equations, Reynolds number, Simulation, Engineering simulation, Modeling, Performance, Circular cylinders, Errors

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