Investigation of Aerator Flow Pressure Fluctuation Using Detached Eddy Simulation with VOF Method

The unsteady flow field and pressure fluctuations in double-suction centrifugal pumps are greatly affected by the wall roughness of internal surfaces. To determine the wall roughness effect, numerical and experimental investigations were carried out. Three impeller schemes for different wall roughness were solved using detached eddy simulation, and the performance and pressure fluctuations resolved by detached eddy simulation were compared with the experimental data. The results show that the effects of wall roughness on the static performance of a pump are remarkable. The head and efficiency of the tested double-suction centrifugal pump are raised by 2.53% and 6.60% respectively as the wall roughness is reduced by means of sand blasting and coating treatments. The detached eddy simulation method has been proven to be accurate for the prediction of the head and efficiency of the double-suction centrifugal pump with roughness effects. The influence of the roughness on pressure fluctuation is greatly dependent on the location relative to the volute tongue region. For locations close to the volute tongue, the peak-to-peak value of the pressure fluctuations of a wall roughness of Ra = 0.10 mm may be 23.27% larger than the case where Ra = 0.02 mm at design flow rate.

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POD and Extended-POD Analysis of Pressure Fluctuations and Vortex Structures Inside a Steam Turbine Control Valve

Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines ◽

10.1115/gt2018-75312 ◽

2018 ◽

Author(s):

Peng Wang ◽

Hongyu Ma ◽

Yingzheng Liu

Keyword(s):

Steam Turbine ◽

Pressure Fluctuation ◽

Pressure Field ◽

Pressure Fluctuations ◽

Turbulence Models ◽

Control Valve ◽

Vortex Structures ◽

Detached Eddy Simulation ◽

Eddy Simulation ◽

Pod Analysis

In steam turbine control valves, pressure fluctuations coupled with vortex structures in highly unsteady three-dimensional flows make essential contributions to aerodynamic forcing on the valve components, and are major sources of flow-induced vibration and acoustic effects. Advanced turbulence models, such as scale adaptive simulation (SAS), detached eddy simulation (DES) and large eddy simulation (LES), can capture detailed flow information of the control valve, but it is challenging to identify the primary flow structures due to the massive flow database. The present study used state-of-the-art data-driven analysis, namely proper orthogonal decomposition (POD) and extended-POD, to extract the energetic pressure fluctuations and dominant vortex structures of the control valve. To this end, the typical annular attachment flow inside a steam turbine control valve was investigated by performing a DES study. Subsequently, the energetic pressure fluctuation modes were extracted by performing POD analysis on the valve’s pressure field. The vortex structures contributing to these energetic pressure fluctuation modes were extracted by performing extended-POD analysis on the pressure-velocity coupling field. Finally, the dominant vortex structures were revealed directly by POD analysis of the valve’s velocity field. The results demonstrated that the flow instabilities inside the control valve were mainly induced by oscillations of the annular wall-attached jet and the derivative flow separations and reattachments. In POD analysis of the pressure field, the axial, antisymmetric and asymmetric pressure modes occupied most of the pressure fluctuation intensity. By further conducting extended-POD analysis, the vortex structures’ incorporation with the energetic pressure modes was identified as mainly attributed to the synchronous, alternating and single-sided oscillation behaviors of the annular attachment flow. However, based on POD analysis of the unsteady velocity fields, the vortex structures, buried in the dominant modes at St = 0.017, were found to result from alternating oscillations of the annular wall-attached jet.

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Research and Application of Filtering Grid Scale in Detached Eddy Simulation Model

Symmetry ◽

10.3390/sym12081252 ◽

2020 ◽

Vol 12 (8) ◽

pp. 1252

Author(s):

Liang Dong ◽

Chao Guo ◽

Ying Wang ◽

Houlin Liu ◽

Cui Dai

Keyword(s):

Geometric Mean ◽

Pressure Coefficient ◽

Polar Angle ◽

Internal Flow ◽

Experimental Result ◽

Detached Eddy Simulation ◽

Quadratic Mean ◽

Eddy Simulation ◽

Large Eddy ◽

Flow Pressure

The existing definition method of filter grid scale in a Detached Eddy Simulation (DES) hybrid model is unreasonable, which will lead to the unreasonable trigger of a boundary layer large eddy simulation and reduce computational efficiency. In view of this problem, the filter grid scale is discussed in this paper. The 90° square curved elbow is selected as the research object. The effects of three grid definition methods: geometric mean (ΔGM), arithmetic mean (ΔAM) and quadratic mean (ΔQM) on the simulation results of the DES model are compared, and the velocity distribution of the flow cross section and the distribution of the flow pressure coefficient on the outer arc surface are compared with the experimental results of Taylor. The results show that the order of the three definition methods is ΔGM≤ΔAM≤ΔQM. Meanwhile, within 30° < polar angle(θ) < 75°, the results are closer to the experiment, and the development trends and numerical values of ΔAM and ΔQM are closer to the experiment in general. However, when θ > 60°, the value of ΔQM is slightly closer to the experimental result than ΔAM. ΔQM is more suitable for calculating the internal flow in a curved elbow than the other two methods.

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Detached eddy simulation of unsteady cavitation and pressure fluctuation around 3-D NACA66 hydrofoil

Thermal Science ◽

10.2298/tsci1504231z ◽

2015 ◽

Vol 19 (4) ◽

pp. 1231-1234 ◽

Cited By ~ 1

Author(s):

De-Sheng Zhang ◽

Hai-Yu Wang ◽

Lin-Lin Geng ◽

Wei-Dong Shi

Keyword(s):

Turbulence Model ◽

Pressure Fluctuation ◽

Cavitating Flow ◽

Numerical Results ◽

Detached Eddy Simulation ◽

Cavitation Model ◽

Cloud Cavitation ◽

Sheet Cavitation ◽

Eddy Simulation ◽

Unsteady Cavitating Flow

The unsteady cavitating flow and pressure fluctuation around the 3-D NACA66 hydrofoil were simulated and validated based on detached eddy simulation turbulence model and a homogeneous cavitation model. Numerical results show that detached eddy simulation can predict the evolution of cavity inception, sheet cavitation growth, cloud cavitation shedding, and breakup, as well as the pressure fluctuation on the surface of hydrofoil. The sheet cavitation growth, detachment, cloud cavitation shedding are responsible for the features of the pressure fluctuation.

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Numerical Study of the Unsteady Flow Inside a Centrifugal Fan and its Downstream Pipe Using Detached Eddy Simulation

Volume 10: Fluids Engineering ◽

10.1115/imece2020-24544 ◽

2020 ◽

Author(s):

Jian-Cheng Cai ◽

Jia-Qi Zhang ◽

Can Yang

Keyword(s):

Unsteady Flow ◽

Pressure Fluctuation ◽

Pressure Fluctuations ◽

Computational Domain ◽

Centrifugal Fan ◽

Detached Eddy Simulation ◽

Impeller Blade ◽

Eddy Simulation ◽

Maximum Value ◽

Outlet Pipe

Abstract The 3-D unsteady turbulent flow inside a centrifugal fan and its downstream pipe is investigated at the best efficiency point (BEP) flow rate using the computational fluid dynamics (CFD) package ANSYS FLUENT. The impeller with an outlet diameter of 400 mm has 12 forward curved blades. The computational domain comprises four parts: the inlet part, the impeller, the volute, and the downstream pipe. The flow domain was meshed in ANSYS ICEM-CFD with structured hexahedron cells, and nearly 9 million cells were used. The Detached Eddy Simulation (DES) turbulence modelling approach was employed with this fine enough mesh scheme. The impeller was set as the rotating domain at a speed of 2900 rpm. A sliding mesh technique was applied to the interfaces in order to allow unsteady interactions between the rotating impeller and the stationary parts; the unsteady interactions generate pressure fluctuations inside the centrifugal fan. One impeller revolution is divided into 2048 time steps, in order to capture the transient flow phenomena with high resolution. Monitoring points were set along the volute casing profile, and along the downstream pipe centerline. When the numerical simulation became stable after several impeller revolutions, the statistics of the unsteady flow was initiated with a total of 16384 time steps (8 impeller revolutions) data. The time history data of the pressure and velocity magnitude at the monitoring points were saved and with Fourier transform applied to obtain the frequency spectra. The time-averaged flow fields show clearly the static pressure rises gradually through the impeller, and further recovers from the velocity in the volute, and decreases gradually along the downstream pipe due to the friction. The mean pressure at the pressure side of the impeller blade is larger than it at the suction side, forming the circumferential nonuniform flow pattern. Owing to the forward-curved blades, large velocity region exists around the impellor exit, and the maximum velocity near the trailing edge can reach 1.5u2, where u2 is the circumferential velocity at the impeller outlet. The root mean square (rms) value distribution of pressure fluctuations show that most parts inside the centrifugal fan undergo large pressure fluctuation with the magnitude about 10% of the reference dynamic pressure pref = 0.5ρu22; the maximum value locating at the tongue tip can reach 30% of pref. The pressure fluctuation magnitude decreases quickly along the outlet pipe: after 5D (D is the outlet pipe diameter) the magnitude is 0.5% of pref. The pressure and velocity fluctuation spectra at the monitoring points in the volute show striking discrete components at the blade-passing frequency (BPF) and its 2nd, 3rd harmonics. The BPF component has the maximum value of 15% of pref in the tongue region, and it decreases dramatically along the downstream pipe with the amplitude less than 0.2% of pref after 5D distance.

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Wind noise source characterization and transmission study through a side glass of DrivAer model based on a hybrid DES/APE method

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407020969551 ◽

2020 ◽

pp. 095440702096955

Author(s):

Yinzhi He ◽

Siyi Wen ◽

Yongming Liu ◽

Zhigang Yang

Keyword(s):

Pressure Fluctuation ◽

Acoustic Pressure ◽

Pressure Fluctuations ◽

Transmission Efficiency ◽

Interior Noise ◽

Perturbation Equation ◽

Detached Eddy Simulation ◽

Source Characterization ◽

Side Window ◽

Eddy Simulation

Based on a DrivAer model with notchback, the characteristics of convective and acoustic pressure fluctuations on the side window, as well as their contributions to interior noise were studied. Firstly, a full-size DrivAer clay model was produced with a real glass set on the front left window, and the rest parts with thick clay. In this way, the side glass becomes the exclusive transmission path for the exterior convective and acoustic pressures into acoustic cabin inside. In this study, the acoustic pressure fluctuation on the side window surface was calculated by solving the acoustic perturbation equation (APE) based on the calculation results of convective pressure fluctuation with the incompressible Detached Eddy Simulation (DES). Furthermore, with the convective and acoustic pressure fluctuations as power inputs, the interior noise was calculated with Statistical Energy Analysis (SEA). The calculated interior noise level shows good agreement with the tested results in the wind tunnel, which indirectly validates the reliability of the calculated acoustic pressures with APE method. The contributions of the convective and acoustic pressure fluctuations to the interior noise show that the acoustic pressure fluctuation takes much higher transmission efficiency than the convective one, especially at the high frequency range above the coincidence frequency of the glass, the contribution of acoustic pressure fluctuation is absolutely dominant.

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