Prediction of Pressure Fluctuation on a Vehicle by Large Eddy Simulation

The objective of this study is to predict accurately interior aeroacoustics noise of a car for a wide range of frequency between 100 Hz and 4 kHz. One-way coupled simulations of computational fluid dynamics (CFD), structural analysis and acoustical analysis were performed to predict interior aeroacoustics noise. We predicted pressure fluctuations on the outer surfaces of a test car by computing unsteady flow around the car as the first step. Secondary, the predicted pressure fluctuations were fed to the subsequent structural analysis to predict vibration accelerations on the inner surfaces of the test car. Finally, acoustical analysis was performed to predict sound fields in the test car by giving vibration accelerations computed by the structural analysis as the boundary conditions. In this paper, we focus on the unsteady flow computations, which is the first step of the coupled simulations. Large Eddy Simulation (LES) was performed to predict the pressure fluctuations on the outer surfaces of the test car. We used the computational mesh composed of approximately 5 billion hexahedral grids with a spatial resolution of 1.5 mm in the streamwise and spanwise directions to resolve the dynamics of the small vortices in the turbulence boundary layer. Predicted and measured pressure fluctuation at several sampling points on the surface of the test car were compared and they matched well in a wide range of frequency up to 2 kHz.

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Large Eddy Simulation of Unsteady Flow in a Mixed Flow Pump Guide Vane

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.444-445.555 ◽

2013 ◽

Vol 444-445 ◽

pp. 555-560 ◽

Cited By ~ 1

Author(s):

Yi Bin Li ◽

Ren Nian Li ◽

Xiu Yong Wang

Keyword(s):

Large Eddy Simulation ◽

Unsteady Flow ◽

Pressure Fluctuation ◽

Guide Vane ◽

Suction Surface ◽

Mixed Flow ◽

Eddy Simulation ◽

Large Eddy ◽

Small Flow ◽

Flow Pump

In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluids rotation is the same to impeller in the guide vane adhere.

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Numerical Simulation of Unsteady Flow and Flow Induced Sound of Airfoil and Wing/Plate Junction by LES and FW-H Acoustic Analogy

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.444-445.479 ◽

2013 ◽

Vol 444-445 ◽

pp. 479-485

Author(s):

Nan Zhang ◽

Shi Jin Lv ◽

Hua Xie ◽

Sheng Li Zhang

Keyword(s):

Numerical Simulation ◽

Large Eddy Simulation ◽

Unsteady Flow ◽

Pressure Fluctuations ◽

Water Channel ◽

Wall Pressure ◽

Acoustic Analogy ◽

Eddy Simulation ◽

Wall Pressure Fluctuations ◽

Large Eddy

Numerical simulation of unsteady flow and flow-induced sound of an airfoil and a wing/plate junction are performed in the paper by large eddy simulation (LES) and FW-H acoustic analogy. The vortical flows around a NACA0015 airfoil at two angles of attack (0°and 8°) are simulated and analyzed by vortex identification. Simultaneously, the wall pressure fluctuations of the airfoil are computed. At two angles of attack, the flow induced sound of the airfoil is predicted. The computed power spectra agree well with experimental measurements. So the capability of large eddy simulation in predicting unsteady flow and flow induced sound is validated. Subsequently, the horse-shoe vortex around a wing/plate junction in water is computed. Furthermore, the calculations of wall pressure fluctuations and flow induced sound of the junction model at three velocities are accomplished. The predicted results are compared favorably with measured data in large circulation water channel. So the numerical approach for flow induced sound of wing/plate junction in water is validated. It shows that the numerical simulation method in the paper is credible.

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Large Eddy Simulation of Periodic Transient Pressure Fluctuation in a Centrifugal Pump Impeller at Low Flow Rate

Symmetry ◽

10.3390/sym13020311 ◽

2021 ◽

Vol 13 (2) ◽

pp. 311

Author(s):

Renfei Kuang ◽

Xiaoping Chen ◽

Zhiming Zhang ◽

Zuchao Zhu ◽

Yu Li

Keyword(s):

Large Eddy Simulation ◽

Centrifugal Pump ◽

Flow Rate ◽

Pressure Fluctuation ◽

Low Frequency ◽

Pump Impeller ◽

Eddy Simulation ◽

Inlet Flow Rate ◽

Large Eddy ◽

Centrifugal Pump Impeller

This paper presents a large eddy simulation of a centrifugal pump impeller during a transient condition. The flow rate is sinusoidal and oscillates between 0.25Qd (Qd indicates design load) and 0.75Qd when the rotating speed is maintained. Research shows that in one period, the inlet flow rate will twice reach 0.5Qd, and among the impeller of one moment is a stall state, but the other is a non-stall state. In the process of flow development, the evolution of low-frequency pressure fluctuation shows an obviously sinusoidal form, whose frequency is insensitive to the monitoring position and equals to that of the flow rate. However, inside the impeller, the phase and amplitude in the stall passages lag behind more and are stronger than that in the non-stall passages. Meanwhile, the strongest region of the high-frequency pressure fluctuation appears in the stall passages at the transient rising stage. The second dominant frequency in stall passages is 2.5 times to that in non-stall passages. In addition, similar to the pressure fluctuation, the evolution of the low-frequency head shows a sinusoidal form, whose phase is lagging behind that by one-third of a period in the inlet flow rate.

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Large Eddy Simulation of Laminar and Turbulent Shock/Boundary Layer Interactions in a Transonic Passage

Volume 2A: Turbomachinery ◽

10.1115/gt2020-14244 ◽

2020 ◽

Author(s):

Stephan Priebe ◽

Daniel Wilkin ◽

Andy Breeze-Stringfellow ◽

Giridhar Jothiprasad ◽

Lawrence C. Cheung

Keyword(s):

Boundary Layer ◽

Large Eddy Simulation ◽

Low Frequency ◽

Boundary Layer Separation ◽

Eddy Simulation ◽

Turbulent Inflow ◽

Wide Range ◽

Large Eddy ◽

Constant Radius ◽

Structure Boundary

Abstract Shock/boundary layer interactions (SBLI) are a fundamental fluid mechanics problem relevant in a wide range of applications including transonic rotors in turbomachinery. This paper uses wall-resolved large eddy simulation (LES) to examine the interaction of normal shocks with laminar and turbulent inflow boundary layers in transonic flow. The calculations were performed using GENESIS, a high-order, unstructured LES solver. The geometry created for this study is a transonic passage with a convergent-divergent nozzle that expands the flow to the desired Mach number upstream of the shock and then introduces constant radius curvature to simulate local airfoil camber. The Mach numbers in the divergent section of the transonic passage simulate single stage commercial fan blades. The results predicted with the LES calculations show significant differences between laminar and turbulent SBLI in terms of shock structure, boundary layer separation and transition, and aerodynamic losses. For laminar flow into the shock, significant flow separation and low-frequency unsteadiness occur, while for turbulent flow into the shock, both the boundary layer loss and the low-frequency unsteadiness are reduced.

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Large-Eddy Simulation of Unsteady Surface Pressure Over a LP Turbine Blade Due to Interactions of Passing Wakes and Inflexional Boundary Layer

Volume 6: Turbo Expo 2005, Parts A and B ◽

10.1115/gt2005-68867 ◽

2005 ◽

Cited By ~ 1

Author(s):

S. Sarkar ◽

Peter R. Voke

Keyword(s):

Large Eddy Simulation ◽

Turbine Blade ◽

Coherent Structures ◽

Pressure Fluctuations ◽

Time Dependent ◽

Suction Surface ◽

Eddy Simulation ◽

Large Eddy ◽

Grid Points ◽

Lp Turbine

The unsteady pressure over the suction surface of a modern low-pressure (LP) turbine blade subjected to periodically passing wakes from a moving bar wake generator is described. The results presented are a part of detailed Large-Eddy Simulation (LES) following earlier experiments over the T106 profile for a Reynolds number of 1.6×105 (based on the chord and exit velocity) and the cascade pitch to chord ratio of 0.8. The present LES uses coupled simulations of cylinder for wake, providing four-dimensional inflow conditions for successor simulations of wake interactions with the blade. The three-dimensional, time-dependent, incompressible Navier-Stokes equations in fully covariant form are solved with 2.4×106 grid points for the cascade and 3.05×106 grid points for the cylinder using a symmetry-preserving finite difference scheme of second-order spatial and temporal accuracy. A separation bubble on the suction surface of the blade was found to form under the steady state condition. Pressure fluctuations of large amplitude appear on the suction surface as the wake passes over the separation region. Enhanced receptivity of perturbations associated with the inflexional velocity profile is the cause of instability and coherent vortices appear over the rear half of the suction surface by the rollup of shear layer via Kelvin-Helmholtz (K-H) mechanism. Once these vortices are formed, the steady-flow separation changes remarkably. These coherent structures embedded in the boundary amplify before breakdown while traveling downstream with a convective speed of about 37 percent of the local free-stream speed. The vortices play an important role in the generation of turbulence and thus to decide the transitional length, which becomes time-dependent. The source of the pressure fluctuations on the rear part of the suction surface is also identified as the formation of these coherent structures. When compared with experiments, it reveals that LES is worth pursuing as an understanding of the eddy motions and interactions is of vital importance for the problem.

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High-resolution atmospheric boundary layer simulations using WRF-LES

10.5194/egusphere-egu2020-21760 ◽

2020 ◽

Author(s):

Gokhan Kirkil

Keyword(s):

Boundary Layer ◽

Large Eddy Simulation ◽

Cross Sections ◽

Wrf Model ◽

Field Measurements ◽

Mean Flow ◽

Spatial And Temporal Scales ◽

Eddy Simulation ◽

Wide Range ◽

Large Eddy

WRF model provides a potentially powerful framework for coupled simulations of flow covering a wide range of spatial and temporal scales via a successive grid nesting capability. Nesting can be repeated down to turbulence solving large eddy simulation (LES) scales, providing a means for significant improvements of simulation of turbulent atmospheric boundary layers. We will present the recent progress on our WRF-LES simulations of the Perdigao Experiment performed over mountainous terrain. We performed multi-scale simulations using WRF&#8217;s different Planetary Boundary Layer (PBL) parameterizations as well as Large Eddy Simulation (LES) and compared the results with the detailed field measurements. WRF-LES model improved the mean flow field as well as second-order flow statistics. Mean fluctuations and turbulent kinetic energy fields from WRF-LES solution are investigated in several cross-sections around the hill which shows good agreement with measurements.

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