scholarly journals Numerical Investigation of Turbulence Models for a Superlaminar Journal Bearing

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Aoshuang Ding ◽  
Xiaodong Ren ◽  
Xuesong Li ◽  
Chunwei Gu
Keyword(s):  
Experimental Data ◽  
Buffer Layer ◽  
Journal Bearing ◽  
Profile Analysis ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Fully Developed Turbulence ◽  
Developed Turbulence ◽  
Sst Model ◽  
Oil Flow

With rotating machineries working at high speeds, oil flow in bearings becomes superlaminar. Under superlaminar conditions, flow exhibits between laminar and fully developed turbulence. In this study, superlaminar oil flow in an oil-lubricated tilting-pad journal bearing is analyzed through computational fluid dynamics (CFD). A three-dimensional bearing model is established. CFD results from the laminar model and 14 turbulence models are compared with experimental findings. The laminar simulation results of pad-side pressure are inconsistent with the experimental data. Thus, the turbulence effects on superlaminar flow should be considered. The simulated temperature and pressure distributions from the classical fully developed turbulence models cannot correctly fit the experimental data. As such, turbulence models should be corrected for superlaminar flow. However, several corrections, such as transition correction, are unsuitable. Among all the flow models, the SST model with low-Re correction exhibits the best pressure distribution and turbulence viscosity ratio. Velocity profile analysis confirms that a buffer layer plays an important role in the superlaminar boundary layer. Classical fully developed turbulence models cannot accurately predict the buffer layer, but this problem can be resolved by initiating an appropriate low-Re correction. Therefore, the SST model with low-Re correction yields suitable results for superlaminar flows in bearings.

Validation of Turbulence Models for the Superlaminar Flows in Journal Bearings

2017 ◽  
Author(s):  
Aoshuang Ding ◽  
Xiaodong Ren
Keyword(s):  
Buffer Layer ◽  
Turbulence Models ◽  
Journal Bearings ◽  
Wall Turbulence ◽  
Fully Developed Turbulence ◽  
Developed Turbulence ◽  
Sst Model ◽  
Oil Flow ◽  
Near Wall Turbulence ◽  
Near Wall

With the development of high speed rotating machinery, the flow regime in bearings changes from laminar to superlaminar, that is, the flow is between laminar and fully developed turbulent. The superlaminar oil flow in an oil–lubricated tilting–pad journal bearing is analyzed in this study. A three–dimensional model for the oil domain is established and the CFD results obtained using laminar and seventeen turbulence models are compared with the experimental results obtained by S.Taniguchi. The seventeen turbulence models are divided into three groups, namely, classical fully developed turbulence models, transition turbulence models, and turbulence models with low–Re correction. The laminar and classical turbulence models cannot simulate the superlaminar flow correctly; accordingly, corrections should be applied to classical fully developed turbulence models for superlaminar flows to consider the turbulent effect properly. However, not all corrections are suitable. Among all the compared turbulence models, the SST model with low–Re correction performs the best. Furthermore, this model can capture the turbulent effect in superlaminar oil flow, as indicated in the analysis of turbulent viscosity ratio. A comparison of the velocity profiles shows that the mechanism of the superlaminar flow in journal bearings is near–wall turbulence. The buffer layer plays an important role in superlaminar flows. The SST model with low–Re correction can likewise capture the characteristics of the buffer layer and simulate the near–wall turbulence properly in superlaminar flows. Thus in superlaminar journal bearings, the low–Re correction is the most suitable correction for the SST turbulence model for simulating oil flows.

scholarly journals Impact of Turbulence Models on the Air Flow in a Confined Rectangular Space

2020 ◽  
pp. 46-53
Author(s):  
Jakub Mularski ◽  
Amit Arora ◽  
Muhammad Azam Saeed ◽  
Łukasz Niedźwiecki ◽  
Samrand Saeidi
Keyword(s):  
Experimental Data ◽  
Air Flow ◽  
Turbulence Models ◽  
The Other ◽  
Experimental Measurements ◽  
Wall Region ◽  
Sst Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
The Given

The paper regards the impact of four different turbulence models on the air flow pattern in a confined rectangular space. The following approaches are analyzed. The Baseline (BSL) Reynolds model, the Speziale-Sarkar-Gatzki (SSG) Reynolds model, the Menter's shear-stress transport (SST) model and the basic k-ε model. Computational fluid dynamics (CFD) results are compared with the experimental measurements in four different planes. The Reynolds number for the given conditions is equal to 5000. The k-ε model yielded the most accurate results with regard to the experimental data but its reliability decreased near the wall region. With respect to the other models, it was also found that the k-ε approach generated the least circulating flow.

CFD analysis of the effect of nozzle stand-off distance on turbulent impinging jets

2013 ◽  
Vol 40 (7) ◽  
pp. 603-612 ◽  
Author(s):  
Mehrdad Shademan ◽  
Ram Balachandar ◽  
Ronald M. Barron
Keyword(s):  
Experimental Data ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Axial Direction ◽  
Reynolds Stress Model ◽  
Impinging Jets ◽  
Diameter Ratio ◽  
Wall Region ◽  
Nozzle Height ◽  
Jet Characteristics

Three-dimensional steady Reynolds Averaged Navier-Stokes simulations have been carried out to investigate the effect of the nozzle stand-off distance on the mean and turbulence characteristics of jets impinging vertically on flat surfaces. As part of the study, the performance of different turbulence models such as Realizable k–ε, k–ω SST, and Reynolds Stress Model (RSM) were evaluated. Based on comparisons with experimental data, RSM was chosen to further evaluate the characteristics of impinging jets. The Reynolds number based on the jet exit velocity and nozzle diameter is 100 000. Three different nozzle height-to-diameter ratios, representing different types of impinging jets, were simulated and compared with available experimental data. A strong dependency of the jet characteristics on the nozzle height-to-diameter ratio was observed. The simulations show that an increase in this ratio results in larger shear stress and more distributed pressure on the wall, more development of the flow in the axial direction and faster progress of the jet in the wall region. The current simulations present a robust step-by-step computational fluid dynamics approach to investigate the role of the nozzle height-to-diameter ratio on the impinging jet flow parameters.

scholarly journals Particle trapping in three-dimensional fully developed turbulence

2005 ◽  
Vol 17 (2) ◽  
pp. 021701 ◽  
Author(s):  
L. Biferale ◽  
G. Boffetta ◽  
A. Celani ◽  
A. Lanotte ◽  
F. Toschi
Keyword(s):  
Three Dimensional ◽  
Particle Trapping ◽  
Fully Developed Turbulence ◽  
Developed Turbulence

Improvement and Analysis for a Gaseous Cavitation Model Applied in a Tilting-Pad Journal Bearing

2019 ◽  
Author(s):  
Aoshuang Ding ◽  
Xuesong Li ◽  
Yuhong Li
Keyword(s):  
Journal Bearing ◽  
Three Dimensional ◽  
Cavitation Model ◽  
Local Pressure ◽  
Cavitation Process ◽  
Air Volume ◽  
Tilting Pad ◽  
Sst Model ◽  
Tilting Pad Journal Bearing ◽  
Good Agreement

Abstract Considering the gaseous cavitation rate is influenced by local pressure, a transient gaseous cavitation model is developed from an equilibrium gaseous cavitation model in consideration of transient gaseous cavitation theories and the Bunsen solubility. With the shear stress transport (SST) model with low-Re correction and air backflow from the bearing outlets, the transient gaseous cavitation model is applied to the three-dimensional simulations of an entire tilting-pad journal bearing at 3000 rpm speed and under 180 kN load. The simulated bearing pressure and load are in good agreement with the experimental data, indicating that the transient gaseous cavitation model performs well in the bearing simulations. Based on the comparisons of the simulated air and dissolved air distributions between the transient and equilibrium gaseous cavitation models, the simulated cavitation process of the transient gaseous cavitation is proved to be not in equilibrium and mass transfer occur between the backflow air and oil. The purpose of building the transient gaseous cavitation model is thus met. Analyses of the air distributions indicate that high cavitation rates and low dissolution rates makes air volume a major part of the total air volume and close to the physical gaseous cavitation process.

Effects of Different Turbulence Models on Three-Dimensional Unsteady Cavitating Flows in the Centrifugal Pump and Performance Prediction

2019 ◽  
Vol 20 (3-4) ◽  
pp. 487-509 ◽  
Author(s):  
Ahmed Ramadhan Al-Obaidi
Keyword(s):  
Centrifugal Pump ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Experimental Results ◽  
Centrifugal Pumps ◽  
Operation Condition ◽  
Sst Model ◽  
And Performance ◽  
Turbulent Models

AbstractIn centrifugal pumps, it is important to select appropriate turbulence model for the numerical simulation in order to obtain reliable and accurate results. In this work, ten turbulence models in 3-D transient simulation for the centrifugal pump are chosen and compared. The pump performance is validated with experimental results. The numerical results reveal that the SST turbulence model was closer to the experimental results in predicting head. In addition, the pressure variation trend for the ten models is very similar which increases and then decreases from the inlet to outlet of the pump along the streamline. The SST k-ω model predicts the performance of the pump was more accurately than other turbulent models. Furthermore, the results also found that the error is the least at design operation condition 300(l/min), which is around 1.98 % for the SST model and 2.14 % and 2.38 % for the LES and transition omega model. Within 7.61 %, the errors at higher flow rate 350(l/min) for SST. The error for SST model is smaller as compared to different turbulent models. For the Realizable k-ɛ model, the errors fluctuate were more high than other models.

Aerodynamic Comparison and Validation of RANS, URANS and SAS Simulations of Flat Plate Film-Cooling

2010 ◽  
Author(s):  
Stefan Voigt ◽  
Berthold Noll ◽  
Manfred Aigner
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Film Cooling ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
3 Dimensional ◽  
Commercial Code ◽  
Sst Model ◽  
Rans Models

The present paper deals with the detailed numerical simulation of film cooling including conjugate heat transfer. Five different turbulence models are used to simulate a film cooling configuration. The models include three steady and two unsteady models. The steady RANS models are the Shear stress transport (SST) model of Menter, the Reynolds stress model of Speziale, Sarkar and Gatski and a k-ε explicit algebraic Reynolds stress model. The unsteady models are a URANS formulation of the SST model and a scale-adaptive simulation (SAS). The solver used in this study is the commercial code ANSYS CFX 11.0. The results are compared to available experimental data. These data include velocity and turbulence intensity fields in several planes. It is shown that the steady RANS approach has difficulties with predicting the flow field due to the high 3-dimensional unsteadiness. The URANS and SAS simulations on the other hand show good agreement with the experimental data. The deviation from the experimental data in velocity values in the steady cases is about 20% whereas the error in the unsteady cases is below 10%.

A Comparison of Some Recent Eddy-Viscosity Turbulence Models

1996 ◽  
Vol 118 (3) ◽  
pp. 514-519 ◽  
Author(s):  
F. R. Menter
Keyword(s):  
Experimental Data ◽  
Finite Difference ◽  
Pressure Gradient ◽  
Eddy Viscosity ◽  
State Of The Art ◽  
Turbulence Models ◽  
Adverse Pressure Gradient ◽  
Gradient Flows ◽  
Grid Convergence ◽  
Sst Model

The performance of recently developed eddy-viscosity turbulence models, including the author’s SST model, is evaluated against a number of attached and separated adverse pressure gradient flows. The results are compared in detail against experimental data, as well as against the standard k-ε model. Grid convergence was established for all computations. The study involves four different, state-of-the-art finite difference (finite volume) codes.

Study of Turbulence Models in Flows Through Adverse Pressure Gradient System

2005 ◽  
Author(s):  
E. Karunakaran ◽  
V. Ganesan
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Pressure Gradient ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Adverse Pressure Gradient ◽  
Reynolds Stress Model ◽  
Gradient System ◽  
Field Development

This paper is concerned with the study of performance of popular turbulence models used in the CFD analysis. Turbulence models considered for evaluation include the eddy viscosity models and the Reynolds stress model. The recent k-ε-v2-f model recommended for a flow with separation is also studied. Evaluation of the turbulence models in the present study focuses on a three-dimensional flow field development with adverse pressure gradient and flows that simulate wall-bounded turbulence. Numerical calculations are performed using SIMPLE based algorithm. Nowadays, decelerating flow in a diffuser is assessed by numerical simulations and the validation is done with experimental results. A comparison of the numerical results and the experimental data are presented. The main objective of the comparison is to obtain information on how well the numerical simulations representing the flow field with the standard turbulence models, are able to reproduce the experimental data.

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