scholarly journals Computational Investigation of Flows in Diffusing S-shaped Intakes

10.14311/262 ◽  
2001 ◽  
Vol 41 (4-5) ◽  
Author(s):  
R. Menzies
Keyword(s):  
Unsteady Flow ◽  
Turbulence Model ◽  
Mass Flow ◽  
Turbulence Models ◽  
High Mass ◽  
Complex Flow ◽  
Choked Flow ◽  
Sst Turbulence Model ◽  
Low Mass ◽  
Flow Case

This paper examines the flow in a diffusing s-shaped aircraft air intake using computational fluid dynamics (CFD) simulations. Diffusing s-shaped ducts such as the RAE intake model 2129 (M2129) give rise to complex flow patterns that develop as a result of the offset between the intake cowl plane and engine face plane. Euler results compare favourably with experiment and previous calculations for a low mass flow case. For a high mass flow case a converged steady solution was not found and the problem was then simulated using an unsteady flow solver. A choked flow at the intake throat and complex shock reflection system, together with a highly unsteady flow downstream of the first bend, yielded results that did not compare well with previous experimental data. Previous work had also experienced this problem and a modification to the geometry to account for flow separation was required to obtain a steady flow.RANS results utilising a selection of turbulence models were more satisfactory. The low mass flow case showed good comparison with experiment and previous calculations. A problem of the low mass flow case is the prediction of secondary flow. It was found that the SST turbulence model best predicted this feature. Fully converged high mass flow results were obtained. Once more, SST results proved to match experiment and previous computations the best. Problems with the prediction of the flow in the cowl region of the duct were experienced with the S-A and k-w models. One of the main problems of turbulence closures in intake flows is the transition of the freestream from laminar to turbulent over the intake cowl region. It is likely that the improvement in this prediction using the SST turbulence model will lead to more satisfactory results for both high and low mass flow rates.

scholarly journals Simulation and Modeling of Flow in a Gas Compressor

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Anna Avramenko ◽  
Alexey Frolov ◽  
Jari Hämäläinen
Keyword(s):  
Steady State ◽  
Mass Flow ◽  
Gas Flow ◽  
Simulation Method ◽  
High Mass ◽  
Ansys Fluent ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Flow Through

The presented research demonstrates the results of a series of numerical simulations of gas flow through a single-stage centrifugal compressor with a vaneless diffuser. Numerical results were validated with experiments consisting of eight regimes with different mass flow rates. The steady-state and unsteady simulations were done in ANSYS FLUENT 13.0 and NUMECA FINE/TURBO 8.9.1 for one-period geometry due to periodicity of the problem. First-order discretization is insufficient due to strong dissipation effects. Results obtained with second-order discretization agree with the experiments for the steady-state case in the region of high mass flow rates. In the area of low mass flow rates, nonstationary effects significantly influence the flow leading stationary model to poor prediction. Therefore, the unsteady simulations were performed in the region of low mass flow rates. Results of calculation were compared with experimental data. The numerical simulation method in this paper can be used to predict compressor performance.

Computational Fluid Dynamics Performance Estimation of Turbo Booster Vacuum Pump

2003 ◽  
Vol 125 (3) ◽  
pp. 586-589 ◽  
Author(s):  
H.-P. Cheng ◽  
C.-J. Chen , ◽  
P.-W. Cheng ,
Keyword(s):  
Fluid Dynamics ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Vacuum Pump ◽  
Performance Estimation ◽  
High Mass ◽  
Rotor Speed ◽  
Low Mass ◽  
Pump Inlet

The CFD performance estimation of turbo booster vacuum pump shows the axial vortex and back flow is evident when the mass flow rate is increased. The pressure is increased from the pump inlet to the outlet for the low mass flow rate cases. But for high mass flow rate cases, the pressure is increased until the region near the end of the rotor then decreased. The calculated inlet pressure, compression ratio, and pumping speed is increased, decreased, and decreased, respectively, when the mass flow rate is increased. The pumping speed is increased when the rotor speed is increased.

Numerical Simulation Analysis of Car Overtaking on SST Turbulence Model

2014 ◽  
Vol 628 ◽  
pp. 270-274
Author(s):  
Yi Bin He ◽  
Qi Zhi Shen
Keyword(s):  
Numerical Simulation ◽  
Numerical Experiment ◽  
Drag Coefficient ◽  
Turbulence Model ◽  
Simulation Analysis ◽  
Turbulence Models ◽  
Force Coefficient ◽  
Side Force ◽  
Sst Turbulence Model ◽  
Side Force Coefficient

Thebased SST (shear strain transport) turbulence model combines the advantages of and turbulence models and performs well in numerical experiment. In the paper, the SST turbulence model is applied to model vehicle overtaking process with numerical simulation technology. The change graph of drag coefficient and side force coefficient are gained. Analysis of the phenomena is presented at the end.

Prediction of Unsteady Flow around a Square Cylinder Using RANS

2011 ◽  
Vol 52-54 ◽  
pp. 1165-1170
Author(s):  
Fu You Xu ◽  
Xu Yong Ying ◽  
Zhe Zhang
Keyword(s):  
Standard Model ◽  
Unsteady Flow ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Surface Flow ◽  
Two Dimensional ◽  
Square Cylinder ◽  
Complex Flow ◽  
Near Surface ◽  
Sst Model

The results of unsteady Reynolds averaged Navier-Stokes (URANS) simulations of flow around a square cylinder using two-dimensional hybrid meshes were presented in this paper. The first part examined the accuracy of various RANS turbulence models, i.e. the standard model, RNG model, realizable model, standard model, SST model, and RSM, by comparing their results with available experimental data. Despite the limits imposed by the RANS approach and the relatively inexpensive two-dimensional computations, the main features of this complex flow can be predicted reasonably well. Among the computations using various RANS models compared here, the SST model shows the best agreement with the experiment. The second part investigated the effects of corner cutoffs on unsteady flow characteristics around a square cylinder by using the SST model. Especially the detailed near-surface flow structure around the cylinder was focused on, aiming at giving an explanation for the drastic modification of the aerodynamic characteristics as the corner shape is slightly changed.

Development of a Numerical Based Correlation for Performance Losses due to Surface Roughness in Axial Turbines

2014 ◽  
Vol 30 (6) ◽  
pp. 631-642 ◽  
Author(s):  
S. A. Moshizi ◽  
M. H. Nakhaei ◽  
M. J. Kermani ◽  
A. Madadi
Keyword(s):  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Streamline Curvature ◽  
Sst Turbulence Model ◽  
Stator Blade ◽  
Dimensional Models ◽  
Three Dimensional Models ◽  
Axial Turbines

AbstractIn the present work, a recently developed in-house 2D CFD code is used to study the effect of gas turbine stator blade roughness on various performance parameters of a two-dimensional blade cascade. The 2D CFD model is based on a high resolution flux difference splitting scheme of Roe (1981). The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the zero-equation turbulence model of Baldwin-Lomax (1978) and two-equation Shear Stress Transport (SST) turbulence model. For the smooth blade, results are compared with experimental data to validate the model. Finally, a correlation between roughness Reynolds number and loss coefficient for both turbulence models is presented and tested for three other roughness heights. The results of 2D turbine blade cascades can be used for one-dimensional models such as mean line analysis or quasi-three-dimensional models e.g. streamline curvature method.

Experimental and Computational Comparisons of Fan-Shaped Film-Cooling on a Turbine Vane Surface

2005 ◽  
Author(s):  
W. Colban ◽  
K. A. Thole ◽  
M. Haendler
Keyword(s):  
Turbulence Model ◽  
Film Cooling ◽  
Turbulence Models ◽  
Complex Flow ◽  
Ir Camera ◽  
Turbine Engine ◽  
Film Cooling Effectiveness ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Film Cooling Holes

The flow exiting the combustor in a gas turbine engine is considerably hotter than the melting temperature of the turbine section components, of which the turbine nozzle guide vanes see the hottest gas temperatures. One method used to cool the vanes is to use rows of film-cooling holes to inject bleed air that is lower in temperature through an array of discrete holes onto the vane surface. The purpose of this study was to evaluate the row-by-row interaction of fan-shaped holes as compared to the performance of a single row of fan-shaped holes in the same locations. This study presents adiabatic film-cooling effectiveness measurements from a scaled-up, two-passage vane cascade. High resolution film-cooling measurements were made with an infrared (IR) camera at a number of engine representative flow conditions. Computational fluid dynamics (CFD) predictions were also made to evaluate the performance of some of the current turbulence models in predicting a complex flow such as turbine film-cooling. The RNG k-ε turbulence model gave a closer prediction of the overall level of film-effectiveness, while the v2-f turbulence model gave a more accurate representation of the flow physics seen in the experiments.

Numerical Study of Turbulent Flow Through Rib-Roughened Channels With Mist Injection

2014 ◽  
Author(s):  
Fifi N. M. Elwekeel ◽  
Qun Zheng ◽  
Antar M. M. Abdala
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Cross Sections ◽  
Numerical Study ◽  
Turbulence Models ◽  
Uniform Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Sst Turbulence Model ◽  
Volume Method

This study investigated heat transfer characteristics on various shaped ribs on the lower channel wall using steam and steam/mist as cooling fluid. The lower wall is subjected to a uniform heat flux condition while others walls are insulated. Calculations are carried out for ribs with square ribs (case A), triangular ribs (case B), trapezoidal ribs (case C) and (case D) cross sections over a range of Reynolds numbers (14000–35000), constant mist mass fraction (6%) and fixed rib height and pitch. To investigate turbulence model effects, computations based on a finite volume method, are carried out by utilizing three turbulence models: the standard k-ω, Omega Reynolds Stress (ωRS) and Shear Stress Transport (SST) turbulence models. The predicted results from using several turbulence models reveal that the SST turbulence model provide better agreement with available measurements than others. It is found that the heat transfer coefficients are enhanced in ribbed channels with injection of a small amount of mist. The steam/mist provides the higher heat transfer enhancement over steam when trapezoidal shaped ribs (38°, case C).

Applicability of Turbulence Models on Characteristics Prediction of Centrifugal Pumps

2011 ◽  
Author(s):  
Yong Wang ◽  
Houlin Liu ◽  
Shouqi Yuan ◽  
Minggao Tan ◽  
Minhua Shu
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Centrifugal Pumps ◽  
Commercial Code ◽  
Calculation Results ◽  
Sst Turbulence Model ◽  
Specific Speed ◽  
Turbulent Models ◽  
Experimental Values

In order to research the applicability of turbulence model on characteristics prediction of centrifugal pumps at the design condition, standard k-ε turbulence model, k-ω turbulence model and SST turbulence model are selected, which are commonly used in the numerical prediction for head, efficiency and NPSHr of the centrifugal pumps. By using commercial code ANSYS CFX, the all three turbulent models are used to predict the characteristics of six centrifugal pumps with the different specific speeds at the design condition, which are varied from 34.3 to 260.5. The calculation results are compared with the experimental data, and the comparison indicates that all the prediction results obtained from different turbulence models are more or less different from the experimental data. The head and efficiency predicted by SST turbulence model and k-ω turbulence model are closer and they are all bigger than that predicted by k-ε turbulence model. For low specific speed centrifugal pumps, the head and efficiency predicted by SST model and the NPSHr predicted by k-ε turbulence model are more closer to the experimental values; while for the medium and high specific speed centrifugal pumps, the head and efficiency predicted by k-ε turbulence model are better than that predicted by other models. The k-ω turbulence model and k-ε turbulence model are the best choice to predict NPSHr of medium and high specific speed centrifugal pumps respectively.

scholarly journals Numerical Study on the Aerodynamic Characteristics of the NACA 0018 Airfoil at Low Reynolds Number for Darrieus Wind Turbines Using the Transition SST Model

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 477
Author(s):  
Krzysztof Rogowski ◽  
Grzegorz Królak ◽  
Galih Bangga
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Wind Turbines ◽  
Numerical Study ◽  
Experimental Studies ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Reynolds Numbers ◽  
Time Step ◽  
Sst Turbulence Model

A symmetrical NACA 0018 airfoil is often used in such applications as small-to-medium scale vertical-axis wind turbines and aerial vehicles. A review of the literature indicates a large gap in experimental studies of this airfoil at low and moderate Reynolds numbers in the previous century. This gap has limited the potential development of classical turbulence models, which in this range of Reynolds numbers predict the lift coefficients with insufficiently accurate results in comparison to contemporary experimental studies. Therefore, this paper validates the aerodynamic performance of the NACA 0018 airfoil and the characteristics of the laminar separation bubble formed on its suction side using the standard uncalibrated four-equation Transition SST turbulence model and the unsteady Reynolds-averaged Navier-Stokes (URANS) equations. A numerical study was conducted for the chord Reynolds number of 160,000, angles of attack between 0 and 11 degrees, as well as for the free-stream turbulence intensity of 0.05%. The calculated lift and drag coefficients, aerodynamic derivatives, as well as the location and length of the laminar bubble quite well agree with the results of experimental measurements taken from the literature for validation. A sensitivity study of the numerical model was performed in this paper to examine the effects of the time-step size, geometrical parameters and mesh distribution around the airfoil on the simulation results. The airfoil data sets obtained in this work using the Transition SST and the k-ω SST turbulence models were used in the improved double multiple streamtube (IDMS) to calculate aerodynamic blade loads of a vertical-axis wind turbine. The characteristics of the normal component of the aerodynamic blade load obtained by the Transition SST approach are much better suited to the experimental data compared to the k-ω SST turbulence model.

Variations of cooling performance on turbine vanes due to incipient particle deposition

2021 ◽  
pp. 095765092110105
Author(s):  
Xing Yang ◽  
Zihan Hao ◽  
Zhenping Feng
Keyword(s):  
Mass Flow ◽  
Film Cooling ◽  
Particle Deposition ◽  
Early Stage ◽  
High Mass ◽  
Cooling Performance ◽  
Turbine Vanes ◽  
Changing Patterns ◽  
Low Mass ◽  
Grid Nodes

In this paper, to demonstrate the deposition effects on cooling performance, the changing patterns of film cooling due to particle deposition are numerically investigated on a turbine vane that is cooled by an array of film-holes. The uniqueness of this work is addressing the cooling performance at an early deposition stage, in which deposits are relatively slight. The build-ups of the deposits are simulated by moving grid nodes on the wall boundaries. Results show that in addition to particle velocity, the blowing conditions and wall temperatures are two important factors to determine the deposition patterns. Increasing coolant-to-mainstream mass flow ratios and lowering wall temperatures can help inhibit the growth of deposits. In addition, the modifications of the vane profile due to incipient deposition are completely different from those with excessive deposition. Although flow fields are less sensitive to the early-stage deposits in the subsonic vane passage, cooling effectiveness is significantly changed and the changes are linked to the mass flow ratios. Compared to the cooling performance from a non-deposition case, reduced cooling performance due to incipient deposition is found at a low mass flow ratio of 1.09%, while cooling performance is improved at moderate and high mass flow ratios of 1.64% and 2.06%.

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