Use of 2-D and 3-D unsteady RANS in the computation of wall bounded buoyant flows

2022 ◽  
Vol 93 ◽  
pp. 108914
Author(s):  
Constantinos Katsamis ◽  
Tim Craft ◽  
Hector Iacovides ◽  
Juan C. Uribe
Keyword(s):  
Buoyant Flows ◽  
Unsteady Rans

TURBULENT BUOYANT FLOWS IN ENCLOSURES

1990 ◽  
Author(s):  
Enrico Nobile ◽  
Antonio C. M. Sousa ◽  
Giovanni S. Barozzi
Keyword(s):  
Buoyant Flows

Effect of Wake Passing on Unsteady Aerodynamic Performance in a Turbine Stage

2006 ◽  
Author(s):  
K. Yamada ◽  
K. Funazaki ◽  
K. Hiroma ◽  
M. Tsutsumi ◽  
Y. Hirano ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Suction Side ◽  
Turbine Stage ◽  
Three Dimensional Flow ◽  
Unsteady Aerodynamic ◽  
Unsteady Effect ◽  
Unsteady Rans ◽  
Wake Passing ◽  
Stage Efficiency

In the present work, unsteady RANS simulations were performed to clarify several interesting features of the unsteady three-dimensional flow field in a turbine stage. The unsteady effect was investigated for two cases of axial spacing between stator and rotor, i.e. large and small axial spacing. Simulation results showed that the stator wake was convected from pressure side to suction side in the rotor. As a result, another secondary flow, which counter-rotated against the passage vortices, was periodically generated by the stator wake passing through the rotor passage. It was found that turbine stage efficiency with the small axial spacing was higher than that with the large axial spacing. This was because the stator wake in the small axial spacing case entered the rotor before mixing and induced the stronger counter-rotating vortices to suppress the passage vortices more effectively, while the wake in the large axial spacing case eventually promoted the growth of the secondary flow near the hub due to the migration of the wake towards the hub.

Unsteady RANS method for ship motions with application to roll for a surface combatant

2006 ◽  
Vol 35 (5) ◽  
pp. 501-524 ◽  
Author(s):  
Robert V. Wilson ◽  
Pablo M. Carrica ◽  
Fred Stern
Keyword(s):  
Ship Motions ◽  
Unsteady Rans ◽  
Surface Combatant ◽  
Rans Method

Low-Pressure Compressor Near-Stall Predictions Using Unsteady CFD Methods

2021 ◽  
Author(s):  
David Vanpouille ◽  
Dimitrios Papadogiannis ◽  
Stéphane Hiernaux
Keyword(s):  
Low Pressure ◽  
Navier Stokes ◽  
Phase Lag ◽  
Sliding Mesh ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Surge Margin ◽  
Large Eddy ◽  
Unsteady Rans ◽  
Pressure Compressor

Abstract Surge margin is critical for the safety of aeronautical compressors, hence predicting it early in the design process using CFD is mandatory. However, close to surge, steady-state Reynolds Averaged Navier-Stokes (RANS) simulations are proven inadequate. Unsteady techniques such as Unsteady RANS (URANS) and Large Eddy Simulation (LES) can provide more reliable predictions. Nevertheless, the accuracy of such methods are dependent on the method used to handle the rotor/stator interfaces. The most precise method, the sliding mesh, requires simulating the full annulus or a periodic sector, which can be very costly. Other techniques to reduce the domain exist, such as the phase-lagged approach or geometric blade scaling, but introduce restrictive assumptions on the flow at near-stall conditions. The objective of this paper is to investigate the near-stall flow of a low-pressure compressor using unsteady methods of varying fidelity: URANS with the phase lag assumption, URANS on a periodic sector and a high-fidelity LES on a smaller periodic sector achieved using geometric blade scaling. Results are compared to experimental measurements. An overall good agreement is found. Results show that the tip leakage vortex is not the origin of the stall on the studied configuration and a hub corner separation is initiated. LES further validates the (U)RANS flow predictions and brings additional insight on unsteady flow separations.

Numerical Investigation of Unsteady Film Cooling on the Turbine Shroud With the Blade Passing

2018 ◽  
Author(s):  
Chao Gao ◽  
Cun-liang Liu ◽  
Hai-yong Liu ◽  
Qi-ling Guo ◽  
Rui-dong Wang ◽  
...  
Keyword(s):  
Film Cooling ◽  
Experimental Studies ◽  
Relative Rotation ◽  
Film Blowing ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Sliding Mesh ◽  
Blowing Ratio ◽  
Blade Rotation ◽  
Unsteady Rans

Numerical simulations have been performed on the turbine shroud unsteady film cooling under the blade passing. There are many published experimental studies for turbine shroud heat transfer and a few computational fluid dynamics data. In this paper, unsteady RANS method has been performed to study the effect of the blade rotation speeds and the film blowing ratios on the behavior of film cooling effectiveness. And the sliding mesh in Fluent was used to achieve relative rotation between blade and shroud. These results are reported for blowing ratios of 1.0, 1.5, 2.0, blade rotation speeds of 1600 rpm, 1800rpm, 2089rpm, 2400rpm. The results show that the time instantaneous film cooling effectiveness on the shroud have a notable different distribution with the steady blade case. And at the rotation results, the film cooling effectiveness is even coverage with the blowing ratio increasing. The time-averaged film cooling effectiveness on the shroud increases by increasing the blowing ratio on all blade rotational velocities. And in this study, the blade at different rotation speeds, the distribution of time-averaged film cooling effectiveness has a significantly reduce on the shroud because of the relative movement of blade and shroud.

Experimental and Computational Investigation of Rayleigh-Bénard Flow in the Rotating Cavities of a Core Compressor

2017 ◽  
Author(s):  
M. R. Puttock-Brown ◽  
M. G. Rose ◽  
C. A. Long
Keyword(s):  
Free Convection ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
High Pressure Compressor ◽  
Aero Engine ◽  
Peripheral Surface ◽  
Unsteady Rans ◽  
The University ◽  
Rayleigh Benard ◽  
Pressure Compressor

This paper presents new experimental measurements, at conditions representative of an aero engine, of heat transfer from the inner peripheral surface (shroud) of a rotating cavity. The results are taken from the University of Sussex Multiple Cavity Rig, which is designed to be similar to a gas turbine high pressure compressor internal air system. The shroud Nusselt numbers are shown to be dependent on the shroud Grashof number and insensitive to throughflow axial Reynolds number. The magnitude of the shroud Nusselt numbers are consistent with accepted correlations for turbulent free convection from a horizontal plate, yet show a trend (gradient of Nusselt to Grashof numbers) that is similar to laminar free convection. A supporting high-resolution 3D unsteady RANS simulation was conducted to investigate the cavity flow structure with particular attention paid to the near shroud region. This demonstrated flow structures that are consistent with published work but also show the existence of a type of Rayleigh-Bénard flow that manifests as a series of streaks that propagate along the periphery of the cavity. These structures can be found in the literature albeit in different circumstances. Whilst these streaks have been shown in the simulation their existence cannot be ratified without experimental confirmation.

Modeling of Turbulent Buoyant Flows in Aircraft Cabins

1984 ◽  
Vol 39 (1-6) ◽  
pp. 107-118 ◽  
Author(s):  
K. T. Yang ◽  
J. R. Lloyd ◽  
A. M. Kanury ◽  
K. Satoh
Keyword(s):  
Aircraft Cabins ◽  
Buoyant Flows

Vortex Suppression Efficiency of Discontinuous Helicoidal Fins

2007 ◽  
Author(s):  
Antonio Pinto ◽  
Riccardo Broglia ◽  
Elena Ciappi ◽  
Andrea Di Mascio ◽  
Emilio F. Campana ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Computational Time ◽  
Reynolds Number Flow ◽  
Flow Past A Cylinder ◽  
Helical Strakes ◽  
Unsteady Rans ◽  
Number Flow ◽  
Offshore Industry ◽  
Good Trade ◽  
High Reynolds

Vortex-Induced Vibration (VIV) is one of the most demanding areas in the offshore industry, and detailed investigation of the fluid-structure interaction is becoming fundamental for designing new structures able to reduce VIV phenomenon. To carry on such analysis, and get reliable results in term of global coefficients, the correct modelling of turbulence, boundary layer, and separated flows is required. Nonetheless, the more accurate is the simulation, the more costly is the computation. Unsteady RANS simulations provide a good trade-off between numerical accuracy and computational time. This paper presents the analysis of the flow past a cylinder with several three-dimensional helical fins at high Reynolds number. Flow field, vortical structures, and response frequency patterns are analysed. Spectral analysis of data is performed to identify carrier frequencies, deemed to be critical due to the induced vibration of the whole structure. Finally, helical strakes efficiency in reducing the riser vibrations is also addressed, through direct consideration on the carrier shedding frequency.

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