scholarly journals Experimental and computational investigation of flow structure of buoyancy induced flow in heated rotating cavities

2021 ◽  
Vol 5 ◽  
pp. 148-163
Author(s):  
Seyed Mostafa Fazeli ◽  
Vasudevan Kanjirakkad ◽  
Christopher Long
Keyword(s):  
Laser Doppler Anemometry ◽  
Tangential Velocity ◽  
Test Facility ◽  
Navier Stokes ◽  
Test Case ◽  
Frequency Spectra ◽  
Spectra Analysis ◽  
Heated Disc ◽  
Induced Flow ◽  
Secondary Air

This paper presents Laser-Doppler Anemometry (LDA) measurements obtained from the Sussex Multiple Cavity test facility. This facility comprises a number of heated disc cavities with a cool bore flow and is intended to emulate the secondary air system flow in an H.P compressor. Measurements were made of the axial and tangential components of velocity over the respective range of Rossby, Rotational and Axial Reynolds numbers, (Ro, <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mtext>R</mml:mtext><mml:msub><mml:mtext>e</mml:mtext><mml:mi>θ</mml:mi></mml:msub></mml:math></inline-formula> and<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mspace width="0.25em"/><mml:mi mathvariant="normal">R</mml:mi></mml:mrow><mml:msub><mml:mtext>e</mml:mtext><mml:mi>z</mml:mi></mml:msub></mml:math></inline-formula>),<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mspace width="0.25em"/></mml:mrow><mml:mn>0.32</mml:mn><mml:mo><</mml:mo><mml:mtext>Ro</mml:mtext><mml:mo><</mml:mo><mml:mn>1.28</mml:mn></mml:math></inline-formula>,<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mspace width="0.25em"/><mml:mi mathvariant="normal">R</mml:mi></mml:mrow><mml:msub><mml:mtext>e</mml:mtext><mml:mi>θ</mml:mi></mml:msub><mml:mo>=</mml:mo><mml:mn>7.1</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>5</mml:mn></mml:msup></mml:math></inline-formula>, <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mn>1.2</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>4</mml:mn></mml:msup><mml:mo><</mml:mo><mml:mrow><mml:mspace width="0.25em"/><mml:mi mathvariant="normal">R</mml:mi></mml:mrow><mml:msub><mml:mtext>e</mml:mtext><mml:mi>z</mml:mi></mml:msub><mml:mo><</mml:mo><mml:mn>4.8</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>4</mml:mn></mml:msup></mml:math></inline-formula> and for the values of the buoyancy parameter <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mo stretchy="false">(</mml:mo><mml:mrow><mml:mi>β</mml:mi><mml:mrow><mml:mi mathvariant="normal">Δ</mml:mi></mml:mrow><mml:mtext>T</mml:mtext></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> :<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mspace width="0.25em"/></mml:mrow><mml:mn>0.50</mml:mn><mml:mo><</mml:mo><mml:mrow><mml:mspace width="0.25em"/><mml:mi>β</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">Δ</mml:mi></mml:mrow><mml:mtext>T</mml:mtext><mml:mo><</mml:mo><mml:mn>0.58</mml:mn></mml:math></inline-formula>. The frequency spectra analysis of the tangential velocity indicates the existence of pairs of vortices inside the cavities. The swirl number, <italic>X<sub>k</sub></italic>, calculated from these measurements show that the cavity fluid approaches solid body rotation near the shroud region. The paper also presents results from Unsteady Reynolds-Averaged Navier-Stokes (URANS) calculations for the test case where Ro = 0.64. The time-averaged LDA data and numerical results show encouraging agreement.

Self-induced flow in a rotating tube

1991 ◽  
Vol 230 ◽  
pp. 505-524 ◽  
Author(s):  
S. Gilham ◽  
P. C. Ivey ◽  
J. M. Owen ◽  
J. R. Pincombe
Keyword(s):  
Boundary Layer ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Laser Doppler Anemometry ◽  
Glass Tube ◽  
The Self ◽  
Navier Stokes ◽  
Ekman Number ◽  
Induced Flow ◽  
Short Tube

When a tube, sealed at one end and open to a quiescent environment at the other, is rotated about its axis, fluid flows from the open end along the axis towards the sealed end and returns in an annular boundary layer on the cylindrical wall. This paper describes the first known study to be made of this self-induced flow. Numerical solutions of the Navier–Stokes equations are shown to be in mainly good agreement with experimental results obtained using flow visualization and laser–Doppler anemometry in a rotating glass tube.The self-induced flow in the tube can be described in terms of the length-to-radius ratio, G, and the Ekman number, E. However, for large values of G (G [ges ] 20), the flow outside the boundary layer on the endwall of the tube can be characterized by a single, modified, Ekman number, E*, where E* = GE. Although most of the fluid entering the open end of the tube is entrained into the annular (Stewartson-type) boundary layer, for small values of E* (E* < 0.2) some flow reaches the sealed end. For this so-called 'short-tube case’, the flow in the boundary layer on the endwall is shown to be similar to that associated with a disk rotating in a quiescent environment: the free disk. The self-induced flow for the short-tube case is believed to be responsible for the ’ hot-poker effect’ used, on some jet engines, to provide ice protection for the nose bullet.

scholarly journals Experimental and Computational Investigation of Flow Structure in Buoyancy Dominated Rotating Cavities

2020 ◽  
Author(s):  
Seyed Mostafa Fazeli ◽  
Vasudevan Kanjirakkad ◽  
Christopher Long
Keyword(s):  
Laser Doppler Anemometry ◽  
Numerical Study ◽  
Tangential Velocity ◽  
Reynolds Numbers ◽  
Convincing Evidence ◽  
Navier Stokes ◽  
Computational Investigation ◽  
Cfd Simulations ◽  
Flow And Heat Transfer ◽  
A Value

Abstract The flow and heat transfer inside HP compressor rotating cavities are buoyancy driven and are known to be extremely difficult to predict. The experimental data of Laser-Doppler Anemometry (LDA) measurements inside an engine representative cavity rig is presented in this paper. Traverses using a two component LDA system have been carried out in the shaft bore and the cavity regions in order to map the axial and tangential velocity components. The velocity data is collected for a range of Rossby, Rotational and Axial Reynolds numbers, Ro, Reθ and Rez: 0.08 &lt; Ro &lt; 0.64, 7 × 105 &lt; Reθ &lt; 2.83 × 106, 1.2 × 104 &lt; Rez &lt; 4.8 × 104 and for values of the buoyancy parameter βΔT, 0.284 &lt; βΔT &lt; 0.55. Numerical study using unsteady Reynolds Averaged Navier-Stokes (URANS) simulations have been carried out to elucidate flow details for a few selected cases. The experimental results revealed that the Swirl number (Xk) varies from a value &lt; 1 near the bore to near solid body rotation at increased radii within the cavity. The analysis of frequency spectrum of the tangential velocity inside the cavities has also shown the existence of pairs of rotating and contra-rotating vortices. There is generally satisfactory agreement between measurements and CFD simulations. There is also convincing evidence of two or more separate regions in the flow dominated by the bore flow and rotation.

Buoyancy-Induced Flow in Open Rotating Cavities

2006 ◽  
Author(s):  
J. Michael Owen ◽  
Hans Abrahamsson ◽  
Klas Lindblad
Keyword(s):  
Tangential Velocity ◽  
Axial Flow ◽  
Quantitative Agreement ◽  
Turbine Engines ◽  
The Third ◽  
Commercial Code ◽  
Heated Disc ◽  
Induced Flow ◽  
Cooling Air ◽  
Buoyancy Induced Flow

Buoyancy-induced flow can occur in the cavity between the co-rotating compressor discs in gas-turbine engines, where the Rayleigh numbers can be in excess of 1012. In most cases the cavity is open at the centre, and an axial throughflow of cooling air can interact with the buoyancy-induced flow between the discs. Such flows can be modeled, computationally and experimentally, by a simple rotating cavity with an axial flow of air. This paper describes work conducted as part of ICAS-GT, a major European research project. Experimental measurements of velocity, temperature and heat transfer were obtained on a purpose-built experimental rig, and these results have been reported in an earlier paper. In addition, 3D unsteady CFD computations were carried out using a commercial code (Fluent) and an RNG k-ε turbulence model. The computed velocity vectors and contours of temperature reveal a flow structure in which, as seen by previous experimenters, ‘radial arms’ transport cold air from the centre to the periphery of the cavity, and regions of cyclonic and anti-cyclonic circulation are formed on either side of each arm. The computed radial distribution of the tangential velocity agrees reasonably well with the measurements in two of the three cases considered here. In the third case, the computations significantly over-predict the measurements; the reason for this is not understood. The computed and measured values of Nu for the heated disc show qualitatively similar radial distributions, with high values near the centre and the periphery. In two of the cases, the quantitative agreement is reasonably good; in the third case, the computations significantly under-predict the measured values.

Investigation of Penny Leakage Flows of Variable Guide Vanes in High Pressure Compressors

2016 ◽  
Author(s):  
Hannes Wolf ◽  
Matthias Franke ◽  
Alexander Halcoussis ◽  
Christophe Kleinclaus ◽  
Sébastien Gautier
Keyword(s):  
Complex Geometry ◽  
Test Facility ◽  
Navier Stokes ◽  
Test Case ◽  
Local Flow ◽  
Experimental Database ◽  
Eddy Simulation ◽  
Jet In Crossflow ◽  
Flow Features ◽  
Modelling Uncertainties

In this paper, the modelling of leakages through a compressor stator penny cavity, and their effect on the aerodynamics within the compressor are studied. The penny, sometimes also referred to as ‘button’, is the cylindrical platform feature of a variable stator normally found between a vane’s airfoil and spindle. The pennies nominally lie recessed into the compressor endwalls at hub and casing, with a surrounding clearance to ensure the vane’s stagger angle can be adjusted. RANS-simulations, with these clearances included, have shown a significant impact from the penny cavity leakages on compressor efficiency and surge line. Neglecting this secondary flow path through the penny cavities results in an under prediction of the losses close to the endwalls. The prediction of the penny cavity effect on the stator row is based on a Reynolds-Averaged-Navier-Stokes (RANS) study, using a hybrid structured-unstructured mesh to provide adequate resolution of the local flow phenomena. The complex geometry and pressure field result in flows that are unevenly distributed within the penny cavity. The outflow or leakage is focused in a concentrated area leading to a high local velocity that strongly impacts the stator losses and turning. Since such geometries lie beyond the normal validated cases, the modelling uncertainties are discussed and the plausibility of the results is checked. In order to provide an experimental database and validate the turbulent mixing of leakage and main flow, which is seen as the main contributor to loss production, a validation test case — ‘Jet-In-Crossflow’ was chosen. As well as the standard RANS code, this validation case was run as a time-accurate high-order Lattice Boltzmann (LBM) simulation (PowerFLOW), using Very-Large-Eddy-Simulation (VLES) turbulence modelling. The LBM simulation showed significant unsteady flow features and was considerably closer to the test data than the RANS calculations. A future test campaign, currently being prepared at the annular cascade test facility of the Institute of Jet Propulsion and Turbomachinery (IST) at RWTH Aachen university, will be briefly presented. This focuses on investigating the penny flows in a typical engine design.

scholarly journals Experimental and Computational Investigation of Flow Structure in Buoyancy Dominated Rotating Cavities

2020 ◽  
Author(s):  
Seyed Mostafa Fazeli ◽  
Vasudevan Kanjirakkad ◽  
C. A. Long
Keyword(s):  
Laser Doppler Anemometry ◽  
Numerical Study ◽  
Tangential Velocity ◽  
Reynolds Numbers ◽  
Convincing Evidence ◽  
Navier Stokes ◽  
Computational Investigation ◽  
Cfd Simulations ◽  
Flow And Heat Transfer ◽  
A Value

Abstract The flow and heat transfer inside HP compressor rotating cavities are buoyancy driven and are known to be extremely difficult to predict. The experimental data of Laser-Doppler Anemometry (LDA) measurements inside an engine representative cavity rig is presented in this paper. Traverses using a two component LDA system have been carried out in the shaft bore and the cavity regions in order to map the axial and tangential velocity components. The velocity data is collected for a range of Rossby, Rotational and Axial Reynolds numbers, Ro, Re? and Rez : 0.08&lt;Ro&lt;0.64,7×?10?^5&lt;?Re?_?&lt;2.83×?10?^6,1.2×?10?^4&lt;?Re?_z&lt;4.8×?10?^4 and for values of the buoyancy parameter ß??, 0.284&lt; ß?T&lt;0.55. Numerical study using unsteady Reynolds Averaged Navier-Stokes (URANS) simulations have been carried out to elucidate flow details for a few selected cases. The experimental results revealed that the Swirl number (Xk) varies from a value &lt; 1 near the bore to near solid body rotation at increased radii within the cavity. The analysis of frequency spectrum of the tangential velocity inside the cavities has also shown the existence of pairs of rotating and contra-rotating vortices. There is generally satisfactory agreement between measurements and CFD simulations. There is also convincing evidence of two or more separate regions in the flow dominated by the bore flow and rotation.

Multiscale Partially Averaged Navier Stokes Approach for the Prediction of Flow in Linear Compressor Cascade With Moving Casing

2011 ◽  
Author(s):  
Domenico Borello ◽  
Giovanni Delibra ◽  
Franco Rispoli
Keyword(s):  
Turbulence Models ◽  
Navier Stokes ◽  
Test Case ◽  
Compressor Cascade ◽  
Preliminary Assessment ◽  
Linear Compressor ◽  
Tip Leakage ◽  
Experimental Campaign ◽  
Elliptic Relaxation ◽  
Linear Compressor Cascade

In this paper we present an innovative Partially Averaged Navier Stokes (PANS) approach for the simulation of turbomachinery flows. The elliptic relaxation k-ε-ζ-f model was used as baseline Unsteady Reynolds Averaged Navier Stokes (URANS) model for the derivation of the PANS formulation. The well established T-FlowS unstructured finite volume in-house code was used for the computations. A preliminary assessment of the developed formulation was carried out on a 2D hill flow that represents a very demanding test case for turbulence models. The turbomachinery flow here investigated reproduces the experimental campaign carried out at Virginia Tech on a linear compressor cascade with tip leakage. Their measurements were used for comparisons with numerical results. The predictive capabilities of the model were assessed through the analysis of the flow field. Then an investigation of the blade passage, where experiments were not available, was carried out to detect the main loss sources.

URANS Studies of Effect of Eccentricity on Ship–Lock Interactions

2016 ◽  
Vol 13 (04) ◽  
pp. 1641012
Author(s):  
Qingjie Meng ◽  
Decheng Wan
Keyword(s):  
Viscous Flow ◽  
Hydrodynamic Interaction ◽  
Vertical Displacement ◽  
Navier Stokes ◽  
Test Case ◽  
The Third ◽  
Surface Pressure Distribution ◽  
Sst Turbulence Model ◽  
Unsteady Viscous Flow ◽  
Ship Lock

The unsteady viscous flow around a 12000TEU ship model entering the Third Set of Panama Locks with different eccentricity is simulated by solving the unsteady Reynolds averaged Navier–Stokes (RANS) equations in combination with the [Formula: see text]SST turbulence model. Overset grid technology is utilized to maintain grid orthogonality and the effects of the free surface are taken into account. The hydrodynamic forces, vertical displacement as well as surface pressure distribution are predicted and analyzed. First, a benchmark test case is designed to validate the capability of the present methods in the prediction of the viscous flow around the ship when maneuvering into the lock. The accumulation of water in front of the ship during entry into a lock is noticed. A set of systematic computations with different eccentricity are then carried out to examine the effect of eccentricity on the ship–lock hydrodynamic interaction.

Waves, jets and vortices: Regime transitions in shallow water turbulence

2021 ◽  
Author(s):  
Nikos Bakas
Keyword(s):  
Shallow Water ◽  
Large Scale ◽  
Rossby Waves ◽  
Phase Speed ◽  
Critical Value ◽  
Turbulent Regime ◽  
Wave Regime ◽  
Frequency Spectra ◽  
Spectra Analysis ◽  
Zonal Jets

&lt;p&gt;Forced-dissipative beta-plane turbulence in a single-layer shallow-water fluid has been widely considered as a simplified model of planetary turbulence as it exhibits turbulence self-organization into large-scale structures such as robust zonal jets and strong vortices. In this study we perform a series of numerical simulations to analyze the characteristics of the emerging structures as a function of the planetary vorticity gradient and the deformation radius. We report four regimes that appear as the energy input rate &amp;#949; of the random stirring that supports turbulence in the flow increases. A homogeneous turbulent regime for low values of &amp;#949;, a regime in which large scale Rossby waves form abruptly when &amp;#949; passes a critical value, a regime in which robust zonal jets coexist with weaker Rossby waves when &amp;#949; passes a second critical value and a regime of strong materially coherent propagating vortices for large values of &amp;#949;. The wave regime which is not predicted by standard cascade theories of turbulence anisotropization and the vortex regime are studied thoroughly. Wavenumber-frequency spectra analysis shows that the Rossby waves in the second regime remain phase coherent over long times. The coherent vortices are identified using the Lagrangian Averaged Deviation (LAVD) method. The statistics of the vortices (lifetime, radius, strength and speed) are reported as a function of the large scale parameters. We find that the strong vortices propagate zonally with a phase speed that is equal or larger than the long Rossby wave speed and advect the background turbulence leading to a non-dispersive line in the wavenumber-frequency spectra.&lt;/p&gt;

Effect of Scaling of Blade Row Sectors on the Prediction of Aerodynamic Forcing in a Highly-Loaded Transonic Compressor Stage

2009 ◽  
Author(s):  
Mari´a A. Mayorca ◽  
Jesu´s A. De Andrade ◽  
Damian M. Vogt ◽  
Hans Ma˚rtensson ◽  
Torsten H. Fransson
Keyword(s):  
Second Harmonic ◽  
Harmonic Excitation ◽  
Navier Stokes ◽  
Test Case ◽  
Moderate Amount ◽  
Object A ◽  
Transonic Compressor ◽  
Geometrical Scaling ◽  
Direct Indication ◽  
Generalized Force

An investigation of the sensitivity of a geometrical scaling technique on the blade forcing prediction and mode excitability has been performed. A stage of a transonic compressor is employed as test object. A scaling ratio is defined which indicates the amount of scaling from the original geometry. Different scaling ratios are selected and 3D Navier Stokes unsteady calculations completed for each scaled configuration. A full annulus calculation (non-scaled) is performed serving as reference. The quantity of interest is the generalized force, which gives a direct indication of the mode excitability. In order to capture both up- and downstream excitation effects the mode excitability has been assessed on both rotor and stator blades. The results show that first harmonic excitation can be predicted well for both up- and downstream excitation using moderate amount of scaling. On the other hand, the predictions of second harmonic quantities do show a higher sensitivity to scaling for the investigated test case.

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