The Prediction and Measurement of Incompressible Flow in a Labyrinth Seal

1989 ◽  
Vol 111 (4) ◽  
pp. 697-702 ◽  
Author(s):  
J. A. Demko ◽  
G. L. Morrison ◽  
D. L. Rhode
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Incompressible Flow ◽  
Labyrinth Seal ◽  
Substantial Effect ◽  
Navier Stokes ◽  
Computer Data ◽  
Computer Data Acquisition ◽  
Swirl Velocity ◽  
Hot Film

Predictions and measurements were obtained for incompressible flow in a labyrinth seal for Taylor numbers of 0, 7,600, and 19,000 at an axial Reynolds number near 50,000. A hot-film anemometer with computer data acquisition was used in obtaining the measurements. The computations were made using a turbulent flow Navier-Stokes finite difference code. The QUICK differencing scheme was utilized in order to diminish false diffusion. Comparison between experiments and predictions are given for the axial and swirl velocity components and turbulent kinetic energy. Also, the substantial effect of the Taylor number on the pressure distribution is presented.

Inception of Turbulence in the Stokes Boundary Layer Over a Transpiring Wall

2002 ◽  
Vol 124 (3) ◽  
pp. 678-684 ◽  
Author(s):  
Joseph Majdalani ◽  
James Barron ◽  
William K. Van Moorhem
Keyword(s):  
Reynolds Number ◽  
Standard Deviation ◽  
Side Wall ◽  
Flow Regimes ◽  
Computer Data ◽  
Computer Data Acquisition ◽  
Onset Of Turbulence ◽  
Wall Injection ◽  
Rectangular Chamber ◽  
Hot Film

In this work, the onset of turbulence inside a rectangular chamber is investigated, with and without side-wall injection, in the presence of an oscillatory pressure gradient. Two techniques are used to define the transition from laminar to turbulent regimes: statistical analysis and flow visualization. Calibrated hot film anemometry and a computer data acquisition system are used to record and analyze acoustical flow data. Four classifications of flow regimes are reported: (a) laminar, (b) distorted laminar, (c) weakly turbulent, and (d) conditionally turbulent. Despite numerous attempts to promote turbulence, a fully turbulent flow does not develop at any of the driving frequencies tested. Statistical measurements reveal that a periodic drop in standard deviation of axial velocity fluctuations always occurs, indicating relaminarization within each cycle. Transition between flow regimes is assessed from the standard deviation of velocity data correlated as a function of the acoustic Reynolds number ReA. Under predominantly laminar conditions, the standard deviation is found to vary approximately with the square of the acoustic Reynolds number. Under turbulent conditions, the standard deviation becomes almost directly proportional to the acoustic Reynolds number. Inception of turbulence in the oscillatory flow with side-wall injection is found to be reproducible at the same critical value of ReA≅200.

Transient inertial hydrodynamic interaction between two identical spheres settling at small Reynolds number

2008 ◽  
Vol 605 ◽  
pp. 263-279 ◽  
Author(s):  
B. U. FELDERHOF
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Relative Motion ◽  
Hydrodynamic Interaction ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Small Reynolds Number ◽  
Navier Stokes Equations ◽  
Small Constant ◽  
Distance Vector

The flow pattern generated by a sphere accelerated from rest by a small constant applied forceshows scaling behaviour at long times, as can be shown from the solution of the linearized Navier–Stokes equations. In the scaling regime the kinetic energy of the flow grows with thesquare root of time. For two distant settling spheres starting from rest the kinetic energy ofthe flow depends on the distance vector between centres; owing to interference of the flowpatterns. It is argued that this leads to relative motion of the two spheres. Thecorresponding interaction energy is calculated explicitly in the scaling regime.

Effects of Pressure Ratio and Sealing Clearance on Leakage Flow Characteristics in the Rotating Honeycomb Labyrinth Seal

2007 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Guojun Li ◽  
Zhenping Feng
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Aerodynamic Efficiency ◽  
Flow Losses ◽  
Leakage Flow Rate ◽  
Swirl Velocity

Honeycomb stepped labyrinth seals in turbomachinery enhance aerodynamic efficiency by reducing leakage flow losses through the clearance between rotating and stationary components. The influence of pressure ratio and sealing clearance on the leakage flow characteristics in the honeycomb stepped labyrinth seal is numerically determined. The geometries investigated represent designs of the honeycomb labyrinth seal typical for modern turbomachinery. The leakage flow fields in the honeycomb and smooth stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT. Numerical simulations covered a range of pressure ratio and three sizes of sealing clearance for the honeycomb and smooth stepped labyrinth seals. The numerical discharge coefficients of the non-rotating honeycomb and smooth stepped labyrinth seals are in good agreement with previous experimental data. In addition rotational effects are also taken into account in numerical computations. The numerical results show that the leakage flow rate increases with the increasing pressure ratio at the fixed sealing clearance for the rotating and non-rotating honeycomb labyrinth seal. The influence of the sealing clearance on the leakage flow pattern for the rotating and non-rotating honeycomb labyrinth seal are observed. Moreover, the similar leakage flow rates are obtained at the same flow condition between the rotating and non-rotating honeycomb labyrinth seal due to the honeycomb acts to kill swirl velocity development for the rotating honeycomb labyrinth seal.

scholarly journals A Comparative Investigation of Corresponding Annular and Labyrinth Seal Flowfields

1989 ◽  
Author(s):  
D. L. Rhode ◽  
R. I. Hibbs
Keyword(s):  
Computer Code ◽  
Labyrinth Seal ◽  
Momentum Conservation ◽  
Comparative Investigation ◽  
Navier Stokes ◽  
Unexpected Finding ◽  
Labyrinth Seals ◽  
Swirl Velocity ◽  
Small Clearance ◽  
Annular Seal

A previous Navier-Stokes finite difference computer code is extended in order to compute seal leakage directly from given upstream and downstream reservoir pressures. The numerical results are in excellent agreement with previous measurements, the discrepancy being less than eight percent. Annual seals are found to leak approximately twenty percent more than corresponding labyrinths over the entire range of realistic clearance. A rather unexpected finding is that a dramatic increase of swirl velocity occurs near the discharge of small clearance annular seals, which does not arise in corresponding labyrinth seals. The results, which are used to explain this finding, show that a large density drop occurs near the small clearance annular seal exit, which provides the swirl velocity increase in accordance with angular momentum conservation.

Clearance Effects on Corresponding Annular and Labyrinth Seal Flow Leakage Characteristics

1993 ◽  
Vol 115 (4) ◽  
pp. 699-704 ◽  
Author(s):  
D. L. Rhode ◽  
R. I. Hibbs
Keyword(s):  
Computer Code ◽  
Labyrinth Seal ◽  
Momentum Conservation ◽  
Navier Stokes ◽  
Unexpected Finding ◽  
Labyrinth Seals ◽  
Swirl Velocity ◽  
Small Clearance ◽  
Annular Seal ◽  
Annular Seals

A previous Navier-Stokes finite difference computer code is extended in order to compute seal leakage directly from given upstream and downstream reservoir pressures. The numerical results are in excellent agreement with previous measurements, the discrepancy being less than eight percent. Annular seals are found to leak approximately twenty percent more than corresponding labyrinths over the entire range of realistic clearance. A rather unexpected finding is that a dramatic increase of swirl velocity occurs near the discharge of small-clearance annular seals, which does not arise in corresponding labyrinth seals. The results, which are used to explain this finding, show that a large density drop occurs near the small-clearance annular seal exit, which provides the swirl velocity increase in accordance with angular momentum conservation.

Effect of Tooth Height, Tooth Width and Shaft Diameter on Carry-Over Coefficient of Labyrinth Seals

2009 ◽  
Author(s):  
Saikishan Suryanarayanan ◽  
Gerald L. Morrison
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Labyrinth Seal ◽  
Major Effect ◽  
Labyrinth Seals ◽  
Shaft Diameter ◽  
Tooth Width ◽  
Pitch Ratio ◽  
Carry Over ◽  
Coefficient Of Discharge

The accuracy of rotodynamic analysis of any turbomachinery is dependent upon the accuracy of seal leakage prediction. An expression for the leakage through a labyrinth seal can be developed by combining the coefficient of discharge under each tooth and a carryover coefficient to account for the dissipation of kinetic energy of the jet emerging from under each tooth in the subsequent cavity through turbulence viscosity interaction. While most popularly used leakage models consider the carry-over coefficient only as a function of clearance and pitch, it was established in our earlier work that Reynolds number and clearance/pitch ratio have a major effect on the carry-over coefficient. This work extends the carry-over coefficient model presented by Saikishan Suryanarayanan and G.L. Morrison [1] for incompressible, straight through, rectangular cavity, tooth on stator labyrinth seals by studying and incorporating the effect of tooth width, pitch, tooth height and shaft diameter in addition to Reynolds number and clearance on the carry-over coefficient. It is shown that the tooth width/pitch ratio has a significant effect upon the carry-over coefficient.

INCOMPRESSIBLE FLOW AT LOW REYNOLDS NUMBER IN A CONICAL ENTRANCE ORIFICE PLATE

2019 ◽  
Author(s):  
MARA NILZA ESTANISLAU REIS ◽  
Wender Oliveira ◽  
Pedro Américo Almeida Magalhães Júnior
Keyword(s):  
Reynolds Number ◽  
Incompressible Flow ◽  
Low Reynolds Number ◽  
Orifice Plate ◽  
Low Reynolds

The flow of liquid in a stream from the standard turbine impeller

1979 ◽  
Vol 44 (3) ◽  
pp. 700-710 ◽  
Author(s):  
Ivan Fořt ◽  
Hans-Otto Möckel ◽  
Jan Drbohlav ◽  
Miroslav Hrach
Keyword(s):  
Reynolds Number ◽  
Kinematic Viscosity ◽  
Momentum Flux ◽  
Relative Size ◽  
Mean Velocity ◽  
Axial Profile ◽  
The Mean ◽  
Hot Film ◽  
Turbine Impeller

Profiles of the mean velocity have been analyzed in the stream streaking from the region of rotating standard six-blade disc turbine impeller. The profiles were obtained experimentally using a hot film thermoanemometer probe. The results of the analysis is the determination of the effect of relative size of the impeller and vessel and the kinematic viscosity of the charge on three parameters of the axial profile of the mean velocity in the examined stream. No significant change of the parameter of width of the examined stream and the momentum flux in the stream has been found in the range of parameters d/D ##m <0.25; 0.50> and the Reynolds number for mixing ReM ##m <2.90 . 101; 1 . 105>. However, a significant influence has been found of ReM (at negligible effect of d/D) on the size of the hypothetical source of motion - the radius of the tangential cylindrical jet - a. The proposed phenomenological model of the turbulent stream in region of turbine impeller has been found adequate for values of ReM exceeding 1.0 . 103.

scholarly journals Numerical analysis of high-lift configurations with oscillating flaps

2021 ◽  
Author(s):  
Johannes Ruhland ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Separated Flow ◽  
Navier Stokes ◽  
Rotational Axis ◽  
High Lift ◽  
Hinge Point ◽  
Reduced Frequency ◽  
Flap Deflection ◽  
The Impact

AbstractThis study presents two-dimensional aerodynamic investigations of various high-lift configuration settings concerning the deflection angles of droop nose, spoiler and flap in the context of enhancing the high-lift performance by dynamic flap movement. The investigations highlight the impact of a periodically oscillating trailing edge flap on lift, drag and flow separation of the high-lift configuration by numerical simulations. The computations are conducted with regard to the variation of the parameters reduced frequency and the position of the rotational axis. The numerical flow simulations are conducted on a block-structured grid using Reynolds Averaged Navier Stokes simulations employing the shear stress transport $$k-\omega $$ k - ω turbulence model. The feature Dynamic Mesh Motion implements the motion of the oscillating flap. Regarding low-speed wind tunnel testing for a Reynolds number of $$0.5 \times 10^{6}$$ 0.5 × 10 6 the flap movement around a dropped hinge point, which is located outside the flap, offers benefits with regard to additional lift and delayed flow separation at the flap compared to a flap movement around a hinge point, which is located at 15 % of the flap chord length. Flow separation can be suppressed beyond the maximum static flap deflection angle. By means of an oscillating flap around the dropped hinge point, it is possible to reattach a separated flow at the flap and to keep it attached further on. For a Reynolds number of $$20 \times 10^6$$ 20 × 10 6 , reflecting full scale flight conditions, additional lift is generated for both rotational axis positions.

Simulating flow separation from continuous surfaces: routes to overcoming the Reynolds number barrier

2009 ◽  
Vol 367 (1899) ◽  
pp. 2885-2903 ◽  
Author(s):  
Michael Leschziner ◽  
Ning Li ◽  
Fabrizio Tessicini
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Major Elements ◽  
Wall Layer ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Models ◽  
High Reynolds ◽  
Near Wall

This paper provides a discussion of several aspects of the construction of approaches that combine statistical (Reynolds-averaged Navier–Stokes, RANS) models with large eddy simulation (LES), with the objective of making LES an economically viable method for predicting complex, high Reynolds number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail: one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

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