Transitional flow between contra-rotating disks

1994 ◽  
Vol 281 ◽  
pp. 119-135 ◽  
Author(s):  
M. Kilic ◽  
X. Gan ◽  
J. M. Owen
Keyword(s):  
Boundary Layers ◽  
Cell Structure ◽  
Rotating Disk ◽  
Transitional Flow ◽  
Free Shear Layer ◽  
Rotating Disks ◽  
Double Transition ◽  
Type Flow ◽  
Radial Outflow ◽  
Good Agreement

This paper describes a combined computational and experimental study of the flow between contra-rotating disks for – 1 ≤ Γ ≤ 0 and Reϕ = 105, where Γ is the ratio of the speed of the slower disk to that of the faster one and Reϕ is the rotational Reynolds number of the faster disk. For Γ = 0, the rotor-stator case, laminar and turbulent computations and experimental measurements show that laminar Batchelor-type flow occurs: there is radial outflow in a boundary layer on the rotating disk, inflow on the stationary disk and a rotating core of fluid between. For Γ = – 1, the laminar computations produce Batchelor-type flow: there is radial outflow on both disks and inflow in a free shear layer in the mid-plane, on either side of which is a rotating core of fluid. The turbulent computations and the velocity measurements for Γ = – 1 show Stewartson-type flow: radial outflow occurs in laminar boundary layers on the disks and inflow occurs in a non-rotating turbulent core between the boundary layers. For intermediate values of Γ, transition from Batchelor-type flow to Stewartson-type flow is associated with a two-cell structure, the two-cells being separated by a streamline that stagnates on the slower disk; Batchelor-type flow occurs radially outward of the stagnation point and Stewartson-type flow radially inward. The turbulent computations are mainly in good agreement with the measured velocities for Γ = 0 and Γ = – 1, where either Batchelor-type flow or Stewartson-type flow occurs; there is less good agreement at intermediate values of Γ, particularly for Γ = – 0.4 where the double transition of Batchelor-type flow to Stewartson-type flow and laminar to turbulent flow occurs in the two-cell structure.

Computation of Flow Between Two Disks Rotating at Different Speeds

2003 ◽  
Vol 125 (2) ◽  
pp. 394-400 ◽  
Author(s):  
Muhsin Kilic ◽  
J. Michael Owen
Keyword(s):  
Boundary Layers ◽  
Gas Turbines ◽  
Reynolds Numbers ◽  
Internal Cooling ◽  
Rotating Disks ◽  
Measured Velocity ◽  
Layer Flow ◽  
Radial Outflow ◽  
Cooling Air ◽  
Good Agreement

Disks rotating at different speeds are found in the internal cooling-air systems of most gas turbines. Defining Γ as the ratio of the rotational speed of the slower disk to that of the faster one then Γ=−1, 0 and +1 represents the three important cases of contra-rotating disks, rotor-stator systems and co-rotating disks, respectively. A finite-volume, axisymmetric, elliptic, multigrid solver, employing a low-Reynolds-number k-ε turbulence model, is used for the fluid-dynamics computations in these systems. The complete Γ region, −1⩽Γ⩽+1, is considered for rotational Reynolds numbers of up to Reϕ=1.25×106, and the effect of a radial outflow of cooling air is also included for nondimensional flow rates of up to Cw=9720. As Γ→−1, Stewartson-flow occurs with radial outflow in boundary layers on both disks and between which is a core of nonrotating fluid. For Γ≈0, Batchelor-flow occurs, with radial outflow in the boundary layer on the faster disk, inflow on the slower one, and between which is a core of rotating fluid. As Γ→+1, Ekman-layer flow dominates with nonentraining boundary layers on both disks and a rotating core between. Where available, measured velocity distributions are in good agreement with the computed values.

scholarly journals Effects of the rotation number on flow and heat transfer in contra-rotating disk cavity with superposed flow

2019 ◽  
Vol 11 (10) ◽  
pp. 168781401988104 ◽  
Author(s):  
Shu-xian Chen ◽  
Jing-zhou Zhang
Keyword(s):  
Heat Transfer ◽  
Flow Structure ◽  
Rotation Number ◽  
Tangential Velocity ◽  
Inertial Force ◽  
Rotating Disk ◽  
Rotating Disks ◽  
Radial Temperature ◽  
Disk Rotation ◽  
Type Flow

The turbulent fluid flow and convective heat transfer in counter-rotating disk cavity with central axial air inflow and radial air outflow are numerically studied based on the finite volume method. Efforts are focused upon the influence of the rotation number Rt on the flow structure, cooling performance, sealing effect, and surface tangential friction characteristics in the cavity. The stagnation point where the radial outward flow along the upstream disk driven by the rotation force meets the radial outward flow along downstream disk driven by the combination of rotation force and inflow inertial force moves from upstream disk wall to the shroud with increasing Rt. At the Rt far smaller than 1, the fluids in the core region between two disks rotate with the upstream disk like a rigid body, and the tangential velocity of the rotating core decreases with the increase of the disk cavity radius, which is different from the Batchelor-type flow. At the Rt larger than 1, the fluids on the upstream disk side rotate like the Batchelor-type flow, while the sandwich rotation disappears in the fluid on the downstream disk side. The temperature on the upstream disk wall increases and then decreases with increasing values of Rt, and the critical value of Rt for the change of temperature variation is assessed to be at about Rt = 0.69. The temperature and radial temperature gradient of the downstream disk wall decrease with increasing Rt. With increasing Rt by increasing the disk rotation rate, the pressures near the downstream disk decrease, while the frictional moments on rotating disks increase. Due to the effect of flow structure, the frictional moment on the upstream disk is smaller than that on the downstream disk.

Turbulent Flow Between Two Disks Contrarotating at Different Speeds

1996 ◽  
Vol 118 (2) ◽  
pp. 408-413 ◽  
Author(s):  
M. Kilic ◽  
X. Gan ◽  
J. M. Owen
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Unsteady Flow ◽  
Turbulent Flow ◽  
Boundary Layers ◽  
Axial Flow ◽  
Radial Component ◽  
Velocity Measurements ◽  
Type Flow ◽  
Radial Outflow

This paper describes a combined computational and experimental study of the turbulent flow between two contrarotating disks for −1 ≤ Γ ≤ 0 and Reφ ≈ 1.2 × 106, where Γ is the ratio of the speed of the slower disk to that of the faster one and Reφ is the rotational Reynolds number. The computations were conducted using an axisymmetric elliptic multigrid solver and a low-Reynolds-number k–ε turbulence model. Velocity measurements were made using LDA at nondimensional radius ratios of 0.6 ≤ x ≤ 0.85. For Γ = 0, the rotor–stator case, Batchelor-type flow occurs: There is radial outflow and inflow in boundary layers on the rotor and stator, respectively, between which is an inviscid rotating core of fluid where the radial component of velocity is zero and there is an axial flow from stator to rotor. For Γ = −1, antisymmetric contrarotating disks, Stewartson-type flow occurs with radial outflow in boundary layers on both disks and inflow in the viscid nonrotating core. At intermediate values of Γ, two cells separated by a streamline that stagnates on the slower disk are formed: Batchelor-type flow and Stewartson-type flow occur radially outward and inward, respectively, of the stagnation streamline. Agreement between the computed and measured velocities is mainly very good, and no evidence was found of nonaxisymmetric or unsteady flow.

scholarly journals The elephant mode between two rotating disks

2008 ◽  
Vol 598 ◽  
pp. 451-464 ◽  
Author(s):  
BERTRAND VIAUD ◽  
ERIC SERRE ◽  
JEAN-MARC CHOMAZ
Keyword(s):  
Global Bifurcation ◽  
Rotating Disk ◽  
Finite Amplitude ◽  
Rotating Disks ◽  
Global Mode ◽  
Precise Analysis ◽  
Crossflow Instability ◽  
Single Disk ◽  
Source Sink ◽  
Good Agreement

Spectral direct numerical simulations (DNS) are carried out for a source–sink flow in an annular cavity between two co-rotating disks. When the Reynolds number based on the forced inflow is increased, a self-sustained crossflow instability of finite amplitude is observed. We show that this nonlinear global mode is made up of a front located at the upstream boundary of the absolutely unstable domain, followed by a saturated spiral mode, and that its properties are in good agreement with results of the local stability theory. This structure is characteristic of the so-called elephant mode of Pier & Huerre (J. Fluid Mech. vol. 435, 2001, p. 145). The global bifurcation is subcritical since only large-amplitude initial perturbations are found to trigger the elephant mode. Small-amplitude perturbations induce a long-lasting transient growth but lead eventually to a damped linear global mode, showing that non-parallel effects counteract the absolute instability and restabilize the flow. A similar linear global stabilization due to non-parallel effects has been found in the case of the flow above a single rotating disk. For the single-disk geometry, the existence of an elephant mode would imply, together with results of Davies & Carpenter (2003) a subcritical global instability, which has not yet been demonstrated. Although the present geometry differs from the single-disk case, the existence of a subcritical global bifurcation is now established, allowing a precise analysis of the transition scenarios.

On the Friction Reducing Non-Newtonian Flow Around an Enclosed Disk

1974 ◽  
Vol 41 (1) ◽  
pp. 45-50 ◽  
Author(s):  
E. Bilgen ◽  
P. Vasseur
Keyword(s):  
Theoretical Analysis ◽  
Turbulent Flow ◽  
Boundary Layers ◽  
Flow Characteristics ◽  
Rotating Disk ◽  
Newtonian Flow ◽  
Dilute Polymer Solutions ◽  
Theoretical Predictions ◽  
Minimum Resistance ◽  
Good Agreement

The turbulent flow characteristics of non-Newtonian dilute polymer solutions around an enclosed rotating disk have been studied both theoretically and experimentally. In the theoretical analysis, the momentum equations of the boundary layers on both rotating disk and housing have been solved numerically using appropriate velocity profiles. It is shown that the theoretical predictions for minimum resistance conditions are in good agreement with the experimental results of this study and with those in the literature.

Flow Between Contrarotating Disks

1995 ◽  
Vol 117 (2) ◽  
pp. 298-305 ◽  
Author(s):  
X. Gan ◽  
M. Kilic ◽  
J. M. Owen
Keyword(s):  
Turbulent Flow ◽  
Shear Layer ◽  
Boundary Layers ◽  
Turbulence Model ◽  
Computational Study ◽  
Reynolds Numbers ◽  
The Core ◽  
Wide Range ◽  
Type Flow ◽  
Radial Outflow

The paper describes a combined experimental and computational study of laminar and turbulent flow between contrarotating disks. Laminar computations produce Batchelor-type flow: Radial outflow occurs in boundary layers on the disks and inflow is confined to a thin shear layer in the midplane; between the boundary layers and the shear layer, two contrarotating cores of fluid are formed. Turbulent computations (using a low-Reynolds-number k–ε turbulence model) and LDA measurements provide no evidence for Batchelor-type flow, even for rotational Reynolds numbers as low as 2.2 × 104. While separate boundary layers are formed on the disks, radial inflow occurs in a single interior core that extends between the two boundary layers; in the core, rotational effects are weak. Although the flow in the core was always found to be turbulent, the flow in the boundary layers could remain laminar for rotational Reynolds numbers up to 1.2 × 105. For the case of a superposed outflow, there is a source region in which the radial component of velocity is everywhere positive; radially outward of this region, the flow is similar to that described above. Although the turbulence model exhibited premature transition from laminar to turbulent flow in the boundary layers, agreement between the computed and measured radial and tangential components of velocity was mainly good over a wide range of nondimensional flow rates and rotational Reynolds numbers.

Blunt Trailing Edge Shear Wake Development With Turbulent In-Flow Boundary Layers

2005 ◽  
Author(s):  
Dhanalakshmi Challa ◽  
Joe Klewicki
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Boundary Layers ◽  
High Speed ◽  
Velocity Ratio ◽  
Free Shear Layer ◽  
Low Speed ◽  
Axial Pressure Gradient ◽  
Layer Flow ◽  
Good Agreement

Experiments are conducted to explore the structural mechanisms involved in the post-separation evolution of a wall-bounded to a free-shear turbulent flow. At the upstream, both the boundary layers are turbulent. Experiments were conducted in a two-stream shear-layer tunnel, under a zero axial pressure gradient shear-wake configuration. A velocity ratio near 2 was explored. Profile data were collected with a single wire probe at various locations downstream of the blunt separation lip. With this set of measurements, mean profile, axial intensity and measures of profile evolution indicate that the predominant shift from turbulent boundary layer to free shear-layer like behavior occurs between the downstream locations x/θ = 13.7 & 27.4, where θ is the upstream momentum deficit thickness on the low-speed stream. The shear wake width is observed to be nominally constant with the downstream position. Axial velocity spectra show that the transition from boundary layer flow to shear flow occurs earlier in high-speed stream when compared to low speed stream. Strouhal number, Sto, of initial vortex rollup based on initial momentum thickness was found to be 0.034, which is in very good agreement with the existing literature. Other measures are in good agreement with linear stability considerations found in the literature.

Turbulent Flow Between Two Discs Contra-Rotating at Differential Speeds

1994 ◽  
Author(s):  
Muhsin Kilic ◽  
Xiaopeng Gan ◽  
J. Michael Owen
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Boundary Layers ◽  
Axial Flow ◽  
Radial Component ◽  
Velocity Measurements ◽  
Rotating Discs ◽  
Type Flow ◽  
Radial Outflow

This paper describes a combined computational and experimental study of the turbulent flow between two contra-rotating discs for −1 ≤ Γ ≤ 0 and Reφ ≃ 1.2 × 106, where Γ is the ratio of the speed of the slower disc to that of the faster one and Reφ is the rotational Reynolds number. The computations were conducted using an axisymmetric elliptic multigrid solver and a low-Reynolds-number k-ε turbulence model. Velocity measurements were made using LDA at nondimensional radius ratios of 0.6 ≤ x ≤ 0.85. For Γ = 0, the rotor-stator case, Batchelor-type flow occurs: there is radial outflow and inflow in boundary layers on the rotor and stator, respectively, between which is an inviscid rotating core of fluid where the radial component of velocity is zero and there is an axial flow from stator to rotor. For Γ = −1, anti-symmetrical contra-rotating discs, Stewartson-type flow occurs with radial outflow in boundary layers on both discs and inflow in the viscid nonrotating core. At intermediate values of Γ, two cells separated by a streamline that stagnates on the slower disc are formed: Batchelor-type flow and Stewartson-type flow occur radially outward and inward, respectively, of the stagnation streamline. Agreement between the computed and measured velocities is mainly very good, and no evidence was found of nonaxisymmetric or unsteady flow.

Computation of Flow Between Two Discs Rotating at Different Speeds

2002 ◽  
Author(s):  
Muhsin Kilic ◽  
J. Michael Owen
Keyword(s):  
Boundary Layers ◽  
Gas Turbines ◽  
Reynolds Numbers ◽  
Internal Cooling ◽  
Measured Velocity ◽  
Rotating Discs ◽  
Layer Flow ◽  
Radial Outflow ◽  
Cooling Air ◽  
Good Agreement

Discs rotating at different speeds are found in the internal cooling-air systems of most gas turbines. Defining Γ as the ratio of the rotational speed of the slower disc to that of the faster one then Γ = −1, 0 and +1 represents the three important cases of contra-rotating discs, rotor-stator systems and co-rotating discs, respectively. A finite-volume, axisymmetric, elliptic, multigrid solver, employing a low-Reynolds-number k-ε turbulence model, is used for the fluid-dynamics computations in these systems. The complete Γ region, −1 ≤ Γ ≤ +1, is considered for rotational Reynolds numbers of up to Reφ = 1.25 × 106, and the effect of a radial outflow of cooling air is also included for nondimensional flow rates of up to Cw = 9720. As Γ → −1, Stewartson-flow occurs with radial outflow in boundary layers on both discs and between which is a core of nonrotating fluid. For Γ ≈ 0, Batchelor-flow occurs, with radial outflow in the boundary layer on the faster disc, inflow on the slower one, and between which is a core of rotating fluid. As Γ → +1, Ekman-layer flow dominates with nonentraining boundary layers on both discs and a rotating core between. Where available, measured velocity distributions are in good agreement with the computed values.

Flow Between Contra-Rotating Discs

1993 ◽  
Author(s):  
Xiaopeng Gan ◽  
Muhsin Kilic ◽  
J. Michael Owen
Keyword(s):  
Turbulent Flow ◽  
Shear Layer ◽  
Boundary Layers ◽  
Turbulence Model ◽  
Reynolds Numbers ◽  
The Core ◽  
Rotating Discs ◽  
Wide Range ◽  
Type Flow ◽  
Radial Outflow

The paper describes a combined experimental and computational study of laminar and turbulent flow between contra-rotating discs. Laminar computations produce Batchelor-type flow: radial outflow occurs in boundary layers on the discs and inflow is confined to a thin shear layer in the mid-plane; between the boundary layers and the shear layer, two contra-rotating cores of fluid are formed. Turbulent computations (using a low-Reynolds-number k-ε turbulence model) and LDA measurements provide no evidence for Batchelor-type flow, even for rotational Reynolds numbers as low as 2.2 × 104. Whilst separate boundary layers are formed on the discs, radial inflow occurs in a single interior core that extends between the two boundary layers; in the core, rotational effects are weak. Although the flow in the core was always found to be turbulent, the flow in the boundary layers could remain laminar for rotational Reynolds numbers up to 1.2 × 105. For the case of a superposed outflow, there is a source region in which the radial component of velocity is everywhere positive; radially outward of this region, the flow is similar to that described above. Although the turbulence model exhibited premature transition from laminar to turbulent flow in the boundary layers, agreement between the computed and measured radial and tangential components of velocity was mainly good over a wide range of nondimensional flow rates and rotational Reynolds numbers.

Sign in / Sign up

Export Citation Format

Share Document