Numerical predictions and experimental analysis of small clearance ratio Taylor-Couette flows
Numerical predictions and experimental analysis of small clearance ratio Taylor-Couette flows
An integrated electrical thruster unit for use with work-class under water vehicles has a gap between two cylinders with the inner one rotating resulting in Taylor-Couette flow. It has a small clearance ratio with low Reynolds number turbulent Taylor vortices. To assess the frictional loss in the gap empirical equations were compared, but these show large discrepancies for the small gaps present in the thruster. From these empirical relations a 2mm gap was chosen for the design of the thruster unit. Published literature indicates that the start-up conditions affect the torque due to different Taylor vortex length and also raises questions about the existence of Görtler-type vortices within the turbulent Taylor vortices.
To analyse the flow an experimental rig was designed and constructed with a dynamically similar clearance ratio with a gap of 10mm and an inner radius of 710mm. The presence of Taylor vortices was clearly demonstrated, using bubbles to visualise the flow. A novel method of analysing the bubbles as a probability spectrum, to measure Taylor vortex length, has been developed. The friction resistance has been measured, demonstrating the empirical equations are approximately correct, from analysis of the power lost in the motor used to drive the rig and dynamometry attached to the outer cylinder.
The laminar flow has been successfully modelled with ELMORE, an in-house finite volume Navier-Stokes code with grid independent solutions. Studies were carried out on the effect of Reynolds number and end boundaries conditions on flow properties. These proved that if the vortex size is that of a critical length then the skin friction was the highest, unless adjacent to the end wall. It was also shown that is was possible to model just one vortex between two mirror boundaries.
Turbulent Taylor vortices have been studied using the low Reynolds number k-w formulation using ELMORE and CFX, a commercial, finite volume CFD code. Grid independent results for three radius ratios tested have explained a turbulent flow transition between turbulent two states. For pre-transition the turbulence production is dominated by the outflowing boundary of the Taylor vortex. As the Reynolds number increases, shear driven turbulence, (due to the rotating cylinder) becomes the dominating factor. The effect of Taylor vortex length on skin friction and vortex strength has been evaluated using ELMORE.
The domain has been extended to that of the full geometry, by implementing ELMORE as a parallel solver, to demonstrate the open end effects. These have allowed a comparison of the pressure with the bubble distributions from the experimental results. The transient start-up problem has been solved using a parallel 2-D DNS approach. Although in 2-D, it clearly shows that Görtler vortices are initially present and evolve into stable turbulent Taylor vortices. Four distinct steps have been identified as this flow develops.
University of Southampton
Batten, William Michael John
97335b46-62ce-4d6f-93aa-bb95d1f86b8a
2002
Batten, William Michael John
97335b46-62ce-4d6f-93aa-bb95d1f86b8a
Batten, William Michael John
(2002)
Numerical predictions and experimental analysis of small clearance ratio Taylor-Couette flows.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
An integrated electrical thruster unit for use with work-class under water vehicles has a gap between two cylinders with the inner one rotating resulting in Taylor-Couette flow. It has a small clearance ratio with low Reynolds number turbulent Taylor vortices. To assess the frictional loss in the gap empirical equations were compared, but these show large discrepancies for the small gaps present in the thruster. From these empirical relations a 2mm gap was chosen for the design of the thruster unit. Published literature indicates that the start-up conditions affect the torque due to different Taylor vortex length and also raises questions about the existence of Görtler-type vortices within the turbulent Taylor vortices.
To analyse the flow an experimental rig was designed and constructed with a dynamically similar clearance ratio with a gap of 10mm and an inner radius of 710mm. The presence of Taylor vortices was clearly demonstrated, using bubbles to visualise the flow. A novel method of analysing the bubbles as a probability spectrum, to measure Taylor vortex length, has been developed. The friction resistance has been measured, demonstrating the empirical equations are approximately correct, from analysis of the power lost in the motor used to drive the rig and dynamometry attached to the outer cylinder.
The laminar flow has been successfully modelled with ELMORE, an in-house finite volume Navier-Stokes code with grid independent solutions. Studies were carried out on the effect of Reynolds number and end boundaries conditions on flow properties. These proved that if the vortex size is that of a critical length then the skin friction was the highest, unless adjacent to the end wall. It was also shown that is was possible to model just one vortex between two mirror boundaries.
Turbulent Taylor vortices have been studied using the low Reynolds number k-w formulation using ELMORE and CFX, a commercial, finite volume CFD code. Grid independent results for three radius ratios tested have explained a turbulent flow transition between turbulent two states. For pre-transition the turbulence production is dominated by the outflowing boundary of the Taylor vortex. As the Reynolds number increases, shear driven turbulence, (due to the rotating cylinder) becomes the dominating factor. The effect of Taylor vortex length on skin friction and vortex strength has been evaluated using ELMORE.
The domain has been extended to that of the full geometry, by implementing ELMORE as a parallel solver, to demonstrate the open end effects. These have allowed a comparison of the pressure with the bubble distributions from the experimental results. The transient start-up problem has been solved using a parallel 2-D DNS approach. Although in 2-D, it clearly shows that Görtler vortices are initially present and evolve into stable turbulent Taylor vortices. Four distinct steps have been identified as this flow develops.
Text
882650.pdf
- Version of Record
More information
Published date: 2002
Identifiers
Local EPrints ID: 464818
URI: http://eprints.soton.ac.uk/id/eprint/464818
PURE UUID: e6515c0b-e8ca-44c5-85f0-7b3f7b570ffc
Catalogue record
Date deposited: 05 Jul 2022 00:03
Last modified: 16 Mar 2024 19:46
Export record
Contributors
Author:
William Michael John Batten
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics