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Flow in a rapidly rotating cone-shaped PCR-tube
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0002-2711-4687
2011 (English)In: International journal of numerical methods for heat & fluid flow, ISSN 0961-5539, Vol. 21, no 6, 717-735 p.Article in journal (Refereed) Published
Abstract [en]

Purpose - A precise and rapid temperature cycling of a small volume of fluid is vital for an effective DNA replication process using the polymerase chain reaction (PCR). The purpose of this paper is to study the velocity and temperature fields inside a rotating PCR-tube during cooling of the enclosed liquid. Design/methodology/approach - The velocity and temperature fields inside a rotating PCR-tube during cooling of the enclosed liquid are studied. By using computational fluid dynamics, the time development of the flow can be investigated in detail. Owing to the rotation, the flow exhibits features which could never arise in a non-rotating system. Findings - An intricate azimuthal boundary layer flow is presented and explained. The inherent problem of stratification of the temperature is discussed, and different methods towards a remedy are presented. By analyzing the governing equations, some properties of the flow observed in the simulations are explained. It is shown that increasing the rate of rotation does not improve temperature homogenization. Research limitations/implications - The simulations were performed for a limited number of temperature boundary conditions, as well as a specific simulation geometry. Practical implications - The analytical and simulation results offer fundamental insight into the physics behind increased DNA duplication. Further simulations offer possible design improvements. Originality/value - While many studies have probed the effects of buoyancy in rotating cylinders and the development of boundary layers in stratified flows in conical containers rotating around their axis of symmetry, little work has been specifically focused on the case where the axis of rotation is normal to the direction of the stratification, which is the case in the present study.

Place, publisher, year, edition, pages
2011. Vol. 21, no 6, 717-735 p.
Keyword [en]
Rotation, Computational fluid mechanics, Coriolis effects, Biomedical flow
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-5624DOI: 10.1108/09615531111148473ISI: 000296602900003Scopus ID: 2-s2.0-79960782001OAI: oai:DiVA.org:kth-5624DiVA: diva2:10052
Funder
Swedish e‐Science Research Center
Note
QC 20100913Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2012-05-24Bibliographically approved
In thesis
1. Analysis of laminar and turbulent flows with turbomachinery, biotechnology and biomechanical applications
Open this publication in new window or tab >>Analysis of laminar and turbulent flows with turbomachinery, biotechnology and biomechanical applications
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The goal of this study was initially to gain a better understanding of the effects of rotation on turbulent flow in ducts. Knowledge concerning the influence of rotation on the structures of turbulence is of fundamental importance in many applications, e.g. centrifugal separators, turbines or cooling channels in rotating machinery, as well as meteorology and oceanography. Rapidly rotating duct flow is studied experimentally with rotation numbers in the interval [ 0, 1] . To achieve this, in combination with relatively high Reynolds numbers (5000 – 30000 based on the hydraulic radius), water was used as the working medium. The influence of the rotation on the pressure drop in the duct was investigated and suitable scalings of this quantity were studied. Due to questions that arose in the experimental study, two numerical studies were initiated. The first study probed the effect of rotation and geometrical configuration on the development length for turbulent flow, while the second comprised a direct numerical simulation of turbulent flow in a rotating duct. It is shown that while system rotation does not have a marked effect on the development length in a plane channel, the development length is substantially shortened in a duct.

Additional systems subject to rotation or curvature effects were studied. The laminar flow of fluid in a rotating PCR-cone was analysed analytically and numerically to understand the increased mixing and temperature homogenization. The flow field in the cone was described and the increased mixing was due to a strong boundary layer flow incited by Coriolis and buoyancy effects. Comparisons of the numerical simulations with experiments yielded good results.

A study to quantify the flow of blood in cerebral malformations using three-dimensional videodensitometry was performed. Data from experiments with an idealized flow phantom, as well clinical pathologies, showed that the proposed methodology in conjunction with clinical injection protocols can yield mean flux data with an error less than 20%. Protocol improvements are proposed.

Place, publisher, year, edition, pages
Stockholm: Mekanik, 2006
Series
Trita-MEK, ISSN 0348-467X ; 2006:06
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-3928 (URN)
Public defence
2006-05-05, Sal F2, Lindstedtsvägen 28, Stockholm, 13:30
Opponent
Supervisors
Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2012-03-21

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Johansson, Arne V.

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