Flow in a rapidly rotating cone‐shaped PCR‐tube

Abstract

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.

Citation

Skote, M., Mårtensson, G.E. and Johansson, A.V. (2011), "Flow in a rapidly rotating cone‐shaped PCR‐tube", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 21 No. 6, pp. 717-735. https://doi.org/10.1108/09615531111148473