Research in Mechanical Engineering

FLUID DYNAMICS

Staff Involved: A.D. Lucey, T.T. Chandratilleke, I.M. Howard, R. Narayanaswamy

Project Description(s):

Hydrodynamic stability of boundary-layers

Our interests lie in the development and utilisation of novel computational methods to study fluid-flow phenomena. A novel discrete-vortex method has been developed that models disturbances within a known vorticity field, for example, that of a boundary layer. The approach is based upon classical hydrodynamic stability theory with the perturbed part of the flow being found using appropriate computational modelling. The technique holds great promise for modelling and resolving localised disturbances (for example, the development of turbulent spots). Moreover, by a judicious redefinition of the unperturbed mean flow, the nonlinear phases of disturbance evolution can be accurately tracked or by-pass transition can be studied.

Stability of Flow in Curved Channels

The fluid flow through a curved passage is fundamentally different from that in a straight passage because of the secondary flow it generates as a result of the centrifugal body forces acting on fluid elements. These centrifugal forces lead to the appearance of a pair of counter-rotating base secondary vortices in the flow. Beyond a certain critical flow condition, extra pairs of secondary vortices appear at the outer (concave) wall of the flow passage. These are commonly called Dean vortices and cause hydrodynamic flow instability in the base secondary flow. Our programme of research in curved channels examines the secondary flow mechanism and its potential as an enhancement technique for convective heat transfer in channels. Favourable heat transfer characteristics of secondary flows are harnessed in developing compact and efficient heat exchangers for heat recovery applications.

Measurement of slurry flow

This industrially sponsored project seeks to develop a robust (and portable) ultrasonic system for the measurement of slurry flows in pipes. A test rig has been developed and preliminary investigations carried out using ultrasonic doppler transducers to ascertain typical resonant frequencies and bandwidths. Of interest are the effects of particle concentrations, sizes, flow velocities, etc, on the doppler frequency shifts from the transducers, and also the effectiveness of gating algorithms to ascertain the velocity profiles within typical pipe diameters.

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