Velocity Profiles Through and Over Arrays of Impermeable Cylinders

Abstract

Abstract We study experimentally (through the non-intrusive technique of Magnetic Resonance Imaging - MRI) and computationally (using the Boundary Element Method - BEM) the distribution of fluid velocities across square arrays of uniform cylinders placed inside a Hele-Shaw cell and oriented with their axes perpendicular to the direction of flow. To simulate the presence of gaps between mold walls and preform in liquid composite molding applications, the cylinders are placed in such a way that an open channel, narrow enough to force a significant part of the flow through the array but wider than the distance between individual cylinders, exists in one side of the array. We are interested in the distribution of velocity in these systems and in particular, the distribution of flow between the two regions (that is, the ‘open’ channel and the cylinder array) and in any velocity transitions from the ‘open’ channel to the interior of the array. Both experimental and computational results show that, for the size of cylinders studied, this transition is complete within the first row of cylinders. Thus, we have not been able to detect any transitions from open-channel flow to flow inside the cylinder array; this will require use of larger number of smaller cylinders. Model predictions are in reasonable agreement with measurements; the observed discrepancies point towards stringent design requirements for such flow cells if the obtained information is to be quantitatively useful.