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- Increasing the flow rate of our experimental apparatus so that we are generating turbulent flow inside the tube flocculator. While this option may reduce the amount of flocs settling out of suspension, the increase in shear stress introduced by turbulence could disrupt the formation of flocs. First, we must determine if our current apparatus can generate turbulent pipe flow. Additional pump heads and/or increasing tubing size may be required to get the Reynolds number of the flow high enough to transition into turbulence. Once the ability to generate turbulent flow is achieved, we must evaluate whether we can achieve good flocculation. An additional challenge of operating in the turbulent regime is that shear, strain and G are now not so easily calculated and one can no longer assume these parameters are constant throughout the flocculator. On the other hand, the effectiveness of laminar flow to generate flocs has also been called into question. In a perfectly straight Poiseuille flow, the parabolic velocity profile requires that the gradient of velocity to be zero at the centerline, which means that if a particle were to travel along the centerline, it will have limited opportunity to collide with other particles because there is no gradient at the centerline. By having a coiled tube flocculator, this issue may have been ameliorated by the secondary flows generated by the centrifugal forces that disrupt the symmetry of the flow. This option, however, is the easiest option to undertake and should be explored first.
- Minimizing the amount of horizontally oriented tube sections should minimize settling because there will be no wall against which flocs could settle onto. This, however, would entail orienting the tube straight up and down, which would limit the length of our flocculator. If the tube were wrapped around like a long racetrack-with the bends occurring at the top and bottom of the loops being much shorter than the vertical sides, we may be able to see some improvements. While this setup may reduce floc settling out of the flow, it brings into question whether laminar straight pipe flow is the right regime to study flocculation. As mentioned earlier, there are some theoretical arguments against flocculating in Poiseuille flow. This problem could be aided by the addition of some kinks in the pipe so that minor losses can introduce horizontal velocity components which will transport particles to different radial locations. More calculations are needed to evaluate this option.
- A third and most difficult option would be to rotate the entire flocculator in such a way that the direction of gravitational acceleration will always be transient with respect to the centerline axis of the tube. Since it is gravity that pulls floc out of the flow and down onto the wall oriented below the centerline of the pipe, by varying the angle of the vector of gravitational acceleration, sedimentation might be avoided. This option is the most complicated and hardest to implement simply because it requires new mechanical equipment and non-trivial design calculations.