Mud Siren Torque and Erosion Analysis - Measurement While Drilling Signal Analysis, Optimization and Design - page 200

200 MWD Signal Analysis, Optimization and Design
Run E. We will retain the 15 o used above, but reduce the thickness of the
downstream lobe from 20 to 5 gridblocks. The 1 in thick lobe becomes 0.25 in
(recent siren advertisements suggest that thin downstream rotors are used in
present tools). Results show some force decrease in the downstream lobe, also
consistent with experiment. Lab results for the upstream lobe are not available.
Run F. In this run, we return to the baseline Run A with square lobes and
no lobe tapering, and a large 0.25 inch gap. In that run, a force range of -19 lbf
to +19 lbf was computed. We now place the siren in an annulus that converges
in area at both walls as the flow moves to the right, with 10 o inclinations at each
wall. The computed force range is -21 lbf to +16 lbf, a noticeable reduction in
the upstream force.