At 5:49 PM 10/19/4, RC Macaulay wrote: >Observation. > >A 100 MGD wastewater treatment plant effluent channel 14 ft wide, flow 2+ fps,
Some off the top of the head comments follow. OK, so about 154 ft^2/sec, thus channel is running about 5.5 feet deep. > 30 degree sharp bend in channel. A push type feeder mixer installed >immediately downstream of the bend. Feeding 15% hypo solution. Random >visible vertical surface vortexes can be seen forming and dissipating at >the bend. > >The mixer 15 hp motor has superb monitoring,, voltage, amps, phase etc. >Normal running amps 16, low amp trip set at 15 amps. The monitor stores >power events. > >Corrected for voltage fluctuations from the electric power system, we >experience periodic increases in amperage load and more strangely, >decreases in amperage below 15 amps for a period. It interests us in that >the rise in amps is a momentary event whereas the drop in amps is a >sustained ( a longer time interval) event. Just a wild guess, but current draw changes could be caused by change of vortex mode, horizontal to vertical. The channel is wider than deep so a vertical vortex would flow slower than a horizontal one. The higher the speed the higher the resistance. A horizontal vortex would take more energy to drive. Due to the bend a vertical vertex would be the normal mode, a much more common mode, and, depending on which side of the channel the pump is located, the natural flow of the pump can be aided by the normal flow. > >We believe these event are caused by a submerged " horizontal" vortex >introduced at the face of the high speed propeller( although the prop is >pushing against the flow) enhanced by the sharp bend in the channel. We >have observed horizontal vortexes form in a glass test tank and "ponder" >the possibility. > >Some studies of porpoise motion and speed have considered the possibility >of their use of vortexes. They cannot be seen unless air is inducted to >trace the pattern.. but... >how much do we fail to see because, like water, the picture is too clear ? > >Richard Initial "instrumentation" to investigate might be fairly cheap. All you need is a piece of transparent tubing attached to a pole, with a piece of pipe on the end of the pole bent into the current flow, like a Pitot tube. This could then indicate relative pressure wherever placed, by the water column. Simply moving such a thing around by hand might give enough info., but ideally a set of 4 would be used, a pair above and below the pump outlet, and a pair to the sides. Relative pressure would then indicate vortex flow direction. Just food for thought. Regards, Horace Heffner
