| 112 | | The siphon rig consists of 12 siphon tubes, each with a nominal internal diameter of 1.6 mm (3.2. mm external diameter), and 15 m in length. The siphons are held in place by a plastic holder which is in turn connected to a rod attached to the channel. The siphon rig is positioned 80 mm downstream of the inflection downstream of bend 2, offset laterally 78 mm off-axis from the position of the UVP (on the right hand side as looking downstream). The siphons are positioned at heights of 10, 25, 50, 75, 100, 125, 150, 175, 200, 250, 350 and 450 mm above the bed. The siphon tubes are connected to a 12 head peristaltic pump. Samples are taken when the traverse (with ADVs and conductivity probe) is positioned upstream measuring the straight section. Samples are collected in an array of 12 plastic containers over a 60 second period, starting at 5, 10, 15, 20, 25, 30 and 35 minutes into the experiment (the start of the experiment is defined as that point where the input is steady). Samples are subsequently measured for conductivity using an Anton Paar DMA35 Portable Density Meter. |
| | 112 | The siphon rig consists of 12 siphon tubes, each with a nominal internal diameter of 1.6 mm (3.2 mm external diameter), and 15 m in length. The siphons are held in place in the channel section by a plastic holder which is in turn connected to a rod attached to the channel. The siphon rig is positioned 80 mm downstream of the inflection downstream of bend 2, offset laterally 78 mm off-axis from the position of the UVP (on the right hand side as looking downstream). The siphons were initially positioned at heights of 7, 16, 26, 56, 86, 116, 146, 176, 206, 236, 266 and 306 mm from the bed for the initial test experiments. For the main experiments the siphons were positioned at heights of 10, 25, 50, 75, 100, 125, 150, 175, 200, 250, 350 and 450 mm above the bed. The siphon tubes are connected to a 12 head Watson Marlow 2058 peristaltic pump which is run at the highest setting of 90 rpm. Samples are taken when the traverse (with ADVs and conductivity probe) is positioned upstream measuring the straight section. Samples are collected in an array of 12 plastic containers over a 60 second period, starting at 5, 10, 15, 20, 25, 30 and 35 minutes into the experiment (the start of the experiment is defined as that point where the input is steady – see Section 3.2). The transit time of fluid moving through the siphons was measured using dye and was found to be 1 min and 50 seconds, thus we are actually sampling the flow at 3 min 10 s, 8 min 10 s, 13 min 10 s, 18 min 10 s, 23 min 10 s, 28 min 10 s, and 33 min 10 s (for the main experiments). Each plastic container was 3 cm in diameter and were placed inside a plastic template consisting of 12 3.2 cm diameter holes. Average fill depth of the containers in the 1 minute measurement period was 2.6 cm. Samples were subsequently measured for conductivity using an Anton Paar DMA35 Portable Density Meter. |
