Drainage of a Water Tank with Pipe Outlet Loaded by a Passive Rotor

The optimal design of pipe outlets is an essential objective for many engineering projects. For the first time, this paper reports the results of a laboratory investigation on the effect of using a passive rotor (added at the pipe outlet) on the outlet performance. Different sizes and numbers of blades of rotors were considered. Through the Tracker software package, video and image processing techniques were applied to capture the temporal variations of the tank water depth and the passive rotor’s angular speed. In addition, a normalized average drainage rate (NADR) parameter is defined to quantify the changes in the tank drainage rate as a result of passive rotor utilization. It is noted that adding a 4-bladed symmetric passive rotor will increase NADR by up to 9.0%. The study also shows that the highest increase in NADR is attained when the rotor diameter size is approximately 1.73 times the pipe outlet’s diameter for the case of symmetric 4-blade rotors, and the corresponding average tip rotor speed ratio is 1.65. It is also found that using an asymmetric 3-blade rotor has a negative impact on the NADR due to the significant perturbation produced by the rotor asymmetry.

Impairing pipe-to-stream connectivity in a heavily degraded blanket bog: the results of a pipe outlet blocking trial

<p>As part of the EU-funded MoorLIFE2020 project, we assessed the impact of pipe blocking on the hydrological responses at pipe and stream level in a heavily degraded blanket bog in the Peak District of northern England. The study catchment, Upper North Grain, has a blanket peat cover up to four meters thick at places, with a branching network of deep gullies that incise into the bedrock. Earlier survey work has shown piping to be ubiquitous to the site, with 346 pipe outlets found and a mean frequency of 22.8 km<sup>-1</sup> gully bank. Topographic position was an important control on the size and depth of pipe outlets. Pipe outlets on streambanks with signs of headward retreat (head pipes) were significantly larger and closer to the peat surface compared to pipe outlets that issued onto uniform streambank edges (edge pipes). In the context of peatland restoration, managers are keen to understand how these pipes contribute to hydrological responses of streams and associated export of fluvial carbon borne away in stream waters. However, little is known about pipe-to-stream connectivity and whether blocking methods used to impede flow in open ditch networks and gullies also work on pipe networks. Results will be presented on a before-after-control-intervention experiment in which we investigated: 1) whether impeding drainage from pipe networks alters the streamflow response at the catchment outlet; 2) how such intervention affects the hydrological functioning of the pipe network and the surrounding peat; 3) the scale of fluxes of particulate organic carbon (POC) and dissolved organic carbon (DOC) from a head pipe before and after pipe outlet blocking; and 4) whether pipe outlet blocking alters DOC and POC export in streams. Four blocking methods were trialed: peat-plugs, peat and stone, wooden planks, and plastic pilling. Results show that pipe outlet blocking led to new pipe outlets appearing or seepage around blocks within 90 days of blocking. Over a period of 17 months, four individual pipe outlets (2 head and 2 edge) produced 11.3 % of streamflow. Head pipes produced significantly larger peak flows and storm contributions to streamflow compared to edge pipes. A distinctive distance-decay effect of the water table around pipe outlets was observed, with deeper water tables around the outlets of edge pipes. To avoid further erosion in gully edge zones, we propose that future pipe blocking efforts prioritize increasing the residence time of pipe water by forming surface storage higher up in the pipe network. Further results will be presented from ongoing analyses of the effect of pipe blocking on the export of particulate and dissolved organic carbon from pipes and streams.</p>

New insights on controls of piping distribution in degraded blanket bog

<p>As part of the EU-funded MoorLIFE2020 project, which examines strategies to restore degraded blanket bog in the Peak District of northern England, we investigated natural soil pipes. These pipes are a cause of concern to peatland restoration practitioners who are unsure whether to block them to reduce erosion and flood risk when conducting restoration work. Soil pipes often occur in complex networks with varying channel sizes, undulating through the soil profile. Their prevalence is often linked to controls such as topographic location, slope, aspect, vegetation cover, climate, and properties of the surrounding soil. Such relationships are poorly understood for degraded blanket bog. A before-after-control treatment study was designed to examine the effects of pipe blocking on fluvial carbon removal and streamflow in Upper North Grain (UNG), a small headwater catchment located between 490 m and 541 m above sea level. The catchment has a blanket peat cover up to four meters thick at places, with a branching network of deep gullies that incise into the bedrock. This experimental design was envisaged to address the following hypotheses: (i) the severity of degradation of UNG is a dominant control on pipe density; (ii) blocking of pipe outlets impairs pipe-to-stream connectivity. Our results point towards a rejection of both hypotheses. An initial field survey used to locate and characterize pipe outlets, resulted in 353 individual outlet recordings with a density of 13.79 per km of surveyed gully bank. Southeast, south, southwest and west-facing gully banks accounted for more than 75% of identified pipe outlets. The experimental design compares water and aquatic carbon fluxes in two streams - in one catchment the active pipe outlets (n=25) were blocked by closing off the void behind the pipe outlet with peat and stones, wooden screens or plastic pilling, while in the other catchment the pipes were left open. Areas on the gully bank around original outlets were photographed every two weeks. This analysis showed that within the first month after blocking, all treated pipes had formed bypass routes around the block and initiated new pipe outlets. New outlets were found both above and below the original pipe outlet at distances up to 1 meter from the original pipe outlet regardless of bank aspect, suggesting the networks behind a pipe outlet to be a porous system that connects in both vertical and horizontal directions when issuing onto gully banks. Further results will be presented from the ongoing monitoring showing effects of pipe blocking on streamflow storm responses and the export of particulate and dissolved organic carbon from pipes and streams.</p>

Numerical and Analytical Calculation of Flow During Steam Blowing

In the paper results are described of numerical simulations of the flow during the steam blowing between the boiler drum and the outlet to the atmosphere. Numerical flow simulations are compared to the analytical approach that best describes the flow during the blowing, i.e. the Fanno flow. The proposed methodology of analytical calculation can be, with a reasonable deviation from reality, used in control of velocity and flow in the pipe outlet cross-section.