Stormwater Management Model (SWMM) Information for watershed water quality, hydrology and hydraulics modelers (Note this Blog is not associated with the EPA). You will find Blog Posts and Twitter Embeds on the Subjects of SWMM5, InfoSWMM, InfoSewer, SWMMLive, InfoSWMM SUSTAIN, SWMM4 and SWMM in general.
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Reasons A Pump H-Q Curve may be Different than the Design Curve
Subject: Reasons A Pump H-Q Curve may be Different than the Design Curve
The actual current system H-Q curve may be different than the original system design. Once a plant is commissioned and the plant is put in service, the system head begins to change. In the short term, levels change in the tanks and wells, valves open and close, and filter screens become clogged. As maintenance occurs, pipe schedules are changed, equipment is changed and new equipment is added into the system. In the long term, equipment loses efficiency, scale forms on the internal pipe walls and the plant undergoes expansion and contraction. Even when new, the original calculated system curve may differ from the actual system performance due to the assumptions used in the calculation, such as 10 year old pipe. Any pump change should, therefore, start with the development (confirmation) of the true current pumping system “Head-Capacity” curve, as detailed in the writer’s January 2009 Column on: “Creating an Accurate Pumping System Head-Capacity Curve...“ A field test of the pump total developed head at one or more measured flow rates can help determine the actual (current) pump and system H-Q curves. By developing the true system head-capacity curve, an accurate determination of the current and new pump operating conditions can be established.
From Pump System Hydraulic Design 10.2.4 Determination of Pump Operating Points—Single Pump
The system curve is superimposed over the pump curve; (Fig. 10.6). The pump operating points occur at the intersections of the system curves with the pump curves. It should be observed that the operating point will change with time. As the piping ages and becomes rougher, the system curve will become steeper, and the intersecting point with the pump curve will move to the left. Also, as the impeller wears, the pump curve moves downward. Thus, over a period of time, the output capacity of a pump can decrease significantly. See Fig. 10.7. for a visual depiction of these combined effects
Soffit Level (pipe technology)The top point of the inside open section of a pipe or box conduit. The soffit is the highest point of the internal surface of a pipe or culvert at any cross-section. The soffit is also referred to as the pipe obvert. So it is not quite the Crown of the Pipe. Here is an image I found that hopefully explains it better.
Comment: A really nice water analogy for the field properties Divergence, Curl and Gradient from the Blog Starts With a Bang
....it's pretty mathematically intensive, but what's missing from most textbooks and E&M courses are physical explanations of what the mathematics means. For instance, I've started teaching about fields, and pretty much every textbook out there goes on and on about the properties of fields. They say you can do three things to fields, take the gradient, divergence, orcurl of them. (Are you asleep yet? I'm sorry!) What do these things mean? An easy way to picture it is in terms of water. If you placed a drop of water anywhere on, say,Earth, the magnitude and direction of how it rolls down is the gradient of the Earth's elevation. If you let that drop of water flow, as it goes downhill, it can either spread out or converge to a narrower stream. When we quantify that, that's what the divergence of the field is. And finally, when that water is …
Engine Error NumberDescription ERROR 101: memory allocation error. ERROR 103: cannot solve KW equations for Link ERROR 105: cannot open ODE solver. ERROR 107: cannot compute a valid time step. ERROR 108: ambiguous outlet ID name for Subcatchment