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Thread: H2OMap Sewer: Forcemain Minor Losses

  1. #1

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    H2OMap Sewer: Forcemain Minor Losses

    Does H2OMap Sewer account for these? If so, how? If not, recommendations on accounting for these within the model?

  2. #2
    Senior Member

    Innovyze Employee



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    Post How to Model Manhole Losses

    Hello Tyhopkin,

    This is how losses at manholes are accounted for in H2OMap Sewer

    MANHOLES

    Manholes are points in the network where links join together and where loads enter the network. They are also placed at locations where pipe characteristics change (e.g., diameter and slope). The basic input data required for manholes is:
    • The rim elevation , i.e. the top elevation of the manhole structure
    • The diameter of the manhole structure
    • The baseline load at the manhole

    The manhole diameter and rim elevation parameters are used in the determination of manhole surcharge and flooding. The loads on the system, i.e., wastewater flows collected, accumulated and conveyed by the collection system are assumed to be positive. Manholes can have their load vary with time and different types of loading (e.g., low density residential, medium density residential, high density residential, industrial, commercial, etc.) can be assigned to them. A manhole can also have no loading defined.The results computed for manholes for a simulation are:
    • The base load
    • The total load
    • The overload storage
    • The hydraulic grade

    Two other types of manhole can also be modeled:
    • Junction chambers represent nodes in a pressurized sewer collection system connecting pumps to force mains. No loads can be defined for a junction chamber.
    • Outlets designate facilities where flows exit the collection system. These nodes define the discharge end or the most downstream element of a sewer network. The exit condition can be grouped into four cases as shown below.

    Flow splits (bifurcations) can also be modeled and represent points in the conveyance system where multiple pipes separate flows to different parts of the system. A flow split occurs whenever two or more pipes exit the same manhole. InfoSewer ad H2OMap Sewer provide four practical methods of allocating flows to the downstream (outgoing) pipes:
    • Fixed flow split percentage method - The user specifies the percentage of the total flow in the manhole which is assigned to each of the downstream pipes.
    • Variable flow split percentage method - The user defines Automatic flow split methoda curve representing the percentage of the total flow in the manhole which is assigned to a downstream pipe as a function of the total incoming flow (See CURVE section).
    • Inflow-outflow flow split method - The user supplies an inflow-outflow curve for each of the downstream pipes splitting from a manhole. The curve defines the amount of the incoming flow to be diverted to a downstream pipe. This flow split method is designed to accommodate flow conditions where hydraulic structures such as weirs and dams are used to regulate downstream flows.
    • - InfoSewer/Pro automatically computes the fraction of the total flow in the manhole assigned to each of the downstream (outgoing) pipes based on their invert levels and diameters.

    Note that InfoSewer/Pro checks that the sum of the fractions leaving a manhole equals 100 percent. In case, the sum is less or greater than 100%, InfoSewer/Pro will automatically adjust the flow allocations for the outgoing pipes proportionally to satisfy flow balance. Finally, note that InfoSewer/Pro assumes that a pipe is closed if its flow split percentage is zero.HEADLOSS AT MANHOLESManhole structures can induce backwater effects to their connecting sewer pipes. However, the precise hydraulic description of the flow in manhole structures is complicated because of the complex degree of mixing, separation, turbulence, and energy losses. These losses are commonly estimated as a function of headloss coefficients and are used to calculate hydraulic grade lines for upstream pipes during backwater analysis.The headloss at a sewer manhole is determined based on the exit pipe’s velocity from the following equation:
    image1273.gif

    whereHs = manhole headloss, ft (m)Vexit = exit pipe velocity, ft/s (m/s)g = gravitational acceleration, 32.184 ft/s2 (9.806 m/s2)K = headloss coefficient (unitless).The headloss coefficient, used for estimating headloss through a manhole, depends on the type of manhole and typically ranges from 0.5 to 1.0.

    Regards,
    Robert Dickinson
    PS Please feel free to contact us directly at support@innovyze.com if you have any further questions on this issue. We are always glad to help.
    Last edited by Robert Dickinson; September 22, 2016 at 08:15 AM. Reason: typo

  3. #3

    Join Date
    Oct 2014
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    Thanks for the info, but it does not really answer my question as I was asking about forcemains and minor losses.

  4. #4
    Senior Member

    Innovyze Employee



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    Hi,

    The minor losses are added at the manholes and the losses affect the force main flows. Minor losses cannot be added directly to the force mains. If you do add losses to the loading manholes this will only affect the downstream HGL for the Force Mains. If you want to adjust the Head Loss, hf in the actual force main then you need to change the value of the HW C - you can see the head loss term in either the Attribute Browser or the FM Graphs.

    2016-09-23_1240.png
    Last edited by Robert Dickinson; September 23, 2016 at 09:45 AM. Reason: added image

  5. #5

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    Oct 2014
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    I'm assuming you mean at the "chambers" because they also have a headloss coefficient.

    The headloss coefficient, used for estimating headloss through a manhole, depends on the type of manhole and typically ranges from 0.5 to 1.0.


    Should chambers be inserted at each bend/fitting in order to represent them with a headloss coefficient? Or is this coeffient intended to represent a 'k' value and can be "summed" for specific portions of a forcemain?

  6. #6
    Senior Member

    Innovyze Employee



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    Again this is more of a support thread and should be addressed at support@innovyze.com but here a new other suggestion:
    1. Headloss is entered for Chamber manholes and only affect the Gravity Mains (GM) and the BC of the FM's
    2. Headloss in the FM's is based on the length of the pipe, diameter, HW C and Velocity or Flow.
    3. If you wan to add in minor losses to the FM's then an alternative would be to add an equivalent length of pipe for the minor losses or make the FM longer in the model
    Regards,
    Robert Dickinson

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