1D Pits: Difference between revisions
Content deleted Content added
No edit summary |
|||
Line 81:
A template for the generation of the UKWIR Inlet Curve can be downloaded from [https://downloads.tuflow.com/Other/Inlet_Spreadsheets/Inlet%20Curve%20Capture%20tool%20v4.xlsx here]. The template determines both Subcritical Head-Discharge and Supercritical Head-Discharge relationships obtained from the Modelling Sewer Inlet Capacity Restrictions Report based on user input values of water depth (in metres). Two sets of curves can be generated, curves based on default parameters, and those based on user-defined parameters.
== Page Under Construction (Section: Spacing of Road Gullies) ==
== Spacing of Road Gullies (BS EN 124 and BS7903) ==
The following section describes the method to determine the spacing of road gratings, according to the [https://new.sthelens.gov.uk/media/330117/5126_ha-102_00.pdf/ Spacing of Road Gullies] guidance ('''BS EN 124''' and '''BS 7903''').
The method depends on the following '''Hydraulic parameters:'''
* Longitudinal gradient, ''S<sub>L</sub>'', along the length of the scheme (expressed as fraction).
* Cross-fall, ''S<sub>c</sub>'' (also expressed as a fraction).
* Manning’s roughness coefficient, ''n''. Usually ''n'' = 0.017 for a conventional road surface. Other values are given in the following '''Table 1'''. (For more details, please see Section: 4.3; p.g.:4/1; Table 1 of the guidance).
'''Table 1:''' Values of Manning's ''n''
<br>[[File:Table1.jpg|450px|]]<br>
* The grating type (P, Q, R, S or T), or the size and angle of kerb inlet.
* The maximum allowable Flow Width (as shown below by ''B'' in m) against the kerb.
<br>[[File:Figures 1 2.jpg|850px|]]<br>
'''A) Use of Tables for determining the flow capacity of gullies and maximum spacings for gully gratings'''<br>
Equations given in Section 5 of the guidance are used for the calculation of the Spacing of Road Gullies. Design Tables have been compiled to present a quick design approach. Tables can be found in Annex C.
Annex C includes Design Tables for the grating types: Types P, Q, R, S and T. The Design Tables C2-C6 in Annex C of the guidance (p.g: C/3-C/12), present the area that can be drained for an intermediate gully and a range of crossfall and gradient of flow widths. For the Design Tables a rainfall intensity of 50mm/h and Manning’s ''n'' = 0.017 are considered.
For ease of access, the Tables C2-C6 (Type P-T) of Annex C, are replicated in the Spacing of Road Gullies file here [Excel File]. Please see, tabs: Type P, Type Q, Type R, Type S and Type T. The Excel file provides tables like the following examples and their corresponding graphs.
<br>[[File:Tables C2-C6 of Annex C.jpg|950px|]]<br>
<br>'''Note:''' a) ''Tables C2 to C6 are for intermediate gullies on a uniform gradient and are not strictly accurate for gradients which vary greatly over short distances.''
b)''The Excel tables also present the flow collection efficiency η of the grating in % (in brackets)''. <br>
Based on Tables and Equations (2), (3) and (4) of the guidance (p.g: 5/1) the Maximum spacings for gully grating can be calculated.
'''B) Calculation of Gully Spacings based on Equations'''
<br>Alternatively, the equations given in Sections 5 of the guidance can be used for the Spacing of Road Gullies, directly. The method requires the calculations of the Flow capacity of the kerb channel and Flow collection efficiency of the gully grating.
*As a first step, a gully grate type: P, Q, R, S or T should be selected. The selection of the grating Type will determine the design value ''G<sub>d</sub>'' (grating parameter) from '''Table 2'''. (For more details, please see Annex B of the guidance; p.g.: B/1.).
'''Table 2:''' Determination of grating type ''G<sub>d</sub>''
<br>[[File:Determination of grating type.jpg|650px|]]<br>
'''Note:''' ''According to the manual: The value of G<sub>d</sub> should be used to calculate the maximum spacing between gullies.''
*Road (longitudinal) gradient (''S<sub>L</sub>''), Crossfall (''S<sub>c</sub>'') and Manning's (''n'') should then be determined. Parameter values can be obtained from '''Table 3'''.
'''Table 3:''' Determination of ''S<sub>L</sub>'', ''S<sub>c</sub>'' and Manning's ''n''
<br>[[File:Table SL SC N Range.jpg|750px|]]<br>
*Further, a Water Depth against the kerb ''H'' (m) range should be provided. (Please note: The depth range can be changed, but the following equations that are used to calculate the flow capacity are only valid up to the kerb height).
*With the above parameters, the calculations of i) The Flow width (''B'' in m), ii) the Cross-sectional area (''A<sub>f</sub>'' in m2), iii) Hydraulic radius (''R'' in m), iv) Flow rate (''Q'' in m3/s) and v) Flow collection efficiency (''ŋ'' (%)) based on the Equations 6-10 which are presented in Section 5 (p.g.:5/2) of the guidance can be completed.
*Finally, the resulting depth-discharge data can be used in the pit inlet curves.<br>
The Spacing of Road Gullies Excel file above includes a calculation tab which can be used for the completion of the calculation process. Based on calculations and Equations (11) and (12) of the guidance (p.g: 5/3) the Maximum spacings for gully grating can be calculated.
'''Key assumption'''<br>
'''Note:''' This method assumes that the route the flow takes around the trap limits the discharge from the gully pot to 10 l/s. This limit is effective in both directions, so any number of negative head on the gully would create -10 l/s flow back up through the gully and flood onto the road. <br>
== How to Translate On-Grade Approach Flow / Pit Capture Flow Curves to Depth / Discharge Curves for use in TUFLOW ==
Line 86 ⟶ 145:
=TUFLOW Model Inputs=
The steps required to represent pit inlet information within a TUFLOW model is
<ol>
<li> Import an empty 1d_nwk GIS file from the TUFLOW file template folder (model\gis\empty).
| |||