Eaves Gutter Overflow Calculations Spacer Spring Clip by cYevV8B

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									EAVES GUTTER OVERFLOW PRINCIPLES

There is 1 input - all in BOLD RED                                                                                           With rainfall rate of        650      mm/hr and a catchment length
                                                                                                                             (ridge to gutter) of         10.0     metres, the head of water above
METROLL 115 HIGH-FRONT SLOTTED QUAD GUTTER                                                                                   back of gutter is             9.0     mm
Space Spring Clip Version                                                                                                    and above slot line is       24.0     mm.
Flow through a slot as modelled in Manning report                                                                                                                                                    Head over back   9.0    mm
This is the case where a head of water drives water through a set of slots                                                                                                                           Head over slot   24.0   mm



h                   20    mm                   head height above bottom of slot                                                            Back ht            63   mm
g                 9.81    m/sec2                                                                                                                                                                     Slot width       33.0   mm
Cd                0.67                         discharge coefficient (as per Manning report)                                                                                                         Slot height      2.0    mm
a                 33.0    mm                   slot width                                                                                                                                            Slot elevation    48    mm
b                   2.0   mm                   slot height                                                                                                                                           Space between     58    mm
D                   58    mm                   space between slots
BH                  63    mm                   gutter back height
SE                48.0    mm                   slot elevation above base
v                0.626    m/s                  stream velocity (only a function of head)                                                   Gap to fascia
FR               0.028    l/s                  flow rate per slot                                                                              6.0     mm
FR               0.304    l/s/m                flow rate per metre                 same value as Manning report                            Clip obstruction             40    mm per m

Flow through a slot - revised criteria                                                                                                     NOTE 1
                                                                                                                                           Slots and back gap must retain nominal width
                                                                                                                                           and remain unblocked for calculations to be valid.
h                 24.0    mm                   head height above centre of slot                                                            NOTE 2
g                 9.81    m/sec2                                                                                                           Gutter deflection when full will increase its
Cd                0.61                         discharge coefficient (per Fig 46 in Rouse: Elementary Mechanics of Fluids)                 capacity and increase the head over slot.
a                   33    mm                   slot width                                                                                  NOTE 3
b                    2    mm                   slot height                                                                                 Gap flow behind gutter has been modelled as a slot
D                   58    mm                   gap between slots                                                                           for h >= b and as a sharp-edged weir when h < b
b/2h              0.04                         look up Cd based on this value                                                              NOTE 4
                                                                                                                                           Gutter is assumed to be level
v                0.686 m/s                     stream velocity
q                0.028 l/s                     flow rate per slot
q                0.304 l/s/m                   flow rate per metre                               17%     through slots



Flow through back gap - modelled as continuous slot (with Cd adjustment when head is less than gap)


h                   9.0   mm                   head height above back of gutter
g                  9.81   m/sec2
Cd                 0.62                        discharge coefficient (per Fig 46 in Rouse: Elementary Mechanics of Fluids)
a                 1000    mm                   slot width
b                   6.0   mm                   back gap = "slot" height
D                    40   mm                   gap between "slots" (used to represent obstruction by clips)
b/2h               0.33                        look up Cd based on this value

q              0.00156 m3/s                    uses weir equation when h<b and slot equation for larger h
q                1.563 l/s                     flow rate per slot
q                1.503 l/s/m                   flow rate per metre - adjusted for clips        83% through gap


Total flow through slots and back gap

Q                1.807    l/s/m                total discharge rate                             100%
=              0.00181    m3/s/m
=                  6.50   m3/hr/m
=                  6.50   m2/hr
L                  10.0   m                    catchment length
RR               0.650    m/hr
=                  650 mm/hr                   rainfall rate giving above flows with entered catchment
EAVES GUTTER OVERFLOW PRINCIPLES

CALCULATIONS FOR WEIR FLOW

Flow over a weir
This is the case where a head of water drives flow over a sharp vertical edge
This edge could be the top of the gutter back, or the front gutter roll.



RR                   200 mm/hr                    rainfall rate looked up on chart
RR            5.55556E-05 m/s                     RR converted to SI units
L                       5m                        catchment length
w                      57 mm                      height of safe weir (from base of gutter) (Stramit 57 mm)
h                     1.6 mm                      water head above weir (used to estimate Cd)
Cd                   0.60                         discharge coefficient - wide weir (multiple iterations) - function of weir hei
g                    9.81 m/sec2

h                 0.00157 m                       rearranged discharge equation to give h as function of rainfall and catchme

h                      1.6 mm                     change cell B14 to this value and recalculate
amit 57 mm)

rations) - function of weir height w, head h and physical form


nction of rainfall and catchment length
AS/NZS 3500.3 Table G1

        As Published

        Average inflow                       l/s/m   0.2   0.4   0.6
        Height above weir                    mm      18    20    22
        Height above weir   Sloping gutter   mm      12    14    16




        Calculated (PENDING)

        Average inflow                       l/s/m   0.2   0.4   0.6
        Height above weir   Level gutter     mm      18    20    22
        Height above weir   Sloping gutter   mm      12    14    16
0.8   1.0
23    25
17    19




0.8   1.0
23    25
17    19

								
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