"Eaves Gutter Overflow Calculations Spacer Spring Clip"
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