Manhole Elevations in InfoSWMM and SWMM 5

Subject: Manhole Elevations in InfoSWMM and SWMM 5
Starting from the bottom of the manhole you have these regions of computational interest:
1. Manhole Invert to the lowest link invert – the node continuity equation is used with the area of the manhole being the default surface area of a manhole,
2. Lowest Link Invert to the Highest Link Crown Elevation – the node continuity equation is used with surface of the node being normally half of the surface area of the incoming and outgoing links,
3. Highest Manhole Pipe Crown Elevation to Manhole Rim Elevation – the node surcharge algorithm in which the surface area of the manhole is not used and the surcharge depth is iterated until the inflow and the outflows of the node are in balance,
4. The region above the Manhole Rim Elevation which can use one of four options to calculate the depth and/or flow out of or into the manhole:

1. No Surcharge Depth is entered and No Ponding area is used – the excess water into the manhole is lost to the network and shows up as internal outflow in the continuity tables,

2. A Ponding Area is used and the excess flow will pond on the surface of the manhole and later go back down into the conveyance pipes.

3. A Surcharge Depth is used and the depth will continue to be calculated using the node surcharge algorithm in which the surface area of the manhole is not used and the surcharge depth is iterated until the inflow and the outflows of the node are in balance,

4. A Dual Drainage system is simulated and the excess flow of the manhole is simulated in the street gutters or the actual street,

5. You use a 1D/2D linkage between the 1D manhole and 1D links to a 2D Mesh and simulate the flow out and the flow into the manhole using a bottom outlet orifice that switches automatically between weir and orifice flow based on the depth on top of the manhole.

Drainage Wells or a Vertical Exfiltration Trench

Subject: Drainage Wells or a Vertical Exfiltration Trench in InfoSWMM
Note, this is just one way to model an Exfiltration Trench. The source for the image below is Rice Creek Watershed.
You can make a storage node to simulate the trench with the following characteristics:
· Functional or Shape Curve to describe the shape of the trench,
· Infiltration parameters to simulate the infiltration flow out of the bottom or sides of the trench,

Step 1: Define the shape and geometrical characteristics of the Infiltration Trench

Step 2: Define the soil infiltration characteristics of the trench

Step 3: Run the simulation. The Storage Volume Summary tells you the volume infiltrated and the average outflow.

Step 4: Output Manager will also show the infiltration outflow, the depth and the volume of the infiltration/storage node.

Step 5: Infiltration losses out the side and bottom of the orifice.

Drainage Wells or a Vertical Exfiltration Trench in InfoSWMM by dickinsonre Subject:  Drainage Wells or a Vertical Exfiltration Trench in InfoSWMM Note, this is just one way to model an Exfiltration Trench.  The source for the image below is Rice Creek Watershed.  You can make a storage node to simulate the trench with the following characteristics: ·         Functional or Shape Curve to describe the shape of the trench, ·         Infiltration parameters to simulate the infiltration flow out of the bottom or sides of the trench, Step 1:  Define the shape and geometrical characteristics of the Infiltration Trench Step 2: Define the soil infiltration characteristics of the trench Step 3:  Run the simulation.  The Storage Volume Summary tells you the volume infiltrated and the average outflow. Step 4:  Output Manager will also show the infiltration  outflow, the depth and the volume of the infiltration/storage node. Step 4:    Infiltration losses out the side and bottom of the orifice. via Blogger http://www.swmm5.net/2013/07/drainage-wells-or-vertical-exfiltration.html

Adding New View Variables To the SWMM 5 Delphi and C Code

Subject: Adding New View Variables To SWMM 5 for Villemonte Correction for Downstream Submergence. A simple seven step procedure to modify the SWMM 5 GUI Delphi Code and the SWMM 5 C code.

Step 1: Add a new View Variable to the SWMM 5 GUI Delphi code UGLOBAL.PAS

You need to add a new variable name (LINKVILLEMONTE) and increase the index number of LINKVIEWS

LINKVILLEMONTE = 48; //Output // (5.0.022 - RED)

LINKQUAL = 49; //Output // (5.0.022 - RED)

LINKVIEWS = 48; //Max. display variable index // (5.0.022 - RED)

Step 2: Add a new BaseLinkUnits description to the SWMM 5 GUI Delphi code UGLOBAL.PAS

('',''), // Villemonte Correction // (5.0.022 - RED)

('mg/L','mg/L')); // Quality

Step 3: Add a new Link View Variable SourceIndex description to the SWMM 5 GUI Delphi code Viewvars.txt

(Name: 'Villemonte Correction';

SourceIndex: 43;

DefIntervals: (25,50,75,100)),

(Name:'Quality';

SourceIndex: 44;

DefIntervals:(0.25,0.5,0.75,1.0))

);

Step 4: Add a new Link View Variable LINK_VILLEMONTE to the SWMM 5 C code in enums.h

You also need to increase the number of Link Results in enums.h for the increased number of view variables

#define MAX_LINK_RESULTS 45 // (5.0.022 - RED)

LINK_VILLEMONTE, // Villemonte Correction // (5.0.022 - RED)

LINK_QUAL}; // concentration of each pollutant

Step 5: Add a new variable to objects.h for the structure Tlink to remember the Villemonte correction at each iteration for each Weir and Orifice

double Villemonte; //(5.0.022 - RED)

} TLink;

Step 6: In the SWMM 5 LINK.C code in procedure weir_getInflow save the current iteration value of the Villemonte correction to the new structure variable

// --- apply Villemonte eqn. to correct for submergence

Link[j].Villemonte = 1.0; //(5.0.022 - RED)

Link[j].head = head; //(5.0.022 - RED)

if ( h2 > hcrest )

{

ratio = (h2 - hcrest) / (h1 - hcrest);

q1 *= pow( (1.0 - pow(ratio, weirPower[Weir[k].type])), 0.385);

if ( q2 > 0.0 )

q2 *= pow( (1.0 - pow(ratio, weirPower[VNOTCH_WEIR])), 0.385);

Link[j].Villemonte = pow( (1.0 - pow(ratio, weirPower[Weir[k].type])), 0.385); //(5.0.022 - RED)

}

Step 7: Save the value of the saved Villemonte correction in LINK.C in the procedure link_getResults so it can be read and seen in the Delphi interface

x[LINK_VILLEMONTE] = (float)Link[j].Villemonte; // (5.0.022 - RED)

Bottom and Side Outlet Orifices in SWMM 5

Note: The main difference between an Bottom and Side Outlet orifice at the same offset elevation and the same diameter is the depth at which the flow in the orifice will switch between weir flow and orifice flow. The Side Outlet orifice has Weir flow until the Orifice is full but the Bottom Orifice has Weir flow until the Critical Height which is usually shorter than the maximum depth of the orifice.

For a circular orifice the Critical Height is:

Critical Height = Orifice Discharge Coefficient / 0.414 * Orifice Opening / 4

For a rectangular orifice the Critical Height is:

Critical Height = Orifice Discharge Coefficient / 0.414 * (Orifice Opening*Width) / (2.0*(Orifice Opening+Width))

Orifice and Weir flow calculations

Note: Orifice and Weir Flow Computations

The orifice flow calculation proceeds as follows:

1. Initially and whenever the setting (i.e., the fraction opened) changes, flow coefficients for both orifice and weir behavior are computed as follows:

a. For side orifices:

Define Hcrit = h/2 where h is the opening height.

b. For bottom orifices:

i. For a circular orifice, compute area over length (i.e., circumference) as AL = h /4.

ii. For a rectangular orifice compute AL = h*w/(2*(h+w)) where w is the opening width.

iii. Compute Hcrit = Cd*AL/0.414 where Cd is the orifice discharge coefficient.

At step 1b, the critical head for the bottom orifice, where orifice flow turns into weir flow, is found by equating the result of the orifice equation to that of the weir equation

Cd*Area*sqrt(2g)*sqrt(Hcrit) = Cw*Length*sqrt(Hcrit)*Hcrit or

Hcrit = (Cd * Area) / (Cw/sqrt(2g) * Length) The value of Cw/sqrt(2g) for a sharp crested weir is 0.414.

c. Compute the flow coefficients (where A is the area of the opening):

Corif = A*sqrt(2g)*Cd

Cweir = A*sqrt(2g)*Cd*sqrt(Hcrit)

2. During flow routing, compute the degree of inlet submergence (f) and head (H) at the current time step:

a. Define:

H1 = upstream head (from node with higher head),

H2 = downstream head (from node with lower head) ,

Hcrest = elevation of bottom of opening,

Hcrown = elevation of top of opening,

Hmidpt = elevation of midpoint of opening

b. For side orifices:

f = min{1.0, (H1 - Hcrest) / (Hcrown - Hcrest)}

if f < 1.0 then H = H1 - Hcrest,

else if H2 < Hmidpt then H = H1 - Hmidpt

else H = H1 - H2

c. For bottom orifices:

if H2 > Hcrest then H = H1 - H2

else H = H1 - Hcrest

f = min{1.0, H/Hcrit}

3. Compute the flow through the orifice (Q):

if f < 1.0 then Q = Cweir*f^1.5

else Q = Corif*sqrt(H)

4: Villemonte correction

If f < 1.0 and H2 > Hcrest then:

r = (H2 - Hcrest) / (H1 - Hcrest)

Q = Q * (1 - r^1.5)^0.385

Weir Flow Computations

1. Weir head calculations

h1 = Upstream Node Depth + Upstream Invert Elevation

h2 = Downstream Node Depth + Downstream Invert Elevation

If h2 is greater than h1 then the flow is reversed and h2 = h1 and h1 = h2

Weir Crest = Upstream Node Invert Elevation + Weir Offset Depth

Head = h1 – Weir Crest

2. Center Weir flow for Transverse Weirs

Q = Cw * Weir Length * Head^3/2

3. Center Weir flow for Side Flow Weirs

Weir behaves as a transverse weir under reverse flow

Q = Cw * Weir Length * Head^3/2

And under normal flow

Q = Cw * Weir Length * Head^5/3

4. Center Weir flow for V Notch Weirs

Q = Cw * Weir Slope * Head^5/2

Orifice Critical Depth for Separating Weir Flow from Orifice Flow for Bottom Outlet Orifices in SWMM5

Note: Orifice Critical Depth for Separating Weir Flow from Orifice Flow for Bottom Outlet Orifices
The Critical height is the opening where weir flow turns into orifice flow. It equals (Co/Cw)*(Area/Length) where Co is the orifice coeff., Cw is the weir coeff/sqrt(2g), Area is the area of the opening, and Length = circumference of the opening. For a basic sharp crested weir, Cw = 0.414. All of the units are based on the internal SWMM 5 units of American Standard.
For a circular orifice the Critical Height is:
Critical Height = Orifice Discharge Coefficient / 0.414 * Orifice Opening / 4
For a rectangular orifice the Critical Height is:
Critical Height = Orifice Discharge Coefficient / 0.414 * (Orifice Opening*Width) / (2.0*(Orifice Opening+Width))
The Orifice Critical Depth changes dynamically as the orifice is opening and closing for a bottom outlet orifice. The critical depth separating the orifice weir flow from orifice flow for a side outlet orifice is the height of the orifice.

Orifice Critical Depth for Separating Weir Flow from Orifice Flow for Bottom Outlet Orifices in SWMM 5 by dickinsonre Note:  Orifice Critical Depth for Separating Weir Flow from Orifice Flow for Bottom Outlet Orifices The Critical height is the opening where weir flow turns into orifice flow. It equals (Co/Cw)*(Area/Length) where Co is the orifice coeff., Cw is the weir coeff/sqrt(2g), Area is the area of the opening, and Length = circumference of the opening. For a basic sharp crested weir, Cw = 0.414.  All of the units are based on the internal SWMM 5 units of American Standard. For a circular orifice the Critical Height is: Critical Height = Orifice Discharge Coefficient / 0.414 * Orifice Opening / 4 For a rectangular orifice the Critical Height is: Critical Height = Orifice Discharge Coefficient / 0.414 * (Orifice Opening*Width) / (2.0*(Orifice Opening+Width)) The Orifice Critical Depth changes dynamically as the orifice is opening and closing for a bottom outlet orifice.  The critical depth separating the orifice weir flow from orifice flow for a side outlet orifice is the height of the orifice. via Blogger http://www.swmm5.net/2013/07/orifice-critical-depth-for-separating.html

Opening and Closing an Orifice with a Time Series Setting

Opening and Closing an Orifice with a Time series Setting

An example of RTC rules in SWMM 5

Orifice Open and Close Speed and the Target Setting in SWMM 5

Orifice Open and Close Speed and the Target Setting
In SWMM 5 there is an orifice parameter called setting which opens or closes the orifice opening by modifying the depth of the orifice. The setting is based either on a RTC rule of the orifice or the Flap Gate condition of the orifice and can be between 0 and 1. Closed is 0; Open is 1. The difference is that the target setting is what the setting should be based on the condition of the Flap Gate or the RTC Rules and the setting is the value actually used in the model.
The open and close speed of the orifice modifies the orifice setting by changing the orifice setting based on the open and closing speed using the equation:
New Orifice Setting = Old Orifice Setting + (Target Setting – Orifice Setting) * Time Step / Orifice Open and Close Speed
If your target setting and the current orifice setting are both 1 or 0 then the orifice Open and Close option does not change the orifice setting. New Setting equals Old Setting in that case. If the target and setting are out of phase then the Open and Close Option will function correctly. For example, if the Open and Close Speed is 1 hour then the orifice setting will open and close in a one hour period. The table shown below shows how the orifice setting changes as a function of the speed and the difference between the target and orifice settings. The setting starts out open but the target says closed – the orifice then closes over a 1 hour period. At one hour the target setting is 1 and the orifice will then open over a one hour period.
Table - Link OR1@82309b-15009b
Setting Target
Days Hours
0 00:00:00 1.00 0.00
0 00:15:00 0.74 0.00
0 00:30:00 0.50 0.00
0 00:45:00 0.25 0.00
0 01:00:00 0.00 0.00
0 01:15:00 0.25 1.00
0 01:30:00 0.50 1.00
0 01:45:00 0.75 1.00
0 02:00:00 1.00 1.00
0 02:15:00 0.75 0.00
0 02:30:00 0.50 0.00
0 02:45:00 0.25 0.00
0 03:00:00 0.00 0.00
0 03:15:00 0.00 0.00
0 03:30:00 0.00 0.00
0 03:45:00 0.00 0.00

Example rule for the opening and closing of the orifice

Here is an example Real Time Control (RTC) rule for the opening and closing of an orifice.
RULE Orifice1
IF SIMULATION CLOCKTIME >= 01:00:00
AND SIMULATION CLOCKTIME <= 2:00:00
THEN ORIFICE OR1@82309b-15009b SETTING = 1
ELSE ORIFICE OR1@82309b-15009b SETTING = 0
PRIORITY 1
; Opens up the orifice at hour 1 of the simulation