SWMM5, InfoSWMM

Keep and Dampen options and their effect on the four main terms of the St Venant equation

Note: The Keep and Dampen options and their effect on the four main terms of the St Venant equation.

The four terms are are used in the new flow for a time step of Qnew:

Qnew = (Qold – dq2 + dq3 + dq4) / ( 1 + dq1)

when the force main or gravity main is full dq3 and dq4 are zero and Qnew = (Qold – dq2) / ( 1 + dq1)

The dq4 term in dynamic.c uses the area upstream (a1) and area downstream (a2), the midpoint velocity, the sigma factor (a function of the link Froude number), the link length and the time step or

dq4 = Time Step * Velocity * Velocity * (a2 – a1) / Link Length * Sigma

where Sigma is a function of the Froude Number and the Keep, Dampen and Ignore Inertial Term Options. Keep sets Sigma to 1 always and Dampen set Sigma based on the Froude number, Ignore sets Sigma to 0 all of the time during the simulation

the dq3 term in dynamic.c uses the current midpoint area (a function of the midpoint depth), the sigma factor and the midpoint velocity.

dq3 = 2 * Velocity * ( Amid(current iteration) – Amid (last time step) * Sigma

dq1 = Time Step * RoughFactor / Rwtd^1.333 * |Velocity|

The weighted area (Awtd) is used in the dq2 term of the St. Venant equation:

dq2 = Time Step * Awtd * (Head Downstream – Head Upstream) / Link Length or

dq2 = Time Step * Awtd * (Head Downstream – Head Upstream) / Link Length

Normally, dq1 (Friction Loss / Maroon in the Graph) balances dq2 (Water Surface Slope Term or Green in the Graph) but often for links with a large difference between upstream and downstream depths dq4 (Red in the Graph) can have a significant value. If dq4 or dq3 are important then the depth of water to increases to pass the same flow using the Keep option over the Ignore. If you have a link with a Froude number near or over 1.0 (Supercritical) then using Keep or Dampen for the Options may result in depth differences. The effect of Keep is to increase the “loss” terms in the St Venant Equation. The effect of Dampen and Ignore is to decrease the sum of the “loss” terms in the St. Venant Solution and lower the simulated depth.

Rooftop gardens could solve Singapore's flooding problem

Rooftop gardens could solve Singapore’s flooding problem

By Tyler Falk | January 18, 2012, 9:09 AM PST

From SmartPlanet

In the last two years, rapid urbanization and changing weather patterns have lead to major flash floods in Singapore.

“[It] can be safely presumed that the weather patterns in Singapore have changed,” said Singapore’s Minister for the Environment and Water Resources last year after a flash flood where in one day Singapore received 77 percent of the amount of rainfall that usually falls in June. “It is very likely that our drainage systems will have to be redesigned to cope with such intense flashes.”

Singapore convened a panel to come up with the best options for dealing with flash floods and stormwater runoff. Their suggestion? Not an overhaul of the drainage system, but rooftop gardens.

Big infrastructure projects are costly and take time to replace. And while the upgrading the drainage system is likely necessary, the panel suggests a quick fix to Singapore: require rooftop gardens on all new and retrofitted buildings. Rooftop gardens don’t just add beauty to the city, they can also play a big role in mitigating floods by reducing and slowing stormwater runoff and filtering pollutants.

But it’s not just rooftop gardens, Singapore’s Today reports:

These measures are to be complemented with diversion canals, storage tanks along “pathways” of drains, drain capacity improvements, and finally, flood barriers, raised platform levels - some of which is already being done, but “could be carried further”, noted Prof Balmforth.

The panel also suggested storage tanks, rain gardens, and porous pavement.

Photo: HenryLeongHimWoh

/Flickr

Urbanisation has led to increase in storm water run-off: Expert panel [Today]

Innovyze Surge Line Brings Surge Events to Life With Cutting-Edge Pipe Profile Animations

Innovyze Surge Line Brings Surge Events to Life With Cutting-Edge Pipe Profile Animations

High Quality Animation Gives Engineers Inside View of Model Activities for the First Time

Broomfield, Colorado USA, January 17, 2011 — Innovyze, a leading global innovator of business analytics software and technologies for wet infrastructure, today announced the worldwide release of the SurgeAnimatemodule for its industry-leading surge product line. The breakthrough pipe profile animation module brings a new level of visualization and interpretation power to transient analysis, helping engineers quickly gain a thorough understanding of the complex phenomena occurring within their distribution systems.

Available for InfoSurge and InfoWorks TS, the module is ideal for assessing the strength and effectiveness of water supply and distribution systems under a wide range of hydraulic transient conditions, from routine operation to emergency states. It has unprecedented power to help users confidently determine the best combination of surge protection devices to minimize the impact of objectionable pressure transients. The enhanced product suite reflects Innovyze’s vanguard position in the water industry and its continuing commitment to delivering pioneering technology for improving the safety and reliability of the world’s water supply.

“This key new modeling functionality makes it easy to get a handle on how transient waves propagate over time in distribution systems, allowing water utilities worldwide to better see how transient events are mitigated by surge protection devices,” noted Christopher W. Baxter, Ph.D., President of HYDRANNT Consulting Inc., in Port Coquitlam, BC, Canada. “Innovyze continues to raise the standard in the industry.”

Anticipating and controlling transient response is critical to ensuring the protection, integrity, and effective/efficient operation of water distribution systems. Transient responses can introduce pressures of sufficient magnitude (upsurge) to burst pipes and damage equipment. The resulting repercussions can range from extended service outages to loss of property and life. Transient responses can also produce sub-atmospheric pressures (downsurge) that can force contaminated groundwater into the distribution system at a leaky joint, crack or break, leading to grave health consequences when carried out downstream in the pipe system. Sustained sub-atmospheric pressures may also lead to cavitation and water column separation, resulting in severe “water hammer” effects as the vapor cavity collapses.

The Innovyze transient flow simulation technology suite addresses every facet of pressure surge analysis and its role in utility infrastructure management and protection, delivering the highest rate of return in the industry. It provides the engineer-friendly simulation framework water utilities need to identify characteristics that can make their water supply and distribution systems more susceptible to transient pressure events. Users can quickly and efficiently assess the effects of power outages, pump shutdowns and startups, valve closures, rapid demand and pump speed changes, as well as the efficacy of any combination of surge protection devices. The product suite also accurately simulates cavitation and water column separation and evaluates their intensity. Its blazing simulation speed, unrivalled in the industry, makes transient analysis an easier and more enjoyable task.

The new SurgeAnimate module enables users to create live animations of pipe profiles simply by specifying the first and last nodes; the rest is done automatically. Tank and reservoir levels, pump speeds, water flow or velocity rates are all animated. Many surge devices (such as air valves and bladder tanks) are also animated in detail. Animation speed can be set and stopped or restarted interactively at any simulation time period, allowing the user to thoroughly view and analyze the model’s transient activities (including cavitation pressure). Animations can be saved as AVI files.

Armed with these mission-critical network modeling capabilities, water utilities can more accurately assess their susceptibility to low or negative pressures caused by transient surges, identify vulnerable areas and risks, evaluate and design sound control and mitigation measures, and determine improved operational plans and security upgrades.

“The ability to confidently assess distribution system vulnerability to pressure transients is becoming more critical every day,” said Innovyze President and Chief Operating Officer Paul F. Boulos, Ph.D., BCEEM, Hon.D.WRE, F. ASCE. “Our new SurgeAnimate module makes models come alive, allowing users to go inside the pipes and network elements for the first time. This unprecedented ability to see and experience model transient activities in real time is critical to designing reliable, enduring systems and protecting public health.”

Surcharged Node and the Link Connection in SWMM 5

Subject: Surcharged Node and the Link Connection in SWMM 5

A surcharged node in SWMM 5 uses this point iteration equation (Figure 1):

dY/dt = dQ / The sum of the Connecting Link values of dQ/dH

where Y is the depth in the node, dt is the time step, H is the head across the link (downstream – upstream), dQ is the net inflow into the node and dQ/dH is the derivative with respect to H of the link St Venant equation. If you are trying to calibrate the surcharged node depth, the main calibration variables are the time step and the link roughness:

1. Mannings’s N

2. Hazen-Williams or

3. Darcy-Weisbach

The link roughness is part of the term dq1 in the St Venant solution and the other loss terms are included in the term dq5. You can adjust the roughness of the surcharged link to affect the node surcharge depth.

Figure 1. The Node Surcharge Equation is a function of the net inflow and the sum of the term dQ/dH in all connecting links. Generally, as you increase the roughness the value of dQ/dH increases and the denominator of the term dY/dt = dQ/dQdH increases.

Figure 2. The value of dQ/dH in a link as the roughness of the link increases.

HOW MOSQUITOES FLY IN RAIN from 3Quarks

HOW MOSQUITOES FLY IN RAIN

Mariel Emrich in Talking Science:

Mosquitoes are as adept at flying in rainstorms as under clear skies. But how is that possible? Wouldn’t rain crush a mosquito to the ground since mosquitoes weigh 50 times less than raindrops?

David Hu, an assistant professor of mechanical engineering and biology at the Georgia Institute of Technology, and his graduate research assistantAndrew Dickerson have found that while mosquitoes do get hit by raindrops, they don’t get crushed by them.

Hu discussed their research in a talk at November's APS Division of Fluid Dynamics Meetingthat was entitled “How Mosquitoes Fly in the Rain”.

The researchers measured the impact forces of raindrops on both regular mosquitoes and custom-built mosquito mimics. The mimics were made from small Styrofoam spheres of mosquito-like size and mass. They used high-speed video to capture images of the mosquitoes getting hit with raindrops.

Since the bugs fly so slowly (a maximum of 1 meter per second) compared to the drops (which fall between 5 to 9 meters per second), the mosquitoes cannot react quickly enough for avoidance, and most likely cannot sense the imminent collision.

More here.

Posted by Abbas Raza at 03:42 PM | Permalink