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Listed below are the 20 most current frequently asked questions in relation to use of the Visual Hydraulics software. Questions are updated as they are received. If you have a question that is not covered below, please contact us immediately.
	“What is the difference between partially submerged and fully submerged weirs? Where is the line drawn?”
	Partial submergence means that although the downstream water level is higher than the weir, the natural head over the weir is still greater than the downstream water elevation. Full submergence occurs when the weir is “drowned out”, or the downstream water elevation is greater than the natural head over the weir.
	“When analyzing the hydraulics of a pipe, three methods for determining the friction loss are supplied – Darcy-Weisbach, Manning’s Equation, and the Hazen-Williams equation. Which is the most accurate, and is there a better time to use one equation over another?”
	In theory, the most accurate equation is the Darcy-Weisbach equation since it is the only equation that relates its roughness value (f) to the diameter of the pipe, and also accounts for the varying regimes of flow. This is mostly a non-issue, however, since almost all pipes encountered during a hydraulic analysis exhibit fully turbulent behavior. The Hazen-Williams equation is still the most popular equation used in practice today because of its relative simplicity and accurate results. The Manning equation is typically reserved more for open channel flow but is also acceptable for full flow pipe analysis.
	“If units are taken off-line or put on-line, how is the flow divided among the units in operation?”
	If multiple units are specified for a particular section, the flow is assumed to be equally divided among each of the units, i.e. at 100 mgd being treated by 4 clarifiers, each unit is assumed to treat 25 mgd. If there is a known discrepancy in flow distribution between units, it is recommended that the unit with the worst case scenario (unit accepting the highest amount of flow) be analyzed separately from the other units.
	“In consulting a few of my engineering reference manuals, I’ve noticed that there can be some considerable variation in the K values reported for different pipe fittings. How was the K value list used in Visual Hydraulics compiled?”
	This is a perfect example of the fact that hydraulics is never an exact science. Many fittings have universal K values, such as standard bends and valves, but many fitting K values can vary from source to source. Visual Hydraulic’s K value database was compiled from the comparison of numerous popular hydraulic sources. Visual Hydraulics was programmed with a built-in working K value database that allows you to change K values for fittings and add fittings that may not exist in the standard database. This allows you to tailor the K value database to your needs.
	“I have return flows specified for my hydraulic profile, but I want to analyze the profile with no return flows, such as during high rain events. Can return flow scenarios be ‘turned off’?”
	Yes. The best way to do this is to simply add a flow value of “0” to the flow values you have stored for that particular return flow. Then you can choose that value of 0 for your return flow scenario and re-analyze your profile. Visual Hydraulics allows return flow values of 0 for any return flow condition.
	“The project properties form has an option for changing the temperature of the flow. How will changing the temperature affect a hydraulic profile?”
	This only affects the hydraulic analysis of pipes. Temperature can affect the viscosity of a liquid. Since the Reynolds number is dependent on viscosity, this in turn can affect the friction loss for a pipe if the Darcy-Weisbach method is being used. This is another reason the Darcy-Weisbach method is offered preferred in theory over the other methods for determining friction loss in a pipe. Note that if the flow temperature is changed in the middle of a profile, the temperature change will only take affect from that point on.
	“I analyzed a hydraulic profile for a treatment plant in English units. One of my client’s project reviewers wants to see the profile in Metric. Can I switch over to Metric after part or all of a profile has been completed?”
	Yes. Simply use the project properties option to change from English to Metric (make sure you specify the flow units you want to use, i.e. cubic meters per second or liters per second) and Visual Hydraulics will convert all of the existing profile from English to Metric.
	“We have a gate that is usually partially closed, it is used to modulate the flow to a tank via a 36 inch pipe. When specifying the opening height for the gate, do I use the opening of the pipe or height of the gate?”
	Always use the height of the gate above the invert of the pipe or opening. In other words, if the gate is 12 inches above the invert of your pipe, the opening height should be 12 inches.
	“I want to analyze the hydraulics of a rectangular clarifier. There is no tank option. What’s the best way to do this?”
	Visual Hydraulics does not analyze entire treatment units as a whole, because each unit usually contains many individual hydraulic features, such as ports, weirs, launders, etc. Visual Hydraulics analyzes each of these features separately. This provides for a more accurate modeling assessment of the entire unit.
	“We have 60 degree elbows on one of our pipe sections. No 60 degree elbow exits in the fitting database. How can this be added to the analysis?”
	There are two ways you can handle this. The first is the ‘non-standard elbow or bend’ fitting, which is listed in the standard fittings list. When this fitting is chosen, a form is supplied that allows you to specify the angle of your bend or elbow. Visual Hydraulics will then calculate a K value for this fitting based on that angle. The other way to do this is to simply add the fitting to the fitting database yourself. See the help files or usual manual on adding a fitting to the database.
	“I want to export my reports so that they can be emailed to my client. What format will they be in?”
	Visual Hydraulics can export your reports to a variety of formats. Any report can be exported to Microsoft Word, Adobe Acrobat, or simply as a standard text file. Once these reports are exported they can be formatted any way you wish.
	“We have a special type of grit removal equipment being installed at the head of a treatment plant. How can we account for the head loss through this unit in our hydraulic profile? The manufacturer says we can expect about 2 inches of head loss at our peak flow.”
	There are two options available for including losses that are not standard with Visual Hydraulics. The first is to simply specify an elevation step or drop. This feature allows you to step down or step up the profile any amount you wish, in this case you would just specify an elevation step of 2 inches, or about 0.17 feet. If hydraulic data is available from the manufacturer at a variety of design flows, the most effective option would be to create a head loss equation for the grit unit using the special loss feature. The program could then adjust the head loss for the grit unit if the design flows are changed. This is spelled out in detail in the help files and in the user manual.
	“Is it necessary to specify return flow conditions? Can’t you just account for the return flows by adding it to the plant flow?”
	Yes, you can do that. This will take away a lot of flexibility, however. If you correctly separate return flows from forward flows, you can change any flow condition and see how it will affect the entire profile. If you don’t separate the conditions and want to change one of them, you would have to individually account for this by changing the flow value for each section of the profile.
	“I keep getting a ‘high velocity’ flag for one of the pipe sections I have in my profile. According to the message it says that velocities over 10 feet per second are not recommended. Should we try and increase this diameter?”
	The warning conditions provided in the program are for guidance only, and are in place to ensure a mistake is not made. Although very high velocities are usually not recommended and can result in high head losses for pipes, the design may be acceptable. Submerged weirs are always flagged in the program, for example. Some weirs are designed to operate in a submerged condition (such as broad crested weirs). Proper engineering judgment should be used when an unusual condition is encountered.
	“I have a Parshall flume in my hydraulic profile. I changed the flow condition and the resulting water level in the flume is the same as the water level in the channel downstream. Is this because the flume is submerged?”
	Yes. Basically the water level downstream is greater than the natural water level that would occur flowing through the flume at that flow condition, therefore the downstream water level governs. Note that submerged flumes are not recommended, although it may be acceptable if they are only being used to split flow. If flow measurement is occurring in this flume, the results will be inaccurate.
	“On the main screen are the ‘current’ forward and return flow conditions. Are these the flows that the profile has been analyzed at?”
	The flows shown on the main screen in the current flow boxes are the conditions the hydraulic profile has been calculated for. To update or change any flow condition, simply use the ‘Options – System Flows’ menu or the flows icon on the toolbar. Whenever a different flow condition or conditions are specified, the profile is automatically re-evaluated at these new conditions.
	“I have a channel that I want to analyze before adding it to the hydraulic profile, because I’m not sure if the channel is large enough to handle the peak flow. I know this can be done using the individual section mode. Do I have to start a new profile to use this mode?”
	No, you do not have to start a new profile. If you have an existing hydraulic profile open and wish to switch to individual profile mode, your profile will simply be stored in the program until you wish to switch back to it. This allows you to analyze anything separate from the hydraulic profile.
	“We have completed our hydraulic profile and want to include as much detail as possible in our design report. Ideally, we’d like to include the summary equations in the report as well as the reports generated by the program. Is there a way to do this?”
	The best way to do this is to simply hit “Alt-Print Screen” on your computer when you have the summary equations displayed. This copies what is on the current screen to your clipboard. You can then paste this into your report.
	“I noticed on the pipe design form that there is an option titled ‘Other’. What is this for?”
	The ‘Other’ option is for an irregularly shaped pipe or conduit, something not circular or rectangular. It’s very rare, but has been encountered enough for us to add it as an option to the pipe form. If this option is selected, you must know the pipe's cross sectional area and hydraulic radius to perform the analysis. In addition, the Hazen-Williams equation cannot be used in this case.
	“If I want to insert a section between two existing sections of my profile, how does the program account for this?”
	Overlooking something or having something added to a design is common. This is why the insert section option was added. It allows you to place a new section between any two existing sections of the hydraulic profile. Inserting a section follows the same procedure as adding any new section, you just have to specify where you want the section inserted into your profile. Inserting a section can have significant impacts on a hydraulic profile. When a section is inserted, the entire hydraulic profile is re-evaluated to account for the new loss.