Skip to main content

Trapezoidal Channel Analysis with FlowStudio

This walkthrough shows how to find normal depth in a trapezoidal open channel when you know discharge, geometry, Manning’s n, and bed slope—using FlowStudio’s trapezoidal open-channel worksheet (uniform flow, SI units).

Open FlowStudio → https://flow.syncster.dev

What you are solving

In uniform flow, depth and velocity stay constant along a long prismatic reach. Manning’s equation links discharge to geometry and resistance. For a trapezoid with bottom width b and side slope z (horizontal to vertical, H:V), flow area and wetted perimeter depend on water depth y. If Q, b, z, n, and S are given, there is a unique normal depth y that satisfies Manning for that discharge (within physical limits).

FlowStudio uses the standard relations: area A = y(b + zy), wetted perimeter P = b + 2y√(1 + z²), hydraulic radius R = A/P, then V = (1/n)R2/3S1/2 and Q = VA. It also reports top width, hydraulic depth, and Froude number so you can judge subcritical vs supercritical flow.

Step 1 — Create the worksheet

Sign in if prompted, then create or open a project. Add a new worksheet and choose the type for trapezoidal open channel (Manning, uniform flow). Open the sheet so you see the form, the unknown selector, and the chart areas for section and rating curve.


Step 2 — Choose “Water depth” as the unknown

Select Water depth (discharge known). The form will expect you to enter discharge Q and will compute depth y after you press Calculate. The depth field is not the primary input in this mode.

Step 3 — Enter channel data

Type your SI values (meters, m³/s, dimensionless n and z, slope S as m/m). For a reproducible demo you might use, for example: b = 3 m, z = 2 (2H:1V sides), n = 0.025, S = 0.0004, Q = 8 m³/s—adjust to match your own case.

Use a realistic Manning n for your lining (concrete, earth, vegetation, etc.). Side slope z is the horizontal run per one unit of vertical (0 for a rectangle).

Step 4 — Calculate and read the table

Click Calculate. FlowStudio solves for y by bracketing Manning’s Q(y) against your target discharge and fills the results table: depth, velocity, area, wetted perimeter, hydraulic radius, top width, hydraulic depth, Froude number, and discharge check.


Step 5 — Use the cross section and rating curve

The section graphic shows the trapezoid with the computed water surface. The rating curve plots depth vs discharge for your fixed b, z, n, and S; your (Q, y) point should lie on that curve—useful for sanity checks and for seeing how sensitive depth is to discharge.

Reading Fr and common pitfalls

  • Froude number Fr < 1 → subcritical; Fr > 1 → supercritical (for this hydraulic depth definition).
  • If discharge is too large for the chosen geometry and slope, the solver may not find a depth—reduce Q, steepen S, widen b, or smooth the channel (n).
  • Manning uniform flow assumes a long, straight, steady reach; transitions, bends, and backwater need other methods (e.g. gradually varied flow elsewhere in FlowStudio).

Wrap-up

You’ve walked through normal depth in a trapezoidal channel with known Q, using the same closure as FlowStudio’s worksheet. Repeat with your project’s b, z, n, S, and design discharges, and keep comparing to codes and field data.

Run the sheet live at https://flow.syncster.dev.

Labels:

Comments

Post a Comment

Popular posts from this blog

How I used Google Sheets and Apps Script

Google Sheet is one of the most powerful spreadsheet application that exists online, rivaling with Microsoft's Excel. One of the main strengths is its strong support for collaboration with other users, much easier and popular than collaboration tools with Microsoft Office. Aside from plain spreadsheet, it also supports extensions such as macro. If you are familiar with macros on other office tools, they work almost the same. However, the most extension I use and tinker with is the Apps Scipt . Apps Script Extension One of the challenges I faced recently is how do I track or monitor reports in our department if they are submitted on time or worst, forgotten due to lack of better monitoring tools. So I thought if there can be simple applications that can be deployed or use by a more general user to allow reminding periodically what reports are approaching due dates or those that are past dues. Then I looked for a way, instead of creating a full blown app from scratc...
Post a Comment
Read more

Automate Sending Email with Apps Script and Google Sheet

Introduction It has been too long that many people uses Microsoft Excel in day-to-day computing tasks. It's so big that it almost resemble a programming language where non-technical people can create their own spreadsheet programs. It has many uses with just the default grid-type data entries. But Microsoft Office developers did not stopped there. They gave it more power by adding a scripting capability to it with VBA or Visual Basic for Applications. Most of the office apps of Microsoft has this VBA at their disposal but I most used it with Microsoft Excel. It was the most appropriate application for me to use it. But then come the big competition. I'll skip the open source apps that may compete with Microsoft Office and go directly with the big one. This is the Google Sheet from Google. Introducing Google Sheet Google Sheets is an online spreadsheet application that allows users to create, edit, and format spreadsheets to organize and analyze information....
Post a Comment
Read more

From Checkers to Consciousness: Tracing the Roots of AI

 Artificial intelligence (AI) and machine learning (ML) have exploded into our lives, powering everything from our music playlists to groundbreaking medical diagnoses. Even how our mobile phone cameras take pictures uses AI. But where did this extraordinary revolution begin? And how did we go from clunky, rule-based systems to the sophisticated, data-driven intelligence we see today? The quest to build intelligent machines has captivated thinkers, scientists, mathematicians and many more for centuries, with pioneers like Alan Turing laying crucial theoretical groundwork long before the formal establishment of the field.  Now let's dive into the fascinating origin story and explore the ever-expanding contributions of these transformative technologies. The Seeds of Intelligence: Early Days of AI The concept of artificial intelligence has roots in ancient myths and fictional automatons. However, the formal pursuit of AI as a scientific field began in the mid-20th century. Alan Tu...
Post a Comment
Read more