What are The Differences Between Submerged and Free Weir Flow?

When you install a weir in your system, there are a variety of factors that must be considered, including your likely flow regime. Both free flow and submerged regimes can greatly affect the functionality of your weir, which is why it’s so important to understand the difference between the two.

Once you’re clear on what separates free low and submerged conditions, you should be able to get the most out of the weir in your operation. Learn more about submerged and free flow conditions, how they affect your weir, and get a few tips for dealing with each of these flow regimes.

Submerged Flow and Weirs

Submerged low results when the downstream conditions are altered, resulting in less water discharging over your weir. While this isn’t necessarily a cause for concern, it can interfere with the measurements taken by your operators. If the weir in your system is currently experiencing submergence, the readings taken by your operators will show that your flow rate is much higher than it is in reality. If you don’t take this into account, your operation’s success will likely be deceased.

Fortunately, it’s possible to correct for submergence by making some small calculations. However, this means that your operators will need to understand the proper method for submergence correction.

Free Flow Conditions

Free flow occurs when the downstream conditions in your system are unaffected. This is also known as modular flow. If you have a free flow regime, it means that water is freely spilling over the nappe of your weir.

The level of water will need to be lower than your weir crest’s lowest point of elevation for free flow to occur. The size of your weir notch will determine whether or not your nappe is aerated.

Which Flow Regime is Better?

Now that you know about the two potential flow regimes and how they can affect your weir, you can decide which better suits your system.

Although your weir can function in both submerged and free flow conditions, free flow is always the better choice. With free flow conditions, your measurements will be considerably more accurate, and your operators will be able to take these readings without having to perform complicated calculations. However, if you want to maintain free flow conditions in your system, you will need to make sure your weir is installed correctly, meaning it will need to be installed higher than you might expect.

Install a Weir in Your System

When installing a weir in your water management operation, preparing for the expected flow regime is of the utmost importance. However, what’s even more important is having the highest quality tools possible. Fortunately, when you need a first-rate fiberglass weir box for your water management operation, you only need to shop with Tracom, FRP.

The focus of the team at Tracom, FRP is helping our customers find the fiberglass water management products that will help them succeed. If you browse our catalog, you’ll find some of the best fiberglass products on the market today, including weirs that will function in both submerged and free flow conditions. Talk to us about your needs today so that we can help you purchase the water management tools you need.