What is Open Channel Flow?
The flow of liquid through a channel with a free surface is defined as open channel flow. This free surface of the liquid is subjected to atmospheric pressure. Hence, open channel flow can also be defined as liquid flow through a passage at atmospheric pressure. The flow in an open channel occurs due to gravity that provides a bed slope. The liquid flow through the open channel can be of several types: steady and unsteady flow, laminar or turbulent flow, uniform or non-uniform flow, and finally, sub-critical, critical, and supercritical flow.
Steady and Unsteady Flow
In an open channel flow, if the flow parameters such as depth of flow, the velocity of flow, and the flow rate at a particular point on the fluid do not change for a time, it is called steady flow. And if at any point on the open channel flow, the flow parameters like depth of flow, flow velocity, and flow rate change their value over time, then it is called an unsteady flow.
Uniform Flow and Non-Uniform Flow
The flow in the channel is uniform if the velocity of flow and depth remains constant for a given channel length. In a Non-uniform flow, the flow parameters like velocity, depth of flow, etc., do not remain constant for a given channel length. The Non-uniform flow can be again defined as rapidly varying flow (RVF) and Gradually Varied Flow (GVF). In the case of RVF, the flow depth rapidly changes over a smaller channel length. It rises suddenly for a short length and settles back. While in a GVF, the depth of flow changes gradually over a longer channel length.
Laminar Flow and Turbulent Flow
Laminar and turbulent flow in open channel flow is defined based on the Reynolds Number. If the Reynolds number Re is less than 500 or 600, then the flow is called laminar flow. If the Reynolds number is more than 2000, the flow is turbulent. Also, a flow with Reynolds numbers between 500 and 2000 is in the transition state.
Critical, Sub-Critical, and Super–Critical Flow
Based on the Froude number (Fe), the open channel flow is categorized as critical, sub-critical, or supercritical. Open channel flow is Sub-critical if the Froude number is less than 1. Sub-Critical open channel flow is also defined as a tranquil or streaming flow. An open channel flow with a Froude number equal to one is critical. And supercritical flow in an open channel has a Froude number greater than 1. A supercritical flow is also called rapid, torrential, or shooting flow.
Open Channel Simulations in ANSYS Fluent Software
ANSYS Fluent can model the effects of open channel flow (e.g., rivers, dams, and surface-piercing structures in unbounded streams) using the VOF formulation and the open channel boundary condition. These flows involve a free surface between the flowing fluid and the fluid above it (generally the atmosphere). In such cases, wave propagation and free surface behavior become essential. The forces of gravity and inertia generally govern flow. This feature mostly applies to marine applications and the analysis of flows through drainage systems.
Open channel flows are characterized by the dimensionless Froude Number, defined as the ratio of inertia force and hydrostatic force.
Where V is the velocity magnitude, g is gravity, and y is a length scale, in this case, the distance from the bottom of the channel to the free surface.
To expand your knowledge about this method and its application in the industry and academic fields, you can enter the Open Channel Flow tab by clicking on the link to find more projects, for instance, using this method, the following simulation models the movement of a jet ski on the water and air interface.
MR-CFD, an Expert in the Field of Heat Transfer Simulations
Having several years of experience in simulating various problems in various CFD fields using ANSYS Fluent software, the MR-CFD team is ready to offer extensive modeling, meshing, and simulation services. Simulation Services for open channel simulations are categorized as follows:
- CFD simulation of Flumes
- CFD simulation of spillways
- CFD simulation of Canals
- CFD simulation of Weirs
- CFD simulation of streams
- CFD simulation of rivers
- CFD simulation of estuaries
Our services are not limited to the mentioned subjects, and the MR-CFD team is ready to undertake different and challenging projects in the heat transfer field ordered by our customers. You can consult with our experts freely and without charge and order your project by sending the problem details to us using the following address.
By outsourcing your project to the MR-CFD as a CFD simulation freelancer, you will not only receive the related project’s files (Geometry, Mesh, …), but also you will be provided with an extensive tutorial video demonstrating how you can create the geometry, mesh, and define the needed settings(pre-processing, processing and post-processing) in the ANSYS Fluent software all by yourself. Additionally, post-technical support is available to clarify issues and ambiguities.