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Weir

Introduction

In hydraulic engineering, a weir is a structure set in a waterway that allows water to overflow and is used to maintain a specific water level or measure flow. In CFD, they are often used for code validation by comparing analytical results with theoretical flow rates.

This example shows an example of mesh generation and calculation for the analysis of a constant water level in a square weir.

A simple geometry of a square weir is read into an stl file to generate a grid.

To use the pressure condition corresponding to the head of water at the inlet, the inlet boundary is divided into water and air regions. The water level at the inlet is 1.6 meters.

Geometry

The geometry of the weir is constructed as shown using an stl file and two [Hex6]s to separate the water and air boundary at the inlet.

Geomerty 설정

Click the [Import] button at the bottom to select the weir.stl file.

Click the [Add] button and select [Hex6] and set values as follows

Name : Hex6_1
Type : None
MIn. : (-2 -1 0)
Max. : (2 1 1.6), Generate z coordinates up to 1.6 because the water level is 1.6.

This will create six surfaces. Right-click on each surface and select [Edit/View] to rename them to

Hex6_1_xMin : water-in
Hex6_1_xMax : out
Hex6_1_yMin : front
Hex6_1_yMax : back
Hex6_1_zMin : bottom

In Geometry, select Hex6_1_zMax and right-click and select Edit/View. In the window that opens, change the type as [None]

Once more, click the [Add] button and select [Hex6] and set values as follows

Name : Hex6_2
Type : None
MIn. : (-2 -1 1.6)
Max. : (2 1 2)

This will create six surfaces. Right-click on each surface and select [Edit/View] to rename them to

Hex6_2_xMin : air-in
Hex6_2_xMax : out-1
Hex6_2_yMin : front-1
Hex6_2_yMax : back-1
Hex6_2_zMax : top

In Geometry, select Hex6_2_zMix and right-click and select Edit/View. In the window that opens, change the type as [None]