https://github.com/relaxxpls/flow-across-weir
Analysis of fluid flow across a weir in Ansys 🌊
https://github.com/relaxxpls/flow-across-weir
Last synced: 2 months ago
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Analysis of fluid flow across a weir in Ansys 🌊
- Host: GitHub
- URL: https://github.com/relaxxpls/flow-across-weir
- Owner: relaxxpls
- Created: 2021-05-13T16:34:23.000Z (almost 4 years ago)
- Default Branch: main
- Last Pushed: 2021-05-13T19:55:24.000Z (almost 4 years ago)
- Last Synced: 2025-01-03T03:16:33.209Z (4 months ago)
- Language: C++
- Homepage:
- Size: 23.6 MB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Control of Weir Flow by Changing Geometry
## Team
|Laxman Desai|Sarthak Bhardwaj|Sagar Yadav|Krutarth Dhaduk|
|:-------:|:-------:|:-------:|:-------:|
|190020066|190040106|19D180026|19D170012|
## Problem statement
We will try and understand how height of fluid over weir affects the flow rate of water across the weir in laminar and turbulent conditions.
## Assumptions
1. Fluid is water at 25 degrees.
2. Surface tension modeling is done by the continuum method 
3. For the calculation of Reynold's number, flow is approximated to that over a flat plate. Transition from laminar to turbulent assumed at 
## Properties
### Dimensions
* Fixed:
1. 
2. 
3. 
* Variables:
1. 
2. 
3. 
### Flow
* Laminar:
1. 
2. 
* Turbulent:
1. 
2. 
### Mesh
* Divisions per unit length in the mesh = 2.
### Solver
* K-epsilon turbulence model (2 equations) used.
* Volume ratio used is modified high resolution schemes for interface capturing (HRIC).
* Time step size = 0.05 s
* Number of steps = 200
* Reporting interval = 10
## Boundary conditions
1. No slip condition on the stream bed & the surface of weir.
2. Plug flow in the inlet stream.
## Visualization
Figure 1.1: 3D geometry of flow over weir
Figure 1.2: Cross section view
Figure 1.3: Mesh cross section view
## Geometry
### Case 1: 
#### Properties
Figure 2.1: 2D mesh for case 1 (H=0)
#### Mesh - `Gmsh .geo file`
```glsl
// Gmsh project created on Mon May 10 10:15:28 2021
SetFactory("OpenCASCADE");
Point(1) = {0, 0, 0, 1.0};
Point(2) = {15, 0, 0, 1.0};
Point(3) = {15, 3, 0, 1.0};
Point(4) = {16, 3, 0, 1.0};
Point(5) = {16, 0, 0, 1.0};
Point(6) = {25, 0, 0, 1.0};
Point(7) = {25, 6, 0, 1.0};
Point(8) = {0, 6, 0, 1.0};
Point(9) = {0, 3, 0, 1.0};
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 5};
Line(5) = {5, 6};
Line(6) = {6, 7};
Line(7) = {7, 8};
Line(8) = {8, 9};
Line(9) = {9, 1};
Curve Loop(1) = {8, 9, 1, 2, 3, 4, 5, 6, 7};
Plane Surface(1) = {1};
Physical Curve("inlet", 10) = {9};
Physical Curve("outlet", 11) = {6, 5};
Physical Curve("ambient", 12) = {7};
Physical Curve("fw", 13) = {8, 1, 2, 3, 4};
Physical Surface("Area1", 14) = {1};
Transfinite Curve {7} = 50 Using Progression 1;
Transfinite Curve {6} = 12 Using Progression 1;
Transfinite Curve {8} = 6 Using Progression 1;
Transfinite Curve {9} = 6 Using Progression 1;
Transfinite Curve {1} = 30 Using Progression 1;
Transfinite Curve {5} = 18 Using Progression 1;
Transfinite Curve {2} = 6 Using Progression 1;
Transfinite Curve {4} = 6 Using Progression 1;
Transfinite Curve {3} = 2 Using Progression 1;
```
### Case 2: 
#### Properties
Figure 2.2: 2D mesh for case 2 (H=0.5)
#### Mesh - `Gmsh .geo file`
```glsl
SetFactory("OpenCASCADE");
Point(1) = {0, 0, 0, 1.0};
Point(2) = {15, 0, 0, 1.0};
Point(3) = {15, 2.5, 0, 1.0};
Point(4) = {16, 2.5, 0, 1.0};
Point(5) = {16, 0, 0, 1.0};
Point(6) = {25, 0, 0, 1.0};
Point(7) = {25, 6, 0, 1.0};
Point(8) = {0, 6, 0, 1.0};
Point(9) = {0, 3, 0, 1.0};
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 5};
Line(5) = {5, 6};
Line(6) = {6, 7};
Line(7) = {7, 8};
Line(8) = {8, 9};
Line(9) = {9, 1};
Curve Loop(1) = {9, 1, 2, 3, 4, 5, 6, 7, 8};
Plane Surface(1) = {1};
Physical Curve("inlet", 10) = {9};
Physical Curve("outlet", 11) = {6, 5};
Physical Curve("ambient", 12) = {7};
Physical Curve("fw", 13) = {8, 1, 2, 3, 4};
Physical Surface("Area2", 14) = {1};
SetFactory("OpenCASCADE");
Transfinite Curve {7} = 50 Using Progression 1;
Transfinite Curve {6} = 12 Using Progression 1;
Transfinite Curve {8} = 6 Using Progression 1;
Transfinite Curve {9} = 6 Using Progression 1;
Transfinite Curve {1} = 30 Using Progression 1;
Transfinite Curve {5} = 18 Using Progression 1;
Transfinite Curve {2} = 5 Using Progression 1;
Transfinite Curve {4} = 5 Using Progression 1;
Transfinite Curve {3} = 2 Using Progression 1;
```
### Case 3: 
#### Properties
Figure 2.3: 2D mesh for case 3 (H=1)
#### Mesh - `Gmsh .geo file`
```glsl
SetFactory("OpenCASCADE");
Point(1) = {0, 0, 0, 1.0};
Point(2) = {15, 0, 0, 1.0};
Point(3) = {15, 2, 0, 1.0};
Point(4) = {16, 2, 0, 1.0};
Point(5) = {16, 0, 0, 1.0};
Point(6) = {25, 0, 0, 1.0};
Point(7) = {25, 6, 0, 1.0};
Point(8) = {0, 6, 0, 1.0};
Point(9) = {0, 3, 0, 1.0};
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 5};
Line(5) = {5, 6};
Line(6) = {6, 7};
Line(7) = {7, 8};
Line(8) = {8, 9};
Line(9) = {9, 1};
Curve Loop(1) = {8, 9, 1, 2, 3, 4, 5, 6, 7};
Plane Surface(1) = {1};
Physical Curve("inlet", 10) = {9};
Physical Curve("outlet", 11) = {6, 5};
Physical Curve("ambient", 12) = {7};
Physical Curve("fw", 13) = {8, 1, 2, 3, 4};
Physical Surface("Area3", 14) = {1};
Transfinite Curve {7} = 50 Using Progression 1;
Transfinite Curve {6} = 12 Using Progression 1;
Transfinite Curve {8} = 6 Using Progression 1;
Transfinite Curve {9} = 6 Using Progression 1;
Transfinite Curve {1} = 30 Using Progression 1;
Transfinite Curve {5} = 18 Using Progression 1;
Transfinite Curve {2} = 4 Using Progression 1;
Transfinite Curve {4} = 4 Using Progression 1;
Transfinite Curve {3} = 2 Using Progression 1;
```
## Results (general)
Figure 3.1: Position vs outlet velocity
Figure 3.2: Position vs outlet static pressure
Figure 3.3: Residuals vs iterations for laminar flow
Figure 3.4: Residuals vs iterations for
turbulent flow
## Results (case specific)
* Case specific versions of the general plots are not shown explicitly, but they follow similar trends.
### Case 1:
#### Laminar flow 
Figure 4.1 A: Velocity profile diagram under laminar conditions with height of stream over weir = 0m
Figure 4.1 B: Pressure field diagram under laminar conditions with height of stream over weir = 0m
#### Turbulent flow 
Figure 4.2 A: Velocity profile diagram under turbulent conditions with height of stream over weir = 0m
Figure 4.2 B: Pressure field diagram under turbulent conditions with height of stream over weir = 0m
### Case 2:
#### Laminar flow 
Figure 5.1 A: Velocity profile diagram under laminar conditions with height of stream over weir = 0.5m
Figure 5.1 B: Pressure field diagram under laminar conditions with height of stream over weir = 0.5m
#### Turbulent flow
Figure 5.2 A: Velocity profile diagram under turbulent conditions with height of stream over weir = 0.5m
Figure 5.2 B: Pressure field diagram under turbulent conditions with height of stream over weir = 0.5m
### Case 3:
#### Laminar flow
Figure 6.1 A: Velocity profile diagram under laminar conditions with height of stream over weir = 1m
Figure 6.1 B: Pressure field diagram under laminar conditions with height of stream over weir = 0.5m
#### Turbulent flow
Figure 6.2 A: Velocity profile diagram under turbulent conditions with height of stream over weir = 1m
Figure 6.2 B: Pressure field diagram under turbulent conditions with height of stream over weir = 1m
## Conclusion
Weirs are mainly used to control the flow rates of rivers during periods of high discharge. Sluice gates (or in some cases the height of the weir crest) can be altered to increase or decrease the volume of water flowing downstream.
For constant fluid flow rate, as the height of the weir decreases, distance covered by the fluid over the flat surface also decreases. On an average we observe that the fluid reaches 5 to 6m ahead of weir in case of turbulent flow (minimum in case where H=0) where as less than 1m in case of laminar flows.
Thus, for the optimum outflow conditions for turbulent flow is that the height of weir should be as close to the height of stream for minimum ahead reach of fluid and controlled outflow of fluid.