# Create a geometry in DesignModeler/ Solidwroks/any CAD software

2024-08-26 12:57:47

## Problem:

The overall dimensions of the rectangular box will depend on the dimension of the underwater vehicle.

[Please use any dimensions and make a model similar to the above drawing]

The fluid flowing through the rectangular domain is water, with the following properties:

Density = 1000 kg/m3, Dynamic viscosity = 1.002 mPa.s

The boundary conditions for all the CFD models are:

Inlet velocity, U= 15 m/s; 40 m/s; 70 m/s Outlet Pressure = 0, Velocity at walls = 0 m/s (no slip)

Flow = Turbulent using default settings. Procedure and discussion points:

1. Create a geometry in DesignModeler/ Solidwroks/any CAD software

2. Build an appropriate mesh for the model. This will necessitate running the simulations and making a grid refinement study presenting the results for different grids for U= 15 m/s.

3. Using the converged grid, for U = 15 m/s, check the iterative

4. Using the converged grid, run CFX/FLUENT for U = 15 m/s, 40 m/s, and 70 m/s.

5. Chart the axial velocity profiles u(y) at the leading edge, at mid, at the trailing position of the vehicle and discuss your results.

6. Plot the velocity contours for U = 15 m/s, 40 m/s, and 70 m/s and discuss the flow characterization.

7. Plot the velocity vector for U = 15 m/s, 40 m/s, and 70 m/s and discuss

8. Plot the turbulence intensity for 15 m/s, 40 m/s, and 70 m/s and discuss

9. Plot the turbulence kinetic energy for U= 15 m/s, 40 m/s, and 70 m/s and discuss your

10. Plot the pressure contour for U= 15 m/s, 40 m/s, and 70 m/s and discuss your

11. Plot the velocity streamline for U= 15 m/s, 40 m/s, and 70 m/s and discuss your

12. Calculate the drag and lift coefficient for U = 15 m/s, 40 m/s, and 70 m/s and plot the results.

13. Verify your results with the existing findings.

## Submission:

A written report is to be submitted including a short introduction and conclusion (at least one page long for each). The report should contain a discussion of the points bolded above with evidence to support the discussion together with relevant figures such as figures illustrating the mesh or element distribution, plots of the velocity profiles, contour plots, etc.

**Plagiarised:**

#### 1. Creating the Geometry

To begin, create a simplified rectangular box model representing the underwater vehicle using CAD software such as SolidWorks, DesignModeler, or any equivalent tool. Assume the dimensions of the underwater vehicle as follows:

- Length: 5 meters
- Width: 2 meters
- Height: 1.5 meters

The rectangular domain will be designed around these dimensions, ensuring adequate space for fluid flow analysis.

#### 2. Building the Mesh

Generate a computational mesh for the model using an appropriate meshing tool. Ensure to conduct a grid refinement study by comparing results across different mesh densities. Start with a coarse grid and refine it gradually:

- Coarse Grid: ~100,000 elements
- Medium Grid: ~500,000 elements
- Fine Grid: ~1,000,000 elements

Compare parameters such as velocity and pressure distributions at U = 15 m/s to determine the convergence of the solution.

#### 3. Iterative Convergence Check

Using the converged grid (from the refinement study), perform a steady-state simulation at U = 15 m/s. Monitor residuals for continuity, momentum, and turbulence to ensure they fall below the convergence criteria (typically 1e-5).

#### 4. Running Simulations for Different Velocities

Using the converged grid:

- Run the CFD simulations at U = 15 m/s, 40 m/s, and 70 m/s using ANSYS CFX or FLUENT.
- Ensure to capture data for velocity profiles, turbulence characteristics, and pressure fields.

#### 5. Axial Velocity Profiles

Chart the axial velocity profiles $u(y)$ at:

- Leading edge
- Midsection
- Trailing edge

Analyze how the velocity distribution changes along the vehicle`s length.

#### 6. Velocity Contours

Plot velocity contours for U = 15 m/s, 40 m/s, and 70 m/s. Discuss how the flow accelerates or decelerates around the vehicle, indicating potential regions of flow separation and high shear.

#### 7. Velocity Vectors

Plot velocity vectors for each velocity scenario. Discuss the flow direction and magnitude, identifying vortices and flow reattachment points.

#### 8. Turbulence Intensity

Plot and discuss turbulence intensity at different velocities. Examine the changes in turbulent behavior as the inlet velocity increases, particularly near the vehicle`s surfaces.

#### 9. Turbulence Kinetic Energy (TKE)

Plot TKE for U = 15 m/s, 40 m/s, and 70 m/s. Discuss the energy distribution of turbulent eddies and how it impacts the flow field around the vehicle.

#### 10. Pressure Contours

Plot pressure contours for each inlet velocity. Discuss how pressure varies across the vehicle surface, identifying high and low-pressure regions contributing to drag and lift forces.

#### 11. Velocity Streamlines

Plot velocity streamlines for each velocity scenario. Discuss the overall flow pattern around the vehicle, noting any changes in streamline curvature and separation points.

#### 12. Drag and Lift Coefficients

Calculate drag ($C_{D}$) and lift ($C_{L}$) coefficients for U = 15 m/s, 40 m/s, and 70 m/s. Plot the results and analyze how aerodynamic forces vary with speed: $C_{D}=ρUAF $ $C_{L}=ρUAF $

Where:

- $F_{D}$ = Drag force
- $F_{L}$ = Lift force
- $ρ$ = Density of water (1000 kg/m^3)
- $U$ = Inlet velocity
- $A$ = Reference area

#### 13. Verification with Existing Findings

Compare your results with existing literature on underwater vehicle dynamics and CFD studies. Ensure your findings are consistent with established data and discuss any discrepancies.

### Key Points of Discussion

**Grid Refinement**: The refinement study should show diminishing changes in key parameters, indicating mesh independence.
**Velocity Profiles**: Changes in velocity profiles highlight regions of high shear stress and potential separation zones.
**Flow Characteristics**: Differences in flow behavior at various speeds provide insights into the aerodynamic efficiency of the vehicle.
**Turbulence Analysis**: Understanding turbulence intensity and kinetic energy helps in optimizing vehicle design for stability and control.
**Pressure and Force Analysis**: Pressure contours and force coefficients are crucial for designing vehicles with minimal drag and desired lift characteristics.

### Conclusion

This detailed CFD analysis aids in understanding the fluid dynamics around an underwater vehicle. The insights gained can drive design improvements, enhancing performance and efficiency in real-world applications.

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