Implementing the Synthetic Eddy Method (SEM) for turbulence inlet conditions involves generating synthetic turbulent fluctuations to simulate the effect of turbulent eddies at the inlet of a computational fluid dynamics (CFD) simulation. The SEM technique is commonly used to provide realistic and time-varying inflow conditions for turbulent flows. Here are some guidelines to help you with the implementation:

1. Understand the Synthetic Eddy Method: Familiarize yourself with the basic principles and concepts behind the SEM. It involves generating coherent structures resembling turbulent eddies and injecting them at the inlet boundary of the CFD domain. The synthetic fluctuations should possess statistical properties consistent with the desired turbulence characteristics.

2. Determine the turbulence characteristics: Define the turbulence parameters required for your simulation, such as turbulence intensity, length scales, and integral time scales. These characteristics should be representative of the real flow conditions you are trying to simulate.

3. Choose an appropriate method for synthetic eddy generation: There are several methods available for generating synthetic eddies, such as the synthetic eddy method, synthetic turbulence method, or rescaling method. Select the most suitable method based on the complexity of your simulation and the desired level of accuracy.

4. Generate synthetic eddies: Implement the chosen method to generate synthetic eddies that mimic the desired turbulence characteristics. This typically involves generating random numbers with appropriate statistical properties and using them to perturb the flow variables (velocity, pressure, etc.) at the inlet boundary.

5. Validate the synthetic eddies: Verify the statistical properties of the generated synthetic eddies by comparing them to experimental data or other reference simulations. This step ensures that the generated fluctuations accurately represent the desired turbulence characteristics.

6. Implement the synthetic eddy generator: Integrate the synthetic eddy generator into your CFD simulation code or workflow. This may involve modifying the code to include the synthetic fluctuations at the inlet boundary or using pre-processing tools to inject the synthetic eddies.

7. Perform simulations and analyze results: Run the CFD simulations with the synthetic eddy method enabled. Post-process the results to analyze the flow behavior and validate against experimental or reference data. Assess the accuracy and realism of the turbulence simulation at the inlet.

8. Iterate and refine: If necessary, iterate the process to improve the fidelity of the synthetic eddy generation or adjust the turbulence characteristics. Fine-tune the parameters based on the simulation results and perform additional validations if required.

9. Document and report: Document the implementation details, methodology, and validation results for future reference. Properly document your code modifications or pre-processing steps, making it easier for others to understand and reproduce your work.

Remember that the implementation of the Synthetic Eddy Method may vary depending on the specific CFD software or framework you are using. Therefore, consult the documentation and resources provided by the software developers for further guidance on incorporating synthetic eddy methods into your simulation setup.

You can check the work done by Shur et. al on synthetic turbulence generator. It might be a good starting point to check his work, and then move on to understand how the implementation actually works. The STG is quite important when performing off-shore wind turbine simulations, where the wave shape and wind velocities need to be tested for different unsteady scenarios.

One way to generate turbulence at the inlet is by implementing Divergence Free Synthetic Eddy Method. The method is first introduced by Poletto (2015) with theoretical framework described in his thesis as below;

https://www.escholar.manchester.ac.uk/uk-ac-man-scw:262700

The method is now integrated within OpenFOAM software. Tutorials with regards to channel flow is accessible within the software. The method seems easy to be implemented as three statistical parameters of Reynold's stress (R), Turbulent Length Scale (L) and Mean velocity (U) can be calculated using DNS or RANS (need further validation) to be prescribed at the inlet. You can perform the initial simulation using these two methods, read and write the parameters in a file, then supply them inside the "Constant" directory inside openFoam. Then, set the inlet boundary condition as turbulent inlet as the type of the boundary condition. Below is for your further reference;

https://www.openfoam.com/documentation/guides/latest/doc/guide-bcs-inlet-velocity-dfsem.html