Diffusion - convection solution in 2D using unstructured mesh (mechanical engineering)

I am looking for a skilled freelancer to develop a solution for diffusion-convection problems like heat transfer in 2D using an unstructured mesh. The project requires high accuracy in the solution and the use of the finite volume method.

I've got a code in html for structured mesh and also for unstructured mesh but the problem is when I use more elements for the unstructured mesh the solution becames too different from the structured solution so I want to correct the code for unstructured mesh so i can increase the number of elements without changes in the results.

Skills and Experience:
- Strong expertise in numerical methods, specifically the finite volume method
- Experience in solving diffusion-convection problems like
- Proficiency in working with unstructured meshes
- Knowledge of 2D modeling and simulation
- Ability to ensure high accuracy in the solution
- Familiarity with WEB based programming languages for implementing the solution like html and javascript.