I have programmed primarily in C for the last 28 years. I am primarily a Linux kernel programmer. I have written huge amount of both kernel code and user level code, from simple to extremely complex code, in the areas of Systems programming, new Storage software products, Linux/Unix Admin tools etc. I'm quite good at MPI programming as well (I worked on HP's High Performance Compute Cluster).
I will easily be able to come up with excellent C code to do your computation of fluid mechanics. However, I'd like to know the details first.