In my refinemeht case the corresponding grid is non-uniform. the distance from the wall to the nearest grid point is set to dx1=0.002.Now I want to form a formula by using the hyperbolic tangent function for stretching the cell sizes between dx1 and a constant size dx2=0.5 in the length L , and the number of nodes distributed over the length L is N. But I don't know how to form such a formula. If anyone know the method, please give me your advice, thank you very much.

Look for "stretching by hyperbolic tangent functions" on the net and you will find lots of references. Please let me know if you would like a code for this purpose.

yes i need this code for my univeristy study i will be thankful

If you have a code for this purpose, can you offer me the code? Thank you.

Will mail you next week after getting back to work from vacation.