and I tried modeling without the pipe wall part sticking outside the sand region and it seemed to work. But I have a few doubts that would be great if I can have clarified:n- I kept the top of sand region at constant 70C . But after the solution was calculated, the top of the sand was 67.9C. Is this normal or does it mean the results are wrong?nn- Also, the residuals started rising a bit midway around 200-250 iterations but then started dropping again. Is this fine or is it also a problem?nnYour advice is much appreciated!nn