A simple question
 

heyy guys,

I have a very simple thing to ask...

I am using 6th order central difference scheme....for a partial difference term, say it includes 12 points (6 right side of the point and 6 left of it). It is fine while we have sufficient number of points both the sides. However, when we approach a boundary, we are not having sufficient points on one of the sides....and thats why we take ghost-cells on other side of the boundary....

my question is:

1. how many ghost cells do we need to consider??? Well, I think it should be 6. If I am wrong, please suggest me something in this regard.

2. Lets say, only 2 ghost cells have been taken. It is always possible to achieve the same level of 6th order accuracy if we take 10 points on interior side along with the 2 ghost points outside (10+2 = 12). Is there anything wrong in it??

thanks in anticipation!!

chandra shekhar