Dear Juan, What kind of polynomial space are you projecting onto? Is it the standard Nek basis (which is piecewise polynomial), or something different? We have routines to do dealiasing, but it might be better to understand the problem a bit more. Paul ________________________________ From: [email protected] [[email protected]] on behalf of [email protected] [[email protected]] Sent: Tuesday, March 21, 2017 9:08 PM To: [email protected] Subject: [Nek5000-users] Project a solution onto a polynomial space Hello, I need to compute some non-linear quantities as part of a post-processing procedure. Because they are non-linear, I will need to do some kind of dealiasing. So far, I know how to map the velocity field onto a finer grid (higher polynomial order) to compute the non-linear quantities. However, I don't know how to project the resulting field onto the original polynomial space. Note, I want to find the "projection" onto the original space, but not the "interpolation". Thanks, Juan Diego