a basic question regarding reconstruction

CFD student

Hi,

I wrote a Finite Volume, 2-D, first order Euler code. I am trying to make it second order accurate using reconstruction method. The primitive variables are stored at the cell centers.

I interpolate these primitive variables from cell center to edge center to make it 2nd order accurate. Using this approach gives me very unstable solution, even after using limiters.

My Question is : should I interpolate {rho, u, v, P} or {rho, rho * u, rho * v , rho * E} to the edge center ?

thanx in advance, Sunny