Hi David, The context is indeed water waves. @Colin: yes the hack I suggested is what we have not tried yet; I am at MARIN two days and looked at what Floriane did hitherto, which seemed right except for the extension bit, so the alternative is either the hack I suggested, or my alternative below, as that avoids having to extend surface functions of only x,y to x,y,z. More context: the grid is obviously aligned/extruded in z such that a uniform function in z could also be defined by solving: d_zz f_3(x,y,z) =0 with f_3s(x,y,z) = f_s(x,y) at the the top z=H0 and the bottom z=b(x,y); now f_3s will become the 3D extension constant in z of f_s(x,y). This is however less pretty than what I asked below-below. Also f_s(x,y) will be an unknown in the larger problem. Best wishes, Onno ________________________________ From: firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> on behalf of David Ham <David.Ham@imperial.ac.uk> Sent: Thursday, April 14, 2016 8:08 PM To: firedrake Subject: Re: [firedrake] volume integration splitting Hi both, Can we see the full context for that integral, as there might be somwthing we can hack up quickly. On Thu, 14 Apr 2016 at 19:31, Cotter, Colin J <colin.cotter@imperial.ac.uk<mailto:colin.cotter@imperial.ac.uk>> wrote: Hi Onno, Not really, I expect you are thinking of something related to water waves? I was hoping that many issues relating to free surface might be helped by defining function spaces that are constant throughout the column, to facilitate coupling between free surface and the bulk. We discussed this a while back, but nothing was implemented. all the best --cjc On 14 April 2016 at 15:36, Onno Bokhove <O.Bokhove@leeds.ac.uk<mailto:O.Bokhove@leeds.ac.uk>> wrote: Hi (-), Can one in Firedrake split a volume integration in 3D, in a horizontal part (dx dy) and a vertical part (dz), as follows: \int_x\int_y f(x,y,t) [ \int_z g(x,y,z,) dz ] dy dx instead of \iiint f(x,y,t) g(x,y,z,t) dx dy dz ? Best wishes, Onno -- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916<http://www.cambridge.org/9781107663916> [http://assets.cambridge.org/97811076/63916/cover/9781107663916.jpg]