does "drag" boundary condition can't work with P1DGP2?

Hi,

You will need to add both a drag BC as well as a no-normal flow BC.

8.12.3.11 isn't saying anything about drag - this is a BC on the tangential
component of velocity, whereas no-normal flow is a BC on the normal
component of velocity.

Best wishes
Matt

On 21 February 2014 07:31, liu chin chi <
<email address hidden>> wrote:

> New question #244332 on Fluidity:
> https://answers.launchpad.net/fluidity/+question/244332
>
> Hi all,
>
> the manual metions in 8.12.3.11, does it means "drag" boundary
> condition can't work with P1DGP2?
> But 8.16 and 8.16.6 sugguest P1DGP2 and both a type::drag and a type::no
> normal flow at bottom boundary condition.
> I'm a liitle confused.
>
> By the way, dose there any forum for Fluidity model users to
> communicate ?
> Maybe who has some basic questions like me can search the information
> first before asking.
>
> Please excuse my poor English. Thanks.
>
> 8.12.3.11 No normal flow
> When using .../control volumes under Pressure .../spatial discretisation
> or when
> using .../integrate continuity by parts with CG Pressure and Velocity
> this boundary condition
> type imposes a weak no normal flow boundary condition on the surfaces
> specified.
>
> 8.16 Configuring ocean simulations
> This section contains advice for running a large scale ocean simulation
> in three dimensions. The
> flow domain is characterised by the large aspect ratio between horizontal
> and vertical length scales.
> The following is a set of recommended discretisation options for such
> simulations. It is based on
> the use of the P1DGP2 velocity, pressure element pair [Cotter et al.,
> 2009]. The recommendations are
> applicable to both global or ocean-scale domains as well as to smaller,
> regional or coastal domains.
> For the first case, see the additional instructions in section 8.16.8, to
> solve the equations on the sphere.
>
> 8.16.6 Boundary conditions
> For the bottom boundary condition, add both a type::drag and a
> type::no normal flow
> boundary condition under Velocity. A typical value for a dimensionless
> bottom friction coefficientfor the ocean is 0.0025.
>
> --
> You received this question notification because you are a member of
> Fluidity Core Team, which is an answer contact for Fluidity.
>

 Hi , Matthew

     Maybe I misunderstand 8.12.3.11. Dose it means no-normal flow BC under Velocity can be used with P1DGP2 mesh ?

Regards,

ChinChi

Hi ChinChi,

no_normal_flow can be used with P1DG_P2.

Jon

On 21/02/2014 10:01, liu chin chi wrote:
> Question #244332 on Fluidity changed:
> https://answers.launchpad.net/fluidity/+question/244332
>
> Status: Answered => Open
>
> liu chin chi is still having a problem:
>
> Hi , Matthew
>
> Maybe I misunderstand 8.12.3.11. Dose it means no-normal flow BC
> under Velocity can be used with P1DGP2 mesh ?
>
> Regards,
>
> ChinChi
>

--
Dr Jon Hill
Research Fellow
AMCG, Earth Science and Engineering
Imperial College London
Mob: 07748254812
Phone: +44(0)2075949321

Thanks Matthew Piggott, that solved my question.