Changes between Version 1 and Version 2 of 2016WP/NocWad

Timestamp:

2016-04-07T12:41:07+02:00 (8 years ago)

Author:

acc

Comment:

--

2016WP/NocWad

@@ -26 +26 @@
 
 == Abstract ==
+
+=== A Wetting and Drying (W/D) Method for NEMO-shelf Based on Flux Limiter ===
+
+==== Hedong Liu and Jason Holt (NOC, UK) ====
+
+NEMO discretize its computational domain with the structured C-grid, hence its W/D
+algorithm needs to deal with two types of grid cells: velocity grid cells and tracer grid
+cells. The essences of current method are to keep the positivity of watermass and avoid
+unphysical overshooting of velocity.At the same time, this method must respect the
+properties of local and global mass conservation. There are quite many existing methods
+for W/D,(see Balzano,A, 1998 and Medeiros,S.C. and Hagen,S.C, 2013). But there are still some
+robustness issues, such as model stability, computational efficiency.  In the current
+method, a flux limiter has been developed to take care of the mass positivity while a new
+barotropic pressure gradient filter is developed to prevent the velocity overshooting at
+the wetting and drying cells on a steep slope.
+
+In the following parts of this note, we will first derive the flux limiter and demonstrate
+its applications to the continuity equation, tracer equations. As the momentum equations
+is also linked with the W/D processes, we then detail the design of the gravity forcing
+filter which aims to remove the errors generated by the normal pressure gradient
+calculations in the W/D area. The implementation of the method in NEMO v3.6_STABLE source
+code will be illustrated at the last.
+
+==== Flux limiter ====
+
+In NEMO, the water column can be considered as a control volume V. The horizontal
+advection is the main process causing the wetting and drying on the grid cells (with the
+evaporation and precipitation as the other two reasons which will be dealt separately).
+For such a control volume V, we can define a flux limiter as follows:
+
+[[Image(math figs/fig01.png)]]
 
 This section should be completed before starting to develop the code, in order to find agreement on the method beforehand.