Bugfix inc hyd

This fixes issues #972 (closed) The solution is to allow vertical diffusion even in cells that are distorted. If not, effects of bottom friction are correctly taken into account and velocities are completely wrong. I think that for prisms, it is not a problem to allow vertical diffusion, as this happens in a vertical profile only, so it should not be affected by hydrostatically inconsistent elements.

A few notes: I only tested for prismatic elements, not for tetraëders (so i do not know whether also changes are needed to mt02_tt.f). I only tested with hydrostatic flow.

I found that the V test case is affected. Now some spurious currents (with velocities 1E-7 m/s) are generated. That's why I changed the coefficients in the vnv.py file. the currents are weaker though than without the use of the hydrostatic inconsistencies filter.

sources/utils/bief/mt02pp.f

@@ -79,6 +79,14 @@
 !+        V7P0
 !+   Now SH%TYPR checked to cancel vertical diffusion.
 !
+!history  WA BREUGEM (IMDC)
+!+        12/01/2024
+!+        V9P0
+!+   Hydrostatic inconsistencies filter not applied to vertical
+!+   diffusivity
+!+   Application of the filter leads to completely different tidal
+!+   signal with and without
+!
 !~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 !| F              |-->| FUNCTION USED IN THE FORMULA
 !| FORMUL         |-->| FORMULA DESCRIBING THE RESULTING MATRIX
@@ -269,9 +277,6 @@
           NG4=0.D0
           NG5=0.D0
           NG6=0.D0
-          NH1=0.D0
-          NH2=0.D0
-          NH3=0.D0
         ELSE
           NF1=F(I1)/H1
           NF2=F(I2)/H2
@@ -292,6 +297,20 @@
           NH2=(H(I2)+H(II5))/H2
           NH3=(H(I3)+H(II6))/H3
         ENDIF
+!VERTICAL DIFFUSIVITY SHOULD NOT BE SET TO ZERO. 
+!OTHERWISE BOTTOM FRICTION IS NOT TAKEN IN TO ACCOUNT CORRECTLY
+        IF(H1.LT.CHOUIA.OR.H2.LT.CHOUIA.OR.H3.LT.CHOUIA) THEN
+           NH1 = 0.0D0
+           NH2 = 0.0D0
+           NH3 = 0.0D0
+        ELSE
+!         DEPENDING ON THE CASE (II4=I1 OR I4, ETC.)
+!         ALTERNATIVE WITH VERTICAL LINEAR VISCOSITY (II4=I4)
+!         ALTERNATIVE WITH P0 VERTICAL VISCOSITY ON THE VERTICAL (II4=I1)
+           NH1=(H(I1)+H(II4))/H1
+           NH2=(H(I2)+H(II5))/H2
+           NH3=(H(I3)+H(II6))/H3
+        ENDIF
 !
         SNI=NF1+NF2+NF3
         SNS=NF4+NF5+NF6