Transcript Free surface flows in Code Saturne

SPH weekly meeting
Free surface flows in Code Saturne
Results 23/11/2009
Olivier Cozzi
Presentation of Code_Saturne…
CFD code based on a co-located Finite Volume approach
Parallel code coupling capabilities
… and its ALE module
New boundary conditions for the boundary faces
Diffusion equation solver to know the mesh velocities for all the
internal and boundary faces
Move of the mesh at the end of the time step
Equations of the problem
Mass Conservation Law
Momentum Conservation Law
Scalar Conservation Law
+
Space Conservation Law  respected in C_S when the mesh just moves vertically
+
Kinetic boundary condition 
on the free surface, that is to
say:
Dynamic boundary condition 
(because, on the free surface, sheer stress, normal stress, and effect of the surface
tension can be neglected)
Free-surface module within C-S
Dynamic boundary condition  use of the usual usclim.F routine:
on the free surface
Kinetic boundary condition  use of the special ALE usalcl.F routine:
on the free surface
Free-surface module within C-S
End of tn, save
of fluid values
Start of tn+1
Use of last
mfsn for vb
Use of last
mfsn+1 for vb
Load of tn
values, except
for mfs
NS solution,
new mfsn+1
Move of the
free surface
End of tn+1,
save of fluid
values
Etc., until
convergence!
Free-surface module within C-S
Variable of activation
Choice of convergence accuracy and max iteration number
Selection of time scheme (second order Crank-Nicolson
method, or first order implicit Euler method)
Parallel computation still available
Results:
1. Standing wave
Wave amplitude A = 1m
Wavelength λ = 0.5L
Mesh: 105*20*1
Initial shape and 2nd order theoretical solution
(Chabert d'Hieres formula):
Airy's formula:
 T = 9,8s period in this case
Results:
1. Standing wave
Results:
1. Standing wave
100 time step of 100ms per period, ~100 cells per spatial period, courant max : ~0.6,
16 000 time steps
Free surface height at the
left side wall as function
of time
Remarks:
-Good height
Results:
1. Standing wave
100 time step of 100ms per period, ~100 cells per spatial period, courant max : ~0.6,
16 000 time steps
Free surface height at the
left side wall as function
of time
Remarks:
-Good height
-Time period overestimated
9,84s > Tth = 9,78 s
Results:
1. Standing wave
100 time step of 100ms per period, ~100 cells per spatial period, courant max : ~0.6,
16 000 time steps
Global relative volume
as function of time
Remarks:
-Loss of volume…
-0,018% per hour
Results:
1. Standing wave
100 time step of 100ms per period, ~100 cells per spatial period, courant max : ~0.6,
16 000 time steps
Global relative energy
as function of time
Remarks:
-Loss of energy…
-0,05% per hour
Results:
2. Solitary wave
Wave amplitude A = 2m
Mesh: 400*15*1
Gaussian shape:
Results:
2. Solitary wave
Results:
2. Solitary wave
Calculation of 2000 time step of 50ms, courant max : ~0.1
Maximal free surface
height as function
of time
Remarks:
-Good height
-Solitary wave speed
slightly underestimated
Results:
2. Solitary wave
Calculation of 2000 time step of 50ms, courant max : ~0.1
Global relative volume
as function of time
Remarks:
-Loss of volume…
-0,014% per hour
Results:
3. Naca hydrofoil
Test case from “The breaking and non-breaking wave resistance of a twodimensional hydrofoil” by JAMES H. DUNCAN
Steady test case
Results:
3. Naca hydrofoil
Results:
3. Naca hydrofoil
Experimental surface height (cm) as
function of horizontal distance (cm)
My results… so far
Results:
4. Submerged cylinder
Test case from “Nonlinear forces on a horizontal cylinder beneath waves”, by JOHN
R. CHAPLIN
Problems to be solved
Energy and volume losses
ALE module
 negative volume… calculation aborted
Problem of period for the standing wave (STREAM has the
right period!)
Any comments or ideas about my work ?!?