[dmaz]

Hello everybody, I'm a university student and I'm trying to simulate a ship hull on a water channel in Fluent.
I have realized the mesh in Gambit and it seems to have a good quality.
My problem is how to set the parameters and the simulation in Fluent 14.
I read I have to use a VOF model for a simulation concerning both the water and the air.
I did the follow commands but you can see the results in figure 2: the water and the air seems to be mixed..

My commands in Fluent14:

• import the gambit mesh
• set a steady solver
• set the VOF model - two phases - implicit scheme - open channel flow
• set the model viscous k-epsilon (2eq)
• define materials - water liquid
• define phases - phase 1=air and phase 2 = water liquid.
• define operating conditions - gravity=-9.81 m/s2 and specified operating density.

regarding the boundary conditions they are reported in figure1. I used symmetry to simulate half fluid volume, wall on the hull, ocean floor and on the right surfaces of the fluid volume, pressure outlet for air in the air surfaces and velocity_inlet for the entrance surface of water. For the water pressure outlet, I set an udf. It describes the idrostatic pressure depending by the z-coordinate :

• define-user defined-functions-interpreted and chose the following Udf:

/************************************************** *********************
UDF for specifying steady-state parabolic pressure profile boundary
profile for a turbine vane
************************************************** **********************/
#include "udf.h"
DEFINE_PROFILE(pressure_profile,thread,index)
{
real x[ND_ND];
real z;
face_t f;
begin_f_loop(f,thread)
{
F_CENTROID(x,f,thread);
z=x[2];
F_PROFILE(f,thread,index) = 998.2*9.81*(-z);
}
end_f_loop(f,thread)
}

• set the boundary condition for the water outlet: boundary conditions - pressure_oultet_water. phase: mixture. edit - I chose the udf_pressure_profile
• phase water - multiphase - backflow volume fraction=1
• boundary conditions - pressure_oultet_air: phase:mixture - gauge pressure=0
• boundary conditions - velocity_inlet_air: phase:mixture magnitude normal to bound velocity magnitude:2m/s
• phase water - multiphase-backflow volume fraction=1

now I set the position of the water when the simulation start

• adapt-region and I insert the values for the volume of water. then I press mark.
• solve -controls-solution: I chose the PISO model and all the first order equations
• solve monitors-residual all the residual set to 10^-5
• solve initialize - init
• solve initialize - patch - water

where I'm wrong? Thanks to everyone will help me!

BC-hull.jpg

results.png

[dmaz]

Anyone can help me?

[zooid]

I have a similar problem, can anyone help please?

[Grigor Nikolov]

http://www.youtube.com/watch?v=y4Sd__Viw-0