hi i trying to heat a tank filled with water. boudary condition: bottom wall temperature 500K, water temperature 300K, pressure of water 1013hPa. Iterations doing well, residuals too but after iterations density doesn`t change. Why. In real density of water change with temperature isn`t ? so why it doesn`t change in my model. Im using: unstady, VOF with body implict..., g=9.81m2/s. time step size 0,001s, number of time steps 100000 regards

You have to explicitly include the density function of temperature ...in the material data.....

Fluent will not change it if you use a fixed density!!

Ok Thank you. I`ve already made an UDF and now everything seems to be ok. regards Grzesiek PS. Mabby you know what to do to have a specific heat changes with temperature changes. I`ve heard that "cp" is the only properties which can not be defined by UDF and must be constant. But what to do when it is a function of temperature and concentration ?

Well you are right, it is strange that C_p cannot be modified with an UDF...

but you can use a piecewise-linear function of temperature...or polynomial function of temperature....I am sure you can find what you need