[Nitisha274]

I am trying to measure the film thickness of deposited fuel after spray impingement. Converge does give me an output file for film mass and I can see a parameter called film height while post processing, but can I know how is film height being calculated?. And for spray in ambient conditions film_scrape gives me 0 value for all time step, and film.out, film_accum_plus is giving me same values over the time. What does that mean?

[Yaju]

Hi Nitisha,

film_scrape.out gives the amount of film being scraped by a boundary. For example: when a piston boundary is moving in an engine, it might scrape some of the film mass from the cylinder wall. For a simulation with non-moving boundaries, the film scrape value will be 0.

film.out gives the total film mass at any given time. film_accum_plus.out gives the total parcel mass that has hit the wall boundaries and remained on it (i.e. parcel mass that has hit the boundary - parcel mass that has splashed and rebounded).

If there is no film evaporation going on, the values in film_accum_plus.out and film.out will be the same. With evaporation the value in film.out will start to decrease. So, the difference in these files can give you an idea on how much of the film mass has been converted to gas phase.


The film height in each boundary cells is calculated as a function of: film mass in the cell, temperature, and wall face area of the boundary cell. The temperature of the film parcel gives us its density, this density and film mass will give us the volume of the film in a cell. The film volume divided by the wall face area gives us the film height.

[Yaju]

Hi Nitisha,

film_scrap.out gives the amount of film mass that is scraped by a boundary. For example: when piston is moving in an engine, it might scrape off mass from the cylinder walls. If there are no moving boundaries in the simulation, the entries in film_scrap.out will be 0.

film_accum_plus.out give the total amount of parcel mass that has hit the boundaries and remained on it (i.e parcel mass hit on the surface - parcel mass rebounded or splashed from the surface). Whereas, film.out gives the total film mass present on the wall boundaries at any given time. During the simulation some of the film mass is converted into gas phase. You can think of the difference between film_accum_plus.out and film.out as the mass that has been converted to gas phase. For your case none of the film parcels are getting converted to gas phase, hence the values in film.out and film_accum_plus.out are the same.

[Yaju]

The film height in a cell is calculated as a function of: film mass in a boundary cell, temperature of the film parcels, and the wall face area of the boundary cell. The film parcel temperature will give us the density of the film parcels, using this film density and film mass we can get the film volume. The film volume divided by the wall face area will give us the film height in a boundary cell.

[Nitisha274]

Thanks a lot. This helps a lot.

[Nitisha274]

Thanks a lot. This helps a lot. However does the film.out include the mass that has been splashed or rebounded? Because in my case both film.out and film_accum_plus.out has the same mass, does that mean no mass is being is rebounded or splashed. But in the post processing I see rebound.

[Yaju]

None of these files include the rebounded and splashed mass.

I am sorry if you misunderstood my earlier statement. film_accum_plus.out file gives the parcel mass that has reached the boundary and remained on it (i.e., mass that has not splashed and rebounded).

film_accum.out lists all the mass that has made contact with a boundary (this will include rebounded and splashed mass as well).

[Nitisha274]

Ok. I got it now. Thanks a lot.