
Re: flow simulation of gas filling a vacuum vessel. is it possible?
Jared Conway Sep 4, 2014 4:39 PM (in response to Francesco Zuddas)have you checked the soldiworks KB? there is an article specific about filling and evacuation.
very involved calculation
needs to be time dependent
actually according to the article it says there is info in the help:
Here is what the Online Help says about it:
Calculations of pressurized tank evacuation through small orifices or exhaust system may
require long computation time due to compression and rarefaction waves which appear in the
fluid region. Sonic and supersonic waves propagate through the fluid region. The code tries
to simulate the wave movement choosing small time steps for the numerical integration of
the governing equations. In many cases the characteristic time of the evacuation process
(te) is much larger then the characteristic time of the compression/rarefaction wave
movements (tw): te>>tw. At this condition, the global gas parameters inside the tank are
changed weakly in comparison with the dynamic gas parameters so evacuation process can
be considered as quasistationary.
Such evacuation process can be calculated with Flow Simulation as a transient task but it
may be very time consuming. However, you can estimate gas parameters inside the tank
versus time using the Calculator tool in Flow Simulation by the given initial parameter values
and the discharge coefficient. The discharge coefficient can be obtained from the calculation
as a ratio of the real (obtained from the analysis) mass flow rate to the ideal mass flow rate
ratio for the effective throat area of your exhaust system. To obtain the ideal mass flow rate,
the value of the pressure and temperature inside the tank is needed. The recommended
strategy for solving the evacuation tasks is to run an analysis in Flow Simulation until the
exhaust jet is formed. Next use the gas parameters from the Flow Simulation analysis and
calculate the discharge coefficient. Finally estimate the gas parameters by using the
gasdynamic Calculator tool provided in Flow Simulation
from personal experience, we did a tank evacuation and it was very difficult to get it to solve reasonably
you should really decide what you're going to gain from the simulation