- #1
Bavier
- 5
- 0
Hi everyone,
I'm doing a simulation and need some help.
A capillary which is closed on both ends with the length l (x=0 to x=l), with a radius R and the volume pi*R^2*l is dropped on a parachut at the time t=0 from a hight h above ground.
At t=0 the pressure inside the capillary is p_i0 (this should be smaller than the ambient pressure p_a at this particular hight). Also at t=0 one side of the capillary is opened (the other side will remain closed). Now due the pressure difference between ambient and inner pressure (p_a - p_i0) a volume flow of air flows in x-direction into the capillary. We can assume laminar flow of the compressible gas.
I tried to use Hagen-Poisuille (for compressible fluids) to calculate the volume flow through the capillary due to the pressure difference. However the pressure difference and thereby the volume flow are time and position dependent, i.e. that the ambient pressure is changing with hight (can be easily calculated with the barometric formula) and the inner pressure and the density of the air inside the capillary will also change. There will be a build up of a back pressure.
Like I said, my goal is to simulate this process, i.e. a time and positon dependent (x-value in the capillary) function of the volume flow.
It's really difficult and I'm not a physicist nor I'm an engineer.
Is using Hagen-Poisuille the right choice? The big problem that I have is that one side is closed.
Do you have any imputs?
Many thanks
I'm doing a simulation and need some help.
A capillary which is closed on both ends with the length l (x=0 to x=l), with a radius R and the volume pi*R^2*l is dropped on a parachut at the time t=0 from a hight h above ground.
At t=0 the pressure inside the capillary is p_i0 (this should be smaller than the ambient pressure p_a at this particular hight). Also at t=0 one side of the capillary is opened (the other side will remain closed). Now due the pressure difference between ambient and inner pressure (p_a - p_i0) a volume flow of air flows in x-direction into the capillary. We can assume laminar flow of the compressible gas.
I tried to use Hagen-Poisuille (for compressible fluids) to calculate the volume flow through the capillary due to the pressure difference. However the pressure difference and thereby the volume flow are time and position dependent, i.e. that the ambient pressure is changing with hight (can be easily calculated with the barometric formula) and the inner pressure and the density of the air inside the capillary will also change. There will be a build up of a back pressure.
Like I said, my goal is to simulate this process, i.e. a time and positon dependent (x-value in the capillary) function of the volume flow.
It's really difficult and I'm not a physicist nor I'm an engineer.
Is using Hagen-Poisuille the right choice? The big problem that I have is that one side is closed.
Do you have any imputs?
Many thanks