|
[Sponsors] |
March 7, 2018, 07:04 |
stagnation pressure on a water droplet
|
#1 |
New Member
Hussain
Join Date: Mar 2018
Posts: 4
Rep Power: 8 |
Hi,
I am modeling a free falling of a water droplet through air. the issue is that i want to estimate the deformation rate and for that it seems like i need to calculate the stagnation pressure. by looking at the equation (wiki) it is not clear to me what values to choose. for example should i choose the density of air or density of water droplet in that equation, similarly what velocity should i consider. is it the velocity of water droplet or the air? i appreciate if you could help me route me to a correct forum. thanks! Best regards Hussain |
|
March 7, 2018, 07:24 |
|
#2 |
Senior Member
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 744
Rep Power: 15 |
You have to use the density of the air. Formula given in textbooks are valid for solid bodies too, which don't deform.
The velocity is the relative one between the droplet and the air. It doesn't play any role if the air is moving or the droplet. It is the difference hat counts.
__________________
Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) |
|
March 7, 2018, 08:19 |
|
#3 |
New Member
Hussain
Join Date: Mar 2018
Posts: 4
Rep Power: 8 |
HI Pilz
Thanks for a quick reply. how about the static pressure in the equation. can i just use the atmospheric pressure? Regards Hussain |
|
March 7, 2018, 08:32 |
|
#4 |
Senior Member
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 744
Rep Power: 15 |
> can i just use the atmospheric pressure?
I think so. I need your reference to check this.
__________________
Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) |
|
March 7, 2018, 08:40 |
|
#5 |
New Member
Hussain
Join Date: Mar 2018
Posts: 4
Rep Power: 8 |
The droplet is falling through the air at atmospheric pressure of 1 atm. do you have any reading suggestions regarding my problem because i want to estimate the deformation rate of the droplet while it is falling?
thanks! Regards Hussain.. |
|
March 7, 2018, 09:27 |
|
#6 |
Senior Member
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 744
Rep Power: 15 |
In this case I would simulate an aerial flow around the droplet. With changing the speed the droplet gets deformed (more or less slightly), but the cf values change fast. Your solution is the one where the drag equals the gravity.
__________________
Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) |
|
March 7, 2018, 09:55 |
|
#7 |
New Member
Hussain
Join Date: Mar 2018
Posts: 4
Rep Power: 8 |
Thank you Pilz. I will try to dig down more on that suggestion of yours.
regards Mazhar.. |
|
Tags |
bernoulli's equation, droplet simulation, falling drops, stagnation pressure |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Periodic flow using Cyclic - comparison with Fluent | nusivares | OpenFOAM Running, Solving & CFD | 30 | December 12, 2017 06:35 |
How to patch a water droplet with smooth surface? | Hossein1 | FLUENT | 0 | January 13, 2017 10:25 |
CFX Solver stopped with error when requested for backup during solver running | Mfaizan | CFX | 40 | May 13, 2016 07:50 |
stagnation pressure boundary problem | mbgnfrx2 | STAR-CD | 2 | November 26, 2012 00:55 |
what the result is negatif pressure at inlet | chong chee nan | FLUENT | 0 | December 29, 2001 06:13 |