|
[Sponsors] |
July 4, 2012, 11:55 |
Simulating aircraft at High Altitude
|
#1 |
New Member
Join Date: Jun 2012
Posts: 3
Rep Power: 14 |
Hello everyone, this is my first post and is concerning a simulation on an airplane meshed in GAMBIT. I would really appreciate some feedback about my values and help me with my mistakes.
My parameters are these: - 10.000 m altitude - Pressure (10k m) = 26437 Pa - Density (10k m) = 0.4161 kg/m3 - Velocity (velocity-inlet): variable - Temperature (10k m)= 223.15 K - Viscosity (10k m)= 1.3067e-05 I do not want to explain my mesh otherwise would take ages, just say it is formed by a large cube involving a cylinder and this involving the aircraft. The boundary conditions are velocity-inlet, interior (for the cylinder), wall (aircraft and cube's faces) and pressure-outlet. Solver parameters: - Node-gauss based - Density-Based - k-omega SST - PRESTO - Second-Order Upwind each parameter I set Pressure to 0 Pa and when asked, Gauge Pressure to 26437, is it correct? In Materials section, both density and viscosity are constant values. Reference Values: - Area: here is where I have more questions, so far I have been using the projected area (1,0,0) in X-axis, which is the frontal view of the aircraft, with 0.01m of error. - Length: I have been using the longitudinal length of the aircraft, along the y-axis, but I'm not sure about this. I think these are the main parameters of the simulation. I would appreciate any help or feedback from anybody, just need to be sure that I am doing the right procedure, or at least close to it. Many thanks in advance |
|
July 4, 2012, 12:16 |
|
#2 |
Super Moderator
Alex
Join Date: Jun 2012
Location: Germany
Posts: 3,427
Rep Power: 49 |
Why do you use a "wall" boundary condition on the faces of the cube?
A slip-wall (symmetry) would be better in my opinion. Since your aircraft might travel at a high speed, effects of compressibility may be important. So you should not use constant values for your fluid properties. |
|
July 4, 2012, 13:01 |
|
#3 |
New Member
Join Date: Jun 2012
Posts: 3
Rep Power: 14 |
When you say symmetry, you mean the four faces of the tunnel (cube), don't you? I will try this solution, thanks a lot!
On the other hand, the aircraft is not meant to fly at high velocities, just up to 200 Km/h or so. However, flying below 200 Km/h I struggle to balance the Weight with the net Lift force the aircraft generates. |
|
July 5, 2012, 07:16 |
|
#4 |
New Member
Join Date: Jun 2012
Posts: 3
Rep Power: 14 |
In addition, when fluent starts iterating, it says Reversed flow in 1000 cells in pressure-outlet, and as iteration goes on it decreases until the warning does not appear anymore.
Plus, if I try Ideal-gas, hence Energy equation = On, Fluent shows another warning saying this settings are not appropriate for Velocity-inlet boundary conditions. Why is that happening? Thanks in advance |
|
July 5, 2012, 08:39 |
|
#5 |
Super Moderator
Alex
Join Date: Jun 2012
Location: Germany
Posts: 3,427
Rep Power: 49 |
For the warnings indicating reversed flow at outlet cells:
Initialize the velocity field with the inlet velocity. Note that this will only speed up convergence. If the warnings disappear after a few iterations, the simulation is still valid. For the ideal gas calculations, try using a mass-flow boundary condition instead of the velocity inlet. |
|
Tags |
aircraft, density, projected areas, reference values, viscosity models |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Simulating a high pressure flow through a valve | Kromagnsss | FLUENT | 8 | July 2, 2010 06:20 |
simulating high Ra and Pr in pipe | f_mahmood | FLUENT | 0 | January 2, 2010 18:50 |
Simulating high pressure burst flow | jakjak | CFX | 2 | November 21, 2007 22:06 |
High Aspect Ratio elements | Flavio | CFX | 2 | November 24, 2006 13:01 |
Multicomponent fluid | Andrea | CFX | 2 | October 11, 2004 06:12 |