sanation
Mechanical
- Jun 1, 2007
- 1
Hi,
I'm a relatively new Floworks user and am having some trouble setting pressure boundary conditions. The goal is to analyze the effects of a sampler pulling air in at a much lower speed than the air it is sampling from. Thus far, I have set up rectangular box (0.1m x 0.03m x 0.03m) to simulate ideal outside conditions. It has a velocity inlet at one end of the long side, a total pressure boundary (set to the total pressure based on the inlet velocity) at the opposite end and ideal walls on the other 4 sides. We are using very ideal conditions: laminar flow, non-fully developed tube flow for the inlet, and no gravity. I ran tests just to check this setup was ok before moving on, and realized that my pressure boundary was not staying at the pressure I set it to. When I run a case with the inlet set to 50m/s and the total pressure at 102809Pa, the pressure at the boundary begin a the right pressure, but at the end (about 0.02s real time) don't get over 101500Pa. The pressure in the majority of the domain is 101378-101398. And as the flow gets closer the pressure boundary, the pressure begins to decrease in the corners. I guess I just don't understand why the pressure boundary or the inlet don't have pressures near the total pressure? Is my box not long enough for the velocity? I assumed since our conditions are so ideal, the size wouldn't be a factor. I also assumed that since it was so short, the flow would reach steady state pretty soon. Should I let it run out longer? Any suggestions would be greatly appreciated!
Thanks,
Shelley
I'm a relatively new Floworks user and am having some trouble setting pressure boundary conditions. The goal is to analyze the effects of a sampler pulling air in at a much lower speed than the air it is sampling from. Thus far, I have set up rectangular box (0.1m x 0.03m x 0.03m) to simulate ideal outside conditions. It has a velocity inlet at one end of the long side, a total pressure boundary (set to the total pressure based on the inlet velocity) at the opposite end and ideal walls on the other 4 sides. We are using very ideal conditions: laminar flow, non-fully developed tube flow for the inlet, and no gravity. I ran tests just to check this setup was ok before moving on, and realized that my pressure boundary was not staying at the pressure I set it to. When I run a case with the inlet set to 50m/s and the total pressure at 102809Pa, the pressure at the boundary begin a the right pressure, but at the end (about 0.02s real time) don't get over 101500Pa. The pressure in the majority of the domain is 101378-101398. And as the flow gets closer the pressure boundary, the pressure begins to decrease in the corners. I guess I just don't understand why the pressure boundary or the inlet don't have pressures near the total pressure? Is my box not long enough for the velocity? I assumed since our conditions are so ideal, the size wouldn't be a factor. I also assumed that since it was so short, the flow would reach steady state pretty soon. Should I let it run out longer? Any suggestions would be greatly appreciated!
Thanks,
Shelley