Yet in the A2 wind tunnel
http://www.a2wt.com/
cars use about 1/3 of the tunnel width and height
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How do they avoid interference from the tunnel walls?
I read somewhere that they adjust the tunnel ceiling height or shape to the shape of the vehicle.
the F1 Jaguar stalled its rear wing on track at an AoA that the wind tunnel said was just fine (ask Eddie Irvine)n_anirudh wrote:a) There will be higher blockage and this will affect Cd Cl values
Did CFD say the wing would not stall as well?Tommy Cookers wrote:the F1 Jaguar stalled its rear wing on track at an AoA that the wind tunnel said was just fine (ask Eddie Irvine)n_anirudh wrote:a) There will be higher blockage and this will affect Cd Cl values
this was because the tunnel was too small for the model, ie just too small
naval aircraft operate unusually close to the stall in carrier approaches
public domain sources could show which ones have had problems consistent with deficiencies in tunnel size and Re number
the wind tunnel is a design tool whose cost, value and availability attributes may be competing with those of other design tools
Did you mean with a static floor and WITHOUT boundary layer suction?gixxer_drew wrote:With a static floor and boundary suction, everything is a generalization anyway. You can still go faster from what you learn. What level are you developing at?
You designing front diffusers or cooling systems? Big difference in what you need to go faster at the end of the day. Taking an axe to your aero or a scalpel?
I think that rule of thumb comes from aircraft stuff for high downforce ground vehicles I think its really defined by the upwash. Sometimes you need a huge vertical upwash area like what was being discussed in the monaco tunnel thread. The sidepods can be tricky as well with requiring a lot of width to the tunnel as well and it all depends on the designs in play. I think this is where most teams get into trouble with the tunnels. Everything is riding some engineering compromise and the design changes but the tunnel does not...P.S. wrote:Usually you should not exceed 5% blockage in the test section. Otherwise it will effect the simulation. But this rule leads to a very large wind tunnel with large costs. So there is a pretty big interest in decreasing the wind tunnel size.
Lots of wind tunnels for cars are build with a blockage of 10% still getting decent simulation results.
F1 wind tunnels are designed large enough staying inside the 5% limit to avoid any risk.
Probably the idea behind the A2 is to adapt the tunnel walls in the same way the air would become displaced in free stream. Some smart guys have shown in the 80s or so, that it is possible to get the same aerodynamic results increasing the blockage up to 20% with this technic. But you need to adapt the walls for every car apart if you want to be very correct.
If they don´t adapt the tunnel walls for each car properly, the error is probably not that big. I would say, especially if you have a small budget, this tunnel can be a nice choice testing full scale stuff.
Jaguar was 2004, with Irvine it was 2002. There was CFD, but it wasn't employed at such a scale as it is now.g-force_addict wrote:Did CFD say the wing would not stall as well?Tommy Cookers wrote:the F1 Jaguar stalled its rear wing on track at an AoA that the wind tunnel said was just fine (ask Eddie Irvine)n_anirudh wrote:a) There will be higher blockage and this will affect Cd Cl values
this was because the tunnel was too small for the model, ie just too small
I guess it did as CFD usually precedes wind tunnel testing.
Would the close placed walls make it worse at a higher speed?riff_raff wrote:According to the A2 website, the tunnel is only capable of producing airflow velocity of 85mph.