Lecture 8 Flashcards
Automotive Wind Tunnels and Measurement Techniques (20 cards)
What are the main differences between aeronautical wind tunnels and automotive wind tunnels?
Aeronautical wind tunnels have ideal flow condition valid for high altitude operation. This includes uniform flow field and low turbulence. Automotive wind tunnels require ground simulation.
What are the effects called that happen on a vehicle in a wind tunnel?
Blockage effects
What are the things that can be tested in a wind tunnel?
Aerodynamic forces and momentum, yaw conditions, cooling performance, local flow field, contamination, aeroacoustics, climate effects
What are the two wind tunnel types?
Closed/return, open/no return
Which type is the göttingen vs the eiffel wind tunnel?
closed/return (göttingen), open/no return(eiffel)
Which wind tunnel type is most common?
Göttingen
Advantages/Disadvantages: Göttingen type?
Advantages: uses the same volume of air, lower losses (guiding vanes), good for climate testing
Disadvantages: expensive, needs temperature control
Advantages/Disadvantages: Eiffel type?
Advantages: Cheaper, less space, no cooling needed
Disadvantages: larger losses, higher operating costs, dependent on weather control and surroundings
What are the main components of a wind tunnel?
Inlet, nozzle, collector, diffuser, fan
What does the inlet and nozzle do?
accelerate flow, equalize velocity over nozzle area, reduction in longitudinal turbulence, measure flow velocity
What does the collector do?
Collects the wake flow behind the vehicle
What does the diffuser do?
Improves energy balance within the wind tunnel.
What does the fan do?
Drives the flow
What are the five different designs for the test section?
Open, closed, slotted wall, streamlined, adaptive
Advantages/Disadvantages: Open test section?
Advantages: Accessibility, test conditions closer to open road (no blockage effects)
Disadvantages: Limitation in test section length
Advantages/Disadvantages: Closed test section?
Advantages: No strong shear layer, less losses, conceptually simple, allows for longer test section, known blockage correction method
Disadvantages: High levels of blockage, wall-compress streamlines
Advantages/Disadvantages: Slotted wall test section?
Advantages: Allow for long test section, less blockage sensitivity than closed wall
Disadvantages: Unclear blockage correction procedures
What are the four effects to correct for open jet?
Jet expansion, jet deflection, nozzle blockage, collector blockage
What is the typical blockage in tunnels?
5-9%
