Hardware overview¶
The wind tunnel is an open-circuit, low-speed facility. Air is drawn from the room through the intake, accelerated through the contraction, passed across the test section, and exhausted to the back of the lab. A three-phase induction motor drives the fan; an ABB ACH550 VFD regulates motor speed; a Modbus/TCP fieldbus connects the lab PC to the VFD; the lab PC runs the control software and the data acquisition.
Airflow path¶
flowchart LR
IN[Intake<br/>+ smoke generator] --> CN[Contraction] --> TS[Test section<br/>+ laser sheet] --> DF[Diffuser] --> FN[Fan / motor] --> EX[Exhaust<br/>blocked off by band saw]The smoke generator sits near the intake so its plume is entrained into the main airflow. The laser sheet illuminates the test section from the side. The fan and motor are downstream of the test section, so airflow blockage from a loose model immediately loads the motor; this is one reason why the pre-run checklist is non-negotiable.
Electrical & control chain¶
flowchart LR
MAINS[Building 480 V three-phase] --> SW[Main switch]
SW --> VFD[ABB ACH550 VFD<br/>option slot 1: RETA-01]
VFD --> MOT[3-phase induction motor]
MOT --> FAN[Tunnel fan]
PC[Lab PC<br/>Win11 + WSL2] -->|USB| ETH[Ethernet 4<br/>Realtek 2.5GbE<br/>192.168.50.100]
ETH -->|Cat 5e| RETA[RETA-01<br/>192.168.50.10]
RETA -.->|internal bus| VFD
PC -->|USB| CDAQ[NI cDAQ chassis]
CDAQ --> S1[NI-9203 4–20 mA]
CDAQ --> S2[NI-9215 ±10 V]
CDAQ --> S3[NI-9237 bridge]The main switch is the only physical disconnect upstream of the drive. Everything to the right of SW is energized once the switch is closed.
Network topology¶
The lab PC's onboard Ethernet talks to the campus network. A separate USB-to-Ethernet adapter (the operating system labels it Ethernet 4, MAC 6C:1F:F7:C3:96:59) carries the private VFD network on a static 192.168.50.100/24. The RETA-01 inside the drive holds 192.168.50.10/24. Both are configured to use the ABB Drives Modbus profile on port 502, unit ID 1.
The reason for the separate adapter is that the campus network's DHCP would assign an address in a different subnet and the RETA-01 has no route there. Treating the VFD network as a separate physical link with a static address means there is no DHCP race, no campus-network firewall, and no risk of someone else's traffic confusing the drive.
Components at a glance¶
| Component | Make / model | Purpose | Manual page |
|---|---|---|---|
| Main switch | Building install | Mains disconnect | Test section & exhaust |
| VFD | ABB ACH550 | Speed regulation of the motor | Motor & VFD |
| Fieldbus adapter | ABB RETA-01 | Ethernet → drive internal bus | Fieldbus |
| Motor | 3-phase induction, nameplate ~880 RPM at 60 Hz | Drives the fan | Motor & VFD |
| Lab PC | Windows 11 with WSL2 sidecar | Control + DAQ host | Control PC |
| Ethernet 4 | Realtek USB 2.5 GbE | VFD network adapter | Control PC |
| cDAQ chassis | NI compactDAQ | Frame for the DAQ modules | Data acquisition |
| NI-9203 | 8-channel, 4–20 mA current input | Pressure transducers | Data acquisition |
| NI-9215 | 4-channel ±10 V voltage input | Angle, miscellaneous voltages | Data acquisition |
| NI-9237 | 4-channel bridge input | PGB sting force balance | Data acquisition |
| Laser | 5 mW Class 2 + glass-rod sheet former | Flow visualization | Laser & smoke |
| Smoke generator | Glycol-based, wired remote | Flow visualization | Laser & smoke |
Physical layout in the lab¶
The lab is one rectangular room. The computer station is at one end (PC, smoke generator remote, ADCL WinSoft on screen); the wind tunnel runs the length of the room with the intake near the computer station and the exhaust at the far wall. The VFD enclosure is mounted on the wall next to the tunnel. The main switch is mounted within reach of the computer station so the operator can disconnect mains without moving away from the controls.
The exhaust opening at the far wall is blocked by a parked band saw to deter people from walking into the airflow path. The band saw is there as a physical barrier, not as a tool to be used during a tunnel run — it must stay in place while the tunnel is energized.
For high-resolution photos of each station, see the dedicated pages: