QUESTION - 2: You are tasked with performing a wind tunnel test on a new airfoil design. Outline the experimental setup , including the type of wind tunnel, instrumentation , and the test procedure you would use . How would you ensure that the results are accurate and reliable?

### Experimental Setup for Wind Tunnel Test on a New Airfoil Design<br /><br />#### 1. Type of Wind Tunnel<br />- **Subsonic Wind Tunnel**: For most airfoil tests, a subsonic wind tunnel is appropriate as it can simulate the airflow conditions experienced by the airfoil at typical operating speeds.<br />- **Closed-Circuit Wind Tunnel**: This type of wind tunnel recirculates the air, providing more stable and controlled test conditions.<br /><br />#### 2. Instrumentation<br />- **Force Balance System**: To measure lift, drag, and moment forces acting on the airfoil.<br />- **Pressure Taps and Transducers**: Distributed along the surface of the airfoil to measure pressure distribution.<br />- **Hot-Wire Anemometry**: To measure the velocity of the airflow in the boundary layer.<br />- **Smoke or Laser Sheet Visualization**: To visualize the flow patterns around the airfoil.<br />- **Angle of Attack Mechanism**: To adjust and accurately measure the angle of attack of the airfoil.<br />- **Data Acquisition System (DAQ)**: To collect and record data from all sensors and instruments.<br /><br />#### 3. Test Procedure<br />1. **Preparation**<br /> - Ensure the wind tunnel and all instrumentation are calibrated and functioning correctly.<br /> - Mount the airfoil model securely in the test section of the wind tunnel.<br /> - Connect all sensors and verify their operation through the DAQ system.<br /><br />2. **Baseline Measurements**<br /> - Run the wind tunnel without the airfoil to establish baseline readings for temperature, pressure, and humidity.<br /><br />3. **Initial Testing**<br /> - Set the wind tunnel to the desired speed (Reynolds number) for the test.<br /> - Gradually increase the angle of attack from zero to the stall angle, recording data at each increment.<br /> - Measure lift, drag, and moment forces using the force balance system.<br /> - Record pressure distribution using pressure taps and transducers.<br /> - Use hot-wire anemometry to measure boundary layer characteristics.<br /><br />4. **Flow Visualization**<br /> - Conduct smoke or laser sheet visualization tests to observe flow separation, vortex formation, and other flow phenomena around the airfoil.<br /><br />5. **Repeatability Tests**<br /> - Repeat the tests multiple times to ensure consistency and repeatability of the results.<br /><br />6. **Data Analysis**<br /> - Analyze the collected data to determine aerodynamic coefficients such as lift coefficient (Cl), drag coefficient (Cd), and moment coefficient (Cm).<br /> - Compare experimental results with theoretical predictions and computational simulations if available.<br /><br />#### Ensuring Accuracy and Reliability<br />- **Calibration**: Regularly calibrate all instruments and sensors before and after tests.<br />- **Environmental Control**: Maintain consistent environmental conditions (temperature, pressure, humidity) within the wind tunnel.<br />- **Model Precision**: Ensure the airfoil model is manufactured to precise specifications and free from defects.<br />- **Data Averaging**: Use data averaging techniques to minimize random errors and fluctuations in measurements.<br />- **Error Analysis**: Perform a thorough error analysis to identify and quantify potential sources of error.<br />- **Peer Review**: Have the experimental setup and procedures reviewed by experts to identify any potential issues or improvements.<br />- **Documentation**: Keep detailed records of all test conditions, procedures, and results for future reference and validation.<br /><br />By following these steps and maintaining rigorous standards throughout the testing process, you can ensure that the results of the wind tunnel test on the new airfoil design are accurate and reliable.