SITIS Archives - Topic Details
Program:  SBIR
Topic Num:  AF071-345 (AirForce)
Title:  Near-Field Velocity Measurement System for Wind Tunnel Testing
Research & Technical Areas:  Air Platform, Sensors, Electronics

  Objective:  Develop a system for non-intrusive measurements of 3-dimensional air-flow velocity components near the surface of wind tunnel models.
  Description:  In wind tunnel tests there are requirements to assess the aerodynamic performance of weapons systems during the system development cycle. Analysis and evaluation tools that can validate system performance and/or identify the source of anomalous test results early in the development cycle have the potential to save millions of dollars by eliminating costly redesign later in the program. Characterization of test article three-dimensional fluctuating boundary layers is important in the evaluation and validation of the computational tools that are used to design and predict the full-scale performance of the system. Complex three-dimensional, vortex-dominated, flow separation phenomena are not well understood. Improvements in CFD capabilities allow limited prediction of such flows, but accurate experimental data are required for continued development and validation of computational methods. A robust system is required that can simultaneously measure three components of velocity in the near-field of a wind tunnel model. The system should be capable of measuring high-spatial-resolution velocity profiles (0 to 1500 ft/sec ± 10 ft/sec for either component) perpendicular to the model surface over a range from the model surface to at least 1.0-in from the surface. The system should be small enough to fit inside a typical model or carried by a traversing mechanism internal to the model. The system must be able to operate at pressures from 200 psf to 4000 psf and temperatures up to 140 deg F. The system control and data acquisition/processing must be remotely located up to 300 ft from the measurement location; noting that space for and routing of cables can be an issue.

  PHASE I: Demonstrate the feasibility of a system to simultaneously measure three components of velocity.
  
  PHASE II: Develop and demonstrate a prototype system that can simultaneously measure the three components of velocity.

  DUAL USE COMMERCIALIZATION: Military application: Potential military applications include incorporation of these systems into preflight test facilities and/or flight test programs to meet test and evaluation requirements for weapons systems. Commercial application: The measurement technique can be applied to any other industry that requires monitoring and/or improving the efficiency of fluid flow systems.

  References:  1. Gwibo Byun, Semih M Ölçmen and Roger L Simpson, “A Miniature Laser-Doppler Velocimeter for Simultaneous Three-Velocity-Component Measurements,” Measurement Science and Technology, Vol. 15 (2004), 2075–2082. 2. Gwibo Byun and Roger L. Simpson, “Structure of Three-Dimensional Separated Flow on an Axisymmetric Bump,” AIAA 2005-113, 43rd AIAA Aerospace Sciences Meeting and Exhibit 10 - 13 January, 2005, Reno, NV. 3. Mouaze, D. and Belorgey, P., “Internally Mounted Laser-Doppler-Anemometry System for Boundary Layer Measurement” Exp. Fluids 30 111–114, 2001.

Keywords:  Velocimetry, LDV, LDA. Miniature sensors, Non-intrusive, Turbulence, Wind Tunnel

Additional Information, Corrections, References, etc:
1. At what time increments is the data desired? It is to be averaged over a small time period, or instantaneous?

Each point in a profile will require a number of samples to be averaged (approx 1000). It is expected that this should take not more than a couple of seconds. The time required to measure a profile will depend on the number of points and the time required moving to the next position in the profile. Assuming 25 to 30 points over a distance of 1 inch, the time to acquire the data should be no more than 3 or 4 minutes.

2. Are only the U,V,W components wanted, or are other turbulent quantities(k, RMS, vorticity) desirable as well?

The 3 velocity components are definitely needed; however, the turbulence quantities are desirable.

3. What is the size of 'a typical model'?

The models that this system would be used in would be at least 6 inches in diameter and 24 inches long.

4. Are some modifications to the model allowable?

Yes, in certain cases. The system will be used on specific tests and will require advanced preparation. In most cases, it will be used if the customer has a specific question about the flow field or to provide validation for CFD computations. The system will require a window on the model surface to make the measurement. The window and the opening will be test peculiar modifications to the model. The system needs to be easily removable from the model and installed in another one.

5. At what spatial increments are measurements desired?

This will likely be customer dependant. The spacing between measurement points will probably not be uniform over profile. The increment can be as small as 0.001 inches near the model surface and as large as 0.1 inches at distances greater than 0.5 inches from the surface. It will be important to know the distance from the surface to the measurement location with an uncertainty that is less than 0.001 inches.
1. At what time increments is the data desired? It is to be averaged over a small time period, or instantaneous?

Each point in a profile will require a number of samples to be averaged (approx 1000). It is expected that this should take not more than a couple of seconds. The time required to measure a profile will depend on the number of points and the time required moving to the next position in the profile. Assuming 25 to 30 points over a distance of 1 inch, the time to acquire the data should be no more than 3 or 4 minutes.

2. Are only the U,V,W components wanted, or are other turbulent quantities(k, RMS, vorticity) desirable as well?

The 3 velocity components are definitely needed; however, the turbulence quantities are desirable.

3. What is the size of 'a typical model'?

The models that this system would be used in would be at least 6 inches in diameter and 24 inches long.

4. Are some modifications to the model allowable?

Yes, in certain cases. The system will be used on specific tests and will require advanced preparation. In most cases, it will be used if the customer has a specific question about the flow field or to provide validation for CFD computations. The system will require a window on the model surface to make the measurement. The window and the opening will be test peculiar modifications to the model. The system needs to be easily removable from the model and installed in another one.

5. At what spatial increments are measurements desired?

This will likely be customer dependant. The spacing between measurement points will probably not be uniform over profile. The increment can be as small as 0.001 inches near the model surface and as large as 0.1 inches at distances greater than 0.5 inches from the surface. It will be important to know the distance from the surface to the measurement location with an uncertainty that is less than 0.001 inches.

Questions and Answers:

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