Browsing by Author "Dr. Harvey J. Charlton, Committee Member"

Now showing 1 - 3 of 3

Calibration Methods for a Constant Voltage Anemometer-Operated Hot-Wire in a Hypersonic Flow
(2003-09-17) Reimann, Craig Aaron; Dr. Hassan A. Hassan, Committee Member; Dr. Harvey J. Charlton, Committee Member; Dr. Ndaona Chokani, Committee Chair
The calibration of measurements made with a CVA-operated hot-wire, in a quiet hypersonic wind tunnel, are examined. Two calibration methods are evaluated. The first calibration method is based on the ratio of the power dissipated in the hot-wire and the difference between the hot- and cold-wire resistances. The second method is based on the traditional semi-empirical heat transfer relation for a heated wire in supersonic/hypersonic flow. The mean mass flux and total temperature derived from the calibration methods show overall good agreement with Navier-Stokes predictions. In general, the first method gives better results across the boundary layer. However, limitations in the calibration data meant no definitive assessment of the capability to yield fluctuation measurements could be made. The recently derived sensitivity coefficients for a CVA-operated hot-wire are used to obtain fluctuation measurements. Also, the fluctuating diagram method is used to evaluate the performance of the NASA Langley Mach 6 quiet tunnel and to detail the characteristics of the fluctuations in the laminar hypersonic boundary layer. Within the boundary layer, profiles of the measured rms fluctuations and the fluctuation diagrams show that the intensityof the boundary layer disturbance fluctuations are most intense in the vicinity of the critical layer. The static pressure fluctuations derived from the fluctuation diagrams verify that the fluctuations are less than 0.2%. This observation confirms previous qualitative observations of the performance of the Mach 6 quiet nozzle.
Distributed Actuation and Sensing on an Uninhabited Aerial Vehicle
(2003-08-12) Barnwell, William Garrard; Dr. Ndaona Chokani, Committee Chair; Dr. Charles E. Hall, Jr., Committee Member; Dr. Harvey J. Charlton, Committee Member
An array of effectors and sensors has been designed, tested and implemented on a Blended Wing Body Uninhabited Aerial Vehicle (UAV). This UAV is modified to serve as a flying, controls research, testbed. This effector/sensor array provides for the dynamic vehicle testing of controller designs and the study of decentralized control techniques. Each wing of the UAV is equipped with 12 distributed effectors that comprise a segmented array of independently actuated, contoured control surfaces. A single pressure sensor is installed near the base of each effector to provide a measure of deflections of the effectors. The UAV wings were tested in the North Carolina State University Subsonic Wind Tunnel and the pressure distribution that result from the deflections of the effectors are characterized. The results of the experiments are used to develop a simple, but accurate, prediction method, such that for any arrangement of the effector array the corresponding pressure distribution can be determined. Numerical analysis using the panel code CMARC verifies this prediction method.
Identification of Statistical Energy Analysis Parameters from Measured Data
(2003-04-03) Gregory, Joseph William; Dr. Richard F. Keltie, Committee Chair; Dr. Harvey J. Charlton, Committee Member; Dr. Charles E. Hall, Committee Member; Dr. Robert T. Nagel, Committee Member
An approach for identifying statistical energy analysis (SEA) parameters from experimental investigation is presented. Specifically, a power flow realization method (PRM) and statistical energy analysis model improvement (SMI) technique using transient time-domain vibration measurements are derived. The efforts are refined and validated using a range of test simulations, and then with true physical tests conducted on both simple and complex structures. Experimentation is also used to define the necessary input power measurements, response energy measurements, and data processing techniques necessary for successful PRM/SMI. It is found that utilization of time domain data allows for an over-determined power balance providing favorable numerical conditions for the identification. In fact, it is observed that a full matrix of measured inputs and outputs is not necessarily required for successful identification as is the case with current methods. Additionally, useful insight into system dimensionality is obtained during the identification process. Furthermore, it is found that the procedure indicates true parameters that are easily distinguished from those associated with noise in the data and, hence, is well suited for this application. Results indicate that the methodology has the potential to significantly enhance standard SEA procedures.