Hot-wire and hot-film anemometry

The circuit techniques, electronics, dynamic properties, and the applications of the anemometers are given

Survey of environmental parameter sensors for a personal heat stress monitor

"This report summarizes the results of a directed survey and review of environmental parameter sensors for use in a personal heat stress monitor unit. A discussion of sensing techniques is given with descriptive details on the sensor's physical characteristics, theoretical basis of sensor operation, and suitability for use in a personal monitor unit. The parameters of interest in this survey are air velocity, dry bulb temperature, wet bulb temperature, natural wet bulb temperature and 1-inch globe temperature or mean radiant temperature. The sensors and measurement techniques found to be useable or adaptable through modification for use in a heat stress monitor are identified and a preliminary design is given which will permit the construction and testing of a complete system. With reference to the 6-inch globe temperature, two options are given with each requiring additional development effort for implementation. The objective of this survey did not include data recording methods or data processing. However, a short discussion is included discussing current techniques which are applicable to the system requirements." - NIOSHTIC-2NIOSHTIC no. 2004657976-182.pdf?id=10.26616/NIOSHPUB761821976Contract No. 210-75-00361117

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

The hot wire anemometer

Hot-wire anemometer and its application to measurements in turbulent flow

A Hot-Wire Anemometer for Particle Counters

Portable real-time air quality monitoring is becoming a reality. While the data quality of these devices may be questionable, they have shown to be promising. One such device is the optical particle counter. The particle counter functions by having laminar airflow with constant velocity traverse the path of a laser beam within an airflow channel. This thesis presents the design and integration of a hot-wire anemometer into the flow channel. The addition of an anemometer allows for real-time airflow velocity measurements to be performed and adjusted. Data from the anemometer can also be used to directly offset irregularities in particulate measurements during flow speeds outside the corrective capabilities of the fan. Experimental results show that an integrated anemometer is capable of correcting varying external disturbances and improving the accuracy of particle counting measurements

Acoustic source location in a jet-blown flap using a cross-correlation technique

The acoustic source strength distribution in a turbulent flow field was measured for two far field microphones at 45 deg above and below the plane of the flap surface. A processed signal from an inclined hot-film anemometry probe was cross correlated with the signal from the appropriate far field microphone. The contribution made by the sources associated with the fluctuating pressure on the flap surface to the sound received at far field microphone was estimated by cross correlating the processed signals of microphones which were embedded in the flap surface with the far field microphone signals. In addition, detailed fluid dynamic measurements were made in the flow field of the jet flap using dual sensor hot-film anemometry probes

The Use of Electrochemical Techniques to Study Turbulence Close to a Wall

Electrochemical techniques can be used to measure the time averaged velocity gradient and the two components of the fluctuating velocity gradient at a solid surface. A chemical reaction Is carried out at the surface of a small electrode embedded in the wall. The voltage applied to the electrode Is large enough that the current flowing in the circuit is controlled by the mass transfer rate. The probes are the mass transfer analog of the hot wire or hot film anemometer. If the test electrode is part of a large electrode surface, it can be used to measure local time averaged and fluctuating mass transfer rates. Research work on the development of these techniques is reviewed. This includes problems encountered, probe design and mathematical analysis. A typical flow system in which the techniques have been used Is discussed. Data that have been obtained for turbulence close to a wall are presented. A comparison between electrochemical techniques and the thermal wall meters is given

Improved Techniques for the Decomposition of Hot-Wire Fluctuation Measurements in Supersonic Flows

This work originated from the need to provide a reliable interpretation of hot-wire anemometer fluctuation measurements in the supersonic jet noise research performed at Oklahoma State University. The objective of this work was to develop a data reduction technique which included hot-wire end-loss corrections to determine the mass velocity fluctuations and total temperature fluctuations in a supersonicturbulent flow field.Mechanical Engineerin

An experimental study of a self-confined flow with ring-vorticity distribution

A new form of self-confined flow was investigated in which a recirculation zone forms away from any solid boundary. An inviscid flow analysis indicated that in a purely meridional axisymmetric flow a stationary, spherical, self-confined region should occur in the center of a streamlined divergent-convergent enlargement zone. The spherical confinement region would be at rest and at constant pressure. Experimental investigations were carried out in a specially built test apparatus to establish the desired confined flow. The streamlined divergent-convergent interior shape of the test section was fabricated according to the theoretical calculation for a particular streamline. The required inlet vorticity distribution was generated by producing a velocity profile with a shaped gauze screen in the straight pipe upstream of the test section. Fluid speed and turbulence intensity were measured with a constant-temperature hot-wire anemometer system. The measured results indicated a very orderly and stable flow field