An air-tunnel study of the establishment of the wake behind a disk at a Reynolds number of approximately 7 × 104 was undertaken. On the basis of the measured data, such a wake is fully established, that is, similarity profiles of the flow characteristics are formed, within 15 diameters of the disk, and approximately 95 percent of the transfer of energy from the mean motion to the turbulence motion takes place within 3 diameters of the disk, in the region of the mean standing eddy. The measured mean ambient-pressure and mean total-pressure distributions, mean velocity distributions, turbulence-intensity and shear-stress distributions, and the mean streamline pattern are presented in graphical form, as are the quantitative balances of the integrated momentum and mean-energy relationships. A stream function consisting of a continuous distribution of doublets is introduced to extend the radial limit of understanding of the flow characteristics to a very large if not infinite radius. Considerable attention is given to the problem of obtaining and interpreting turbulence shear-stress data immediately downstream from the point of flow separation. The applicability of a local diffusion coefficient or virtual viscosity of the Boussinesq or Prandtl type for relating the turbulence shear stress to the radial gradient of mean axial velocity is discussed. The Bernoulli sum and the energy changes along individual streamlines investigated in an associated study are incorporated herein to obtain a quantitative estimate of the local errors involved in the turbulence-shear-stress measurements.
In the flow-establishment region of an air jet issuing with an efflux velocity of about 35 ft./sec from a 1.0 ft. diameter nozzle into still air, measurements were made of mean axial and radial velocities, mean static pressure, turbulence intensities, turbulent shear, and pressure fluctuation. For the measurement of the latter a pressure probe using a ceramic piezo-electric tube was developed. Also included in the measurements were the temporal mean gradient and autocorrelation of the axial-velocity fluctuation and the intermittency factor. The fluctuating-pressure and turbulence-intensity fields were observed to be closely similar in form. Through use of the measured distributions of mean-flow and turbulence characteristics, all terms of the integral and differential forms of the momentum and mean-energy equations were evaluated throughout the region. The results are presented herein by curves of variation of each of the terms as they appear in the corresponding equations.
Industrial hygienists often work closely with engineers to control occupational safety and health hazards. This working relationship involves an educational process in which both engineers and industrial hygienists learn from one another. The Center for Chemical Process Safety (CCPS) of the American Institute of Chemical Engineers (AIChE) is expanding the opportunity for interdisciplinary cooperation and education by producing a series of guidelines publications on the technical and scientific issues critical to preventing and mitigating major releases of toxic materials. Examples of these guidelines include Hazard Evaluation Procedures; Technical Management of Chemical Process Safety; Chemical Process Quantitative Risk Analysis; and Safe Storage and Handling of Highly Toxic Hazardous Materials. Additional topics are addressed in the 8 guidelines in print and the 15 others in preparation. Several guidelines contain specific examples that illustrate how industrial hygienists, engineers, and other readers can use the guidelines to help address chemical process safety problems. Another CCPS activity involves an effort to include an awareness of health, safety, and loss prevention as an integral part of undergraduate chemical engineering education. For practicing engineers and industrial hygienists, a number of continuing education courses on topics such as process hazard analysis, process risk assessment, and process safety are offered by the AIChE. All of these resources are particularly timely in light of the Occupational Safety and Health Administration's recently enacted rule on Process Safety Management of Highly Hazardous Chemicals.
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