Experimental and numerical study of local mean age of air

This paper presents the results from the experimental and numerical study of a room with mixing ventilation, focused on the local mean age of air (LMA). The measurements were performed using the tracer gas concentration decay method. The numerical predictions were obtained from the computational fluid dynamics (CFD) module of the latest version of the ESP-r software

Turbulence induced changes in vortex shedding from a circular cylinder

CER73-74KMB-JEC27.Includes bibliographical references (pages 61-66).Prepared under Office of Naval Research contract no. N00014-68-A-0493-0001; project no. NR 062-414/6-6-68 (Code 438).January 1974.Turbulence effects on vortex shedding from a circular cylinder were investigated in a wind tunnel. Most of the literature on vortex shedding reports investigations in air flows where special efforts had been made to keep the turbulence intensity very low (usually <.5%) in the free stream. Under such conditions, vortex shedding from a circular cylinder can be classified into four regimes with a discontinuity condition between each two succeeding regimes. These regimes are identified by the span of Reynolds numbers, Re, and Strouhal numbers, St, by the angle of boundary layer transition, α, and by the transition point from laminar to turbulent flow in the boundary layer or vortex. In this study, turbulence intensity, near the center of a wind tunnel, was increased from .3% to 25% by plates of similar geometry (many small holes) with blockage ratios from .50 to .97. The Re of all flows was kept near 4 x 104. Vortex shedding frequency, f, was observed simultaneously by a pressure transducer (with sensors on cylinder surface) and a hot wire anemometer (immediately downstream). Means of 50 to 150 cross-spectra defined f. Flow visualization, spectra and transducer output voltages with different α were utilized to estimate transition and separation. Four concepts were verified that are already in the literature. As the turbulence intensity of the upstream flow is increased: (a) the vortex shedding regimes occur at lower Re; (b) discontinuities lose any dominant f value that they might have had; (c) vortices are destroyed closer to the cylinder; and (d) the size of cylinders influence turbulence effects on vortex shedding. Six things were observed that have not been published, to the best of the author's knowledge: (a) analogous changes in vortex shedding processes can be obtained either by increasing the air speed (while holding the turbulence intensity very low) or by increasing the turbulence intensity (while holding the air speed approximately constant); (b) the frequency of the vortex shedding becomes relatively smaller, for the vortex shedding regime, as the turbulence intensity is increased; (c) an estimate of the turbulence induced changes in vortex shedding can be made from Re of the flow, mean air speed, rms value of longitudinal speed fluctuations, integral scale of turbulence and cylinder diameter; (d) the "super critical" regime , associated with highest α and St, can be disrupted by sufficient turbulence intensity; (e) the extent to which turbulence can induce changes in vortex shedding is limited. A model of vortex shedding is hypothesized which includes the concept that vortex shedding is continuous from Re near 40 until either the mean air speed and the turbulence intensity, or both, are increased until turbulence destroys individual vortices before they can be shed

An efficient feti based solver for elasto-plastic problems of mechanics

This paper illustrates how to implement effectively solvers for elasto-plastic problems. We consider the time step problems formulated by nonlinear variational equations in terms of displacements. To treat nonlinearity and nonsmoothnes we use semismooth Newton method. In each Newton iteration we have to solve linear system of algebraic equations and for the numerical solution of the linear systems we use TFETI algorithm. In our benchmark we compute von Misses plasticity with isotropic hardening and use return mapping concept

Research and development technique for estimating airflow and diffusion parameters in connection with the Atmospheric Water Resources Program: annual report

September 1970.CER70-71MMO-JEC-LOG23.Period September 2, 1969 to June 30, 1970.Includes bibliographical references.Atmospheric Water Resources Research, Bureau of Reclamation, Contract No. 14-06-D-6842

Research and development technique for estimating airflow and diffusion parameters related to the Atmospheric Water Resources Program: final report

Period September 1969 to September 1971.CER71-72MMO-JEC-LOG20.Includes bibliographical references

Delivery of nucleating materials to cloud systems from individual ground generators

CER69-70LOG-JEC-MMO24.February 1968.Includes bibliographical references (pages 40-42).Presented to the Bureau of Reclamation Third Skywater Conference on the Production and Delivery of Cloud Nucleating Materials February 14-16, 1968.Delivery of nucleating materials to cloud systems from individual ground generators can play an important role in the beneficial modification of orographic cloud systems. Substantial evidence from the Colorado State University mountain study at Climax is presented to show that ground-released seeding materials do under some weather situations in fact enter the mountain cloud systems and produce changes in the precipitation. Evidence is also presented to show that under other weather situations seeding materials are not carried to the proper clouds at a place and time to be of value. A discussion of atmospheric transport mechanisms is presented to serve as a basis for understanding the motions of seeding materials once released from a ground source. The approaches, or directions, for further research are discussed. This includes consideration of the coagulation problem in the vicinity of the generator site. The use of wind tunnel modeling, which can provide basic information and specific results for specific areas, is emphasized

Research and development technique for estimating airflow and diffusion parameters in connection with the Atmospheric Water Resources Program : final report

CER69-70JEC-LOG-MMO-11.August 1969.Includes bibliographical references (pages 47-48).Period March 15, 1968 to June 30, 1969 Atmospheric Water Resources Research Bureau of Reclamation Contract No. 14-06-D-6455.A stably stratified atmospheric boundary layer was simulated in a wind tunnel and utilized to determine radioactive krypton dispersion patterns over a 1:9600 scale model of the Eagle River Valley and topography surrounding Climax, Colorado. Geometric, dynamic, and thermal similarity are considered, primarily, for barostromatic airflow. Similarity criteria for transport and dispersion are considered also. This is the first time that a barostromatic airflow produced by cooling with dry ice has been documented by temperature and velocity profile measurements. Field Gata indicate that airflow and temperature characteristics over the model are approximately similar to a prototype storm. Dispersion measurements were taken by using sources representative of field ground sources. Model and field measurements confirm that seeding nuclei are reaching the target area from the present existing ground sources. Limited field measurements of ice nuclei concentrations at Chalk Mountain show a variation of 5 to 300 part./liter or XU/Q ~ 1 x 10 -9m-2 to 68 x 10-9m-2. Concentration values deduced from radioactive gas measurements over the model show values within the same range but closer to the optimum values indicated by present cloud physics models, i.e., XU/Q ~ 15 to 18 x 10-9m-2. The barostromatic airflow model indicated that topography plays an important role in determining the downwind direction of the particulate plume.Under contract no. 14-06-D-6455

Dispersion of vapor from LNG spills: simulation in a meteorological wind tunnel

CER76-77RNM-JEC-DEN-MM57.Under contract to R & D Associates, Marina del Ray (C.A.).Includes bibliographical references (page 35).May 1977

Research and development technique for estimating airflow and diffusion parameters in connection with the Atmospheric Water Resources Program: interim report

CER70-71MMO78.Period September 2, 1970 to February 28, 1971.Includes bibliographical references (pages 38-39).Atmospheric Water Resources Research, Bureau of Reclamation, Contract No. 14-06-0-6842.This report presents a summary of the research and tentative findings on the use of scaled topographic models and laboratory techniques to study the transport and dispersion of cloud seeding material over mountainous terrain. Three mountainous areas along the continental divide have been selected by the Bureau of Reclamation for such studies. Each area has cloud seeding programs in progress