@article{zhu_arya_snyder_1998, title={An experimental study of the flow structure within a dense gas plume}, volume={62}, ISSN={["0304-3894"]}, DOI={10.1016/S0304-3894(98)00162-9}, abstractNote={A wind tunnel study was conducted to examine how a dense gas plume could affect the mean flow and turbulence structure of the boundary layer containing the plume. For this, a neutral atmospheric boundary layer developing over an aerodynamically rough surface was simulated in the US EPA's Meteorological Wind Tunnel. The dense gas plume was created by releasing CO2 through a small circular source at ground level. A procedure was developed to make reasonably accurate mean velocity and turbulence measurements within the dense gas plumes by using hot-film anemometry in a range where the probe response was insensitive to the concentration of CO2. Both the flow visualization and quantitative measurements of concentration and velocity fields indicated that, at low wind speeds, the dense gas plumes exhibited significant buoyancy effects on the flow structure. Within the dense plumes, mean velocity profiles were observed to have changed significantly in shape, with reduced speeds near the surface and increased velocities farther away from the surface. Consistent with these changes in mean velocity profiles, significant reductions in the roughness length and friction velocity were observed. Both the longitudinal and vertical turbulence intensities were also found to be greatly reduced within the dense plumes at low wind speeds. These changes in mean flow and turbulence structure were not only related to the dense-gas concentrations, but also to the local velocity gradients and the growth of the dense plumes with distance from the source. The local gradient Richardson number is found to be the most appropriate parameter for describing the changes in the mean flow and turbulence structure. Significant dense gas effects were observed when the Richardson number increased beyond its critical value (0.25) for the dynamic stability of a stratified flow. Our experimental results show that, in an existing turbulent flow, turbulence is not completely suppressed even when the gradient Richardson number exceeds one.}, number={2}, journal={JOURNAL OF HAZARDOUS MATERIALS}, author={Zhu, GW and Arya, SP and Snyder, WH}, year={1998}, month={Sep}, pages={161–186} }
 @article{lu_arya_snyder_lawson_1997, title={A laboratory study of the urban heat island in a calm and stably stratified environment .1. Temperature field}, volume={36}, ISSN={["0894-8763"]}, DOI={10.1175/1520-0450(1997)036<1377:ALSOTU>2.0.CO;2}, abstractNote={An extensive and systematic water-tank study was performed to simulate the urban heat island under a calm and stably stratified environment. The objective was to examine the mean-temperature field, mixing height, and heat-island intensity as functions of surface heating rates, heat-island sizes, and ambient temperature gradients. The scaling parameters for the temperature field associated with the heat-island plume are the diameter D, surface heating rate H0, and Brunt–Väisälä frequency N of the ambient stratification. The induced plume was turbulent, and the Froude number was found to be the most important similarity parameter. The differences between low- and high-aspect-ratio plumes are discussed, and simple theoretical models are proposed for low-aspect-ratio plumes. The experimental results generally confirm the theoretical predictions and agree reasonably well with field observations, in spite of several limitations of the laboratory simulation. The mean-temperature distributions are found to have a universal shape that is a function of location only. The results are described in two papers. In this paper, the temperature fields are described. Part II describes the velocity fields and develops analytical models that apply to low-aspect-ratio plumes.}, number={10}, journal={JOURNAL OF APPLIED METEOROLOGY}, author={Lu, J and Arya, SP and Snyder, WH and Lawson, RE}, year={1997}, month={Oct}, pages={1377–1391} }
 @article{lu_arya_snyder_lawson_1997, title={A laboratory study of the urban heat island in a calm and stably stratified environment .2. Velocity field}, volume={36}, ISSN={["0894-8763"]}, DOI={10.1175/1520-0450(1997)036<1392:ALSOTU>2.0.CO;2}, abstractNote={Abstract A fully turbulent, low-aspect-ratio buoyant plume with no initial momentum under calm and stably stratified conditions is produced in a convection tank. The plume is generated by a circular heat island at the bottom of the tank. Two analytical models, a bulk convection model and a hydrostatic model, are developed to formulate similarity relations for the low-aspect-ratio plume. The convective velocity scale wD, suggested by the analytical models, is used as the similarity parameter for both the mean velocity and standard deviations of velocity fluctuations. The normalized standard deviations of horizontal and vertical velocities agree with each other for two heating rates, as well as with field observations in the center of Sapporo, Japan. The suggested scaling and empirical relations based on our experimental results may be applied to the velocity fields of other low-aspect-ratio plumes in calm and stably stratified environments. Further investigations are recommended to confirm the results of t...}, number={10}, journal={JOURNAL OF APPLIED METEOROLOGY}, author={Lu, J and Arya, SP and Snyder, WH and Lawson, RE}, year={1997}, month={Oct}, pages={1392–1402} }
 @article{brown_arya_snyder_1997, title={Plume descriptors derived from a non-Gaussian concentration model}, volume={31}, ISSN={["1352-2310"]}, DOI={10.1016/1352-2310(96)00487-6}, abstractNote={Equations for point-source releases are derived from the non-Gaussian solution to the diffusion equation for (l) the first four moments of the vertical concentration distribution (centroid, variance, skew-ness, and kurtosis), (2) the magnitude and downwind location of the maximum ground-level concentration, and (3) the plume advection velocity. Equations are obtained for both ground-level and elevated sources. Where applicable, results are compared to wind-tunnel and field measurements and/or to other less generalized equations.}, number={2}, journal={ATMOSPHERIC ENVIRONMENT}, author={Brown, MJ and Arya, SP and Snyder, WH}, year={1997}, month={Jan}, pages={183–189} }