A review on laboratory experiments and numerical simulations mimicking convective cloud-like flows.
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| Title: | A review on laboratory experiments and numerical simulations mimicking convective cloud-like flows. |
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| Authors: | Bhat, G S1 (AUTHOR) bhat@iisc.ac.in, Diwan, Sourabh S2 (AUTHOR) |
| Source: | Sādhanā: Academy Proceedings in Engineering Sciences. Jun2025, Vol. 50 Issue 2, p1-22. 22p. |
| Subjects: | Coherent structures, Convective flow, Cumulus clouds, Radar meteorology, Cloud physics |
| Abstract: | Convective clouds play a major role in the large-scale circulation of the tropical atmosphere and monsoon rainfall. Understanding macro-scale dynamics of convective clouds has been one of the thrust areas in cloud physics, which has largely relied on field observations using instrumented aircraft and weather radars. A key physical process in clouds is release of latent heat following condensation of water vapor and associated increase in buoyancy. Previous attempts, starting from 1960s, to simulate cumulus cloud flow in the laboratory to understand entrainment rate in this class of flow were inconclusive as they involved chemical reactions where mixing of two reagents was a pre-requisite to increase buoyancy. Professor Narasimha's group in Bengaluru pioneered a laboratory apparatus to study the dynamics of cumulus clouds, in which dynamically similar quantities of heat were volumetrically added in a controlled manner to a jet/plume flow away from the source ("off-source") without involving a chemical reaction. Here we present a summary of the existing literature on off-source heated jets/plumes. The off-source heating significantly modifies the structure of a jet/plume by disrupting the large-scale coherent structures and promotes a more evenly mixed "protected core". Detailed quantitative measurements performed using laser Doppler and particle image velocimetry techniques in Bengaluru and elsewhere in the world documented the key statistical features of off-source heated jets/plumes and their departures from their unheated counterparts. An important result from these studies is that local heating changes the entrainment coefficient: it increases in the region immediately above the starting level of heat injection followed by a significant decrease after a certain axial distance. It is possible to reproduce several different types of cloud forms and their evolution by controlling time history and vertical profile of the off-source heating. The laboratory experiments inspired numerical simulations on off-source heated jets. The temporal simulations revealed that baroclinic torque suppresses large eddies and promotes small-scale eddies thereby enhancing the molecular mixing. Off-source heated spatial jets have provided new results on the entrainment dynamics that are broadly consistent with experimental findings, but with some differences in its variation in the post-heating zone. These experimental and numerical simulations on convective cloud-like flows represent a powerful tool in investigating their macro-scale dynamics. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Convective clouds play a major role in the large-scale circulation of the tropical atmosphere and monsoon rainfall. Understanding macro-scale dynamics of convective clouds has been one of the thrust areas in cloud physics, which has largely relied on field observations using instrumented aircraft and weather radars. A key physical process in clouds is release of latent heat following condensation of water vapor and associated increase in buoyancy. Previous attempts, starting from 1960s, to simulate cumulus cloud flow in the laboratory to understand entrainment rate in this class of flow were inconclusive as they involved chemical reactions where mixing of two reagents was a pre-requisite to increase buoyancy. Professor Narasimha's group in Bengaluru pioneered a laboratory apparatus to study the dynamics of cumulus clouds, in which dynamically similar quantities of heat were volumetrically added in a controlled manner to a jet/plume flow away from the source ("off-source") without involving a chemical reaction. Here we present a summary of the existing literature on off-source heated jets/plumes. The off-source heating significantly modifies the structure of a jet/plume by disrupting the large-scale coherent structures and promotes a more evenly mixed "protected core". Detailed quantitative measurements performed using laser Doppler and particle image velocimetry techniques in Bengaluru and elsewhere in the world documented the key statistical features of off-source heated jets/plumes and their departures from their unheated counterparts. An important result from these studies is that local heating changes the entrainment coefficient: it increases in the region immediately above the starting level of heat injection followed by a significant decrease after a certain axial distance. It is possible to reproduce several different types of cloud forms and their evolution by controlling time history and vertical profile of the off-source heating. The laboratory experiments inspired numerical simulations on off-source heated jets. The temporal simulations revealed that baroclinic torque suppresses large eddies and promotes small-scale eddies thereby enhancing the molecular mixing. Off-source heated spatial jets have provided new results on the entrainment dynamics that are broadly consistent with experimental findings, but with some differences in its variation in the post-heating zone. These experimental and numerical simulations on convective cloud-like flows represent a powerful tool in investigating their macro-scale dynamics. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 02562499 |
| DOI: | 10.1007/s12046-024-02658-x |
