The behavior of ablated plumes produced by nanosecond scale multiple laser pulses typical for carbon ablation is studied in order to understand the plume expansion dynamics and shielding effect of plume with special interest to ionization of plumes. The patterns of a planar plume (typical for channel cutting) and an axisymmetric plume (typical for hole drilling) appear to be quite different. Ionization in carbon plume is estimated using the Saha equation. An iterative procedure is developed to determine the local equilibrium temperature affected by ionization. It is shown that though shielding due to the presence of ionized particles in carbon plume is small, the effect of ionization on plume temperature can be considerable. Shielding effect is calculated for laser pulses with different time intervals between pulses. The effects of high temperature and low density of plume are conflicting and cause shielding behavior to be nonmonotonic. It is shown that the nonmonotonic dependence of the delivered laser energy, the pulse number, and the difference in shielding characteristics between planar and axisymmetric formulations increase with the time duration between two consecutive pulses.

The dynamics of a conducting laser ablated carbon plume flow in the ablation furnace typical for nanoparticle synthesis is investigated by numerical modeling. The effect of magnetic field on the flow is accounted through the Lorentz body force. The study begins with benchmark calculations of two simple test cases, the Kelvin–Helmholtz instability and Hartmann layer. The evolution of plume is then studied for longitudinal and transverse magnetic fields. It is observed that the transverse magnetic fields have more impact than longitudinal fields on plume evolution for this application. Ionization and heat capacity variation in the plume are accounted through the Saha equation and the Shomate equation, respectively. Multiple plume ejections typical for pulsed laser deposition of thin films are also discussed.

Wood is generally used as a source of energy for cooking in rural and semi-urban areas of India. Approximately 216 million tons per year of wood is consumed in the cooking of which 9.731 million tons per year is used in Gujarat. The use of wood causes deforestation and increases indoor pollution. To reduce this, solar energy can be used as an alternate source of energy for cooking. The current research aims to present the findings of two weeks of experiments in the Indian (Gujarat) climate with the novel solar cooker. The cooker was build using a parabolic dish collector (85 % reflectivity) with a supporting structure and adjustable mechanism, a receiver (heat exchanger) and a cooking burner with a pot. The experimental result shows that the maximum temperature available at the receiver is 110°C with 560.7 W/m2 of average solar irradiation, justifying solar cooking as a viable alternative source of energy for cooking in Gujarat and India.

One of the major methods of production of carbon nanotubes is the laser ablation process. In this process, a powerful nanosecond-scale laser beam illuminates a target. The resulting explosion produces a plume of rapidly expanding gaseous carbon with embedded metallic catalysts, on whose surfaces the nanotubes are formed. The time-scale of a single laser pulse is of the order of nanoseconds whereas the plume development and growth of nanotubes take up to several milliseconds. The synthesis process largely depends on the plume properties, i.e., on the temperature, pressure, and density of the expanding plume. In turn, the plume propagation depends on the ablation speed, pressure, and density. In the current study, a combined thermal and gas dynamics model is proposed, implemented and tested. The proposed model is based on combined conduction heat transfer within the solid target, carbon sublimation process described by equilibrium thermodynamics, and process of plume development described by continuous gas dynamics. The carbon sublimation model is based on Clausius-Clapeyron equation and conservation of energy for differential control volume. The parameters of the injected plume are defined by this thermal model. The validity of viscous and inviscid models of plume dynamics is discussed. The ability of finite-volume discretizations to capture the plume dynamics and its roll-up is compared for various numerical schemes. To evaluate the accuracy of numerical modeling of plume dynamics, we compare finite-volume discretization based on Relaxing TVD scheme with that based on the upwind scheme with Roe averaging at the cell interface and non-linear ENO scheme for second-order flux formulas.

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