Stability of a moving radial liquid sheet: experiments

A recent theory (Tirumkudulu & Paramati, Phys. Fluids, vol. 25, 2013, 102107) for a radially expanding liquid sheet, that accounts for liquid inertia, interfacial tension and thinning of the liquid sheet while ignoring the inertia of the surrounding gas and viscous effects, shows that such a sheet is convectively unstable to small sinuous disturbances at all frequencies and Weber numbers. We equivalent to rho(l)U(2)h/sigma). Here, rho(l) and sigma are the density and surface tension of the liquid, respectively, U is the speed of the liquid jet, and h is the local sheet thickness. In this study we use a simple non-contact optical technique based on laser-induced fluorescence (LIF) to measure the instantaneous local sheet thickness and displacement of a circular sheet produced by head-on impingement of two laminar jets. When the impingement point is disturbed via acoustic forcing, sinuous waves produced close to the impingement point travel radially outwards. The phase speed of the sinuous wave decreases while the amplitude grows as they propagate radially outwards. Our experimental technique was unable to detect thickness modulations in the presence of forcing, suggesting that the modulations could be smaller than the resolution of our experimental technique. The measured phase speed of the sinuous wave envelope matches with theoretical predictions while there is a qualitative agreement in the case of spatial growth. We show that there is a range of frequencies over which the sheet is unstable due to both aerodynamic interaction and thinning effects, while outside this range, thinning effects dominate. These results imply that a full theory that describes the dynamics of a radially expanding liquid sheet should account for both effects

Does energy diversification cause an economic slowdown? Evidence from a newly constructed energy diversification index

Countries have made considerable efforts to diversify their energy sources from fossil fuels to renewables in the last two decades to achieve sustainable economic development. However, it is widely argued that the countries may experience sluggish economic development during the energy transition period due to structural and functional changes in the economic system. Given this backdrop, this study introduces a new measure of energy diversification. It explores its impact on economic development across the panels of low-income, high-income, European Union (EU), the Organization for Economic Co-operation and Development (OECD), and G20 countries. The study uses data from 1995 to 2018 and utilizes Nonlinear Panel Autoregressive Distributed Lag (NPARDL) method. Our findings confirm that the major economies (including G20) realize positive economic growth with increasing long-run energy diversification. However, some countries (OECD and G20) experience negative economic growth due to energy diversification in the short term. The results also disclosed that energy diversification does not favor economic growth in low-income economies in both the short and long term. Therefore, more precautionary measures to be taken into account while diversifying energy sources