Ahmadreza Vasel-Be-Hagh

A numerical study on shear layer behaviour in flow over a square unit of four cylinders at Reynolds number of 200 using the LB method

The major purpose of the present research is developing the Lattice Boltzmann (LB) method as an extremely efficient computational technique in the pragmatic field of fluid-structure interactions. Hence, the LB method is employed in simulating the incompressible flow past a square unit of four equal diameter circular cylinders. The simulation is conducted at Re of 200 and the spacing ratio (L/D) increases from 1.5 to 5 in 0.5 steps to cover all closely, moderately and widely spaced cases. Accordingly, the effects of the spacing ratio on the shear layer’s behaviour and vortex shedding pattern are studied in detail. Furthermore, its effects on the main force characteristics, i.e., lift and drag coefficients and also the Strouhal number are fully investigated. The observations and results obtained by the LB method employed in the current work are in strict accordance with experimental evidence of other researchers and other existent numerical data in the literature.

Energy storage using weights hydraulically lifted above ground

Renewable energy sources constitute an ever-growing share of the total electrical market; but, the intermittency and instability issues make it difficult to dispatch these sources directly into the grid. Energy storage represents a promising solution to overcome this obstacle. Among energy storage solutions, pumped hydro energy storage is largely considered the most technologically and financially feasible, though having some drawbacks. In this paper, a new design is introduced to address the major challenges associated with the conventional pumped hydro energy storage. The proposed storage solution does not require tall water tank towers or long piping; rendering it more cost effective and implementable. It is also scalable to operate over a wide range of capacities depending on the electrical surpluses. Beyond this, the design provides a constant pressure and faster discharge, furnishing a quick response to instantaneous demand fluctuations.

Drag of buoyant vortex rings.

Extending from the model proposed by Vasel-Be-Hagh et al. [J. Fluid Mech. 769, 522 (2015)], a perturbation analysis is performed to modify Turners radius by taking into account the viscous effect. The modified radius includes two terms; the zeroth-order solution representing the effect of buoyancy, and the first-order perturbation correction describing the influence of viscosity. The zeroth-order solution is explicit Turners radius; the first-order perturbation modification, however, includes the drag coefficient, which is unknown and of interest. Fitting the photographically measured radius into the modified equation yields the time history of the drag coefficient of the corresponding buoyant vortex ring. To give further clarification, the proposed model is applied to calculate the drag coefficient of a buoyant vortex ring at a Bond number of approximately 85; a similar procedure can be applied at other Bond numbers.