Animal Flight

Abstract: Unlike airplanes, animals must have either flapping wings (birds, bats) or oscillating wings (insects). Only such wings can produce both lift and thrust, provided the animal has sufficient muscle power.
To fly, wings impart downward momentum to the surrounding air and obtain lift by reaction. How this is achieved under various flight situations (cruise flight, hovering, landing, etc.), and what is the role of the wing-generated vortices in producing lift and thrust is discussed (both for birds and insects).
Bird wings have several possibilities how to obtain the same functions as airplane wings. Birds have the capabilities of adjusting the shape of the wing according to what the immediate flight situation demands, as well as of responding almost immediately to conditions the flow environment dictates.

FLUIDIC OSCILLATORS FOR ALGAE CULTIVATION and their role in geopolitic stability

Abstract:
Our civilisation is extremely dependent on cheap liquid fuel used for transportation. Until roughly the end of 19th century people used to work in their respective dwelling places. Now they commute in huge numbers every day. Food and other goods travels hundreds (if not thousands) of kilometres between production and use. This model is increasingly adopted by developing most populated countries (China, India). Fossil fuel sources, on which this all depends, is produced – at an increasingly high cost – in politically unstable regions. No wonder research grant providers are willing to support financially the research promising renewable petrol as its result. The starting point are algae – primitive, often unicellular plants capable to produce by photosynthesis - from H in water and CO2 taken from air - hydrocarbon compounds, processing of which into biofuels brings no difficulty in principle – after all, the fossil oil was produced the same way from algae millions of years ago. Additional benefit would be the whole process being carbon neutral so that removal of CO2 from the atmosphere would suppress the global warming. Algae may be also a starting point of a food chain, solving another global problem.
The difficulty is so far the price of the crude oil from algae being higher than the fossil one. The key factor for success is making more efficient every step in the process. One of perhaps small but nevertheless important contribution towards the goal is more efficient diffusion transport of CO2 into the algae in bioreactors. Suggested solution is generation of sub-millimetre sized microbubbles by placing a fluidic oscillator into the gas inlet. The research grant project investigated in the Institute of Thermomechnaics enabled recently testing a number of alternative oscillator designs.

Discontinuous Galerkin method for the solution of elasto-dynamic, compressible flow and fluid-structure interaction problems

Abstract:
This lecture will be concerned with the numerical solution of dynamic elasticity and compressible flow. We consider the linear case as well as the nonlinear St. Venant-Kirchhoff model. The space Discretizat on is carried out by the discontinuous Galerkin method (DGM). For the time discretization several techniques are proposed and tested. As the best method the DG discretization both in space and time appears. The discontinuous Galerkin method is also used for the numerical solution of compressible flow in time-dependent domains, formulated with the aid of the arbitrary Lagrangian-Eulerian (ALE) method. It will be shown that this method allows the solution of compressible flow with a large range of the Mach number. Then the developed methods are combined and used for the numerical simulation of vibrations of elastic bodies induced by compressible flow. The applicability of the developed techniques will be demonstrated by several numerical experiments.
The results were obtained in cooperation with M. Balázsová, J. Česenek, M. Hadrava, A. Kosík and J. Horáček.