ВИНОРОБСТВО І ВИНОГРАДАРСТВО У

Простежено розвиток і проаналізовано чинники, що на нього впливали, виноградарської і виноробної галузі сільського господарства Буджаку (Південної Бессарабії) наприкінці ХІХ - на початку ХХ ст. на документах фонду Аккерманської повітової земської управи Ізмаїльського архіву.There are investigated and analysed factors of development of vine branch of the agriculture of Budchack (South Bessarabia) at the end of XIX – beginning of XX cent. based on the documents of Accerman zemskoy upravy of Ismail archive

High aerodynamic lift from the tail reduces drag in gliding raptors

Many functions have been postulated for the aerodynamic role of the avian tail during steady-state flight. By analogy with conventional aircraft, the tail might provide passive pitch stability if it produced very low or negative lift. Alternatively, aeronautical principles might suggest strategies that allow the tail to reduce inviscid, induced drag: if the wings and tail act in different horizontal planes, they might benefit from biplane-like aerodynamics; if they act in the same plane, lift from the tail might compensate for lift lost over the fuselage (body), reducing induced drag with a more even downwash profile. However, textbook aeronautical principles should be applied with caution because birds have highly capable sensing and active control, presumably reducing the demand for passive aerodynamic stability, and, because of their small size and low flight speeds, operate at Reynolds numbers two orders of magnitude below those of light aircraft. Here, by tracking up to 20,000, 0.3 mm neutrally buoyant soap bubbles behind a gliding barn owl, tawny owl and goshawk, we found that downwash velocity due to the body/tail consistently exceeds that due to the wings. The downwash measured behind the centreline is quantitatively consistent with an alternative hypothesis: that of constant lift production per planform area, a requirement for minimizing viscous, profile drag. Gliding raptors use lift distributions that compromise both inviscid induced drag minimization and static pitch stability, instead adopting a strategy that reduces the viscous drag, which is of proportionately greater importance to lower Reynolds number fliers

Investigation on trailing-edge noise sources by means of high-speed PIV

The noise generation of turbulent flows over surfaces and around edges of airplanes and automobiles is a general design problem and its importance increases in times of growing traffic in this globalizing world. Turbulent boundary layers near the trailing-edge of a surface are known to generate intense, broadband scattering noise as well as surface pressure fluctuations. The wake of vortices shed depends on the trailing edge thickness and results in the emission of narrow band noise. The noise generating mechanisms depend essentially on the radial components of the velocity fluctuations in respect to the trailing edge. Resulting forces may also cause model vibrations, which are additional low frequency noise sources. In this feasibility study the high-speed PIV (HS-PIV) technique is applied to an investigation of the spatial and temporal development of coherent structures in a turbulent flat-plate boundary layer flow in the vicinity of the trailing-edge (TE). It is expected that with time resolved PIV data obtained in the region immediately up- and downstream of the TE an identification of noise sources and their correlation with the flow structure movement will be possible. On the basis of a large number of time resolved instantaneous velocity vector fields the technique enables also the possibility of determining several statistical quantities of fluid mechanical significance: average velocity profiles, velocity fluctuations (u´, v´), rms-fields, probability density functions and space-time-correlations of the velocity fluctuations and the z-component of vorticity. The far field noise intensity, which is radiated locally at the position of the TE, measured simultaneously with the instantaneous velocity fields by a directional microphone at 80 kHz sample rate. A phenomenological link between noise and flow structure movement by a comparison of the pressure -time -history of the far field with the time-velocity vector fields directly at the noise source is one objective of this investigation. A connection of the velocity fluctuation structures to the far field noise by means of space-time-correlations is a first step towards an identification of the noise generating flow structures

Investigation of trailing-edge noise sources by means of high-speed PIV

Turbulent boundary layers near the trailing-edge of a surface are known to generate intense, broadband scattering noise as well as surface pressure fluctuations. The noise generating mechanisms depend essentially on the radial components of the velocity fluctuations in respect to the trailing edge. Resulting forces may also cause model vibrations, which are additional low frequency noise sources. The high-speed PIV (HS-PIV) technique is applied to an investigation of the spatial and temporal development of coherent structures in a turbulent flat-plate boundary layer flow in the vicinity of the trailing-edge. With time resolved PIV data obtained in the region immediately up- and downstream of the trailing edge an identification of the flow structure movement, which cause the noise sources is possible. On the basis of a large number of time resolved instantaneous velocity vector fields the technique enables also the possibility of determining several statistical quantities of fluid mechanical significance: average velocity profiles, velocity fluctuations (u´, v´), rms-fields, probability density functions and space-time-correlations of the velocity fluctuations, the instantaneous Reynolds stresses (u´v´) of all four quadrants and the z-component of vorticity. A flat plate with an elliptic leading edge was mounted vertically in the AWB, the low noise wind tunnel of DLR, Braunschweig. At a free stream velocity of U = 40 and 50m/s and a stream-wise length of the flat plate of x = 2 m a turbulent boundary layer flow develops and the flow structures convect past the trailing edge

A Study on Trailing Edge Noise Sources using High-Speed Particle Image Velocimetry

The noise generation of turbulent flows near the edges of airplanes and automobiles is a general design problem and its importance increases in times of growing traffic. Turbulent boundary layers being convected past the trailing edge into the wake are known to generate an intense, broadband scattering noise. In this feasibility study the high-speed PIV technique was applied to a generic trailing edge noise experiment as performed on a flat plate model in the Aeroacoustic Wind Tunnel Braunschweig (AWB). Trailing edge source noise was measured simultaneously with instantaneous velocity vector fields to relate the generated sound to the ensuing aeroacoustic source quantities. The first step towards a new procedure for trailing edge noise prediction, combining numerical methods with the high-speed PIV measurement, is presented

Tomographic particle-image velocimetry in an IC engine

The flow structures during the intake and compression phase within the cylinder of an internal combustion(IC)engine strongly influence the mixing and combustion process. To gain a better understanding of the flow field, fully three-dimensional quantitative measurement techniques have to be applied to the flow field. Analog off-axis holographic particle-image velocimetry is capable of resolving the whole flow field of an IC engine with very high resolution (van Overbrueggen et. al [21]). On the other hand, long processing procedures make this technique not feasible for a statistic flow field analysis. Tomographic particle-image velocimetry (Tomo-PIV) is another three-component/three-dimensional (3C/3D) measurement technique that could be used. It is digital and therefore possesses the advantage of relatively short processing time. In this study, cycle resolved tomographic particle-image velocimetry measurements are performed in a four-valve IC engine to resolve the highly three dimensional flow in a large area of the cylinder. The resolved volume has a size of about 60 x 60 x 80 mm3 for the 160? measurements. The three-dimensional structure of the flow field is analyzed for 80?, 160?, and 240? after top dead center (aTDC) during the intake and compression phase at an engine speed of 1,500 rpm. The flow fields are analyzed by ensemble-averaged velocity fields, turbulent kinetic energy (TKE), and the G1 vortex center criterion. The results provide detailed inside in the highly three-dimensional flow field inside an internal combustion engine and show the feasibility of tomographic PIV to resolve such a large volume in a complex geometry

Investigation of a turbulent spot and a tripped turbulent boundary layer flow using time-resolved tomographic PIV

In this feasibility study the tomographic PIV technique has been applied to time resolved PIV recordings for the study of the growth of a turbulent spot in a laminar flat plate boundary layer and to visualize the topology of coherent flow structures within a tripped turbulent flat plate boundary layer flow. The experiments are performed around (Re x )1/2 ? 450 in a low speed wind-tunnel using four high speed CMOS cameras operating up to 5 kHz. The volume illumination required a multiple-reflection system able to intensify light intensity within the measurement volume. This aspect is deemed essential when a high-speed tomographic PIV system is applied in air flows. The particle image recordings are used for a three dimensional tomographic reconstruction of the light intensity distribution within the illuminated volume. Each pair of reconstructed three-dimensional light distributions is analyzed by 3D spatial cross-correlation using iterative multi-grid schemes with volume-deformation, yielding a correlated time sequence of three-dimensional instantaneous velocity vector volumes. The coherent structures organization is analyzed by 3D-vorticity and -swirling-strength iso-surfaces visualization. In both flow types streaks and hairpin-like or arch vortical structures are most prominent. The data gives insight into the role of these structures for the spatio-temporal arrangement of the wall normal flow exchange mechanisms, especially of the instantaneous Reynolds stress events Q2 and Q4. A description of different self-sustainable flow organizations based on modifications of the hairpin-vortex- and streak-models is given. Two preliminary results are essential: Self-sustainability of a coherent vortical structure depends on the ability to entrain high momentum fluid, initially Q4. And, stream-wise swirl at the near-wall region of arch or hairpin-like vortices has been observed to be rare.Aerospace Design, Integration and OperationsAerospace Engineerin