A Detailed Study: CFD Analysis of NACA 0012 at Varying Angles of Attack

This work reflects the study and detailed analysis of NACA 0012 airfoil at different angles of attack with a constant value of Reynolds Number. The geometrical designing of the airfoil is done using FreeCad and the computational analysis is carried out using Simflow 4.0- OpenFoam Interface. The analysis is fully based upon the concepts of FEM and CFD. The velocity is kept constant with various angles of attack. CFD methods are reliable source of analysis and hence can be replaced with the experimental wind tunnel methods. Boundary layer approaches were taken into consideration using the meshing techniques. The main purpose of this work is to study the symmetric profile of NACA 0012 with varying angles and the behaviour of 0012 at specific conditions. At the end, various graphs are plotted depicting the relationship of Angle of Attack with other dimensionless quantities.

CONSEQUENCES OF THE BASIC LAW OF FLAT INTERLOCKING OF INVOLUTE CYLINDRICAL GEARS

Three consequences based on the basic law of the flat interlocking have been determined that allow the generation of asymmetric tooth profile on different poloidal circles. Gears with asymmetric profile are used in both mechanical engineering and measuring devices. Qualitative indicators of engagement that cannot be accomplished with a symmetric profile have been developed. A specific example of generation III has been presented. The qualitative indicators of engagement, which are invariant to the parameters of the tool, have been improved.

Analysis by FEMof elasto-plastic deformation of beams with associated plate

Для оценки несущей способности балок судовых конструкций надо определять их предельную нагрузку. Существующие расчетные зависимости, приводимые в справочных изданиях, далеко не всегда дают верные рекомендации, когда речь идет о балках с присоединенным пояском обшивки, который может намного превосходить размер свободного пояска. В работе проведен сравнительный анализ оценки предельной нагрузки, определяемой аналитически и путем упругопластического расчета методом конечных элементов с варьированием ширины присоединенного пояска. Рассматривался вариант упругопластического нагружения с линейным упрочнением. Полученные результаты показали, что приводимая в справочнике по СМК, зависимость для оценки предельной нагрузки балок с асимметричным профилем не совсем корректна из-за неполного включения присоединенного пояска в работу. Это дает завышенные значения предельной нагрузки. Проверены были также рекомендации по оценке прогибов балок в предельном состоянии, показавшие, что рекомендации справочника по СМК приводят к заниженным значениям прогибов. Для балок симметричного профиля расчетные зависимости справочника дают вполне удовлетворительные результаты. Отмечено, что если поперечная нагрузка вызывает текучесть стенки балки от сдвига, то влияние ширины присоединенного пояска практически не сказывается на ее несущей способности. Проанализировано также влияние величины секущего модуля на предельную нагрузку балки. For estimation of load capacity of the ship beams it is necessary to determine their limit load. Existing analytical relations, indicated in different manuals, not always give true recommendations when talk is about beams with associated plate many times exceeding dimensions of free flange. In this paper fulfilled comparative analysis of limit load, determined with analytical and elastic-plastic calculation by the finite element method. It was considered case of elastic-plastic deformation with lineal strain-hardening. Obtained results show that indicated in manual on the ship structural mechanics, relation for estimation of limit load of non-symmetric I-beams is not quite correct because of not complete inclusion of associated plate to the beam deformation. This lead to overestimation of limit loads. It was also shown that recommendations on evaluation of the deflections of beams in elastic-plastic deformations according to mentioned manual lead to much lower values of deflections. For beam with symmetric profile the relations of manual give quite satisfactory results. It was noticed, that if transverse load produces the yielding of web due to shear the influence of width of associated plate has no influence on the load capacity of beam. It was also analyzed influence of value of the strain-hardening modulus on limit load of beam.

Breakdown of Scaling and Friction Weakening in Intermittent Granular Flow

Many materials are produced, processed and stored as grains, while granularity of matter can be crucial in triggering potentially catastrophic geological events like landslides, avalanches and earthquakes. The response of grain assemblies to shear stress is therefore of utmost relevance to both human and natural environment. At low shear rate a granular system flows intermittently by distinct avalanches. In such state the avalanche velocity in time is expected to follow a symmetrical and universal average behavior, whose dependence on the slip size reduces to a scale factor. Analyzing data from long lasting experiments, we observe a breakdown of this scaling: While in short slips velocity shows indeed a self-similar and symmetric profile, it does not in long slips. The investigation of frictional response in these different regimes evidences that this breakdown can be traced back to the onset of a friction weakening, which is of dynamical origin and can amplify instabilities exactly in this critical state, the most frequent state for natural hazards.

Aerodynamic Investigations of an Advanced VIGV Design of Adjustable Geometry for Very High Flow Turning

On the basis of experimental results the new design of a Variable Inlet Guide Vane (VIGV), as can be used for the control and regulation in multishaft compressors, is presented. Main goal of this investigation is a significant increase of the operating range and a reduction of the total pressure loss compared to a currently used basic design. For both designs 2D-cascades were build for detailed measurements in the High-Speed Cascade Wind Tunnel at the Institute of Jet Propulsion at the Universität der Bundeswehr München. The basic design exhibits a symmetric profile with only one segment. In contrast to that the new VIGV design consists of two symmetric vane segments which are arranged pivotable to each other. This provides the advantage of a symmetric profile for a fully opened VIGV associated with a low-loss level. For guidance of the flow, both vane segments can be rotated. Hence, the turning of the flow is split onto two segments. This avoids a huge flow separation on the suction side for high turning angles (Δβ > 30°) which is linked with a strong and abrupt loss increase. Due to the design, the new VIGV exhibits a gap between the two vane segments. Results with opened and sealed gap are presented and discussed. Using a sealing between the segments, a reduction of the profile loss could be detected for all investigated operating conditions. Even without a sealing in the gap, the “low-loss working range” is significantly increased. In addition, it is depicted that the presented results are valid for varying inflow velocities. This broadens the usability of the outcomes. Concluding, it is shown that all aims are achieved. Using the new VIGV design with sealing the low-loss working range can almost be doubled (Δβ > 55°) and the total pressure loss decreases in every working condition compared to the basic design.

Aerodynamic Investigations of a Variable Inlet Guide Vane With Symmetric Profile

In order to determine the aerodynamic behavior of a Variable Inlet Guide Vane as used in multishaft compressors, extensive experimental investigations with a 2D linear cascade have been conducted. All the experiments were performed at the High-Speed Cascade Wind Tunnel at the Institute of Jet Propulsion. They covered a wide range of Reynolds numbers and stagger angles as they occur in realistic turbomachines. Within this work at first the observed basic flow phenomena (loss development, overturning) will be explained. For the present special case of a symmetric profile and a constant decreasing chord length along the vane height, statements about different spanwise position can be made by investigating different Reynolds numbers. The focus of this paper is on the outflow of the VIGV along the vane height. Results for an open flow separation on the suction side are presented, too. Stall condition can be delayed by boundary layer control. This is done using a wire to trigger an early boundary layer transition. The outcomes of the trip wire measurement are finally discussed. The objective of this work is to evaluate the influence of the stagger angle and Reynolds number on the total pressure losses and the deviation angle. The results of the work presented here, gives a better insight of the efficient use of a VIGV.