This paper deals with experimental results of an axial compressor of a small power plant gas turbine engine. Tests were carried out during the engine operation (along operating line of the compressor). Time averaged axial and radial pressure distributions in each individual stage were measured at different rotational speeds. Acceleration and deceleration phases of the engine were divided into reasonable time intervals of constant rotational speeds. Consequently, data logging was performed during steady operation of the engine. Measured parameters included pressure and temperature distributions and air mass flow rate. Test results were used to calculate axial distribution of load factor along the compressor mean line. Experimental results showed that the span wise total pressure reduces from mean line region towards the hub and casing at each stage. No significant variations in load factor of each stage were observed during acceleration and deceleration phases of the engine. Meanline load factor distribution was increasing from compressor head towards its end within experimental rotational speed range.

An analysis of the minimum pressure coefficient on the suction side of the axial-flow pump blades is presented as a design criterion. A Matlab code is used to improve the computer aided design process efficiency and quality. X-Foil software determines the blade profiles' lift and drag coefficients, and a computational fluid dynamics model is applied to certify the pump efficiency. The model is validated from the available experimental data in the literature. The finite volume method is used through the commercial software Ansys CFX, in order to solve the model equations. A case study is presented to design the axial-flow pump for a large circulating water channel that will be used to test ships, naval structures, and hydrokinetic turbines. Particular attention is given to the pump cavitation conditions. The model evaluates the minimum pressure coefficient criterion and pressure coefficient distribution on the blade span, showing satisfactory performance for the pump at the design point and at variable speed.

In this paper, a novel approach is proposed to investigate the progressive collapse damage of prismatic thin walled metal columns with different regular cross sections, under the action of axial quasi-static and impact loads. The present work mainly focuses on implementation of some important factors which have been neglected in other studies. These factors include the effect of reducing impactor velocity and inertia effect during collapse, a mixed collapse mode for crushing mechanism, and consideration of a realistic elasto-plastic model for material. Taking all these factors into account, the analysis led to some parametric algebraic equations without a possible general solution in terms of collapse variables. Consequently, a new theoretical approach was proposed based on previously offered Super Folding Element (SFE) theory, to obtain the closed form explicit relations for the static and dynamic mean crushing forces and collapse variables. The proposed approach considers an analytic-numeric discretization procedure to solve these equations. To evaluate the results, a detailed finite element analysis on square mild steel models was conducted under an axial impact load, using LS-DYNA and ANSYS software programs. Comparison of the experimental results that are available in the literature with those of finite element analysis, shows the applicability of this approach in predicting the collapse behavior in such structures.

The distributions of axial static pressure coefficient and flow fluctuation in the test section which affect aerodynamic measurement in an open jet wind tunnel is presented. In this paper, the flow characteristics of the open jet automotive wind tunnel with passive reinjection and active reinjection were simultaneously investigated by experimental and numerical approaches. The axial static pressure coefficient variations can be reduced by passive or active reinjection, and recycle flow returns to the test section from the loophole is the main reason. The more mass flow rate improves the effect. Meanwhile, it is found that the improvement of the axial static pressure coefficient by reinjection is always better in the condition of 0° collector angle. The turbulence intensity in the collector angle of 15° is lower than that of 0° , and the reinjection increases the turbulence intensity near the collector. The increase of the turbulence intensity by active reinjection in the collector angle of 0° is greater than the collector angle of 15° for the 3. 28° diffusion angle. There are some peaks emerging at the frequencies of 40 Hz and 50 Hz, which indicates that the flow field fluctuations may have induced structural vibration. The peaks at several frequencies increase when the passive and active reinjection are conducted, and the increase of peak is correlate with the increase of the reinjection flow rate. Due to the reduction of average static pressure coefficient and increase of flow fluctuations, the application of passive and active reinjection should be considered at the same time.

Discrete Element Method can be used for numerical analysis of different geotechnical problems such as retaining wall earth pressure distribution. This paper is an effort to use the method in determining active and passive earth pressure distribution behind a retaining wall. Soil mass in the present method is treated as comprising of blocks, which are connected by elasto-plastic Winkler springs. The solution of this method satisfies all equilibrium and compatibility conditions. The method has the simplicity of the classic limit analysis and offers more ability in solving problems in complex geometry and loading conditions such as seismic impacts, pore water pressure, non-homogeneity of the soil reinforced backfill soils, etc. In this paper, the formulation of the method is briefly reviewed. Examples are shown to demonstrate the applicability of the method for analysis of earth pressure behind a retaining wall including dynamic lateral pressure of non-homogeneous soil. The results are compared with previous classic methods. Applicability of DEM for analysis of reinforced soil structure and advantages of this method over conventional methods are also discussed.

Inclined retaining walls with slopes less than perpendicular are appropriate candidates in several engineering problems. Yet, to the knowledge of authors, only a few analytical solution for calculation of active earth pressure on such walls, which will be usually smaller than the same pressure on vertical ones, has been presented neither in research papers nor in design codes. Considering limit equilibrium concept in current research, a new formulation is proposed for determination of active earth pressure, angle of failure wedge and application point of resultant force for inclined walls. Necessary parameters are extracted assuming the pseudo-static seismic coefficient to be valid in earthquake conditions. Moreover, based on Horizontal Slices Method (HSM) a new formulation is obtained for determining the characteristics of inclined walls in granular and or frictional cohesive soils. Findings of present analysis are then compared with results from other available methods in similar conditions and this way, the validity of proposed methods has been proved. Finally according to the results of this research, a simplified relation for considering the effect of slope in reduction of active earth pressure and change in failure wedge in inclined retaining walls has been proposed.

Static and pseudo-static analysis based on the Discrete Element Method (DEM) is presented for active and passive earth pressure distribution behind a retaining wall. Soil mass in the present model is treated as comprising blocks which are connected by elasto-plastic Winkler springs. The solution of this method satisfies all equilibrium and compatibility conditions. Examples are shown to demonstrate the applicability of the method for analyses of earth pressure behind a gravity wall, including pseudo-static pressure of earth and lateral pressure of non homogeneous soil. The applicability of DEM for analyses of reinforced soil structures and the advantages of this method over the conventional limit equilibrium method are also discussed.

A simple method which is suitable for determining with reasonable precision the parameters of gas flow system has been proposed. An inverse boundary-value problem is considered. The model of gas flow with the Danckwert’ s boundary conditions in a real measurement system has been analyzed and solved. The tracer technique was applied to determine axial dispersion coefficient of gas phase and Pè clet number. These parameters are commonly used to characterize the flow behavior of fluids. Axial dispersion coefficients were estimated by comparing model solution with recorded TCD signal (an inverse problem as a method for model parameter estimation) employing the Laplace transform technique. The Gaver-Stehfest algorithm for the solution of the mathematical model has been applied. The proposed model of gas show a good agreement with the experimental data. The obtained results show that under operation conditions in the studied system the flow behaviour is neither plug flow nor perfect mixing. The described method is very fast in both experimental and computational part. Simple and errorless derivation of sophisticated model formulas has been possible by application of the Computer Algebra System-type program. The program also simplifies computations. Mathematical manipulations and computations were performed using program Maple® .

A plane subsonic jet was subjected to periodic oscillations in the near nozzle region by a twin vane system. During excitation, the jet was found to spread significantly and entrain mass much more than its steady counterpart. Time averaged static pressure measured in the flow field with a disc probe exhibited prominent well defined suction regions different from that of a steady jet.  

In this research, the free vibration analysis of cylindrical shells with longitudinal stiffeners, i. e. stringer with analytical method, for eight different types of simply supported and clamped boundary conditions is investigated. Ritz method is applied in analytical solution while stiffeners treated as discrete elements. The stiffened shell is loaded axially under static pressure and supports are axially follower force type. Some analytical results for natural frequencies are compared with other’ s experimental and analytical results, which showed good agreement. Furthermore, variations of natural frequencies, fundamental frequency and natural mode shapes for mentioned boundary conditions are studied and in some cases, these results are compared with FEM results. Also, the effect of stiffener eccentricity on natural frequencies, especially fundamental frequency is considered. Furthermore, variations of natural frequencies for different axial static pressure load are considered and with plot of these, the buckling load is determined.