Sharif Digital Repository

In this research, design methods of radial flow compressor volutes are reviewed; the main criteria in volute primary designs are recognized and the most effective ones are selected. The effective parameters, i.e., spiral cross-section area, circumferential area distribution, exit cone, and tongue area of the compressor volute are parametrically studied to identify the optimum values. A numerical model has been prepared and verified through experimental data which are obtained from the designed turbocharger test rig. Different volutes are modeled and numerically evaluated using the same impeller and vane-less diffuser. For each model, the volute total pressure ratio, static pressure recovery... 

During recent years centrifugal-based microfluidic devices known as Lab-on-a-CD have attracted a lot of attentions. Applications of these CD-based platforms are ubiquitous in numerous biological analyses and chemical syntheses. Mixing of different species in microscale is one of the essential operations in biochemical applications where this seemingly simple task remains a major obstruction. Application of centrifugal force, however, may significantly improve the flow agitation and mixing, especially when it is combined with the Coriolis force which acts perpendicular to centrifugal force. In this study, mixing process in minichambers located on a rotating platform under a periodic... 

Development of design and production technology of centrifugal pumps for achieving better performance and less energy consumption in these devices has increasingly been taken into consideration. This is due to the fact that centrifugal pumps have an important contribution in industrial applications and energy consumption around the world. Accordingly, the international standards of centrifugal pumps, urge more precise analysis systems for obtaining the performance curves of these pumps. For this reason, a complete, precise and real-time monitoring and performance analysis system for centrifugal pumps is introduced in this paper. The pump characteristics are measured by precise measuring... 

During recent years centrifugal-based microfluidic devices known as Lab-on-a-CD have attracted a lot of attentions. Applications of these CD-based platforms are ubiquitous in numerous biological analyses and chemical syntheses. Mixing of different species in microscale is one of the essential operations in biochemical applications where this seemingly simple task remains a major obstruction. Application of centrifugal force, however, may significantly improve the flow agitation and mixing, especially when it is combined with the Coriolis force which acts perpendicular to centrifugal force. In this study, mixing process in minichambers located on a rotating platform under a periodic... 

A fully coupled numerical analysis using Biot's theory with u-p formulation considering variable permeability during liquefaction is used in this study to simulate liquefaction induced lateral spreading phenomenon. A centrifuge test performed on liquefiable soil at Rensselaer Polytechnic Institute is simulated using the developed model. The numerical results are in good agreement with experimental observations. A number of numerical simulations under different geometric, site-specific, and ground acceleration parameters have been carried out in the course of this study. Based on the statistical analysis conducted on the results of 31 different models, a new relation is proposed for... 

A semi-analytical thermoelasticity solution for hollow and solid rotating axisymmetric disks made of functionally graded materials is presented. The radial domain is divided into some virtual sub-domains in which the power-law distribution is used for the thermomechanical properties of the constituent components. Imposing the necessary continuity conditions between adjacent sub-domains, together with the global boundary conditions, a set of linear algebraic equations are obtained. Solution of the linear algebraic equations yields the thermoelastic responses for each sub-domain as exponential functions of the radial coordinate. Some results for the stress, strain and displacement components... 

A sixteen node cylindrical super element is presented for evaluating the free vibration characteristics of a rotating laminated cylinder with conventional boundary conditions. It is shown that the natural frequencies are affected considerably when the centrifugal force is also taken into account. The vibration frequencies of rotating finite cylinder, obtained by conventional finite element are used to evaluate the accuracy of this approach. The special case of a stationary cylinder with zero spinning velocity is also considered as a check on this method. Results indicate only few number of cylindrical super elements are capable of predicting the natural frequency of the rotating cylinder... 

Rapid isolation of white blood cells (WBCs) from whole blood is an essential part of any WBC examination platform. However, most conventional cell separation techniques are labor-intensive and low throughput, require large volumes of samples, need extensive cell manipulation, and have low purity. To address these challenges, we report the design and fabrication of a passive, label-free microfluidic device with a unique U-shaped cross-section to separate WBCs from whole blood using hydrodynamic forces that exist in a microchannel with curvilinear geometry. It is shown that the spiral microchannel with a U-shaped cross-section concentrates larger blood cells (e.g., WBCs) in the inner... 

This research explores the effectiveness of the use of stiff diaphragm walls next to a rocking foundation through numerical simulation. This improvement technique is used as a means to increase in subsoil peripheral confinement and reduce rocking-induced settlement. The numerical model was verified by the centrifuge test of rocking shallow foundations on clay under cyclic loading. A parametric study was conducted to explore the effect of three stiff wall shapes on the performance of a rocking system. The general conclusion of the parametric investigation is that the use of stiff diaphragm walls reduced the sinking-dominated settlement response of the rocking system. © 2019 Taylor & Francis... 

The blade element momentum (BEM) theory is based on the actuator disc (AD) model, which is probably the oldest analytical tool for analysing rotor performance. The BEM codes have very short processing times and high reliability. The problems of the analytical codes are well known to the researchers: the impossibility of describing inside the one-dimensional code the three-dimensional (3D) radial flows along the span-wise direction. In this work, the authors show how the 3D centrifugal pumping affects the BEM calculations of a wind turbine rotor. Actually to ascertain the accuracy of the analytical codes, the results are compared with rotor performance, blade loads and particle image... 

This paper is concerned with a quasi-3D design method for the radial and axial diffusers of a centrifugal compressor on the meridional plane. The method integrates a novel inverse design algorithm, called ball-spine algorithm (BSA), and a quasi-3D analysis code. The Euler equation is solved on the meridional plane for a numerical domain, of which unknown boundaries (hub and shroud) are iteratively modified under the BSA until a prescribed pressure distribution is reached. In BSA, unknown walls are composed of a set of virtual balls that move freely along specified directions called spines. The difference between target and current pressure distributions causes the flexible boundary to deform... 

Gas turbine has broad applications in variety of industries. The developing gas turbine efficiency is of great engineering concern. This appeals to more precise modeling as somewhat inevitable. Modeling plays a decisive and essential role not only in all design phases, but also in development and manufacturing process to investigate performance of an engine. In this research, components of a gas turbine including air intake, axial and centrifugal compressors, combustion chamber and axial turbine are investigated. A novel dimensionless modeling approach is introduced and then, the engine performance parameters are predicted. Setting up a systematic series of experiments on the existing engine... 

Design and optimization of centrifugal compressors, based on main blades configuration of impeller have been vastly discussed in open literature, but less researches have addressed splitters. In this research, the impeller of a commercial turbocharger compressor is investigated. Here, profiles of main blades are not changed while the effect of changing the configuration of splitters is studied. An optimization study is performed to find the best configuration using genetic algorithm over a complete operating curve of the compressor. CFD codes with experimental support are used to predict the compressor performance. Quantumetric tests beside destructive analysis of two impellers are... 

Particle dispersion in the vortex flow has been one of the most interesting subjects in recent years. Bidirectional vortex flow field is an industrial sample of rotating flow which is used to obtain advantages of better mixing and combustion. In this work penetration and dispersion quality of particles which are entering from various positions on the vortex engine walls have been numerically predicted. Head side, end side, and sidewall are considered as the entering positions. The particle has been assumed to be a rigid sphere. Initial velocity, diameter, and density of entering particles are assumed to be known. If the particle length scale is considered not to be comparable with the... 

Diabetes mellitus is a global endemic with a rapidly increasing prevalence in both developing and developed countries. Recently, hemoglobin A1c has been recommended by the American Diabetes Associations as a possible substitute for fasting blood glucose for the diagnosis of diabetes, because it is an indicator of long-term glycemic control. Also, centrifugal microfluidic systems have good potential for use in the point of care testing systems. In this study, a centrifugal microfluidic disc was designed and manufactured to measure hemoglobin A1c in whole blood using an immunoturbidimetry based method. Also, a new passive valve, named septum valve, was presented to precisely control the entry... 

This paper presents a comprehensive 3D numerical simulation of reacting flows in micro scale dimension through centrifugal, or Lab-On-a-CD (LOCD), and pressure-driven, or Lab-On-a-Chip (LOC) devices. Three different serpentine channel configurations (rectangular, triangular and sinusoidal) are investigated. In these configurations, two chemical species enter from two inlets and according to an irreversible chemical reaction, start yielding other species. Both Newtonian and generalized Newtonian fluids are considered in the simulations and the results are compared for both LOC and LOCD devices. Besides, the effects of different parameters such as the aspect ratio of channels’ cross section,... 

A rotating closed loop pulsating heat pipe (RCLPHP) was experimentally investigated as a passive heat sink for rotary equipment cooling. The effects of heat input, rotational speed, filling ratio, and working fluid on the thermal resistance of RCLPHP were studied. Pure water and ethanol were used as working fluids with filling ratios of 30%, 50%, and 70% by volume, and the RCLPHP was tested at four rotational speeds: 200, 400, 600, and 800 rpm. The results showed that the best filling ratio for both water and ethanol is 50% and proved that the RCLPHP is able to work efficiently in a wide range of rotational speed. Moreover, it was observed that at the optimum filling ratio for ethanol and... 

In this paper, vibration analysis of rotating laminated composite cylindrical shells using a combination of the layerwise theory and wave propagation approach is investigated. This combination enables us to study all the conventional boundary conditions in our analysis. Results obtained have been compared with those available in the literature and a good agreement has been observed. In contrast to the Equivalent Single Layer theories (ESL), the layerwise theory is constructed on the basis ofC°- continuity through the laminate thickness. For the surface of the shell, a displacement field based on the wave propagation approach is proposed. The effect of Coriolis and centrifugal accelerations... 

Dynamic compaction (DC) is a popular soil improvement method that is extensively used worldwide. DC treatment design is usually carried out based on past experiences and empirical relations. To establish a rational design approach, all important factors affecting the DC process should be taken into account. In this paper, a finite element code is developed for modeling the impact behavior of dry and moist granular soils. The code is verified with the results of some centrifuge tests. Several analyses were conducted in order to study the effects of energy/momentum per drop, tamper base radius, and number of drops on compaction degree, compacted depth, and extension of the improved zone in the... 

The performance of a gas centrifuge that is used for isotopes separation is dependent on the gas flow inside it. In this study, for modeling the UF6 gas flow, an Implicit Coupled Density-Based (ICDB) solver, was developed in OpenFOAM. To validate the ICDB solver, the gas flow within the rotor in total reflux state was compared with the analytical solution obtained by Onsager model and the numerical solution obtained by the Fluent software. The results showed that the ICDB solver had acceptable accuracy and validity. Also the computational efficiency of Roe, AUSM (Advection Upstream Splitting Method) and AUSM+ up schemes were compared. The results showed AUSM+ up scheme is efficient. Then,...