Centrifugal Force

We conduct detailed velocity measurements in the turbulent boundary layer, which is developed on a rotating disk opposed to a turbulent jet perpendicularly impinged onto it. The effect of rotation is remarkable in both the skew in the mean flow and in the centrifugal force. We propose a non-dimensional parameter that correlates these two effects and classifies the velocity field. We find the modification of the turbulence structure due to the disk rotation in the increase of the normal stress component in the circumferential direction. The increases in the other stress components are found to be indirect, i.e., re-distribution from the circumferential normal stress is the source of modification in the turbulence structure.

Body roll is one of the most common phenomenon that occurs in a car during high speed turnings on curve roads. Hence to avoid any kind of tilting in the vehicle body, while it is turning, he reaction forces due to centrifugal forces have to be negated. In this paper we will discuss about three mechanisms which can counter body roll and assist in efficient cornering of the vehicle thereby providing safety to the passengers and enhance better steering control.

The technology for electrostatic enhancement of coalescence of water droplets in oil emulsions is critically reviewed. Historically, the electrostatic coalescer was invented for the petroleum-related industries in California [US Patent 987 115 (1911)]. Nowadays, this technology is generally considered for the separation of an aqueous phase dispersed in a dielectric oil phase with a significantly lower dielectric constant than that of the dispersed phase. Various designs have been introduced, with most using alternating current (AC) electric fields with mains frequency (50 or 60 Hz). The direct current (DC) electric field has been less common in the past as compared to the AC. In 1981, the concept of pulsed DC electric fields was introduced, together with insulated electrodes [Trans. IChemE 59 (1981) 229-237; UK Patent 217 1031A (1986)]. Since then, this has become more common in the electrocoalescence technology. Pulsed DC and AC fields are especially useful, when the aqueous phase content of the emulsion is high, to prevent short-circuiting between the pair of electrodes. Processing of oil from old wells is a good example, where the volumetric water content could vary significantly. Reported work by some workers indicates the existence of an optimum frequency, which depends on the electrode coating material, its thickness and the liquid emulsion composition. This is however, a contentious issue which has not been completely resolved. The characteristics and geometry of the electrode system (generally cylindrical or plate) influence the performance of the electrostatic coalescer, and are closely related to the type of the applied electric field and the emulsion used. There are basically two types of electrode: uninsulated electrode and insulated electrode. Combination of electrocoalescence and mechanical separation (e.g., centrifugal force) has also been introduced. Heating and the addition of chemicals have been shown to further enhance the electrocoalescence of water droplets. Other methods that can be combined with the electrical treatment are filtration, methods employing high pressure and temperature, and mixing. This review paper also looks at some of the current specific industrial applications using the electrocoalescence technology. Besides the oil and petroleum industries, this technology has potential applications in the edible oil industries such as palm oil, sunflower oil and vegetable oil processing. Most of the currently available equipment is very big and bulky, having a large inventory of emulsion. Therefore, we see the future trend for new developments to be in the direction of inventing small portable devices, incorporating features such as optimum electric fields and combined electrical and centrifugal forces to further enhance the separation of water-in-oil emulsions. Furthermore, a better understanding of the fundamentals of electrocoalescence will enable a better design of the geometry of the electrodes, of the flow field with respect to the electric fields, the type of dispersion used and the type of the applied electric field.

The importance of centrifugation in the pharmaceutical industry has rarely been studied. Centrifugation is one of the most important and widely applied research techniques in biochemistry, cellular and molecular biology and in evaluation of suspensions and emulsions in pharmacy and medicine. This review focuses on the basics and principle of centrifugation, classes of centrifuges, types of centrifuge separations, different types of density gradient media, classification of industrial centrifuges, types of industrial centrifuges and applications of centrifugation in the pharmaceutical industry. Centrifugation, clearly, plays an important role in the pharmaceutical industry in the production of bulk drugs, biological products, determination of molecular weight of colloids and in the evaluation of suspensions and emulsions.

James Clerk Maxwell is credited with having brought electricity, magnetism, and optical phenomena, together into one unified theory. The details of what exactly he did were however seriously distorted in twentieth century physics textbooks. Maxwell is most famous in connection with a set of equations which bear his name, but these equations have been totally removed from the physical context within which Maxwell was working, and outside of that physical context the full meaning of these equations is lost. Maxwell was working within the context of a sea of tiny aethereal vortices pressing against each other with centrifugal force. The centrifugal force bit was crucial for explaining magnetic repulsion, yet both centrifugal force and aether are stringently denied by modern physicists who nevertheless continue to hail Maxwell for the equations that he derived by using these very concepts which they deny. This irony seems to be explained at least in part because they think that the equations can be re-derived using Einstein's special theory of relativity. Such an erroneous belief stems from the fact that one of the most important of Maxwell's equations has been wrongly credited to Lorentz and referred to as the Lorentz force law and treated as 'supplementary' to Maxwell's equations. Einstein, being ignorant of Maxwell's original equations and the fact that they contained the Lorentz force law, hence wrongly believed that the equations contained no convective term, and so he made the erroneous conclusion that Maxwell's equations mean that the speed of light must be frame independent in contradiction of classical principles of vector addition of velocities. This erroneous conclusion led Einstein to his special theory of relativity in 1905, and it subsequently led to the erroneous belief amongst both relativists and many anti-relativists, that Einstein's special theory of relativity follows naturally from Maxwell's theory, when in fact Maxwell and Einstein were not even remotely working along the same lines.

The modern teaching is that centrifugal force only exists as a fictitious force in a rotating frame of reference, and that the only force acting in an inertial frame of reference when a body undergoes circular motion is an inward acting centripetal force. On the contrary however, it is here proposed that a rotating frame of reference, rather than creating a fictitious centrifugal force, actually masks the existence of a very real inertial centripetal force that has gone unrecognized in the literature. When the books are correctly balanced, it will be demonstrated that centrifugal force is a real force, closely related to kinetic energy, and observable in any frame of reference.

This paper reviews the current understanding of electrocoalescence of water droplets in oil, highlighting particularly the mechanisms proposed for droplet–droplet and droplet–interface coalescence under the influence of an applied electric field, as well as various factors influencing the ...

an experimental analysis of a two stage mechanical oscillator has been provided in the following paper. A two stage mechanical oscillator acts as a mechanical amplifier multiplying the input energy provided at the input side to provide an amplified output. A two stage mechanical oscillator is a simple mechanism consisting of a see-saw arrangement i.e., massive lever pivoted on a support. On one side of the lever hangs a pendulum with a bob of mass, m. Input energy to the mechanism is provided by raising the pendulum to a height h, and then releasing it. The pendulum oscillates about the pivot point due to the unbalance on the input side as a result of oscillation of the pendulum about the pendulum's pivot point. Due to the unbalance the other side of the lever also undergoes to and fro motion about the pivot point, which can be coupled to generator, motors, mechanical presses etc and hence act as the output side of the mechanism. The oscillations continue until damped due to various factors like frictional and inertial resistances. Therefore, in theory the above mechanism can provide efficiency over unity. An experimental analysis is done calculating energies provided at the input and output side to measure the efficiency of the mechanism.

The present work considers the turbulent flow inside an annular rotor-stator cavity with and without centrifugal throughflow. Extensive measurements performed using a two component laser Doppler anemometer technique, and pressure transducers are compared to numerical predictions based on one-point statistical modeling using a low-Reynolds number second-order full-stress transport closure. A study of the flow control parameters is performed, and, for the first time, a better insight into the transition from Batchelor to Stewartson types of flow is gained from this study. The advanced second-order model is confirmed to be the adequate level of closure to describe such complex flows.

Computational fluid dynamics (CFD) simulations of the hydrodynamic behavior of rotating fluidized beds in static geometry (RFB-SG) are carried out for gas-solid flows. The rotating motion of the reactor bed is induced by the tangential injection of the gas along the circumference of the fluidization chamber. Steep gradients in the gas velocity fields both in radial and tangential direction generate turbulence. The radial and tangential drag forces fluidize the particle bed in both radial and tangential direction.

A passive twist control is proposed as an adaptive way to maximize the overall efficiency of the small-scale rotor blade for multifunctional aircrafts. Incorporated into a database of airfoil characteristics, Blade Element Momentum Theory is implemented to obtain the blade optimum twist rates for hover and forward flight. In order to realize the required torsion of blade between hover and forward flight, glass/epoxy laminate blade is proposed based on Centrifugal Force Induced Twist concept. Tip mass is used to improve the nosedown torsion and the stabilization of rotating flexible blade. The laminate blades are tested in hover and forward flight modes, with deformations measured by Laser Displacement Sensor. Two Laser Displacement Sensors are driven by the tracking systems to scan the rotating blade from root to tip. The distance from blade surface to a reference plane can be recorded section by section. Then, a polynomial surface fitting is applied to reconstruct the shape of rotating blade, including the analysis of measurement precision based on the Kline-McClintock method. The results from deformation testings show that nose-down torsion is generated in each flight mode. The data from a Fluid Structure Interaction model agrees well with experimental results at an acceptable level in terms of the trend predictions.

Cylindrical slices (2 cm diameter, 0.5 cm thickness) of potatoes and apples were immersed in three different osmotic solutions: 70% (w/w) sucrose, 30% (w/w) NaCl, and 15% (w/w) NaCl and 450/ ( / ) o w w sucrose. Osmotic solutions and food samples were placed into stainless steel containers and centrifuged at 64 x g using a tabletop centrifuge at 30°C to perform osmotic dehydration. Results obtained showed that solids uptake by the food samples was always lower when centrifugal force was applied to the system. Under centrifugal force application, and with the osmotic solution containing both NaCl and sucrose, potato slices lost ca. 70% of their original moisture after 6 h of osmodehydration, whereas only 2% of the solutes were taken by the samples. In contrast, osmotic dehydration of static samples for the same time removed ca. 65% of the moisture, but 15% of their original weight was gained by absorption of solids from the osmotic solution. For apple slices, similar results were obtained: 83% water lost, and 6% solids gained for the dynamic system, compared with 75 and 12% respectively, for the static system.

This work investigates the mechanical behaviour of a rotor in working conditions. The rotor is a part of the high-speed integrated flywheel energy storage system designed at University of Berkley. It has a sinusoidal profile in order to achieve a sinusoidal MMF waveform with no harmonics. Mechanical behaviour is analysed using SolidWorks software. Firstly, the stress analysis of the rotor subjected to the centrifugal force is investigated with angular velocity of 75000 rpm. Areas of maximum stresses are found and it is shown that the basic analytical solutions for maximum stresses in rotating discs cannot be used for this type of rotors. Thus, the numerical analysis seems to be the only option for this purpose. Secondly, the frequency analysis is carried out and main harmonics are identified.

This paper presents an analysis and experiment of centrifugal force for microfluidic Enzyme-Linked Immunosorbent Assay (ELISA) on a compact-disc (CD) platform. The ELISA CD was designed based on the centrifugal force as a driving force while capillary force acts as preventing barrier. The CD composed of 2 layers: the substrate layer is made of PMMA and the top layer is laminated with an Adhesive Sealing Films (ASF) or thermal seal. The PMMA substrate was fabricated by CNC micromachining. The ELISA CD consists of 7 reservoirs: waste, detection, serum, conjugate, washing solution, substrate and stopping solution. In the experiment, the reservoirs were filled with colour liquid and the fluid flow behaviour of the liquid in the CD was studied and monitored by a customized CD spin stand system equipped with visualization system. The experimental test results show an average of 9% error when compared with the theoretical calculation of burst frequency for all the reservoirs. © 2010 IEEE.

ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5742282

In this study, Al-5mass%Zr functionally graded materials (FGMs) were fabricated by the centrifugal solid-particle method (CSPM) under applied centrifugal force of 30, 60 and 120G (units of gravity). Microstructural observation along the centrifugal force direction showed that Al 3 Zr platelet particles are almost oriented normal to the applied centrifugal force direction. Volume fraction of Al 3 Zr particles increases close to the ring surface. Moreover, this distribution range of Al 3 Zr particles becomes broader with decreasing the applied centrifugal force. The wear anisotropy of the fabricated Al/Al 3 Zr FGMs was strongly influenced by the platelet particles orientation at the test position. Investigating both of the worn surface morphology and the sub-worn surface layer showed that plastic deformation induced wear is the dominant mechanism during the wear process of Al/Al 3 Zr FGMs samples. Therefore, some of the tested samples were severely deformed and an Al 3 Zr particles-free layer containing Al-Zr supersaturated solid solution was observed very near to the worn surface during the wear test.

This article takes a closer look at the bonding and stability mechanisms within the electron-positron dipole sea and how these result in the double helix theory of the magnetic field. The physical connection between the inertial forces and magnetic repulsion will be further investigated.

The results of the milling experiments of different mineral ores and laboratory wear testing with different abrasives have shown that the abrasivity of treated materials does not depend only on their hardness, but, to a great extent, on the particle shape of the materials. The grindability of materials milled by collision depends on the properties of materials as well on the treatment parameters (specific treatment energy). The aims of this investigation were (1) to study the abrasivity and the grindability of different minerals (granite, quartzite, etc.) and to predict the relative wear resistance of the materials prospective for the grinding media of milling equipment, using a centrifugal type impact wear tester. Experiments conducted with abrasives of different hardness and with particles of different shape have shown that the wear rate of materials used as wear resistant materials in grinding devices depend more on the angularity of abrasive particles than on their hardness. It was shown that the grindability depends more on the composition and properties (fracture toughness, homogeneity of the structure) than on the hardness of the mineral ores. The main size reduction occurs at first collision, later in the multiple milling of mineral materials particle rounding takes place. The angularity parameter has good correlation with the wear rate in the case of the studied commercial steels as well as with metal matrix composites. Experiments with cermets showed that erosion does not practically depend on abrasive particle shape.

Current methods of nuclear isolation from liver disrupt the plasmalemmae via homogenization and separation of the nuclei by high centrifugal force (HCF) through gradients of sucrose or other substances for up to 80 min. The use of HCF for such a long time increases the potential for nuclear damage and degradation by endogenous proteases. We compared four combinations of alterations to classical nuclear isolation methods as follows. Mouse liver was gently crushed through a fine mesh with and without in vivo perfusion with collagenase. The cell suspension was centrifuged at 600g to remove gross debris and then at moderate centrifugal force (MCF, 16,000g) or high centrifugal force (HCF, 70,000g) through sucrose gradients for 30 min. The purity of the isolated nuclei was assessed biologically and morphologically, including analyses of representative marker proteins for nuclei and cytoplasm. The results indicate that MCF and no collagenase provided the highest nuclear integrity and purity, whereas MCF with collagenase is a viable option if priority is given to yield. The method is especially suited for small samples and so should facilitate studies with human liver biopsies and livers from mice, the most widely used species for gene targeting.

The new concept of a rotating fluidized bed in a static geometry (RFB-SG) is presented. The rotating motion of the particle bed and the tangential fluidization of the solids are obtained by the tangential injection of the fluidization gas via multiple gas inlet slots in the outer cylindrical wall of the fluidization chamber. The solids experience a radially outwards centrifugal force. The gas, on the other hand, is forced to move radially inwards towards a chimney with one or more outlet slots, creating a radially inwards gas-solid drag force and fluidizing the solids radially. The new fluidization concept is experimentally investigated and proven using one and the same non-optimized fluidization chamber design with either large diameter, low density polymer particles or small diameter, higher density Alumina particles. The fluidization chamber is operated in continuous mode, at different solids loadings and in the vertical and horizontal position. © 2007 American Institute of Chemical Engineers AIChE J, 2007

a b s t r a c t An understanding of particle dynamics is important when determining material erosive wear in any erosion tester, because particle impact conditions are primarily influenced by particle acceleration. A better understanding of particle dynamics in the testers will aid the control of erosion test conditions and therefore improve the accuracy of measurement. In this paper, particle dynamics in the two most popular erosion testers, the centrifugal erosion tester and the gas-blast erosion tester, has been discussed in detail. Mechanisms of particle acceleration in the two types of testers were explored and computational models of particle dynamics were described briefly. A review of the experimental determination of important characteristics of particle dynamics (such as particle velocity, particle trajectory, particle dispersion and particle rotation) showed how they influenced particle movement and therefore the particle impact conditions. In addition, comparison of the particle dynamics in the two types of erosion testers showed that differences of particle acceleration may lead to significantly different results at identical pre-set test conditions. It may be concluded that it is not possible to directly compare the results obtained in different types of erosion testers even under notionally identical test conditions.

A 3-D potential-based boundary element method (BEM) is coupled with a 3-D finite element method (FEM) for the time-dependent hydroelastic analysis of cavitating propulsors. The BEM is applied to evaluate the moving cavity boundaries and fluctuating pressures, as well as the added mass and hydrodynamic damping matrices. The FEM is applied to analyze the dynamic blade deformations and stresses due to pressure fluctuations and centrifugal forces. The added mass and hydrodynamic damping matrices are superimposed onto the structural mass and damping matrices, respectively, to account for the effect of fluid-structure interaction. The problem is solved in the time-domain using an implicit time integration scheme. An overview of the formulation for both the BEM and FEM is presented, as well as the BEM/FEM coupling algorithm. Numerical and experiment validation studies are shown. The effects of fluid-structure interaction on the propeller performance are discussed.

The floating frame of reference formulation is currently the most widely used approach in flexible multibody simulations. The use of this approach, however, has been limited to small deformation problems. In this investigation, the computer implementation of the newabsolute nodal co-ordinate formulationand its use in the small and large deformation analysis of flexible multibody systems that consist of interconnected bodies are discussed. While in the floating frame of reference formulation a mixed set of absolute reference and local elastic co-ordinates are used, in the absolute nodal co-ordinate formulation only absolute co-ordinates are used. In the absolute nodal co-ordinate formulation, new interpretation of the nodal co-ordinates of the finite elements is used. No infinitesimal or finite rotations are used as nodal co-ordinates from beams and plates, instead, global slopes are used to define the element nodal co-ordinates. Using this interpretation of the element co-ordinates, beams and plates can be considered as isoparametric elements, and as a result, exact modelling of the rigid body dynamics can be obtained using the element shape function and the absolute nodal co-ordinates. Unlike the floating frame of reference approach, no co-ordinate transformation is required in order to determine the element inertia. The mass matrix of the finite elements is a constant matrix, and therefore, the centrifugal and Coriolis forces are equal to zero when the absolute nodal co-ordinate formulation is used. Another advantage of using the absolute nodal co-ordinate formulation in the dynamic simulation of multibody systems is its simplicity in imposing some of the joint constraints and also its simplicity in formulating the generalized forces due to spring-damper elements. The results obtained in this investigation show an excellent agreement with the results obtained using the floating frame of reference formulation when large rotation–small deformation problems are considered.

This paper introduces novel vacuum/compression valves (VCVs) utilizing paraffin wax. A VCV is implemented by sealing the venting channel/hole with wax plugs (for normally-closed valve), or to be sealed by wax (for normally-open valve), and is activated by localized heating on the CD surface. We demonstrate that the VCV provides the advantages of avoiding unnecessary heating of the sample/reagents in the diagnostic process, allowing for vacuum sealing of the CD, and clear separation of the paraffin wax from the sample/reagents in the microfluidic process. As a proof of concept, the microfluidic processes of liquid flow switching and liquid metering is demonstrated with the VCV. Results show that the VCV lowers the required spinning frequency to perform the microfluidic processes with high accuracy and ease of control.

http://www.ncbi.nlm.nih.gov/pubmed/23505528
dx.plos.org/10.1371/journal.pone.0058523

The technology for electrostatic enhancement of coalescence of water droplets in oil emulsions is critically reviewed. Historically, the electrostatic coalescer was invented for the petroleum-related industries in California [US Patent 987 115 (1911)]. Nowadays, this technology is generally considered for the separation of an aqueous phase dispersed in a dielectric oil phase with a significantly lower dielectric constant than that of the dispersed phase. Various designs have been introduced, with most using alternating current (AC) electric fields with mains frequency (50 or 60 Hz). The direct current (DC) electric field has been less common in the past as compared to the AC. In 1981, the concept of pulsed DC electric fields was introduced, together with insulated electrodes [Trans. IChemE 59 (1981) 229-237; UK Patent 217 1031A (1986)]. Since then, this has become more common in the electrocoalescence technology. Pulsed DC and AC fields are especially useful, when the aqueous phase content of the emulsion is high, to prevent short-circuiting between the pair of electrodes. Processing of oil from old wells is a good example, where the volumetric water content could vary significantly. Reported work by some workers indicates the existence of an optimum frequency, which depends on the electrode coating material, its thickness and the liquid emulsion composition. This is however, a contentious issue which has not been completely resolved. The characteristics and geometry of the electrode system (generally cylindrical or plate) influence the performance of the electrostatic coalescer, and are closely related to the type of the applied electric field and the emulsion used. There are basically two types of electrode: uninsulated electrode and insulated electrode. Combination of electrocoalescence and mechanical separation (e.g., centrifugal force) has also been introduced. Heating and the addition of chemicals have been shown to further enhance the electrocoalescence of water droplets. Other methods that can be combined with the electrical treatment are filtration, methods employing high pressure and temperature, and mixing. This review paper also looks at some of the current specific industrial applications using the electrocoalescence technology. Besides the oil and petroleum industries, this technology has potential applications in the edible oil industries such as palm oil, sunflower oil and vegetable oil processing. Most of the currently available equipment is very big and bulky, having a large inventory of emulsion. Therefore, we see the future trend for new developments to be in the direction of inventing small portable devices, incorporating features such as optimum electric fields and combined electrical and centrifugal forces to further enhance the separation of water-in-oil emulsions. Furthermore, a better understanding of the fundamentals of electrocoalescence will enable a better design of the geometry of the electrodes, of the flow field with respect to the electric fields, the type of dispersion used and the type of the applied electric field.

A series of analysis and testing procedures for small turbine engines blades are presented. These procedures can be used to (i) verify the critical failure modes, and (ii) propose approaches for improving the performance, reliability and safety of engine blades in service. The procedures include metallographic examination, chemical ingredient analysis, vibration and modal analysis, stress analysis, fatigue life prediction and modal testings with and without coating. For the particular small turbine engine considered, it is demonstrated that the most probable failure mode for blades is fatigue fracture rather than creep fracture. Possible approaches to enhance the fatigue performance and reliability of engine blades have been proposed and investigated. These include the surface coating, the use of high strength material, and a reduction of the number of stators. Among these approaches, a reduction of the number of stators from 17 to 14 is most beneficial, because it removes vibrational frequencies of the turbine engine from the operating frequencies, thus significantly reducing the vibrational level of engine blades. The vibrational stress in blades can thus be reduced to a level below the fatigue limit.

The stability and onset of convection in a rotating fluid saturated porous layer subject to a centrifugal body force and placed at an offset distance from the center of rotation is investigated analytically. The marginal stability criterion is established in terms of a critical centrifugal Rayleigh number and a critical wave number for different values of the parameter representing the dimensionless offset distance from the center of rotation. At the limit of an infinite distance from the center of rotation the results are identical to the convection resulting from heating a porous layer from below subject to the gravitational body force. At the other limit, when the parameter controlling the offset distance approaches zero, the results converge to previously found solutions for the convection in a porous layer adjacent to the axis of rotation. The results provide the stability map for all positive values of the parameter controlling the offset distance from the center of rotation, hence bridging the gap between the two extreme limit cases.

The differences of speed characteristics between fixed and movable roller design are compared in this paper, the belt squeezing is analyzed by the test and simulation, the main factor affecting the speed characteristics of CVT is identified. A new theoretical method is provided for CVT design and speed characteristics improvement.

The centrifugal instability mechanism in boundary layers flows over concave surfaces is responsible for the development of streamwise counter-rotating vortices, known as Görtler vortices. These Vortices create two regions in the spanwise direction, the upwash and downwash regions. The downwash region is responsible to compress the boundary layer towards the wall, increasing drag and heat transfer rates. The upwash region does the opposite. In the nonlinear development of the Görtler vortices the upwash region becomes narrow, and the average drag and heat transfer rate is higher than that for a Blasius boundary layer. In the present research, using a Spatial Direct Numerical Simulation, it is analyzed the influence of the Görtler Vortices spanwise wavelength in heat transfer rates. Different wavelengths are analyzed and compared with experiments. 1 The results show that steady Görtler flow can reach heat transfer rates higher than the turbulent values, even without introducing secondary instabilities.

This report addresses the structural analysis and optimization of a composite fan blade sized for a large aircraft engine. An existing baseline solid metallic fan blade was used as a starting point to develop a hybrid honeycomb sandwich construction with a polymer matrix composite face sheet and honeycomb aluminum core replacing the original baseline solid metallic fan model made of titanium. The focus of this work is to design the sandwich composite blade with the optimum number of plies for the face sheet that will withstand the combined pressure and centrifugal loads while the constraints are satisfied and the baseline aerodynamic and geometric parameters are maintained. To satisfy the requirements, a sandwich construction for the blade is proposed with composite face sheets and a weak core made of honeycomb aluminum material. For aerodynamic considerations, the thickness of the core is optimized whereas the overall blade thickness is held fixed so as to not alter the original airfoil geometry. Weight is taken as the objective function to be minimized by varying the core thickness of the blade within specified upper and lower bounds. Constraints are imposed on radial displacement limitations and ply failure strength. From the optimum design, the minimum number of plies, which will not fail, is back-calculated. The ply lay-up of the blade is adjusted from the calculated number of plies and final structural analysis is performed. Analyses were carried out by utilizing the OpenMDAO Framework, developed at NASA Glenn Research Center combining optimization with structural assessment.

This paper presents a model of fully flexible bladed rotor developed in the rotating frame. An energetic method is used to obtain the matrix equations of the dynamic behaviour of the system. The gyroscopic effects as well as the spin softening effects and the centrifugal stiffening effects, taken into account through a pre-stressed potential, are included in the model. In the rotating frame, the eigenvalues' imaginary parts of the latter matrix equation give the Campbell diagram of the system and its stability can be analysed through its associated eigenvalues' real parts. The turbo machine casing is also modelled by an elastic ring in the rotating frame through an energetic method. Thus, the contact problem between the rotor and the stator can be treated as a static problem. Prior to the study of the complete problem of contact between the flexible blades of the rotor and the flexible casing, a simple model of an elastic ring having only one mode shape, excited by rotating loads is developed in the rotating frame too, in order to underline divergence instabilities and mode couplings. Then, the real complex problem of contact between the blades and the casing, without rubbing, is studied. The stable balanced static contact configurations of the structure are found as function of the rotational speed of the rotor. Finally, the results are compared to these of the simple model of rotating spring-masses on an elastic ring.

The boiling mechanism of a liquid film formed on the surface of a smooth horizontal rotating disc was studied using de-ionised water at 2 l/min flow rate, boiling under vacuum at 40°C and 5-10°C wall superheat. Visualization experiments were carried out and video films were taken for rotational speeds from 0 to 1000 rpm. It was observed that nucleate flow boiling prevails in the case of 0 rpm (stationary disc). Nucleate boiling was also observed at 100 and 200 rpm with the number of bubbles and the diameter of the bubbles decreasing as the rotational speed was increasing. At 600 and 1000 rpm rotational speeds, vapor bubbles were not observed. The results of visual observation were in agreement with bubble growth analysis which showed that at heat flux values of 40 kW/m 2 , conditions for bubble growth are favorable at low rotational speeds (<200 rpm) but are unfavorable at high rotational speeds (1000 rpm).

In order to upgrade polymer waste during recycling, separation should take place at high purity. The present research was aimed to develop a novel, alternative separation opportunity, where the polymer fractions were separated by centrifugal force in melted state. The efficiency of the constructed separation equipment was verified by two immiscible plastics (polyethylene terephthalate, PET; low density polyethylene, LDPE), which have a high difference of density, and of which large quantities can also be found in the municipal solid waste. The results show that the developed equipment is suitable not only for separating dry blended mixtures of PET/LDPE into pure components again, but also for separating prefabricated polymer blends. By this process it becomes possible to recover pure polymer substances from multi-component products during the recycling process. The adequacy of results was verified by differential scanning calorimetry (DSC) measurement as well as optical microscopy a...

This paper considers a class of high-speed airjet weaving machines that is characterized by excessive harness frame vibration, resulting in premature failure. This problem is tackled through addition of an auxiliary, input torque balancing mechanism: a centrifugal pendulum, of which the pendulum motion is imposed by an internal cam. While earlier work by the same authors focused on the design, optimization and robustness analysis of this mechanism, the current paper presents experimental results. The considered setup is an industrial weaving machineà blanc equipped with a centrifugal pendulum prototype. Below a critical speed, the prototype functions as predicted and significantly improves the machine dynamics: the drive speed fluctuation is reduced by a factor of 2.5 and the vibration level of the harness frames is halved. Above the critical speed, however, torsional resonance dominates the machine dynamics. This phenomenon is verified on simulation by extending the rigid-body setup model, on which the centrifugal pendulum design is based, with a torsional degree of freedom.

Thermo elastic analysis of a functionally graded cylinder under mechanical and thermal loads is investigated analytically in the present paper. The first order shear deformation theory (FSDT) is employed for analysis of the problem. FSDT recognizes two components for definition of the deformation. Displacement of the mid-plane and rotation about that are two components of deformation. The modulus of elasticity is assumed to vary continuously along the thickness with a power function. Stress strain relation is developed in the cylindrical coordinate system with regarding the thermal strain. Necessary equations for solving the problem have been obtained by taking variation of the energy equation with respect to four assumed functions using Euler equations. The effect of the temperature rising on the distribution of the displacement and stress for different values of nonhomogenous index (n) are investigated in the present paper. Evaluation of the axial displacement of cylinder can be presented as an important result of this paper. Furthermore, the present result is compared with results that were obtained using the plane elasticity theory.

This paper presents a model of fully flexible bladed rotor developed in the rotating frame. An energetic method is used to obtain the matrix equations of the dynamic behaviour of the system. The gyroscopic effects as well as the spin softening effects and the centrifugal stiffening effects, taken into account through a pre-stressed potential, are included in the model. In the rotating frame, the eigenvalues' imaginary parts of the latter matrix equation give the Campbell diagram of the system and its stability can be analysed through its associated eigenvalues' real parts. The turbo machine casing is also modelled by an elastic ring in the rotating frame through an energetic method. Thus, the contact problem between the rotor and the stator can be treated as a static problem. Prior to the study of the complete problem of contact between the flexible blades of the rotor and the flexible casing, a simple model of an elastic ring having only one mode shape, excited by rotating loads is developed in the rotating frame too, in order to underline divergence instabilities and mode couplings. Then, the real complex problem of contact between the blades and the casing, without rubbing, is studied. The stable balanced static contact configurations of the structure are found as function of the rotational speed of the rotor. Finally, the results are compared to these of the simple model of rotating spring-masses on an elastic ring.

Functionally graded materials (FGMs) consisting of Ni-tung (nickel-tungsten carbide) powders with different concentrations of tungsten carbide particles are successfully deposited by a laser-based direct metal deposition (LBDMD) process on 4140 steel substrates. The slurry erosion behaviour of the Ni-tung FGMs is studied at different impingement angles. The slurry erosion tests are performed at Southern Methodist University's Center for Laser-Aided Manufacturing using a centrifugal-force-driven erosiontesting machine. For the purpose of comparison, Ni-tung 40 depositions and 4140 steel samples are also tested. The results indicate that the LBDMD process is able to deposit defect-free Ni-tung FGMs with uniform distribution of tungsten carbide particles in a nickelbased matrix. The slurry erosion resistance of Ni-tung FGMs as observed to be much better than that of the Ni-tung 40 and 4140 steels. The superior slurry erosion resistance of Ni-tung FGMs is attributed to the presence of large amounts of very hard tungsten carbide particles. The material removal rate (MRR) values by erosion decrease with a decrease in the impingement angle, except at a 45 impingement angle on 4140 steel. The relationship among the MRRs, the craters' depth of penetration, the areas of the craters formed, the average surface roughness values, and the impingement angles are established for Ni-tung FGMs, Ni-tung 40, and 4140 steels. The surface profiles of the eroded samples are analysed by measuring the depth of penetration of the craters formed by the slurry jet using a needleshaped probe and a linear scale with a digital readout. The damaged surfaces are characterized by scanning electron microscopy to investigate the possible application of a material failure model, called damage initiation and damage propagation, to the case of the impingement of a mixture of solid and liquid particles on the Ni-tung FGMs, Ni-tung 40, and 4140 steels. The potentiodynamic polarization curves are generated for the three tested materials and to discover the susceptibility of the material in an erosive environment.

Incorporation of nanofluidic elements into microfluidic channels is one approach for adding filtration and partition functionality to planar microfluidic devices, as well as providing enhanced biomolecular separations. Here we introduce a strategy to pack microfluidic channels with silica nanoparticles and microbeads, thereby indirectly producing functional nanostructures; the method allows selected channels to be packed, here demonstrated so that a separation channel is packed while keeping an injection channel unpacked. A nanocapillary array membrane is integrated between two patterned microfluidic channels that cross each other in vertically separated layers. The membrane serves both as a frit for bead packing and as a fluid communication conduit between microfluidic channels. Centrifugal force-assisted sedimentation is then used to selectively pack the microfluidic channels using an aqueous silica bead suspension loaded into the appropriate inlet reservoirs. This packing approach may be used to simultaneously pack multiple channels with silica microbeads having different sizes and surface properties. The chip design and packing method introduced here are suitable for packing silica particles in sizes ranging from nanometers to micrometers and allow rapid (∼10 min) packing with high quality. The liquid/analyte transport characteristics of these packed micro/nanofluidic devices have potential utility in a wide range of applications, including electroosmotic pumping, liquid chromatographic separations, and electrochromatography.

In this study, Al-5mass%Zr functionally graded materials (FGMs) were fabricated by the centrifugal solid-particle method (CSPM) under applied centrifugal force of 30, 60 and 120G (units of gravity). Microstructural observation along the centrifugal force direction showed that Al 3 Zr platelet particles are almost oriented normal to the applied centrifugal force direction. Volume fraction of Al 3 Zr particles increases close to the ring surface. Moreover, this distribution range of Al 3 Zr particles becomes broader with decreasing the applied centrifugal force. The wear anisotropy of the fabricated Al/Al 3 Zr FGMs was strongly influenced by the platelet particles orientation at the test position. Investigating both of the worn surface morphology and the sub-worn surface layer showed that plastic deformation induced wear is the dominant mechanism during the wear process of Al/Al 3 Zr FGMs samples. Therefore, some of the tested samples were severely deformed and an Al 3 Zr particles-free layer containing Al-Zr supersaturated solid solution was observed very near to the worn surface during the wear test.

Abstraet~6rtler instability occurs due to the action of centrifugal forces in boundary layers over curved surfaces, where it most commonly results in the generation of steady streumwise vortices. This study provides a summary of the current knowledge of this phenomenon. All existing experimental evidence is discussed. Experimental facts that bear on the theoretical modelling of the instability are pointed out. Linear theory is discussed in details and compared critically with the available experiments. The nonlinear evolution of the vortices and their effect on the laminar-turbulent transition process are reviewed. The available nonlinear theories and direct numerical simulations are critically compared with the experiments. Centrifugal instability of turbulent boundary layers is discussed in detail. Effects of the instability on heat transfer and the associated buoyancy forces on the instability are discussed. A summary of some outstanding questions is given.

A novel adaptive tracking control law for nonlinear Hamiltonian multi-input-multi-output (MIMO) systems with uncertain parameters in the actuator modeling as well as the inertia and/or the Coriolis and centrifugal terms is developed. The physical properties of the Hamiltonian systems are effectively used in the control design and the stability analysis. The number of the parameter estimates is significantly lowered as compared to the conventional adaptive control methods which are based on the statespace form. The developed control scheme is applied for attitude control of a spacecraft with both the inertia and the actuator uncertainties, and numerical examples show that the controller successfully deals with the unknown inertia/actuator parameters.

This paper concerns the tracking control of a robot manipulator with unknown uncertainties and disturbances. It presents a new control method that uses only joint position measurements to design a tracking controller. The controller has two parts. One is based on a feedback linearization technique; it makes the nominal model of a manipulator asymptotically track a desired trajectory. The other is based on the idea of equivalent input disturbance (EID); it compensates for uncertainties and disturbances. Together they enable a robot manipulator to precisely track the desired trajectory. The new control algorithm is applied to a two-link robot manipulator, and simulation results demonstrate the validity of this method.