Sinusoidal Injection Research Articles

Analytical and numerical solution of three-dimensional channel flow in presence of a sinusoidal fluid injection and a chemical reaction

Abstract Modeling of three-dimensional channel flow in a chemically-reacting fluid between two long vertical parallel flat plates in the presence of a transverse magnetic field is presented. The stationary plate is subjected to a transverse sinusoidal injection velocity distribution while the uniformly moving plate is subjected to a constant suction and slip boundary conditions. Due to this type of injection velocity, the flow becomes three dimensional. Comparisons with previously published work are performed and the results are found to be in excellent agreement. An increase in the permeability/magnetic parameter is found to escalate the velocity near the plate in motion. Growing Reynolds number or magnetic parameter enhances the x -component and reduces the z -component of the skin-friction at the wall at rest. The acquired knowledge in our study can be used by designers to control MHD flow as suitable for certain applications which include laminar magneto-aerodynamics, materials processing and MHD propulsion thermo-fluid dynamics.

Sensorless Control for Induction Machines Based on Square-Wave Voltage Injection

This paper presents a sensorless control for induction machines, using square-wave voltage injection. Multiple saliencies are considered, as well as saliency orientation shift according to loading conditions. These two nonideal phenomena severely degrade the performance of sensorless controls for induction machines. Multiple saliencies cause the position error signal to become distorted and make estimation of the rotor flux position difficult. Saliency orientation shift causes the estimated rotor flux position to drift from the actual rotor flux position, depending on the torque and speed. In this study, a sensorless algorithm based on square-wave voltage injection is adopted for induction machine control. When square-wave voltage is injected into the estimated synchronous reference frame, the harmonics of the error signal are lower than those of the conventional sinusoidal injection method. In addition, by injecting a square wave into the q-axis of the estimated synchronous reference frame instead of the d-axis, the saliency orientation shift is made smaller. Based on this study using square-wave voltage injection into the q-axis, the flux can be estimated with less error. Because of its enhanced rotor flux estimation performance, the proposed method provides better torque controllability than the conventional sinusoidal voltage injection method. Experimental results confirm the effectiveness of the proposed technique.

Inertia Effects in Rheodynamic Lubrication of an Externally Pressurized Thrust Bearing Using Bingham Lubricant with Sinusoidal Injection

In the present theoretical investigation, the combined effects of fluid inertia forces and sinusoidal injection of the Bingham lubricant, on the performance of an externally pressurized thrust bearing with circular geometry are studied. Using the conventional two-constant Bingham model and by adopting the method of averaging inertia terms, the reduced Navier-Stokes equations are modified and numerical solutions have been obtained for the bearing performances such as the pressure distribution and the load carrying capacity for different values of Bingham number, Reynolds number, time and amplitude. The effects of fluid inertia forces and the non-Newtonian characteristics of the Bingham lubricant on the bearing performances for different sinusoidal conditions are discussed.

Rheodynamic Lubrication of an Externally Pressured Thrust Bearing Using Herschel-Bulkley Fluid with Sinusoidal Injection

Lubricants with variable viscosity are assuming greater importance for its application in polymer industry, thermal reactors and in biomechanics. With the bearing operations in machines being subject to high speeds, loads, increasing mechanical shearing forces and continually increasing pressure, there has been an increasing interest to use nonNewtonian fluids characterized by a yield value. Some of them, which fit into this class, are Bingham, Casson and Herchel-Bulkley models. In the present work, the problem of an externally pressurized thrust bearing lubricated with Herschel-Bulkley fluid under the sinusoidal flow rate has been investigated. Herschel-Bulkley fluids are characterized by a yield value, which leads to the formation of rigid core in the flow region. The shape and extent of the core has been determined numerically for various values of the Herschel-Bulkley number, power-law index, amplitude of sinusoidal fluid film and time. Numerical solutions have been obtained for the bearing performances such as pressure distribution and load capacity for different values of the Herschel-Bulkley number, power-law index, amplitude of sinusoidal fluid film and time. The effects of sinusoidal injection of the lubricant and the non-Newtonian characteristics on the bearing performances have been discussed.

Heat transfer effects in a Couette flow through a composite channel partly filled by a porous medium with a transverse sinusoidal injection velocity and heat source

This study theoretically analyzes the heat transfer effects in a three dimensional Couette flow through a composite parallel porous plate channel partly filled by a porous medium. The flow is three dimensional in the channel because of the application of a transverse sinusoidal injection velocity of a particular form at the lower stationary plate. The governing equations are solved using a perturbation series expansion method. The effects of various flow parameters such as, Prandtl number (Pr), suction/injection parameter (?), permeability of the porous medium (K), heat source parameter (S), and viscosity ratio parameter (?1), are investigated on temperature distribution in the composite channel and rate of heat transfer at the upper moving plate and at the fluid-porous medium interface, and discussed graphically.

Rotational and Quasiviscous Cold Flow Models for Axisymmetric Hybrid Propellant Chambers

In this work, we present two simple mean flow solutions that mimic the bulk gas motion inside a full-length, cylindrical hybrid rocket engine. Two distinct methods are used. The first is based on steady, axisymmetric, rotational, and incompressible flow conditions. It leads to an Eulerian solution that observes the normal sidewall mass injection condition while assuming a sinusoidal injection profile at the head end wall. The second approach constitutes a slight improvement over the first in its inclusion of viscous effects. At the outset, a first order viscous approximation is constructed using regular perturbations in the reciprocal of the wall injection Reynolds number. The asymptotic approximation is derived from a general similarity reduced Navier–Stokes equation for a viscous tube with regressing porous walls. It is then compared and shown to agree remarkably well with two existing solutions. The resulting formulations enable us to model the streamtubes observed in conventional hybrid engines in which the parallel motion of gaseous oxidizer is coupled with the cross-streamwise (i.e., sidewall) addition of solid fuel. Furthermore, estimates for pressure, velocity, and vorticity distributions in the simulated engine are provided in closed form. Our idealized hybrid engine is modeled as a porous circular-port chamber with head end injection. The mathematical treatment is based on a standard similarity approach that is tailored to permit sinusoidal injection at the head end.

Effect of constant suction and injection on MHD three dimensional couette flow and heat transfer through a porous medium

The objective of this paper is to analyzethe effect of constant suction and sinusoidal injection on three dimensional couette flow of a viscous incompressible electrically conducting fluid through a porous medium between two infinite horizontal parallel porous flat plates in presence of a transverse magnetic field. The stationary plate and the plate in uniform motion are, respectively, subjected to a transverse sinusoidal injection and uniform suction of the fluid .The flow becomes three dimensional due to this type of injection velocity distribution. The governing equations of the flow field are solved by using series expansion method and the expressions for the velocity field, the temperature field, skin friction and the rate of heat transfer in terms of Nusselt number are obtained. The effects of the flow parameters on the velocity field, temperature field, skin friction and the Nusselt number have been studied and analyzed with the help of figures and tables. It is observed that a growing magnetic parameter (M) retards the main velocity (u) and accelerates the cross flow velocity (w1) of the flow field and a growing permeability parameter (Kp) or suction / injection parameter (Re) reverses the effect. Both Prandtl number (Pr) and the suction / injection parameter have retarding effect on the temperature field. Further, a growing suction / injection parameter diminishes both the components of skin friction at the wall while the permeability parameter enhances the x-component and reduces the z-component of the skin friction at the wall. The effect of increasing permeability parameter is to enhance the magnitude of rate of heat transfer at the wall while a growing Prandtl number (Pr) reverses the effect.Keywords: MHD; couette flow; heat transfer; suction; sinusoidal injection; porous mediumDOI: 10.3329/jname.v5i2.2570Journal of Naval Architecture and Marine Engineering 6(1)(2009) 41-51

Flow Induced in a Porous Medium due to a three dimensional couette flow Adjacent to it

The flow of a viscous fluid induced in a porous medium due to a uniform motion of a plate parallel to its surface has been discussed when there is a transverse sinusoidal injection of the fluid at the moving plate. The fluid fills the space between the plate and the porous medium which is fully saturated with the fluid. Due to this type of the injection velocity the flow in the clear fluid becomes three dimensional. It is assumed that the flow in the clear fluid region governed by Navier-Stokes equation and that in the porous medium by the Brinkman equation near the interface and by Darcy law far away from interface. It is found that with increase of the permeability of the porous medium the magnitude of the velocity component increase in both regions. In the porous region the velocity component parallel to motion of the plate is maximum at the interface and then decreases exponentially forming a boundary layer at the interface. Also the velocity component parallel to the motion of the plate decreases with the increase of injection Reynolds number Re and the magnitude of other velocity components increases with the increase of Re.

3D couette flow of dusty fluid with transpiration cooling

The couette dusty flow between two horizontal parallel porous flat plates with transverse sinusoidal injection of the dusty fluid at the stationary plate and its corresponding removal by constant suction through the plate in uniform motion was analyzed. Due to this type of injection velocity the dusty flow becomes 3D. Perturbation method is used to obtain the expressions for the velocity and temperature fields of both the fluid and dust. It was found that the velocity profiles of both the fluid and dust in the main flow direction decrease with the increase of the mass concentration of the dust particles, and those in cross flow direction increase with an increase in the mass concentration of the dust particles up to the middle of the channel and thereafter decrease with increase in mass concentration of the dust particles. The skin friction components T x and T z in the main flow and transverse directions respectively increase with an increase in the mass concentration of the dust particles (or) injection parameter. The heat transfer coefficient decreases with the increase of the injection parameter and increases with the increase in the mass concentration of the dust particles.

Three dimensional free convection couette flow with transpiration cooling

Free convection flow between two vertical parallel plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by constant suction through the plate in uniform motion has been analyzed. Due to this type of injection velocity, the flow becomes three-dimensional. Analytical expressions for the velocity, temperature, skin friction and rate of heat transfer were obtained. The important characteristics of the problem, namely the skin friction and the rate of heat transfer are discussed in detail with the help of graphs.

Magnetohydrodynamics effect on three‐dimensional viscous incompressible flowbetween two horizontal parallel porous plates and heat transfer withperiodic injection/suction

We investigate the hydromagnetic effect on viscous incompressible flow between two horizontal parallel porous flat plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by periodic suction through the plate in uniform motion. The flow becomes three dimensional due to this injection/suction velocity. Approximate solutions are obtained for the flow field, the pressure, the skin‐friction, the temperature field, and the rate of heat transfer. The dependence of solution on M (Hartmann number) and λ (injection/suction) is investigated by the graphs and tables.

MHD Three-Dimensional Couette Flow with Transpiration Cooling

An analysis of the Couette flow between two horizontal parallel porous flat plates of an electrically conducting, viscous, incompressible fluid is presented. The stationary plate is subjected to a transverse sinusoidal injection of the fluid and its corresponding removal by constant suction through the other plate in uniform motion. The flow becomes three-dimensional due to such an injection velocity. A magnetic field of uniform strength is also applied normal to the planes of the plates. The effects of the injection/suction velocity and the magnetic field on the flow field, skin friction, and heat transfer are reported.

Forcing pulsatile behaviour in semiconductor lasers by periodic control

Abstract In this paper, we apply optimal control theory for the operation of a standard edge-emitter semiconductor laser so as to produce good quality pulsing output signals. This is achieved by using a sinusoidal injection current whose characteristics (frequency and amplitude) are suitably tuned. The performances obtained from this optimal control strategy are compared with those achievable with a novel self-pulsing device recently designed.

Three dimensional Couette flow with transpiration cooling

The Couette flow between two horizontal parallel porous flat plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by constant suction through the plate in uniform motion has been analyzed. Due to this type of injection velocity the flow becomes three-dimensional. The series expansion method is used to obtain the expressions for the velocity and temperature fields. It is found that the heat transfer coefficient decreases with the increase of the injection parameter \(\lambda\).

Automatic simultaneous determination of Ca and Mg in natural waters with no interference separation

In this study a methodology is reported for the automatic, simultaneous determination of Ca and Mg in natural waters which is not affected by the presence of species that may interfere with other methods. A flow system based on the sinusoidal injection analysis (SIA) methodology with diode array spectrophotometric detection of the complex formed by both analytes with the Arsenazo III has been used. The technique of multivariate calibration used, PLS1, enables Ca to be determined in the concentration range 45–85 mg l −1 and Mg to be determined in the range 2–70 mg l −1, with no need for the samples to be previously diluted. The accuracy of the method has been tested by comparing the results obtained with the standard atomic absorption spectrometry method. With an analysis speed of 20–30 samples per hour, the RMSE in terms of standard deviation of the original variables was 6.1 for Mg and 6.4 for Ca.

Experimental and numerical study of transient laminar counterflow diffusion flames

In the present article, we analyze the nonsteady behavior of counterflow diffusion flames subjected to a time-dependent injection velocity in the case of hydrogen—air flames. The numerical study, using a finite-difference implicit linear multistep method and employing complex kinetics, is done for sinusoidal injection velocity variations, for moderate values and also for values near the extinction limit. The frequency response is obtained in these different cases. The experimental setup comprises two axisymmetric nozzles. In order to change the inlet velocities periodically, we use a vibrating mechanism in each burner. The amplitude and the frequency of injection velocities of the opposed nozzles are synchronously modified. The OH radical emission intensity is used to measure the flame response to velocity fluctuations. The experimental results are compared to numerical calculations. Good agreement is obtained in this comparison.

Walsh function current patterns and data synthesis for electrical impedance tomography

A data collection method which uses Walsh functions as injection current patterns is presented. This method can satisfy two conditions: the optimality of current patterns in every iteration and the single-time data measurement condition. The use of Walsh functions simplifies the design of current sources since only two levels of current (+1 and -1) are required, whereas sinusoidal injection requires a digital-to-analog converter to produce many different values of currents. Compared to diagonal or neighboring type of pulses as injection current patterns, Walsh injection current patterns provide more information about the interior of the subject since Walsh function simulate low and high spatial frequency patterns. Therefore, Walsh function injection uses the simplicity of pulse type injection and yields the better distinguishability or SNR of sinusoidal injection.

A model of a diode laser actively mode-locked by gain modulation

A rate-equation analysis of a diode laser in an external resonator which is actively mode-locked by periodic modulation of the injection current is presented. A computer simulation of the transient process of pulse generation is developed. The coupled rate equations for electron and photon densities as functions of time and position within the diode are solved numerically. The effects of sinusoidal and pulsed injection current, spatial and temporal gain saturation, various resonator configurations, mismatch between modulation frequency and round-trip frequency, and varying laser parameter values are considered. A comparison of results with those of previous theories is presented. Optimum conditions for mode-locking are stated.

Generation of single-longitudinal-mode gigabit-rate optical pulses from semiconductor lasers through harmonic-frequency sinusoidal modulation

Generation of optical pulses at gigabit rates from semiconductor lasers by means of harmonic-frequency sinusoidal injection current modulation has been demonstrated for the first time. It was confirmed that these optical pulses consisted of one longitudinal oscillating mode because of the presence of a ‘self-optical injection-locking effect’.

Response of semiconductor laser to deep sinusoidal injection current modulation

Laser diode response to deep sinusoidal injection current modulation is investigated both theoretically and experimentally. By the numerical analysis of multilongitudinal rate equations with a modulation term, regular pulsation regions and the spectral broadening and wavelength shift of the optical pulse are given. These theoretical results are well supported by experimental observations with an AlGaAs laser diode, where a 40-70 ps optical pulse at a repetition rate of 200 MHz to 2.17 GHz was obtained. The possibility of generating a coherent optical pulse by harmonic frequency injection current modulation of laser diodes without external cavities is pointed out theoretically. Further, coherent pulsations by external light injection in sinusoidally modulated laser diodes are investigated both theoretically and experimentally.