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This research paper presents a comprehensive study on the intricate interplay of rotational, magnetic field and heat transfer effects in squeezing fluid flow, utilizing the foundational framework of Navier–Stokes equations. Fluid flow in confined geometries has significant applications in various industrial processes, including lubrication systems, microfluidics, and heat exchangers. The integration of rotational motion, magnetic fields, and heat transfer phenomena into this context holds immense potential for optimizing performance and efficiency. The study commences with the derivation and analysis of the coupled Navier–Stokes equations, incorporating the Coriolis force due to rotational motion, the Lorentz force arising from magnetic fields, and the energy equation for heat transfer. This comprehensive model accounts for the complex interactions between these physical phenomena, offering a holistic perspective on squeezing fluid flow dynamics. Numerical analysis are conducted to investigate the behavior of fluids under the influence of rotational, magnetic field, and heat transfer effects. The results reveal intricate flow patterns, including vortex formation and heat transfer enhancement. Furthermore, the impact of key parameters such as rotational speed, magnetic field strength, and temperature gradients on flow characteristics is systematically analyzed. The Dufour effect pertains to the transfer of energy resulting from a gradient in mass concentration, occurring as a correlated consequence of irreversible processes. It functions as the inverse of the Soret effect. The temperature changes due to the concentration gradient, amplifying as the Dufour number increases. The most significant temperature rise is observed at the midpoint of the fluid domain. Conversely, the Soret number behaves in a similar but opposite manner. Tables 4–10 has been created to offer a comprehensive analysis of the optimal alignment between Homotopy Analysis Method (HAM) and BVP4c. Specifically, it demonstrates a continuous decrease in skin friction for ξ S o , ξ R d , and ξ R 2 , while showing an increase for ξ S c , ξ D o , and ξ R e m . Meanwhile, the skin friction remains constant for ξ P r . The research centers on analyzing heat and mass transfer properties within an incompressible fluid confined between two rotating and stretching disks amidst an unpredictable flow pattern. The study employs a blend of analytical and numerical approaches to solve the governing equations, delving into the intricate fluid dynamics and the intricate processes of heat and mass transfer within this intricate system. [ABSTRACT FROM AUTHOR]

The demand of energy saving and loss mitigation in modern industry gives rise to drag reduction techniques such as micro groove/riblet ever since the last century. Plenty of studies are conducted under straight flow condition showing relevance between drag reduction and flow features. However, the same issue has not been studied adequately for rotational flows, which is typical in turbopumps. In this paper, two-dimensional numerical simulations of rotating disks are performed together with verification experiments to investigate drag reduction effect of micro riblet under rotational flow condition. The numerical results show that riblets with certain dimensions can lessen the resistant torque by a maximum of 8.46% and the drag reduction efficiency depends on rotational Reynolds number and riblet dimensions. Meanwhile, the distributions of static pressure and swirl velocity on surfaces are changed and near-wall turbulence intensity is tranquilized by riblets which are considered as the main reasons to the diminish of drag. Finally, the relevance of vortexes inside riblets to swirl wall shear stress and torque is demonstrated revealing that the configuration of riblets plays an important role in cutting resistance. The results of this paper can be a supplement for the investigation of micro groove/riblet drag reduction mechanism. [ABSTRACT FROM AUTHOR]

A comprehensive experimental investigation of water cold plate with different flow configurations for electronic cooling was conducted. Serpentine, parallel and wavy channels cold plate were designed to study the hydrothermal performance of water cold plate for electronic servers cooling. Thermal resistance, pressure drop, Nusselt number, servers' temperatures and performance evaluation criterion were measured, evaluated and compared to evaluate the hydrothermal performance of the different configurations. The results showed that the serpentine channels cold plate has a better thermal performance than both parallel and wavy channels cold plate. The serpentine channels cold plate yields a lower thermal resistance by (6.02–10.5%), (2.4–8.7%) and a higher average Nusselt number by (7.9–13.9%), (6.3–13.7%) compared to parallel and wavy channels cold plate, respectively. Also, the results indicated that the serpentine channels cold plate has a higher pressure drop and pumping power compared to parallel and wavy channels cold plates. Similarly, the results showed that the wavy channel has better thermal performance than parallel channels due to the larger flow path and the rotational flow occurred. The I-Type inlet and outlet configuration used in the wavy channel cold plate provide a lower pressure drop compared to parallel channels however the large flow path. The performance evaluation criterion showed that the wavy channels cold plate has a higher performance evaluation criterion than serpentine channels due to its lower pressure drop. [ABSTRACT FROM AUTHOR]

The blade unit of the tridimensional rotational flow sieve tray (TRST) makes the fluid form a rotational–perforated flow. The analysis of the flow properties of the unit is helpful to understand the hydrodynamic characteristics of TRST. The gas–liquid concurrent flow field was studied using the multi-fluid VOF method. The rotational and perforated flows at each section were analyzed based on the section rotational flow ratios. The section rotational flow ratio for the gas phase was between 0.6 and 0.85, and the transition section of the rotational and perforated flows of the liquid phase was z = 30 mm. The relationships between TRST and blade unit were clarified. The simulation performed for analyzing the mass transfer and structural optimization of the blade unit and TRST. • The rotational and perforated flows are separated by the simulation. • The variation for rotational–perforated flow at each section for gas–liquid phase is studied. • The simulation clarified the transition point of rotational-perforated flow on the blade unit. • The relationships between the blade unit and TRST are analyzed. [ABSTRACT FROM AUTHOR]

A novel design of cooling air supply system with dual row pre-swirl nozzles (DRPM) is promoted and investigated. Simplified theoretical analysis and numerical simulation are used to estimate the total temperature reduction and mass flow rate characteristic of DRPM and compared with single row pre-swirl nozzle model (SRPM). The results show that, both models have similar flow structure and the variation of total temperature reduction and dimensionless mass flow rate with rotational Reynolds number and pressure ratio is also similar. Which have an inflection point with the increase of rotational Reynolds number but increases monotonically with the variation of pressure ratio. The pre-swirl system has the maximum flow rate and temperature reduction when the inflow Angle equal to 0 or the swirl ratio equal to 1 at the inlet of the receiver hole. The increase in pressure ratio improves the total temperature reduction and dimensionless mass flow rate as well. In the range of rotational Reynolds number calculated, DRPM can increase the dimensionless mass flow rate by 3.0% but the total temperature reduction decreased by 37.8% in average compared with SRPM. On the other hand, the dimensionless mass flow rate increased by 2.8% and total temperature reduction decreased by 14.9% in average in the range of pressure ratio calculated. Numerical results are in good agreement with the results calculated by simplified theoretical formulas. [ABSTRACT FROM AUTHOR]

A novel design of cooling air supply system with dual row pre-swirl nozzles (DRPM) is promoted and investigated. Simplified theoretical analysis and numerical simulation are used to estimate the total temperature reduction and mass flow rate characteristic of DRPM and compared with single row pre-swirl nozzle model (SRPM). The results show that, both models have similar flow structure and the variation of total temperature reduction and dimensionless mass flow rate with rotational Reynolds number and pressure ratio is also similar. Which have an inflection point with the increase of rotational Reynolds number but increases monotonically with the variation of pressure ratio. The pre-swirl system has the maximum flow rate and temperature reduction when the inflow Angle equal to 0 or the swirl ratio equal to 1 at the inlet of the receiver hole. The increase in pressure ratio improves the total temperature reduction and dimensionless mass flow rate as well. In the range of rotational Reynolds number calculated, DRPM can increase the dimensionless mass flow rate by 3.0% but the total temperature reduction decreased by 37.8% in average compared with SRPM. On the other hand, the dimensionless mass flow rate increased by 2.8% and total temperature reduction decreased by 14.9% in average in the range of pressure ratio calculated. Numerical results are in good agreement with the results calculated by simplified theoretical formulas. [ABSTRACT FROM AUTHOR]

In this paper, a numerical study of a swirling flame generated through the interaction between a central fire and its surrounding fires is performed. A swirling flame can be configured by installing a secondary's sources surrounding the central source, organized in an asymmetrical manner in order to ensure circumferential entrainment of the central flame by the supply puffs air. An analysis is performed to study this kind of flow. This analysis highlights the different zones that characterize the vertical propagation of a swirling flame; a first zone, close to the fire source, characterized by an acceleration of the flow and an increase of the temperature. A second zone marked by the passage of the temperature by a maximum while changing variation with a net decrease of the flow acceleration and a third zone where the thermal and dynamic fields change and gradually decrease. Moreover, this study shows an axisymmetric flow behavior with two different aspects of its global structure. A central region characterized by a block motion (solid core) where the flow is rotational, characterized by a concentration of vorticity, and surrounded by the rest of the space where the flow is irrotational. Moving vertically away from the active source, results show an attenuation of the axial vortex intensity which is accompanied by a disappearance of movement by block. The centerline evolution of the axial and azimuthal momentum flux enables also to highlight these different aspects of the global flow structure. [ABSTRACT FROM AUTHOR]

An experimental vortex pump with a specific speed of 76 is investigated to get its performance and flow structure under noncavitation and cavitation conditions when the pump operates as turbine in the reverse direction by using computational fluid dynamics (CFD) method. A method is proposed to extract hydraulic, volumetric, and mechanical efficiencies for the first time. It is shown that a vortex pump can operate as turbine but it is subject to poor cavitation performance. The performance conversion factors of flow rate and head are 2.33 and 2.74 which are much larger than existing centrifugal pumps as turbine with the same specific speed. The conversion factor of efficiency is 0.98, which agrees with the conversion factor of efficiency for a centrifugal pump as turbine. There are a rope cavity and a vortex flow in the same rotational direction of the impeller. It is shown that flow structure is complex in the impeller in pump and turbine modes, particularly on the blade-to-blade surface, while static pressure profile in the volute and impeller as well as the space between the casing and the impeller is simple. The flow in the space between the impeller and the casing cannot be regarded as a forced vortex in both modes. The cavitation performance improvement and rope cavity control may be key issues in the future. [ABSTRACT FROM AUTHOR]

We present a method for three-dimensional (3D) localization and tracking of multiple targets by using images from multiple cameras with overlapping views. Most recent methods make an assumption on a flat ground plane and determine the 3D grounding location of each target based on this assumption. In contrast, we aim to find 3D locations of multiple head trajectories, regardless of their standing or sitting status without the flat ground plane assumption. For this purpose, we suggest a unified optimization formulation, which solves two coupled problems simultaneously: the spatio-temporal data association problem and the 3D trajectory estimation problem. To handle a large solution space, we develop an efficient optimization scheme that alternates the solving procedures between two coupled problems with a reasonable computational load. In the unified optimization formulation, we design a new cost function that describes 3D physical properties of each target. The experiments illustrate that the proposed method outperforms the state-of-the-art methods in 3D localization and tracking performance. [ABSTRACT FROM AUTHOR]

In this paper, we present a new algebraic method to solve the perspective-three-point (P3P) problem, which directly computes the rotation and position of a camera in the world frame without the intermediate derivation of the points in the camera frame. Unlike other online methods, the proposed method uses an “object” coordinate frame, in which the known 3D coordinates are sparse, facilitating formulations of the P3P problem. Additionally, two auxiliary variables are introduced to parameterize the rotation and position matrix, and then a closed-form solution for the camera pose is obtained from subsequent substitutions. This algebraic approach makes the processes more easily followed and significantly improves the performance. Experimental results demonstrated that our method offers accuracy and precision comparable to the existing state-of-the art methods but it has better computational efficiency. [ABSTRACT FROM AUTHOR]

• Investigation of the effects of acoustically flow on PCM characteristics for the first time were investigated. • Uniform inlet flow and the square profile decreases the amount of natural convection in the PCM unit. • With the sine profile, it takes about 50% less time for the PCM unit's average temperature to reach its highest level. Acoustic flows are the rotational flows that are generated near solid surfaces and vibrating components, as well as near boundary walls in a high-intensity sound field. By making the flow oscillate, this type of flow can be a good way to improve HT. Besides, phase change materials provide high cooling in a short time because they absorb the latent heat of their melting during melting. The use of the phase change material and adding some pulsing function of inlet flow have been considered to investigate the battery's performance. To this end, the finite volume method, along with interface mesh and grid adaptation techniques, has been used to achieve more accurate results. The comparisons of the obtained results were made to the existing data, and after ensuring the numerical methodology, four functions were used to investigate the effects of variations in inlet velocity. The results showed that different kinds of pulsation flows have different qualities and ways to improve HT in different situations. For instance, the sine profile helps the average temperature of the PCM unit reach the maximum value in approximately 50 percent less time. [ABSTRACT FROM AUTHOR]

Most of the shaft theories have based their analysis on bending moment, twisting moment or combined between them. Nevertheless, the dynamic behavior of flexural-torsional coupled vibrations in the rotating shafts is affected by the internal resistance forces due to torsion. It is expected that the deflected shafts shall be exposed to this resistance, where these forces were not considered in the analysis before. The objective of the present work was to estimate the effect of internal torsional resistance in shafts which is caused by deflection, for the reason that it has the upper hand on misalignment problem. With the aim of fulfilling this objective, an experimental rig has been constructed to verify the existence of the torsional resistance in deflected shafts and its variation with the rotation angle. [ABSTRACT FROM AUTHOR]

An open-hole extended-reach limit model was established and published by the authors to determine how far a horizontal extended-reach well (ERW) can extend. The published model shows that the open-hole extended-reach limit (the maximum measured depth of the horizontal ERW) is mainly dependent on the annular pressure drop and the fracture pressure of drilled formation. Moreover, some optimal control methods, such as lowering drilling fluid density, reducing drilling fluid flow rate and optimizing drill pipe eccentricity, were also presented to obtain greater open-hole extended-reach limit. However, the published model was established based on the assumption that the annular fluid is ideal single-phase flow. Failing to consider the effects of cuttings may lead to an inaccurate prediction of the open-hole extended-reach limit and even drilling safety hazards. In this paper, in order to overcome the shortcomings of the published model, a prediction model of the open-hole extended-reach limit in horizontal drilling considering the effects of cuttings is established and analyzed. The study shows that due to an increase of annular pressure drop, the horizontal-section limit (the maximum measured depth of horizontal-section for the horizontal ERW) is relatively smaller when considering the effects of cuttings. Meanwhile, a case study is carried out, and the results show that the horizontal-section limit is 1610 m when the cuttings are considered. In contrast, when the cuttings are ignored, the limit is 1941 m based on the published model. Furthermore, since several main parameters of the established model may greatly affect the annular pressure drop and the horizontal-section limit, parameters sensitivity analysis are also performed and some conclusions are drawn. First, the horizontal-section limit first increases and subsequently decreases with the increase in drilling fluid density. Second, there is an increase in horizontal-section limit when the drilling fluid flow rate increases. Third, the horizontal-section limit gradually increases with the increase in the drill string rotation speed. Finally, there is also a decrease in the horizontal-section limit when the rate of penetration (ROP) and the consistency coefficient increase. In sum, the simulated condition in this paper is more consistent with the situation of field drilling practice than that of the published model. This study will also provide a more accurate result of the open-hole extended-reach limit, which is of great significance to the drilling design and drilling safety. [ABSTRACT FROM AUTHOR]

In this paper, blade tip cooling is investigated with coolant injection from the shroud alone and a combination of shroud coolant injection and tip cooling. With a nominal rotation speed of 1200 rpm, each blade consists of a cut back squealer tip with a tip clearance of 1.7% of the blade span. The blades also consist of tip holes and pressure side (PS) shaped holes, while the shroud has an array of angled holes and a circumferential slot upstream of the rotor section. Different combinations of the three cooling configurations (tip and PS holes, shroud angled holes, and shroud circumferential slot) are utilized to study the effectiveness of coolant injected from the shroud as a complementary method of cooling the blade tip. The measurements are done using liquid crystal thermography. Blowing ratios of 0.5, 1.0, 2.0, 3.0, and 4.0 are studied for shroud slot cooling, and blowing ratios of 1.0, 2.0, 3.0, 4.0, and 5.0 are studied for shroud hole cooling. For cases with coolant injection from the blade tip, the blowing ratios used are 1.0, 2.0, 3.0, and 4.0. The results show an increase in film cooling effectiveness with increasing blowing ratio for shroud hole coolant injection. The increased effectiveness from shroud hole coolant is concentrated mainly in the tip region below the shroud holes and toward the blade suction side and the suction side squealer rim. Slot coolant injection results in increased effectiveness on the blade tip near the blade leading edge up to a maximum blowing ratio, after which the cooling effectiveness decreases with increasing blowing ratio. The combination of the different cooling methods results in better overall cooling coverage of the blade tip with the shroud hole and blade tip coolant combination being the most effective. The level of coolant protection is strongly dependent on the blowing ratio and combination of blowing ratios. [ABSTRACT FROM AUTHOR]

An experimental study of film cooling is conducted on the tip of a turbine blade with a blade rotation speed of 1200 rpm. The coolant is injected from the blade tip and pressure side (PS) holes, and the effect of the blowing ratio on the heat transfer coefficient and film cooling effectiveness of the blade tip is investigated. The blade has a tip clearance of 1.7% of the blade span and consists of a cut back squealer rim, two cylindrical tip holes, and six shaped PS holes. The stator-rotor-stator test section is housed in a closed loop wind tunnel that allows for the performance of transient heat transfer tests. Measurements of the heat transfer coefficient and film cooling effectiveness are done on the blade tip using liquid crystal thermography. These measurements are reported for the no coolant case and for blowing ratios of 1.0, 1.5, 2.0, 3.0, and 4.0. The heat transfer result for the no coolant injection shows a region of high heat transfer on the blade tip near the blade leading edge region as the incident flow impinges on that region. This region of high heat transfer extends and stretches on the tip as more coolant is introduced through the tip holes at higher blowing ratios. The cooling results show that increasing the blowing ratio increases the film cooling effectiveness. The cooling effectiveness signatures indicate that the tip coolant is pushed toward the blade suction side thereby providing better coverage in that region. This shift in coolant flow toward the blade suction side, as opposed to the PS in stationary studies, can primarily be attributed to the effects of the blade relative motion. [ABSTRACT FROM AUTHOR]

A new model for calculation of the velocity field in a pump meridian is presented in this paper. It is a parameterized rotational flow model providing the pump designer with an option to simulate various flow conditions at the blade leading edge using a single parameter, which leads to different blade designs. Despite being rotational, this flow model does not allow for creation of helical swirl structures, a feature that is usually sought to be suppressed in a pump impeller. A condition for a flow pattern suitable for a pump hydraulic design is derived using curvilinear coordinates. The variation of the meridional velocity for different choices of the parameter is demonstrated, and the meridional flow field is compared against the turbulent flow. The resulting velocity field is easy to obtain and provides a unified approach to determine the distribution of the blade inlet angles along the leading edge for a range of design requirements. [ABSTRACT FROM AUTHOR]

Experimental data are presented for large arrays of rotating, finite-height cylinders to study the dependence of the three-dimensional (3D) mean flows on the geometric and rotational configurations of the array. Two geometric configurations, each with two rotational configurations, were examined at a nominal Reynolds number of 600 and nominal tip-speed ratios of 0, 2, and 4. It was found that the rotation of the cylinders drives the formation of streamwise and transverse flow patterns between cylinders and that net time-space averaged transverse and vertical flows exist within the developed flow region of the array. This net vertical mean flow provides an additional mechanism for the exchange of momentum between the flow within the array and the flow above it, independent from the turbulent exchange mechanisms which are also observed to increase by almost a factor of three in a rotating array. As an array of rotating cylinders may provide insight into the flow kinematics of an array of vertical axis wind turbines (VAWTs), this planform momentum flux (both mean and turbulent) is of particular interest, as it has the potential to increase the energy resource available to turbines far downstream of the leading edge of the array. In the present study, the streamwise momentum flux into the array could be increased for the rotating-element arrays by up to a factor of 5.7 compared to the stationary-element arrays, while the streamwise flow frontally averaged over the elements could be increased by up to a factor of four in the rotating-element arrays compared to stationary-element arrays. [ABSTRACT FROM AUTHOR]

The oil-and-gas industry has become increasingly interested in drilling dynamics and vibration as causes of drilling inefficiency and reduced drilling performance. Generally, drillstring vibration is measured with shock-and-vibration sensors installed in measurement- while-drilling (MWD) tools, logging-while-drilling (LWD) tools, and rotary steerable systems (RSS). Although these tools provide valuable real-time and recorded-mode information on the dynamic conditions, they are not generally designed to capture continuous high-frequency (HF) mechanics and dynamics data, and burst data may miss important information about the evolution of the system response and state. A downhole mechanics measurement tool has been developed that makes a comprehensive suite of measurements of the drilling process, including forces, accelerations, rotational speed, pressures, and temperatures. In addition to providing information in real time, the tool has the capability to capture long durations of continuous data at frequencies between 50 and 2,000 Hz. The recorded-mode information obtained has provided significant insight into the response of the drilling system to starting rotation; drilling procedures and parameter modifications; and exposure to excitation from sources including, but not limited to, rig heave, bottomhole-assembly (BHA) component imbalance, and bit/rock interaction. A wide range of occurrences has been captured in which the drilling system switches from a dominant vibration mode, typically torsional (downhole rotation-velocity oscillations or stick/slip) into a different mode, such as axial (bit bounce) or lateral (whirl). Transitions between different types of whirl have also been recorded. Several cases were studied to investigate the evolution and response of drilling-system behavior on the basis of in-depth interpretation of relatively long durations (minutes to hours) of HF data sets in the operational context. The findings verify the value of using continuous HF vibration data to understand the drilling system and to increase drilling performance. [ABSTRACT FROM AUTHOR]

Recently, there has been a strong push toward automation and the use of real-time models in the drilling industry. However, it has been recognized that these new methods require a dramatic improvement in the quality of sensor data gathered at the rig. In this paper, we investigate how accurate measurement of drillpipe torque and tension at the surface can be used to diagnose downhole conditions. A surface-based torque-and-tension sub (TTS) was used to perform measurements while drilling several horizontal wells in the Dilly Creek area of the Horn River Basin, which is onshore in Canada. A filtered version of surface torque was used to calculate a stick/slip metric, which was compared to stick/slip measurements acquired with a downhole tool. The results show that there is reasonable correlation between surface and downhole metrics, but the correlation is highly dependent on torque filter start and stop frequencies. A comparison is also performed between the hookload measured with a deadline sensor and the tension measurement from the surface sub. The results show a systematic discrepancy of approximately 5% that is likely caused by sheave friction. A commercial torque-and-drag (T&D) software package is used to show that values for casing friction factor (FF) may be underestimated if sheave friction is present but ignored in the analysis. The results from this study show that an advanced measurement sub placed below the topdrive can provide valuable information regarding drilling performance. Specifically, the torque signal can be used to estimate the level of downhole stick/slip, which alleviates the need for an expensive downhole-dynamics tool. Also, the tension signal can be used to obtain accurate measurements of wellbore FF, which can be compared with theoretical values obtained with T&D analysis. With an appropriate-software implementation, these measurements can be performed in real time, which would enable rig crews to react quickly whenever excessive stick/slip or wellbore drag is encountered during drilling operations. [ABSTRACT FROM AUTHOR]

The micromixing efficiency of a rotating packed bed (RPB) with blade packings, which is determined by a parallel competing reaction system, is related to the rotational speed, the total liquid flow rate, the outer radius of the blade, the inner radius of the blade, the number of blades, and the liquid viscosity. Experimental results show that increasing the rotational speed, the total liquid flow rate, and the number of blades effectively increased the micromixing efficiency. Increasing the outer radius of the blade and the liquid viscosity did not almost affect micromixing efficiency. The inner radius of the blade had a particular effect on micromixing efficiency: the micromixing efficiency firstly decreased and then increased as the inner radius of the blade was increased. Although the micromixing efficiency in the RPB with blade packings was lower than that in the RPB with structured packings, the mean size of the magnesium hydroxide nanoparticles that were prepared using the RPB with blade packings was close to that of those prepared using the RPB with structured packings. Accordingly, the RPB with blade packings is a promising reactor for preparing nanoparticles with high micromixing efficiency. [ABSTRACT FROM AUTHOR]

Unsteady Taylor–Couette flows of an Oldroyd-B fluid, which fills a straight circular cylinder of radius R , are studied. Flows are generated by the oscillating azimuthal tension which is given on the cylinder surface. As a novelty, authors used in this paper the governing equation related to the tension field. The closed forms of the shear stress and velocity fields corresponding to the flow problems are obtained by means of the integral transforms method. Expressions for the azimuthal tension and fluid velocity were written as sums between the “permanent component” (the steady-state component) and the transient component. By customizing values of parameters from the mathematical model were obtained the corresponding solutions of other types of fluids, namely, Maxwell fluids. By using numerical simulations and diagrams of the azimuthal stress, the fluid behavior has been analyzed. The necessary time to achieve the “steady-state” was, also, determined. [ABSTRACT FROM AUTHOR]

The aerodynamic flow conditions on wings and tail surfaces due to the rotational motion of a spinning aeroplane have been investigated in a full-scale spin flight research programme at the Brunei Flight Safety Laboratory. The wing upper surface vortex has been visualised using smoke and tufts on the wing of a Slingsby Firefly. The flow structures on top of both wings, and on top of the horizontal tail surfaces, have also been studied on a Saab Safir. The development of these rotational flow effects has been related to the spin motion and the effect on the spin dynamics has been studied and discussed. Evidence suggests that the turbulent wake from the wing upper surface vortex impinges the tail of the aircraft during the spin entry. It is hypothesised that the turbulent flow structure on the outside upper wing surface is due to additional accelerations induced by the rotational motion of the aeroplane. Furthermore, the lightening in stick force during spin entry and the apparent increase in push force required for spin recovery corresponds to the observed change in flow condition on the horizontal tail. The difference in pressure on the upper and lower horizontal tail surfaces have been measured using differential pressure sensors, and the result corresponds both with the observed flow conditions and earlier research results from NASA. [ABSTRACT FROM AUTHOR]

The vehicle-induced aerodynamic loads bring vibrations to some of the highway sound barriers, for they are designed in consideration of natural wind loads only. A field experiment is carried out with respect to three important factors: vehicle type, vehicle speed and the vehicle-barrier separation distance. Based on the results, the time-history of pressures is given, showing identical characteristics in all cases. Therefore, the vehicle-induced aerodynamic loads acting on the highway sound barrier are summarized as the combination of "head impact" and "wake impact". The head impact appears to have potential features, while the wake impact is influenced by the rotational flow. Then parameters in the experiment are analyzed, showing that the head impact varies with vehicle speed, vehicle-barrier separation distance, vehicle shape and cross-sectional area, while the wake impact is mainly about vehicle-barrier separation distance and vehicle length. [ABSTRACT FROM AUTHOR]

This is the second part of the paper for modeling and validation of the rotational vibra-tion responses for an accessory drive system. The unified formulas for modeling the rota-tional vibration of an accessory drive system are presented. In the modeling of an accessory drive system, the damping and stiffness of a belt are regarded as the function of the excitation frequency of an engine and the amplitude of belt stretching. Additionally, the creeping effect of a belt on the pulley wrap arc is included in the model. A general purpose software for calculating the rotational vibration of an accessory drive system is developed, based on the presented unified formulas. One accessory drive system with seven pulleys, a tensioner, and a serpentine belt is used as a studying example to demon-strate the unified formulas and the procedure for obtaining the rotational vibration. In the simulation of the accessory drive system, the stiffness and damping of the belt, the friction coefficient between the belt and pulley, and the excitation torques with multifre-quency components from the crankshaft torsional vibration are obtained from the experi-ment in the first part of this paper. The static tension and steady-state tension of each belt span, along with the natural frequency of the accessory drive system, rotational vibra-tions of the driven pulley and tensioner arm, and the dynamic tension of the belt span are calculated and compared well with the experimental data, which validate the presented unified formulas and the developed general purpose software. The modeling method and the procedure described in this paper are instructive for designing an accessory drive system. [ABSTRACT FROM AUTHOR]

Experimental and modeling techniques for belt longitudinal static stiffness, longitudinal dynamic stiffness and damping coefficient, bending stiffness, and friction coefficient between a pulley and a belt are presented. Two methods for measuring longitudinal dynamic stiffness and damping coefficient of a belt are used, and the experimental results are compared. Experimen tal results show that the longitudinal dynamic stiffness of a belt is dependent on belt length, pretension, excitation amplitude and excitation frequency, and the damping coefficient of a belt is dependent on excitation frequency. Two models are presented to model the dependence of longitudinal dynamic stiffness and damping coefficient of a belt on belt length, pretension, excitation amplitude and excitation fre-quency. The proposed model is validated by comparing the estimated dynamic stiffness and damping with the experiment data. Also, the measurements of belt bending stiffness are carried out and the influences of the belt length on the belt bending stiffness are investigated. One test rig for measuring friction coefficient between a pulley and a belt are designed and fabricated, and the friction coefficient between the groove side belt with the groove side pulley, and the flat side belt with a flat pulley is measured with the test rig. The influences of wrap angle between pulley and belt, pretension of belt and rota-tional speed of the pulley on the friction coefficient are measured and analyzed. Taking an engine front end accessory drive system (FEAD) as the research example for the accessory drive system, experimental methods and the static and dynamic characteristics for the FEAD with seven pulleys, a tensioner, and a serpentine belt are presented. [ABSTRACT FROM AUTHOR]

Abstract: The thermal-diffusive model was applied to demonstrate possibility of formation of oscillating or rotating spatial flame structures, which were described previously in experimental works on premixed gas combustion in the clearance between two disks with radial feeding of premixture. The gas flow was assigned and described by the Poiseuille-flow velocity profile. Rotating and oscillating flame patterns in a radial channel were observed only within certain ranges of gas flow rates. Formation of these special flame structures is related to preheating of unburned mixture by hot walls and non-uniform velocity distribution inside the microchannel. [Copyright &y& Elsevier]

The demand of further increased bypass ratios for turbofan engines will lead to low pressure turbines with larger diameter and lower rotational speed in conventional highbypass aeroengine architectures. Due to that, it is necessary to guide the flow leaving the high pressure turbine to the low pressure turbine at a larger diameter without any severe loss generating separation or flow disturbances. To reduce costs and weight this turbine duct has to be as short as possible. This results in superaggressive (very high diffusion) S-shaped geometries where the boundary layers are not able to withstand the strong adverse pressure gradient, which results inflow separation. This paper describes the flow through a fully separated duct as a baseline configuratiOn. In a next step the influence of passive flow control devices onto this separation has been investigated. Therefore, lowprofile vortex generators were applied within the first bend of this S-shaped intermediate turbine diffuser in order to energize the boundary layer and further reduce or even suppress the occurring separation. This configuration was investigated downstream a transonic turbine stage. Measurements were performed by means of five-hole-probes, static wall pressure taps, and oil flow visualization at the duct endwalls. For a better understanding of the flow behavior the vortex generators were also investigated in a two-dimensional rectangular S-shaped duct using the same Mach number level. Results showed that the vortex generators reduce the separation in the 2D-duct but have no distinct influence on the separation within the turbine duct due to wakes as well as strong secondary flow effects. [ABSTRACT FROM AUTHOR]

Oxygen content in the pure Silicon crystal is inevitable because of the significant rate of corrosion of the crucible walls at high temperature. Precise control of oxygen is possible only by manipulating underlying flow. A global model was developed to investigate the effect of crystal and crucible rotations in absence and presence of the Electromagnetic Fields (EMs) on melt flow. The simulation results show that strong buoyancy driven flow interaction generates non-uniformity in oxygen concentration near the edge of the crystal in the absence of magnetic field. Application of external field facilitates more pumping of melt underneath the crystal that prevents stratification of oxygen near the edge. [ABSTRACT FROM AUTHOR]

The suitability of a Lattice Bhatnagar-Gross-Krook (LBGK) modelling approach is tested to examine the behaviour of free surface waves in shallow water. The free surface model is fully non-linear. Mathematically, this is taken into account through the collision integral. The present LBGK model discretises the non-linear shallow water equation in rotational flow and approximates the collision between particles using a single time relaxation. It is further assumed that the waves do not overturn. The test case includes a long-wave run-up study on a sloping beach. Two methods have been evaluated to treat the wet-dry interface: a thin film in dry areas of the beach slope; a linear extrapolation scheme. The standard LBGK solutions are second-order accurate in space and first-order accurate in time. The uniform grid solutions compared well with other findings reported in the literature when using a shoreline algorithm. [ABSTRACT FROM AUTHOR]