Rotational Speed Research Articles

A Novel Multi-compartment Rotating Bioreactor for Improving ADSC-Spheroid Formation and its Application in Neurogenic Erectile Dysfunction.

The aim of this study was to construct a multicompartment synchronous rotating bioreactor (MCSRB) for batch-production of homogenized adipose-derived stem cell (ADSC) microspheres and treat neurogenic erectile dysfunction (ED). Firstly, an MCSRB was constructed using a centrifugal device and hinged trays. Secondly, influence factors (density, rotational speed) on the formation of ADSC-spheroids were explored. Finally, a neurogenic ED model was established to verify the effectiveness and safety of ADSC-spheroids for ED treatment. An MCSRB promoted ADSCs to gather microspheres, most of which were 90-130 μm in diameter. Supernatant from three-dimensional culture led to a significant increase in cytokine expression in ADSCs and migration rate in human umbilical vein endothelial cells (HUVECs) compared to control groups. The erectile function and pathological changes of the penis were improved in the ADSC-spheroids treatment group compared to the traditional ADSCs treatment group (p < 0.01). Efficient, batch, controlled and homogenized production of ADSC stem cell microspheres, and effective improvement of erectile dysfunction in neurogenic rats can be achieved using the MCSRB device.

Design and optimization of stirrer and mixer design for the correct mixing of pharmaceutical powders through DEM

Mixing of granular materials is an important process for pharmaceutical industries. In this study, a quantifiable calculation method was suggested to determine the final mixing degree of the mixture. Based on that, the effect of the stirrer design, rotational speed, powder density, cohesivity, material ratios, and particle movement in the chamber guided through different designs of deflectors on the final mixing quality is examined. The results show that increasing the stirring speed, generates better mixing quality. However, introducing a varying rotational speed mode improves the mixing degree specially for binary mixtures with high relative densities. The improvement of the mixing with the number of contacting blades is observed. Finally, the introduction of a simple deflector drastically enhances the mixing quality and enables the feeding into the chamber, which is key for continuous operation with cohesive powders, making the process more stable and efficient by using more of the mixing volume.

DEM analysis of heat generation and transfer during granular flow in a rotating drum

In many granular material handling processes, heat generation, and subsequent temperature rise, due to contacts between particles and surfaces is common. Aiming to explore this phenomenon, friction-induced heat generation and heat transfer models are developed and implemented into a Discrete Element Method (DEM) in this paper. The DEM models are validated qualitatively for the temperature distribution pattern and quantitatively for the evolution of particle temperature rise using data obtained experimentally. Moreover, the temperature distribution of the drum end plates obtained in the simulations shows the same annulus pattern observed in experiments. It is also found that increasing the rotation speed of the drum leads to an increase in the annular heated region of drum and in the net heat that particles obtain. In addition, a higher rotation speed leads to higher absolute fluctuations and lower relative variability of particle temperature.

Tip clearance influence on the performance of high-speed micro-pumps

The fast-paced development of the aerospace and shipping industry is promoting the development of lightweight and high-speed transfer pumps. High-speed micro-pumps with semi-open impellers are highly sensitive to tip clearance (TC), which crucially influences the head and efficiency. This study proposes a new design for a high-speed micro-semi-open impeller centrifugal pump with a 19 000 rpm rotational speed and 30 m hydraulic head. The performance of the proposed centrifugal pump under different inlet corrosion allowances and different impeller TC ratios (0.05, 0.08, 0.11, and 0.14) is investigated through numerical simulations and experiments. The interaction process between the leakage and main flows in the tip gap is recorded with a high-speed camera and is numerically calculated. The stability of the internal flow field is optimal under smaller TCs. This study provides the optimal TC and guidance for designing high-speed micro-pumps.

Investigation of Cross‐Sectional Characteristics of Internal Meshing Screw Mixing Flow Field for Dough Paste

ABSTRACTThe internal meshing screw mixer, driven by extensional rheology, demonstrates excellent mixing efficiency for high‐viscosity materials while minimizing fiber damage. This study developed a computational model for the mixing process of high‐viscosity fluids based on the motion equations of the internal meshing screw. The model was validated through experiments involving the mixing of corn syrup, flour and water. The results reveal the flow field's cross‐sectional streamlines and confirm the presence of chaotic mixing states at the system interface through horseshoe mapping and the existence of hyperbolic points. By comparing the extensional and shear rates, as well as analyzing the distribution of mixing indices, this paper establishes that the primary mixing mechanism within the cross‐section is extensional force, highlighting the role of the internal meshing screw as a mixer dominated by extensional flow fields. We investigate the variations in fluid velocity, velocity uniformity index, extensional rate, shear rate, and mixing index over time under different conditions of eccentricity, rotor radius, and rotational speed. The findings indicate that while eccentricity has a limited impact on average velocity, it significantly enhances velocity disturbances and increases the ratio of extensional effects within the fluid domain. In contrast, rotor radius and speed lead to a linear increase in average velocity but have little effect on velocity disturbances and the extensional effects in the fluid domain. This study provides valuable insights into how various cross‐sectional parameters influence the flow field of the internal meshing screw mixing process, offering crucial support for its application in mixing high‐viscosity non‐Newtonian fluids within the food industry.

Effect of flow direction on circumferential velocity, radial velocity, and flow resistance characteristics of rotating gap structures

A rotating gap structure is a type of viscous flow resistance using two disks where the rotation of one disk drives the fluid within the gap, generating rotational inertia. This inertia, combined with viscous friction, determines the flow resistance characteristic curve (pressure drop vs flow rate, or Δp-Q curve). By adjusting the disk's rotational speed, the rotational inertia and the Δp-Q curve can be modified. This paper examines how the radial flow direction (positive and negative) affects the circumferential velocity, radial velocity, and the Δp-Q curve of the rotating gap structure through theoretical modeling and experiments. Results show that radial flow direction and rate influence the symmetric distribution of radial velocity and the linear distribution of circumferential velocity, altering the main components of the Δp-Q curve: the viscous flow resistance curve (Δpvis-Q) and the rotational inertia flow resistance curve (Δprot-Q). The study found that the slope of the Δpvis-Q curve is smaller for positive flow than for negative flow due to differences in radial velocity distribution. Additionally, the circumferential velocity is weakened in positive flow and enhanced in negative flow, resulting in a smaller slope of the Δprot-Q curve for positive flow. These factors cause the Δp-Q curve to deviate from linearity, with greater deviation at higher rotational speeds. Finally, experimental verification was conducted, and the measured Δp-Q curve closely matched the theoretical calculations.

Characterizing the contact force of a high-speed rotating fluid on brush wire

Abstract To study the effect of coolant fluid on rotor-brush wire contact in high-speed conductive slip rings, the rotor-brush wire contact model is simplified to two cylindrical vertical contacts. The theoretical formula of the force on the near-wall surface of the brush wire is derived by combining the distribution of the characteristics of the cylindrical rotating fluid domain. A three-dimensional model of high-speed rotor-brush wire fluid-solid coupling is created. The initial preload and coolant disturbance on the near-wall surface of the brush wire is considered to analyze the force characteristics of the brush wire. The force characteristics of the near-wall surface and the three-dimensional surface velocity cloud diagram of the fluid domain are obtained. The results show that the growth rate of the fluid domain force on the wall surface of the brush wire increases with the increase of rotational speed. A change of only 0.5 mm near the wall leads to a change of nearly 40% in the speed.

Effect of Induced Wheel and Impeller Inlet Diameter on the Hydrodynamic Performance of High-speed Centrifugal Pumps

The high-speed centrifugal pump plays a crucial role in fields such as aerospace and petrochemical industries, owing to its characteristics of elevated rotational speed and high head. During high-speed operation, the centrifugal pump is prone to cavitation, which alters the fluid flow state within the pump, leading to vibrations, noise, and a sudden decrease in pump head and efficiency. Simultaneously, the collapse of cavitation bubbles generates impact pressure that can damage the pump's internal flow components, significantly reducing its operational lifespan and causing severe consequences. Moreover, under constant-flow conditions, the absolute and relative velocities of the fluid at the impeller inlet are functions of the suction pipe diameter. Therefore, there exists an optimal value for the impeller inlet diameter to enhance the centrifugal pump's resistance to cavitation. Similarly, the different geometric and structural parameters of the inducer also influence the hydraulic performance of the centrifugal pump. The focus of this study is on the external characteristics and internal flow patterns of an optimized high-speed centrifugal pump. In this paper, the entire flow field of the model pump is numerically simulated using ANSYS CFX software. The performance and overall flow field state of the high-speed centrifugal pump under different impeller configurations and inlet diameters are explored. The influence of blade wrap angle and inlet diameter on the high-speed centrifugal pump is revealed, providing a theoretical basis for subsequent optimal design.

Traveling wave vibration characteristics of rotating FGM conical shell

Abstract Conical shell is common structural component in various rotating machinery. The study of traveling wave vibration performance of conical shell is of great significant for the design of rotating machinery. This paper addresses the traveling wave vibration performance of rotating functionally graded material (FGM) conical shells. Artificial springs, uniformly distributed, are employed to simulate the boundary constraints of rotating FGM conical shell. Accounting for the effects of Coriolis and centrifugal forces caused by rotation, the energy equation of rotating FGM conical shell is calculated, and then the dynamical model of the rotating FGM conical shell under elastic supported constraints is established using the Lagrange equation. The influence of key factors on traveling wave frequency and response characteristics of rotating FGM conical shell are investigated including rotational speed, half-cone angle and material components.

Experimental analysis of a hybrid thermochemical cycle driven by intermediate grade heat sources for energy storage and combined cold and work productions

This paper presents an experimental study of a hybrid thermochemical cycle for the simultaneous cogeneration of cold and mechanical power, and thermal storage based on medium temperature sources. This concept is based on the integration of an expander machine on the reactive gas flow between the evaporator and the reactor to allow mechanical work production. The paper shows the proof of concept of this hybridization by continuous mechanical production and cold during the whole production phase: 68.33 kJ mechanical energy and 15.18 MJ cold, stable pressure ratio at the expander (around 1.3) and stable rotational speed (around 400 rpm). The prototype conception and design are detailed. The integration of the expander creates a pressure difference between the evaporator and the reactor (contrary to a classical thermochemical cycle), and thus an experimental sensitivity study investigating the effect of the cold production temperature at the evaporator (which defines the inlet pressure of the expander) on the mechanical production of the prototype and its dynamics is done. This allowed to analyze the strong coupling between the reactor and the expander in different operating conditions, experimentally and from a theoretical point of view. Indeed, the identified limitations of these two main components, it is worth mentioning that this is the first hybrid thermochemical prototype with stable output productions. The prototype works properly by providing continuous mechanical production during the whole production phase under different cold temperatures and constant electrical load, in comparison with what was found in the literature.

CFD numerical simulation, verification with experimental results and internal flow analysis of bristle turbines

In industrial facilities, a considerable amount of waste heat is often generated. However, due to the high costs associated with traditional methods of recovery, which do not align with the economic interests of enterprises, this waste heat is frequently wasted. With technological advancements, the bristle turbine has been proposed as a solution capable of effectively managing waste gases and providing added value to enterprises. Its advantages lie in its simple structure, easy installation, low rotational speed, and high reliability, offering a new option for waste heat recovery and utilization. Despite its potential, no previous research has conducted a detailed simulation of the bristle turbine, particularly focusing on internal flow dynamics, energy loss mechanisms, drag forces, and entropy generation. This study is the first to explore these critical aspects, making a novel contribution to the field. The paper presents the computational fluid dynamics (CFD) simulation of a 20 kW bristle turbine. The numerical simulation results are in good agreement with experimental results. Subsequently, the isentropic efficiency of the turbine at different speeds is simulated, and the performance of the turbine under off-design conditions is analyzed. By investigating the energy loss mechanisms within the turbine, optimization designs are proposed.

Artificial Neural Network and Gaussian Approach to Predict Rotor-Airframe Acoustic Waveforms

An artificial neural network-based surrogate model and Gaussian process model were developed to predict the acoustic interaction for a fixed-pitch rotor in proximity to a downstream cylindrical airframe typical of small unmanned aerial system platforms. The models were trained to predict the acoustic waveform under representative hover conditions as a function of rotational speed, airframe proximity, and observer angle. Training data were acquired in an anechoic chamber on both isolated rotors and rotor–airframe configurations. The acoustic amplitude and phase of the revolution-averaged interaction were predicted, which required up to 25 harmonics to capture the impulse event caused by the blade’s approach and departure from the airframe. Prediction performance showed, on average, that the artificial neural network models could estimate the acoustic amplitude and phase over the relevant harmonics for unseen conditions with 86% and 75% accuracy, respectively. This enables a time-domain reconstruction of the waveform for the range of geometric and flow parameters tested. In contrast, the Gaussian process matched the amplitude but underpredicted the phase for unseen conditions at 86% and 45% accuracy, respectively.

Simulation of thermal-mechanical coupling in Al alloy/steel inertia friction welding

Inertia friction welding (IFW) is a complicated thermal-mechanical coupling process. In-depth understanding of the thermal-mechanical process can improve the joint quality. In this study, a three-dimensional (3D) thermal-mechanical coupling model was successfully established to simulate the evolution of temperature, energy density, stress, strain, and flow behavior of the IFW process between 2219-O Al alloy and 304 stainless steel. The developed model was validated by comparing it with the measured temperature and deformation. Results show a transforming distribution of interface temperature from a M-shape to a squished V-shape during the IFW process. The characterization is attributed to the transformation of the accumulated friction energy density at the interface from a M-shape to an approximate V-shape due to the combined effect of varying sliding velocity and contact pressure. The Mises stress at the region near the interface is high and low at the steel and Al alloy sides, respectively. A significant portion of the kinetic energy stored in the flywheel is dissipated in the form of plastic deformation energy and cannot be neglected. The tracer particles show that most Al alloy at the initial interface is extruded to form flash, while a small amount of Al alloy is sticky and remains at the interface center. Increasing friction pressure and initial rotation speed result in higher interface temperature, axial shortening distance, and proportion of plastic work in total energy input.

Linear and nonlinear dynamics of self-consistent collisionless tearing modes in toroidal gyrokinetic simulations

We investigate tearing modes (TM) driven by current density gradient in collisionless tokamak plasmas by using the electromagnetic gyrokinetic simulation code ORB5. We elucidate the TM width by simulations for flat profiles, as the absence of background diamagnetic flows implies a small rotation speed, while finite gradients are included to investigate the TM rotation. For flat profiles, the initial saturation width of nonlinearly driven magnetic islands is related to the TM linear growth rate; however, large islands in the initial saturation phase are prone to current density redistribution that reduces the island width in the following evolution. Island-induced E×B and diamagnetic sheared flows develop at the separatrix, able to destabilize the Kelvin–Helmholtz instability (KHI). The KHI turbulence enhances a strong quadrupole vortex flow that reinforces the island decay, resulting in a strong reduction of the island width in an eventual steady state. This process is enhanced by trapped electrons. For finite gradients profile, the TM usually rotates in the electron diamagnetic direction but can change direction when the ion temperature gradient dominates the other gradients. The reduced growth of the TM by diamagnetic effects results in a moderate island size, which remains almost unchanged after the initial saturation. At steady state, strong zonal flows are nonlinearly excited and dominate the island rotation, as expected from previous theoretical and numerical studies. When β is increased, the TM mode is suppressed and a mode with the same helicity but with twisting parity, coupled with the neighboring poloidal harmonics, is destabilized, similar to the kinetic ballooning mode.

Design and study of a novel rotary high-impact test device

Abstract Impact testing is an important means of evaluating an object’s ability to withstand impacts at specific peak accelerations. Currently, commonly used high-g impact testing devices, such as the Mach hammer and air cannon test devices, generally provide overloads ranging from 10, 000g to 30, 000 g, with a maximum of 50, 000 g. To meet the demand for high-overload impact collisions, this paper designs and studies a high-g long pulse width rotary impact test device with a detachable impact head. A finite element simulation model of the impact process was established by using finite element analysis software, and the dynamic response of the device was studied by changing the initial rotation speed and the target plate material. The results show that the overload of this rotary impact test device can reach more than 70, 000 g, and increasing the speed and hardness of the target plate material can improve the overload magnitude. This device and research method can provide theoretical support for high-overload impact testing.

Magneto-convection ?ow of Nano-encapsulated phase change material (NEPCM) confined within a trapezoidal porous enclosure

This research attempts to study the thermal activity of suspension consisting of water and NEPCM elements inside a cavity with a trapezoidal cross-section. In addition, the cavity center contains a cold circular object rotating at a constant speed. The cavity is thermally characterized by the following: the upper and lower walls are thermally insulated (adiabatic), while the two lateral walls have a high temperature. The purpose of this study is to find out how the suspension interferes with the transfer of heat from hot walls to the cold body through the intervention of some initial conditions, which are: The effects of rotating cylinder speed (Re = 1 -500), medium permeability (Da = 10-5 – 10-2) and the magnetic field strength (Ha= 0 -100). The study used a digital simulation by solving the differential equations related to fluid mechanics and heat transfer using the Galerkin finite element (GFEM) method.to understand the influences of studied parameters (Re, Da and Ha numbers), the contours of isotherms, heat capacity and pathlines are presented in terms of these parameters. The findings indicated that as the rotation speed of the obstacle increased, the forced convection became dominant, and the thermal transmission rate improved. The improvement of the thermal transfer rate was also observed for higher Da numbers. Increasing the strength of the magnetic field hiders the fluid motion and reduces the thermal activity. At the highest studied Re, increasing Da from 10-5 to 10-2 augmented the Nusselt number by 10 times, while augmenting Ha from 0 to 100 reduced the Nu by 46%.

DEM simulation of an impact crusher using the fast-cutting breakage model

The impact crusher that exploits impact rather than pressure to break down materials has been widely used in the mineral industry. To further improve its performance in material crushing, numerical simulation capable of providing a deeper insight into the complicated dynamics of feed materials than experimental study has emerged as a promising tool. However, the field of the accurate prediction of product quality and explicit simulation of breakage events inside an industrial-scale crusher remains underexplored on account of the absence of a robust breakage model and heavy computational cost. In this study, a numerical investigation of an industrial-scale crusher using the fast-cutting breakage model is conducted within the DEM (Discrete Element Method) framework. The accuracy of the breakage simulation is quantitatively validated by comparing the predicted results with the measurements from actual production. Furthermore, the influence of operating conditions including the rotation speed of the rotor and the feeding rate on the interested parameters, i.e., the power consumption of the equipment, the size distribution of the products, and the impact-induced wear is investigated comprehensively. The results illustrate that (i) the size of the product increases with the rotor speed until a critical value, after which a further increase in rotor speed will exert no significant influence on the size distribution; (ii) The feeding rate is not a critical operating condition that largely determines the fineness of the product and the efficiency of the equipment almost remain stable under a certain range of feeding rates; (iii) The wear of the devices concentrates on the rotor and the impact plates, and the distribution of the wear exhibits different characteristics in different parts, caused by the complex collision between the particles and the devices.

Generation of broadband airborne ultrasound using an Harmonic Acoustic Pneumatic Source

This paper presents a new type of airborne transducer for generating broadband ultrasound with a high Sound Pressure Level (SPL). The concept is based on the Harmonic Acoustic Pneumatic Source (HAPS) that uses pressurized air in conjunction with a flow chopper made up of a rotating cage with slots connected to a specific exhaust. The fundamental frequency depends on the number of slots and the rotation speed of the cage. An analytical model of the HAPS coupled with a numerical model of the exhaust is used to predict the radiated acoustic pressure and to estimate the influence of dimensional parameters on pressure level generated by the source. Experiments are conducted with two cages: one with one slot in order to generate pulses periodically and one with 122 slots to generate periodic sound. The level of sound pressure is measured as a function of distance (0.004 to 0.5 m), the cage rotation (up to 11 krpm) and directivity (0 to 90°). For the fundamental frequency at 22 kHz, the maximum SPL of 150 dB (632 Pa rms) is /measured at 0.004 m, and decreases to 122 dB (35 Pa rms) at 0.5 m. At 0.5 m, the second and third harmonics can generate a SPL equal or greater than 115 dB above 22 kHz and up to 66 kHz. Discrepancies between the experiments results and numerical model are observed in terms of SPL, directivity and in-axis pressure.

Study on ultrasonic-assisted lapping performance and material removal behavior of diamond/SiC composites

Diamond/SiC composites have emerged as a new generation of highly promising materials for semiconductor packaging due to their excellent thermal conductivity. However, the exceptionally hard diamond and SiC phases in the composites have made precision machining a substantial difficulty. This study specifically explores the utilization of ultrasonic-assisted lapping (UAL) to enhance the machining performance of diamond/SiC composites. The focus is on investigating the effects of UAL on the material removals, including the brittle-ductile transition of sample interfacial diamond at different ultrasonic conditions, as well as the surface morphology of diamond/SiC composites. The removal mechanism of diamond/SiC composites under different machining conditions and the transient impact action of the abrasive were systematically analyzed, taking into account the abrasive size, the mechanical effects of ultrasonic vibration, and the interplay of processing parameters. The experimental results reveal that UAL significantly changes the traditional removal mode of diamond/SiC composites. At a constant rotational speed, the diamond abrasive size in the lapping solution exerts the primary influence on the sample surface morphology, followed by the average power of ultrasonic. Compared to conventional lapping methods, UAL improves the removal rate by 10.3 %, 5.4 %, and 5.3 % for abrasive sizes of 8 μm, 4 μm, and 1 μm, respectively. Optimally, the best surface quality finish of diamond/SiC composites was achieved with a lapping solution containing 4 μm abrasive particles and an average ultrasonic vibrator power of 75 W. This study underscores the potential of UAL to enhance the efficiency and quality of diamond/SiC composite machining.

Friction Stir Welding of Laser-powder Bed Fusion Manufactured A20X

This study investigates butt friction stir welding of 4 mm thick A20X plates, which were produced using additive manufacturing through laser-powder bed fusion. The plates were joined at varying process parameters, including different welding and rotational speeds. Both the microstructure and the mechanical strength of the joints were examined, comparing joints in both as-printed and as-welded conditions.The joints welded at a welding speed of 100 mm/min and a rotational speed of 1500 rpm exhibited superior mechanical properties compared to those produced with other parameter settings. The results show that decreasing the rotational speed while increasing the welding speed leads to the formation of tunnel defects, compromising joint integrity and resulting in lower ultimate tensile strength. In contrast, the combination of 100 mm/min welding speed and 1500 rpm rotational speed produced defect-free joints, with an average ultimate tensile strength of 335 MPa and an elongation at fracture of 8.5%.