bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Consideration on the Aerodynamic Design of Blast Wave Simulator Using a Shock Tube System
Authors: Kushida Suguru , Asada Kengo , Fujii Kozo , Tatsukawa Tomoaki , Sakamoto Kazuyuki
Published: November 2019

Reduction methods of the jet flow associated with simulated blast waves by blast wave simulators are investigated by computational simulations. First, the cause of the jet flow is discussed. After that, the influence of the nozzle angle and the volume of the driver section on the jet flow are investigated. The obtained results show that the jet flow is caused by vortices which are generated at the edge of the nozzle and that the jet can be reduced by decreasing the driver section. Furthermore, the nozzle with the moderate angle reduces the jet flow near the nozzle exit and the nozzle with the widest angle reduces the jet flow far from the nozzle exit. These results indicate reducing the driver section and using the proper nozzle angle according to the distance from the nozzle exit are effective for reducing the jet flow.
Numerical Prediction and Experimental Study on the Waviness Mechanical Seal
Authors: Feng Xiaodong , Ma Yu , Huang Bin
Published: November 2019

According to the actual operating conditions of the reactor coolant pump (RCP), based on the fluid lubrication theory, considering the complexity of the micro-narrow gap flow and the effect of surface roughness of the sealing end face, a mechanical seal model with different base film thicknesses at inner radius for the fixed waviness end face was established. The k-ε turbulent model was applied to solve the Navier-Stokes equation. Under different pressures, the fluid film pressure, open force and leakage rate of the mechanical seal end face with different base film thicknesses were obtained. According to the waviness end face of the specified wave amplitude at outer radius, the mechanical seal was manufactured by the grinding method of extrusion deformation and experiment. Comparing the experimental results with the numerical calculation results, it shows that the experimental results are in good agreement with the numerical results. It illustrates that the designed mechanical seal meets the requirements in engineering applications. Under different pressures, the base film thickness of the actual operation is accurately predicted by comparing the experimental leakage rate with the calculated ones. The calculating results show that the leakage rate increases with the increasing of pressure and the base film thickness under the same pressure. The open force decreased with the increasing of the base film thickness under the same pressure. Compared with the ideal surface, the presence of surface roughness will significantly increase the leakage.
The Transient Characteristics Analysis of Pump During Rapid Valve Opening and Closing
Authors: Yang Shuai , Li Shiyang , Wu Dazhuan , Zhang Kai , Li Qiao , Xu Zhongtian
Published: November 2019

The dynamic characteristics of pump response to transient events were investigated by combining the Method of Characteristic (MOC) and Computational Fluid Dynamics (CFD) together. In a typical pump–pipeline–valve system, similar to the reactor system, the pump is treated as three-dimensional CFD model using Fluent code, whereas the rest is represented by one-dimensional components using MOC code. Meanwhile, a description of the coupling theory and procedure ensuring proper communication within the two codes is given. Then the pump transient characteristics caused by downstream valve closing and opening were analyzed and compared with the steady characteristic to study the effect of fluid inertia on the pump transient performance. It was found that the H-Q curve in transient operation evidently deviates from the steady-state value and shows two distinct patterns of deviation, and the cause of the deviation was further explained by the comparison of pump internal and external characteristics. All the results showed that MOC–CFD is an efficient and promising way for simulating the interaction between pump model and piping system.
3D Modeling of Unsteady Flow Characteristics in ALIP Pump
Authors: Zhao Ruijie , Miao Heng , Zhang Desheng , Huang Jun , Gao Xiongfa
Published: November 2019

Annular linear induction pump (ALIP) is an ideal type of pump applied as the nuclear coolant pump for the sodium-cooled faster reactor (SFR). However, the operation will suffer from serious unstable problems when the pump size is increased and run at certain working conditions. A 3d numerical model of an ALIP based on the Finite Element method is built in this work to study the flow instability in the pump channel. The results show that the model can accurately predict the pump head at different working flow rate and some common phenomena, such as double supply fluctuation (DSF) and low frequency fluctuation. The results under unstable condition show that the liquid sodium in pump channel will separate in term of the outer stator position. Reversed flow and vortices always occur in the channel between two outer stators because of the non-uniform magnetic field in the azimuthal direction. Meanwhile the unstable flow is first presented in the meridian plane near the outer duct surface. Finally, a wave-like swing of the flow is presented at the rear of the unstable flow region, resulting in low frequency fluctuation in pressure.
Large Eddy Simulation of a Submerged Vortex in a Simplified Computational Model
Authors: Yamade Yoshinobu , Kato Chisachi , Nagahara Takahide , Matsui Jun
Published: November 2019

The flow structures of a submerged vortex that appears in a model pump sump were numerically investigated by performing large eddy simulation (LES) of a model vortex in a simplified computational model with a sufficiently fine grid that could resolve the vortex core. The simplified model is designed to simulate the flow under the bellmouth in a model pump sump. The model pump sump is composed of a 2,500 mm-long water channel of rectangular cross section with a width of 300 mm, a water height of 150 mm and a vertical suction pipe with a diameter of 100 mm installed at its downstream end. Our previous large eddy simulations, which used approximately 2 billion grids and were applied to the model pump sump, have fully clarified the origin and formation mechanism of a submerged vortex. In these computations, however, the static pressure in the vortex core decreased only by as much as 4 kPa at a channel velocity of 0.37 m/s. The decrease in the static pressure was far smaller than the one for which one can expect initiation of cavitation in the vortex core. The static pressure drop was most likely to be underpredicted in our previous LES. Insufficient grid resolution was assumed to be one of the reasons for this underprediction. In the present study, LES with a sufficiently fine grid was applied to the simplified computational model that represents the stretch of a submerged vortex under a constant acceleration of the vertical velocity. Case studies for which the grid resolution was varied between 3.25 and 150 micrometres were performed while the size of the vortex core appeared in the simplified model was 500 micrometres. As a result, we confirmed the grid resolution finer than 15 micrometres is needed to resolve the vortex core with a diameter of 500 micrometres. Vertical and tangential velocities obtained by averaging those distributions of a submerged vortex that was computed in our previous LES were prescribed at the bottom wall of the computational domain as the inlet boundary conditions. In the present LES with the grid resolution finer than 15 micrometres, the static pressure decreased by more than 100 kPa. In addition, the parametric studies where the initial swirl numbers were changed have fully clarified the change in the dynamics of a submerged vortex. We found that a strong submerged vortex appears only at a relatively small range of the swirl-number from 1 to 3.
Experimental Investigation of Choked Flow Conditions for Bubbly Flow
Authors: Shepard Thomas , Garbaly Aleksey
Published: November 2019

In an effervescent atomizer, a bubbly two-phase mixture flows through a convergent section before exhausting from an exit orifice. It is commonly believed that one of the key effects of including bubbles is in the substantial decrease in the speed of sound experienced by the two-phase flow allowing for choked flow conditions at the exit. The existence of choked conditions would result in under-expanded bubbles that would further expand upon exiting the atomizer and provide additional forces to aid in the break-up of the bulk liquid into droplets. This study examines how the homogenous two-phase flow model of speed of sound, and thus critical conditions, compare with experiments in order to better understand the fundamental physics of effervescent atomization. In these experiments, an effervescent atomizer is connected to a vacuum chamber allowing for internal atomizer pressure, liquid flow rate and air flow rate to be monitored as the post-exit pressure is decreased. Experiments reveal that the flow remains subcritical well beyond conditions that the homogenous flow theory might predict being choked. High-speed imaging is used to capture internal atomizer bubble size.
Cavitation-Induced Interface Instability of Droplet Between Plates
Authors: Li Hongchen , Wang Jingzhu , Wang Yiwei
Published: November 2019

Interface instability of droplet and formation of the liquid jet caused by internal volume oscillation are directly related to liquid pumping and mixing of microfluidic devices. Complex morphology jet enables liquid shaping, which is advantageous for industrial applications and biomedical engineering. In this study, the interface instability of cylindrical droplet between plates is investigated. The problem is analyzed through numerical simulation and experimentation. In the experiment, a single-pulse laser is used to generate cavitation at the center of the cylindrical droplet between two polymethyl methacrylate plates, and the physical progress is captured by high-speed photography. A compressible two-phase solver in the open source code OpenFOAM is used to simulate the 3D progress of bubble pulsation and droplet jet in consideration of viscosity and surface tension. Numerical methods adopt large eddy simulation. Results show that the interface density gradient is not collinear with the pressure gradient due to the shock wave impact and the bubble pulsation, that is, the baroclinic effect is the main cause of the instability at the droplet interface. The mechanism of the radial jet formation in the first period of bubble pulsation is closely related to the interface instability. A pair of vortex rings is formed under the influence of instability, thereby causing a stacking phenomenon on the jet head and eventually being cut. Affecting factors of the instability of the droplet interface are discussed. A high instability intensity of the droplet interface can be caused by a large initial bubble energy and a small contact angle. The instability strength of the droplet interface and the mode of jet formation are very sensitive to the curvature of the initial droplet shape. Relevant results may provide a reference for further understanding of interface instability and related engineering applications.
The Effect of the Velocity Ratio on the Diffusion Inhibition of Coaxial Jet
Authors: Akagi Fujio , Etou Takumi , Fukuda Yuito , Yoshioka Ryoya , Ando Youichi , Yamaguchi Sumio
Published: November 2019

The mixing characteristics of a coaxial round jet having inner to outer diameter ratio di/do = 0.67 was investigated to establish the method for mass and energy transport with inhibiting its diffusion. In the present study, the effect of the velocity ratio on the streamwise length of the potential core of the central round jet, the streamwise velocity distribution, and the evolution of vortcies of a coaxial jet was evaluated by using Large Eddy Simulation and experimental flow visualization to clarify diffusion inhibition mechanism of a central jet. Three velocity ratios γ = 0.25, 0.5, and 0.75 were conducted under a single condition of the central jet Reynolds number of 2000. The results show that the potential core length of a central jet become the longest on condition of the velocity ratio of 0.5, and the length was 15 times of the inner nozzle diameter. This value is equivalent to 3.8 times in the case of a general round jet. In other velocity ratio, it was also confirmed that the potential core length of a central jet becomes short by enhancement of vortices generation in the shear layer of annular and central jet. It is concluded that the velocity gradient in the shear layer is the important parameter in determining the diffusion of a central jet.
Numerical Study of Heat Transfer in a Row of Cylinders by 2D Large Eddy Simulation
Authors: Thorstensen Andreas Stengaard , Krogh Andreas , Dueholm Bjørn Christian , Højte Sebastian Bækkel , Thomasen Signe Birkebæk , Jensen Anna Lyhne , Sørensen Henrik , Hærvig Jakob
Published: November 2019

Complex flow structures arise as fluids are forced to flow across cylinder rows at moderate Reynolds numbers. In this study a numerical heat transfer analysis of 12 cylinders in an inline configuration is performed using Large Eddy Simulation (LES). The LES is conducted to get a better understanding of changes in the time averaged Nusselt number, 〈Nu〉, and local time averaged Nusselt number, 〈Nuθ〉, for each cylinder in the cylinder row. The simulations are performed at Re = UD/v = 10,000 and Pr = 0.71 with isothermal cylinders and a constant and uniform inflow temperature.

The results show that the time averaged Nusselt number increases slightly between the first and second cylinder due to increased turbulent velocity fluctuations. Beyond the second cylinder, the time averaged Nusselt number decreases until it reaches a near constant value after the fifth cylinder. For all 12 cylinders the local time averaged Nusselt number around the surface is highest at the stagnation point. The first cylinder in the row has the same distribution as the reference simulation conducted for a single cylinder. From the second cylinder and onwards a larger part of the overall heat transfer is in the spanwise direction compared to the first- and reference cylinder.
Effect of Fineness Ratio of 0.5 - 2.0 on the Wake Structure Around a Circular Cylinder Measured Using Time-Resolved PIV
Authors: Yokota Sho , Ochiai Taku , Ambo Takumi , Ozawa Yuta , Nonomura Taku , Asai Keisuke
Published: November 2019

In this study, the wake structure around freestream-aligned cylinder is investigated and its aerodynamic characteristics are discussed. A magnetic suspension and balance system (MSBS) was used to support a model without interference from a mechanical support device. Seven models with the fineness ratio (length to diameter, L/D) of 0.5, 1.0, 1.25, 1.5, 1.75, 2.0, and 2.25 were used. Reynolds number based on the cylinder diameter were 3.2 × 104 and 6.3 × 104. The velocity field was obtained by particle image velocimetry (PIV) in the center plane of the cylinder. In the case of fineness ratio over 1.5, the reattachment of shear layer was observed from the mean velocity field. The characteristic fluctuation of velocity was confirmed in power spectral density of streamwise component and vertical component. The length of the recirculation region is different depending on fineness ratio. The characteristic frequencies of the velocity fluctuation which seems to be due to recirculation bubble pumping and large-scale structure are observed from power spectrum density.
Erosive Wear Behavior of Fiberglass Reinforced Plastic Composite and Polyethylene
Authors: Banazadeh-Neishabouri Nafiseh , Shirazi Siamack A.
Published: November 2019

Effects of particle velocity, impact angle and particle size and shape on erosive behavior of Fiberglass Reinforced Plastic (FRP) and Polyethylene were investigated. Experiments were carried out with two particle velocities (18 and 32 m/s) and different impact angles ranging from 15 to 90 degrees. Silica sands with sizes of 75, 150 and 300 μm was utilized as erodent to study effects of sand shape and size. Results revealed erosion data of FRP and Polyethylene are similar to ductile materials as they display maximum erosion ratio at 30 degrees impact angle. However, Polyethylene showed an interesting behavior at 75 and 90 degrees; sand particles were embedded into the specimen and mass gain of specimen has been observed. 3D scan of wear patterns of specimens was obtained by 3D profilometer in order to evaluate the erosion depth and wear pattern of the surface.
A Tomographic PIV Study and Comparison of Vortex Identification Methods on NACA 63-215 Hydrofoil Wake Structure
Authors: Ziazi Reza M. , Goudarzi Navid
Published: November 2019

The unsteady flow field in the vicinity of a NACA 63-215 hydrofoil in a closed-loop water channel at Reynolds number of Re ≈ 29103 is investigated experimentally. A Tomographic Particle Image Velocimetry (TomoPIV) is used to determine the velocity field in the near-wake region of the studied hydrofoil. The manufactured hydrofoil was mounted on the 3D traverse and installed vertically in the water tunnel test section. The TomoPIV measurement volume was performed in a voxel with the volume of 164 × 168 × 82 mm3 (X, Y, Z). Vortex identification techniques including Q-criterion and λci criterion, together with helicity of flow are evaluated in the wake of the hydrofoil. Vorticity and swirling strength are used to further understand the location and behavior of the dynamic pattern of the vortex shedding in the trailing edge of the hydrofoil. The vorticity magnitudes as they transport downstream is explored to dissipate their energy in the wake. The flow pattern reflects a turbulent behavior required for higher efficiency of the designed hydrofoil. The results are compared with literature. This work obtains a validated model for the wind farm case and will be a basis of the ocean current turbine arrays wake structure analysis.
In-Line Testing of Novel Filter Media for Oil-Water Mixtures
Authors: Mule Anisha , Dabirian Ramin , Kolla Srinivas Swaroop , Mohan Ram , Shoham Ovadia
Published: November 2019

A novel non-fibrous filter media is evaluated for in-line oil-water separation. Outside-in-crossflow configuration incorporating the filter media is utilized in order to test the filter. All experiments are conducted with a hydrophilic-olephobic filter for water-continuous flow with low oil concentrations.

The collected experimental data include permeate flow rate and purity as well as pressure drop. Values of permeate flow rate and pressure drop are averaged over the duration of the experiments, which is about 5 minutes, constituting the “initial average” of the permeate flow rate and the corresponding pressure drop. Totally twelve experimental runs are conducted for mixture velocities of 0.038 m/s, 0.055 m/s and 0.066 m/s, and oil concentrations of 0.6%, 0.83%, 1.1%, 7.9% and 9.1%. Permeate samples are analyzed for oil content, demonstrating a high separation efficiency of 98 ± 2%.

The permeate flux across the filter cartridge ranges between 0.0739 (L/h)/cm2 to 0.216 (L/h)/cm2 owing to the low pressure drop across to filter. Oil concentration in to permeate water samples shows consistently increasing trend with an increase in inlet oil content, while maintaining high separation efficiency for all runs. The pressure drop across the membrane under flowing conditions ranges from 0.35 psid to 0.6 psid for flow rates between 0.1 L/min and 0.29 L/min, respectively. Also the data confirm that the filter membrane breakthrough pressure is 0.35 psid.
Reynolds Averaged Navier-Stokes Simulation of Highly Turbulent, Under-Expanded Jets and Effects of Impingement at Elevated Injection Pressure
Authors: Riglin Jacob , Wachtor Adam , Morgan Robert , Holguin Ryan , Bernardin John
Published: November 2019

Under-expanded jets have wide range of application from fuel injection to rocket propulsion. In the present work, a numerical model was generated to investigate the fluid mechanics behavior of under-expanded jet formation and wall interaction of a jet produced by exhausting a high pressure cylinder through a narrow tube into a low pressure cylinder. Axisymmectic, Reynolds Averaged Navier Stokes simulations were conducted employing the ANSYS FLUENT explicit, Coupled Pressure-Velocity solver to determine the stagnation pressure at the wall downstream of the orifice. Transient cases were conducted using timestep sizes of 1.0 × 10−8 s and 5.0 × 10−9 s. Various gases were investigated with Hydrogen being the primary working fluid with pressure ratios ranging from 10 to 100. This paper will focus primarily on the Hydrogen jets for pressure ratios of 10, 20, and 70. Numerical results were validated from both experimental results and higher fidelity Large Eddy Simulation results specifically analyzing the jet formation. Error between Mach disk height, Mach disk width, and Prandtl-Meyer expansion fan angles of the jet for pressure ratios of 10 and 70 were kept below 5%. The peak stagnation pressures at the center of the far wall for pressure ratios of 10, 20, and 70 were observed to be 86,843 Pa, 127,786 Pa, and 315,843 Pa, respectively. The predicted peak pressures show a linear relationship with respect to the initial pressure ratio existing between the high pressure and low pressure regions when the ratios are bounded between 10 and 70.
Evaluation of the Effect of Particle Size on Erosion Calculations Utilizing CFD and Comparison With Submerged Slurry Jet Experiments
Authors: Karimi Soroor , Zhang Jun , Shirazi Siamack A. , McLaury Brenton S.
Published: November 2019

The effects of particle size on erosion magnitude and erosion profiles are investigated experimentally in a submerged slurry jet impingement facility. The slurries were diluted to avoid concentration effects on the flow field and the resulting erosion. The experiments are performed with particle sizes of 25, 75, 150, 300, and 600 μm. Experimental results demonstrate different erosion severity and pattern for the various particle sizes. It is critical to have a reliable and accurate tool to predict erosion for different particle sizes. Previously, a comprehensive CFD-based procedure to predict erosion for various particle sizes was proposed by investigators at the Erosion/Corrosion Research Center (E/CRC). A feature of this procedure is that it can account for particle size in more detail than previous methods. In this study, the computational procedure is applied to conditions of the present experimental data. Particle impact parameters are extracted to explain the effect of particle size on the resulting erosion. The predicted results are compared with data which demonstrate possible shortcomings of the available CFD based techniques for predicting solid particle erosion. The results indicate that with proper use of grid spacing near the wall, the CFD-based erosion calculation method with existing erosion models can predict the trend of the experimental data, though improvements are still needed to the models to accurately account for particle size effects.
Numerical Simulation of Deposition Phenomena on High-Pressure Turbine Vane Using UPACS
Authors: Mizutori Kenta , Fukudome Koji , Yamamoto Makoto , Suzuki Masaya
Published: November 2019

We performed numerical simulation to understand deposition phenomena on high-pressure turbine vane. Several deposition models were compared and the OSU model showed good adaptation to any flow field and material, so it was implemented on UPACS. After the implementation, the simulations of deposition phenomenon in several cases of the flow field were conducted. From the results, particles adhere on the leading edge and the trailing edge side of the pressure surface. Also, the calculation of the total pressure loss coefficient was conducted after computing the flow field after deposition. The total pressure loss coefficient increased after deposition and it was revealed that the deposition deteriorates aerodynamic performance.
Analysis of a Centrifugal Pump Equipped With an Axial Rotor With Variable Speed
Authors: Bosioc Alin Ilie , Moş Daniel Călin , Muntean Sebastian , Anton Liviu Eugen
Published: November 2019

In the last two decades the energy market policy was focused on development of renewable energy. The renewable energy (solar and wind power) induces a fluctuating component of the electrical grid. The solution to compensate fluctuating energy is provided by the hydraulic turbines in order to produce energy in a short time and the pumps units in order to use the energy excess.

In order to ensure higher flow rate for the storage pumps, the units have constructive differences besides regular. Consequently, the complex shape of the suction-elbow with symmetrical geometry generates unsteady flows which are ingested by the impeller. These phenomena induce stronger unsteady flow conditions, such as stall, wakes, turbulence and pressure fluctuations, which affect the overall behavior of the pump providing vibration, noise and radial and axial forces on the rotor.

Alternatively, an axial rotor can be installed in front of the impeller. In this case, the flow non-uniformity will be decreased and the static pressure will be increased at the pump impeller inlet. Consequently, the efficiency behavior practically remains unchanged while the cavitational behavior is improved. Recently, a new concept was explored in order to assess the cavitational behavior on a wide range operation of the pump. The new concept proposes variable speed for the axial rotor, while the speed of the pump impeller remains constant. Accordingly, this new concept is experimentally and numerically investigated in the paper. First, the paper presents the 3D numerical investigation of the pump impeller combined with an axial rotor. The axial rotor is investigated at variable speed (between 2000 and 3000 rpm) while the pump impeller has constant speed of 2500 rpm. The minimum static pressure and the static pressure coefficient are analyzed in order to assess the new method. Second the mechanical design of the solution, for testing on the laboratory is presented. The solution contains an innovative clutch for controlling the variable speed of the axial rotor using magneto-rheological (MR) fluids. Thirdly, the experimental results concentrates on MR clutch operating regimes and the pump efficiency analysis. The MR clutch was installed between the driven electrical motor and the pump, three regimes were investigated: runaway speed for the axial rotor, clutch with MR fluid inside with and without magnetic field applied on it. The conclusions are drawn in the last section.
Fundamental Study on Injector Flow Characteristics of Self-Pressurizing Fluid for Small Rocket Engines
Authors: Yasuda Kazuki , Nakata Daisuke , Uchiumi Masaharu , Okada Kugo , Imai Ryoji
Published: November 2019

Nitrous oxide (N2O) is a suitable propellant for small rocket engines (mostly kN class), and has been widely used in various countries given its high saturated vapor pressure (i.e., 6 MPa at 300 K), which enables self-pressurization. Because nitrous oxide exists with gas-liquid equilibrium in tanks, cavitation occurs when the pressure in the tanks and feed lines drops slightly, which easily forms a gas-liquid two-phase flow. Since accurately estimating the performance of rocket engines requires ascertaining the characteristics of their propellant flows, flow tests with self-pressurization using nitrous oxide were conducted, as were firing tests of hybrid rocket engines using nitrous oxide as a liquid oxidizer and acrylic as a solid fuel. This paper presets the results of those tests, along with findings obtained regarding the characteristics of the gas-liquid two-phase injector flow with self-pressurization. In the N2O flow test, the injector upstream pressure was approximately 1.5 MPa, while the injector downstream pressure was approximately 0.1 MPa. At 0.070, the ratio of upstream to downstream pressure of the injector was thus extremely large, which suggested that the gas-liquid two-phase flow was choked with the injector. By contrast, in the firing test with a chamber pressure of approximately 1.0 MPa and a thrust of approximately 650 N, the ratio of the injector downstream pressure (i.e., chamber pressure) and its upstream pressure was approximately 0.56. Although that ratio was relatively large, because the injector upstream pressure is relatively low (i.e., approximately 1.8 MPa) and the backpressure fluctuated due to combustion, it remains unclear whether the gas-liquid two-phase flow was choked.
Inclusion of Heat Transfer on Settling Behavior of Elliptical Particles: Immersed Boundary-Thermal Lattice Boltzmann Method
Authors: Karimnejad Sajjad , Amiri Delouei Amin , Nazari Mohsen , Shahmardan Mohammad Mohsen , Ahmadi Goodarz , Mofakham Amir A.
Published: November 2019

In this study, the hybrid immersed boundary-thermal lattice Boltzmann method was developed and applied to assess the inclusion of heat transfer in flows containing non-circular particles. The direct forcing/heating immersed boundary method was used for determining the hydrodynamic forces and energy exchange. A complementary method was also implemented to treat non-circularity. The accuracy of the computational model and the employed complementary method were properly validated. Two cases for the falling ellipse were considered. A set of comprehensive simulations were performed and the effects of geometry, Grashof number, repulsive force, and heat transfer were analyzed. The findings of this study would be useful for a better understanding of settling non-circular particles in a thermal field.
Dynamic Performance Analysis of Large-Scale Packed Bed Truncated Conical Thermal Energy Storage
Authors: Singh Shobhana , Sørensen Kim
Published: November 2019

In the present paper, a high-temperature packed bed energy storage system of volume 175,000m3 is numerically investigated. The system is a underground packed bed of truncated conical shape, which comprises of rocks as a storage medium and air as a heat transfer fluid. A one-dimensional, two-phase model is developed to simulate the transient behavior of the storage. The developed model is used to conduct a parametric study with a wide range of design parameters to investigate the change in performance during both charging and discharging operation. Results show that the model satisfactorily predicts the dynamic behavior, and the truncated conical shaped storage with a rock diameter of 3cm, insulation thickness up to 0.6m and charging-discharging rate of 553kg/s leads to lower thermal losses and higher energy efficiencies. The paper provides useful insight into the transient performance and efficiency of a large-scale packed bed energy storage system within the range of parameters investigated.
Embedded RIOTS: Model Predictive Control Towards Edge
Authors: Viola Jairo , Dehghan Sina , Chen YangQuan
Published: November 2019

RIOTS is a general purpose optimal problem solver written as a MATLAB toolbox with mixed-language programming (C, Fortran, Matlab, Simulink). This first paper introduces how to make RIOTS run under an embedded platform RP3B (Raspberry Pi 3 B) with Windows 10. We presented the system architecture and a complete demo on running RIOTS as the inner kernel for MPC, using a house made thermal control system based on Peltier modules.
A SPICE Sub-Circuit Model for Backward Diode
Authors: Wu Wei , Wang Fengxia , Lozowski Andy G.
Published: November 2019

Backward diode and tunnel diode were formerly used in communication systems and now considered obsolete. Recently, because of their ultra-low threshold voltage at reverse bias condition, the backward diode is used as a rectifier diode for ultra-low power energy harvester. Unfortunately, there are few models available for SPICE simulation or any other computation analysis. The challenge of modeling backward diode and tunnel diode is their negative differential resistance (NDR) and result in a high probability of having numerical instabilities. This paper will first investigate several available mathematical models such as the polynomial model and Ray’s Empirical model, then, a less complex SPICE model based on discrete components sub-circuit will be proposed. All the unknown parameters of this proposed model are optimized based on measurement data using the Levenberg-Marquardt (LM) algorithm. This discrete SPICE model can be easily modified to model other elements with similar negative resistance behavior.
Novel Design of a 3T2R 5-DOF Parallel Manipulator
Authors: Yang Zhongxing , Zhang Dan
Published: November 2019

A novel 5-DOF 3T2R parallel manipulator is designed with chains in perpendicular planes. The synthesis is based on motion sets intersection and disseminated Chebychev-Grübler-Kutzbach formula. A boundary offset method is developed to detect link interference. Multi-objective optimization is practiced on the design for improved performances. Stiffness based on oriented platform coordinate is developed. This paper also discusses the potential applications of the design.
Design of a New Fully Compliant Translational Joint via Straight-Line Motion Mechanism Based Method
Authors: García Sonia C. , Gallego-Sanchez Juan A.
Published: November 2019

A Compliant Translational Joint (CTJ) is designed via Straight-Line Motion Mechanism Method. The designed CTJ is based on the Pseudo-Rigid-Body-Model (PRBM) of a modified Scott-Russell Mechanism. The precision of the straight-line motion of the rigid-body mechanism adjusts to a straight-line to a 99.6% while the compliant version adjusts to a 99.9%. The novelty of the design is given by the way the CTJ is designed, the performance of the CTJ is achieved by mirroring the mechanism about an axis tangent to the path of the mechanism and that passes through the initial position of the coupler point at the symmetry axis of the path. The CTJ motion is predicted by the PRBM. The force-displacement relations and the frequency modes of the CTJ are analyzed using finite element analysis (FEA).
Extended Camus Theory and Higher Order Conjugated Curves
Authors: Chan Cody Leeheng , Ting Kwun-Lon
Published: November 2019

According to Camus’ theorem, for a single DOF 3-body system with the three instant centers staying coincident, a point embedded on a body traces a pair of conjugated curves on the other two bodies. This paper discusses a fundamental issue not addressed in Camus’ theorem in the context of higher order curvature theory. Following the Aronhold-Kennedy theorem, in a single degree-of-freedom three-body system, the three instant centers must lie on a straight line. This paper proposes that if the line of the three instant centers is stationary (i.e. slide along itself), on the line of the instant centers a point embedded on a body traces a pair of conjugated curves on the other two bodies. Another case is that if the line of the three instant centers rotate about a stationary point, the stationary point embedded on the body also traces a pair of conjugated curves on the other two bodies. The paper demonstrates the use of instantaneous invariants to synthesize such a three-body system leading to a conjugate curve-pair generation. It is a supplement or extension of the Camus’ theorem. The Camus’ theorem may be regarded as a special singular case, in which all three instant centers are coincident.
Numerical Analysis of Quasi-Static Out-of-Plane Compression of Miura-Ori Patterned Sheets
Authors: Xiang Xinmei , Lu Guoxing
Published: November 2019

In this paper, quasi-static out-of-plane compression behaviors of Miura-ori patterned sheets were investigated numerically by using finite element analysis (FEA). The simulation results show a reasonable agreement with the experimental results. In addition, the parametric analysis of the Miura-ori patterned sheets with different cell wall thicknesses, side lengths, dihedral angles and sector angles were carried out using FEA method. The influences of different parameters on the peak force and mean force were determined.
Digital Twins for Space Factory 4.0
Authors: Weber Martins Thiago , Anderl Reiner
Published: November 2019

Aiming the rapid response of mega constellation of satellites to cover the increasing demand for Earth observation and communication, in-orbit manufacturing is a promising approach. Driven by the NewSpace, which is leading a paradigm change in the space industry, the project Space Factory 4.0 has been founded to establish new processes and technologies based on the Industrie 4.0 approaches for rapid satellite assembly on an in-orbit platform. One of its fundamental approaches and the main contribution of this paper is the Digital Twins. In the scope of a Space Factory 4.0, the Digital Twin is a holistic approach for supporting and controlling systems for in-orbit Assembly, Integration, and Test processes, as well as satellite operations, by establishing a bidirectional link to its physical counterpart. It is an essential approach to obtain a digital representation of the current state of the real product at any time, enabling the recognition of and reaction to disruptive parameters at an early stage. To model Digital Twins and to meet the specific requirements of a Space Factory 4.0, such as the capability of sending telecommands and processing telemetry data, an extension of Industrie 4.0 component, called Space Factory 4.0 component, is proposed. This paper discusses this concept, its implementation and the results obtained and concludes to discuss its benefits and potentials for the space industry.
On the Geometry of Stiffness and Compliance Under Concatenation
Authors: Kim Charles J.
Published: November 2019

Eigentwists and eigenwrenches capture the stationary stiffness behavior of compliant mechanisms and can be related to a mechanism’s primary kinematic behavior. The nature of concatenation of multiple mechanism building blocks is not well-understood. In this paper, we consider the mechanics of concatenation and develop design rules that capture the geometric nature of concatenation in terms of eigenwrenches and eigentwists. The rules are illustrated through mechanisms from the literature. The design rules have potential to provide intelligent guidance for systematic building block synthesis of compliant mechanisms.
A Novel Autonomous Scaled Electric Combat Vehicle
Authors: Tan Aaron Hao , Lang Haoxiang , El-Gindy Moustafa
Published: November 2019

Current literature pertaining to multi-steerable mobile platforms and the progression of military vehicles in the past few decades suggest a lack of effort in pursuing advanced technologies in this joint area. As a result, a novel 1:6 scaled electric combat vehicle prototype that features eight independently driven and steerable wheels is designed and developed in this paper. The intent is to create a scaled model for future autonomous vehicle navigation and control research in off road terrains. Starting with the mechanical design, this paper discusses the details of the chassis, suspension, driving and steering systems development. The electronics necessary for vehicle actuation is implemented with custom nodes and topics created for hardware communication within the Robot Operating System (ROS). Lastly, path planning and obstacle avoidance abilities are implemented to achieve autonomous navigation. The result of this work is a fully functional and instrumented robotic platform with a modular software architecture. Vehicle design analysis, performance and autonomous navigation abilities are experimentally tested with promising results.
A Transient Model of Inductrack Dynamic Systems
Authors: Wang Ruiyang , Yang Bingen
Published: November 2019

As a new approach to magnetic levitation by permanent magnet envisioned in 1990s, the concept of Inductrack has been applied to designs of various Maglev systems, including rocket launchers, Maglev trains, and the Hyperloop system as a conceptual future transportation tool. In such a system, the interaction forces between the source and induced magnetic fields are motion-coupled, and inevitably complicated with transient responses. Most previous investigations have mainly relied on the assumptions of ideal magnetic field, steady-state response and averaged magnetic force. Although these analyses provide some useful information for system design, due to limited understanding of the magnetic field-motion coupling and transient responses, they cannot predict the dynamic behaviors of an Inductrack system with fidelity and accuracy. Presented in this paper is a new transient model of Inductrack dynamic systems that is derived from fundamental physics laws, with the interactions of magnetic forces and motion in consideration. In the development, a state space representation of the transient model is established for numerical simulations. As verified in numerical examples, a benchmark 2-DOF transient model not only is able to reproduce the “steady-state” results reported in the literature, but also can exhibit the transient behaviors of Inductrack systems in longitudinal and vertical motion, which otherwise may not be possible by the existing models. The modeling approach presented in this paper is extendible to multi-degree-of-freedom (M-DOF) cases and it provides a foundation for stability analyses and feedback control of Inductrack systems.
A Literature Review: Solving Constrained Non-Linear Bi-Level Optimization Problems With Classical Methods
Authors: Biswas Arpan , Hoyle Christopher
Published: November 2019

Bi-level optimization is an emerging scope of research which consists of two optimization problems, where the lower-level optimization problem is nested into the upper-level problem as a constraint. Bi-level programming has gained much attention recently for practical applications. Bi-level Programming Problems (BLPP) can be solved with classical and heuristic optimization methods. However, applying heuristic methods, though easier to formulate for realistic complex design, are likely to be too computationally expensive for solving bi-level problems, especially when the problem has high function evaluation cost associated with handling large number of constraint functions. Thus, classical approaches are investigated in this paper. As we present, there appears to be no universally best classical method for solving any kind of NP-hard BLPP problem in terms of accuracy to finding true optimal solutions and minimal computational costs. This could cause a dilemma to the researcher in choosing an appropriate classical approach to solve a BLPP in different domains and levels of complexities. Therefore, this motivates us to provide a detailed literature review and a comparative study of the work done to date on applying different classical approaches in solving constrained non-linear, bi-level optimization problems considering continuous design variables and no discontinuity in functions.
Numerical Investigation on the Mixed Lubrication Performance of Water-Lubricated Coupled Journal and Thrust Bearings
Authors: Han Yanfeng , Xiang Guo , Wang Jiaxu
Published: November 2019

The mixed lubrication performance of water-lubricated coupled journal and thrust bearing (simplified as coupled bearing) is investigated by a developed numerical model. To ensure the continuity of hydrodynamic pressure and flow at the common boundary between the journal and thrust bearing, the conformal transformation is introduced to unify the solution domain of the Reynolds equation. In the presented study, the coupled effects between the journal and thrust bearing are discussed. The effects of the thrust bearing geometric film thickness on the mixed lubrication performance, including the load capacity, contact load and friction coefficient, of the journal bearing are investigated. And the effects of the journal bearing eccentricity ratio on the mixed lubrication performance of the thrust bearing are also investigated. The simulated results indicate the mutual effects between the journal and thrust bearing cannot be ignored in the coupled bearing system. The increasing thrust bearing geometric film thickness generates a decrease in load capacity of journal bearing. There exists an optimal eccentricity ratio of journal bearing that yields the minimum friction coefficient of the thrust bearing.
Fully Turbulent Vortex-Induced Vibration on a Cylinder Structure With a Nonlinear Energy Sink Absorber
Authors: Chen Dongyang , Xiao Qing , Ma Lei , Zhu Weijun , Abbas Laith K. , Rui Xiaoting
Published: November 2019

The fully turbulent vortex induced vibration (VIV) suppression of a circular cylinder through a nonlinear energy sink (NES) having linear damping and nonlinear cubic stiffness is investigated numerically. The computational fluid dynamics (CFD) method is carried out to calculate the fluid field, while a fourth-order Runge-Kutta method is used to calculating the nonlinear structure dynamics of flow-cylinder-NES coupled system. The fluid-structure interaction (FSI) model is validated against VIV experimental data for a cylinder in a uniform flow. The simulation results show that placing an NES structure with suitable parameters inside of the cylinder structure achieves a good VIV amplitudes’ suppression effect and narrows the “lock-in” region.
Regenerative Cutting Dynamics for a Periodically Forced Machine-Tool System
Authors: Xing Siyuan , Luo Albert C. J.
Published: November 2019

In this paper, a nonlinear, regenerative, orthogonal cutting system with a weak periodic oscillation of workpiece is considered. Period-1 motions in such a system are studied through a semi-analytical method, and the corresponding stability and bifurcations of the period-1 motions are analyzed via the eigenvalue analysis. The vibration of machine-tool varying with excitation is studied, and excitation effects on machine-tool chatters are discussed. Numerical simulations of unstable and stable period-1 motions are completed from analytical predictions. The machine-tool chatter can emerge from the saddle-node or Neimark bifurcation of period-1 motions.
Efficient Development of Continuum/Compliant Planar Linkage Mechanisms
Authors: Suh Woo Rib , McCarthy J. Michael , Peraza Hernandez Edwin A.
Published: November 2019

This paper presents a method to develop continuum/compliant mechanisms based on planar bar-node linkage precursors. The method takes as inputs the initial node positions and connectivity data of a given bar-node linkage and converts it into a continuum/compliant mechanism having the same targeted motion. The line bars of the given bar-node linkage are thickened into trapezoidal planar members and the nodes are thickened by introducing fillets at each intersection of bars. The thicknesses of the bars and the shape parameters of the fillets in the continuum/compliant linkage are optimized to obtain the same targeted motion of the given bar-node linkage while keeping stresses below a maximum allowable value. Each design generated during the optimization process is evaluated using finite element analysis. The present method allows for the synthesis of mechanisms having the following advantages over conventional bar-node linkages: 1) They do not require complex ball or pin joints; 2) they can be readily 3-D printed and size-scaled, and 3) they can be optimized to decrease stresses below a maximum allowable value. Furthermore, the method uses a relatively small number of optimization variables (thicknesses of the members, shape-parameters of the fillets), making it an efficient alternative to more complex and computationally intensive methods for synthesizing compliant mechanisms such as those incorporating topology optimization.