scholarly journals Comparative modelling of the destruction of a soft armour barrier using two- and threedimensional textile materials based on orthogonal fabrics

2021 ◽  
Vol 54 (4) ◽  
pp. 37-42
Author(s):  
Alexander P. Grechukhin ◽  
Amirhamza T. Khabibulloev ◽  
Begidzhon E. Begnazarov ◽  
Maksim D. Rudkovskiy
Keyword(s):  
Kinetic Energy ◽  
Surface Density ◽  
High Speed ◽  
Linear Density ◽  
Lesion Area ◽  
Virtual Testing ◽  
Textile Materials ◽  
Comparative Modelling ◽  
Number Of Layers ◽  
Weave Fabric

The article suggests an approach to virtual testing of textile materials for high-speed penetration. The comparison of two materials developed using different technologies – 3D orthogonal fabric and a package of plain weave fabric is carried out. For this purpose, such parameters of fabrics are selected so that the surface density is identical, the number of layers is the same, the linear density of the threads would be the same. The material of the threads is aramid fibre. In general, according to the assessment along the warp and weft, the lesion area for 3D orthogonal tissue is higher by up to 30 %. At the same time, 31.7 % more kinetic energy of the bullet was extinguished.

A New Method of Torque Compensation for High Speed Indexing Cam Mechanism

1999 ◽  
Vol 121 (2) ◽  
pp. 319-323 ◽  
Author(s):  
Teng Guilan ◽  
Fu Haibo ◽  
Zhou Weiyi
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Output Shaft ◽  
New Method ◽  
Linkage Mechanism ◽  
Energy Fluctuation ◽  
Positioning Accuracy ◽  
Input Shaft ◽  
Cam Mechanism

Severe vibration and poor positioning accuracy may occur in an indexing cam mechanism operating at a high speed. Torque fluctuation of the input shaft and the resulting fluctuation of kinetic energy of the mechanism may be the major cause of the vibration. In this paper a method is proposed to minimize the fluctuation by using a so-called “speed-varying flywheel” that produces an opposite kinetic energy fluctuation that can counteract the effect of the energy fluctuation. The flywheel is installed on the output shaft of an additional cam-linkage mechanism. The parameter of the cam-linkage mechanism is optimized. An example is given to demonstrate the effectiveness of this method.

CFD Investigation of the Flow of Trailing Edge Cooling Slots

2018 ◽  
Author(s):  
Y. Jiang ◽  
N. Gurram ◽  
E. Romero ◽  
P. T. Ireland ◽  
L. di Mare
Keyword(s):  
Mach Number ◽  
Kinetic Energy ◽  
Flow Separation ◽  
Film Cooling ◽  
High Speed ◽  
Turbine Blades ◽  
Cross Flow ◽  
Turbulent Energy ◽  
Trailing Edge ◽  
Flow Interactions

Slot film cooling is a popular choice for trailing edge cooling in high pressure (HP) turbine blades because it can provide more uniform film coverage compared to discrete film cooling holes. The slot geometry consists of a cut back in the blade pressure side connected through rectangular openings to the internal coolant feed passage. The numerical simulation of this kind of film cooling flows is challenging due to the presence of flow interactions like step flow separation, coolant-mainstream mixing and heat transfer. The geometry under consideration is a cutback surface at the trailing edge of a constant cross-section aerofoil. The cutback surface is divided into three sections separated by narrow lands. The experiments are conducted in a high speed cascade in Oxford Osney Thermo-Fluids Laboratory at Reynolds and Mach number distributions representative of engine conditions. The capability of CFD methods to capture these flow phenomena is investigated in this paper. The isentropic Mach number and film effectiveness are compared between CFD and pressure sensitive paint (PSP) data. Compared to steady k–ω SST method, Scale Adaptive Simulation (SAS) can agree better with the measurement. Furthermore, the profiles of kinetic energy, production and shear stress obtained by the steady and SAS methods are compared to identify the main source of inaccuracy in RANS simulations. The SAS method is better to capture the unsteady coolant-hot gas mixing and vortex shedding at the slot lip. The cross flow is found to affect the film significantly as it triggers flow separation near the lands and reduces the effectiveness. The film is non-symmetric with respect to the half-span plane and different flow features are present in each slot. The effect of mass flow ratio (MFR) on flow pattern and coolant distribution is also studied. The profiles of velocity, kinetic energy and production of turbulent energy are compared among the slots in detail. The MFR not only affects the magnitude but also changes the sign of production.

scholarly journals Self-ignition characteristics of the high-speed ramjet kinetic energy projectile in the launch process

2019 ◽  
Vol 32 (4) ◽  
pp. 851-860 ◽  
Author(s):  
Changfei ZHUO ◽  
Haotian CHEN ◽  
Wenjin YAO ◽  
Xiaoming WANG
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Ignition Characteristics

Grid Requirements for Multiscale Resolution in Separated Unsteady High Speed Turbulent Flows

2006 ◽  
Author(s):  
D. Basu ◽  
A. Hamed ◽  
K. Das
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulent Flows ◽  
Sound Pressure Level ◽  
High Speed ◽  
Sound Pressure ◽  
Pressure Fluctuations ◽  
Pressure Level ◽  
Navier Stokes ◽  
Detached Eddy Simulation

This study deals with the computational grid requirements in multiscale simulations of separated turbulent flows at high Reynolds number. The two-equation k-ε based DES (Detached Eddy Simulation) model is implemented in a full 3-D Navier-Stokes solver and numerical results are presented for transonic flow solution over an open cavity. Results for the vorticity, pressure fluctuations, SPL (Sound Pressure level) spectra and for modeled and resolved TKE (Turbulent Kinetic Energy) are presented and compared with available experimental data and with LES results. The results indicate that grid resolution significantly influences the resolved scales and the peak amplitude of the unsteady sound pressure level (SPL) and turbulent kinetic energy spectra.

Turbulent flow normal to a triangular cylinder

1997 ◽  
Vol 331 ◽  
pp. 107-125 ◽  
Author(s):  
D. K. HEIST ◽  
F. C. GOULDIN
Keyword(s):  
Energy Balance ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
High Speed ◽  
Turbulent Transport ◽  
Low Frequency ◽  
Recirculation Region ◽  
Constant Density ◽  
Energy Balances

Laser Doppler Velocimetry (LDV) measurements are presented for a nominally two-dimensional constant-density flow over a surface-mounted triangular cylinder. The thickness of the boundary layer approaching the triangular cylinder is much less than the height of the triangle. Momentum and turbulent kinetic energy balances are presented and comparisons are made with other separated and reattaching flows. Also, time domain information is presented in the form of autocorrelations and spectra. From the energy balances, the importance of the pressure transport term at the high-speed edge of the shear layer is seen. Observations of the relationships between the shapes of the spectra and the details of the energy balance are made. For example, the slope of the velocity spectra varies from the free-stream value of −5/3 to a value of −1 in the middle of the recirculation region. Concurrent with this increase in slope is a decrease in the role of shear production in the turbulent kinetic energy balance and an increase in the role of advection and turbulent transport. From the two-component LDV measurements, a very low-frequency unsteadiness is shown to contribute energy preferentially to different components of the velocity fluctuations depending on the location in the flow.

scholarly journals Rates of Dissipation of Turbulent Kinetic Energy in a High Reynolds Number Tidal Channel

2016 ◽  
Vol 33 (4) ◽  
pp. 817-837 ◽  
Author(s):  
Justine M. McMillan ◽  
Alex E. Hay ◽  
Rolf G. Lueck ◽  
Fabian Wolk
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
High Speed ◽  
Flow Speed ◽  
Small Scale ◽  
Tidal Channel ◽  
Dissipation Rates ◽  
Channel Separation ◽  
Shear Probe

AbstractThe ability to estimate the rate of dissipation (ε) of turbulent kinetic energy at middepth in a high-speed tidal channel using broadband acoustic Doppler current profilers (ADCPs) is assessed by making comparisons to direct measurements of ε obtained using shear probes mounted on a streamlined underwater buoy. The investigation was carried out in Grand Passage, Nova Scotia, Canada, where the depth-averaged flow speed reached 2 m s−1 and the Reynolds number was 8 × 107. The speed bin–averaged dissipation rates estimated from the ADCP data agree with the shear probe data to within a factor of 2. Both the ADCP and the shear probe measurements indicate a linear dependence of ε on the cube of the flow speed during flood and much lower dissipation rates during ebb. The ebb–flood asymmetry and the small-scale intermittency in ε are also apparent in the lognormal distributions of the shear probe data. Possible sources of bias and error in the ε estimates are investigated, and the most likely causes of the discrepancy between the ADCP and shear probe estimates are the cross-channel separation of the instruments and the high degree of spatial variability that exists in the channel.

Further studies of kinetic energy methods in high speed ramjet cycleanalysis

1992 ◽  
Author(s):  
EDWARD CURRAN ◽  
JOHN LEINGANG ◽  
LOUIS CARREIRO ◽  
DEANP. PETTERS
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Energy Methods

Turbulent Flow Past a Surface-Mounted Two-Dimensional Rib

1994 ◽  
Vol 116 (2) ◽  
pp. 238-246 ◽  
Author(s):  
S. Acharya ◽  
S. Dutta ◽  
T. A. Myrum ◽  
R. S. Baker
Keyword(s):  
Kinetic Energy ◽  
Shear Layer ◽  
High Speed ◽  
Two Dimensional ◽  
Duct Flow ◽  
Core Flow ◽  
The Core ◽  
Separated Shear Layer ◽  
Flow Past ◽  
The Mean

The ability of the nonlinear k–ε turbulence model to predict the flow in a separated duct flow past a wall-mounted, two-dimensional rib was assessed through comparisons with the standard k–ε model and experimental results. Improved predictions of the streamwise turbulence intensity and the mean streamwise velocities near the high-speed edge of the separated shear layer and in the flow downstream of reattachment were obtained with the nonlinear model. More realistic predictions of the production and dissipation of the turbulent kinetic energy near reattachment were also obtained. Otherwise, the performance of the two models was comparable, with both models performing quite well in the core flow regions and close to reattachment and both models performing poorly in the separated and shear-layer regions close to the rib.

CRASHWORTHINESS EVALUATION OF THE KOREAN HIGH SPEED TRAIN USING A VIRTUAL TESTING MODEL

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1383-1390 ◽  
Author(s):  
SEUNG ROK KIM ◽  
TAE SOO KWON ◽  
JEONG SEO KOO
Keyword(s):  
High Speed ◽  
High Performance ◽  
Assessment Method ◽  
High Speed Train ◽  
Virtual Testing ◽  
Testing Model ◽  
Chain Reactions ◽  
Modeling Techniques ◽  
Accident Scenarios ◽  
High Performance Computers

In this paper, a virtual testing model (VTM) for the Korean high speed train (KHST) is developed to meet several design purposes, and an improved collision safety assessment method is also suggested. Although twisting, buckling, zigzagging, chain reactions, overriding and derailment have long been recognized as the important elements that can affect the safety of passengers in the event of a collision, the means by which such behaviors can be predicted have been restricted. To address this, a VTM, supported by the technological advancements of numerical analysis software and high-performance computers, was developed to simulate and evaluate such behaviors. The VTM for KHST was modeled using finite elements, in order to obtain such collision behaviors. In addition, the VTM was simulated in a variety of accident scenarios, and the results were analyzed and compared with the results obtained using other modeling techniques. Since factors such as the deformation of individual members, serial collisions and twisting of the train body were incorporated into the VTM, this simulation provides more practical collision responses than other modeling techniques. This shows that it can predict more nonlinear collision behaviors, giving it a wider range of applications.

scholarly journals DETERMINATION OF THE OPTIMAL PARAMETERS OF THE HEAT-SHIELDING PROPERTIES OF NATURAL AND SYNTHETIC FILLERS FOR CHILDREN'S OUTERWEAR PRODUCTION

2019 ◽  
pp. 170-180
Author(s):  
Iraida Dudla ◽  
◽  
Olena Khrebtan ◽  
Keyword(s):  
Heat Transfer ◽  
Surface Density ◽  
Optimal Parameters ◽  
Target Setting ◽  
Textile Materials ◽  
Mathematical Equations ◽  
Shielding Properties ◽  
Heat Shielding ◽  
Natural And Synthetic

Urgency of the research. The main functional property of children's outerwear is a heat-shielding property. The research of the heat-shielding properties of natural and synthetic fillers for children's outerwear production is quite multifaceted, complex and insufficiently studied question. This is due to the fact that for the manufacture of children's outerwear new fabrics for the top and lining, as well as fillers of various materials are used. Target setting. Determination of the optimal parameters of the heat-shielding properties of natural and synthetic fillers for children's outerwear production is an important task, since the greatest value of clothing is for the processes of heat exchange of the human body with the environment and to ensure normal thermoregulation. Actual scientific researches and issues analysis. Considerable attention has been paid to the prediction of the heatprotective properties of winter clothing or its construction, the substantiation of the choice of a package of materials for the manufacture of children's outerwear, mathematical modelling of the heat transfer through textile materials and to the physical model of thermal resistance determination. Uninvestigated parts of general matters defining. The heat-shielding properties of natural and synthetic fillers for the outerwear of children are practically not studied, and the calculations of the optimal parameters of these properties are fragmentary. The research objective. to determine the optimal parameters of the heat-shielding properties of natural and synthetic fillers for children's outerwear production. The statement of basic materials. It was found that the heat-shielding properties of children's jackets with feather-down and synthetic textile filler depend on the type of filler, thickness, surface density and breathability of the clothing package. Conclusions. Children's jackets with feather-down filler with a smaller thickness have the lowest level of breathability, which provides them with the best heat-shielding properties. The higher level of breathability inherent in a children's jacket with synthetic textile filler with a significantly greater thickness of the package can provide high levels of the heat-shielding properties. Mathematical equations to determine the optimal parameters of the heat-shielding properties of natural and synthetic fillers for children's outerwear production are suggested.

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