Atmospheric turbulence model for direct fire ballistics

2020 ◽  
pp. 154851292090647
Author(s):  
Tomas Bober ◽  
Thomas Recchia
Keyword(s):  
System Analysis ◽  
Flow Direction ◽  
High Fidelity ◽  
Mean Flow ◽  
Spectral Functions ◽  
New Information ◽  
Modern System ◽  
Atmospheric Motion ◽  
The Given ◽  
Turbulence Parameters

Modern system accuracy studies require high fidelity representations of environmental phenomena in order to accurately predict the down range performance of a gun system. One component of the atmosphere that has not been studied in great detail within the ballistic domain is turbulence. The current portrayal of wind leveraged by system analysis efforts ignores this element of atmospheric motion completely and thus its effects on down range dispersion have not been quantified. As a first step in addressing this deficiency, this study develops a methodology for generating synthetic turbulent wind signals along the flight path of a projectile. This goal is accomplished by integrating the work of several authors, developing techniques to fill knowledge gaps, and tailoring the solution to the direct fire domain. The significant contributions of the presented effort include mean flow direction agnostic spectral functions, provisions to account for the non-homogeneity of turbulence parameters along a trajectory, and a higher fidelity signal generation method than was used in previous work. The new information is applied to a sample engagement scenario in order to demonstrate the realization of the given techniques within the small caliber direct fire domain.

Uncertainty Quantification of Turbulence Measurements in a Fully Pulsed Axisymmetric Subsonic Air Jet

2016 ◽  
Vol 2 (2) ◽  
Author(s):  
Hariyo P. S. Pratomo
Keyword(s):  
Random Process ◽  
Flow Direction ◽  
Accuracy Assessment ◽  
Time History ◽  
Accuracy Evaluation ◽  
Hot Wire ◽  
Mean Flow ◽  
Turbulence Measurement ◽  
Air Jet ◽  
The Given

This paper reports the statistical accuracy evaluation of the implementation of ensemble-averaged equation used for the measurement of turbulence quantities in a fully pulsed, axisymmetric-subsonic air jet issuing into the still surrounding air. A constant mass flow rate and frequency of pulsation were used to generate the intermittent free jet, which physically contained a period of no flow between pulses due to a mechanical excitation. Time-history records of the random process were gained from a single normal hot-wire probe by a digital sampling technique, where the probe was operated in a constant temperature mode and placed at a fixed location in the jet field with the probe stems parallel to the mean flow direction. Within the framework of amplitude-domain analysis, the accuracy assessment was performed to which the uncertainties of mean value and higher-order moments were evaluated from the given values of sampling parameters, where the estimate of integral-time scale of the random process was the basis for determining the given sampling parameters. The present results suggest appropriate values of number of samples, sampling frequency, and sampling time of the hot-wire anemometer (HWA) technique for a repeatable turbulence measurement in the unsteady jet within a high degree of accuracy.

scholarly journals Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake

2021 ◽  
Author(s):  
Alexander Vakhrushev ◽  
Abdellah Kharicha ◽  
Ebrahim Karimi-Sibaki ◽  
Menghuai Wu ◽  
Andreas Ludwig ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Applied Magnetic Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Experimental Studies ◽  
Submerged Entry Nozzle ◽  
Mean Flow ◽  
Slab Caster ◽  
The Mean

AbstractA numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The magnetic field models a ruler-type EMBr and is installed in the region of the ports of the submerged entry nozzle (SEN). The current article considers magnet field strengths up to 441 mT, corresponding to a Hartmann number of about 600, and takes the electrical conductivity of the solidified shell into account. The numerical model of the turbulent flow under the applied magnetic field is implemented using the open-source CFD package OpenFOAM®. Our numerical results reveal that a growing magnitude of the applied magnetic field may cause a reversal of the flow direction at the meniscus surface, which is related the formation of a “multiroll” flow pattern in the mold. This phenomenon can be explained as a classical magnetohydrodynamics (MHD) effect: (1) the closure of the induced electric current results not primarily in a braking Lorentz force inside the jet but in an acceleration in regions of previously weak velocities, which initiates the formation of an opposite vortex (OV) close to the mean jet; (2) this vortex develops in size at the expense of the main vortex until it reaches the meniscus surface, where it becomes clearly visible. We also show that an acceleration of the meniscus flow must be expected when the applied magnetic field is smaller than a critical value. This acceleration is due to the transfer of kinetic energy from smaller turbulent structures into the mean flow. A further increase in the EMBr intensity leads to the expected damping of the mean flow and, consequently, to a reduction in the size of the upper roll. These investigations show that the Lorentz force cannot be reduced to a simple damping effect; depending on the field strength, its action is found to be topologically complex.

Effects of Pin Shape and Array Orientation on Heat Transfer and Pressure Loss in Pin Fin Arrays

1984 ◽  
Vol 106 (1) ◽  
pp. 252-257 ◽  
Author(s):  
D. E. Metzger ◽  
C. S. Fan ◽  
S. W. Haley
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Pressure Loss ◽  
Flow Direction ◽  
Circular Cross Section ◽  
Cycle Performance ◽  
Mean Flow ◽  
Pin Fin ◽  
The Mean ◽  
Cooling Air

Modern high-performance gas turbine engines operate at high turbine inlet temperatures and require internal convection cooling of many of the components exposed to the hot gas flow. Cooling air is supplied from the engine compressor at a cost to cycle performance and a design goal is to provide necessary cooling with the minimum required cooling air flow. In conjunction with this objective, two families of pin fin array geometries which have potential for improving airfoil internal cooling performance were studied experimentally. One family utilizes pins of a circular cross section with various orientations of the array with respect to the mean flow direction. The second family utilizes pins with an oblong cross section with various pin orientations with respect to the mean flow direction. Both heat transfer and pressure loss characteristics are presented. The results indicate that the use of circular pins with array orientation between staggered and inline can in some cases increase heat transfer while decreasing pressure loss. The use of elongated pins increases heat transfer, but at a high cost of increased pressure loss. In conjunction with the present measurements, previously published results were reexamined in order to estimate the magnitude of heat transfer coefficients on the pin surfaces relative to those of the endwall surfaces. The estimate indicates that the pin surface coefficients are approximately double the endwall values.

Linguistic influences on gesture’s form

Gesture ◽  
2005 ◽  
Vol 4 (2) ◽  
pp. 157-195 ◽  
Author(s):  
Jennifer Gerwing ◽  
Janet Bavelas
Keyword(s):  
Common Ground ◽  
Symbolic Form ◽  
Communicative Function ◽  
Face To Face ◽  
Original Action ◽  
New Information ◽  
Physical Form ◽  
The Common ◽  
The Given ◽  
Linguistic Influences

Hand gestures in face-to-face dialogue are symbolic acts, integrated with speech. Little is known about the factors that determine the physical form of these gestures. When the gesture depicts a previous nonsymbolic action, it obviously resembles this action; however, such gestures are not only noticeably different from the original action but, when they occur in a series, are different from each other. This paper presents an experiment with two separate analyses (one quantitative, one qualitative) testing the hypothesis that the immediate communicative function is a determinant of the symbolic form of the gesture. First, we manipulated whether the speaker was describing the previous action to an addressee who had done the same actions and therefore shared common ground or to one who had done different actions and therefore did not share common ground. The common ground gestures were judged to be significantly less complex, precise, or informative than the latter, a finding similar to the effects of common ground on words. In the qualitative analysis, we used the given versus new principle to analyze a series of gestures about the same actions by the same speaker. The speaker emphasized the new information in each gesture by making it larger, clearer, etc. When this information became given, a gesture for the same action became smaller or less precise, which is similar to findings for given versus new information in words. Thus the immediate communicative function (e.g., to convey information that is common ground or that is new) played a major role in determining the physical form of the gestures.

High-Fidelity Simulations of a High-Pressure Turbine Stage: Effects of Reynolds Number and Inlet Turbulence

2021 ◽  
Author(s):  
Yaomin Zhao ◽  
Richard D. Sandberg
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Suction Side ◽  
Rotor Blades ◽  
High Fidelity ◽  
Mean Flow ◽  
High Pressure Turbine ◽  
Flow Shear ◽  
Phase Lock ◽  
The Mean

Abstract We present the first wall-resolved high-fidelity simulations of high-pressure turbine (HPT) stages at engine-relevant conditions. A series of cases have been performed to investigate the effects of varying Reynolds numbers and inlet turbulence on the aerothermal behavior of the stage. While all of the cases have similar mean pressure distribution, the cases with higher Reynolds number show larger amplitude wall shear stress and enhanced heat fluxes around the vane and rotor blades. Moreover, higher-amplitude turbulence fluctuations at the inlet enhance heat transfer on the pressure-side and induce early transition on the suction-side of the vane, although the rotor blade boundary layers are not significantly affected. In addition to the time-averaged results, phase-lock averaged statistics are also collected to characterize the evolution of the stator wakes in the rotor passages. It is shown that the stretching and deformation of the stator wakes is dominated by the mean flow shear, and their interactions with the rotor blades can significantly intensify the heat transfer on the suction side. For the first time, the recently proposed entropy analysis has been applied to phase-lock averaged flow fields, which enables a quantitative characterization of the different mechanisms responsible for the unsteady losses of the stages. The results indicate that the losses related to the evolution of the stator wakes is mainly caused by the turbulence production, i.e. the direct interaction between the wake fluctuations and the mean flow shear through the rotor passages.

Doppler Profiler and Radar Observations of Boundary Layer Variability during the Landfall of Tropical Storm Gabrielle

2006 ◽  
Vol 63 (1) ◽  
pp. 234-251 ◽  
Author(s):  
Kevin R. Knupp ◽  
Justin Walters ◽  
Michael Biggerstaff
Keyword(s):  
Boundary Layer ◽  
Doppler Radar ◽  
Layer Structure ◽  
Flow Direction ◽  
Surface Flow ◽  
Tropical Storm ◽  
Mean Flow ◽  
Boundary Layer Structure ◽  
Stratiform Precipitation ◽  
Wind Profiles

Abstract Detailed observations of boundary layer structure were acquired on 14 September 2001, prior to and during the landfall of Tropical Storm Gabrielle. The Mobile Integrated Profiling System (MIPS) and the Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) were collocated at the western Florida coastline near Venice, very close to the wind center at landfall. Prior to landfall, the boundary layer was rendered weakly stable by a long period of evaporational cooling and mesoscale downdrafts within extensive stratiform precipitation that started 18 h before landfall. The cool air mass was expansive, with an area within the 23°C surface isotherm of about 50 000 km2. East-northeasterly surface flow transported this cool air off the west coast of Florida, toward the convergent warm core of the Gabrielle, and promoted the development of shallow warm and cold fronts that were prominent during the landfall phase. Airflow properties of the boundary layer around the coastal zone are examined using the MIPS and SMART-R data. Wind profiles exhibited considerable temporal variability throughout the period of observations. The stable offshore flow within stratiform precipitation exhibited a modest jet that descended from about 600 to 300 m within the 20-km zone centered on the coastline. In contrast, the onshore flow on the western side of the wind center produced a more turbulent boundary layer that exhibited a well-defined top varying between 400 and 1000 m MSL. The horizontal variability of each boundary layer is examined using high-resolution Doppler radar scans at locations up to 15 km on either side of the coastline, along the mean flow direction of the boundary layer. These analyses reveal that transitions in boundary layer structure for both the stable and unstable regimes were most substantial within 5 km of the coastline.

scholarly journals Discourse Intonation and Information Structure: An Empirical Study of Existential There Constructions in Non-native Spontaneous Speech

2016 ◽  
Vol 8 (2) ◽  
pp. 139-153
Author(s):  
Judit Nagy
Keyword(s):  
Language Learners ◽  
Information Structure ◽  
Sentence Type ◽  
Spontaneous Speech ◽  
New Information ◽  
Different Types ◽  
Discourse Intonation ◽  
Problematic Area ◽  
Accented English ◽  
The Given

Abstract The management of given and new information is one of the key components of accomplishing coherence in oral discourse, which is claimed to be a problematic area for language learners (Celce-Murcia, Dörnyei, and Thurrell 1995: 14). Research on discourse intonation proposes that instead of the given/new dichotomy, givenness should be viewed as a continuum, with different types of accessibility (Baumann & Grice 2006). Moreover, Prince (1992) previously categorized information structure into Hearer-old/Hearer-new and Discourse-old/Discourse-new information. There is consensus on the fact that focus or prominence associated with new information is marked with nuclear pitch accent, and its main acoustic cue, fundamental frequency (f0) (Ward & Birner 2001: 120). Non-native intonation has been reported to display numerous differences in f0 range and patterns compared to native speech (Wennerstrom 1994; Baker 2010). This study is an attempt to address the issue of marking information structure in existential there sentences by means of f0 in non-native spontaneous speech. Data originates from task-based interactions in the Wildcat Corpus of Native- and Foreign-Accented English (Van Engen et al. 2010). This paper examines two issues: (1) information structure in relation to the notions of givenness and different types of accessibility (Baumann & Grice 2006) and to Prince’s (1992) multidimensional taxonomy and (2) the use of f0 peaks to mark the prominence of new information. Several differences were measured among native speakers regarding the use of f0, sentence type, and complexity.

Measurement of the Mean Flow Field in a Smooth Rotating Channel With Coriolis and Buoyancy Effects

2017 ◽  
Author(s):  
Ruquan You ◽  
Haiwang Li ◽  
Zhi Tao ◽  
Kuan Wei
Keyword(s):  
Flow Field ◽  
Coriolis Force ◽  
Indium Tin Oxide ◽  
Buoyancy Force ◽  
Flow Direction ◽  
Density Ratio ◽  
Mean Flow ◽  
The Mean ◽  
Static Conditions ◽  
Rotating Channel

The mean flow field in a smooth rotating channel was measured by particle image velocimetry under the effect of buoyancy force. In the experiments, the Reynolds number, based on the channel hydraulic diameter (D) and the bulk mean velocity (Um), is 10000, and the rotation numbers are 0, 0.13, 0.26, 0.39, 0.52, respectively. The four channel walls are heated with Indium Tin Oxide (ITO) heater glass, making the density ratio (d.r.) about 0.1 and the maximum value of buoyancy number up to 0.27. The mean flow field was simulated on a 3D reconstruction at the position of 3.5<X/D<6.5, where X is along the mean flow direction. The effect of Coriolis force and buoyancy force on the mean flow was taken into consideration in the current work. The results show that the Coriolis force pushes the mean flow to the trailing side, making the asymmetry of the mean flow with that in the static conditions. On the leading surface, due to the effect of buoyancy force, the mean flow field changes considerably. Comparing with the case without buoyancy force, separated flow was captured by PIV on the leading side in the case with buoyancy force. More details of the flow field will be presented in this work.

scholarly journals Vulnerability analysis and method of selection of communication protocols for information transfer in Internet of Things systems

2021 ◽  
pp. 133-149
Author(s):  
Maryna Kolisnyk
Keyword(s):  
Internet Of Things ◽  
Initial Data ◽  
Information Transfer ◽  
System Analysis ◽  
Communication Protocols ◽  
Critical Systems ◽  
Smart Objects ◽  
Corporate System ◽  
The Given ◽  
Selection Of

The subject of study in the paper is the analysis of technologies, architectures, vulnerabilities and cyberattacks, communication patterns of smart objects, messaging models, and Internet of Things (IoT) / Web of Things (WoT) protocols for solving applied problems of critical and non-critical systems. The goal is to develop a method for selecting messaging models and application-level protocols in non-critical and critical multi-level IoT/WoT systems, provided that the type of access to intelligent objects is initially determined by the initial data, as well as analysis of vulnerabilities and attacks using these protocols. Objectives: to formalize the procedure for choosing communication protocols for IoT/WoT systems; analyze possible vulnerabilities of communication protocols; develop a method for selecting communication protocols for given initial data, depending on the selected type of communication template for smart objects; check practically the proposed method. The methods of research are methods of system analysis. The following results were obtained. The analysis of the features of communication protocols is conducted by comparing the main interrelated characteristics of IoT/WoT, the results of which are presented in the form of a table. A method has been developed for selecting communication protocols, depending on the selected type of communication template. The analysis of possible vulnerabilities of communication protocols and possible attacks using these protocols is conducted. The author has tested the method using the example of a corporate system (Smart House) based on the WoT concept. Findings. The scientific novelty of the results obtained is as follows: the analysis conducted in the paper shows that currently there is no unified approach to the choice of a messaging model and application-level protocols for building IoT/WoT, depending on the selected type of communication template for smart objects. The method for selecting communication protocols for the given conditions (for each IoT system its interaction pattern will correspond, depending on which components interact with each other), improved by the authors of the paper, makes it possible to simplify the task of using separate protocols for given IoT systems, considering vulnerabilities of protocols.

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