On the Near-field Aerodynamics of a Projectile Launched from a Ballistic Range
01 Jul 2007-Journal of Mechanical Science and Technology (Korean Society of Mechanical Engineers)-Vol. 21, Iss: 7, pp 1129-1138
TL;DR: In this paper, a moving coordinate scheme for a multi-domain technique was employed to investigate the unsteady flow with moving boundary, and the effect of virtual mass was added in the governing equations for each domain.
Abstract: A computational fluid dynamics method has been applied to simulate the unsteady aerodynamics of the projectile launched from a ballistic range. A moving coordinate scheme for a multi-domain technique was employed to investigate the unsteady flow with moving boundary. The coordinate system fixed to each moving domain was applied to the multi-domains, and the effect of virtual mass was added in the governing equations for each domain. The unsteady, axisymmetric Euler equation systems were numerically solved using the third order Chakravarthy-Osher total variation diminishing scheme, with MUSCL approach. The projectile mass and configuration effects on the unsteady aerodynamics were investigated based on the computational results. The present computations were validated with results of some other CFD works available. The computed results reasonably capture the major flow features, such as shock waves, blast waves, shear layers, vertical flows, etc. which are generated in launching a projectile up to a supersonic speed. The present computational method properly predicts the velocity, acceleration and drag histories of the projectile.
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TL;DR: In this paper, a model based on the division of the momentum flux signal into momentum packets (fuel parcels) sequentially injected, and the tracking of them along the spray is presented.
Abstract: Momentum flux is a very important parameter for predicting the mixing potential of injection processes. Important factors such as spray penetration, spray cone angle, and air entrainment depend largely on spray momentum. In this article, a model is obtained which is able to predict the spray tip penetration using as an input the spray momentum flux signal. The model is based on the division of the momentum flux signal into momentum packets (fuel parcels) sequentially injected, and the tracking of them along the spray. These packets follow a theoretical equation which relates the penetration with the ambient density, momentum, spray cone angle and time. In order to validate the method, measures of momentum flux (impingement force) and macroscopic spray visualization in high density conditions have been performed on several mono-orifice nozzles. High agreement has been obtained between spray penetration prediction from momentum flux measurements and real spray penetration from macroscopic visualization.
38 citations
TL;DR: In this paper, a simulation of the launch process with different muzzle brakes was performed in a nearly realistic situation, where the hybrid Roe type scheme was employed to solve the flow fields with strong blast waves, and structured dynamic mesh technique was used for describing projectile motion.
Abstract: Numerical investigations of the projectile launch process with different muzzle brakes have been performed in a nearly realistic situation. Both two- and three-dimensional unsteady Euler equations are used as the governing equations. The hybrid Roe type scheme is employed to solve the flow fields with strong blast waves, and structured dynamic mesh technique is used for describing projectile motion. Based on the numerical solutions, the flow structures of a bare muzzle, the three-way and multi-hole muzzle brakes have been described, respectively, which agree well with our previous experimental shadowgraphs. Moreover, the efficiency of the three-way muzzle brake is calculated, which is also comparable to the corresponding experimental value. Our results showed that the numerical simulation can be a useful and efficient way for the design of new muzzle brakes.
22 citations
Cites background from "On the Near-field Aerodynamics of a..."
...However, numerical investigations of the complex geometry of the projectile and the muzzle brake are still difficult, and it needs to predigest the computational model, such as ignoring the chemical reactions, two-phase flow and the projectile shape [1, 8, 9], as well as the moving of projectile [10, 11] etc....
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...These kinds of muzzle flows are usually characterized mainly by two blast waves originating by two jet flows, and their interactions with the projectile [1-3]....
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TL;DR: In this article, the sabot discard behavior after projectile ejection from the muzzle is investigated at Mach number 4.0 and angle of attack of 0°, and 3D compressible equations implemented with a dynamic unstructured tetrahedral mesh are numerically solved with a commercial computational fluid dynamics (CFD) code (FLUENT 12.0).
Abstract: The sabot discard process of an armor-piercing, fin-stabilized discarding sabot (APFSDS) is crucial for the flight stability of the projectile. In this paper, the sabot discard behavior after projectile ejection from the muzzle is investigated at Mach number 4.0 and angle of attack of 0°. 3D compressible equations implemented with a dynamic unstructured tetrahedral mesh are numerically solved with a commercial computational fluid dynamics (CFD) code (FLUENT 12.0). Six-degrees-of-freedom (6DOF) rigid-body motion equations is solved with the CFD results through a user-defined function to update the sabot trajectory at every time step. A combination of springbased smoothing and local re-meshing is employed to regenerate the meshes around the sabot and describe its movement at each time step. Computational results show three different separation processes during the sabot discard process. Furthermore, the aerodynamic forces of APFSDS are calculated, and the trajectories of the three sabots are illustrated through the numerical solution of 6DOF equations. The results of the present study agree well with typical experimental results and provide detailed parameters that are important for analyzing the stability of the projectile. The present computations confirm that the numerical solution of the governing equations of aerodynamics and 6DOF rigid-body equations are a feasible method to study the sabot discard processes of APFSDS.
22 citations
TL;DR: In this article, the authors used Artificial Neural Network (ANN) to model and predict the impact of submerged aquatic weeds existence on the hydraulic performance of a branched open channel system.
Abstract: The existence of hydraulic structures in a branched open channel system urges the need for considering the gradually varied flow criterion in evaluating the different hydraulic characteristics in this type of open channel system. Computations of hydraulic characteristics such as flow rates and water surface profiles in branched open channel system with hydraulic structures require tremendous numerical effort especially when the flow cannot be assumed uniform. In addition, the existence of submerged aquatic weeds in this branched open channel system adds to the complexity of the evaluation of the different hydraulic characteristics for this system. However, this existence of aquatic weeds can not be neglected since it is very common in Egyptian open channel systems. Artificial Neural Network (ANN) has been widely utilized in the past decade in civil engineering applications for the simulation and prediction of the different physical phenomena and has proven its capabilities in the different fields. The present study aims towards introducing the use of ANN technique to model and predict the impact of submerged aquatic weeds existence on the hydraulic performance of branched open channel system. Specifically the current paper investigates a branched open channel system that consists of main channel supplies water to two branch channels that are infested by submerged aquatic weeds and have water structures such as clear over fall weirs and sluice gates. The results of this study showed that ANN technique was capable, with small computational effort and high accuracy, of predicting the impact of different infestation percentage for submerged aquatic weeds on the hydraulic performance of branched open channel system with two different hydraulic structures.
11 citations
TL;DR: The implemented experimental high-speed BOS setup has demonstrated its ability to capture clearly the salient features of the precursor and the propellant gas flow fields and their interactions, confirming the BOS capability to visualize complex density flow fields.
Abstract: Several experimental and numerical studies on muzzle blast and flow fields have been performed. However, due to the extremely short duration and the spatiotemporal evolution of these flows, experimental quantitative techniques are limited. As a consequence, the number of validated numerical calculations is limited as well. On the other hand, despite the development of computer models that have succeeded in predicting the measured pressure and velocity, they show unrealistic temperatures and densities. Therefore, temperature and/or density measurements are required to validate these codes, thus the motivation of this research. The present paper focuses on the development of a density-sensitive and non-intrusive measurement technique and the implementation of a quantitative flow visualization method based on Background-Oriented Schlieren (BOS) combined with a high-speed camera. In BOS, the experimental setup of conventional Schlieren (mirrors, lenses, and knife-edge) is replaced by a background pattern and a single digital camera. The muzzle flow fields and the flow field around a 5.56-mm projectile in flight were successfully visualized. Indeed, the implemented experimental high-speed BOS setup has demonstrated its ability to capture clearly the salient features of the precursor and the propellant gas flow fields and their interactions. The captured structures such as vortex, barrel shock, Mach disk, and blast wave show a good agreement with that issued from a realized conventional Schlieren setup and the bibliography, confirming the BOS capability to visualize complex density flow fields.
9 citations
References
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01 Jan 1983
TL;DR: Computational tests in two dimensions indicate that the use of multiple overset grids can simplify the task of grid generation without an adverse effect on flow-field algorithms and computer code complexity.
Abstract: A mesh system composed of multiple overset body-conforming grids is described for adapting finite-difference procedures to complex aircraft configurations. In this so-called 'chimera mesh,' a major grid is generated about a main component of the configuration and overset minor grids are used to resolve all other features. Methods for connecting overset multiple grids and modifications of flow-simulation algorithms are discussed. Computational tests in two dimensions indicate that the use of multiple overset grids can simplify the task of grid generation without an adverse effect on flow-field algorithms and computer code complexity.
472 citations
01 Jan 1985
TL;DR: In this article, a new family of high accuracy Total Variation Diminishing (TVD) schemes has been developed, which are defined with a five-point grid bandwidth and described for scalar equations, systems, and arbitrary coordinates.
Abstract: A new family of high accuracy Total Variation Diminishing (TVD) schemes has been developed. Members of the family include the conventional second-order TVD upwind scheme, various other second-order accurate TVD schemes with lower truncation error, and even a third-order accurate TVD approximation. All the schemes are defined with a five-point grid bandwidth. In this paper, the new algorithms are described for scalar equations, systems, and arbitrary coordinates. Selected numerical results are provided to illustrate the new algorithms and their properties.
423 citations
TL;DR: In this article, a coordinate-free formulation of conservation laws is developed, which clearly distinguishes the role of physical vectors from that of algebraic vectors which characterize the system, and the analysis considers general types of equations: potential, Euler, and Navier-Stokes.
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324 citations
Book•
15 Jan 1965
TL;DR: High speed wind tunnel testing as mentioned in this paper, high-speed wind tunnel test, high speed wind tunnels testing, مرکز فناوری اطلاعات, اراع رسانی, ک-شاوρزی
Abstract: High-speed wind tunnel testing , High-speed wind tunnel testing , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
256 citations
"On the Near-field Aerodynamics of a..." refers background in this paper
...In such a case, the projectile aerodynamics may be different from the steady aerodynamics, in which, at high-Reynolds number, the aerodynamics drag is only a function of only Mach number if the projectile shape were given (Pope and Goin, 1963; Sun et al., 2005)....
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01 Jan 1985
TL;DR: A new family of high accuracy Total Variation Diminishing schemes has been developed, which include the conventional second-order TVD upwind scheme, various other second- order accurate TVD schemes with lower truncation error, and even a third-order accurateTVD approximation.
Abstract: A new family of high accuracy Total Variation Diminishing (TVD) schemes has been developed. Members of the family include the conventional second-order TVD upwind scheme, various other second-order accurate TVD schemes with lower truncation error, and even a third-order accurate TVD approximation. All the schemes are defined with a five-point grid bandwidth. In this paper, the new algorithms are described for scalar equations, systems, and arbitrary coordinates. Selected numerical results are provided to illustrate the new algorithms and their properties.
115 citations